cummins consideration for paralling dissimilar equipment
TRANSCRIPT
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Considerations forParalleling Dissimilar Equipment
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Paralleling Dissimilar Equipment (2)
General Considerations
• You can parallel anything to anything, BUT:– Genset dissimilarities may result in poorer load
sharing performance or,– Potential for some nuisance tripping of protection– Some problems can be resolved with
modifications in the system sequence ofoperation
• Switchgear to genset “incompatibility” cannormally be resolved with the cooperation ofthe parties.
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Paralleling Dissimilar Equipment (3)
GenSet Compatibility
• Engine Compatibility• Alternator Compatibility• Control Compatibility
– Governor/kW Load ShareSystem
– Voltage Regulation/kVar loadshare system
– Miscellaneous Controls
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Paralleling Dissimilar Equipment (4)
Core Compatibility Point
• When two or more machines areparalleled:
• Instantaneous differences in voltagewill cause current (kVar) flow.
• Instantaneous differences infrequency will cause kW flow.
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Paralleling Dissimilar Equipment (5)
GenSet Compatibility
• Engine Compatibility– Not a big issue for prime power
• High speed engines are generally compatiblewith each other on a steady state basis.
– Review steady state frequency regulation• Typical: plus or minus 0.25% from no load to full
load• Look at “steady state” values
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Paralleling Dissimilar Equipment (6)
Frequency vs Time
59.7
59.8
59.9
60
60.1
60.2
60.3
25 26 27 28 29 30
time
freq
uen
cy
DQKC
DFLE
Steady State Frequency Regulation
FAE engines tend to have faster, more complex governing systemsthan hydro-mechanically fueled engines.
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Paralleling Dissimilar Equipment (7)
Engine Compatibility
• Not a big issue for prime power– High speed engines are generally compatible
with each other on a steady state basis.• Review steady state frequency regulation• Typical: plus or minus 0.25% from no load to full load
– Transient Performance Issues• Dissimilar machines accept and reject load at
different rates• Sudden load changes to paralleled machines may
cause load sharing disturbance.• Reverse power on load rejection
– Extend time delay on reverse power trip– Smaller load steps
» each load step ½ the smallest genset rating
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Paralleling Dissimilar Equipment (8)
GenSet Compatibility:Impact of Harmonics
• All Alternators have “imperfect” sinusoidalwaveforms
• Different alternators have different harmoniccontent
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Paralleling Dissimilar Equipment (9)
GenSet Compatibility:Impact of Harmonics
• Differences in harmonics cause differentwaveform shapes
• Difference in “instantaneous voltage” causecurrent flow
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Paralleling Dissimilar Equipment (10)
A
B
C
N
G
CIRCULATING NEUTRAL CURRENTS
• If there is a current path between dissimilaralternators, current will flow
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Paralleling Dissimilar Equipment (11)
Physical Impact of Pitch(Stator Coil Slot Span)/(# Slots/Pole)
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Paralleling Dissimilar Equipment (12)
Alternator Compatibility
• Compatible alternators have similar harmonics– 3rd Order and multiple harmonics most problematic– 2/3 Pitch machines, which have no 3rd order
harmonics, are “universally” compatible with eachother
• Deal with Dissimilarities by:– Block flow of neutral current
• 3-wire (no neutral) connection on one or all machines• be careful of neutral connection through ground path for
solidly grounded machines.
– Neutral reactors– Replace alternator
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Paralleling Dissimilar Equipment (13)
GenSet Compatibility• Control Compatibility
– Load Sharing (kW &kVar)– Load Govern– Master Synchronizer
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Paralleling Dissimilar Equipment (14)
PowerCommand Compatibility
– PCC Compatible with all that use analogload sharing lines
• Woodward 2301• Barber-Colman• Governors America
– AVR Interface• All PCC, or Reactive Droop
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Paralleling Dissimilar Equipment (15)
Genset Paralleling Compatibility
• Compatible Engines– Similar Transient Performance– Equal Frequency Regulation
• Compatible Alternators– Same Pitch (2/3 most compatible)– Can Solve Incompatibility with
Compromise
• Compatible Controls– Load Sharing is Key Issue
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Paralleling Dissimilar Equipment (16)
Conventional Paralleling Architecture
GOVERNORBIAS SIGNAL
GOV
AVREC
GENSET
GOV
AVREC
GENSET
ILS
PLC
SYNC
PROTECTION
METERALARM
CB
ILS
PLC
SYNC
PROTECTION
METERALARM
CB
PLCPROTECTION
METERALARM
LOAD SHARELINES
DISCRETESIGNALS
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Paralleling Dissimilar Equipment (17)
PowerCommand Systems
CB CB
PCC
GENSET
PCC
GENSET
PLCMETERALARM
LOAD SHARELINES
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Paralleling Dissimilar Equipment (18)
CB CB
PCC
GENSET
PCC
GENSET
PLCMETERALARM
LOAD SHARELINES
PowerCommand Differences
• No Remote Paralleling ControlNecessary
• Genset Control Operates Breaker• No Governor/Speed Bias Available• Load Sharing Lines Connect GenSet
to GenSet• MasterControl Could Be the Same
•• No Remote Paralleling ControlNo Remote Paralleling ControlNecessaryNecessary
•• Genset Control Operates BreakerGenset Control Operates Breaker•• No Governor/Speed Bias AvailableNo Governor/Speed Bias Available•• Load Sharing Lines Connect GenSetLoad Sharing Lines Connect GenSet
to GenSetto GenSet•• MasterControlMasterControl Could Be the SameCould Be the Same
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Paralleling Dissimilar Equipment (19)
Situations
• Using All New PCC GenSets withSwitchgear by Others
• New PCC GenSet with ExistingCummins/Onan GenSets (Detector-style Controls)
• Using a New PCC GenSet withExisting Switchgear and GenSets byOthers
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Paralleling Dissimilar Equipment (20)
Typical Isolated Bus Interface(PCC to Conventional Gear)
PLC
PROTECTION
METER
ALARM
CB
PLC
PROTECTION
METER
ALARM
CB
PCC
GENSET
PCC
GENSET
PLC
PROTECTION
METER
ALARM
LOAD SHARELINES
DISCRETESIGNALS
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Paralleling Dissimilar Equipment (21)
ILSI: Isochronous Load Sharing Interface
Converts PCC Load Sharing Lines
ILSI
CB
ILS
PLC
SYNC
PROTECTION
METERALARM
CB
PCC
GENSET
GOV
AVREC
GENSET
PLCPROTECTION
METERALARM
LOAD SHARELINES
GOVERNORBIAS SIGNAL
NEW SWGR
SECTION
PLCPROTECTION
METERALARM
OptionalComponents
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Paralleling Dissimilar Equipment (22)
ILSI Compatibility
• Woodward 2301• Barber Colman Analog• GAC (Governors America)• Others
– using analog load sharing lines– NOT CAN
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Paralleling Dissimilar Equipment (23)
Paralleling Compatibility
• Genset Paralleling Compatibility– Compatible Engines
• Similar Transient Performance• Equal Frequency Regulation
– Compatible Alternators• Same Pitch (2/3 most compatible)• Can Solve Incompatibility with Compromise
– Compatible Controls• Load Sharing is Key Issue
• Switchgear Compatibility is Non-Issue
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Paralleling Dissimilar Equipment (24)
Specifications
• New Systems:– 2/3 Pitch Alternators– Analog kW Load Sharing Signals
• Old Systems– Deal with “Odd Pitch” Alternators
• Floating Neutral on “odd” machine, or• Reactors, or• Replace Alternator
– Control Upgrades might be best choice
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