This document discusses the debate around whether paralleling generators is a good idea for hospital standby power systems. It provides an overview of how generator paralleling works, including the requirements and components needed. The advantages of paralleling include increased reliability if one generator fails, more flexibility, and better overall system performance compared to a single generator. While paralleling equipment adds some costs, proponents argue the reliability benefits are worth it. However, some argue hospitals could save money by not using paralleling and instead implementing load shedding of lower priority equipment in an outage. The document examines both perspectives on this issue.

1. Standby Power Systems for Hospitals:
The Debate: Is Paralleling Generators a Good Idea?

2. Webcast Announcements
Technical problems?
• Click on the HELP button
• Send a question from the Question window
Slides:
• Click “Enlarge slides” button to view expanded window and slides should change
automatically
• Click on “Download slides” for PDF of all slides
AIA-certified continuing education credits or PDHs:
• Take 10-question exam
• Get 8 answers right to pass
• Hardcopy certificate mailed within 30 days
Archive:
• Within 7 days, an archive with Q&A will be posted
• We will send an email to registered attendees with link
• Can also view from www.csemag.com home page

3. Power Control Systems for
Mission Critical Facilities

4. Control Systems for Onsite
Power Generation and Distribution

5. Custom Designed and Built
to Your Specific Requirements

6. The Industry’s Most Responsive
Factory-Direct Field Service

7. 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.

8. Paralleling Generators –
A Good Idea?
May 14, 2009
Tom Divine

9. Answer
Yes, it’s a good idea.
Paralleled systems have:
• more reliability,
• more flexibility, and
• better performance
than single-generator systems

10. Overview
Anatomy of a Generator Paralleling Scheme (simplified)
• Single Generator
• Requirements for Paralleling
• Multiple Generators
• Additional Functions
Costs
Advantages of Paralleled vs. Single Generators

11. 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
ENG
BKR
LOAD
ENG – Engine
G - Generator

12. 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

13. 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

14. 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

15. 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
ENG
BKR
LOAD
MC – Master Controller
LS – Load Sharing Controller
SYNC – Synchronizer
EC
GOV
VR G
ENG
BKR
LS
MC
SYNC SYNC

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. Advantages
Flexibility
• Generator Sizing
– Design to cost or operational targets
– Lower maintenance for smaller units
• Operation
– Wide load range without under-loading units

23. 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

24. 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

25. 27
27
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

26. 28
28
Cutler-Hammer® Safety
Switch Quick Connect
Cutler-Hammer Roll-Up
Generator Termination Box
Cutler-Hammer Switchboard
Quick Connect Systems
Portable Generator Connection Solutions

27. 29
29
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

28. 30
30
• 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:

29. 31
31
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:

30. 32
32
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!

31. Kenneth L. Lovorn, President & Chief Engineer
Lovorn Engineering Associates, LLC
May 14, 2009

32. Hospital Emergency Power
• Dump expensive paralleling equipment
• Design for generator back-up
• Load shedding of Priority 3 equipment
• Concentrate funding on generator sets

33. 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

34. Dumping the Paralleling
Equipment
Basic paralleling system is sophisticated
Paralleling cabinet fails, system fails

35. Generators and Transfer Switches
Multiple generators without paralleling
Unequal generator sizing

36. Inherit Priority 3 Load Shedding
Additional load transfer switch
Priority 3 loads and transfer switches

37. Real-World Application
Existing 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

38. 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+

39. Real-World Application (con’t)
Electrical Single Lines – Paralleling System

40. Real-World Application (con’t)
 Electrical Single Lines – Generator/Transfer Switch System

41. The right way to parallel engine-generators
ASCO Series 7000
Engine-Generator Paralleling
Control Switchgear

42. Custom Engineered
• Hospitals
• Business-critical
facilities
• Commercial
buildings
• Industrial
complexes

43. Digital Control
• Synchronizes, manages and parallels
• Load management, bus optimization
• Sophisticated communications
capabilities
• Power system monitoring
and protection

44. • Design and development
engineering
• Expert product
and project managers
• Knowledgeable
applications engineers
• Skilled sales force
• Best-in-the-industry
commissioning and
field service
Deep Resources

45. Ensure Your Success
Call 800-800-ASCO
Email: CustomerCare@asco.com