successfully run individually, the generator sets are ready for verification of manual paralleling capabili-ty.
Make sure that all generator set RUN/OFF/AUTO control switches are placed in the OFF position and that the master control switch (if used) is also in the manual mode position.
Operate the control switch of one generator set to the RUN position and allow the generator set to start and accelerate to rated speed and voltage.
Manually close the paralleling breaker on this gen-erator set by pushing the breaker close pushbutton on the front face of the PowerCommand control. Al-low the generator set to run at no load for the first phase of the manual paralleling test.
Use extreme caution when perform-ing phase relationship testperform-ing. The system is energized and dangerous voltages are present in many locations. Contact with energized parts will cause serious injury or death. Do not at-tempt these tests unless you have proper equipment for testing and are trained in its safe use.
Check the phase relationship of the generator set output to its Bus PT module. The voltage difference between the L1 phase on the input to the Bus PT board and the generator set PT/CT board should be zero. Repeat this process for each generator set in the system.
Make sure that all generator set RUN/OFF/AUTO control switches are placed in the OFF position and that the master control switch (if used) is also in the manual mode position.
Operate the control switch of one generator set to the RUN position and allow the generator set to start and accelerate to rated speed and voltage.
Manually close the paralleling breaker on this
gen-erator set by pushing the breaker close pushbutton on the front face of the PowerCommand control.
Check the phase relationship of the generator set which is closed to the bus, with each individual gen-erator set. This can be accomplished by starting the second generator set in the system by operating the RUN/OFF/AUTO control switch to the RUN position and allow the generator set to start and accelerate to rated speed and voltage. When generator set fre-quency and voltage have stabilized, operate the display screen of the PowerCommand control to the voltage and frequency screens and use the digital display to verify that the generator set voltage and frequency matches the bus voltage and frequency.
Switch the display screen to the digital synchro-scope (bus frequency) screen and observe the con-trol phase relationship between the generator set and the bus. When the phase relationship of the on-coming generator set is within the acceptance pa-rameters programmed into the control, an asterisk (*) will be displayed on the screen next to the phase difference display.
When the asterisk is displayed on the control panel, check the phase relationship between the genera-tor set and the bus. With the hand-held digital volt-meter, check the voltage from the line side to the load side for each phase of the open paralleling breaker on two phases simultaneously (Figure 8-1).
If the phase relationship is proper, the voltage across the breaker (with the breaker open) should be zero, or nearly zero on both phases when the
”synchronized” indicator lamp is on. The voltage of the two meters should rise and fall at approximately the same time.
Note: If the generator set output phase rotation matches the bus and a PHASE ROTATION warning appears when you attempt to close the paralleling breaker, you should check the generator set and Bus PT boards for proper wiring and interconnection.
Both the primary and secondary wiring in the Bus PT board should be checked. See Table 4-27.
Power Command Control Accessory Box
Bus PT Board (A39) PT/CT
Board (A36)
VM2
VM1
CB (Open)
To Load Bus
FIGURE 8-1. CHECKING PHASE RELATIONSHIP BETWEEN GENERATOR SET AND SYSTEM BUS
Note: For applications where a wye connected gen-erator set is paralleled to a delta connected bus, the generator neutral bus must be floating and the neu-tral connection to the bus PT module must not be used.
Make sure that the “charged” flag is present on the paralleling breaker and push the breaker close pushbutton on the PowerCommand Control to manually close the oncoming set paralleling break-er and paralleling the genbreak-erator set to the system bus.
Note: The breaker close function operates through a permissive relay function in the PowerCommand Control, so the paralleling breaker will not close un-less the generator set is properly synchronized with the system bus.
Perform the phase rotation verification on each generator set in the system, prior to attempting to close it to the live parallel bus for the first time.
When all generator sets have been closed to the bus, observe the voltage, frequency, amp load and kilowatt load on each generator set metering set.
The metering should indicate identical voltage and frequency readings on all generator sets in the sys-tem. Amp and kilowatt readings should all be zero.
With no load on the system, a positive amp load reading on generator sets indicates a voltage differ-ence between the generator sets in the system. A
positive kilowatt reading on any generator set indi-cates a frequency misadjustment on at least one generator set. Perform adjustments necessary to eliminate circulating currents and kilowatt loads.
Save the generator set adjustments made prior to switching off the generator set.
With all generator sets running in parallel in manual (RUN) mode, apply available load to the system.
Observe load sharing levels on the generator sets.
The units should share load proportionally. (The
%load and %amps meters on the PowerCommand control should all read within plus or minus 5% of each other.)
Adjust load sharing parameters within control sys-tem to achieve proper load sharing. Save all changes.
If possible, operate the system at various load lev-els and verify proper operation at each level.
Remove all load from the system and return the generator sets to their normal automatic mode by placing the RUN/OFF/AUTO switch in the AUTO position.