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
×
–
×