Parallel Operation (Load Transfer)

TM 5-6115-465-12

TO 35C2-3-446-1

NAVFAC P-8-625-12

TM 06858B/06859D-12

(10) To remove a generator set from parallel operation,

(6) Carefully observe the synchronizing lights of the

place the circuit breaker switch of the set in the OPEN posi-

"on-coming" set and, at the instant both lights go dark, place

tion. Stop the set as described in paragraph 2-11.

the CKT BRK switch (30) of the "on-coming" set to the

CLOSE position. When the CKT BRK indicator light (31)

e. Parallel Operation (Load Transfer). The following

illuminates, the sets are operating in parallel.

method of parallel operation is to be used when it is necessary

to transfer the load from one set to the other without inter-

CAUTION

rupting power.

The kilowatt meter and AC ammeter

indicate precentages and do not in-

NOTE

d i c a t e true KW and ampere

Visually check that the power cable

readings.

and parallel cable are in accordance

(7) With no external load on the paralleled sets, adjust

with figure 2-5. If the cables are not

the frequency adjust rheostat, (29) of the "on-coming" set

attached as indicated, shutdown the

until both rated load meters (kilowatt) read zero. Adjust the

"on-line" set and follow instructions

voltage adjust rheostat of the "on-coming" set until the per-

in paragraph 2-12c.

cent of rated current meters (ammeters) on both sets read

CAUTION

zero. Turning counterclockwise will decrease readings.

(8) Apply load to the sets. The kilowatt load should

Do not attempt load connects in

divide so that the load on each set is equal. If the load and

paragraph 2-12c unless all sets are

current are not shared equally, adjust the voltage and fre-

off and no other external voltage is

quency rheostats of the "on-coming" set until load and cur-

applied to the load.

rent are divided equally between the generator sets.

(1) The set in operation shall be designated as "on-line"

(9) The current should divide so that the observed dif-

and the sets placed in parallel operation shall be designated

ference between the current on any phase between the "on-

"on-coming".

line" and "on-coming" sets is not more than 20 percent.

If the readings are not within 20 percent, notify higher level

(2) Place the operations switch (26, figure 2-7) on both

sets in the PARALLEL OPERATION position.

maintenance.

NOTE

CAUTION

If the reverse power indicator (16)

Do not close the circuit breaker

of either set illuminates and the main

switch after starting the "on-

load contactor opens, open the main

coming" set as serious damage to

power switch and reparallel the

one or both generator sets may

generator sets.

result.

CAUTION

(3) Refer to paragraph 2-10 and start the "on-coming"

set. Do not perform steps 7 & 8 of figure 2-8.

When generator sets are being

operated in parallel, one or more

(4) Note the voltage indicated on the "on-line" set. Ad-

operators must remain with the sets

just the voltage of the "on-coming" set to the voltage noted

to monitor the rated load and current

on the "on-line" set.

meters.

(5) Adjust the frequency of the "on-coming" set to a

NOTE

higher value that that of the "on-line" set.

Three generator sets can be operated

(6) Slowly reduce the frequency of the "on-coming"

in parallel. Paralleling procedures

set until the SYNCHRONIZING LIGHTS (25, figure 2-7)

are the same as those described

flash at 2 to 3 second intervals.

above. One generator set at a time

is brought on line.

CAUTION

Do not place the circuit breaker

switch of the "on-coming" set in the

Prior to removal of generator sets

CLOSE position while the SYN-

from parallel operation, make sure

CHRONIZING LIGHTS are lit as

the load does not exceed the full load

rating of generator set(s) remaining

damage to one or both generator sets

may result.

on line.

2-20