Phase Differential Trip Accuracy - GE 489 Instruction Manual

7.3 ADDITIONAL FUNCTIONAL TESTS
These tests will require a dual channel current source. The unit must be capable of injecting prefault cur-
rents and fault currents of a different value. Application of excessive currents (greater than 3 × CT) for
extended periods will cause damage to the relay.
NOTE
a) MINIMUM PICKUP CHECK
1. Connect the relay test set to inject Channel X current (I
Increase I until the differential element picks up. Record this value as pickup. Switch off the current. The theoretical
x
pickup can be computed as follows:
b) SINGLE INFEED FAULT
2. Set the I prefault current equal to 0. Set the fault current equal to CT. Apply the fault. Switch off the current. Record the
x
operating time.
3. Set the I prefault current equal to 0. Set the fault current equal to 5 × CT. Apply the fault. Switch off the current. Record
x
the operating time.
c) SLOPE 1 CHECK
4. Connect the relay test set to inject Channel Y current (I
between I and I
x Y
5. Set pre-fault current, I
6. Set fault current, I
7. At this value the relay should operate according to the following formula:
8. Set fault current, I
9. Set fault current, I
d) SLOPE 2 CHECK
10. Set fault current, I
7
11. At this value the relay should operate according to the following formula.
12. Set fault current, I
13. Set fault current, I
e) DIRECTIONAL CHECK
14. Set pre-fault current, I
relay will enable the directional check.
15. Set fault current, I
16. Repeat Steps 1 through 15 for phases B and C.
7-14
I
=
XPU
will be 180°.
and I equal to zero.
x Y
equal to 1½ CT.
Y
2 Slope 1 setting
–
I ------------------------------------------------ -
=
XOP1
2
+
equal to 0.95 × I . Apply the fault. The relay should operate. Switch off the current.
x XOP1
equal to 1.05 × I . Apply the fault. The relay should restrain. Switch off the current.
x XOP1
equal to 2.5 × CT.
Y
2 Slope 1 setting
–
------------------------------------------------ -
I
=
XOP2
2 Slope 1 setting
+
equal to 0.95 × I . Switch on the test set. The relay should operate. Switch off the current.
x XOP2
equal to 1.05 × I . Switch on the test set. The relay should restrain. Switch off the current.
x XOP2
and I equal to 2.5 × CT. At this value the conditions for CT saturation detection are set and the
x Y
equal to 0.95 × I . Switch on the test set. The relay should restrain. Switch off the current.
x XOP2
489 Generator Management Relay

7.3.8 PHASE DIFFERENTIAL TRIP ACCURACY

) into the G3 terminal and out of H3 terminal (Phase A).
x
Pickup setting CT ×
) into the G6 terminal and out of H6 terminal. The angle
Y
3 CT ×
× ---------------- -
Slope 1 setting 2
× ×
2.5 CT
7 TESTING
(EQ 7.5)
(EQ 7.6)
(EQ 7.7)
GE Multilin