GE ALPS - 6.4 Backup Protection Tests; T9 - Phase Instantaneous Overcurrent 50

6-8 ALPS Advanced Line Protection System
GE Power Management
6.4 BACKUP PROTECTION TESTS 6 FUNCTIONAL TESTS (USER SETTINGS)
6
6.4 BACKUP PROTECTION TESTS 6.4.1 T9 – PHASE INSTANTANEOUS OVERCURRENT 50
1. Protection Settings:
OVERCURRNT
(601) 50 = YES
(602) 50_DIRCNL = NO
(603) 50PICKUP = [_________] amps
50 is calculated with the following equation:
50 = (
I
A
– I
B
) or ( I
B
– I
C
) or ( I
C
– I
A
) (eq. 6–11)
where 50 is the difference in phase-to-phase current. The test current,
I
op
, is connected to one phase and returned
through another to simulate a phase-to-phase fault. When an AB fault is applied, the difference
( I
A
– I
B
) equals ( I
op
– (– I
op
)) = 2 I
op
. Therefore 50 will pick up when I
op
= 0.5 x 50
2. Connect the relay as shown in Figure 5–1: PHASE-TO-PHASE TEST CONNECTIONS on page 5–6 for a phase AB,
BC, or CA fault.
3. Set the relay into test mode 43 (Phase Overcurrent). The LUI should display: INST PHS OVRC ON
4. Set I
op
= 0.5·50 + 0.05·50 = [________] amps rms and apply to the relay. The A1 contact should close. Lower I
op
to
0.5·50 – (0.05·50) = [________] amps rms; the A1 contact should open.
5. Reduce I
op
to zero.
6.4.2 T10 – GROUND INSTANTANEOUS OVERCURRENT 50G
1. Protection Settings:
OVERCURRNT
(605) 50G = YES
(606) 50G_DIRCNL = NO
(607) 50GPICKUP = [_________] amps,
50G is given by: 50G = (eq. 6–12)
where
I
0
is the zero-sequence current and I
1
is the positive-sequence current. Since the test current, I
op
, is single-
phase,
I
0
and I
1
are given by
I
0
= I
op
/ 3 (eq. 6–13) and I1 = I
op
/ 3 (eq. 6–14)
Substituting Equations 6–13 and 6–14 into Equation 6–12 yields
50G = I
op
– 0.3 I
op
= 0.7 I
op
(eq. 6–15)
Therefore IPT will pick up when
I
op
= 50G / 0.7.
2. Connect the relay as shown in Figure 4–3: PHASE TO GROUND TEST CONNECTIONS on page 4–12.
3. Set the relay into test mode 44 (Ground Overcurrent). The LUI displays: INST GND OVRC ON
4. Set
I
op
to (50G / 0.7) + 0.5 = [________] amps rms and apply to the relay. The A1 contact should close. Lower I
op
to
(50G / 0.7) – 0.5 = [________] amps rms; the A1 contact should open.
5. Reduce I
op
to zero.
6. Change the setting of 50G_DIRCNL back to YES to restore directional control, if required.
3 I
0
0.9 I
1
×
–
×