TM 9-6115-604-34
NAVFAC P-8-633-34
12-18. CIRCUIT INTERRUPTER (OVER-VOLTAGE AND UNDERVOLTAGE).
a.
General. To protect the load from generator malfunction (for example, over voltage or under voltage) a
circuit interrupter is connected between the generator voltage reconnection system and the generator output
terminals. A voltage sensing circuit operates the circuit interrupter if an over voltage or an under voltage
condition occurs.
b.
Apparatus. Instrumentation for measuring voltage shall be as described and illustrated in Figure 12-8.
c.
Procedure I (Overvoltage).
(1)
Preparation for bench test.
(a)
Locate and disconnect the input circuit to the input terminals of the overvoltage protective
sensing circuit, and connect the apparatus in accordance with Figure 12-8.
(b)
Select curve "A" on both the undervoltage and overvoltage relays.
(2)
Test.
(a)
Close S1 (A, Figure 12-8), and start, operate the set at rated frequency and no load, and adjust R1 for
2400/4160 V.
(b)
Set the oscillograph chart speed such that the individual waveform peaks are dearly visible. Set the
timing lines to a minimum of 0.01 second per line or use a 60 Hz time trace. Adjust the trace peak-to-
peak amplitude to a minimum of 1 inch (25.4 mm).
(c)
Read and record both voltmeter readings.
(d)
With the oscillograph recording and the circuit breaker closed, adjust R1 (A) until the circuit breaker
trips on overvoltage.
(e)
The generator set contains an overvoltage malfunction indicator. Check and record its indication.
(f)
Record whether or not the set shuts down.
(g)
Open S1, and readjust R1 for 2400/4160 V. The voltage difference between S1 open and S1 dosed is
the difference between rated voltage and overvoltage.
(h)
Repeat steps (b) through (g), above, two additional times.
d.
Procedure II (Undervoltage). Prepare for the test in accordance with step c, above.
(1)
Close S1 (A, Figure 12-8), and start and operate the set at rated frequency and no load, and adjust R1 for
2400/4160 V.
(2)
Set the oscillograph chart speed such that the individual waveform peaks are dearly visible. Set the timing
lines to a minimum of 0.01 second per line or use a 60 Hz timing trace. With S1 open, adjust the trace peak-
to-peak amplitude to a minimum of 1 inch (25.4 mm).
(3)
With the set operating and the circuit breaker and S1 open, read and record both voltmeter readings.
(4)
Close S1 and circuit breaker.
(5)
With the oscillograph recording, open S1, and adjust R1 until the circuit breaker trips on undervoltage.
(6)
Check and record the indication of the undervoltage malfunction indicator.
(7)
The voltage difference between S1 open and S1 closed is the difference between the rated voltage and
undervoltage.
(8)
Repeat steps (2) through (7), above, two additional times.
12-25
