ntpc anta report

8/11/2019 NTPC ANTA REPORT

http://slidepdf.com/reader/full/ntpc-anta-report 1/52

1

CONTENTS:-

Title Page no.

Abstract

Chapter 1

1)Introduction of NTPC 3

1.1)Overview 3

1.2)Company profile 3-6

1.3)organization and hierarchy 6-7

1.4)Mission and vision 7

1.5)Core value of NTPC 10

1.6)Power scenario in India 10-11

1.7)Aims and objective 12

Chapter 2

2)Economy of power generation

2.1)Introduction 13-17

2.2)Selection of type of generation 17

2.3)Cost of generation 18-19

3)Power generation process

3.1)Principle operation process 20

3.2)Silent feature of gas and steam turbine 21

3.3)Equipment of power plant 22-29

Chapter 3

4)Introduction of 220kv switchyard 29-33

5)Equipment in switchyard 33-51



2

Appendix A

Conclusion 50

References 51



3

INTRODUCTION

Nranking of the World’ s biggest companies. NTPC became a Maharatna company in

May, 2010, one of the only four companies to be awarded this status. It received

International Project Management Association (IPMA) award in 2005 for excellence

in project management for its Simahadri Project and in 2008 its Vindhyachal Project

received Silver medal from IPMA. NTPC is the largest power generation in the

country with an installed capacity of 34,854 MW (including Joint Ventures). Today,

NTPC with an installed c apacity of about 18% of country’ s total capacity is

contributing about 28% of the electricity generated, which depicts the high level of

operational performance, that are comparable with any of the global power utilities.NTPC has adopted a vision - “To be the world’ s largest and best power producer,

powering India’s growth”. NTPC has plans to have an installed capacity of 75 GW by

2017 reaching to 128GW by 2032. Capacity of over 7000 MW unit is already under

construction and another over 7000 MW under request by NTPC under its portfolio.

1.1.2. NTPC Installed Capacity

NTPC installed capacity region wise is mentioned below in the table:

REGI ON COAL GAS TOTAL

Northern 8,015 2,312 10,327

Western 6,860 1,293 8,153

Southern 4,100 350 4,450

Eastern 7,900 - 7,900

JVs 1,424 1,940 3,364

TOTAL 28,299 5,895 34,194

Table 1.1 Total i nstalled capacity of NTPC

1.2. Company Profile

Organizational Environment : -

National Thermal Power Corporation Ltd. (NTPC) was incorporated in 1975 by an

Act of parliament, to supplement the efforts of the states for quicker and greater

capacity addition in



4

Thermal power generation. In 1997, the Department of Public Enterprises,

Government of India granted, Navratna (Nine Jewels) status with powers of

operational autonomy to the board of NTPC with an objective to turn the public sector

enterprise into a global giant. This has helped NTPC in speedy implementation of

power projects, adoption of new technologies and formation of Joint Ventures in the

core generation as well as service businesses.

Recently NTPC has bee n awarded the “MAHARATNA” status which has given it

greater autonomy. In line with its vision and mission statement over the last thirty five

years NTPC has grown to become the largest power utility in India with a

commissioned generation capacity of 31,704 MW (as on 31.03.2010) with power

stations spread over the length and breadth of the country, covering portfolios in coal

based and combined cycle power plants Besides, being India’s largest power

generation utility, NTPC has also grown to become the number one independent

power producer in Asia and second globally in 2009 (by Platts, a division of

McGraw-Hill companies), 5th largest company in Asia and 317th Largest company in

the world (FORBES ranking – 2009) with Net Sales of Rs. 46,504.47 crore during

2009-10.

NTPC has also the honor of becoming the 6th largest thermal power generator in the

world and second most efficient in terms of capacity utilization amongst top 10

utilities in the world. NTPC has been re- christened as “NTPC Limited” since 7th

Nov. 05.

Today NTPC is more than a company. It is an institution, which has moulded the

economy of India setting many landmarks particularly in power plant engineering,

operation and maintenance, contract management that other power organisations

would strive to emulate.

Investor’s ProfileTo augment capital outlay, NTPC made an Initial Public Offer (IPO) in Oct. 2004

and subsequent Further Public Offer (FPO) in Feb 2010. With this disinvestment, the

ownership of GOI has reduced to 84.5%.Presently NTPC is one of the three largest

Indian companies in terms of market cap.

1.2.1. NTPC Anta

1 Approved capacity 413 MW

2 Location Baran, Rajasthan3 Gas Source HBJ Pipeline- South Basin



5

Gas Field

4 Beneficiary States

Uttar Pradesh,Jammu &

Kashmir,

Chandigarh, Rajasthan,

Haryana, Punjab,

Himachal Pradesh, Delhi

& Uttaranchal

5 Approved Investment Rs. 418.97 Crore

6 Unit Sizes 3X88.71 GT + 1X153.2 ST

7 Unit Commissioned

Unit - I 88 MW GT January

1989

Unit - II 88 MW GT March

1989

Unit - III 88 MW GT May

1989

Unit - IV 149 MW ST March

1990

8 International Assistance IBJ and World Bank

9 Water Source Anta Kota Right Main Canal

Table 1.2 Detail s of NTPC Power Pl ant at Anta

1.2.2. Site Approach

The plant site is 2 KM form Anta Railway Station which is about 50 KMs from Kota.

The installed capacity of the plant is 419.33 MW. It consists of three gas turbines of

ABB make type 13D-2 of 88.71 MW capacity and one steam turbine of 153.2 MW

capacity. The three numbers of WHRBs are unfired boilers supplied by WAAGNER-

BIRO. The WHRB (Waste Heat Recovery Boiler) have horizontally arranged finned

tubes with separate high and low pressure systems and condensate preheating, forced

circulation.

The main fuel for the plant is Lean Natural Gas and alternative fuel is Naphtha. GAIL

supplies the Natural gas for the plant from HBJ pipeline through a branch line and

GAIL and oil majors IOCL, BPCL& HPCL as per requirement, supply naphtha. The

circulating water requirement for condenser cooling is met by taking water from the

Kota Right Main Canal (RMC), through CW intake channel. Kota RMC is an



6

irrigation canal and its opening depends upon irrigation requirements. During open

cycle operation of CW system, the water is passed through condenser and flows back

to RMC. During the closed cycle operation the water is drawn from Raw Water

Reservoir for make up by two numbers of CW system is supplied from the same.

