standby power systems for hospitals
TRANSCRIPT
Standby Power Systems for Hospitals: The Debate: Is Paralleling Generators a Good Idea?
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Standby Power Systems for Hospitals: The Debate: Is Paralleling Generators a Good Idea?
Tom Divine, PE, Project
Manager and Electrical
Engineer, Smith Seckman
Reid, Inc. (SSR), Houston.
Today’s Presenters:
Michael Ivanovich,
Editor-in-Chief & Moderator,
Consulting-Specifying Engineer
Kenneth Lovorn, PE,
President and Chief Engineer,
Lovorn Engineering
Associates, Pittsburgh.
Paralleling Generators –
A Good Idea?
May 14, 2009
Tom Divine
Answer
Yes, it’s a good idea.
Paralleled systems have:
• more reliability,
• more flexibility, and
• better performance
than single-generator systems
Overview
Anatomy of a Generator Paralleling Scheme (simplified)
• Single Generator
• Requirements for Paralleling
• Multiple Generators
• Additional Functions
Costs
Advantages of Paralleled vs. Single Generators
Single Generator
Controls required:
• Engine Controller (EC)
– Starts and stops the engine
– Protects engine from damage
– Provides alarms and engine status
• Governor (GOV)
– Controls engine speed
• Voltage Regulator (VR)
– Controls alternator excitation
EC
GOV
VR G
EN
G
BKR
LOAD
ENG – Engine
G - Generator
Single Generator - Disadvantages
Engine/generator failure: critical load is at risk
Generator will require scheduled maintenance
• Load is at risk, or
• Temporary unit required
G G
LOAD LOAD
- ON
- OFF
Solution – Paralleled Generators
Operate multiple, smaller generators on a common bus
• Maintains service when some, but not all, units fail
• AC generators don’t intrinsically operate in parallel
– Fairly sophisticated controls required for parallel operation
• To initiate
• To maintain
G GG G
Requirements for Paralleling
Four requirements for paralleling:
Equal
Frequencies
Equal Phase
Angles
Equal
Voltages
Same Phase
Rotation
Controlled by paralleling system in real time
Go / No Go:
Monitored only
Multiple Generators (simplified)
Synchronization sequence:
• All units start
• Master Controller allows first
unit at voltage and frequency
to close
• Other units locked out until
they match in
– phase angle
– voltage, and
– frequency
After synchronization:
• Load Sharing Controller
adjusts setpoints to control
KW and kVAR flows
EC
GOV
VR G
EN
G
BKR
LOAD
MC – Master Controller
LS – Load Sharing Controller
SYNC – Synchronizer
EC
GOV
VR G
EN
G
BKR
LS
MC
SYNC SYNC
Reliability
System tolerates loss of a single unit
• With N+1 generators, load is served
when one generator fails
• Ability to selectively shed load
allows system to continue to serve
critical loads if more than one unit
fails
G G
LOAD
Additional Functions
Load Shed / Load Restore
• Disconnects loads if overload is imminent
• Responds to loss of generator
• Restores loads as conditions improve
TO LOAD CONTROL
EQUIPMENT – ATS’s,
DISTRIBUTION
G
MC
G
LOAD
Additional Functions
Load Demand
• Shuts down unneeded generators
• Generators run more efficiently
– extending available runtime,
– without wet-stacking at low load
• Restarts units as needed
G
MC
G
LOAD
Design Considerations
Generator Sizing:
• Minimum size generally driven by performance requirements
– Life Safety and Critical branches on within ten seconds
– Minimum size is the projected peak load on these two branches
• N+1 generators required for reliable service to low-priority loads
– Otherwise, reliability for low-priority loads is actually decreased.
• Provision for load growth must be made at installation
Costs
Wide variation in cost of paralleling equipment with:
• Size and number of generators
• Generator voltage
• Required functions
• Level of customization required to meet specifications
• Amount and type of distribution
Range: about $20K - $110K per generator, excluding distribution
• Source: Informal survey of vendors.
