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INDUSTRY AND ENERGY DEPARTMENT WORKING PAPERENERGY SERIES PAPER No. 11
Technology Survey Report onElectric Power Systems
February 1989
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The World Bank Industry and Energy Department, PPR
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TECHNOLOGY SURVEY
ON
ELECTRIC POWER SYSTEMS
by
Lionel 0. BartholdPower Technologies, Inc.Schenectady, New York
FEBRUARY, 1989
Copyright (c) 1989The World Bank1818 H Street, N.W.Washington, DC 20433U.S.A.
This report is one of a series issued by the Industry and Energy Department for theinformation and guidance of Bank staff. The report may not be published or quotedas representing the views of the Bank Group, nor does the Bank Group acceptresponsibility for its accuracy or completeness.
Power Technologies, Inc.
ABSTRACT
This report presents an overview of the status of today's power system technology and expectations
for future development. The report examines all the main areas of the power system -- supply
and demand, generation, energy storage, transmission lines, transmission substations, system
operation, distribution, system design, software, and utility management. Throughout the world
shortage of investment funds is requiring utilities to give greater emphasis to operational
improvements to extend plant life, improve capacity factors and effect energy conservation.
Combined cycle units (gas turbines plus waste heat boiler and steam turbine) are emerging as the
preferred generating source because of their low capital cost and high efficiency, particularly
where gas is available. These units can also be adapted to coal fueling through coal gasification
to minimize using oil as a fuel and to utilize indigenous resources. Increased environmental
concern over conventional coal thermal emissions in many countries is giving impetus to the
development of fluidized bed and coal gasification technologies to permit wider use of coal for
electricity production. Unless economic hydro is available, diesels will continue as the
predominant supply source on small systems up to about 100 MW. Public concern, low oil prices
and high capital cost will limit the use of nuclear power to only a few developing countries. It
will be many years before new technologies such as fuel cells or ocean thermal energy conversion
could be considered for the developing countries. The limit of ac transmission voltages has
levelled off at about 800 kV because dc transmission is available for long distance transmission
and the maximum generating unit size has also levelled off. There is considerable scope for
improving utility productivity through computer automation in specific areas such as generation
dispatch, distribution operation and system control optimization.
Power Technologies, Inc.
TECHNOLOGY SURVEY REPORT
ON
ELECTRIC POWER SYSTEMS
PREFACE
The report was prepared by Power Technologies, Inc. (PTI) ofSchenectady, N.Y. and is therefore based largely on PTI'sexperience, insights and opinions. While the report includes"application-readiness" ranking as well as economic comparisonsfor each technology, generalizing on either subject is risky,particularly when one considers the power of technicalbreakthroughs. Where circumstances make a technologyparticularly interesting, it is better to have the applicationstudied by experts than to reject it based on an arbitraryranking system as used herein.
TABLE OF CONTENTS
Power Technologies, Inc.
TABLE OF CONTENTS
PAGEPREFACE
INTRODUCTION
POWER PRODUCTION & SUPPLY/DEMAND BALANCE . . . . . . . I-l
A. SUPPLY, DEMAND AND TECHNOLOGY DRIVING FORCES . . . 1-l
Conservation ........................ . 1-2Control ..... . . . . . . . . . . . . . . . . . . . . . . 1-6Dispersed Generation .... . . . . . . . . . . . . . . . . . 1-7Environmental Accommodation . . . . . . . . . . . . . . . . . 1-8Expert System Application . . . . . . . . . . . . . . . . . . . 1-9Fast-Valving .1....................... . 1-9Inspection and Maintenance Scheduling .1.. . . . . . . . . . . I-10Life Extension and Plant Betterment .1... . . . . . . . . . . I-10Load Management . . . . . . . . . . . . . . . . . . . . . . I-liPerformance Monitoring . . . . . . . . . . . . . . . . . . . . 1-13Repowering . . . . . . . . . . . . . . . . . . . . . . . . . 1-14Stabilizers . . . . . . . . . . . . . . . . . . . . . . . . . . I- 14Uprating . . . . . . . . . . . . . . . . . . . . . . . . . . I- 17
B. GENERATION TECHNOLOGY OPTIONS, STATUS AND DEVELOPMENT I- 18
Coal Desulphurization and Gasification .... . . . . . . . . . I- 18Combined Cycles . . . . . . . . . . . . . . . . . . . . . . . 1-18Integrated Gasification/Combined-Cycle Power Plants (IGCC). . I-18Pressurized Fluidized Bed Combined Cycle .1.. . . . . . . . . . 1-22Combustion Turbine Plants .1................. . 1-24Gas Turbines .1....................... . 1-24Combined Cycles .1... . . . . . . . . . . . . . . . . . . . 1-28Low Grade Gas Turbine Fuels .1... . . . . . . . . . . . . . 1-28Conventional Steam Power Plants .1... . . . . . . . . . . . . I-29Cycles & Steam Turbine/Generators .1... . . . . . . . . . . . I-30Other Equipment .1... . . . . . . . . . . . . . . . . . . . I-31Diesel Generation . . . . . . . . . . . . . . . . . . . . . . . 1-32Direct Converters . . . . . . . . . . . . . . . . . . . . . . . 1-34Magnetohydrodynamics (MHD) .1............... . I-34Thermionic Generators .1....... ... .. ... .. . . I-36Fluidized Bed Combustion ........ .. .. . . . . . . . 1-37Fuel Cells .1......................... 1-39Fusion, Breeders and Fast Reactors .1... . . . . . . . . . I-45Geothermal Plants .1.......... .... ... ... . 1-46Hydroelectric Plants .1.................... . 1-47
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TABLE OF CONTENTS (continued)
PAGE
Liquid Metal Topping Cycles . . . . . . . . . . . . . . . . . . 1-48Nuclear Power .1... . . . . . . . . . . . . . . . . . . . . 1-49Ocean Current . . . . . . . . . . . . . . . . . . . . . . . . 1-51Ocean Thermal Energy Conversion .-. 5.0. . . . . . . . . . . . I-S0Solar Thermal-Electric Power Plants .1............. . I-51Solar Voltaic ...... .. . . .. . . . . . . . . . . . . . I-52Stirling Engines .... . . . . . . . . . . . . . . . . . . . I-54Tidal Power ...... .. . . .. . . . . . . . . . . . . . 1-55Waste-Burning Plants . . . . . . . . . . . . . . . . . . . . . 1-57Wave Energy Conversion .1.... . . . . . . . . . . . . . . I-56Wind Power .1..... .. . .. . . .. . .. . . .. . . . I-57
II. ENERGY STORAGE . . . . . . . . . . . . . . . . . . . . . II-I
Battery Storage . . . . . . . . . . . . . . . . . . . . . . . . II- ICompressed Air (CAES) .1.1... . . . . . . . . . . . . . . . II-2Pumped Hydro .1.1.... . . .. . . . .. . . .. . . . . . 11-2Superconducting Magnetic Storage Energy System .1.1. . . . . . . II-3
III. TRANSMISSION LINES .1.1.1.-. . . . . . . . . . . . . . . .
Compaction . . . . . . . . . . . . . . . . . . . . . . . . .-Conductors .1.1.1...................... . III-3Cryogenic Transmission .1.1.1.. . . . . . . . . . . . . . . . III-4Electric Fields .1.1.1... . . .. . . . .. . . .. . . . . . III-5Fibre-Optics . . . . . . . . . . . . . . . . . . . . . . . . . III-5High Phase Order (HPO) .1.1.1................ . III-6High Voltage Direct Current (HVDC) .1.1.1. . . . . . . . . . . III-7Inspection and Maintenance .1.1.1. . . . . . . . . . . . . . . III-8Insulators .1.1.1.... . .. . .. . .. . .. .. . .. . . III-9Monitoring Systems ..... i . . . .. . . . . . . . . . . . III- I0Shield Wires for Supply of Local Load . . . . . . . . . . . . . . III- 11Towers and Optimization ..... . . . . . . . . . . . . . . III- 12Ultra High Voltage (UHV) .................. . II11-14Underground Cable . . . . . . . . . . . . . . . . . . . . . . III- 15Uprating Lines and Rights-of-Way .1.1.1. . . . . . . . . . . . 111-17
IV. TRANSMISSION SUBSTATIONS .... . . . . . . . . . . . IV-I
Bus Configuration ..... . . . . . .. . . . . . . . . . . IV- IBuswork .......................... . IV-2
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TABLE OF CONTENTS (continued)
PAGE
Capacitors ................... ...... . IV-2Gas-Insulated Substations (GIS) ................ . IV-4Grounding and Shielding ....... .. . .. .. . .. . . IV-5Instrument Transformers ................... . IV-5Protective Relays ........... ... ... .... . . IV-5Static Var Systems .......... .. ... ... .. . . IV-6Surge Arresters and BIL Specification ..... . . . . . . . . . IV-7Switchgear ......................... . IV-8Synchronous Condensers ........ .. .. .. . .. .. . IV-8Transformers and Reactors .................. . IV-8
V. SYSTEM OPERATION ........ .. .. .. .. . .. . V-1
Applications Software . . . . . . . . . . . . . . . . . . . . . V- 1Control Center Configuration ................. . V-3Control Software ........... ... ... .... . . V-4SCADA Systems ........... ... ... .... . . V-5Security ......................... . . V-6Training .......................... . V-6Wheeling of Power ......... .. .. .. ... .. . V-7
VI. DISTRIBUTION . . . . . . . . . . . . . . . . . . . . . . . VI- I
Distribution Automation . VI- IDistribution Voltage . VI- IMinimum Cost Rural Distribution. . VI-2Surge Protection . VI-2Switchgear and Switching . VI-3System Configuration. . VI-3Underground Cable . VI-5
VII. SYSTEM DESIGN . . . . . . . . . . . . . . . . . . . . . . VII- I
Dynamic Analysis .. VII-1Fault Analysis.. . VII-2Harmonics .. VII-2Load Flow.. . VII-3Maximizing Transfer Capability.. . VII-3Planning .. VII-4
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TABLE OF CONTENTS (continued)
PAGE
Production Simulation ............... .... .. . VII-6Subsynchronous Resonance .. VII-7Voltage Instability .... . . . . . ...... . . . . . . . VII-7
VIII. SOFTWARE . . . . . . . . . . . . . . . . . . . . . . . . . VIII- I
Artificial Intelligence . . . . . . . . . . . . . . . . . . . . . VIII- IData Bases .. VIII- IExpert Systems .. VIII-2Hardware Trends .. VIII-2"Product" Status of Software .. VIII-3Structure .. VIII-4
IX. MANAGEMENT & STRATEGIC TOPICS .XI-I
Corporate Modeling .. XI- IDeregulation . . . . . . . . . . . . . . . . . . . . . . . . . XI- IEnergy Modeling .. XI-2Least Cost Planning .. XI-3Maintenance Policies .. XI-3Prioritization and Structured Approaches to Complex Decisions . . . XI-4Privatization .. XI-SProductivity .. XI-6Strategic Planning .. XI-7
REFERENCES
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SECTION 0
INTRODUCTION
Power Technologies, Inc.
INTRODUCTION
This report is addressed to the engineer generally familiar with power industry
technologies, but not specialized in advanced technical fields. It is intended to
render as realistic and objective an assessment of technology as possible, avoiding
as best it can, the optimism bias that tends to color the reporting done by
researchers specific to a technology or by those with an interested position in a
technology's success. The report will serve as a technical update for engineers
generally familiar with power systems and it will cite, for key technologies and
major equipment categories:
o Current State-of-the-Art
o Research emphasis
o Application readiness
o Economic comparisons
The scope of the study did not provide for an extensive survey of the industry, so
the comments are largely derived from experience, consulting activities, and
software offered by the author's company. References are provided for those
interested in further background.
Each technology or product will be designated as one of the following "readiness'
categories:
A Successfully applied or clearly ready for economic application.
As Economically applicable in special circumstances only.
Ad Applicable following reasonably straightforward development orengineering effort.
P Suitable for experimental or demonstration prototype only
RD Suitable for research or development work
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C Concept only. Needs feasibility study before R&D commitment.
Developing countries often find advanced technologies difficult to apply due to a
weak technical support infrastructure and lack of local manufacturer support. Ir
the case of renewable power resources, for example, the power industry's (or moreaptly, its critics') enthusiasm has waned considerably as a result of very high-cost
demonstration projects, a lack of "breakthroughs," and the downturn in oil prices.
Most such sources, with the notable exception of small hydroelectric plants, were
too costly and too sophisticated for use in developing countries even before the oil
surplus. Lower oil prices suggest even greater caution in recommendation of
renewable options where economic priorities must put low cost energy supply highon the list of national priorities.1
In some cases however, they may be the best beneficiary of new technologies, e.g.
where those technologies accelerate training or protect equipment from misuse o!
lack of maintenance. This report points out where the latter is the case.
It is also important to note that advanced technologies are developed in
industrialized countries and put into application-ready form in accordance with
quality, reliability, and cost criteria appropriate to those countries. Manufacturers
and consultants who apply technology in developing countries, usually transfer it .s
is, without examining the implications a less demanding or more demanding context
have on the shape that technology should take. Many technical advances which a-e
used to improve performance could be used to reduce cost by accepting poorer
performance. Furthermore, equipment is usually designed assuming maintenance
skills and maintenance policies that are unrealistic in developing countries.
Determining the optimal cost/performance balance and the optimum overall energyplan for developing countries is a very complex issue.2 However electricity, in
some form and in some quality is often the key to reversing environmertal
degradation and to the beginnings of economic bootstrapping that will eventually
justify the quality and reliability norms familiar to the industrialized world.
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Application in such countries should emphasize ongoing protection of equipment,training, and economy - the latter recognizing the urgency of near term needs andultimate integration into a more sophisticated system.
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SECTION I
POWER PRODUCTION &SUPPLY/DEMAND BALANCE
Poawer Technologies, Inc.
1. POWER PRODUCTION & SUPPLY/DEMAND BALANCE
A. SUPPLY. DEMAND AND TECHNOLOGY DRIVING FORCES
Rapidly changing factors in the U.S. power generation environment, both business
and natural, are creating pressures which will significantly influence the
development and application of U.S. power generation technologies over the
foreseeable future. Many of these factors are global issues and power technologies
which are developed and applied to meet these requirements in the U.S. and other
developed countries, will be adopted throughout the world.
Utilities are showing continuing interest in operating improvements and in the
areas of: Plant Life Extension, Capacity Factor Improvement (Energy Management &
Interconnection), and Conservation. However, there are inherent constraints in these
approaches which will limit their impact on effective capacity improvements.
The current surplus in worldwide gas and oil production has produced a temporary
sense of relief for clean energy. This attitude has unfortunately slowed the
development emphasis of alternate fuel power technologies. Independent Power
Producers (IPP) tend to favor the low capital cost gas turbine options however,
utilities are hesitant in committing to long term premium energy sources and
demonstration to long term conversion to coal based fuels will be an increasingly
important requirement.
Pressures to deregulate the power generation industry is creating a new industry
entity called Independent Power Producers (IPP) in addition to the cogenerators
brought on by the 1978 PURPA legislation. These IPP envision a significant business
opportunity in providing the design, construction and operation of relatively small,
low cost, project financed generating plants (up to 200 MW). These changes are
occurring at a time when existing long range plans for capacity additions may be
insufficient to meet the unexpected higher load growth now being experienced in
the U.S. and many other countries.
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Power Technologies, Inc.
IPP are forecast to gain a major portion of new generating capacity over the
foreseeable future. The emphasis for these power suppliers will be on low risk,
demonstrated power technologies which can be reliably and economically applied at
smaller plant sizes. Primary near term candidate technologies are gas turbine
combined cycles, with coal gasification or coal derived synthetic fuels for future
fuel flexibility, and coal fueled fluidized bed boilers with conventional steam turbine
cycles.
Increasing concerns over the environmental impact of generation emissions and plant
siting are creating additional pressures which will also influence power technology
development trends. Emphasis on the development and application of higher
efficiency power cycles is likely to be the near trends in addressing this issue and
in reducing the rate of global heating due to CO2 production. Pressure to reduce
NO., SO2 and CO emission limits is growing, and is forecast to increase.
Although currently stagnated by public opposition, the disposal of municipal solid
waste by incineration and energy recovery is forecast to be a significant factor in
power generation by the late 1990's.
The following discussion on technologies must be viewed and assessed in light of
this background of market forces and uncertainty.
Conservation' [A]
Energy conservation is superficially regarded as a direct offset to the addition of
new generation capacity or fuel consumption, and, particularly for the most easily
achieved conservation options, a more economic alternative.
The cost and effectiveness of conservation initiatives involve major uncertainties.
Regional differences are important, as are program details. See Figures I-1 and 1-2.
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4.000 - so-w wm *wsf - MCW _ " 2.4
M _ kWhsv | _ 2.1
°kW savs
3,000 _ _ 1.8
3u000 I- 11
t 09
1,000 0
Figure I-2. Air Conditioner Demand and Energy Savings as a Result ofElcrcUtility Promotion of Energy-Efficient Units Vary Significantly
Among Utilities. (Source: Electrical World, August 1983, p.85)
1,200 -WaIWAGOWes .Mwg uas,m
1.000
I~~~~~~I3
Figure 1-2. Benefits of Electric-Water-Heater Conservation to a Utilityare a Function of Technology. (Source: Electrical World, August 1983,p.86)
Power Technologies, Inc.
Economic analyses of conservation options are difficult. It is often an
oversimplification to view conservation as negative generation. For example, the
Philadelphia Electric Company (peak demand: 6500 MW) studied eight conservation
programs:
A. "House doctor" thermal rebates
B. Commercial lighting rebates
C. High-efficiency motor rebates
D. Refrigerator rebates
E. Central air conditioner rebates
F. Room air conditioner rebates
G. Mail order conservation services
H. Third-party megawatt contracting
Figure 1-3 shows that most appear attractive on a utility investment-per-kW basis.
But Figure 1-4 shows that the overall effect of all of them is to raise average
electricity costs.
PeakReduction 240 + E
24.0 +(MW) -
16.0 +
8.0 _ A- C
-H
°-°~ + -+_+ G +++F
0 350 700 1050 1400 1750
Utility Investment (S /kW)
Figure I-3. Peak MW Reduction and Utility Investment for EightConservation Programs (Data Source: Philadelphia Electric Co. "IntegratedResource Plan")
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PeakReduction 24.0 E B
(MW) 240
16.0 +
8.0 + AC
H
0.0+ G ° F
0.00080 0.00160 0.00240 0.00320 0.00400 0.00480
Reserve Requirements Increase (¢/kWh)
Figure 1-4. Peak MW Reduction and Revenue Requirement Increase forEight Conservation Programs. (Data Source: Philadelphia Electric Co.,"Integrated Resource Plan")
Among the most highly leveraged conservation programs are:
o Thermal insulation campaigns to reduce both heating and coolinglosses, where both involve significant electrical consumption.
o Time-of-day metering, penalizing use at peak periods.
O Demand-limiting controls for commercial and industrial facilities.
O Replacement or upgrading of energy intensive industrial processes.
Conservation must always be viewed in its broadest context since increased use of
one energy form may result in a net saving in total energy or in a particularly
scarce fuel. Automation of processes, for example, may actually increase electrical
use but reduce total fuel consumption significantly.
( See also "Load Management")
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Power Technologies, Inc.
Control . 7. 8 [A]
Power plant control represents a highly leveraged investment in plant economy,
security, and life-extension. It remains a rapidly evolving technology.
New and retrofit controls are now all digital, distributed processing systems. The
reliability of digital controls is so high that it is feasible to make the entire plant
operation dependent on control functioning. However just as early automobiles were
designed as "horseless carriages," most commercial digital controls simply replicate
their analog predecessors. The real potential of digital systems is just beginning to
be tapped. Among the new functions that digital controls allow are:
o Thermal simulation of turbines, boilers and auxiliaries either tocontrol start-up and shut-down or impose limits on operator-initiatedactions, to minimize the risk of damage.
o Simulation of the combustion process as an aid in optimizingoperating variables such as excess air, temperatures and pressures.
O Optimum start-up and shut-down logic for pulverizers, boiler feedpumps, fans, etc.
o Performance monitoring of plant components, including analysis ofperformance data and maintenance recommendations.
o Simulation of turbines and boilers, initially for precommissioningcheckout of controls and later for operator training. Checkoutsimulators allow replication of emergencies that would not be a partof shakedown in full-scale plant tests. They also speed up plantcommissioning.
o Increased use of automation augmented by expert system application.
These extensions to control functions represent logical, cost-effective enhancements
to the "stripped down" controls which unfortunately resulted from an intensely
competitive power plant market. They also represent a good example of where
developing countries have a greater need for "stretch" technology than industrialized
countries. In the latter, skilled and experienced operators plus a well estahlislL;d
maintenance infrastructure already assure reasonable care and support of fJIan
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equipment. In developing countries plants are more apt to be misoperated, incipientproblems less likely to be detected, and maintenance more difficult. Thus theinherent power of digital control and automation should be used to the fullest toguide operation and protect equipment.
Fibre-optics are increasingly popular in plant control communication. They arerugged and virtually insensitive to noise which often plagues electrical controlwiring in plants.
Disnersed Generations [A]
"Dispersed' generation refers here to a variety of power plants, usually in the rangeof a few kW to hundreds of MW, not necessarily owned by a conventional utility,but connected to the utility network at the subtransmission or distribution level.This includes installations which make use of waste heat or steam produced in thegeneration process (cogeneration). Cogeneration may offer efficient use of scarcefuel in many countries.