F igur e 1.1: View of M ain Plant

Employee Profile:

The employee strength of ANTA is 221 as on May 2010. Power generation being

highly technology intensive, most of the employees are Engineers and technicians.

Executives are from professional background, supervisors and workmen are from

technical / graduate background. Contract workforce (average150 nos.) is also

engaged for Skilled/ semi – skilled/un-skilled jobs. The employee is organized into

Executive Association, Supervisors Association and Workers Union.

Democratically elected representatives manage association and unions.

1.3. Organization and Hierarchy

1.3.1. Organization Chart – NTPC Anta

NTPC s current 3 -tier structure comprises Corporate Centre (CMD, Board ofdirectors & corporate functions), Regional Headquarters (five in numbers – NCR, NR,

SR, ER and WR) and stations/Projects, ANTA being one of the stations. Anta falls



7

under NCRHQ. The business unit head of ANTA is the General Manager (GM). The

power generation is handled by Operations and Maintenance department headed by

AGM (O&M), reporting to GM. O&M consists of different sections viz. Operations,

Mechanical Maintenance, Electrical Maintenance, C&I maintenance, Chemistry,

EEMG, MTP , each subsection is headed by a DGM/ Senior Manager. The support

function Departments are F&A, HR, Contracts.

1.4. Mission and Vision of NTPC

NTPC s vision and mission are driving force in all our endeavors to ultimately

produce and deliver quality power in optimum cost and eco-friendly manner through

concerted team efforts and effective systems. Being a PSU, Anta has derived its

mission and vision aligning with that of the Corporate Mission and Vision.

VISION: “A world class integrated power major, powering India’ s growth, with

increasin g global presence.”

MISSION : “Develop and provide reliable power, related products and services at

competitive prices, integrating multiple energy sources with innovative and eco-

friendly technologies and contribute to society.”

1.5. Core Values of NTPC

The Core Values (BCOMIT), as of NTPC epitomizes the organizational culture and is

central to every activity of the company. The values create involvement of all sections

of the employees. The core values are widely communicated for the actualization

among the employees.

Business Ethics

Customer Focus

Organizational and Professional Pride

Mutual Respect and Trust

Innovation and Speed

Total Quality for Excellence



8

1.6. Power Scenario in India

1.6.1. India’s Installed Capacity

In India Electricity are generated state level, central level and private. Overallinstalled capacity in these sectors is as on 30.04.2011.

SECTOR MW %

States 82452.58 47.29

Central 54412.63 31.21

Private 37496.19 21.5

Total 174361.4 100

Table 1.3 I nstalled Capacit ies by Di ff er ent Sectors



9

The total installed capacity by fuel is mentioned in the table :

FUEL M W %

Coal 94,653.38 54.29

Gas 17,706.35 10.15

Oil 1,199.75 0.69

Total Thermal 1,13,559.48 65.13

Hydro 37,567.40 21.25

Nuclear 4,780 2.74

Renewable 18,454.52 10.58

Total 1,74,361.40 100

Table 1.4 Total I nstalled Capacity by F uel



10



11

F igur e 1.2: India’ s I nstalled Capacity F uel Wi se

1.6.2. Consumption of Electricity in India

Day by day the consumption of electricity is increasing and it assumed that on 2012

consumption will be 1000 KWh per annum.

YEAR PER CAPIT A CONSUM PTI ON

1950 15 KWh/per year

2007 672 KWh/per year

2012- Target 1000 KWh/per year

Table 1.5: Per Capita Consumption

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

THERMAL NUCLEAR HYDRO RES TOTAL CAPTIVE

112824

4780

37567

18455

174361

19509

INDIA'S INSTALLED CAPACITY FUEL WISE



12

1.7. Aims & Objectives

The National Electricity Policy aims at achieving the following objectives:

Access to Electricity - Available for all households in next five years

Availability of Power - Demand to be fully met by 2012. Energy and peakingshortages to be overcome and adequate spinning reserve to be available.

Supply of Reliable and Quality Power of specified standards in an efficient

manner and at reasonable rates.

Per capita availability of electricity to be increased to over 1000 units by 2012.

Minimum lifeline consumption of 1 unit/household/day as a merit good by year

2012.

Financial Turnaround and Commercial Viability of Electricity Sector.

Protection of con sumer’s interests.



13

CHAPTER 2

2. ECONOMICS OF POWER GENERATION

2.1. Introduction

The function of a power station is to deliver power at the lowest possible cost per kilo

watt hour. This total cost is made up of fixed charges consisting of interest on the

capital, taxes, insurance, depreciation and salary of managerial staff, the operating

expenses such as cost of fuels, water, oil, labor, repairs and maintenance etc.

The cost of power generation can be minimized by:

1. Choosing equipment that is available for operation during the largest possible % of

time in a year.

2. Reducing the amount of investment in the plant.3. Operation through fewer men.

4. Having uniform design

5. Selecting the station as to reduce cost of fuel, labor etc.

All the electrical energy generated in a power station must be consumed immediately

as it cannot be stored. So the electrical energy generated in a power station must be

regulated according to the demand. The demand of electrical energy or load will also

vary with the time and a power station must be capable of meeting the maximum loadat any time. Certain definitions related to power station practice are given below:

Load Curve:

Load curve is plot of load in kilowatts versus time usually for a day or a year.

Load Duration Curve:

Load duration curve is the plot of load in kilowatts versus time duration for which it

occurs.

Maximum Demand:

Maximum demand is the greatest of all demands which have occurred during a given

period of time.

Average Load:

Average load is the average load on the power station in a given period (day/month or

year)

Base Load:

Base load is the minimum load over a given period of time.



14

Connected Load:

Connected load of a system is the sum of the continuous ratings of the load

consuming apparatus connected to the system.

Peak load:

Peak load is the maximum load consumed or produced by a unit or group of units in a

stated period of time. It may be the maximum instantaneous load or the maximum

average load over a designated interval of time.

Demand Factor:

Demand factor is the ratio of maximum demand to the connected load of a consumer.

Diversity Factor:

Diversity factor is the ratio of sum of individual maximum demands to the combined

maximum demand on power stations.

Load Factor:

Load factor is the ratio of average load during a specified period to the maximum load

occurring during the period.

