Paralleling Procedures

1. Connect the incoming set, as shown in figure 3-20.

2. Make certain that the voltage change board (reconnection board) (fig. 3-12) of the incoming generator is set up for the same output voltage as the on-line generator.

3. Set CKT BRK switch on the incoming set to OPEN. When the incoming set circuit breaker is open (CKT BRK indicator light will be out), operate the load switchgear so that the on-line output voltage is present at the voltage change board of the incoming set.

4. Set the PARALLEL OPERATION-SINGLE UNIT operation switch on both sets to PARALLEL OPERATION.

5. Start the incoming set. The on-line set should be in operation already.

6. After a 5-minute warmup, try the VOLTAGE ADJUST control on the incoming set until the output voltages of both sets are equal. 

CAUTION If the synchronizing lights do not blink on and off in unison, the phase sequence is incorrect. Shut down the incoming set and recheck the cabling to and from the incoming set.

7. On the incoming set, position the ENGINE MANUAL SPEED CONTROL until the SYNCHRONIZING LIGHTS blink on and off as slowly as possible.

8. With one hand on the CKT BRK switch, adjust the ENGINE MANUAL SPEED CONTROL vernier knob until the SYNCHRONIZING LIGHTS dim gradually from full on to full off as slowly as possible. Just as the SYNCHRONIZING LIGHTS dim to out, set and hold the CKT BRK switch to close. When the CKT BRK indicator light comes on, release the switch.

9. On both sets, check that the readings of the PERCENT RATED CURRENT meters and KILOWATTS meters are well within 20 percent of each other. If not, increase the engine power of the set with the lower readings (by adjusting the ENGINE MANUAL SPEED CONTROL to increase the speed) until the readings are about equal. 

NOTE: The division of the kilowatt load is also dependent on the frequency droop of the two sets and must be adjusted at the next higher level of maintenance. If the current does not divide as described above, adjust the reactive current-sharing control located at the right side of the special relay box for equal reading on both percent rated current meters.

10. On the incoming set, readjust the voltage and frequency of the output until it is equal to the output of the on-line set.

Removing a Generator Set from Parallel Operation  Refer to figure 3-19 while following the procedure for removing a generator set from parallel operation.

CAUTION Before removing the generator set( s) from parallel operation, make sure the load does not exceed the full-load rating of the generator set( s) remaining on the line.

1. On the outgoing set, position and hold the CKT BRK switch to OPEN until the CKT BRK indicator light goes out. Release the switch.

2. On the outgoing set, allow the engine to operate with no load for about 5 minutes.

3. On the outgoing set, pull the DC CONTROL CIRCUIT BREAKER to OFF.

4. On the outgoing set, set the START-STOP-RUN switch to STOP.

WARNING Make certain the outgoing set is shut down and there are no voltages at the switchgear terminals connected to the outgoing set. Do not take anybody's word for it! Check it out for yourself! 5. Disconnect the cables going from the outgoing set to the load switchgear.

Stopping Generator Set Operation Refer to figure 3-19 as you study this section.

1. Set the CKT BRK switch to OPEN until the CKT BRK indicator light goes out, then release the CKT BRK switch.

2. Allow the engine to cool down by operating at no load for 5 minutes.

3. Set the START-STOP-RUN switch to STOP.

4. Close all generator doors.

MAINTENANCE There are actually three major categories (or levels) of maintenance. The three categories are (1) depot, (2) intermediate, and (3) organizational. In depot or intermediate maintenance, equipment is restored to like-new condition or subjected to some degree to detailed repairs. Under the organizational category, generator maintenance may consist of inspection, testing, adjustment, and so forth, and then perhaps replacement of, rather than repair of, a faulty component. Two types of organizational maintenance are (1) operator and (2) preventive. Each of the two types should complement the other. Defects discovered during operation of the unit will be noted for future correction either by the operator or by maintenance personnel, as appropriate. The purpose of preventive maintenance is to keep the machinery running trouble-free. The operator will likely have fewer problems if the preventive maintenance work is done well. In our previous discussion we have seen that operator maintenance includes many of the tasks you do before, during, and after you operate the generator set to produce power.

As a member of a unit or organization large enough to have a maintenance crew, you may serve as a member of the crew. As a crew member, you will perform organizational preventive maintenance functions on the generator set periodically according to the manufacture's specifications or to service maintenance manuals. To prevent buildup of contaminants that may cause damage to the operating components or systems of the generator set, you should clean the set periodically. Cleaning operations must be performed only on generator sets that are not operating, that are connected to a parallel bus, or that are connected in a standby mode. To clean the generator set, heed the warnings and cautions given, and proceed as follows:

WARNING Compressed air used for cleaning can create airborne particles that may enter the eyes. Pressure shall not exceed 30 psig (206 kPa). Wearing of goggles is required.

CAUTION Exercise care to prevent dry-cleaning solvent from coming into contact with electrical components. Painted metal surfaces should be wiped with a clean lint-free cloth moistened with cleaning solvent (P-D-680, type II). Hard deposits may be scrubbed off with a bristle brush that has been dipped in solvent. Dry the surfaces with a clean lint-free cloth.

WARNING Dry-cleaning solvent, P-D-680, type II, is flammable and moderately toxic to the skin and eyes. Respiratory and eye protection are required.

Remove any dust, dirt, or sand from inside the generator set with a damp, lint-free cloth. Disconnect the battery cables (negative cable first) and remove any corrosion from the battery terminals, cables, and hold-down with a wire brush. Clean the battery filler cap vent holes.

Clean the instrument faces with a clean, lint-free cloth.