Dispersed plants have become increasingly popular for a variety of reasons,including the economies sometimes achieved through combining generation with theindustrial processes, and laws which require utilities to purchase excess power atrates favorable to the seller.
The trend is encouraged by emphasis on deregulation, i.e. the concept that anyorganization should be free to build and operate power generating facilities,competing with the utility and others to supply load.
Dispersed generation need not involve any new power generation technology. Itdoes, however, involve new challenges at the system and institutional levelincluding:
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O Adapting a transmission network to an unknown pattern ofgeneration, considering transmission line thermal capability, stability,and protective relay coordination.
o Operation of a system where some of the generation is not undercentral control.
o Providing reliable back-up to generation which is neither plannednor controlled centrally.
o Anticipating and providing for system effects inherent in somedispersed generation, e.g. harmonic generation, and reactive powerdemands.
o Accommodation of safety problems inherent in some remotegeneration sites.
Most experts consider the further development of independent generating plantsinevitable, encouraged in part by the difficulty in gaining approval for conventionalutility plants. However, any country adopting a policy that encourages dispersedgeneration should thoroughly study the system challenges inherent in that policy,particularly the need for close communication and cooperation between independentgenerators of power and the utility system to which that generation is connected.
(See also "Wheeling'" in Section V.)
Environmental Accommodation [A]
Electrostatic precipitators and baghouses are commonly used for removal ofparticulate matters from fuel gases. Most utilities prefer precipitators except wherespace is at a premium.
"Scrubbers," using limestone to remove sulphur-dioxide from flue gas, are nowuniversally applied to coal-fired plants in industrialized countries. They increasethe equipment first cost of a plant by about $150-250/kW, almost double the plantmaintenance cost, increase the heat rate, and will reduce availability somewhat.
Scrubbers also use a great deal of water - up to 1 gallon per minute per MW.
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TEilese disadvantages weigh against application of scrubbers in developing countries
JJ zere environmental priorities suggest better application of financial resources.
Nitrous oxides (NO.) are not affected by scrubbers and can best be controlled by
bur ners which minimize excess air. However thermal nitrogen fixation by ammoni
i..jection is another technology gaining industrial application popularity.
Cooling towers, either natural or forced draft, have changed very little. They are
of en called for in developed countries through concern over heating rivers or
lakes, and in developing countries simply for want of adequate cooling water.
(See "Conservation")
ExDert System ADDilcatlon [PI
Expert Systems, now in the prototype stage, have been developed to improve plant
performance, enhance operational safety and supplement equipment maintenance.
This capability may be particularly important in developing countries where
operating and maintenance expertise is not generally available. Expert system
applications include:
o automated analysis of equipment performance trends to identifyand/or implement changes to operating procedures to improveperformance
o identify longer term maintenance requirements and timing
o alarm diagnostics for safe operator reactions
o sequence of event analysis and resolution.
Fast-Valvinll [A,,]
Generators are deliberately tripped on some systems to preserve stability. As an
alternative, output on reheat units can be cut very quickly by intercept or bypas
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valve operation. Fast-valving is not widely used, though many plants are capable of
applying it.
Insvection and Maintenance Scheduling [Al
Performance monitoring and inspection during overhaul are increasingly important
inputs in establishing what maintenance needs to be done. Newly introduced
performance monitoring systems, designed for retrofitting as well as for new plants,
warn of individual plant component degradation. Once maintenance is undertaken,
modern inspection procedures correct operating practices and establish the timing of
future maintenance work.
Once maintenance needs are known, either to restore efficiency or avert possible
breakdown, maintenance scheduling software is increasingly used to optimize the use
of down-time and to evaluate the economic trade-off between maintenance cost and
improved efficiency.
Life Extension and Plant Betterment3 [A.]
Power plant life extension and plant betterment programs have been encouraged by
the dearth of new plant construction in industrialized countries. Experience gained
through such efforts, while still very limited, will be very useful to countries the
world over.
Older, less efficient plants are often relegated to cyclical operation, thereby
increasing wear and the need for refurbishment. Life extension amounts to (I)
increasing reliability and longevity of aging components and (2) improving
efficiency to bring old plants back to economic usefulness. Many fossil-fired plants
built in the 1950's, for example, can be refurbished for costs in the range of $200
to $400 per kW, increasing efficiency by as much as 10% in the process.
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Life extension and betterment efforts generally consist of the following steps:
1. Performance tests to determine the current status of all equipmentand instrumentation.
2. Specification of a "Design Change Package" (DCP) addressing bothequipment changeout or rebuild and improvements in operatingprocedures.
3. Implementation of changes, testing, and recommissioning.
Steps I and 2 represent major efforts in their own right, ranging from thorough
inspection and test of plant components, to consideration of system level objectives,
such as operational coordination with existing capacity, maintenance scheduling,availability estimates, etc.
Recommended improvements may range from lubricating system replacement toreplacement of such major components as turbine rotors. Virtually all projects
include modernization of controls and monitoring systems.
Despite the limited experience with life extension programs, they should beconsidered a viable alternative where new construction can be postponed or
eliminated. Success is heavily contingent on the thoroughness of steps 1 and 2 cited
above, specifically on the recognition of all limitations to existing performance andlongevity.
(See also 'Performance Monitoring" and "Repowering")
Load Manaeement5 [A]
While efforts to control loads by economic incentives or direct controls go back to
the 1930's, intensive studies began relatively recently.
Shifting load from peaks to valleys, or simply shaving the peak, is very effective in
deferring capacity additions and in transferring load from high cost, inefficient
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Power Technologies, Inc.
peaking generation to economic, base load units. While each country's load pattern
is different, utilities usually find that residential load (heating, air conditioning, and
water heaters) represent the best aggregate opportunity for load control, but the
most complex to implement due to the large number of small control points.
Adjustable commercial and industrial load, while smaller contributors to overall
load swings, are larger, easier, and more often implemented targets of load
management systems.
For example, Figure 1-5 shows the effects of an aggressively-marketed storage
heater program on the winter daily load curve of a West German utility.
900
Hamburg Electric Works Daily Load Curve - Typical January Day
Figure I-5. Impact of Storage Heating
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Power Technologies, Inc.
However time-of-day rates have not always had the desired effect on consumption
patterns. This has made evident the importance of understanding consumer
response. In some developing countries availability and cost of meters suitable for
time-of-day charging is a barrier.
Less than 1% of U.S. load is controlled for peak-leveling purposes. Most of present
control is "direct," i.e., controlled by the utility without customer action. The least
common is "local control," (controlled at the customer side of the meter with no
utility intervention), and intermediate in popularity are "distributed controls,"
(controlled with inputs from both). Radio is the most common communication
medium, though power-line carrier (PLC), telephone, and cable TV circuits have also
been tried.
Load management is a very important option for any country with capacity
limitations or high peaking energy costs - if it has significant controllable loads. It
should not be undertaken without thorough understanding of customer response and
of system issues ranging from the effect on maintenance scheduling to adequacy of
and access to communication links.
(See "Conservation")
Performance Monitoriny [A]
The need for accurate and timely monitoring of power plant performance is driven
by higher fuel prices and the need to keep older plants in useful service.
Component monitoring permits the plant operator to:
o Identify controllable operating problems and ensure efficientoperation.
o Use component performance as a guide to maintenance planning.
O Compare component performance with guarantees.
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Fower Technologies, Inc.
O Develop meaningful incremental production costs to aid in systemeconomic dispatch.
Modern plant performance monitoring systems include a comprehensive set of
performance calculations. They supplement and work in parallel with power plant
operating computer systems. Calculated performance indices and warnings of
substandard operation are sent to the plant's computer system for display or alarm.
While a relatively new technology, monitoring systems should be considerce for
plants in developing countries where extending life and identifying the need for
maintenance or incipient equipment damage is unusually important.
(See "Life Extension" and "Plant Betterment")
Rgowerina [Al
'Repowering" involves replacing the fuel-handling and boiler systems of a steam
turbine with a gas turbine and Heat Recovery Steam Generators to fet!rm a
combined cycle plant. Candidates for repowering projects are usually non reheat
units in the range of 100 MW. Repowering improves heat rate and cepacity
substantially. The technology is mature, so this option should be care'Aly
considered where candidate plants exist. The repowering of existing boiler/-! tam
turbine plants with supplementary fire gas turbines can also be a viable power
option.
(See also "Combined Cycle" and "Life Extension.")
Stabllzers16, 17 [A]
Low frequency oscillations with periods of one to three seconds may de"'elop
between machine groups on systems where electrical distance is long for the pc ;ver
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Power Technologies, Inc.
being transmitted. Those oscillations in active and reactive power, and voltage may
be sustained or growing leading to what is know as dynamic instability.
This problem has long been mitigated with the use of "stabilizers" providing
supplementary inputs to the excitation systems of the problem generators.
Virtually all generator manufacturers supply stabilizers designed for their particular
excitation systems. Tuning and maintaining analog type stabilizers has been a
problem. If detuned they can make oscillations worse. That prospect, in fact, has
led some utilities to leave stabilizers disconnected.
Within the past several years digital, microprocessor base stabilizers have been
introduced using standard voltage and current inputs thus making them suitable to
any type of excitation system. The new generation of stabilizers does not need
retuning with system changes and is simpler to maintain.
Stabilizers are important adjuncts to systems which are subject to dynamic
instability, as is often the case with the 'stretched" state of systems in developing
countries. They provide the least expensive means of increasing transmission
capability in systems limited by dynamic stability.
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Power Technologies, Inc.
I~~~ ~ ~ ~~~~~~~~~ , I ISetacted Top Ratio
Oulput of Shp Algorithm
GENERATOR POWER OUTPUT
NoSlFbills r
0 1.0 2.0 3.0 4.0 5.0
TIME tsECO.OSI
Figure 1-6. Effect of Power System Stabilizer on Dynamic Stability
Figure I-7 is an example of the effectiveness of supplementary stabilizing through
excitation control.
0O REItat'l machin angle s.,ngs follo. 3m short Circb n
Mai uJ bUof tramums on circuit
10 Srlem u dbil al iONtumbers on cu,,,es id*nV)r the ma:hints.
0
.30
-tiO
0 TIME SEQTESCE30 Relati,,i macbice mngt swinp for sume dislurbanct.
20 System usumei to ts,* stali: exciulion *yulems
10 LDd stabilizers on xal units
10
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Power Technologies, Inc.
UDratinz [A]
There are some opportunities where replacement of turbine steam path components
will result in increased power output. This results from the increased efficiency of
the new parts. As an example, a majof U.S. turbine manufacturer has a replacement
last stage which will improve performance by 1.2%. This must result in increased
output of the same amount. This can only be realized if the units generator has the
capability of the increased power.
Uprating can be accomplished in other ways depending on the original constraint on
the maximum output of a unit. Design of a unit should be based on the turbine-
generator as the limiting factor. Many units built in the 1950's had excessive
capacity margin in the turbine generators. This resulted in other plant components
being the output limiting factor. Replacement of limiting auxiliaries can often
provide unit uprating.
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Power Technologies, Inc.
B. GENERATION TECHNOLOGY OPTIONS, STATUS AND DEVELOPMENT
Coal Desulphurization and Gasification4 [Ad]
The high costs for the treatment or removal of SO2, NO. and particulate matter
from flue gas with commercial systems creates a financial incentive for technologies
which can mitigate these effects. Coal desulphurization by acid leaching, catalytic
and noncatalytic nitrogen fixation, and many other techniques are being developed
and used.
The entrained gasification concept being developed by Texaco, Shell, Dow, and
others, is receiving the highest priorities. Gasification systems with capacities over
1000 tons per day and used in commercial service have been in operation for several
years.
Coal gasification is a key technology in the future use of fossil fuels for power
generation. In addition to the ability to "deep clean" the fuel gas, gasification
provides a valuable synthesis gas which can be utilized as a chemical feedstock for
a wide variety of petrochemical products. These products include clean synthetic
fossil fuels from coal, such as methanol and synthetic oils. Gasification may also
play a major role in reducing fossil fuel combustion C0 2 emissions since the fuel
gas may be shifted and the concentrated CO2 chemically removed to produce a
hydrogen fuel.
Combined Cycles
Integrated Gasification/Combined-Cycle Power Plants (IGCC)3' 4 [Ad]
Combining Gasification with a Combined-Cycle plant provides additional efficiency
opportunities by integrating process waste heat in the cycle. Coal gasification is a
particularly promising concept since contaminants are concentrated in high pressure,
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Power Technologies, Inc.
low gas volume flows which can be economically treated to high degrees of
cleanliness. The resulting clean fuel is ideal for application in large advanced gasand steam turbine combined cycles with efficiencies of 40%.
Air blown gasifiers produce a low-Btu fuel gas from the reaction of coal, steam, and
air. An intermediate-Btu gas results when oxygen is used in place of air. Combined
cycle gasifiers would operate at high pressure to produce a fuel gas adaptable togas turbine firing after appropriate cleanup to remove particulates, sulphur andother deleterious components. Steam is also produced in the gas cooling process and
can be integrated with the combined cycle steam system. Figure 1-8 presents aschematic and sample heat balance for such a gasifier used in conjunction with agas turbine and condensing steam turbine combined cycle power plant. Thisconfiguration is similar to the 100 MW Coolwater Demonstration project, utilizingthe Texaco entrained gasifier, which has been operating since 1984.
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Power Technologies, Inc.
LOSSES
13 UNITS
HHV COAL.WATER GASIfiER S UNITS100 UNItS LAND up
E LAN-U OXYG EN LOSSES4 UNItS , Y SS UNITS (AUXILIAR IES)
O UNITS POWER
LOSSES OXY GE
13 UNITSi8 UPNITSr
Fuel: Coal
Variables: Process TemperatureSteam Turbine Exhaust Pressure
Range: 80 MW - 500 MW
Advanced Art Gasifier, Gas Cleanup, Gas TurbineSystem Integration
Figure I-8. Integrated Gasifier-Gas Turbine
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Power Technologies, Inc.
The progressive generation concept whereby combined cycle plants, initially installed
and operated on natural gas or oil, can be refuelled with clean coal gas when the
fuel supply economics warrant is an attractive power generation expansion conceptwhich is being utilized to obtain natural gas permits for these plants.
The major advantages of IGCC are:
- High efficiency (35% to 40%, including gasification)
- Capability to attain very low levels of SO2 and particular emissions
- Solid wastes only 40% of a pulverized coal plant, 25% of an AFBCplant
- Capable of phased construction
- Uses coal.
- Uses only 50% of the water requirement of a conventional steamplant with cooling towers.
Disadvantages include:
- Costs are comparable to conventional coal 1,500$/kW
- Complexity
- Limited operating experience
- Land area required (300 - 600 acres for 500 MWe)
- Large water requirement.
Since none of the IGCC technologies are particularly new or exotic, all have been
tried in service, and prototype IGCC operating experience has been favorable, IGCC
plants should be considered a viable current alternative, particularly where water
and land area are not limitations, where coal is plentiful, where staged investment
is desirable, and where environmental compatibility is important.
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Power Technologies, Inc.
Pressurized Fluidized Bed Combined Cycle [A.]
A second means of utilizing coal for a gas turbine system is the pressurized
fluidized bed system illustrated in Figure 1-9. The gas turbine functions as a
supercharger pressurizing the PFB and supplying all of its air for coal combustion.
The gas turbine expands the combustion gases from 17000 F to 9150 F. The PFB bed
temperature is held at 17500 F by the simultaneous combustion of coal and heat
transfer to inbed steam generating tubes. Dolomite fed into the bed captures the
sulphur from the coal. American Electric Power is constructing a 70 MW
demonstration plant utilizing this concept which should be in operation by 1990.
Configurations of the PFB with high temperature air-cooled imbedded tubes are
presently uneconomical since high alloy tube materials are required that would
greatly increase the cost as compared to steam generation.
Improvement to cycle heat rate is marginal (one or two points) due to the relatively
small amount of gas turbine topping power as compared with other combined cycle
approaches.
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Power Technologies, Inc.
75% 1460 P, 100M f W
lOOY; 1750 F 11% fEEDWATER t I E _6 OE
COAL Avance Ar FB asceau
MODULE 17090F
600 Ff~ CYCLONESI 0% -10 °%
AIR 600 F' 4~49%e STACK +
AIR \13% i/GS OTHERCOM IN 9% POW ER LOSSES
Fuel: Coal
Variables: Process Temperature,Steam Turbine Exhaust Pressure
Range: 13 MW - 600 MW
Advanced Art PFB, Gas cleanup
Availability: 1 990
Figure I-9. Pressurized Fluidized Bed
Advanced development includes the PFB and the gas cleanup or gas turbine erosion
protection means. System integration and control would also require development.
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Power Technologies, Inc.
Combustion Turbine Plants
Gas TurbInesl 2 13 [A]
The gas turbine is a thermally versatile component which may be installed in a
variety of configurations to satisfy both power and, for cogeneration applications,
process heat requirements. Each configuration has a distinct efficiency and output
characteristic, and depends on the base firing temperature and pressure ratio of the
gas turbine under consideration as can be noted in Figures 1- 10 and 1-11.
In each example, the fuel higher heating value (HHV) is counted as 100 units. A
latent heat loss of 6 units (oil), is deducted at the combustor. Regeneration
improves cycle efficiency by exhaust heat recovery with compressor discharge as
compared to the simple cycle. The steam injection gas turbine (STIG) increases its
power and efficiency by the expansion of steam through the turbine, but reduces
the process heat available. In the combined cycle shown, the HRSG produces steam
at a pressure and temperature appropriate for expansion through a steam turbine for
process use. A condensing steam turbine would increase power output by 15 units as
compared to 10 for a noncondensing cycle.
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Power Technologies, Inc.
HHV FUEL 8 UNITS AIR 0 UNITS POWER100 UNITS LATENT POWER X 36 UNITS
48 ITSS L 1 UNIGASTURBINE ERA-
GE REGENERATIVERCENRTo~~~~~~~~~~O
UNITS LOSS
AIR ~ ~ 6 U NT OE 2UISFO A UBN
LOSS ~ ~ ~ ~ ILATIENT 1 UNIT
33UITS 1 NT
AIR 0 UNITS 1 UN
PROCESS HRSG LOSS
5 UNIS t NITSLOSS UN|10INIT
HEAT 1 UNIT HHV48 UNITS
T7 UNIT S ....
IMCYLE STACK LOSS LOSS 36 UNITSCYCLE I3UN7T4 HSGI UNITS 1I UNo. PROCESSSTEAM SYSTEM 3UHNEAT
Figure IREGENERATIVE CYCLE
STACK LOSS20 UNITS
AIR 0 UNITS ~~POWER 82 UNITS FROM GAS TURBINE
TOR 1UNIT.*..HRSG42 UNITS
83 ~~~~~~~~~POWER6 UNITS UNITS LOSS ~ ~ ~ ~ ~ ~ 0 UIT
23 UNITS HHV FUEL ~~~~STACK LOSS
21 UNITS I~gUNIS ENRA
STEAM~~~~~~~~~~STA
INJECTED ~~~~~~~~~~~~~~LOSSSTACK LOSS GAS TURBINE 1 UNITCYCLE 37 UNITS COMBINED CYC'LE1 PROCESS
H EATSTEAM SYSTEM 31 IUNITS
Figure I- 10. Gas Turbine Configurations
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Power Technologies, Inc.
Using clean fuels, the total temperature at the first stage would be 23000 F for
advanced air-cooled units and could rise to 26000 F for advanced water-cooled
units. Current state-of-the-art gas turbines operate at about 18500 F firing residual
oil and 20500 F firing distillate oils or natural gas fuels.
Simple cycle and STIG combustion turbines are an attractive option for peaking duty
on most systems. Maximum rating will probably stabilize at 150 MW. Gas turbine
technology is advancing at a rapid pace relative to the conventional steam plant
cycle. Units operating at 2300°F will be going into commercial operation starting
in 1989. Cycle options such as regeneration, gas reheat and compressor
intercooling, offer further improvements to heat rate but their cost and
complication make the approach of increased turbine firing temperature and
application of advanced steam reheat cycles for combined cycles, the preferred
concept.
Research in gas turbines includes the following:
o Increasing efficiency by raising first stage firing temperatures fromtoday's practice of beyond 23000 F by cooling the first stage withair bled from the compressor.
o Dry combustion development to achieve lower Nox and CO emissionswithout steam or water injection.
O High temperature materials and coating technology development toallow use of wider range of fuels and higher firing temperatures.
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Power Technologies, Inc.
42 - ,i~ STIG 15%SSH/,./ AC ZKX0F
4oL /STIG 10% SN
f 12 AC 22000!12
10 Tp 10 14
12 16tc AC 14
EUIS &11is I IsSTIG 10% SATRC WC p , AC220001
36 ~~~~14 AS 1212 1 12 1C
16~~~~1
z~ ~~~~h *I' o10P 7 c SMPXY2'34L 1
|C AC 2HCOO- s - 222000!A 12
M. RC WC32 BASIE ~ 12 26000!
tO 10 10F I 20000C SC SIMPLE CYCLE
3 0~7S0 AC AIR COOLEDWC WfATER COOLED
SC AC (NO HASG) RC REGENERATIVE CYCLESTIG STtAM INJIEC "ED CYCLE
S ~~~~SN SUPERHSATED STEAMSC AC SAT SATURATED STEAM'
28 ~~~~2200011
a REGENERATOR IFF!CTIVINFSS
22' 700 120 140 160 .,0 =!0
SPIECIFIC CUTP1UT KWV L3hlSEC;
Figure I- lI
Gas Turbine Performance Map
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Power Technologies, Inc.