Load factor = Average Load / Maximum demand

Station Load Factor:

Station load factor is the ratio of net power generated to the net maximum demand on

a power station.

Plant Factor:

Plant factor is the ratio of the average load on the plant for the period of time

considered, to the aggregate rating of the generating equipment installed in the plant.

Capacity Factor:

Capacity factor is the ratio of the average load on the machine for a period of time

considered, to the rating of the machine.

Demand Factor:Demand factor is the ratio of maximum demand of system or part of system, to the

total connected load of the system, or part of system, under consideration.

Utilization Factor:

Utilization factor is the ratio of maximum demand of a system or part of the system,

to the rated capacity of the system, or part of the system, under consideration.

Firm Power:

Firm power is the power intended always to be available even under emergencyconditions.



15

Prime Power:

Prime power is the maximum potential power constantly available for transformation

into electrical power.

Cold Reserve :

Cold reserve is the reserve generating capacity that is available for service but not in

operation.

Hot Reserve:

Hot reverse is the reserve generating capacity that is in operation but not in service.

F igur e 2.1 Monopoly M odel

Spinning Reserve:

Spinning reserve is the reserve generating capacity that is connected to the bus and

ready to take load.

Run of River Station:Run of river station is a hydro-electric station that utilizes the stream flow without

water storage.

Base Load Supply:

In inter connected systems with many generating stations of various types; the choice

of station to supply the varying load is of considerable economic significance. Entire

load of the system may be divided into two parts e.g., base load and peak load. Base

load is the load which is supplied for most of the time which remains more or lessconstant. Peak load is the intermittent requirement at particular hours of the day and

so on.



16

The main considerations for base load provision are:

(i) High efficiency

(ii) High availability of the system.

Even a higher capital cost is sometime favoured if it can ensure resultant gain in

efficiency, as the cost is spread over a large total energy value.

Nuclear power plants are invariably used as base load plants. Thermal power plants

and hydroelectric power plants can also be used as base load plants.

As far as peak load plants are concerned, these plants should have:

(i) Ability to start and take full load with a short time

(ii) Low capacity cost in view of the small annual output with the efficiency only a

secondary condition.

Obsolete steam plant, through less efficient can't be used to met with peak load

demand. Gas turbines, diesel engine plant and pumped storage stations are also

suitable for peak load operation.

Peak Load:

Load on a power plant seldom remain constant. The load varies from season to season

and also in a day from hour to hour. In summer, due to fans and air conditioners the

plants have generally high load as compared to winter months. During day time also

lights are switched on in the evening, the load on the plant will increase. During the

days of festivals like national festivals, national days etc., there is excessive demand

of electrical power. A power generating plant has to meet with all such variable

demand sand at the same time maintain overall economy of operation. The period

during which the demand on a power station is highest is known as peak load. Peak

load on a plant may exist for small duration but still the plant has to devise ways and

means for meeting with such demands.

Some of the methods are given below to meet with peak load demand:1. Peak Load Plants:

Such plants arc operated only during peak load periods. These plants must be capable

of quickly starting from cold conditions. Diesel engine plants, gas turbine plants,

pumped storage plant and sometimes steam power plants and hydroelectric plants are

used as peak load plants. Efficiency of such plants is of secondary importance as these

operate for limited period only.



17

2. Use of Accumulators:

Although electrical energy cannot be stored, however steam can be stored in steam

accumulators, which can be used to generate additional power during peak load

period.

3. Purchasing Power:

When a power plant cannot generate sufficient power to meet with the demand, it may

purchase power from neighboring plants if facilities exist.

4. Load Shedding:

When there is no alternative available the supply to some consumers is cut off

temporarily, which is known as load shedding. Sometimes load shedding is done by

switching off feeders by rotation or by reducing system voltage or by reducing

frequency.

2.2. Selection Of Type Of Generation

2.2.1. Cost of Electrical Energy

Capital cost of a power plant is due to

1. Cost of land and buildings

2. Cost of generating equipment and accessories

3. Cost of transmission and distribution network

4. Cost of designing and planning the power station

In general following plants are preferred for base load operations:

1. Nuclear power plant

2. Hydro electric plant

3. Steam power plant

Following points are preferred for peak load operations:

1. Diesel engine power plant.

2. Gas turbine power plant

3. Pumped storage plant.

2.3. Cost of Generation

The cost of generating electricity in a power plant can be conveniently split into two

parts: fixed costs and variable costs.



18

(A) Fixed Cost:

Fixed costs are to be borne by the plants irrespective of the load. These costs consists

of following:

(i) Interest on Capital:

Capital cost of a plant includes the cost of land, buildings, of equipment including

installation, designing, engineering etc. Since the capital cost of a plant is fixed

therefore interest on the amount is considered as fixed cost.

(ii) Taxes:

A power generating and distributing company has to pay taxes to the Government;

this amount is more or less fixed.

(iii) Cost of Transmission and Distribution:

Power transmission and. distribution network involves huge capital expenditure. This

involves cost of transmission lines, transformers, substations and associated

equipment. Interest on the capital involved is considered as a fixed cost.

(iv) Depreciation:

It is decrease in value caused by the wear due to constant use of equipment under the

Income tax laws there is provision for setting aside a fixed proportion of the capital

employed, towards the depreciation fund.

(v) Insurance:

The plant and also life of some of workers working in dangerous areas, has to be

insured against various risks involved. For this purpose a fixed sum is payable as

premium for the insurance cover.

(vi) Salary for Managerial Staff:

Irrespective of whether the plant works or not certain managerial staffs has to be

retained by the organization. The salary liability of such staff is a part of the fixed

cost.(B) Variable Cost:

These costs vary in some proportion of the power generated in a plant. These costs

consist of-

(i) Cost of Fuel:

Cost of fuel is directly related with the amount of power generated. For generating

more power, more fuel is required. Cost of fuel may be 10% to 25% of the total cost

of production. In case of hydroelectric plants the cost of fuel is zero.



19

(ii) Maintenance and Repair Charges:

In order to keep the plant in running condition, certain repairs are always needed.

Stock of some consumable and non- consumable items has got to be maintained. All

chargers for such staff are considered as operating costs.

(iii) Wages:

Salaries including allowances bonus, benefits etc. for the workers are considered as

operating costs. Total cost of production is thus sum of the fixed charges and the

operating charges. As the plant load factor improves, the cost per kWh decreases. The

sum of the charges for various factors will give an optimum load factor where such

charges will be least.

