GE 750 Instruction Manual page 286

750/760
Feeder Management Relay
7–32
f) Overvoltage (Delta VTs only)
To test Overvoltage for Delta VTs, use the test connections specified in FIGURE 7–2:
Relay Test Wiring – Delta Connection on page 7–4. The following procedure tests
Pickup with One Phase For Operation:
1. Inject V = V = 0 into the bus voltage input of the relay. The Pickup LED
ab cb
should be off.
2. Slowly raise V until the Pickup LED comes on. This is the pickup voltage.
ab
3. Lower V until the Pickup LED goes out. This is the reset voltage, which should
ab
be the pickup value minus 2% of VT.
4. Repeat Steps 1 through 3 except adjust V
The following procedure tests Pickup with Two or Three Phases For Operation:
1. Inject V = V > pickup into the bus voltage input. The Pickup LED should be
ab cb
on.
2. Lower V until the Pickup LED goes out. This is the reset voltage, which should
ab
be the pickup value minus 2% of VT.
3. Slowly raise V until the Pickup LED comes on. This is the pickup voltage.
ab
4. Repeat Steps 1 through 3 except adjust V
g) Overvoltage (Wye and Delta VTs)
To test Overvoltage for Delta and Wye VTs, use the test connections specified in
FIGURE 7–1: Relay Test Wiring – Wye Connection and FIGURE 7–2: Relay Test
Wiring – Delta Connection on page 7–4. The Indications and Operations are as
outlined for Phase TOC 1 on page 7–18.
The following procedure tests Blocking From Logic Inputs:
1. Inject voltage to cause a pickup.
2. Assert a logic input to provide a "Block 1 Trip Relay".
The following procedure tests the element Timing:
1. Connect the "Stop Trigger".
2. Set the voltage source to the required test voltage, then turn off voltage.
3. Reset the timer. Turn the voltage on in the required number of phases, and
measure the operating time. Repeat Steps 2 and 3 four more times and obtain
an average of the time intervals.
4. Reset the relay and disconnect the "Stop Trigger".
h) Neutral Displacement (Wye VTs Only)
To test Neutral Displacement (Wye VTs only), use the test connections specified in
FIGURE 7–1: Relay Test Wiring – Wye Connection on page 7–4.
The following procedure tests the Pickup Level:
1. Apply a three phase balanced nominal voltage to the relay.
2. Reduce one phase voltage slowly until the Neutral Displacement element
operates and note this voltage.
3. Calculate the 3V (neutral voltage, i.e. residual voltage) being supplied to the
0
relay using the formula:
4. Repeat Steps 1 through 3 except adjust V
The following procedure tests Blocking From Logic Inputs:
1. Cause a pickup of the Neutral Displacement element.
2. Assert a logic input to provide a "Blk Ntr Displacement". The Pickup LED should
immediately go out.
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.
bc
.
bc
3V V V V
= + +
0 a b c
and V
bn cn
Protection Schemes
(EQ 7.2)
in turn.
GE Multilin