Combined Cycles3 [A]
A steam turbine cycle can make use of a gas turbine's waste heat, in a "topping
cycle" arrangement, and currently achieve heat rates below 7800 Btu/kWhr (HHV)
at full load.
Combined cycle plants incorporating 150 MW advanced gas turbines are commercially
offered at heat rates below 7500 Btu/kWHR. These plants incorporate factory
assembled module components and have low installed cost. Because of gas turbine
modularity and ability to control air flow, low heat rates can be maintained across
most of the load range for larger plants.
Combined cycle plants can be built in stages, the steam system being postponed
until the extra capacity is needed. Combined cycles represent a mature technology
which should be considered seriously where new low cost capacity additions are
required and gas and liquid fuels are available.
Low Grade Gas Turbine Fuels [A]
Crude oil, residual, and some distillates contain corrosive components and as such
require fuel treatment equipment. In addition, ash deposits from these fuels result
in gas turbine deratings of up to 15%. They may still be economically attractive
fuels however, particularly in combined-cycled plants.
Sodium and potassium are removed from residual, crude and heavy distillates by a
water washing procedure. A simpler and less expensive purification system will do
the same job for light crude and light distillates. A magnesium additive system may
also be needed to reduce the corrosive effects if vanadium is present.
"Higher Heating Values - see "Gas Turbines."
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Power Technologies, Inc.
Fuels requiring such treatment must have a separate fuel-treatment plant and a
system of accurate fuel monitoring to assure reliable, low-maintenance operation of
gas turbines.
Research continues on the direct use of micronized coal, however there does not
appear to be any concept which would result in a successful breakthrough with this
technology.
Conventional Steam Power Plants1 0 [A]
Coal, oil, and gas-burning conventional power plants continue to be the mainstay
capacity additions for most countries. Fossil-fired plants are designed both for
base-load and cycling duty.
Steam pressures and temperatures peaked about 1960 in the U.S. at 5,500 psi and
1 200°F, respectively. Both overstretched the technology and caused serious
availability problems. Pressures for supercritical units retrenched to 3,500 psi,
10500 F but the "advanced coal-fired power plant," resulting from a major EPRI
study, calls for 4,500 psi and double reheat, anticipating full-load heat rates
approaching 8,000 BTU/kWhr. Steam temperatures for this design will be 1050°F.
The cost of new coal-fired plants will range from $1,500 to $2,000 per kW
installed, depending on location, size and, more specifically, environmental
compatibility requirements.
For pulverized coal plants up to 15% of the cost goes for pollution controls where
environmental restrictions limit air discharges and where low sulphur coal is
unavailable. Heat rates for modern plants are in the order of 9,000 Btu/kWhr.
Typical plants require I acre of land per MW of capacity.
New Oil and Gas-fired plants will likely incorporate combined cycles, but with some
reluctance due to fuel costs and fuel supply uncertainty.
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Power Technologies, Inc.
Cycles & Steam Turbine/Generators 18 [A]
Steam turbine development slowed considerably in the mid 1970's due to world
energy supply concerns and subsequent recession. U.S. load growth dropped from its
historic 7%/year level to less than 2%/year, leaving a drought in new U.S. plant
orders. In addition, the heavy focus on nuclear generation in the late 1960's and
early 1970's shifted large steam turbine development away from large turbines with
advanced steam conditions to large nuclear turbines operating under saturated steam
conditions.
Current focus in steam turbine activity is on performance upgrading of existing
units and the supply of relatively small state-of-the-art units for combined cycle
and cogeneration applications.
Reduced load growth and the anticipated increase in power supplied by cogenerators
and independent producers in the U.S., indicates that in the near term U.S. power
plants will incorporate smaller steam turbine units (eg. 200 MW) with no more than
state-of-the-art reheat steam conditions, (eg. 24000F/1000 0F/1000 0F).
With the current world concerns toward nuclear based power, and the long term
availability of oil and gas fuel, there is likely to be some continued emphasis on
larger more efficient coal power plants, incorporating advanced steam conditions.
Major world equipment manufacturers continue to explore material development,
turbine and plant designs for advanced steam cycles. A 700 MW double reheat
supercritical cycle is currently under construction by the Chubu Electric Power Co.
in Japan. Further improvements to Rankine Cycle efficiency will be marginal. If
sufficient growth in coal based generation develops there will be renewed incentive
for large steam turbines incorporating advanced steam conditions if such plants can
demonstrate economy of scale with advanced technology.
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Power Technologies, Inc.
Generator technology has remained reasonably stable over the past decade. Stators
on large machines are water-cooled, whereas hydrogen cooling of rotors is
commonplace. Water-cooling of rotors has been used in China, but is not likely to
be applied by western manufacturers.
The escalation in generator unit size foreseen in the early 1960's, while proven
unrealistic in retrospect, led to interest in cryogenic generators. It was argued
that their losses would be lower, their size smaller, and their electrical
characteristics more apt to keep systems electrically stable. Research was terminated
in the U.S., largely due to the realization that generators were already highly
efficient, that units were getting smaller rather than larger, and that the stability
advantage was probably not worth complexity and reliability issues introduced by
cryogenic cooling equipment.
Development of advanced technology generators has virtually stopped. Current sizes
with hydrogen and water cooling appear suitable for units in the foreseeable future.
Higher temperature cryogenic technology may revive advanced development in the
next decade.
Other Equigment [A]
Power plant auxiliary equipment has not changed substantially over the past decade.
However utilities now undertake more careful risk analysis to determine the degree
of redundancy or overrating. Industrialized countries, where system reliability is
critical, generally minimize the chance that plant output will be lost or curtailed
due to the failure of one pulverizer, boiler feed pump, etc. Developing countries,
while perhaps more tolerant of down time, may have an even greater incentive for
redundancy due to long repair cycles.
Probably the most important technical change in auxiliaries is the introduction of
electronics for variable speed operation of AC induction motors. This has made
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Power Technologies, Inc.
drives for fans and pumps more reliable by substituting speed control for motor-
operated hydraulic valves and fluid couplings. Retrofitting forced and induced-draft
fans on boilers, for example, allows better flow control and minimizes the risk of
boiler "implosions," following inadvertent fuel cut-off.
Boiler manufacturers are now working on two-stage pulverizers to produce
"micronized' coal, recognizing that the finer coal means less ash, greater
efficiency, due to lower excess air requirements and more complete coal combustion,
and fewer particulates in the flue gas. This work is largely developmental and most
suitable for industrialized countries.
Diesel Generation 9 [A]
Slow speed (450 rpm) diesel engines burning residual oil are typical of larger power
installations. The diesel has had a substantial growth in power output by increased
supercharging and aggregating up to twenty cylinder configurations up to 40 MW.
Diesel advancement has been evolutionary which is expected to continue. Higher
supercharge with intercooling, and charge air cooling, could permit up to 50 percent
increase in power output per cylinder. Truly revolutionary steps, such as the
adiabatic diesel with ceramic parts or the slow speed coal-burning diesel, will
require prolonged development to meet the standards of diesel reliability and low
maintenance expense. These latter are considered to be a generation beyond the
advanced diesels that will be ready for commercial application before 2000.
Figure 1-12 presents a heat balance schematic for the diesel engine. The advanced
diesel efficiency is only slightly higher than state-of-the-art diesels.
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Power Technologies, Inc.
PROCESS HEAT6 UNITS
INPUT PROCESS HEAT_ ~~100 UNITS 25 UNQITS
115" *ts135*F 39 UNITS , STACK LOSS
AIR COOLER DIESEL 9 300 F0 UNIT S |I o | >L ISE 0' 37 UNITS ELECTRIC
* | _ ~~OTHER230'F _2500 F LOSSES
4 UNITS
14 UNITSPROCESS HEAT
Fuels: Residual (Distillate)
Variable: T Process2 MW to 15 MW
Advanced Art: Higher Supercharge2500 F Jacket CoolantGreater Efficiency
Figure I-12. Diesel Cogenerator
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Power Technologies, Inc.
Diesel Generators, remain a reliable, low initial cost, short term power source.
These advantages are bought at the cost of use of restricted types of fuel and
relatively high maintenance requirements.
The maturity, modularity and simplicity of field installation makes diesel technology
a predominant choice for small remote systems of 100 MW or less.
The medium speed diesel efficiency is comparable to modern gas turbines but are
limited to much lower combined cycle efficiencies. Diesel waste heat may be used
for hot water, space heating, etc.
Diesel generators play an important role as local reserve, particularly where the
transmission tie is radial or of margin reliability for other reasons.
Direct Converters
Maunetohydrodvnamics (MHD) [P]
Figure I- 13 is a schematic for a coal fired Open Magnetohydrodynamic (MHD) cycle.
There are variation of this cycle including closed inert gas and liquid metal. This
concept offers the potential of efficiencies of 50% when combined with a Rankine
Cycle power plant. Although MHD has received considerable support for many years
and prototype experiments of key components such as the MHD generator channel,
continue at MW scale, the practical achievement of a reliable large commercial
design is many years away. The obvious complexity of this concept questions the
overall power cost and reliability of such an approach. Gas turbine cycle "topping"
approaches which simplify the configuration and improve potential reliability, have
gained stronger support.
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Power Technologies, Inc.
A C Powe to T(onslormer
o d r ICverttf S I06 1 .O02$ 1D C Po. 0.01'.1 R cti, C , P
X? "I 2 0 rl* Reoctor~fedwo,,Keoor
| iK2CO i MHD | S sioc g - O
Dried D i _ __ _ff URPul"rizedL ir H eo-8trf
cool,¢nk 00 rsdeh_ h;7
_~~~~~~~~n ;Reheqh Plssue _ ol 1D riiwiter|
Fiir Ire - 1. O
-1-35 E Aos -_
= r . ; o i e t Fe rd.otr Heolers~~ i i Inlerrmed ole ~~~~~~~~~~And So ler feed Pumps
Stoeri Condootor Sta cilaillasnorn
Condensate_ \ t Celn
Schematic Diagram of Open Cycle MHD
Figure 1-13. Open Cycle MHD Cycle
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Power Technologies, Inc.
Thermionic Generators [RD]
The thermionic steam generator is illustrated in Figure 1-14. Pulverized coal is
burned in primary air and hot recycle secondary air. Radiant and convective heat
exchange to the high temperature thermionic emitters at 1600 K drive direct current
electricity and heat energy to the thermionic collectors. The thermionic collectors
use heat pipes to discharge heat to the combustion air flow. The combustion gases
flow out of the radiant furnace zone, heating the low temperature thermionic
elements with 1300 K emitter temperature, then heat exchange with steam
superheater and steam generator surfaces. Preheated secondary air is used for
staged combustion of the pulverized coal. NOX limitation is achieved by this means.
The secondary steam generator brings the stack gas to 3000 F. Flue gas
desulphurization is applied to limit sulphur emissions. Residual oil could be
substituted for coal as fuel. This is particularly suitable for small ratings. Steam
conditions of 1465 psia, 1000° F are producible in this system. Condensing steam
turbine bottoming is used to increase power output.
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Power Technologies, Inc.
fUEL 1000
STACK LATENT HEAr SICONOAAY AIR 1OO0f
6 ° t M3 2 'ET I NPUTS 11t36.2 .203
MISCELLANEOUS , LU
AC a153.7 ^Xo25 30OANS * 13o\ETAC * 140.7 145.1
p I 120.1 I
SECONDARY AIR GOOF 4PRIMARY AIR 540F
0590.6
TO300F AMBIENTAsi RF ~~~~~ZERIO SASE
FOR HEATINTO STEAM SENSIBLE STACK BALANCE
(Power 248) LOSS AT 300Fn5OlLEA M.
Figure 1-14. Thermionic-Steam Heat Balance Based on 1000 Btu Coal HHV
Although this concept has the attraction of eliminating high temperature rotating
equipment, a thermionic power system has not been demonstrated to date and
requires extensive development to achieve the performance level of Figure I-14.
Fluidized Bed Combustion3' 4 [A.]
In fluidized-bed combustion, fuel is burned and its sulphur recaptured in a single
process, as contrasted with conventional boiler combustion where a scrubber
removes the sulphur from flue gasses. The fuel, which can be a wide variety of
solid materials, limestone (the 'sorbent"), and air are simultaneously injected into a
'bed" of intent solids. The combustion occurs in a high temperature (1500 to 16000
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Power Technologies, Inc.
C) turbulent bed of solids which acts as a fluid. Due to the solids mixing and
contact with the heating surfaces, heat is transferred from the fluid combustion bed
to water tubes at rates much higher than in a conventional boiler. Particles (the
sorbent-sulphur mixture) are removed from the vessel for separation and ash
recycle, and from the flue gas by precipitators or baghouses.
These plants utilize conventional steam cycles therefore, efficiency levels are
comparable to coal fired power plants.
The "bubbling bed" AFBC is the most technically mature of the various types, and
involves lower bed air velocity. Northern States Power Company and TVA
(Tennessee Valley Authority) are currently testing 115 MW and 160 MW versions of
this concept. The "circulating bed" AFCB, continuously transports and recycles bed
material to separation cyclones. This type of fluid bed requires higher air velocity,
but shows somewhat more promise for high capacities and eliminates troublesome
bubbling inbed tube problems. Smaller scale demonstrations have been done with
pressurized fluidized bed combustion (PFBC). The marginal potential efficiency
improvement, when integrated with an expander gas turbine, and inherent technical
problems with turbine solids flow and hot gas cleanup, put it in the longer range
category. American Electric Power is building a 70 MW PFBC plant which should be
operational in 1990.
Commercial units are being offered in the U.S. at 106 lbs/HR steaming capability by
Pyropower and Combustion Engineering. Pyropower has had a 130 MW unit in
operation at Colorado UTE Co. for over a year and is working with Black & Veatch
on the design and construction of a 100 MW power plant at the Trona, California
site of Kerr McGee. Circulating fluid beds will likely dominate near term solid fuel
power generation application in sizes from 100 MW to 200 MW. Reheat capability is
also being offered. AFB technology offers ability to efficiently burn wider range of
solid fuel types in the same boiler but has marginal economic advantage (if any)
over conventional coal boilers with flue gas treatment systems and is at an
economic disadvantage where stack treatment is not required. Ability to
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Power Technologies, Inc.
simultaneously burn clean industrial wastes, sludges and biomass fuels is asignificant technology advantage over conventional grate or suspension type boilers.
Fluid bed SO2 emissions are comparable to dry scrubbers (90% +) and NO. emissions
less than conventional boilers due to lower combustion temperatures. However, this
technology produces an ash which has leachable characteristics. This will require
development for siting where tight standard exist.
Major application hurdles for this technology are:
o Cost (approximately $1,500/kWe for capital and 17 mills/kWh forfuel). Further scale up can be anticipated.
o Although initial results are encouraging with availabilities in the 80%range, system reliability base must be developed
o Long plant lead time
o Siting of solid fuel plants
This technology is receiving heavy industry support with many commercial projects
in the 50 to 100 MW range, currently planned by IPP.
AFBC should be regarded as a technology beyond a 100 MW scale, although is still
in a prototype stage at this scale. This technology will find application in countries
where national priorities rank control of atmospheric sulphur discharge high or have
difficult or multiple solid fuels to utilize.
Fuel Cellsh [P]
Fuel cells produce direct current by the electrochemical reaction between oxygen
and hydrogen, the latter extracted from a hydrocarbon fuel (usually natural gas) by
a 'fuel processor." There is no combustion in the traditional sense.
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Power Technologies, Inc.
Hydrogen, fed into an electrolyte of phosphoric acid, generates negative charge at
the anode and positive at the cathode. Water is the only byproduct of the reaction.
Individual cells are connected into series 'stacks' ranging from 200 to 700 kWe, a
number of stacks comprising a fuel cell power plant. Stacks must be replaced after
about four years at full power output.
Fuel cells also require inverters to convert dc to ac. This adds to the initial cost,
maintenance cost, and inhibits application as a small, sole source plant in isolated
locations.
PDFC Fuel cells have been applied in demonstration programs with prototypes up to
5 MWe having been demonstrated. Commercial type units could range up to 25 MW.
The fuel cell component conversion efficiency can be over 40%,, the total generation
system efficiency, including hydrogen production, steam cycle waste heat recovery
and dc/ac power conversion can produce power at more than 50% from fossil fuel.
There are many varieties of fuel cell processes, however, the leading candidates
are:
phosphoric acid (PAFC), 2500 C
- molten carbonate (MCFC), 6000 C
- solid oxide (SOFC), 11000 C
Each of these concepts have unique development problems which must be solved
before commercial status can be achieved.
The PAFC has a high first cost ($2500/kW) projected for larger MW units. MCFC
must be integrated with a steam bottoming cycle to produce 50% efficient power at
the 250 MW size level.
These systems are relatively complex with many subsystems which require close
integration. This will tend to keep fuel cell power a higher cost option. Solid oxide
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Power Technologies, Inc.
(SOFC) technology is still in an experimental stage and requires extensive
development before commercialization.
The molten carbonate fuel cell operates at a temperature of 13000 F. Figure 1-15
presents a schematic and heat balance for a coal-fueled molten carbonate fuel cell
energy conversion system. The pressurized coal gasifier effluent gases are cooled by
an HRSG en route to the gas cleanup system. The fuel gas that is not consumed in
the anode (A) side of the fuel cell at 2000 F is burned with supplementary air in
the catalytic burner. These combustion gases with excess air provide the necessary
oxygen on the cathode (C) side of the fuel cell. The recirculation loop has an
HRSG, a blower, and a hot gas bleed-off to the expansion gas turbine. The gas
turbine exhaust passes through an economizer to be cooled to the minimum stack
temperature of 300° F. The aggregate net ac power produced is 41.4% of the fuel
energy of which 6.3% is produced by the gas turbine generator. The aggregate steam
production from all HRSG sends 47.*% heat to the steam turbine.
The simplified system would be used for a small distillate-fired molten carbonate
fuel cell. The distillate would be processed in an autothermal reformer with air and
steam to form synthetic fuel gas. That stream would be cooled in an HRSG and then
passed through a zinc oxide reactor to reduce sulphur to below 1 ppm.
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Power Technologles, Inc.
(Power 17%)
ST EA..J 1MLL N Ou HA
t l ~~72.4% 2831 .O . *et0w cc
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G ASIFI:ER CELL ELECTRIC
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MOLTEN CARUONATE PUEL CELL
Fuels: Coal, Distillate
Variables: Process Temperature 2000 F to 5000 F
Advanced Art: Molten Carbonate Fuel CellGasifiers, System Integration
Availability: 1990
Figure 1-15. Molten Carbonate Fuel Cell
The phosphoric acid fuel cell operating at 3750 F is shown schematically in Figure
1-16. The fuel gas at the anode is hydrogen. The distillate fuel oil must be
processed through a zinc oxide reactor to remove any trace sulphur. The zinc oxide
consumption results in a high operating expense. The reformer burns spent anode
fuel gas and some distillate oil as its heat source and uses the bulk of the distillate
fuel as a chemical feedstock. There is extensive heat exchange at the reformer that
heats the incoming fluid streams and cools the effluent gas streams. The shift
reactors produce a high concentration of hydrogen in the fuel gas stream. The stack
gases are cooled to 1000 F in order to recover and recycle water in the system.
The cleanliness of the exhaust products (e.g., 02, H20) is an environmental
advantage.
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Power Technologies, Inc.
Although the fuel cell operates at a nominal 3250 F to 3750 F level, other heat
exchangers operate a temperatures up to 7500 F. Process steam can be produced at
temperature levels from 1600 F to 6000 F to the extend of 0.17 of the fuel energy.
FUEL
HEAT oo%| {STAC K
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Phosphoric Acid Fuel Cell
Fuel: Distillate - Desulfurized
Variables: Process Temperature (600 F to 6000 F)
Range: I MW - 10 MW
Advanced Art Phosphoric Acid Fuel CellShift ReactorsSystem Integration
Figure I-16. Phosphoric Acid Fuel Cell
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Power Technologies, Inc.
The fuel cell's primary advantages are:
- Low environmental impact
- Relatively high fuel efficiency (40%-44%)
- Ease of waste heat recovery
- Flexible module size.
Its disadvantages include:
- Uncertain maintenance and availability data
- High capital cost (Est. at $3,000/kWe at present)
- Requires premium fuels and "fuel processor"
- Specialized technology
- Required premium fuels and "fuel processor'
- Not suitable as the sole supply on isolated systems
- Requires high grade fuels (H2, natural gas, etc.)
The long range role of fuel cells will become increasingly clear as small prototype
plants gain experience. It is not currently a practical technology for developing
countries, other than on an experimental or familiarization scale.
Figure I-17 compares the cost and efficiency of several advanced combined cycle
coal fired systems. The dash line indicate the performance of large state-of-the-art
supercritical coal fired steam plants. It will be noted from this comparison that only
the integrated gasification gas turbine combined cycle indicated a cost of power
reduction potential vs. the state-of-the-art steam plant. It would require a coal cost
of over $5.00/106 Btu for MHD to compete with the steam plant.
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Power Technologles, Inc.
I. A Liquid Meal
Iner Ges l Suprcrltical CO2Ful Cells Low F Iner 60 _ Trsture \ .t. ,'i \ ~~~~~Fuel Calls High _ _ meal Vapo
I MMDTemperature Topping
~~MAdancid SteamOopen Cydo Gas tulOlne _ _ Stndard SIOm CondlUonXSimple and tR-cuperati Closd Cycle Ces Tur,n
pen Cle bs Turbine CombinedCoal Cost
85¢/106 Btu
0 AD~~~~~~~~~~~~ Oerall Etldcinqc III
Figure 1-17. Advanced Energy Conversion Systems
'Range" of Results
Fusion. Breeders and Fast Reactors [R]
Research in fusion, breeders and fast reactors still receives considerable funding in
industrialized countries. Breeder and fast reactor concepts have been demonstrated
at various scale in the U.S. and foreign countries. Further application of this
technology depends on the timing and fate of nuclear energy for power generation.