2.4. Tariff

A tariff is the rate of charge per kilowatt hour of energy supplied to a consumer. The

cost of generation of electrical energy may be conveniently split into two parts e.g.

fixed charges plus the operating charges. So a tariff should be adjusted in such a way

that the total receipts balance the total expenditure involved in generating the energy.

There are several solutions to this problem, some of which are given below:

1. Uniform Rate Tariff:

In this case there is a fixed rate per unit amount of energy consumed. The

consumption of energy is measured by the energy meter installed at the premises of

the consumer. This type of tariff accounts for all the costs involved in the generation

of power. This is the simplest tariff easily understood by consumers. However, this

type of tariff does not distinguish between small power domestic consumer and bulk

power industrial consumers.

2. Two Part Tariff:

In this the total charges are split into two parts - fixed charges based on maximum

demand (in kW) plus the charges based on energy consumption (in kWh). Thismethod suffers from the drawback that an additional provision is to be incorporated

for the measurement of maximum demand. Under such tariff, the consumers having

'peaked' demand for short duration are discouraged.

3. Block Rate Tariff:

In this the fixed charges are merged into the unit charges for one or two blocks of

consumption, all units in excess being charged at low or high unit rate. Lower rates

for higher blocks are fixed in order to encourage the consumers for more and moreconsumptions. This is done in case the plant has got larger spare capacity. Wherever



20

the plant capacity is inadequate, higher blocks are charged at higher rate in order to

discourage the consumers for higher than minimum consumption.

4. Three Part Tariff:

It is an extension of the two part tariff in that it adds to the consumer some fixed

charges irrespective of the energy consumption or maximum demand. In this ever if

the consumer has got zero power consumption, he has to pay some charges merely

because a connection has been provided to him.

5. Power Factor Tariff:

In ac power supply size of the plant is determined by the kVA rating. In case the

power factor of a consumer installation is low, the energy consumption in terms of

kW will be low. In order to discharge such consumers, power factor tariff is

introduced, which may be of the following types.

(a) Maximum kVA demand Tariff: In this instead of kW the kVA consumption is

measured and the charge are Based partly or fully on this demand.

(b) Sliding Scale: In this case the average power is fixed say at 0.8 lagging. Now if

the power factor of a consumer falls below by 0.01 or multiples thereof, some

additional charges are imposed. A discount may be allowed in case the power factor is

above 0.8. The depreciation on the plant is charged by any of the following methods:

1. Straight Line method

2. Sinking fund method

3. Diminishing value method.

.



21

CHAPTER3

3. POWER GENERATION PROCESS

3.1. Principle of Operation of Combined Gas and Steam Plant

The process of generation of power at ANTA is briefed. The Gas/Naphtha from

pipeline is taken and supplied to GT Combustion Chamber where it is burnt as fuel

along with air drawn from atmosphere. This heat is then converted into mechanical

energy in the Gas Turbine. Gas turbine through a common shaft rotates a Generator,

which produces electric power.

Flue gas from the turbine exhaust is used to convert water into steam in the Waste

Heat Recovery Boiler or HRSG. Water required for steam generation is circulated

through the tubes in the boiler, where heat exchange takes place and water gets

converted into

steam. The steam generated from WHRBs is used to run a steam turbo generator &

produce electric power. This power is supplied to customer through 220 KV lines.

3.2. Salient Features

Gas Tur bine 88 MW, TYPE ABB Gas Turbine, 5 StagesGT Compressor 18 STAGE Axial Flow (TYPE VA 140 18)

Combustion Chamber Single Silo Type

Burner Single Stage Dual Fired

Air I ntake F il ter T ype Self Cleaning Tenekay Cartridges

Bypass Stack Vertical 25M High

WHRB Double Drum, Unifired, Assisted

Circulation TypeWH RB Steam Parameter s Pressur

e

Flow Temperature

HP 62.7 BAR 163 T/HR 485 ° C

LP 5.5 BAR 39.1 T/HR 207 ° C

Steam Turbin e 149 MW, Tandem Compounded Double

Exhaust, Condensing Type, Single Flow

Horizontal 25 Stage HP Turbine and 2X6Stage LP Turbine



22

Condenser 2 Pass Surface Condenser with Stainless

Steel Tubes, Total Cooling Area 13988

M2

Cooling System for Condenser Open Cycle/Closed Cycle

Cooling Tower Type Induced Draft Cells

Cooli ng Water Pump 3X50% 15330 M3/HR each at 11.5 MWC

Range of Cooling 10 ° C

DM Water Plant 2 Streams each of 100% capacity to cater

to all 3 Boilers

Net Plant Output (STAGE-I ) 413 MW

Table 3.1: Sali ent F eatur es of Gas Tu rbin e

F igur e 3.1: Gas Tur bine at Anta

3.3. Generation Process

In Combined Cycle Gas Plant integrate two power conversion cycles, which are:1. Gas Turbine Plant (Bratyon Cycle) – Efficiency 34%

2. Steam Plant (Rankine Cycle) – Efficiency 35%



23

3.Overall combined cycle plant efficiency is 49%.

3.4. Gas Turbine Plant

Gas turbine plants can use a variety of fuels – solid, liquid and gas. Natural gas which

has 80 % methane and small fractions of other gases is very widely used in plants

situated near 19

the gas fields. This is especially so for the plants used for auxiliary power generation

in oil fields. Present day gas turbine plants generally use natural gas and liquid

petroleum fuels.

F igur e 3.2 L ayout of Gas Tu rbine Plant

3.4.1. Gas Turbine Plant Equipments

1. Air-intake system2. Compressor

3.Combustion Chamber



24

4. Gas Turbine

5. Gas Generator

3.4.2. Working of gas Turbine Plant Equipments

Air Intake System:

Compressor:

There are two types of compressors, the axial-flow compressor and the centrifugal –

or radial-flow compressor. Most power plant compressors are axial-flow compressors.

The object of a good compressor design is to obtain the most air through a given

diameter.

The compressor is made up of rotating blades on discs and stationary vanes that direct

the air to the next row of blades. The first stage compressor rotor blades accelerate the

air towards their trailing edges and towards the first stage vanes. The first stage vanes

slow the air down and direct it towards the second stage compressor rotor blades, and

so on through the compressor rotor stages (each stage is one rotating stage and one

stationary stage). The compressed air temperature is 1005 degree C.

