Question.

Describe the procedure for paralleling a 440-volt 3-phase AC generator with another generator on the line.

Answer.

a- See that the generator circuit breaker and field switch (if furnished) are open.

b. See that the field rheostat handle is set to cut in all the field resistance.

c- Make sure the voltage regulator control switch (if furnished) is turned to the MANUAL position.

d. Make sure the manual voltage control is set at the position that gives the lowest generator voltage.

e. Make sure that both prime mover and electrical ends are examined for evidence of obstruction to moving parts

f. See that the oil reservoir for oil ring lubricated bearings contains the right amount of oil as indicated by the oil sight glass.

g. See that the unit is started and brought up to speed in accordance with the instructions for the type prime mover used.

Be sure that the overspeed governor and trip and all other safety devices are tested and functioning as required by these instructions.

h. Check the lubrication of bearings, check oil and bearing temperatures.

i. See that the collector rings run true, that all brushes ride freely in the brush holders, and that there is no chattering of brushes.

j. For totally enclosed machines with coolers, see that the water is flowing through the cooler, and see that there is no leakage of water. Shut the heaters off (if furnished).

k. Bring the generator up to approximately normal speed.

Close the field switch and bring the voltage up to approximately normal and place the voltage regulator in control.

1. Turn the voltmeter switch on the incoming generator to indicate the generator voltage on the voltmeter.

m. Turn the voltmeter switch on the adjacent generator panel to indicate the bus voltage.

n. Turn the voltage adjusting rheostat of the voltage regulator until the incoming generator voltage is equal to the bus voltage

o. Compare the frequency of the incoming generator with that of the bus and adjust to correspond with the bus frequency

p. Turn the synchroscope switch to the ON position.

The synchro-scope will rotate in one direction or the other.

Adjust the speed of the generator by means of the governor motor control switch until the synchroscope rotates very slowly in the clockwise direction.

q. Be certain that the voltages of the bus and the incoming generator are still equal, and close the generator circuit breaker just before the synchroscope pointer passes very slowly through the zero position (pointing vertically upwards).

When synchronizing lamps are used instead of the synchroscope, the midpoint of the dark period of the lamps corresponds to the vertical position of the synchroscope pointer.

r. Turn the synchronizing switch to the OFF position.

s Adjust the generators so that the kilowatt and the reactive KVA load is divided evenly between them