Fusion has yet to demonstrate a sustained reaction. Furthermore, researchers have
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Power Technologies, Inc.
yet to address methods for handling the heat produced by a fusion reaction. These
problems, plus the uncertain economics of fusion generation, put it in a 30 to 40
year time frame and even then leave a question as to its long term applicability.
Geothermal PlantsM [A - Single flash, P - dual flash, binary]
Geothermal plants are useful only where special geological conditions entrain high
temperature brine close to the earth's surface. Heat is removed by "flashing" a
portion of the brine into steam to operate a turbine. Typically, less than 15% of the
thermal energy is convertible to power.
Commercial single-flash geothermal plants reflect a mature technology which
goes back many decades. Newer technologies attempt to improve efficiency and
make lower grade heat sources economic. "Dual flash" plants, for example, extract
the heat in two successive tanks, one at high pressure, the other at lower pressure.
Unused brine, plus condensate from the steam, are pumped back into the earth to
maintain reservoir pressure.
The dual flash process requires a lot of cooling water (typically 3 Million gal/day
for a 50 MWe plant). The most serious technical obstacle is scale formation in and
corrosion of flash equipment and plant piping due to noncondensable gases and
entrained solids in the brine.
Where conditions favor geothermal, typical dual-flash plants will be rated about 50
MWe and will require only about 20 acres.
An alternative binary cycle technology uses the brine to vaporize a secondary fluid
with a lower boiling temperature, which in turn drives a turbine generator. Binary
cycles return all the brine to the reservoir and therefore produce less air pollution.
They are more efficient, but more complicated, more costly and use even more
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Power Technologies, Inc.
water than the dual flash plant. The first binary plant prototypes were put into
operation in the U.S. in 1986.
Advantages of Geothermal are:
- Low fuel and operating costs
- Small land requirement
- High plant factor.
Disadvantages are:
- Useful only in special locations, i.e., site-specific
- High survey & feasibility study and field development costs
- High cost (est. between $1,500 to $2,000 per kWe)
- Large cooling water requirements.
- Environmental discharge constraints primarily on H2S.
- High maintenance of equipment.
- Lower availability compared to other types of power generators.
Geothermal generation is a practical option where geological conditions provide a
basis for it. Single flash plants represent a mature technology while dual flash and
binary cycles should be regarded as technologies to watch, pending operating results
from present prototypes.
Hydroelectric Plants14 [A]
Both the electrical and civil technologies supporting hydro electric plants are well
developed and well understood. Advances have been made in control, monitoring,
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Power Technologies, Inc.
protection and other aspects of electrical design. Units as large as 700 MW have
been installed in the U.S.S.R.
China's success with relatively low-technology hydro plants in the range from
several hundred kW to ten MW, gave impetus to the idea, now popular in the U.S.
and Canada too. Many of these plants use induction generators and require very
little maintenance. Where they serve mostly local load, power is distributed at
generator voltage.
Hydro plants in any size range are more expensive than fossil-fired plants. However
since much of the cost is labor, and much of the hardware can be locally
manufactured, many developing countries have made small, unsophisticated hydro
plants an important part of electrical development plans. China has over 90,000 such
plants and India has encouraged their development as well.
Many irrigation projects could be retrofitted with small hydroelectric generators.
Liauld Metal Tonxnlz Cycles [Ad]
Combined cycles for power generation may be configured utilizing a variety of
technologies other than gas turbines. This includes: MHD, liquid metals, fuel cells,
etc. Liquid metal topping cycles have been under study for many years. These
topping cycles utilize liquid metal working fluids having a high vaporization
temperature which provides for heat absorption and conversion at higher average
cycle temperature level while maintaining high steam conditions in the steam
bottoming cycle. Liquid metal cycles can utilize such metals as mercury, sodium and
potassium. A successful demonstration plant was built and operated by American
Electric Power Company in the 1950's. However, the evolution of the supercritical
steam cycle and high efficiency gas turbine combined cycles diminished the
advantages to be gained with the more complex and expensive liquid metal combined
cycles.
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Power Technologies, Inc.
Nuclear Power [A]
Three basic technologies remain useful in nuclear generation. They are (1) the
Pressurized Water Reactor (PWR), (2) the Boiling Water Reactor (BWR), and (3) the
Heavy Water (CANDU) reactors developed and applied in Canada. In addition,
several industrialized countries operate breeder reactors to reprocess fuel and some
research continues on high temperature gas-cooled reactors (HTGR).
BWR and PWR technologies remain at what appears to be an economic standoff. The
Candu reactor is somewhat less efficient and has the extra expense of heavy water,
but has built an enviable record of availability due, in part, to the fact that it can
be refuelled on line.
Politicization of nuclear power in the U.S., England, Germany, Sweden, Austria and
many other countries, has virtually stopped consideration of new plants and put
pressure on decommissioning of existing plants. This trend is not universal,
however. France now derives over 70% of its power from nuclear plants and has
become an international leader in nuclear technology. The U.S.S.R. also continues
with an active nuclear program, as does Japan, Korea, and Taiwan. The long term
future of nuclear is not clear, but two factors which may have a very important
bearing are:
1. An end to the current low price levels of oil.
2. Attitudes less antagonistic to nuclear.
3. Concern over global heating due to CO2.
Nuclear technology continues to develop and will likely one day be a major source
of world electricity supply. Current costs of new plants range up to $5,000 per kW,
fuel costs being from 50% to 60% of that for a similarly sized coal-fired plant.
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Power Technologies, Inc.
Ocean Thermal Energv Conversion14 [All
Scientist have long sought to take advantage of thermal gradients in the ocean for
electric power generation. While the available energy is very impressive, the
temperature differential is very limited - usually less that 200C (370F). Serious
experiments in taking advantage of this gradient began in 1926, but with limited
success. Present technology shows somewhat more promise, but is still considered
uneconomic by most experts. There are two basic Rankine cycles which take
advantage of this source:
1. Open Cycle
Open cycles use the water vapor generated by first degassing warmwater, then reducing its pressure (flashing) in an evaporator, theresulting steam being used to power a turbine. The condenser useswater from a greater depth. Warm water and cold water pumps, aswell as vacuum pumps, are required to maintain the continuous flowconditions in the evaporator and condenser.
Very large, slow turbines are needed to generate significant amountsof power. Plans for such turbines use light weight materials such asfibre-reinforced plastics.
2. Closed Cycle
A closed cycle permits use of a high vapor pressure fluid, such asammonia. Ammonia equipment and process technology is welladvanced by virtue of experience in refrigeration and in chemicalmanufacturing. However very little experience exists with ammoniaturbines.
Among the technical challenges of OTEC cycles are:
o The cold water pipe is very difficult to install andmaintain.
o Platforms accessible to cold water tend to bedifficult to install.
o Heat exchangers tend to get fouled by marine life.
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Power Technologies, Inc.
The best economic case for OTEC plants can be made by locating the plant wherewarm discharge water from a conventional plant can be used. Even under thosecircumstances OTEC plants tend to be very expensive to build and maintain.
While several small OTEC plants have been built in Japan and Hawaii, it is not, atthis stage, a practical technology for developing countries.
Ocean Currenll' [R1
Ocean currents have been used in low-energy applications since medieval times,normally mounted on bridges and used to pump river water to nearby towns.
While a variety of schemes have been proposed for electric power generation, themost popular is a series of low-speed water turbines, tethered to moorings at thebottom of a river or sea channel. Most proposals involve relatively small levels ofpower, and the technology must be regarded as largely experimental.
Solar Thermal-Electric Power Plants3 [P], [R]
The most efficient method for converting the sun's incident energy into thermalenergy useful for production of electricity is by concentrating it at one centralreceiver by means of mirrors ("heliostats"), at the focal point of each of manyparabolic dish, or along a 'solar trough." In each case the collecting mechanism iscaused to track the sun, and the concentrated heat energy is transmitted to aturbine, either as the sole energy source, or to supplement a gas-fired turbine.
A 10 MWe prototype central receiver system has operated in Southern Californiasince 1982. Parabolic troughs, a more mature technology, have also been built atratings appropriate to commercial application, although economically justifiedthrough tax incentives.
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Power Technologies, Inc.
Another form of thermal-electric conversion uses a solar pond, relying on three
layers of water, each of different density by virtue of its salt content. The high
density of the bottom layer (highest in salt content) prevents its normal rise to the
top as it gathers heat. The entrapped heat can cause the temperature of that layer
to reach 2270F, sufficient for transfer, by means of an intermediate fluid, to a
power-producing turbine generator. A 5 MWe prototype solar pond plant has been
built in Israel, and several small ones in the U.S. for direct heat use. The
technology is well established.
There are many variations of the above principals, though most are characterized by
the same general advantages and disadvantages, the former being:
- No fuel cost
- No air pollution.
The disadvantages are:
- High and uncertain capital cost
- Uncertain maintenance cost
- Limited prototype experience
- Low capacity factor
- Large land requirements.
Solar thermal power generation is not likely to be an important commercial source
for at least the next decade or two. The R&D and prototype funding needed to
firmly establish costs are very high, considering current estimates of economic
value.
(See also 'Solar Voltaic")
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Power Technologies, Inc.
Solar Voltalc3 [P]
Photovoltaic semiconductor cells convert sunlight directly into direct current. Cells
are grouped into modules, the output from which is fed to an inverter to produce
alternating current at commercial voltage and frequency.
The simplest, "flat plate" solar configurations are less efficient than systems which
use lenses to concentrate sunlight to a smaller but more intense surface.
Concentrator systems which follow the sun with a two-axis tracking system might
come closest to economic feasibility, realizing capacity factors as high as 30% to
35%, and conversion efficiencies from 12% to 20%, depending on location. The best
case for photovoltaic generation is for centralized plants up to 20 MWe. Even for
this case, capital costs are uncertain, - currently ranging about $5,000 per kWe,
with projections as low as $2500 per kWe peak in areas of greatest sun intensity.
Land estimates span an even broader range, from 40 to 370 acres, for such a plant.
Recent progress in the reliable and cost effective production of high conversion pV
cells using integrated circuit techniques, has greatly improved cell density and
offers potential for commercialization. More basic technology and production
technique breakthroughs are needed before significant power generation application
is realized.
The advantage of photovoltaic generation include:
- No fuel cost
- Minimal water requirements
- No emissions or solid wastes.
Major disadvantages are:
- High capital costs
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Power Technologies, Inc.
- Intermittent solar supply
- Very high land use.
While further technical developments and mass production could certainly improve
the economics of solar voltaic generation, this technology is not likely to be a
significant source of economic energy at least for the next decade or two.
(See also "Solar Thermal-Electric Power Plants")
Stirline Eneines [Ad]
The stirling cycle uses a helium closed cycle which approached Carnot efficiencies.
Burners atop each cylinder are supplied with highly preheated air. Within the
cylinder are dual pistons, the lower drives the crankshaft, the upper provides
helium compression and helium expansion. The displacer piston surges the helium
through an external regenerator and through a helium heater and heat rejection
heat exchanger. As noted in the heat balance scxhmatic of Figure I- 18, the 35%
engine efficiency is significantly reduced to about 28% when all system components
are included.
An industrial-size stirling engine beyond 500 kW is a significant development. Unit
sized could be in the range of 500 kW to 2 MW. Combustion of coal would
represent a further significant development effort.
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Power Technologies, Inc.
COMBU A.ST5OUL.OR 1140ATE
1O P 1472. 1E A t2F !OG
aEo .INO| COCLANL *. *Li CYCLE
PIREN£ATIR PET T s F
+|^ ~~~~1 4% ,S.-ACX
fUEL: COAL. .RESIOUAL. DISTILLATIVAAIAILE$: PROCES TE.MPERATURE 222F'O SOOF
ADVYANCEO ART; INOUSTRIAL STIRLING CYCLEAIR PAEH"TIA TO 120OFCOAL EURNER HEAT EXCHANGE)
Figure 1-18. Stirling Cycle
The advantages of slower speed engines and hydrogen working fluids could improve
efficiency by approximately 2%. The increased size and weight would appreciably
increase the cost at no increase in power output. The stirling cycle concept doesnot appear to be a major contender for future power generation.
Tidal Powers1 [Al]
Means of harnessing the power of tides for useful work go back to the 12th
century, since which time a number of ingenious schemes have been used, including
the recapture of potential energy of a heavy mass, floated to the top of a platform
at high tide.
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Power Technologies, Inc.
Modern tidal power applications, the largest of which is a 240 MWe station in
France, involve at least one storage pond (two if continuous output is required),one or more dams, a sluice system, and a power house. One of the larger projectproposed is in the Bay of Fundy, where engineers have shown a potential ofbetween 1,000 and 4,000 MWe. In England, however, schemes in the range from7,000 to 13,000 MWe have been considered. These schemes may involve either single
or double effect operation, i.e. extraction of energy either at lowering tide or at
both rising and lowering tide.
The technologies associated with tidal power are all well known. In fact a tidalplant is very similar to a run-of-river hydro plant. Apart from the normalenvironmental issues associated with large civil engineering projects, tidal power
may also affect certain tidal ecosystems.
Tidal power is limited mainly by its high cost and the limited number of sites whereboth tidal and coastal geographic conditions are suitable. It will have very limiteduse for electrical generation in developing countries, though may, on much smaller
scale, be useful for its traditional role as a drive for mills.
Wave Enerev Conversion's [R]
The prospect of exploiting wave energy has fascinated engineers for at least 100
years. Dozens of innovations have been proposed and tested on a small scale,including:
o Hydraulic pumps, driven by wave perturbation of an air-filledcylinder.
o A cam-shaped "duck" which rotates with wave action, acting againsta gyroscope to drive a hydraulic pump.
O A "sea clam' consisting of several flexible bags configured to usewave action to force air into a turbine.
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Power Technologies, Inc.
O A barge, large enough to straddle several waves, under whichvariations in air pressure are captured by a number of cylinders,rectified, and used to drive an air turbine.
o A series of hinged barges, the relative tilting of which is used todrive hydraulic pumps.
o Wave amplifying channels, built into the shore-line, which causewater to spill over into a reservoir which, in turn, drives a low-head hydro plant.
o Vertical "flaps," anchored to the sea-bottom, whose forward andbackward rocking energy is capture by a hydraulic damping device.
o Hydraulic pumps driven by the rising and falling action of floats.
O Dome-shaped wave focusers, directly couple to a low-speed turbinegenerator.
It is too early to gauge the usefulness of wave energy, but early experiments
indicate that it is a very high-cost option, both in terms of initial and maintenance
expenses. Of the options tested, the wave amplifying channels appear the most
economic, though they require special shore-line features. Visual, ecological, and
navigational impacts may also be impediments.
Waste-Burnina Plants 19 [A]
Plants up to 50 MW have been built to burn solid refuse, from which non-
combustibles and toxic materials have been removed. Incinerators for municipal
solid wastes have been commercially operated for many years. Problems with
combustion, slagging, corrosion, surface fouling, unsteady power production and low
availabilities are inherent with the nature of and wide variations in fuel
constituents.
The steam turbines and power cycles associated with these fuels generally employ
low technology components (750 psig, 750°F nonreheat steam conditions). Material
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Power Technologies, Inc.
improvements and power cycle configurations which allow increased steam conditions
(to 900°F) with supplemental fuels are possible and have been proposed.
Justification for waste-burning plants rests in part on their waste-disposing
function. They are difficult to justify solely on economics where land-fills are
available.
Wind Power3 [Al]
Experimental wind turbines have been built up to 1 MWe, though most have been in
the 100 kWe range, clustered into "wind farms' to centralize maintenance and
operating support, take advantage of a good location, and minimize environmental
impact - primarily noise and visibility.
Wind farms occupy large land areas, probably in excess of a thousand acres for a 20
MWe capacity plant. Capacity factors are also low, usually below 20%, making the
land per kW unusually high.
The cost of wind power in moderately large farms is estimated at between about
$1,300 and $1,900 per kWe, though these costs must be viewed with an awareness of
the low capacity factor that can be expected. Operating costs are estimated in the
range from 10 to 25 mills/kwHr.
Advantages of wind power include:
- No fuel requirement
- Minimal ecological impact- Remote, isolated operation is feasible
- Short delivery time.
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Power Technologies, Inc.
Disadvantages include:
- High (often sophisticated) maintenance burden
- Large, specialized land area requirements
- Low capacity factor ... need for energy storage method
- High initial cost.
Wind energy should be regarded as suitable only for experimental or highly
specialized applications, e.g. in isolated locations where fuel transport costs would
otherwise be very high, where intermittent operation (e.g. for pumping load) is
acceptable, and where maintenance access is not difficult.
U.S. activity in wind power subsided with elimination of state and federal subsidies.
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SECTION 11
ENERGY STORAGE
Power Technologies, Inc.
II. ENERGY STORAGE
Battery Storaze2 0 [R]
Large scale storage of electricity by batteries has been the subject of industry
research for almost twenty years. Schemes ranging from static batteries such as the
familiar lead-acid units, to circulating reactant systems resembling a complex
chemical plant have been explored. Most have a cycle efficiency between 65% and
75%, similar to pumped hydro.
Battery storage is an attractive option technically since it can be used in small
sizes, permitting "local" storage, and because the charge\discharge cycle can be
reversed quickly enough to allow the battery to stabilize the system during dynamic
swings. It is expensive and, at least in the case of lead-acid cells, cycle life
requires replacement every 8 to 16 years. Zinc-chloride and other battery options
may ultimately have longer life and lower cost, but are still in an early
developmental stage. The cost of battery storage is increased by the fact that a
rectifier/inverter is needed to convert from ac to dc or vice versa.
The overall economics of battery storage are generally unfavorable. For example, a
recent study of a peak-shaving battery system for a subway system (ideal by virtue
of two sharp daily peaks and high electricity demand charges), showed that the
costs outweighed the benefits.
Battery storage is a technology worth following, since a breakthrough in battery
storage technology could profoundly influence utility loads and utility system
structure.
ComDressed Air (CAESWS [AJ]
Compressed air is an interesting storage medium because of its synergy with the gas
turbine combustion cycle. About two thirds of a gas turbine's output is used in its
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Power Technologies, Inc.
air compressor, one third being available for the electrical generator. If a
generator is run as a motor during off-peak periods, the compressor can pressurize
a reservoir which can later substitute for all or part of the compressor requirement
during the generation cycle. The result is up to three times the output of the
original turbine, paid for of course by the energy used in pressurizing the
reservoir. Efficiency is further enhanced by using turbine exhaust heat to preheat
air discharged from the storage chamber.
The storage reservoir may be in hard rock caverns, salt caverns, or in an aquifer.
Except in the latter case, a compensating pressure water reservoir is needed to
maintain constant pressure in the cavern.
In addition to a suitable reservoir, CAES plants must have access to water in the
amount of about 2,000 gallons per day per MWe.
Although the elements of a CAES plant are well proven, none have been built in
the U.S. A successful 290 MWe demonstration plant has been operating since 1978
at Huntrof, Federal Republic of Germany.
While most of the individual components of a CAES are commercially available,
there is significant uncertainty associated with this technology as a system. Its
performance at a specific site is uncertain and it appears expensive compared to
other options.
Pumped Hydro20 [A]
Pumped hydro represents the mainstay of storage technologies, but is limited to
regions where terrain permits economic reservoir construction. Pump/discharge
efficiency of most pumped storage plants falls in the range from 65% to 75%. Cost
varies considerably, depending on geographic conditions. Unit sizes suitable for
utility application will generally be larger than 100 MW. Heads of at least 300 feet
are preferred. "Turn-around" time is an important measure of any storage scheme.
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Power Technologies, Inc.
To go from full pump rating to full generation rating or vice-versa, usually takes
from 30 to 40 minutes for pumped storage plants.
Pumped hydro using underground storage has been proposed, but would require
relatively large storage ratings to be economic, e.g. 1000 MW. Apart from higher
construction costs and difficult maintenance access, operating characteristics of
plants using underground storage are estimated to be the same as an above ground
plant.
In a station at La Rance, France, pumping has been combined with tidal effects to
give efficiencies above 100%. The plant pumps sea water at high tide and
generates at low tide.
Sunerconductine MaRnetic Storage Enerey System20 [R]
A superconducting magnetic energy storage system stores electrical energy in the
magnetic field produced by a circulating current in the winding of a magnet. Typical
overall efficiencies are believed to be in the range from 80% to 90%, considering
refrigeration and ac/dc conversion loss.
Superconducting storage is very expensive, requires a lot of land, and is fraught
with technical problems. It is a technology to watch, however, both because of the
impact that local storage capability would have on system design and operation, and
because of recent dramatic advances in high temperature superconductivity.
-II-3-
SECTION III
TRANSMISSION LINES
Power Technologies, Inc.
III. TRANSMISSION LINES
Compaction21 [As]
The past decade's transmission line research has included emphasis on compact
construction to reduce transmission line cost, lessen visual impact, and to make
maximum possible use of available rights of way. The most dramatic reductions in
spacings have been at 115-138 kV where traditional clearance specifications were
established long before technical requirements were clearly understood and before
probabilistic flashover calculations were accepted.
Demonstration lines have been built with spacings as low as 0.9 meter at 138 kV
(Figures III-I and III-2) and about 2 meters at 230 kV. Typical compact
construction has allowed more spacing - usually 1.5 m at 115 and 3 m at 230 kV.
