PARALLEL OPERATION (LOAD SHARING)

ARMY TM 9-6115-464-12 AIR FORCE TO 35C2-3-445-1 NAVY NAVFAC P-8-624-12 2-10 PARALLEL OPERATION (LOAD SHARING]. a. b. c. d. e. f. g. h. i. 2-14 The first set started shall be designated as “on-line” and the sets in parallel operation shall be designated “on coming”. With all sets shut down install the paralleling cable and connect the load terminal boards as described in paragraph 2-4e. Check that the voltage reconnection boards (paragraph 2-5) of the sets are identically positioned. Do not place the circuit breaker switch on any of the generator sets in the CLOSE position until specifically directed to do so. Closing the circuit breaker switch at any other time may severely damage one or more of the generator sets. Equipment damage could result if caution is not observed. Check that the main power switch (Figure 2-6) at the load is open before attempting to place a generator set on line. Equipment damage could result if caution is not observed. Start the generator sets as described in paragraph 2-6. Do not perform steps 7 & 8 of Figure 2-8. Hold the CKT BRK switch (30, Figure 2-1) of the “on- line” set in the CLOSE position until the CKT BRK indicator light (31 ) illuminates. Place the operation switch (26) in the PARALLEL position. Adjust the voltage on both sets to the required value. Adjust the frequency of the “on-line” set to the re- quired value. Place the operation switch (26) of the “on-coming” set in the PARALLEL position. NOTE Observe the synchronizing lights of the “on-coming” set. The lights should go on and off simultaneously. If the lights go on and off alternately, sets are out of phase. Stop both sets and correct interconnect cables (Figure 2-5). If the problem per- sists, refer to next higher level of maintenance. Adjust the frequency of the “on-coming’’ set a little higher than the “on-line’’ set. Then reduce the frequency slowly with frequency adjust rheostat (29) until the synchronizing lights (25) remain on or off a 2 to 3 se- cond intervals. Carefully observe the synchronizing lights of the “on-coming” set and, at the instant both lights go dark place the CKT BRK switch (30) of the “on-coming” set to the CLOSE position. When the CKT BRK indicator light (31 ) illuminates, the sets are operating in parallel. The kilowatt meter and AC ammeter indicate percentages and do not indicate true KW and ampere readings. Equipment damage could result if caution is not observed. With no external load on the paralleled sets, adjust the frequency adjust rheostat (29) of the “on-coming” set until both rated load meters (kilowatt) read zero. Adjust the voltage adjust rheostat of the “on-coming” set until the percent of rated current meters (ammeters) on both sets read zero. Turning counterclockwise will decrease readings. Apply load to the sets. The kilowatt load should divide so that the load on each set is equal. If the load and current are not shared equally adjust the voltage and frequency rheostats of the “on-coming” set until the load and current are divided equally between the generator sets. The current should divide so that the observed difference between the current on any phase between the “on-line” and “on-coming” sets is not more than 20 percent. If the readings are not within 20 percent, notify higher level maintenance.