Combustion Chamber:

Combustion is the chemical combination of a substance with certain elements, usually

oxygen, accompanied by the production of a high temperature or transfer of heat. The

function of the combustion chamber is to accept the air from the compressor and to

deliver it to the turbine at the required temperature, ideally with no loss of pressure.

Essentially, it is a direct-fired air heater in which fuel is burned with less than one-

third of the air after which the combustion products are then mixed with the remaining

air.

Gas Turbine (Brayton Cycle):

The Brayton cycle is used for gas turbines only where both the compression andexpansion processes take place in rotating machinery. The two major application

areas of gas-turbine engines are aircraft propulsion and electric power generation.

Gas turbines are used as stationary power plants to generate electricity as stand-alone

units or in conjunction with steam power plants on the high-temperature side. In these

plants, the exhaust gases serve as a heat source for the steam. Steam power plants are

considered external-combustion engines, in which the combustion takes place outside

the engine. The thermal energy released during this process is then transferred to thesteam as heat.



25

Gas Generator

Gas generator’ s shaft is connected with gas turbine’ s shaft, by rotation of turbine

generator’ s shaft rotates and then energy is generated and fed to switchyard through

power transformer.

Exhaust Module

The gas turbine’ s hot gases exit via the exhaust section or module. Structurally, this

section supports the power turbine and rear end of the rotor shaft. The exhaust case

typically has an inner and outer housing. Hollow struts locate its position. The inner

housing typically has a cone shape or cover that encloses a chamber for cooling the

thrust bearing at the end of the shaft.

3.4.3 Other Gas Turbine System

Cooling System

Air for cooling the hot sections of the turbine are drawn (bleed air) from various

stages in the compressor. Mostly air is used for cooling, even if they have a combined

cycle operation.

Bearing and Lubrication System

Basically, sleeve bearings locate the turbine modules concentrically around the

shaft(s) during operation and when the turbine is not running, they provide the rotor

with support. The thrust developed by the overall rotor is absorbed by thrust bearings

at the end of the rotor. Oil flow to the bearings is regulated. The bearings in the hot

section require far more oil flow than those in the cooler compressor section.

Thermocouples or RTDs measure oil flow temperature. Sudden temperature rises in

the oil trigger an alarm or shutdown.

3.4.4. Gas Plant Silent Features

Make ABB-1

Type 13D2

On N atural Gas Output is 89.25 MW

On Naphtha Output is 86.03 MW

Gas Turbin e Type TA140 05

No. of stages 5Di rection of rotation seen i n di rection of Clockwise



26

gas fl ow

Speed 3000 RPM

Gas inl et temperatur e 1005 ° C

Combustion Chamber Pressur e 11.6 Bar

Table 3.2: Detail of Gas Plan t

3.5. Steam Plant

3.5.1. Principle of Steam Plant

The hot exhaust gas exits from gas turbine and then passes through the Waste Heat

Recovery Boiler (WHRB). WHRB filled with high purity water. The hot exhausted

gas coming from the turbines passes through these tube bundles, which act like a

radiator, boiling the water inside the tubes and turning that water into steam. The

steam is fed to the turbine and energy is generated to supply.

F igu re 3.3 Waste Heat Recovery Boi ler

3.5.2 Steam Turbine (Rankine Cycle)

Process 1-2: Water from the condenser at low pressure is pumped into the boiler at high

pressure. This process is reversible adiabatic.

Process 2-3: Water is converted into steam at constant pressure by the addition of heat in the

boiler.Process 3-4: Reversible adiabatic expansion of steam in the steam turbine.

Process 4-1: Steam is condensate into water and feed to the boiler



27

3.5.3 Waste Heat Recovery Boiler

Anta combined cycle power plant also known as Waste Heat Recovery Boiler (WHRB) plant,

which are of non-fired, dual pressure and forced circulation type. The boiler has two different

water/steam cycles known as high-pressure system and low pressure system.

Components of WHRB

The main components of WHRB can be divided into following categories:

LP Economizer

LP Drum and Evaporator

LP Super-heater

HP Economizer

HP Drum and Evaporator

HP Super-heater

LP Economizer

In economizer the flue gas heats up the feed water. After the economizer the feed water

enters the LP evaporators and then to LP drum boiler.

LP Super-Heater

The steam, leaving at the top of the LP Drum is heated by flue gas in super heater where it

reaches the end temperature about 220 degree C.

HP Economizer

The HP economizer coils are in two parts is just below the LP economizer and other part is

below LP super-heater and both the coils are connected in series.

HP Boiler Drum and Evaporator

The feed water in the HP boiler is pumped through the evaporator by means of 2x100% HP

circulation pumps.HP Super-Heater

The HP super heater consists of two parts with a spry attemperators them. This configuration

allows the temperature control of the superheated steam.

Condensate Pre-Heater

The main condensate is pumped by condensate extraction pumps (CEPs) to feed the water

tank. Before entering the feed tank the condensate is passed through the condensate pre-

heaters, which are situated at the tail end of the WHRBs and heated by the flue gas to achievethe highest cycle efficiency.



28

TURBO GENERATORS

The Anta GPP consists of one module consisting of three gas turbine generators and one

steam turbine generator. Each turbo generator unit is a three phases, two pole cylindrical rotor

type machine directly connected to the steam / gas turbine, rotating at 3000 rpm. Generators

have the following main technical parameters.

Gas turbine generators Steam turbine generators

Rated output 97.5 MVA 191.5 MVA

Rated voltage 10.5 KV 15.75 KV

Rated power factor 0.8 0.8

Rated frequency 50 Hz 50 Hz

The machine is capable of delivering continuously its output within a voltage variation of

±5% and frequency variation of +3% to -5%. Generator is of Horizontal shaft air cooled type.

Air flows in a closed circuit and is cooled by air to water heat exchangers.