Other costs:
• Space requirements
• System complexity requires highly skilled technicians
Hardware
Paralleling gear will typically contain:
• A Master Control cabinet
• Multiple Generator Control cabinets
• Distribution cabinets
Alternatives to discrete controls:
• Unitized controllers,
• Distributed controls,
– with control unit and circuit breaker packaged with generator
Advantages
Flexibility
• Generator Sizing
– Design to cost or operational targets
– Lower maintenance for smaller units
• Operation
– Wide load range without under-loading units
More Advantages
Reliability
• Serves all loads under single-unit failure
• Serves critical loads under multiple-unit failure
Ease of expansion
• Generators can be added as load increases
– If addressed in initial design
Maintenance
• Single generator can be taken out of service in N+1 system
And More Advantages
Performance
• Paralleled system is stiffer than multiple single-unit systems
Mature technology
• Large installed base
• Issues are thoroughly tested and well-understood
2727
Eaton’s Electrical Group
With 2008 net sales of $15.4 billion, Eaton is recognized
around the world for power quality and innovation
Powerware power quality and reliability products
Cutler-Hammer power distribution and control equipment
2828
Cutler-Hammer® Safety
Switch Quick Connect
Cutler-Hammer Roll-Up
Generator Termination BoxCutler-Hammer Switchboard
Quick Connect Systems
Portable Generator Connection Solutions
2929
Caterpillar Paralleling
Switchgear*
Cutler-Hammer Automatic
Transfer Switches
*Eaton, through a joint venture relationship with Caterpillar Corporation, offers Caterpillar
Switchgear with PowerLynx Control Technology
Permanent Generator Connection Solutions
3030
• MRI, CT, X-ray, PET
• Ultrasound, Mammography
• Trauma Centers
• Cath Labs
• Special and Clinical Labs
• Blood Analyzers
Protecting Diagnostic Imaging: UPS
Power problems cause sensitive electronics to fail resulting
in unplanned downtime, system lock-ups, and expensive
maintenance costs.
UPS for:
3131
Protecting IT Systems: UPS
• Pharmacy
• Clinical Labs
• PACS / RIS
• Computerized Physician Order Entry
• Nurses Stations
• Patient Monitoring Systems
• Patient Records
Hospital IT systems are now mission critical. Power
problems cause data loss and equipment failures.
UPS for:
3232
Dedicated Consultant Site
www.eaton.com/consultant
• Order free copy of Eaton’s
Consultant Application Guide
• Sign up for Eaton’s
Consultant Newsletter
• Check out our Lunch &
Learn portal
• Product & service information
• And more!
Kenneth L. Lovorn, President & Chief Engineer
Lovorn Engineering Associates, LLC
May 14, 2009
Hospital Emergency Power
• Dump expensive paralleling equipment
• Design for generator back-up
• Load shedding of Priority 3 equipment
• Concentrate funding on generator sets
Advantages
Lower construction costs
Elimination of the paralleling cabinet
Less total area required
Equivalent or better reliability
Design to serve initial load
Ease of expansion as load grows
More difficult to implement
Requires switches in series
Disadvantages
Dumping the Paralleling Equipment
Basic paralleling system is sophisticated
Paralleling cabinet fails, system fails
Generators and Transfer Switches
Multiple generators without paralleling
Unequal generator sizing
Inherit Priority 3 Load Shedding
Additional load transfer switch
Priority 3 loads and transfer switches
Real-World ApplicationExisting Hospital 800 kW generator
Expansion of 400 kW emergency capacity
Paralleling system parameters
Add two 800 kW generators
Add a paralleling line-up
Implement a Priority 3 load shedding scheme
Real-World Application (con’t)
Multiple generator-transfer switch system Add one 1500 kW generator Add emergency-only distribution panel Priority 1 and 2 loads to 800 kW generator Serve all Priority 3 from 1500 kW generator Second transfer switches for Priority 1 and 2 loads If the 1500 kW generator fails, Priority 3 loads off Savings - $500,000+
Real-World Application (con’t)
Electrical Single Lines – Paralleling System
Real-World Application (con’t)
Electrical Single Lines – Generator/Transfer Switch System
The right way to parallel engine-generators
ASCO Series 7000
Engine-Generator Paralleling
Control Switchgear
Custom Engineered
• Hospitals
• Business-critical
facilities
• Commercial
buildings
• Industrial
complexes
Digital Control
• Synchronizes, manages and parallels
• Load management, bus optimization
• Sophisticated communications
capabilities
• Power system monitoring
and protection
• Design and development
engineering
• Expert product
and project managers
• Knowledgeable
applications engineers
• Skilled sales force
• Best-in-the-industry
commissioning and
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Deep Resources