Reductions in spacing at 345 kV and higher are also being proposed, but since
conventional spacing is largely limited by surface gradients on the conductors,
compaction above 345 kV involves unusually large conductor "bundles."
Where long low voltage lines are to be built in developing countries, reduced phase-
phase spacing will also provide a significant advantage in lower reactance. For
example, a 230 kV line with compact spacing and twin conductors can offer the
same load-carrying capability as some conventionally designed 345 kV lines ... an
example of where modifications of design practices can be appropriate for
developing countries, because many such countries have no ice problem and because
occasional outages due to wind motion of conductors may be acceptable, compact
line designs may be particularly attractive.
(See also "Uprating")
- III- 1-
Power Technologies, Inc.
Figure III-1. Prototype Compact 138 kV Line - Horizontal
' /
Figure III-2. Prototype Compact 138 kV Line - Delta
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Power Technologies, Inc.
Conductorsl° [A]
Purchase and installation of transmission line conductors typically represent a third
of the total construction costs of a transmission line, and must therefore be
approached with great care. There are a variety of aluminum conductor types, the
most common of which is ACSR (Aluminum Conductor Steel Reinforced), in a variety
of stranding configurations. All-aluminum conductors and various aluminum alloy
conductors are available. Difference in conductor cost, strength, weight, and
domestic availability will effect the best choice. That choice will also interact with
the tower type. Joint conductor/structure optimization software has become an
important adjunct to line design.
Line designers normally select a conductor size that balances initial cost (conductor
and tower support requirements) equal the present worth of losses over the life of
the line. At voltages above 230 kV, corona effects may force a somewhat larger
than economic conductor, or cause the optimum cross-section area to be subdivided
to comprise a "bundle" of several conductors. In developing countries, some
applications will favor lower initial cost, higher losses, and higher electrical
gradients (noise).
Conductor temperature calculations are also critical to conductor application.
Temperature depends on the balance between heat inputs, principally ohmic and
solar heating, and heat losses due to wind and radiation. Maximum allowable
conductor temperature is governed by loss of life, by the risk that conductors will
sag to unsafe limits, or both. Since conditions vary along the right-of-way, the limit
is set by the span assumed to have most adverse conditions.
Aluminum alloys used in most overhead conductors suffer some permanent loss of
strength above 750C, a loss that depends on both temperature and time of exposure.
Since most utilities allow a 10% loss of strength over the life of a line, strict limits
are placed on emergency loading to respect that threshold.
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Power Technologies, Inc.
Because of recent progress in the understanding of temperature and loss-of-life
characteristics, many utilities have increased power flow limits. Countries with
limited economic means should pay special attention to thermal criteria to assure
that assumptions are appropriate to their circumstances.
New lines which would benefit from very high overload capability should consider
conductors specifically designed for high temperature operation. In SSAC (Steel
supported aluminum conductor), the aluminum strands are pre-annealed, so the
temperature limit (in the order of 250°C) is set by the risk of damaging the
galvanizing on strands of the steel core.
(See also "Monitoring," "Low Cost Transmission," and "Tower Optimization")
Cryo2enic Transmission [RI
Research has been done on cryogenic transmission cable both in the superconducting
range (initially in the liquid range 40 Kelvin, now possibly approaching room
temperature) and in the "resistive" range (liquid hydrogen temperature 20°K to
liquid nitrogen, 800 Kelvin). While attractive in concept, the idea had two important
hurdles. The power levels necessary to justify cryogenic cables (2,000 to 10,000 MW)
are simply too large for practical systems to accommodate, recognizing that several
parallel cables would be needed to accommodate the failure of one. In addition, the
practical difficulty of maintaining a distributed refrigeration system at such low
temperatures suggested poor availability and high risk.
Recent breakthroughs in "high temperature" superconducting materials have
reawakened interest in application for power transmission. Yet the research
timetable, uncertain economics, and inherent reliability obstacles, suggest that
superconducting applications in the power field, if ever commercially attractive,
will first occur in concentrated installations or equipment.
(See "Energy Storage" and "Generators")
-III-4-
Power Technologies, Inc.
Electric Fields [A]
There has been considerable recent study of the effects of 60 Hz electric and
magnetic fields produced by transmission lines. Means for preventing electric
shock hazards have long been known, but of more recent interest is the prospect
that those fields could have adverse health effects.
Literally hundreds of studies of electric and magnetic field effects have been done,
none showing any physiological link between high fields and disease or injury. A
small statistical correlation was shown between proximity to distribution lines and
the incidence of leukemia in children but:
o The experiments are suspect to challenge insofar as objectivity isconcerned.
o Other experiments, involving people with unusually high exposure tofields, show no correlation.
o Magnetic fields in most household, school, and commercialenvironments far exceed those found under transmission anddistribution lines.
Thus there is no substantial evidence showing harmful electric or magnetic fields
associated with overhead or underground transmission or distribution lines. They
should not be a factor in deciding on their construction, other than necessary to
prevent electric shocks by induced voltages on nearby objects.
Fibre-Optics 7 5 [A.]
Fibre Optics are already widely used in communications and in equipment
applications. Of particular current interest is their incorporation into the center of
shield wires on electric power lines. Several manufacturers will supply such shield
wire and considerable field experience has now accrued.
-111-5-
Power Technologies, Inc.
Fibre optics have far greater signal capacity and immunity to noise and to surges
than carrier current systems, and are usually much less expensive than microwave
links.
Early suspicions that lightning strokes would damage the fibre-optic link appear ill
founded. To the author's knowledge, there has been no instance of such damage.
As with any fibre-optics installation, maintenance and repair demand specialized
tools and skills. Apart from those considerations, fibre-optic ground wires should be
regarded as a viable application where a transmission right-of-way is to be used for
communication or relaying.
(See "Control")
Hih Phase Order (HPO)22 [P]
It was demonstrated in the 1960's that increasing the number of phases from the
traditional three to either six or twelve, allowed unusually high loading on a
relatively narrow right of way; experimental circuits have since been built and
tested using both six and twelve phases. Six-phase line is pictured in Figure III-3.
L~~~~~ A
Figure 111-3. Experimental Six-Phase Line
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Power Technologies, Inc.
Because HPO produces lower conductor electrical gradients for the same spacing, it
also appears useful in uprating double circuit three phase lines where the conductor
would otherwise be too small. Economic studies have shown cases where savings in
losses alone would justify the conversion to six-phase. In the U.S. serious
consideration is being given to conversion of a 115 kV double circuit line to six
phase operation for that reason.
Economics show HPO to be competitive with UHV for very large transfers of power.
Some developing countries have shown interest in HPO since it would allow the
same transfer at a lower voltage than three phase, permitting use of domestically-
made equipment.
This technology should be considered quite tentative until prototype lines have
demonstrated satisfactory performance.
Hkih Voltaue Direct Current (HVDC)2 3 [A]
HVDC has seen wide spread, successful application over the past two decades. It has
proven a valuable recourse in systems where:
o Transmission distance causes the lower cost of dc overhead line orunderground cable to justify the added expense of HVDC terminals.
O The power transfer that is economically justified is less than theac capacity needed to connect two systems stably.
o Characteristics of the two connected systems are incompatible, e.g.differences in frequency.
o The damping capability of HVDC is valuable in maintaining stable actransfer.
Most HVDC lines have been justified on the basis of one or more of the above
arguments. While few are based solely on distance economics, it is of interest to
note that, at a cost of about S50/MW per terminal, the "break even" distance for dc
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Power Technologies, Inc.
from 350 to 450 miles of overhead line and from 20 to 40 miles of underground or
undersea cable.
In some cases dc has been applied "back-to-back," i.e., as an asynchronous coupler
without any dc transmission line at all. This is useful where there is a frequency
difference, a strong incentive to limit fault current or to control exchange between
systems. Back-to-back dc costs about 85-90% as much as two independent separated
terminals. Of course this application fails to take advantage of the inherently less
expensive transmission that could be interposed between rectifier and inverter
terminals.
When power must be tapped off along a transmission corridor, ac transmission has
the advantage of flexibility. However, modern controls make multi-terminal HVDC
feasible when the economics justify intermediate HVDC taps. One multiterminal
system has been commissioned in Europe. A five terminal HVDC system is under
construction in North America.
In theory, small series taps could be inserted in a dc line, but planners are
reluctant to jeopardize the reliability of a major tie just to gain access to the line
for a small level of power. The cost of smaller taps tend to be disproportionally
expensive.
HVDC is now entirely based on thyristor technology. When large Gate-Turn-Off
devices become commercially available at attractive prices, cost reductions will be
possible in converter stations.
Inspection and Maintenance [A]
Transmission line inspection has been made much easier through the use of aircraft,
particularly in colder climates where thermographic inspection methods are
applicable. Such an inspection is particularly important prior to significant
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Power Technologies, Inc.
increases in line loading. Thermographic methods allow the user to identify bad or
poorly made splices and dead ends.
X-ray equipment, put into the proximity of the conductor with a hotstick, may be
used to locate strand breaks due to excessive aeolian vibration. If such damage is
found, vibration dampers may be installed to prevent further deterioration.
Live-line-maintenance is now common for voltages up to and including 500 kV. The
cost of equipment and training necessary for safe and effective live-line work is
usually more than offset by the value of continuity of service for the maintained
line. Training courses and conferences specific to live-line work should be made
use of by utilities beginning live-line programs or extending them to higher
voltages.
Novel construction methods involving live line techniques can be used for a line
remaining in service. For example, temporary bypass structures or sections of
cable can be used while the main structures are rebuilt or replaced.
(See also "Monitoring," "Uprating")
Insulators [Al
Basic porcelain suspension insulators have changed very little in the past several
decades. Their glass counterparts have won increased acceptance, though not
uniformly. Most U.S. utilities still fear the susceptibility of glass to shattering
when hit by rifle fire. Countries who have used quality glass insulators regard them
as a reliable option.
Fiberglass insulators have evolved as another reliable alternative to porcelain, as in
Figure 111-4. Several manufacturers have demonstrated success with units having
significantly better electrical performance than their porcelain counterparts.
Improved power frequency (contamination) performance in kV per length of insulator
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Power Technologies, Inc.
is possible with synthetic insulators compared to porcelain. These advantages are
particularly important in uprating, where clearances are limited, or in regions
subject to atmospheric pollution. Because they are relatively new, utilities are well
advised to use only those fiberglass units that have extensive field experience,
accepting units of newer design only on a prototype or experimental basis.
Figure III-4. Non-Ceramic Insulator
Monitoriun Systems 25 ' 26 [RD to A.]
Monitoring of transmission lines will become an increasingly important technology,
albeit mainly confined to industrialized countries and to prototype service over the
next decade. Instrumentation ideas range from a "doughnut" current transformer
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Power Technologies, Inc.
and instrumentation unit to robots traveling on the conductors. Doughnuts are
already marketed, robots mainly in the conceptual stage.
Real-time conductor thermal rating is high on the list of application possibilities
[III(5)]. The thermal capability of a line is based on relatively conservative
assumptions of ambient temperature, wind, and solar radiation. Knowing actual
conditions, including conductor temperature, would allow greater power flow under
most circumstances. Skeptics argue that hot spots, e.g. joints, clamps, broken
strands, or areas of atypical weather, minimize the value of readings taken at
several discrete points. Nevertheless it is very likely that monitoring will be used
increasingly, not only to assess operating state, but also to detect anomalies in sag,
hot spots, insulator defects, and corona levels.
Instrumentation and real-time thermal ratings are becoming important options for
underground transmission cables, technically, because of the high thermal inertia and
economically because of the high cost of installing new cables.
Relevance to developing countries is minimal, both because of the stage of
technology and the fact that most lines in developing countries are stability or
voltage-limited, rather than thermally limited.
(See also "Maintenance & Inspection")
Shield Wires for SuDily of Local Load27 [Al]
In many developing countries, high voltage transmission lines pass through villages
which are not yet electrified or which depend on very high cost sources of power,
and whose demand does not justify a step-down substation. Shield wires can be
used as a low cost means of transmitting power to such locations, particularly
where this purpose is anticipated at the tinre the line is built.
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Power Technologies, Inc.
The simplest means of doing this is by simply using the shield wire as a single-
phase distribution circuit with a ordinary distribution step-down transformer at local
loads. Inductive coupling from the phase wires can also be used as a source of low
voltage power up to about 100 kW. The fact that the shield wires are energized
does not diminish their shielding effectiveness. However the distribution circuit must
be designed very carefully, recognizing both electrical and safety considerations.
Where clearances permit, the more conventional alternative of "underbuilding" a
distribution or subtransmission circuit on existing towers should also be considered.
Towers and Ontlmization2 4 ' 28 [A]
The past twenty years has seen major strides in the design of towers and in the
optimization of structures and conductors as a single mechanical system. Towers
have evolved to allow the use of cables for tension loading-receiving rigid members
for compression and bending loads. Figure III-5 shows a traditional steel lattice
self-supporting tower and a more recently developed "rope suspension" tower. The
use of guyed towers requires somewhat greater right of way and may present
problems in rugged terrain, but the cost savings can be significant. Experience
with guyed towers goes back almost 50 years and shows that, properly designed,
they are as reliable mechanically and as sabotage-resistant as self-supporting towers.
The optimization of transmission lines involves the consideration of all the major
cost factors simultaneously. The major determinants of transmission line cost are:
conductor size, type, and tension; tower design, placement on the right-of-way, and
minimization of high cost dead-end and heavy angle tower types; predicted electrical
loads over the life of the line; and environmental and reliability limits. For
example, in flat terrain, the use of higher conductor tensions [29, 30], made
possible with special conductors such as SDC, T2 or SSAC, or by the application of
vibration dampers, can reduce the number of towers per kilometer and/or allow the
use of shorter towers. If environmental restrictions on radio noise are reduced it
may be possible to reduce the size of conductor required and thus save both on
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Power Technologies, Inc.
conductor material cost and on the cost of supporting towers and hardware. Joint
optimization of all line cost variables can reduce the cost of lines well below the
cost of lines designed by traditional methods.
65'i 36'
in 4 44'6'
TP1
Figure III-5
-III-13-
Power Technologies, Inc.
Several advanced computer programs have been introduced for overall line
optimization. They have proven very successful in reducing cost.
Tower/conductor optimization, and the use of lighter, more efficient towers
represent a very attractive technology for developing countries. It is ironic that the
poorest countries tend to be the most conservative in terms of structure design and
conductor choice.
Ultra High Voltaee (UHV)3' [A]
Beginning with 345 kV, each new voltage was preceded by major research and
demonstration projects. The progression in voltage levels was quite steady until the
introduction of 800 kV in the Eastern U.S., Canada, and Brazil in the 1960's and
1970's. In the mid 1960's, intensive research began on "Ultra High Voltage" (UHV),
i.e., voltages above 1000 kV, primarily in the U.S., the U.S.S.R., Italy, and Japan.
Several lines have been built and operated in the U.S.S.R. where large blocks of
power must be transmitted long distances to load centers. Several were proposed in
the Western U.S., but are no longer seriously considered. Despite solution of all
critical technical problems and demonstrated economic advantage for large blocks of
load, it now seems quite unlikely that UHV will see much further application, the
reasons being:
o Growth in maximum transmission line rating correlates closely withgrowth in the output of power plants. The latter growth stoppedabout 1970 and has, in fact, reversed. Thus the function that wouldhave been served by UHV has not materialized. (See Figure III-6)
o Despite extensive research on the effects of electric fields, publicconcern remains strong enough to raise doubts as to whether a UHVline could be built in a developed country even if the need arose.
o HVDC technology has matured to the point where large powertransfers, where they are required, are usually better served byHVDC than by UHV. Where synchronous (AC) ties are needed, High-Phase-Order may also one day compete with UHV three-phase,serving the same transfer need at lower line-to-ground voltage.
(See also "HVDC" and "High Phase Order")
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Power Techmologles, Inc.
10000
0z
cc _ _ 4 F u _LARGEST GENERATOR
_ - _ -_ _ LARGEST PLANT SIZE_ _ _ -__- S.I.L. OF HIGHEST
TRAN SMISSION10 ~~~~VOLTAGE
1880 1900 1920 1940 1960 1980 2000 2020
YEAR
Figure 111-6
Undermround Cablell3 2 [A]
Underground transmission cable, used primarily in metropolitan areas or underwaterlinks, is primarily:
o Pipe-Type cable, in which an oil-filled steel pipe houses three phasesof power cable.
o Direct burial self-contained cable, where each phase or all threephases are built for direct burial without a pipe. This cable may beinstalled in duct, if required.
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Power Technologies, Inc.
O Extruded cable, which resembles the self-contained cable but uses apolythene insulation similar to distribution.
Pipe-Type cable has been popular in the U.S. because of its high reliability and
ease of maintenance. Direct burial cable predominates in Europe. Both have
traditionally used oil-impregnated paper for insulation. Extruded cable, the newest
approach, is used throughout the world too. Originally limited to distribution, it has
progressed upward in voltage to the point where France has considerable experience
with no failures at 220 kV (other than a dig-in) and now has installations at 400
kV.
The three basic cable design approaches cited above should be considered as viable
competitors. The best choice in a particular case will depend on the specifics of the
application and on financing since pipe-type cable is manufactured principally in
the U.S. and both self-contained and extruded cable for transmission voltages, only
outside the U.S.
Among the more innovative transmission cable technologies are:
o Forced cooling, wherein water or oil is circulated to remove heatfrom the duct, pipe or ground environment. This is a reasonablysound, well-developed practice, though limited in application to caseswhere high thermal rating or uprating warrants the expense.
o Flexible gas-insulated cable is being developed, largely through U.S.(EPRI) research funding, but is likely to serve only specialapplications, and only then after considerable further work.
o PPP (Paper-Polypropelene-Paper) insulated cable is a very promising,near-range technology that promises to reduce cable system cost andincrease thermal ratings. While initially aimed at pipe-type cable, itis also applicable to self-contained cable. While PPP splices havebeen used for over ten years, PPP cable prototypes are just nowbeing installed. PPP technology is understood in most cable-producing countries.
O Temperature-monitoring is particularly useful for thermally-limitedcable since the thermal time-constant of the environment is verylong.
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Power Technologies, Inc.
The three basic cable design approaches cited above should be considered as viablecompetitors. The best choice in a particular case will depend on the specifics ofthe application and on financing since pipe-type cable is manufactured principally in
the U.S. and both self-contained and extruded cable for transmission voltages,
principally outside the U.S.
UDratine Lines and Rights-of-Wav10 ,33 [A]
The uprating of existing circuits (or rights-of-way), either in terms of voltage orcurrent, probably represents the most cost-effective of all methods for improving
transmission capability.
In the U.S. a number of 138 kV lines have been satisfactorily uprated to 230 kV-
some with no change in either conductor or insulation system. Most uprating hasconcentrated on overhead lines but underground cables have been modified to
increase power transfer by as much as 34% as well.
Voltage uprating is feasible because insulation and clearance requirements are nowbetter understood and the need for large design margins is correspondinglydiminished. This change has been reflected in revisions of design codes.
The most attractive opportunities for voltage uprating occur in the range fromabout 50 kV through 230 kV where:
o The conductor is large enough to operate at the next higherstandard voltage.
o Clearance to ground and to the tower will, under present codes anddesign practices, be adequate for the next higher standard voltage.
o Insulation is adequate for the next higher voltage or can be replacedby insulators that are.
o The change-over can be accommodated by the system itself,considering:
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Power Technologies, Inc.
- The ability of the system to operate while the line isout of service, if removal from service is necessary.
- The loss of the circuit to the lower voltage network.
- The convenience of terminations at the upratedvoltage, e.g. by virtue of the higher voltage alreadybeing used at one or both terminals.
- The uprated circuit's ability to relieve a power flowlimitation by virtue of the changed system impedancematrix.
The feasibility of voltage uprating, where limited by switching surge levels, can be
accommodated by upgrading or replacing circuit breakers by breakers with surge
control resistors.
Sometimes insulator or hardware changeout can be done without removing the line
from service. Utilities have also bypassed sections of line with temporary structures,
rebuilding the removed section, moving the bypass further along, and ultimately
rebuilding the entire line. It has been suggested that this could also be done with
cable bypasses, though in both cases a thorough analysis of the technical and safety
issues must be made.
Sometimes voltage uprating would be attractive but for too small a conductor, i.e.,
excessive corona at the uprated voltage. This limit is sometimes overcome by either
reconductoring or adding a second conductor to each phase. Doing either would
normally require structural reinforcement of the existing towers.
In one case, a utility will convert a double-circuit 138 kV line to 230 kV by
simultaneously converting it to six phase. The latter reduces the electric gradient
on the conductor.
Voltage uprating of an existing line will greatly increase its load carrying capacity.
Doubling the line voltage quadruples the surge impedance loading and doubles the
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Power Technologies, Inc.
thermal capacity. However, the actual increase in transfer of course is determined
by the overall system configuration and generation dispatch.
Increase in current carrying capacity can be accomplished by a number of methods,
the most expensive of which is reconductoring. A far less expensive alternative is
the use of dynamic thermal ratings as described in the section on line monitoring.
Another uprating method simply utilizes existing materials less conservatively. For
example, actual measurement of the breaking strength of conductors has shown that
ACSR conductors with 15% to 20% steel by area can experience temperatures in the
range of 1 50°C for several weeks with little or no loss of strength. Maximum
conductor temperatures may then be increased from more conservative temperatures
of 75°C-95°C in order to increase the line rating.
