Nidec 22765-01, Manual

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Page 28
If cross-current compensation is used, paralleling current transformers
must give the same secondary current.
Current transformer secondary windings provide reactive kVA droop
signal to the voltage regulator. Accidental reversal of this electrical
wiring will cause the voltage to attempt to rise with load rather than
droop. If this occurs during paralleling, stop the unit and reverse the
wires at the voltage regulator terminals.
If the set is provided with a unit/parallel switch, set the switch to the
parallel position on the unit being synchronized.
Synchronize the generator by adjusting the speed (frequency) slightly
higher than the system. Observe the synchroscope or the lamps. The
lamps should fluctuate from bright to dark at the rate of one cycle
every 2 to 3 seconds. When the generator is in phase (the lights will be
dark), close the circuit breaker. Immediately after closing the breaker,
measure the line current kVAR of the generator. The readings must be
within the rating of the unit. A high ammeter reading accompanied by
a large kW reading indicates faulty governor control. A high ammeter
reading accompanied by a large kVAR unbalance indicates problems
with the voltage regulator. Adjusting the cross current or voltage droop
rheostat should improve the sharing of kVAR.
To shut down the generator operating in parallel, gradually reduce the
kW load by using the governor to reduce speed. When kW load and
line current approach 0, open the generator circuit breaker. Operate
the generator unloaded for several minutes to dissipate the heat in
the windings. Refer to the prime mover manual for shutdown and
cool-down procedures.
Figure 19 Synchronizing Paralleled Generators with Test Lamps
Load lines from the incoming generator
Load
switch
Synchronizing
lamps
System bus