Waste heat recovery boil er

EMERGENCY DIESEL GENERATOR SET:

ENGINE

Number of cylinder : 12

Cylinder configuration : Vee-Form

Operating process : Four stroke

Combustion Process : Direct Injection



29

Exhaust turbo charging : Yes

Cylinder size : Dia. 240 mm x L 280 mm

Standard Output : 2400 KW

Rated speed : 1000 RPM

Compression Ratio : 11.59 mm

Fuel consumption at full load : 210 g/KWh

Requirement of Air Intake : 17100 M3/Hr

GENERATOR

Output capacity : 2875 KVA

Nominal Voltage : 6600 Volt

Nominal Current : 263 Amp.

Nominal excitation current : 80 Amp.

Nominal excitation voltage : 100 V

Cooling air requirement : 21.3 M3/H



30

CHAPTER 4

4. INTRODUCTION TO 220KV SWITCHYARD

4.1. Introduction

There are two types of substations: (1) Substation and (2) Switchyard

F igur e 4.1: Switchyard at NTPC Anta

4.1.1. Substations

A substation contains a transformer, which steps-up or steps-down power voltages, according

to the end-use purpose and destination. These transformers emit a low humming sound, and

in built-up residential areas, some manufacturing company’s transformers are primarily

contained within a cement sound enclosure to minimize noise.

4.1.2. Switchyards

Switchyard is considered as the HEART of the Power Plant. Power generated can be worthy

only if it is successfully transmitted and received by its consumers. Switchyard plays a very



31

important role as a junction between the generation and transmission. It is a junction, which

carries the generated power to its destination (i.e. consumers).

Switchyard is basically a yard or an open area where many different kinds of equipments are

located (isolator, circuit breaker etc.), responsible for connecting & disconnecting the

transmission line as per requirement (e.g. any fault condition).

Power transmission is done at a higher voltage. (Higher transmission voltage reduces

transmission losses resulting in higher utilization of generating capacity and optimizes the

resource required for capacity addition.).

Therefore, the power generated by the gas generator of 1 to 3 units is 10.5 KV and by the

steam generator of 1 unit is 17.75 KV which is stepped-up to 220 KV by the Generating

transformer & then transmitted to switchyard.

In NTPC Anta there is only one switchyard i.e. 220 KV switchyard.

4.2. Types of Switchyard

There are three types of switchyards:

(1) Conventional Air Insulated Switchyard

(2) Gas Insulated Switchyard

(3) Air Insulated Switchyard

At NTPC Anta 220 KV switchyard is of type Conventional Air insulated Switchyard. There

are 12 bays in 220KV switchyard. A Bay is basically a way for the incoming power from

generator as well as outgoing power for distribution.

4.3. Salient features of 220 KV switchyard at NTPC Anta

4.3.1. Tasks of Switchyard

Delivers electrical power via outgoing transmission lines to various substations.

Protection of transmission system,

controlling the exchange of power,

Maintain the system frequency within the targeted levels,

Determination of power transfer through transmission line,

Fault analysis and subsequent improvements and

Communication



33

F igur e 5.1: L ayout of Double Bus Bar Scheme

5.1.4. Double Bus Bar with Transfer Bus Scheme

This system has additional flexibility for operation.

We can shut down one breaker without interrupting the transmission line.

It is used for critical 220 KV substations.

F igur e 5.2: Double Bus Bar wi th T ransfer B us Scheme

5.1.5 One and Half Bus System

In this system three breakers are used for two circuits.

The loads are automatically transferred to healthy bus from fault bus without

interruption of circuit.



34

It is important for 400 KV, where higher flexibility is required.

At NTPC Anta 220 KV Switchyard Double Main Bus and Transfer Bus Sc heme is

adopted.

5.2. Insulators These provide insulation between line conductors and supports and thus prevent the

leakage of current from conductors to earth.

F igur e 5.3 Strain I nsulator

F igur e 5.4: Suspension I nsulator

Material used for insulators:

Ceramic (Porcelain, Steatite)

Glass

Synthetic Resins



36

5.4. Earthing Switch (E/S)

Earth switch is mounted on the isolator base on the line side or breaker side

depending upon the position of the isolator.

The earth switch usually comprises of a vertical break switch arm with the contact,which engages with the isolator contact on the line side.

Specification of used Isolators with and without E/S at NTPC Anta

Isolator (With Single E/S)

Make S & S Madras

No. of Provided 10Type RC 300 Horizontal Centre Break

Rating 245 kv, 1250 A

No. of Poles 3

Rated SC with stand

Current

31.5 kA, 1 Sec.

Table 5.1: Details of I solator s (with E/s)

Isolator (without E/S)

Make S & S Madras

No. of Provided 10

Type RC 300 Horizontal Centre Break, Tandem

Rating 245 kv, 1250 A No. of Poles 3

Rated SC with stand Current . 31.5 kA, 1 Sec

Table 5.2: Detail s of I solator s (without E/S)

5.5. Clamps and Connectors

There are different types of clamps and connectors used in switchyard for different purposeslike to connect the two conductors, to take tapping etc.



37

5.6. Conductors and Accessories

Conductor consists of several strands wound in layers spiralled along the length of

conductor.

The total no. of individual strands “N” is given by

N=3n^2+3n+1, where N = no. of layers

Diameter of conductor = (2n+1)*d, where d= diameter of strand

F igur e 5.6: ACSR Conductor

Types of Conductors used are:

AAAC – All Aluminum Alloy Conductors

ACSR- Aluminum Conductor Steel Reinforced

AACSR- Aluminum Alloy Conductor Steel Reinforced

5.7. Circuit Breaker

A circuit breaker is an automatically-operated electrical switch designed to protect an

electrical circuit from damage caused by any disturbance in power system. Its function is to

interrupt continuity, to immediately discontinue electrical flow.

It can be used in off-load as well as on-load condition. When a circuit breaker is operated by

sending an impulse through relay, C.B. contact is made or broken accordingly. During this

making and breaking, an arc is produced which has to be quenched; this is done by air, oil,

SF6 gas etc.



38

F igur e 5.7: SF 6 Cir cuit Br eaker

Features of Circuit Breakers

Superior Interrupting Capability

Low Operation Noise

Simple Construction and Compact Size

Easy Installation and Maintenance

High safetyDepending on the arc quenching medium being used C.B.s can be categorized into various

types. In NTPC Anta 220 KV switchyard only one type is being used:-

ACB (Air break circuit breaker):- operated as well as arc quenched through air.

BOCB (Bulk oil circuit breaker):- arc quenching done through oil (Aerosol fluid oil).