Thermal rating of certain lin-es limited by conductor say at heavy load, have been
increased by 10% to 30% or more by a careful route survey and selective increases
in the clearance of certain critical spans through the addition of towers or the
raising of existing towers.
A careful study of weather conditions along the right-of-way can also provide a
basis for using less conservative weather parameters in a conventional thermal
rating calculation. Increases of 5% to 15% are possible using this approach.
Uprating of rights-of-way are of particular interest in countries where new rights-
of-way are scarce. Rebuilding on an existing right-of-way can often increase the
capacity of that right-of-way by a factor of ten or more.
Uprating remains one of the most underutilized methods for increasing the transfer
capability in developing countries.
(See "Compaction" and "High Phase Order")
-III-19-
SECTION IV
TRANSMISSION SUBSTATIONS
Power Technologies, Inc.
IV. TRANSMISSION SUBSTATIONS
Bus Configuration [A]
The progression from (1) Ring Bus to (2) Breaker-and-a-half to (3) Double Breaker,
Double Bus schemes (See Figure IV-1) generally represents a progression in
increased reliability34 and increased cost. While the breaker-and-a-half scheme is
clearly the most common and the best compromise, there will be applications where
the alternative schemes should be preferred. In developing countries, for example,
the cost savings with ring bus schemes may be more important than the reduced
reliability.
(a) Ring Bus (b) Breaker and a Half
(c) Double Breaker, Double Bus
Figure IV-1. Different Bus Arrangements
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Power Technologies, Inc.
In any case the reliability/economics tradeoffs, particularly important in developing
countries, can now be analyzed with the aid of substation reliability software.
Buswork [A]
Bus current rating should generally be coordinated with the highest future current
level anticipated on any one bus section. This may require bus rating substantially
higher than present requirements, but the penalty for over-rating bus work will
appear very small compared to the cost of rebuilding an existing substation to
accommodate system growth
The dire consequences of bus faults make careful mechanical design of high voltage
buswork extremely important. Some utilities now prefer rigid tubular bus, supported
by post insulators to the traditional suspended bus design. The former provides a
lower, more compact, "cleaner" looking station. However rigid bus has much tighter
engineering tolerances than suspended designs and makes it easier for mechanical
failures to cascade within the station. For this reason, substations which do not
demand a particularly low profile for aesthetic reasons and which may be subject to
a lack of precision in engineering or workmanship, will more safely be candidates
for suspension bus.
CaDacitors1 0 [A]
Capacitors often represent the most economic recourse in improving system transfer
capability and voltage quality. Shunt capacitors, now cost roughly $5 per kVAR
(installed) at distribution voltage and $16 per kVAR at transmission voltages. Series
capacitors cost roughly $12 to $15 per kVAR installed.
Series and shunt capacitors, now almost universally made with polypropelene film,
rather than paper, often represent the most economic way to enhance the capability
of transmission systems. In many instances, judicious use of the capacitors may
postpone the need for new lines. Shunt capacitors, more widely applied than series,
-IV-2-
Power Technologies, Inc.
increase transfer capacity by supplying extra reactive power. Series capacitors
simply make lines electrically "shorter." Both have important roles and should often
be used in combination.
Shunt capacitors are often switched (sometimes more economically on a transformer
tertiary) to accommodate changes in line loading. Where rapid response and fine
control are not necessary, switched capacitors often make an economic alternative
to static var control systems.
Capacitor switching may pose some unusually difficult requirements on switchgear,
particularly when banks are switched in parallel or "back-to-back." Any application
of capacitors should examine not only new breakers but also existing breakers
whose duty may be made more severe by adding capacitor banks.
Capacitor fusing is also a debatable issue, most European manufacturers favoring
internally-fused units (fuses on each "pack" within a capacitor can) which afford
maximum protection but which give no indication of having blown. U.S. suppliers
favor external fusing. While there are arguments for either practice, care should be
taken when internally fused capacitors are part of a tuned circuit, e.g. in a
harmonic filter, since an unknown fuse blowing can detune the bank and cause
serious problems.
As more and more shunt capacitors are added to improve transfer, systems tend to
approach voltage instability. Before approaching that point, it's usually prudent to
use some degree of series compensation.
Series capacitors, traditionally used on long, heavily loaded lines, are useful even on
compact systems if the latter are reactance or stability-limited. Series capacitors
need to be bypassed in the event of a close-in fault, lest the high voltage drop
across the capacitor's reactance cause it to fail. The advent of metal oxide arresters
gave a two-fold boost to the series capacitor option. They make application simpler,
and improve both the margin and reliability of protection. Rigid specifications for
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oxide arresters are important, since not all manufacturers have had equal success in
oxide protector application.
The problem of sub-synchronous resonance (SSR) was a barrier in the widespread
application of series capacitors. With development of new analytical toolsJ5 36
37, this problem can be studied and appropriate solutions can be implemented.Hence, this barrier has been effectively overcome.
Experts now discuss the prospect of thyristor controlled series capacitors toincrease stable transfer limits by modulation of series system reactance.
Gas-Insulated Substations (GISl 8 [A]
SF6 -insulated substations are useful in areas where the cost of land is high, the
environment is harsh, severe contamination problems exist, or where there is simply
no space for conventional stations. They occupy about one eighth the space of open
stations, but may even be cost-competitive where space limitation is not a problem.GIS also requires more specialized maintenance. GIS has been successfully applied
up to 500 kV. While there have been experiments with compact HVDC stations, GISfor dc should be regarded as being at the experimental or prototype stage.
Surge arresters presented a particularly difficult problem for early GIS gear, but
metal oxide arresters solved that problem by eliminating the need for internal arc
discharges. As with any oxide protector application, specifications should be quite
careful and rigorous.39
While GIS should be regarded as a mature technology, research is now focused on
the effect of very steep-fronted waves such as those generated by the operation of
disconnect switches.
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Power Technologies, Inc.
Groundlin and Shielding4 0 s5 [A]
Substation grounding and the shielding of control and instrument leads are poor
places to seek economies. A quality installation in either case will prevent
operating problems and the need for rework many times the original cost. The
principles of grounding in substations are well established and set forth in the
references.
Fibre optic control leads, now successfully applied in some substations, offer an
excellent way to finesse interference problems and the need for shielding. Prior to
using this technology however, utilities should have specialists trained in fibre-
optics repair and maintenance.
While some substations have operated satisfactorily with minimal shielding of
instrumentation and control wiring, it is generally advisable to use only shielded
cables unless a utility already has considerable satisfactory experience with
unshielded wiring.
Instrument Transformers IAI
Instrument transformers, potential and current transformers have changed very little
in the past several decades, even though a number of radical departures from
traditional instruments have been studied and the subject of experimentation. While
still in its infancy, optics based instruments appear likely eventually.
Protective Relays IA)
Protective relays respond to faults, overloads, voltage, instability, or other
difficulties, either isolating equipment or splitting the system. Most new relaying is
solid-state or microprocessor-based, though mechanical relays still find an
important market - principally where a new line is to match several that were built
when mechanical relays were the way to do things. No dramatic improvement in
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Power Technologies, Inc.
relay (or breaker) speed is likely since present 2-cycle speeds are close to the
inherent time needed to diagnose system malfunctions.
Relay application remains one of the most sophisticated aspects of system
engineering and one of the most leveraged areas of system investment. Relay
reliability and dependability is a matter of concern to utilities the world over.
Nuisance trips represent one of the most common and most serious outage causes
for many systems - normally because relays were not properly specified, maintained,
or because the system is being used in a manner not anticipated at the time the
relays were installed.
Some system planners feel that investments in protective relaying, including the
supporting communications systems, represent by far the lowest cost way of
improving system reliability and safe transfer limits. Optimizing relay system
investment does not mean adding relays, however, but rather opting for high quality
elements and selective use of redundancy and voting logic.
Relaying is a discipline in which developing countries will do well to develop
application and maintenance skills.
Static Var Systems36 [Al
Static Var Systems now costing roughly $20 per kVAR installed, have all but
replaced synchronous condensers as controlled reactive power sources. If properly
applied they can enhance stability and eliminate rapid voltage fluctuations. They are
cheaper, easier to maintain, and generally respond faster than synchronous
condensers.
A decade ago there was quite a variety of SVS options available.41 Present day
SVS is usually a thyristor switched reactor, a thyristor switched capacitor or a
combination of these with fixed mechanically switched capacitors. Use of SVS on
transmission voltage levels involves a stepdown transformer to 10 kV - 20 kV range.
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It is also possible to connect SVS to the power transformer tertiary taking care
that the tertiary rating allows this.
SVSs now represent a mature technology - one that is very important to full
utilization of many voltage or reactance-limited systems.
(See also "Capacitors")
Suree Arresters and BIL Specification IAl
Metal oxide surge arresters provide much lower protective levels and higher current
discharge capability than their gapped predecessor. In theory, this allows use of
equipment with lower impulse strength (BIL) and lower switching surge strength
(BSIL) than before. In practice, most utilities prefer to stay with insulation strength
they have used before, accepting protective margins much higher than the 15% to
20% which have proven a good rule in the past.
It is also wise, though not common, to undertake replacement programs of older,
gapped arresters, thus giving extra protection to older insulation that may have an
actual strength lower than presumed rating.
Recognizing the protective characteristics of Zinc Oxide arresters, present
transformer insulation levels, according to IEC standards, generally fall in the
following range:
Maximum Switching LightingSystem Impulse ImpulseVoltage Withstand kV Withstand kV
(SIL) (BIL)
300 kV 750- 850 850-1050362 kV 850- 950 950-1175420 kV 950-1050 1050-1425525 kV 1050-1175 1175-1550765 kV 1300-1550 1425-2400
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Switchgear 37 . 42 [A]
There have been few important improvements in circuit breakers or disconnect
switches in the past decade. SF6 now dominates the high voltage circuit breaker
market, though oil breakers are still manufactured up to 230 kV. SF6 breakers are
moving down in voltage rating to address the 38 kV market while vacuum breakers,
dominating the low voltage and industrial market will probably push above 38 kV to
compete with SF68. Air, as an interrupting medium, has virtually vanished above
utilization voltages.
Operating times have stabilized at three cycles up to 400 kV with two cycles as an
option at 400 kV and standard for higher voltages. One cycle breakers have been
built for special applications, but are seldom needed, considering the time needed
for accurate diagnosis of system faults.
Continuous current ratings for high voltage breakers are typically 2,000 or 3,000
amperes with short circuit current ratings typically ranging from 30 kA to 60 kA,
well in excess of requirements in developing countries.
Synchronous Condensers
Synchronous condensers are now seldom competitive with Static Var Systems. In
unusual circumstances they may be needed to support commutation in very weak
systems fed by HVDC lines.
(See "Static Var Systems")
Transformer. and Reactorse [A]
Transformers and reactors represent a very mature technology - one in which
dramatic changes are not likely. Thyristors will gradually replace contactors for tap-
changing, though this is still a prototype development.
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Volume variations in insulating oil are usually accommodated by "Conservators," i.e.
a tank with an air cushion, pipe-connected to the main tank. This works well for
slow variations in pressure but often results in tank rupture for the fast changes
associated with faults. There is considerable current interest, particularly at 500 kV
and above, in providing an air cushion within the tank to minimize damage in the
event of a fault.
Perhaps the most important current topic in transformer and reactor development is
the use of amorphous (unusually straight-grained) steel for cores. Amorphous steel
has very low losses. Quite a number of test units have been built at the distribution
level and a few for transmission application despite the increased difficulty at
higher voltages.
Introduction of amorphous-steel cores will probably be very slow and very cautious.
Their ultimate role is not yet clear and it is quite possible that the same
characteristics that reduce losses may cause resonance or overvoltage problems.
"Electrification," i.e. the build up of high static charge as a result of oil flow, is
among the more significant areas of present transformer research. Electrification,
normally associated with high velocity oil flow, is blamed for a number of
dielectric failures and has implications both in design and oil handling. Utility
engineers responsible for transformer maintenance should remain aware of this work.
Experiments have been done with gas-insulated transformers but it is unlikely that
commercial application will evolve very soon, if ever.
(See also 'Surge Arresters")
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SECTION V
SYSTEM OPERATION
Power Technologies, Inc.
V. SYSTEM OPERATION
The hardware, software, and communications equipment that dominate modern
control systems are no more important to system operation than carefully developed
operating policies, practices, and well trained staff. The former, however, are more
amenable to treatment in this report.
Anplications Software44 [A]
An increasingly sophisticated array of software is now available to system
dispatchers to aid their judgement in system operation and to produce information
needed for system control. Most relate to system security. They include:
Topology [Al - A means for determining, from telemetered and manually-entered data, the exact configuration of the system, e.g. which physicalbus sections form an electrical node and which line sections andtransformers form a network branch.
State Estimation [Al - Software which uses topology results and SCADAinputs (the later being incomplete, partly inaccurate, and non-simultaneous) to estimate a complete load-flow.
Contingency Analysis [Al - The process of identifying and analyzing theeffect of important operating contingencies, ranking them in order ofdecreasing severity and, in the most modern programs, suggesting actionsto reduce operating risk.
Operator Load Flow [Al - Allowing the operator to simulate steady-stateoperation of the system, opening or closing breakers, changing dispatch,etc. and note the results in terms easily understood by him. Someoperator load flows permit direct acceptance either of real-time or ofstate-estimator data.
Optimal Load Flow [PI - [A.1 - Software which goes well beyond normaleconomic dispatch to also develop a schedule of reactive power outputs,tap settings, capacitor or static var compensator (SVS) operating points.The objectives of Optimal Load Flows are typically (1) minimization ofproduction cost, (2) reduction of system losses, (3) improved systemsecurity and (4) improved voltage regulation. Optimal power flows arerarely used and where they are, generally provide the operator with astrategy (suggested changes) rather than being directly linked to thecontrol loop.
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Hydro Scheduling IAl - Developing short-term (hours to weeks) plans foroptimum use of hydro-electric resources considering a wide variety offactors including available water, irrigation demands, load forecasts, andthermal generation costs.
Short-Term Load Forecasts [Al - Techniques for reviewing past weatherdata, load patterns and load/weather correlations to predict load profilesfor the short-term (hours to weeks) given in current weather forecasts.Long-Term Load Forecasts [Al - Procedures for developing annual andmulti-year forecasts of load given recent history, demographic patterns,and prediction of industrial production.
Unit Commitment IAl - The decision as to when specific generator unitsshould be put into or removed from service, considering power demand,security requirements, and the cost of production and standby operation.
Maintenance Scheduling [Al - Producing a frequently updated annualschedule for taking generating units out of service for maintenance, givenannual load forecasts, maintenance needs, crew and equipment availability,and multi-unit constraint.
As with many types of modern software, the above functions are available as a
package built around a common data base.
In addition to the above, it is becoming increasing popular to use what is normally
considered as "system planning" software in the control center, sometimes capable of
accepting real-time data as its initialization. This software is used by engineers
assigned to operations planning functions. Short circuit and even dynamic solutions
can be relevant to operating strategies.
It is hard to argue against the tendency, even in developing countries, to specify
state-of-the-art application programs for new control centers. Assuming the SCADA,
communication systems, and CPUs can be maintained, good application software
allows the operator to make maximum use of whatever system he is given to operate
- a requirement even more important to developing countries.
State estimation has to be treated very carefully in that regard. While it may be
very important to make the best use of known information, it is dangerous to use
state estimation without having sufficient hard data to make the estimate accurate.
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Sparse data can lead to implied precision but mask serious inaccuracies. In fact,
one of the best initial uses of state estimation software is in the planning stages,
where the software itself is used to determine the optimum number, type, and
location of remote telemetry units (RTUs).
Control Center Confieuration [A]
Modern control center configurations are designed for a system availability of at
least 99.8 percent (cumulative failure rate of 17.5 hours per year). System
availability is a function of both the time between failures and the time to repair
and is highly dependent upon the equipment configuration. High availability is
achieved by using redundant components (e.g., computers, auxiliary memory units,
man/machine interface equipment and power supplies) arranged in various
configurations principally determined by the control system vendor. A vendor's
software subsystem design is tightly coupled to the chosen arrangement of
equipment.
Modern systems tend to employ microprocessor based communications front-end
controllers to reduce loading on the host computers. Some also use separate
interconnected microprocessor based subsystems to handle most of the display
processing.
Virtually all new systems use multicolor limited-graphic displays with special
function keyboards supplemented by light pen or trackball cursor positioning devices
as the primary man/machine interface. These are arranged in specially designed
dispatcher consoles, each with two or three CRT units. Electric utility limited-
graphic symbols are used to construct one-line diagram displays designed by utility
personnel. Full-graphic display systems, of increasing interest, represent an
emerging technology - one requiring significantly more expensive display equipment
and computers. As the technology matures over the next several years their cost
will decrease.
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Typical systems employ "mirror image" computer subsystems with certain peripheral
equipment (e.g., communication processors, printers, and display units) connected to
one subsystem or the other via computer and manually controlled peripheral
switches. One subsystem serves as primary while the other operates in a "hot
standby" mode. The data base in the standby subsystem is periodically updated
using a high-speed computer-to-computer data link. Failover from the primary to
the standby subsystem can be both manually and automatically controlled.
Configurations are increasingly being seen where two or more host computers are
connected together and with the peripheral equipment using a local area network
(LAN) such as Ethernet. LAN configurations offer greater flexibility, improved
expansion capacities and lend themselves well to distributed processing. A single
LAN can, with very low probability, present a single point of failure; therefore,
some systems utilize two LANs to ensure the desired system availability is
maintained.
Control Software44 [A]
Some software is integral with on-line system control. Automatic Generation Control
(AGC), a relatively mature technology, allocates the total MW demands of the
system among generators, continuously matching total generation with the load,
plus interchange. On interconnected systems, measured net flows between systems
combined with frequency deviation are used to guide control action needed to
maintain frequency and scheduled interchange.
The allocation commands given to AGC are developed by "Economic Dispatch" (ED)
software which minimizes the sum of production cost and the cost of transmission
losses. Modern dispatch programs also accommodate constraints, ranging from system
security to pollution control. Normal ED software is unable to schedule reactive
power output, transformer tap positions, or changes in system configuration. Those
decisions, also important influences on losses, security, and service quality, are now
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the subject of considerable industry development and are discussed under "Optimal
Load Flow" in the paragraph on "Application Software."
AGC and ED, supplementing a basic SCADA system, form the core of most
sophisticated control systems.
SCADA Systems4 6 [Al
"Supervisory Control and Data Acquisition" (SCADA) systems represent the nerve
system of energy control and the foundation for more sophisticated control systems.
The SCADA system includes:
o Sensors at remote points on the system, now increasinglysupplemented by distributed microprocessors or programmablecontrollers which improve the quality of data transmitted to thecontrol center and may also perform certain local functions.
o Communication link to the control center, by combinations ofmicrowave, power line carrier, and leased phone line. Radio linksand fibre-optic segments may also be used.
o Central processors for data reduction, control, and applicationsoftware functions. CPUs will often be distributed or paralleled toachieve response-time and availability requirements.
o Relational data bases, the most dramatic recent improvement inSCADA systems, allow great flexibility in displays and analysis ofdata.
o Color graphics systems, now universally used, typically high-resolution, and often replacing the traditional "mimic board."
Among the more current developments are "expert systems" applications to help
interpret operating data - particularly alarms. They will become very useful in
suppressing alarms that are meaningless, redundant, or in error.
SCADA systems are an essential part of energy control in virtually any country.
They are normally very cost-effective. In developing countries, one must be careful
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about oversophistication and the availability of manufacturer support for complex
hardware and software SCADA elements.
(See also "Control" and "Application Software")
Securitv10 [A]
Much of the system security issue is associated with and discussed under application
software programs in "System Operation."
The broader issue includes efforts to minimize the risk of any service interruption,
of containing that interruption if it does occur, and of speeding up restoration. The
U.S. has led the development of procedures and software to minimize and contain
interruptions. The Soviet Union has put more emphasis on minimizing their
consequences and on automating restoration.
System security standards should be carefully tailored to the requirements of each
system. It is unlikely that those requirements would be the same for systems in
both industrialized and developing countries.
Training4 6 [A]
Dispatcher training is recognized as extremely important to system security.
Courses, particularly audio/visual courses, are good at teaching fundamentals, but
there is no substitute for exercises specific to the system to be operated. One of
the most popular and effective ways to train dispatchers in the real context they'll
be working, is to use a spare CRT-based console that is able to access all the
software and displays available from the main operating consoles. Data are
simulated or come from the real-time data base. Actions initiated at the training
console are not permitted to affect the real system. Actual system condition,
including those associated with past emergencies, can be loaded for access at the
training console.
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Wheeline of Power47 [A]
Wheeling is defined as "The use of transmission or distribution facilities of a system
to transmit power of and for entities other than that which owns and operates the
lines involved." It is obviously a problem in countries which have multiple systems,
although, while as old as interconnected systems themselves, it has never been a
major issue. Networks were designed to accommodate contract flows and, to a
certain extent, inadvertent flows resulting from emergencies or equipment outages.
The movement towards deregulation and privatization has caused an increased
interest in wheeling. In the total absence of regulation, there is no control over
flows through intermediate systems and no way to plan for adequate transmission
capacity or secure system operation. The result can cause a severe economic
penalty to the intermediate system since the transmission losses (which it must
supply) are proportional to 12. Thus a company forcing a 10% increase in loading of
a line it does not own, imposes a loss increase of 21% on the intermediate utility,
irrespective of the prospect of conductor overheating, sag excess, etc. Yet it is
often in the best interest of consumers to encourage competition for generation and
to make maximum available use of transmission.
