GE 750 User Manual

17-
26
750/760 Feeder Management Relay GE Power Management
17.7 PROTECTION SCHEMES 17 COMMISSIONING
17
b) FORWARD TRIPPING AND DELTA CONNECTED VTs
Test Connections per Figure 17–2: RELAY TEST WIRING – DELTA CONNECTION on page 17–4.
Characteristics:
1. Set
V
ab
= V
bc
= V
ca
>
MINIMUM POLARIZING VOLTAGE
setpoint at 0
°
, 120
°
, and 240
°
respectively. Inject phase
A current of 0.2 x CT at an angle which is in phase with the polarizing voltage. This angle is outside the
tripping region, so tripping should be blocked. If the function is set to
Control , check that any output relays
programmed for this condition are operated. If the function is set to
Alarm , check that the ALARM and
MESSAGE indicators are flashing, the correct Phase Directional Reverse alarm message is displayed, and
any output relays programmed for this condition are operated.
2. Slowly increase the angle of the phase A current in the lagging direction. The directional element should
detect current flow in the tripping direction when the phase A current is lagging the polarizing voltage by
more than 90
° ±
2
°
. The alarm and output relays should reset.
3. Continue to increase the lagging angle until the alarm is again raised. The phase A current should be lag-
ging the polarizing voltage by an angle of 270
° ±
2
°
.
4. Continue to increase the angle until the phase A current is once again in phase with the polarizing voltage.
The alarm should remain.
5. Repeat the above steps 1 through 4 for current angle adjusted in each of phase B and C.
17.7.8 NEUTRAL TIME OVERCURRENT 1
The procedure to test this element is identical to that outlined in Section 17.7.3: PHASE TIME OVERCUR-
RENT 1 on page 17–21, with the following exceptions.
Current is injected into any one phase, and the element is not subject to the test “phases required for opera-
tion” and “voltage restrained time overcurrent”.
Blocking From Logic Inputs
1. Inject current to cause a pickup.
2. Assert logic input to provide a "Block Neutral Time 1". The PICKUP indicator should immediately go out.
3. Repeat steps 1 and 2 for logic inputs "Block Neutral O/C", "Block All O/C" and “Block 1 TRIP Relay” as
required.
17.7.9 NEUTRAL TIME OVERCURRENT 2
The procedure to test this element is identical to that outlined in Section 17.7.3: PHASE TIME OVERCUR-
RENT 1 on page 17–21, with the following exception.
Current is injected into any one phase, and the element is not subject to the test "phases required for opera-
tion” and “voltage restrained time overcurrent”.
Blocking From Logic Inputs:
1. Inject current to cause a pickup.
2. Assert logic input to provide a "Block Neutral Time 2". The PICKUP indicator should immediately go out.
3. Repeat steps 1 and 2 for logic inputs "Block Neutral O/C", "Block All O/C" and “Block 1 TRIP Relay” as
required.

GE 750 Specifications

General

Brand	GE
Model	750
Category	Relays
Language	English