MOCB (Minimum oil circuit breaker):- arc quenching done through oil (Aerosol fluid

oil).

ABCB (Air Blast Circuit Breaker):- arc quenching done by blast of air

SF6 circuit breaker: - arc quenching done through SF6 gas.

Hydraulic operated SF6 circuit breaker is the most efficient due to following reasons:-

1. Less maintenance.

2. Arc quenching capability of SF6 gas is more effective than air.

3. Heat transfer capacity is better in this C.B.



39

Specification of Circuit Breaker

Circuit breaker SF6

Make ABB Germany-10 Nos ABB

India- 1 No

Type ELF SL-5-2 and ELF SL-4-1

Rating 245/220 kv,2000 A

Breaking Capacity 40 kv

Insulation Level 1050 kv (Peak)

No. of Breaks per pole Two

Type of Operating Mechanism Closing : Spring, Opening :

Hydraulic

Gas Pressure 7 Kg/cm2

Closing time 70m Sec.

Opening time 20 m Sec.

Table 5.3: Specifi cation of Ci rcui t Br eaker

5.8. Instrument Transformer

These are used in measuring voltage and current in electrical power system and for power

system protection and control.

Types of Instrument Transformer

1. Current Transformer

2. Potential Transformer (CVT Type Transformer used)

5.8.1. Current Transformer

The current transformer is a step up transformer; it means current is stepped down to a very

low value (generally 1 or 5 A) so that it can be used for measuring and protection purposes.

C.T is designed in such a way its Core Material could give high accuracy with low saturation

factor. Core Material is generally made of CRGO Silicon steel. For very low loss

characteristics, μ material (Alloy of Ni -Fe) is used.



40

F igur e 5.8: Connection of CT

Current Transformer is used for basically two major functions: -

1. Metering which means current measurement.

2. Protection such as:

Over current protection

Overload earth fault protection

Bus-bar Protection

Bus Differential Protection

CT is typically described by its current ratio from primary to secondary. There is not more

difference between 220KV and 400 KV CT, only current ratio differs.



41

Specification of Current Transformer Current Transformer

Make ABB India

No. of Provided 30 Nos (1200-600/1A), 3 No (2000-

1000/1)

Type TMBR

Rating 245 kv, 1245 A

No. of Cores 5

Table 5.4: Details of CT

5.8.2. Capacitive Voltage Transformer

It is a step down transformer, which step down the high voltage to a lower value that can be

measured using the measuring instruments. The CVT are connected between phases and

ground in parallel to the circuit. The other most important function of C.V.T is that it blocks

power frequency of 50Hz and allows the flow of carrier frequency for communication.

F igur e .5.9: CVT

Protection of CVT

1. It can be continuously operated at 1.2 times the rated voltage.

2. Short circuit on the secondary side of a transformer can lead to complete damage of the

transformer.

3. Fuses are used in the secondary side to protect the transformer against faulty switching and

defective earthing.



42

5.8.3. Potential Transformer

F igur e 5.10: Potential Tr ansfor mer

Potential transformers are used to operate voltmeters, the potential coils of watt meters and

relays from high voltage lines. The primary windings of the transformers are connected

across the line carrying the voltage to be measured and the voltage circuit is connected across

the secondary winding.

5.9. Surge Arrestor

A surge arrestor is electric equipment used in substations and switch yards. The surge arrester

is used to protect the substation equipment from surges caused by lightning or by sudden

switching. The Surge Arrester consists of spark gap in series with non- linear resistor. This

means that the surge arrestor has high resistance at the operating voltage and low resistance

as the voltage increases. The length of gap is set that normal line voltage is not enough to



43

cause an arc. Thus when lightning strikes the overhead conductors in a substation, the arrestor

acts like a conductor and discharge the surge to the ground.

Surge arrestors are usually constructed of MOA (Metal Oxide Arrester) .

Zinc oxide is a widely used non-linear resistor. The zinc oxide is the form of blocks which

are stacked inside the arrestor. It is well accepted as voltage clippers for effective protection

against over voltages. The striking aspects of this arrestor are its simplicity of construction.

F igur e 5.11: L ightnin g Ar rester

Lightning arrestor on its continuous operation drives a small amount of driving current

usually of magnitude 0.1 to 0.8 mA. For monitoring this leakage current we use a surgemonitor as these leakage current increases with time which indicates the aging of arrestor.



44

Specification of Lightning Arrester in NTPC Anta

Make WSI

No. of Provided 27

Type CPL-II, Heavy duty Station class

Rating 198 kv, 11 kA

Minimum discharge Capacity 5 kj/kv

Table 5.6: Specifi cation of L ightn in g Arr ester i n NTPC Anta

5.9.1. Arcing HornsArcing horns are used for protection of insulators in case of high voltage, which it cannot

withstand. There are two metal rods fitted on the top most and bottom most parts of the

insulator.

During high voltage insulator can’t resist, and crack may be developed. In order to avoid

these arcing horns are provided. Arcing Horns conduct the high voltage to the ground and

protect the insulator.

5.9.2. Ground (Earth) Wires

In an overhead power line, ground (earth) wires are wires that run above the live phase

conductors.

Since lightning caused damage to power equipment, as well as to that of the end users. So by

the use of proper ground (earth) wires above the normal conductors make it very unlikely for

lightning to hit the transmission lines directly. Reliability of transmission lines increases

greatly by the use of ground wires.

5.10. Earthing System

Earthing is to be provided in substations due to following reasons:

The object of earthing is to maintain a low potential on any object.

To provide a means to carry electric current into the earth under normal and fault

conditions, without exceeding any operating and equipment limits or adversely

affecting continuity of service.



45

To assure that a person in the vicinity of grounded facilities is not exposed to the

danger of electric shock.

Following basic require are to be satisfied so as to ensure a proper earthing system:

The earth resistance for the switchyard area should be lower than a certain limiting

value in order to ensure that a safe potential gradient is maintained in the switchyard

area and protective relay equipment operate satisfactorily. For major switchyards and

substations in India this limiting value of earth resistance is to be taken less than 0.5

ohm.

The grounding conductor material should be capable of carrying the maximum earth

fault current without over-heating and mechanical damage.

All metallic objects which do not carry current and installed in the substation such asstructures, parts of electrical equipments, fences, armouring and sheaths of low

voltage power and control cables should be connected to the earthing electrode

system.