In a newly-private system, concerns over the operation and ownership of the
transmission system and future wheeling arrangements have resulted in industry
structures that associate transmission with the generating utilities in some countries
and with the distribution utilities in others. The whole issue is under debate, and
represents a particularly complex argument considering an ac system's inherent
inability to direct or regulate flows, and the difficulty in establishing fair rates for
transmission access.
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SECTION VI
DISTRIBUTION
Power Technologies, Inc.
VI. DISTRIBUTION
Distribution Automation4 8 ,49 [A]
Automation of distribution systems addresses such functions as:
o Feeder sectionalization
o Meter reading
o Load control
o Capacitor control
o Monitoring and Data collection
The economic case for distribution automation is much debated. In making economic
comparisons, for example, it is important to compare automated systems with
manually-operated systems having extended manual control options rather than with
the inflexible characteristics of many existing systems. Where automation is a
clear-cut, reasonably long term alternative to reconductoring or power equipment
replacement programs, it can be very advantageous.
Distribution automation is an example of new technology that may actually have
more application in developing countries than in industrialized countries ...
particularly where applied to load control. Developing countries often have more
incentive for load control, both in stretching the existing transmission and
distribution systems and in accommodating generation capacity shortfalls. They are
also less sensitive to the reliability degradation inevitable with intentional load
trips.
Distribution Voltaie5 0 [A]
Distribution voltages have increased over the past several decades, initial feeling
being that 35 kV would be optimum for many high density as well as rural systems.
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The reliability of 35 kV systems has been disappointing, however, particularly where
a lot of underground is used. System problems such as lightning and switching
overvoltages as well as ferroresonance which were not significant at lower voltage
become more important at 35 kV, due in part to the lower insulation margins
characteristic of 35 kV equipment. While these phenomena are well understood and
easy to avoid in the engineering of transmission systems, it is impractical to try to
anticipate all possible configurations of a distribution system - hence the need for
systems which have margin sufficient to ride through them.
15 kV distribution still appears the best choice for many systems, particularly those
in developing countries. An exception is the case where rural distribution
predominates and feeders are unusually long, in which case 35 kV may be a better
choice.
Minimum Cost Rural Distribution [A.]
A variety of innovations have been used for distribution where shortages of money
or materials makes conventional systems impossible. Single phase, ground-return
systems have been used in Australia, New Zealand, Canada, and the U.S. to serve
widely dispersed rural loads. In North Carolina, for example, a 7.2 kV single wire,
ground-return system achieved its ground at the step down transformer by extending
a local ground wire one span in either direction, terminating it in a guy and screw
anchor system. In some cases steel conductors have been used.
A World Bank/CIDA financed project in the Ivory Coast included single-wire earth
return systems using Canadian experience.
Surge Protection61' 62 [A]
Metal oxide arresters, a boon to transmission applications, must be looked at much
more carefully on distribution systems. In many cases, all the advantages of a
gapless device apply. However some distribution systems, particularly those in
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developing countries, are subject to voltage variations which are hard to predict
precisely. Thus the risk of exceeding the continuous capacity of a gapless protector
is much higher. Where that risk is significant, it may be wiser to use a gapped
arrester, thus preventing arrester current absent a bona fide fault.
Switchzear and Switchinv53, 54, 61 [A]
Although vacuum breakers are very widely used on today's distribution system, SF6 .
promises to become a significant competitor. Distribution vacuum breakers are
usually under oil, with all the attendant oil-insulated gear problems. SF6. breakers
require no oil and have a better history of operation, reliability, and safety since
failures are not explosive.
Automatic reclosing is becoming less common in developed countries. More systems
are now underground, and it makes no sense to close on underground (presumably
permanent) faults. Also, with most fault currents reaching well beyond three or
four thousand amperes for many systems, fuses operate in one-half cycle, making it
virtually impossible to save the fuse on temporary faults by reclosing. Finally, fuse
operation interrupts just one lateral whereas reclosing interrupts the entire feeder.
With more and more sensitive loads, it is often better to accept a longer outage
time if it means fewer loads are out.
System Confieuration 5 s [A]
The five basic distribution system configurations are shown in Figure VI- 1. The
radial system is least expensive and least reliable, the spot network being highest
on both counts and appropriate only to dense metropolitan load areas. The primary
loop configuration is by far the most common in the U.S. It permits isolation of
permanent faults with minimum disruption to other loads.
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PRIMARY FEODRS
(1) PAOIAL
rO LC.AOS
(2) PAIMARY
LOOP~~~~~~N
( PIMARYTO rA S
NO NoT- T
DNOARY ~~~~~~~~~~~F1OTO LOAOS) SECrTvE 1CTI_E
, SPOT1 OR TO LOADS
NETWORK TRANSFORMERWITH PROTECTOR
NO* NORMALLY OPEN SWITCHOR RAEACER
Figure VI-I - Five Basic Distribution Service Systems
There has been a strong recent trend to four-wire distribution systems, their
advantages being:
o Higher, more predictable fault current, allowing better relayprotection.
o Lower BIL.
O Economy in single-phase underground laterals (no need to use twophase-wires.)
o Greater reliability.
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Power Technologies, Inc.
Underground Cable5 6 [A]
Virtually all distribution cable is extruded, most of it cross-linked polyethylene
(XLP). Research is now focused on improved reliability, including the prospect of
more widespread use of Ethylene Propylene Rubber (EPR) due to its good failure
record. Reducing the exposure of distribution cables to surges is also felt important
to improve reliability. Evidence attributing failures to surges, particularly in older
cables, is now very strong.
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SECTION VII
SYSTEM DESIGN
Power Technologies, Inc.
VII. SYSTEM DESIGN
This section will address some of the more important issues in system design. Most
are closely linked to software and, while discussed separately here, are often
addressed by "activities" within a common software package. (See Section VIII-
Software).
Dynamic Analysis57 [A]
Modern dynamic analysis requires flexibility in problem scope, time span and time
resolution. The last decades efforts at better defining machine and load model
characteristics have resulted in their very accurate simulation. Among the features
of state-of-the-art dynamics programs are:
o HVDC models, with comprehensive control simulation
o SVS models, including controls
o Frequency-dependent system models
o Extensive libraries of protective relay models, capable of beingeither "set" to operate as they would during actual systemperformance or raising "flags" to show how they would haveoperated.
o Utility modules for estimating parameters when accurate data isunknown.
o Provisions for checking excitation system models against actualexcitation system performance.
o Provisions for eigenvalue and frequency domain analysis.
Insofar as technical capability is concerned, modern dynamics programs can carry
solutions out to steady-state values with any degree of resolution in between.
Economics of computer time however, suggest special program features for "mid-
term" stability, also inherent in leading software offerings.
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Fault Analysis
Modern fault analysis programs will handle complex combinations of unbalanced
faults, including:
o Identification of individual ground currents
o Provision for single-pole closing
o Provisions for sizing of circuit breakers.
Harmonics5 8 , 65 [A]
It is estimated that by the turn of the century, one half the power consumed in the
United States will flow through silicon. The rapid growth in low-cost thyristor
control of lighting and motor drives in virtually all developed countries has brought
the issue of harmonics to prominence. The harmonic currents generated by static
converter controlled loads flow into the system and may damage capacitors, motors
and other equipment. The increased use of shunt capacitors for voltage and
reactive power control makes it more likely that harmonic currents will see
resonant points in the system, thus amplifying both harmonic current and voltage.
Distorted voltage waveshape can affect the timing of equipment that depends on
consistency in voltage zero from cycle to cycle. Higher harmonic currents can
induce noise in communication circuits.
The industry has responded to the problem by strengthening standards which limit
harmonic currents sent to the electric utilities by encouraging filters at major
harmonic generating loads.
Harmonic generation is often a more serious problem in developing countries than in
industrialized countries. New production facilities impose loads which, in developing
countries, tend to be large relative to local system capacity, thus making the
consequences of harmonic currents more severe. Situations of this kind should
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Power Technologies, Inc.
always be preceded by analyzing the harmonic effects and determining the
appropriate solutions.
Load Flow59 [A]
Load flow programs have grown dramatically in sophistication and speed. Among
recent advances are:
o Increase in representation capacity to easily accommodate extremelylarge systems, e.g. all of the Eastern U.S. or Central Europe. Thishas virtually eliminated the need for equivalents in representation.
o Increases in speed to permit automated sweeps through a large fieldof cases.
o Economic dispatch capability to replicate actual schedule ofgeneration.
O Automatic transformer tap changer action.
o Area interchange analysis.
o Automatic generation of contingency cases.
o Programmable sequence of events.
Maximizine Transfer CaDabilitv'0 [A]
Many industrialized countries have been forced to "stretch' existing transmission
systems beyond transfer levels for which they were designed. This is due to load
growth, a dearth in new line construction, and shifting generation patterns and
transfer incentives.
The challenge of maximizing transfer capability of existing systems uncovers useful
recourses in:
o Transmission line uprating
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O Addition or modification of substation equipment
o Changes in system operation and control
o Modifications in power plant control
o Reassessment of reliability criteria.
While these studies were inspired by a system where additions were inhibited by
regulatory or environmental constraints, they are equally applicable to systems
whose expansion is limited by financial resources or which, while committed to
expansion, must do so in as leveraged a way as possible.
Prior to committing new transmission facilities, any system would do well to go
through an exercise to see what stretch remains in the existing network through a
variety of recourses such as those cited above.
Plannine6 [Al
The system planning process traditionally consisted of:
1. Forecasting Loads
2. Developing alternative generation plans and dispatch schedules.
- Aided by sophisticated simulation of reliability andproduction cost, including plant maintenance, hydroscheduling, representation of load management, etc.
3. Identifying alternative transmission system plans capable ofaccommodating new loading levels, considering thermal ratings,voltage tolerances, and dynamic behavior.
- Now based on very accurate simulation, aided by recentresearch on machine and load modeling.
- Considering a broad array of equipment options toenhance power flow control and dynamic performance.
- Basing transmission costs on preliminary optimizationstudies.
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4. "Testing" each transmission alternative against standard (severe)contingencies to assure that each alternative results in a "tough"system.
- More modern approaches go beyond "pass/fail" tests andassess the value of differences in reliability ofalternatives.
5. Selection of the minimum cost alternative.
- Considering both generation and transmission investmentand operating costs.
6. Studies of subsidiary issues, including overvoltage and protection,relaying, and communications.
Generation and transmission planning are logically coupled. Traditionally, because
of the relative investments and lead times, transmission planning tended to react to
generation planning, with distribution planning done last.
Computer programs which combine some of these steps have been developed -- e.g.,
our "TPLAN" and EPRI's "EGEAS." These cycle through menus, carry out many
analyses, and give tentative recommendations which can then be analyzed using
detailed models.
Today, in the US and abroad, new elements of planning are in the limelight. One
is the need to consider objectives of a variety of utility stakeholders: various
classes of rate payers, equity holders, creditors, the regional or national society,
etc. Related to this is the active participation of these parties in the planning
process, which is no longer the private domain of the utility. Unusual options for
customer-supplied energy sources and new utility-customer relationships are on the
table. Finally, new and critical uncertainties and risks must be accounted for.
The new planning environment, and responses to it, are discussed in Section IX of
this report.
-VII-5-
Power Technologies, Inc.
Production Simulation6 l (A]
Modern production-simulation ("production cost") programs to examine a spectrum of
time frames, ranging from short term operations planning analysis to long term
resource and strategic assessment of up to 40 years. They will simulate production
chronologically, incorporating unit commitment constraints, transactions, and unit
modeling or by handling key variables probabilistically. Such programs will
recognize multi-area transmission limitations, accommodate supply and demand side
load management strategies, storage alternatives, emissions constraints, and a
variety of other financial and operational issues.
While production simulation is most widely used by utilities in industrialized
countries, its ability to minimize production costs make it extremely helpful in
developing countries where there is flexibility in power sourcing. Table VII- I
summarizes the five principal types of production-simulation programs.
TABLE VII-I
Summary of Production-Simulation Programs
BALERIALDX MONITE QUICK ANDMETHOD CUMULANTS CARLO DIRTY DETERMINISTIC
<----------------ACCOUhNT FOR THERMAL UNIT FORCED OUTAGES----------------->
LOAD CHRONOLOGICAL PLACE-WISE USUALLY SEASONAL CHRONOOLOGICALMODEL OR LOAD- LINEAR CHRONOLOGICAL LOAD-DIRATION
DURATION LOAD-DLRATION CLRVESCURVES CURVES
RESLLTS -----------------AVAILABLE LINIT-BY-UNIT----------- AG6EGATED INDIVIDUALBY FLEL LUNITSTYPE
COMPUTER LON6 MODERATE DEPENDS ON SHORT SHORT TOTIME NUMBER OF MODERATE
GAMES
OTHER -----FAIR MCOELING OF -----> GOD MODELING MANY GOOD MODELING<--TIME-DEPENDENT EFFECTS--) OF TIME- SHORTCUTS OF TIME-
DEPENDENT EFFECTS DEPENDENT EFFECTS
CAN BE USED INACCULATE --------------CAN BE USED ON ALL SYSTEMS------------->ON ALL SYSTEMS FOR SMALL SYSTEMS
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Power Technologies, Inc.
Subsynchronous Resonance62' 63, 64 [A]
In the 1960's severe oscillations, capable of fracturing generator shafts, were
observed on systems using series capacitive compensation, it being found that they
resulted from a combined resonance of the system's electrical properties and the
mechanical properties of steam turbine-generators. "Subsynchronous Resonance" has
since shown itself to be a potential problem on a number of series compensated
systems.
The initial "fix" was to apply a filter tuned to damp the frequency of oscillation.
Subsequently less expensive devices were introduced to achieve damping.
Alternatively, system designers have preferred to reduce or eliminate series
capacitors on systems subject to this problem. In some systems the possibility of
SSR occurs only under several simultaneous contingency conditions considered to be
extremely improbable. In such cases the approach has been to use SSR detection
and accept the risk of having to trip generators.
Subsynchronous resonance is now sufficiently well understood to trigger very careful
study on any potential application of series capacitors. It should not be regarded as
reason to discount the series capacitor option, but merely as an extremely important
check to be made in system studies involving such application.
Voltage Instabilitv10 [A]
Voltage instability or "collapse" has gained new attention as systems have been
loaded closer to their steady-state dynamic limits. Without adequate voltage support
near load areas, a point can be reached where the reactive demands of loads cannot
be satisfied, resulting in rapid "collapse" of voltage. Once initiated, there is no
way to reverse the collapse process with loss of load. However there are methods
for gauging the systems "proximity" to collapse, both in planning and during the
course of system operation.
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Power Technologies, Inc.
Shunt capacitors, placed near load areas, extend the safe transfer limits of the
system but also steepen the edge between normal operation and collapse. Series
compensation helps too, without steepening that edge. Usually some combination of
the two, or with static var systems, is best.
-VII-8-
SECTION VIII
SOFTWARE
Power Technologies, Inc.
VIII. SOFTWARE
Software has become an increasingly important technology, affecting virtually every
aspect of power system planning, design, construction, and operation. An
appreciation of the changing nature of software is essential to anyone dealing with
technical, financial, or managerial aspects of electric power systems.
Artificial Intelligence [R]
Artificial Intelligence is the means by which a program, in the course of its
execution, gains and stores experience of value in later calculations. Practicability
of implementation is improving, as the Al languages (LISP, Prolog) become available
for conventional computers as well as their initial special machines.
Applications in the electric power industry are slow to appear and it seems unlikely
to see significant practical applications for several years.
(See "Expert Systems")
Data Bases [A]
Data bases, originally an inherent part of individual programs, have emerged as a
product in their own right. Modern "Relational" data bases will serve such functions
as:
o Accepting and ordering data, making unit conversions andreasonableness checks.
o Complex searching and sorting to specified requirements.
O Plotting of one variable against another, either directly from datastored or through exercise of an algorithm based on that data
o Accepting programs based on the stored data, providing a convenientuser link to that program and others similarly coupled.
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Power Technologies, Inc.
O Minimizing the effort and storage space required to establish andmaintain a date-coded general purpose data base with monitoredaccess rights and security measures.
Some data bases can be used to knit together a group of related individual programs
into a cohesive, user-friendly package. Limitation in the representational capacity of
programs that were originally designed for free-standing operation will remain
however.
Expert Systems [P]
Expert systems attempt to capture the wisdom and experience of experts and build
those inputs into software to help those with less skill. Expertise can be
incorporated directly into the program or through a question and answer procedure.
Early applications among utilities are in less sophisticated areas such as fleet repair.
The first technical applications are in areas that are largely experience based, e.g.
relay settings, training simulators, and turbine diagnostics. It is also likely that
expert systems will be used to allow those only marginally acquainted with a
technical discipline to use sophisticated programs in that discipline for the limited
scale or generalized solutions needed by the investigator or for training.
(See "Artificial Intelligence")
Hardware Trends [A]
Hardware capability and cost continue to be closely linked to software trends.
Among the key developments in hardware are:
o Speed increases continue. Sometimes measured in "MIPs" (Mega-Instructions per second), five years ago, I MIP was the cutting edgeof commercially available minicomputers. Now 10 MIP machines areoffered and 100 MIPs on the horizon.
o Costs continue to decrease at roughly 10% per year for a givenmodel, closer to 30% per year for a given compute capability.
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Power Technologies, Inc.
o Office "Work Stations" consisting of small computers, intermediate incapability between a PC and a mainframe, combined with a completeperipherals package, are becoming less expensive and more popular.
O Memory costs have decreased to the point where memory's hardly alimitation in most applications. But the industry is becoming moreaware that magnetic memory has a limited life (Usually two to fiveyears without reprocessing) and that optical memory, in addition toits immense capability, has virtually no deterioration.
o Parallel processing, originally introduced in the form of specialpurpose computers, is now showing up as an integral feature ofmodern mainframes. In some of the newest computers, the parallelingof computations is an option exercised by the compiler to makemaximum use of available CPU resources.
o Although initially unattractive due to the need for special computers,except in special applications, parallel operation of multiple standardcomputers has recently been shown to be promising.
o Personal computers are virtually universal and will continue to growin popularity and power, differing less and less from what are nowconsidered "work stations."
o High resolution color graphics systems are now widely available andwill continue to drop in price.
Of paramount importance in selecting hardware for a particular application is the
degree of manufacturer support in the installed location.
"Product" Status of Software
At first, most application software was developed by users. User groups then
formed, pooling resources to maintain and improve the more successful programs.
Commercially developed software was then gradually introduced and, as is the case
with electrical apparatus, became the logical way to concentrate development and
to accommodate the growing burden of maintenance and support. The analogy to
"manufactured" products goes further than many realize. Commercial software
developers:
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Power Technologies, Inc.
o Pool the most current needs and the best ideas of a wide variety ofusers, through market research and a broad industry interface.
O Through use of program "shells," develop code for ease of use, filehandling, modification, and maintenance. In the case of software,"maintenance" amounts to accommodating changes in operatingsystems, compilers, graphics and other peripheral devices, eliminationof latent errors, and alteration of algorithms for improved accuracyor extended scope.
o Avail themselves of sophisticated "Machine Tools" for manufacture-in this case software utility programs which help organize, write,optimize, maintain, and diagnose code. Similarly, software sourcecode maintenance programs keep a log which helps a manufacturermaintain and institute retrofits for old versions of a program.
O Initiated rigorous Quality Assurance and testing programs.
o Developed the equivalent of "spare parts" support - in this caseadditional modules to extend the useful scope of software.
o Instituted warranty and user support "hot lines."
o Launched major R&D programs to advance their product offering.
It is seldom economic for individual users to develop programs which are available
in commercial form.
Structure [A]
Until about 1970, most computer programs addressed a single, limited scope problem,
e.g. load flow, short circuit, stability, etc. Each called for its own input data, and
most simplified certain boundary conditions. In 1970 a pioneering program was
introduced which bundled four programs which used the same data. What used to be
separate programs became "activities" within a common program package. Data input
was simplified, problem-solving was more convenient, and fewer boundary
simplifications were necessary. Most modern software now uses this approach. In
system planning, for example, load flow, short circuit, stability, and a host of
subsidiary functions now share a common data base.
(See "Data Base")
-VIII-4-
SECTION IX
MANAGEMENT & STRATEGIC TOPICS
Power Technologies, Inc.
IX. MANAGEMENT & STRATEGIC TOPICS
Corporate Modelin26 6 [A]
Financial modeling of corporations goes back to the late 1960's, the basic idea being
to allow top management to interpret decisions (plant additions, rate policies, fuel
alternatives, etc.) in terms of their effect on the income (i.e., profit and loss)
statement and balance sheet. Early models were complex and tended to be inflexible.
This limited their usefulness. Current practice tends to subdivide models (e.g.
revenues, taxes, fuel costs, etc.,) defining an interface between them. In fact the
advent of spreadsheet software, such as Lotus 1-2-3, has made model-building simple
enough for most utilities to satisfy their own modeling problem. Some form of
financial modeling, if only spread-sheet based, is essential to effective utility
management in any country.
Deregulation6 7 [Aj]
Deregulation is a strong trend in the U.S. It is assumed that by making the
generation end of the utility business competitive, production costs will drop and a
new diversity in sources will obviate the need for many more large central plants.
No one disputes the need for singular ownership and operation of distribution and
transmission facilities within a given area. In the U.S. bidding systems for new
generation are being developed and implemented in several areas. There is also
pressure to require utilities to offer unbundled transmission service (i.e., wheeling)
and to allow the wheeling of power by larger customers as well as by utilities and
independent generators.
The benefits of deregulation are not without costs and disadvantages - among them:
o Difficulties in assuring adequate generation capacity when plantconstruction and decommissioning are dependent on market forces,recognizing the high risk and long lead times involved.
