GE ALPS - T11 - Ground Time Overcurrent 51 G

GE Power Management
ALPS Advanced Line Protection System 6-9
6 FUNCTIONAL TESTS (USER SETTINGS) 6.4 BACKUP PROTECTION TESTS
6
6.4.3 T11 – GROUND TIME OVERCURRENT 51G
1. Setting:
OVERCURRNT
(610) 51G = YES
(611) 51G_DIRCNL = NO
(612) 51GPICKUP = [_________] amps,
(615) 51GTIMDIAL = [________] Time dial,
(614) 51GCURVE = [________] Curve,
51G is calculated with the equation
51G = (eq. 6–16)
where
I
0
is equal to the zero-sequence current. Since I
op
is single-phase, I
0
is given by
I
op
/ 3 = I
0
. (eq. 6–17)
Substituting Equation 6–17 into Equation 6–16 yields
I
op
= 51G. (eq. 6–18)
Therefore, 51G will pick up when
I
op
= 51G. The time it takes for 51G to pick up is determined by the time-dial curve in
Chapter 2: CALCULATION OF SETTINGS.
If the test current exceeds 2 x
In
(
In
is the rated current), then the current test should be applied with a
50% duty cycle. For instance, if current is applied for 5 minutes, it should be left off for 5 minutes
before it is reapplied.
2. Connect the relay as shown in Figure 5–2: GROUND REACH TIMER TEST CONNECTIONS on page 5–7.
Start the timer when
I
op
is applied and stop the timer when the A1 closes (the relay trips).
3. For this test remove the relay from test mode and assign TOCTRP to A1.
(2007) A1 = index 119, TOCTRP
4. Apply
I
op
at 2·51G = [________] amps rms and start the timer. Leave the current on until the A1 contact closes, then
stop the timer. The time should be within ±7% of the value found on the ALPS time-dial curve in use.
5. Reduce I
op
to zero.
6. Repeat steps 4 and 5 for
I
op
at 6·51G = [________] and 10·51G = [________].
7. Change the setting of 51G_DRCNL (0611) back to YES if directional control of 51G is required.
3 I
0
×
CAUTION
NOTE