The design of ground conductor should take care of the effect of corrosion for the

total life span of the plant.

5.11. Wave Trap

Wave Trap is used to trap the high carrier frequency of 20Hz to 20 KHz and above and allow

the flow of power frequency (50 Hz). High frequencies also get generated due to capacitance

to earth in long transmission lines. The basic principle of wave trap is that it has low

inductance (2 Henry) & negligible resistance, thus it offers high impedance to carrier

frequency whereas very low impedance to power frequency hence allowing it to flow in the

station.



46

F igur e 5.12: Wave Tr ap in switchyard

Generally there are two class of line trap depending upon the value of inductance. Inductance

value may be of 1.0 mH or 0.5 mH.

Specification of Wave Trap used at NTPC Anta

Make WSI

Nos Provided 6Rating 0.5 mH, 1250 A, 220 kv

Table 5.7: Specif ication of Wave Tr ap used at NT PC Anta

5.12. PLCC (Power Line Carrier Communication)

As the name suggests, P.L.C.C. is basically a method in which the line used for power

transmission is also being used for communication.

P.L.C.C is employed for performing following two functions:

1. Communication purposes.

2. Protection

5.12.1. Communication Purpose

There are two types of electrical frequency which flow in a line- 50Hz power signal & 20

KHz of carrier signal. In order to isolate these two frequencies (so that they do not hinder

each other) tapping of the frequencies is done as per the requirement.



47

Since in the buses and bays we need only power frequency, wave traps are being used to

block high frequency carrier signals. C.V.T. blocks the power frequencies and due to the

capacitance present it allows the high frequency carrier signals to pass through co-axial

cables.

5.12.2. Protection

Transmission line between two sub-stations is bi-directional. When a fault occurs and a trip

command is given at one end, the breaker gets opened. Now the other end breaker should also

be opened to completely isolate the line from supply. For this the other end should also give

the trip command. This is when the P.L.C.C. comes into play. From the P.L.C.C. room

present at the tripping end along with the carrier signal, a signal of a lesser frequency is

superimposed and sent to the P.L.C.C. room present at the other end. Now this will be

demodulated and the other end will come to know that tripping has occurred.

F igur e 5.13: PL CC Schematic Di agram

Now it will give a command, which will energize the relay, contact will be made and the

breaker will operate.



48

Specification of PLCC at NTPC Anta

Batter ies for PL CC System

Make Exide Ltd.

Type Lead acid Cell, 2 Volts/Cell

Rating 48V, 300 AH

Battery Charger (PLCC)

Make Chhabi

Nos. Provided 1 (Normal), 1 (Reserve)

PLCC E quipments & Panel

Make ABB India

Nos Provided 8

Table 5.8 Detail s of PL CC at NTPC An ta

5.13. Control and Relay Panel

Control panel mostly consists of meters and protective relays. The meters include ammeter,

voltmeter, wattmeter, energy meter etc. The relays include over voltage relay, over current

relay, over frequency relay, under voltage relay, under frequency relay, earth fault relay,

master trip, distance relays. Auxiliary relay and transformer relays like OLTC out of step,

winding temperature alarm, oil temperature alarm. The trip indicators included are CB SF6

gas density low, CB Air pressure low, VT fuse fail alarm, CB pole disc trip, carrier signal

received, back up protection, auto reclose lock out, control DC supply fails, distance

protection , carrier out of service, distance protection trip etc.

AUTOMATION

Early electrical substations required manual switching or adjustment of equipment, and

manual collection of data for load, energy consumption, and abnormal events. As the

complexity of distribution networks grew, it became economically necessary to automate

supervision and control of substations from a centrally attended point, to allow overall

coordination in case of emergencies and to reduce operating costs. Early efforts to remote

control substations used dedicated communication wires, often run alongside power circuits.



50

Conclusion

The training at grid substation was very helpful. It has improved my theoretical concepts of

electrical power transmission and distribution. Protection of various apparatus was a great

thing. Maintenance of transformer, circuit breaker, isolator, insulator, bus bar etc was

observable.

I had a chance to see the remote control of the equipments from control room itself, which

was very interesting. So the training was more than hope to me and helped me to understand

about power system more

I feel I got the maximum out of that experience. Also I learnt the way of work in an

organization, the importance of being punctual, the importance of maximum commitment,

and the importance of team spirit. I have learnt many things in this 45 days training session.

In my opinion, I have gained lots of knowledge and experience needed to be successful in a

great engineering challenge, as in my opinion, Engineering is after all a Challenge, and not a

Job.

The main objective of the industrial training is to provide an opportunity to undergraduates to

identify, observe and practice how engineering is applicable in the real industry. It is not only

to get experience on technical practices but also to observe management practices and tointeract with fellow workers. It is easy to work with sophisticated machines, but not with

people. The only chance that an undergraduate has to have this experience is the industrial

training period.



51

REFERENCES

Books

1. Anderson 1987 “Transmission Line Reference Book”, Second E dition Substations

Committee

2. Geri. A, “Behavior of grounding system excited by high impulse current: the model

and its validation,” IEEE Trans, Power Deliver, 1999.

3. Nagrath, I.J. and D.P.kothari, Electric Machines, Tata McGraw-Hill , New Delhi,

Third Edition, 2004

4. Kiessling, Friedrich; Nefzger, Peter; Nolasco, Joao F.; Kaintzyk, Ulf (2003),

Overhead Power Lines , Springer, ISBN 3540002979

5. Wadhwa, C.L. (2006), Electrical Power Systems , New Age Publishers , ISBN 978-

8122417739

6. Kiessling, Friedrich (2001), High Voltage Engineering and Testing , IET, ISBN

0852967756

7. Harlow, James (2004). Electric Power Transformer Engineering . CRC Press. ISBN

0-8493-1704-5.

8. Standards

9. IEEE Std 998- 1996 “Guide for Direct Lightning Stroke Shielding of Substation”,IEEE Working Group D5

10. IEEE Std C37.91-2000 IEEE Guide for Protective Relay Applications to Power

Transformers

11. Internet

12. Three-phase transformer circuits from All About Circuits

13. J.Edwards and T.K Saha, Power flow in transformers via the Poynting

vector (http://www.itee.uq.edu.aq/~aupec/aupec00/edwards00.pdf)PDF (264 KB)

ntpc anta report

Documents