GE Multilin 750/760 Feeder Management Relay 8-25
8 COMMISSIONING TESTS 8.4 PROTECTION SCHEMES
8
For Delta VTs, use the test connections specified in Figure 8–2: Relay Test Wiring – Delta Connection on page 8–3. A neg-
ative sequence voltage can be created by injecting a single phase-phase voltage, or a set of two phase-phase voltages with
a known negative sequence component. For a single phase-phase injection the negative sequence voltage magnitude is
the injected voltage divided by .
To test Pickup for Delta VTs, use the following procedure:
1. Inject a negative sequence voltage of 0 into the bus voltage input of the relay. The Pickup LED should be off.
2. Slowly raise the voltage until the Pickup LED comes on. This is the pickup level.
3. Lower the voltage until the Pickup LED goes out. This is the reset voltage, which should be 2% of VT less than the
pickup level.
Indications and Operations are the same as those outlined in Phase TOC 1 on page 8–16.
The following procedure checks blocking from logic inputs for Delta VTs:
1. Inject voltage to cause a pickup.
2. Assert a logic input to provide a "Block Neg Seq Voltage". The Pickup LED should immediately go out.
3. Repeat steps 1 and 2 for logic input “Block 1 TRIP Relay” as required.
The following procedure checks negative-sequence voltage timing for Delta VTs:
1. Connect the “Stop Trigger".
2. Set the voltage source to the required test voltage, then turn off the voltage.
3. Reset the timer. Turn the voltage on and measure the operating time.
4. Repeat Steps 2 and 3 four more times and obtain an average of the time intervals.
5. Reset the relay and disconnect the “Stop Trigger".
8.4.6 VOLTAGE
a) BUS UNDERVOLTAGE (WYE VTS ONLY)
To test Bus Undervoltage for Wye VTs, use the test connections specified in Figure 8–1: Relay Test Wiring – Wye Connec-
tion on page 8–3.
The following procedure checks Pickup with One Phase For Operation:
1. Inject V
an
= V
bn
= V
cn
= nominal voltage into the bus voltage input of the relay. The Pickup LED should be off.
2. Slowly lower V
an
until the Pickup LED comes on. This is the pickup voltage.
3. Continue to lower V
an
until the Pickup LED goes out. This is the MIN OPERATING VOLTAGE level minus 2% of VT.
4. Raise V
an
until the Pickup LED comes on, and continue to increase until the indicator goes out. This is the reset volt-
age, which should be the pickup value plus 2% of VT.
5. Repeat Steps 1 through 4 except adjust V
bn
and V
cn
in turn.
The following procedure checks Pickup with Two Phases For Operation:
1. Inject V
cn
= nominal voltage and V
an
= V
bn
= a voltage between the MIN OPERATING VOLTAGE and the pickup voltage
into the bus voltage input of the relay. The Pickup LED should be on.
2. Slowly raise V
an
until the Pickup LED goes out. This is the reset voltage, which should be the pickup plus 2% of VT.
3. Reduce V
an
until the Pickup LED comes on. This is the pickup voltage of V
an
.
4. Continue to lower V
an
until the Pickup LED goes out. This is the MIN OPERATING VOLTAGE of V
an
minus 2% of VT.
5. Slowly raise V
an
until the Pickup LED comes on, then reduce V
bn
until the Pickup LED goes out. This is the pro-
grammed
MIN OPERATING VOLTAGE of V
bn
minus 2% VT.
6. Slowly raise V
bn
until the Pickup LED first comes on and then goes out. This is the reset voltage, which should be the
pickup value plus 2% of VT.
7. Lower V
bn
until the Pickup LED comes on. This is the pickup voltage of V
bn
.
8. Repeat Steps 1 through 7, substituting V
cn
for V
an
, V
an
for V
bn
and V
bn
for V
cn
.
3
Courtesy of NationalSwitchgear.com
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