GE Multilin 489

CHAPTER 7: TESTING
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL 7–17
Minimum Pickup Check
Z Connect the relay test set to inject Channel X current (I
x
) into the G3
terminal and out of H3 terminal (Phase A). Increase I
x
until the
differential element picks up.
Z Record this value as pickup.
Z Switch off the current.
The theoretical pickup can be computed as follows:
(EQ 7.5)
Single Infeed Fault
Z Set the I
x
prefault current equal to 0.
Z Set the fault current equal to CT.
Z Apply the fault.
Z Switch off the current.
Z Record the operating time.
Z Set the I
x
prefault current equal to 0.
Z Set the fault current equal to 5 × CT.
Z Apply the fault.
Z Switch off the current.
Z Record the operating time.
Slope 1 Check
Z Connect the relay test set to inject Channel Y current (I
Y
) into the G6
terminal and out of H6 terminal.
The angle between I
x
and I
Y
will be 180°.
Z Set pre-fault current, I
x
and I
Y
equal to zero.
Z Set fault current, I
Y
equal to 1½ CT.
At this value the relay should operate according to the following formula:
(EQ 7.6)
Z Set fault current, I
x
equal to 0.95 × I
XOP1
.
Z Apply the fault.
The relay should operate.
Z Switch off the current.
Z Set fault current, I
x
equal to 1.05 × I
XOP1
.
Z Apply the fault.
The relay should restrain.
Z Switch off the current.
I
XPU
Pickup setting CT×=
I
XOP1
2 Slope 1 setting–
2 Slope 1 setting+
----------------------------------------------
3CT×
2
---------------
×=
Courtesy of NationalSwitchgear.com