GE 750 User Manual

GE Power Management 750/760 Feeder Management Relay 17-
39
17 COMMISSIONING 17.7 PROTECTION SCHEMES
17
17.7.27 UNDERFREQUENCY 1 (2)
Test Connections per Figure 17–1: RELAY TEST WIRING – WYE CONNECTION or Figure 17–2: RELAY
TEST WIRING – DELTA CONNECTION on page 17–4.
Procedure To Check:
Minimum Operating Voltage Supervision:
1. Set the injection source well below the pickup frequency. Inject
V
a
= 0 V into the bus voltage input of the
relay with
I
a
= I
b
= I
c
above the Minimum Operating Current level. The PICKUP indicator should be off.
2. Slowly increase the voltage in phase A until the PICKUP indicator comes on. Check that the pickup voltage
is the selected Minimum Operating Voltage.
3. Slowly reduce the voltage. Note the voltage at which the PICKUP indicator goes out. Check that this drop-
out voltage is the pickup voltage minus 2 x VT nominal. Turn the injection voltage off.
Minimum Operating Current Supervision:
1. Set the injection source well below the pickup frequency. Inject
V
a
= 0 V into the bus voltage input and I
a
=
I
b
= I
c
= 0 A into the phase current inputs of the relay. The PICKUP indicator should be off.
2. Slowly increase the voltage in phase A above the selected Minimum Operating Voltage. The PICKUP indi-
cator should remain off.
3. Slowly increase the phase A current until the PICKUP indicator turns on. This is the Minimum Operating
Current level. Now reduce the current until the PICKUP indicator turns off. Note the dropout level, which
should be 2% of CT less than the Minimum Operating Current level when the level is
≤
CT. When the Min-
imum Operating Current level is > CT, the dropout level should be 97 to 98% of the Minimum Operating
Current level.
4. Slowly increase the phase B current until the PICKUP indicator turns on. This is the Minimum Operating
Current level. Now reduce the current until the PICKUP indicator turns off. Note the dropout level, which
should be 2% of CT less than the Minimum Operating Current level when the level is
≤
CT. When the Min-
imum Operating Current level is > CT, the dropout level should be 97 to 98% of the Minimum Operating
Current level.
5. Slowly increase the phase C current until the PICKUP indicator turns on. This is the Minimum Operating
Current level. Now reduce the current until the PICKUP indicator turns off. Note the dropout level, which
should be 2% of CT less than the Minimum Operating Current level when the level is
≤
CT. When the Min-
imum Operating Current level is > CT, the dropout level should be 97 to 98% of the Minimum Operating
Current level.
For all procedures following, the injected voltage and currents are always above the minimum
operating levels.
Pickup:
1. Inject voltage at a frequency above the pickup level into phase
V
a
. Slowly decrease the frequency until the
PICKUP indicator comes on. Note the pickup value.
2. Slowly increase the frequency until the PICKUP indicator goes out. Note the dropout level, which should
be the pickup plus 0.03 Hz.
NOTE

GE 750 Specifications

General

Brand	GE
Model	750
Category	Relays
Language	English