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Power Technologies, Inc.
O Difficulties and cost premiums associated with the conversion oftransmission systems, originally designed for a specificload/generation pattern, to one capable of accommodating a flexiblepattern of generation sources.
o Difficulties in achieving reliable operation of a system wheregeneration sources have diverse ownership and, in many cases,subsidiary purposes, e.g. steam production.
o Economies of scale, the ease and cost of pollution control, andenforcement of national fuel policies are lost, in part, withdependence on smaller, decentralized generation.
Deregulation, at least in its extreme form, should be viewed with extreme caution
prior to a clear demonstration of its advantages over assigning total power supply
responsibility, within a fixed area, to one accountable entity. It should not be
confused with "Privatization," the act of transferring state owned utilities to
private ownership.
(See "Dispersed Generation")
Enerev Modelini68 [A]
Many countries attempt, with varying degrees of sophistication, to model their
entire energy situation, from primary fuel resources to utilization. Many early
models were too complex, and buried too many assumptions to win the confidence of
decision makers. The trend has been to subdivide models into smaller, manageable
modules, allowing judgement inputs as they are used together to address larger scale
issues.
Prior to embarking on comprehensive energy modeling efforts, governments would do
well to survey the successes and failures of other countries in this field. Some of
the best work on the subject has been done by the International Institute for
Applied System Analysis (IIASA) in Vienna.
-IX-2-
Power Technologies, Inc.
Least Cost Planning6 9 70 [A]
Until the early 1970's, utility planning studies, largely centered on issues internal to
the utility, sought to minimize the present worth of revenue requirements or some
other economic or financial yardstick specific to the utility. Public awareness of
the socio-economic impact of electric power, together with new consciousness of the
environmental impact of planning choices, gave rise to a more circumspect approach
to system planning - one that optimizes the total societal cost. "Least cost
planning," as it is called, examines such issues as demand-side alternatives to
supply-side growth, affordability, value of service, etc.
Because least cost planning must compare a wide range of dissimilar alternatives,
new techniques were necessary and they have been developed.
While the issues involved in least cost planning for developing countries will be
quite different from those associated with the same process in industrialized
countries, the least cost process may be even more germane in the former. For
example, the value of electrification in building up economic infrastructure in a
developing country may actually outweigh its value as measured in revenue-
producing service.
(See also "Prioritization and Structured approaches to complex decisions)
Maintenance Policies
Maintenance policy and operator training is part and parcel of an increasingly
important tradeoff between plant design, first cost, service reliability, and
equipment life. That balance is sometimes poorly understood by those countries
least able to afford the penalties of poor balance. The objective of developing
countries should be to:
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Power Technologies, Inc.
O Stick to relatively simple, well-proven plant designs, avoidingfeatures that are poorly understood, marginally useful, or difficult tomaintain.
Equipment and software suppliers receive bid specificationsfrom developing countries which call for state-of-the-arttechnology and redundant designs where simple, lessexpensive, and more easily maintained alternatives wouldappear better suited.
o Stress the building of maintenance and operating skills and facilities,as opposed to reliance on excessive equipment redundancy.
Redundancy and automatic throw-over, often coupled witha large spare parts compliment, are often considered asubstitute for the lack of local maintenance skills. Yetcomplex plants cost more and are less reliable thansimple ones. Maintenance and operator training is a farbetter long range investment.
O Limit the number of qualified suppliers and technologies, thussimplifying maintenance and facilitating a rational spare parts policy.
Competitive considerations often result inengineer/constructors mixing equipment from an unusuallybroad spectrum of suppliers. That pressurenotwithstanding, specifications can be written to minimizethe range of technologies that need to be serviced, andthe number of spare parts that need to be maintainedlocally.
This does not necessarily mean low-technology solutions are best for developing
countries. It does suggest that technology be used much more selectively, and that
it not be considered a substitute for aggressive maintenance or operator training
programs where the latter is the real availability limitation.
Prioritization and Structured Anproaches to Comolex Decisions7 1
Engineers have long appreciated the power of eigenvalues in simplifying complex
response characteristics of electrical, mechanical, chemical, or other system. One
breaks the system into "orthogonal' (uncoupled) components, analvzes the problem
-IX-4-
Power Technologies, Inc.
one component at a time, and treats the whole problem as the sum of several
simpler ones.
The same general approach has been found useful in simplifying complex judgement
challenges that confront decision makers, for example, "Which prospective
structural alternatives is best for our national utility system?", "What mix of
generation will best satisfy the diverse pressures we're subjected to?," or "What's
the best portfolio of R&D projects considering that I can't fund all of them?" In
each such case there are "orthogonal" attributes that can simplify the comparison
and lend clarity and structure to the judgement call that must ultimately be made.
The problem is often less of evaluating individual options than comparing alternative
"portfolios." Portfolios are most commonly reviewed in terms of "balance" and
"robustness," balance measuring the degree to which a portfolio satisfies objective,
and "robustness" indicating the sensitivity of a portfolio to surprises in the
operating environment.
The process, relatively new, is essentially a disciplined way of addressing complex
alternatives or groups of alternatives and as such will be useful in many countries
and a wide variety of issues.
Privatization72 [A]
The past decade has seen more and more conversions of government-owned utilities
to private companies, either through vertically-integrated companies of regional
scope or of separate generation and distribution companies, or both.
The success of "privatization" hinges on better management and operational
efficiencies, stemming in turn, from financial incentives of private owners.
This move, while mainly seen up to now in developed countries, has also been
proposed as a means of revitalizing and de-politicizing national utilities in
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Power Technologies, Inc.
developing countries. One useful means proposed for achieving more efficient
operation is "performance contracting," a deal where private owners or operators
agree to certain economic bogeys and share in the savings achieved beyond those
norms. Performance contracting must be done with great care to assure that the
benefits are long-term.
Productivity7 3 [A]
Utilities in the U.S. and in many other countries are subject to new pressures to
improve productivity through improved methods, through automation, and through
better organization and deployment of human resources. Improvements in methods
and automation have evolved constantly and are now encouraged, in the U.S. at
least, by comparative productivity data for power plant, and line crews.
The potential for improving productivity further is apparent from the very wide
disparity in employees per installed MW among world utilities having similar systems
and internal staff scope.
A variety of approaches to human productivity have been used successfully. Most
lead to reductions in the number of management layers (vertical) and the degree of
organizational compartmentalization (horizontal). Most achieve these goals by
eliminating or farming out marginally useful or highly cyclical work, and by
increasing management spans of control, i.e. the number of direct reports.
One of the most successful and most quantitative approaches begins by building a
data base which, among other information, describing how every employee currently
spends his time. This is done by means of a "dictionary" of activities, usually
tailored to the company under study. The data base helps improve structure, improve
work flow, and allocate human resources in accordance with priorities.
To be effective, productivity improvement programs must have the support and
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Power Technologies, Inc.
participation of top management and must be sheltered from excessive political or
institutional constraints.
Strateeic Plannin&z4 [A]
No corporate or government entity can avoid the need for some form of strategic
planning. Experience with strategic planning suggests that whether strategic
planning is done by internal specialists, hired consultants, or is built into the
management function is less important than whether it:
o Is based on a clear statement of mission and objectives.
o Includes a realistic, dispassionate appraisal of the operatingenvironment, including its constraints.
o Fosters imaginative, and courageous thinking.
o Results in strategies that are straightforward and simply stated.
o Is a process rather than a document.
o Involves and has the commitment of top management.
Strategic planning is a judgement game. While software and modeling may provide
inputs, the strategic process itself cannot be "programed."
Utilities who have never done strategic planning would be well to sponsor internal
workshops on the method and, from that point forward, learn by doing the planning.
(See also "Prioritization and Structured Approaches to Complex Decisions")
-IX-7-
REFERENCES
Power Technologies, Inc.
REFERENCES
(I) "Impact of Lower Oil Prices on Renewable Energy Technologies,"Industry and Energy Department working paper. Energy Series Paper No.5. The World Bank.
(2) "Energy Issues in the Developing World," Industry and EnergyDepartment Working Paper. Energy Series Paper No. 1, The World Bank.
(3) New Electric Power Technologies, Problems and Prospects for the 1990's.(Washington, DC: Congress, Office of Technology Assessment, OTA-E-246,July, 1985
(4) "Clean Coal Technologies," Electric Power Research Institute Journal,January/February 1988, pp. 5-17.
(5) "End-Use Catalog - R&D Projects and Products," Electric Power ResearchInstitute, Palo Alto, California, September 1984.
(6) "Power Plant Instrumentation and Control: Present and Future Needs andTrends," by F.C. Olds, Power Engineering, May 1985, p. 30.
(7) "Retrofitted Microprocessor-Based Combustion Controls Provide MajorSavings," C.D. Evans, R. Zambratto, Power Engineering, January 1984, p.42.
(8) "State-of-the-Art in Non-Classical Means to Improve Power SystemsStability," CIGRE SC38-WG02, ELECTRA, May 1988, No. 118, pp. 87-113.
(9) "Diesel Plant Performance Study," Energy Department Paper 21, May 1985.The World Bank.
(10) "Technical Limitations to Transmission System Operations." ElectricPower Research Institute. 3412 Hillview Ave. Palo Alto, California 94304.
(11) "Uprating of High Pressure Gas-Filled Feeders by Fluid Filling and RapidCirculation," IEEE Conference, Anaheim, California, September 15-19, 1986(co-authors T.R. Grave and E. Kallaur).
(12) Gas Turbine World Handbook, 1986-87.
(13) Current Review of Combined Cycle Technology, D. Chase, L. Davis,Pacific Coast Electrical Association, 1986.
(14) Proceedings of the C.I.G.R.E. Symposium on "Electric Power Systems inDeveloping Countries," Dakar, November 1985.
-R-1-
Power Technologies, Inc.
(15) Ocean Energy Technologies: The State of the Art. EPRI report AP-4921.November, 1986.
(16) "A Power System Stabilizer Design Using Digital Control," by F. P. deMello, L.N. Hannett, D.W. Parkinson, J.S. Czuba, IEEE Paper 82 WM 119-6presented at the IEEE PES Winter Meeting, New York, N.Y. January 31-February 4, 1982.
(17) F.P. de Mello, L.N. Hannett, and J.M. Undrill, "Practical Approaches toSupplementary Stabilizing from Accelerating Power." IEEE Transactionson Power Apparatus and Systems, Vol. PAS-97, No.5, September/October1978, pp. 1515-1522.
(18) Steam Turbine Reference, First International Conference on ImprovedCoal-Fired Power Plants, Electric Power Research Institute, November 12-21, 1986, Palo Alto, California.
(19) "Processed Fuels and Materials Recovery," from Municipal Solid WasteSymposium, December 1986, Washington, D.C. Sponsored by ResourceRecovery Report, GBB.
(20) EPRI report EM 264, "An Assessment of Energy Storage Systems Suitablefor Use by Electric Utilities," July, 1976.
(21) "Transmission Line Reference Book 115-138 kV Compact Line Design."Electric Power Research Institute, 3412 Hillview Ave, Palo Alto, California94304
(22) I.S. Grant and J.R. Stewart, "Mechanical and Electrical Characteristics ofEHV High Phase Order Overhead Transmission", Paper 84T&D318-2,IEEE/PES 9th Transmission and Distribution Conference, Kansas City,Montana, April 29 - May 4, 1984.
(23) "Comparison of Costs and Benefits of dc and ac Tranbsmission", ORNL-6204, Oak Ridge National Laboratory, February 1987.
(24) I.S. Grant and R.E. Clayton, "Transmission Line Optimization," IFETransactions on Power Delivery, Vol. PWRD-2, No.2, April 1987.
(25) "Weather-Dependent Versus Static Thermal Line Ratings," Paper No.86T&D 503-7, presented at the IEEE T&D Conference, Anaheim, CA,September, 1986, IEEE Transactions on Power Delivery, Vol.3, No.2, April,1988, pp 754-761.
(26) G.J. Ramon, IEEE Task Force Chairman, "Dynamic Thermal Line RatingSummary and Status of the State-of-the-Art Technology," IEETransactions on Power Deliver, Vol. PWRD-2, No.3, July 1987.
(27) Shield Wire Distribution reference.
-R-2-
Power Technologies, Inc.
(28) H.B. White, "Modular Design of Guyed-V Towers," IEEE T-PAS,November/December 1978, pp. 2354-2358.
(29) "Economic Measures of Bare Overhead Conductor Characteristics," PaperNo.86 T&D 502-9, presented at the IEEE T&D Conference, Anaheim, CA,September 1986, IEEE Transactions on Power Deliverv, Vol.3, No.2, April1988, pp. 742-753.
(30) Fritz, E., "The Effect of Tighter Conductor Tensions on Transmission LineCosts," IEEE Transactions Paper, Vol. PAS-79, 1960, pp. 513-527.
(31) Transmission Line Reference Book - UHV. Ibid.
(32) U6 Cables: "Underground Power Transmission", Section of StandardHandbook for Electrical EnRineers" 11th Edition. McGraw-Hill 1987.
(33) Harvey, J.R., "Effect of Elevated Temperature Operation on the Strengthof Aluminum Conductors," IEEE/PES Paper T-72, 189-4, presented atIEEE 1971 Winter Meeting.
(34) "Power System Reliability Calculations," R. Billinton, R.J. Ringlee, and A.J.Wood, The MIT Press, 1973.
(35) Practical Applications of ANSI/IEEE Std.80- 1986, IEEE Guide for Safety,86EH0253-5-PWR, IEEE Service Center, Pisacataway, N.J. 07754-4150.
(36) "Static Compensators for Reactive Power Control," Canadian ElectricalAssociation, Cantext Publications, Winnipeg, 1984.
(37) "Circuit Breakers, Switchgear, Relays, Substations, and Fuses,"ANSI/IEEE Std. C37.
(38) "Gas-Insulated Substation Reliability: Present Status and Future Trends,"EPRI, EL-4422, February, 1986.
(39) "Metal Oxide Surge Arresters for Gas-Insulated Systems," EPRI, EL-2876,February, 1983.
(40) "IEEE Guide for Safety in Ac Substation Grounding" ANSI/IEEE Std. 80-1986.
(41) "Static Shunt Devices for Reactive Power Control," CIGRE Paper 31-08,August, 1974.
(42) "High Voltage alternating-current Circuit-Breakers," CEI/IEC standard 56,fourth edition, 1987. International Electrotechnical Commission, I Rue deVarembe, Geneva, Switzerland.
-R-3-
Power Technologies, Inc.
(43) "Insulation Coordination," IEC publication 71-1, sixth edition, 1976."Static VAR Compensators," CIGRE Working Group 38-01, Task Force No.2on SVC, 1986.
(44) "Energy Control Center Design", IEEE Tutorial Course, 77 TUOOIO-9-PWR.
(45) "The New Energy Management System at PSE&G," by J.N. Wrubel and R.Hoffman, presented at the IEEE 1987 Power Industry ComputerApplication Conference, PICA 87, Montreal, Canada, May 18-22, 1987.
(46) "A Practical and Cost Effective Approach to a Dispatcher TrainingSimulator", by S.A. Ibrahim Lashin, E.R. Lybrand,, Henri Dale, presentedat the IEEE 1987 Power Industry Computer Application Conference, PICA87, Montreal, Canada, May 18-22, 1987.
(47) "Wheeling Rates Based on Marginal-Cost Theory" by Hyde M. Merrill andBruce W. Erickson. IEEE transactions paper submitted for the IEEEWinter Power Meeting to be held in 1989.
(48) "Guidelines for Evaluation Distribution Automation," General ElectricCompany, EPRI EL-3728, Project 2021-1, Final Report, November 1984.
(49) "Cost/Benefit Analysis of Distribution Automation," presented at theAmerican Power Conference, Chicago, IL, April, 1987.
(50) "Higher Distribution Voltages ... Not Always a Panacea." Electrical World- April 1988.
(51) "Are URD Overvoltage Margins Inadequate." Electrical World. [NEEDDATEI
(52) "Surge Protection of Underground Systems up to 34.5 kV," by J.J. Burke,N.R. Schultz, E.G. Sakshaug and N.M. Neagle. Presented at UndergroundConference in Atlantic City, NJ., September 1976.
(53) "Compensation Techniques to Increase Electrified RailroadPerformance," IAS, Norfolk, VA, April, 1986.
(54) "An Analysis of Distribution Feeder Faults," Electric Forum Magazine,December 1976 (co-authored by J.J. Burke and D.J. Ward.
(55) "Utility Operation and Its Effect on Power Quality," by James J. Burke.Tutorial paper presented at the 1988 Winter Power Meeting of theInstitute of Electrical and Electronic Engineers.
Copies available from Power Technologies, Inc.
-R-4-
Power Technologies, Inc.
(56) "Summary of JICABLE '84 - International Conference on Polymer-InsulatedPower Cables, by L. Deschamps, Electricit6 de France, Clamart, France.IEEE Transactions on Electrical Insulation Vol. EI-21. No.l. February.1986
(57) "Advanced Analytical Tools in Evaluating Power System Dynamic andSecurity Performance Results of a Questionnaire," CIGRE SC38-WG02,ELECTRA, March 1988, No. 117, pp. 35-54.
(58) "IEEE Guide for Harmonic Control and Reactive Compensation of StaticPower Converters," IEEE Std. 519-1981. Under revision as "IEEERecommended Practices and Requirements for Harmonic Control inElectric Power Systems," (expected to be submitted to IEEE StandardsBoard in 1988.)
(59) "Review of Load Flow Calculation Methods," B. Stott, Proceedings of theIEEE, July 1974, pp. 916-929.
(60) "Power System Planning Technique," W.R. Puntel, H.M. Merrill, M.A.Sager, A.J. Wood, Course Notes, Power Technologies, Inc., Schenectady,New York, 1984.
(61) Power Generation. ODeration. and Control, A.J. Wood and B.F. Wollenberg,John Wiley & Sons, New York, 1983.
(62) "Simplified Transmission and Generation System Analysis Procedures forSubsynchronous Resonance Problems. Kilgore, L.A., +, T-PASNovember/December 1977, pp.1840-1846.
(63) "Subsynchronous Resonance Between Rotating Machines and PowerSystems. IEEE Power Engineering Society, Power System Eng. Ctte.,Subsynchronous Resonance Task Force, +, T-PAS January/February 1976,pp. 216-218.
(64) "Subsynchronous Resonance Between Rotating Machines and PowerSystems. IEEE Power Engineering Society, Power System Eng. Ctte.,Dynamic Performance Working Group, T-PAS November/December 1979,pp. 1872-1875.
(65) Power System Harmonics, J. Arrillaga, D.A. Bradeley, and P.S. Bodger,John Wiley & Sons, New York, 1985.
(66) "Quick Spreadsheet Corporate Models for Strategic Planning," by J.W.Feltes and H.M. Merrill, IEEE Transactions on Power Systems, Vol. PWRS-1, No. 3, August 1986.
(67) Special issue on electric utility deregulation, Public Utilities Fortnightlv,Vol. 110, No. 6, September 16, 1982.
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Power Technologies, Inc.
(68) Enersv in a Finite World: Executive Summary, by Alan McDonald. Reportby the Energy Systems Program Group of the International Institute forApplied Systems Analysis, Wolf Hafele, Program Leader. Executive Report4, May 1981, Revised October 1981. IIASA, A-2361 Laxenburg, Austria.
(69) What is Least Cost Planning?" by W. J. Burke and Walter R. Puntel,"Power Technolorv" (Commercial Newsletter) Issue No. 49, April 1987.
(70) "Least-Cost Planning: Issues and Methods," F.C. Schweppe, H.M. Merrill,and W.J. Burke, to appear, Proceedings of the IEEE, 1988.
(71) "Trade Off Methods in System Planning," by H.M. Merrill et al, presentedat IEEE PES Summer Power Meeting, San Francisco, California, July 1987.
(72) "Improving Power System Efficiency in the Developing Countries ThroughPerformance Contracting," Industry and Energy Department WorkingPaper. Energy series paper No. 4. May, 1988. The World Bank.
(73) "Organizing the Utility for Increased Productivity," by Lionel 0. Barthold.Transmission & Distribution, December 1987.
(74) "Strategic Planning for Electric Utilities: Problems and Analytic Methods,"H.M. Merrill and F.C. Schweppe, Interfaces, Vol 14, No.1, January &February 1984, pp. 72-83. Also published in Readints on StrateaicManarement (editor: A.C. Hax), Bellinger Publishing Co., Cam,bridge, MA,1984.
(75) "Fibre Optics, Technology and Applications in Power Industry", CIGRESC35, ELECTRA July 1986, No. 107, pp. 8-51.
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ENERGY SERIES PAPERS
No. 1 Energy Issues in the Developing World, February 1988.
No. 2 Review of World Bank Lending for Electric Power, March 1988.
No. 3 Some Considerations in Collecting Data on Household EnergyConsumption, March 1988.
No. 4 Improving Power System Efficiency in the Developing Countriesthrough Performance Contracting, May 1988.
No. 5 Impact of Lower Oil Prices on Renewable Energy Technologies, May1988.
No. 6 A Comparison of Lamps for Domestic Lighting in Developing Countries,June 1988.
No. 7 Recent World Bank Activities in Energy (Revised September 1988).
No. 8 A Visual Overview of the World Oil Markets, July 1988.
No. 9 Current International Gas Trades and Prices, November 1988.
No. 10 Promoting Investment for Natural Gas Exploration and Production inDeveloping Countries, January 1989.
No. 11 Technology Survey on Electric Power Systems, February 1989.
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