GE L60, Instruction Manual, Page: 366 / 498

8-26 L60 Line Phase Comparison Relay GE Multilin
8.2 SINGLE-POLE TRIPPING 8 THEORY OF OPERATION
8
The
TRIP 1-POLE
operand initiates automatically a single-pole autoreclose. The autoreclose is started and asserts the
AR
RIP
operand. This operand keeps blocking the Phase Selector so that it does not respond to any subsequent events. At the
same time the operand removes zero-sequence directional supervision from ground distance zones 2 and 3 so that they
could respond to a single-line-to-ground fault during open pole conditions.
The
AR FORCE 3-P TRIP
operand is asserted 1.25 cycles following autoreclose initiation. This operand acts as an enabler
for any existing trip request. In this case none of the protection elements is picked up at this time, therefore no more trips
are initiated.
When the recloser dead time interval is complete it signals the Breaker Control element to close the breaker. The Breaker
Control element operates output relays to close the breaker.
When pole A of the breaker closes this new status is reported to the Breaker Control element, which transfers this data to
the Breaker Failure, Autorecloser, Open Pole Detector and Trip Output elements. The response at Breaker Failure is
dependent on the programming of that element. The response at the autorecloser is not relevant to this discussion. At the
Open Pole Detector, the blocking signals to protection elements are de-asserted.
If the fault was transient the reset time would expire at the autorecloser and the
AR FORCE 3-P TRIP
and
RIP
outputs would
be de-asserted, returning all features to the state described at the beginning of this description.
If the fault was permanent appropriate protection elements would detect it and place a trip request for the Trip Output ele-
ment. As the
AR FORCE 3-P TRIP
is still asserted, the request is executed as a three-pole trip.
The response of the system from this point is as described above for the second trip, except the autorecloser will go to lock-
out upon the next initiation (depending on the number of shots programmed).
c) SLG FAULT EVOLVING INTO LLG
When an AG fault occurs the events unfold initially as in the previous example. If the fault evolves quickly, the Phase Selec-
tor will change its initial assessment from AG to ABG fault and when the trip request is placed either by the Z1 or the 87PC,
a three-pole trip will be initiated. If this is the case, all three
TRIP PHASE A
,
B
and
C
operands will be asserted. The com-
mand is passed to the Breaker Control element and results in a three-pole trip. At the same time the Recloser is initiated as
per settings of the Trip Output. As the
TRIP 3-POLE
operand is asserted (not the
TRIP 1-POLE
operand) the Open Pole is not
activated. Because the
AR RIP
in progress is asserted, the Phase Selector is blocked as well.
If the fault evolves slowly, the sequence is different: The relay trips phase A as in the previous example. The Phase Selec-
tor Resets, the Open Pole Detector is activated and forces Z1 and Z2 AG, AB, CA and negative-sequence overcurrent ele-
ments to reset. If the Z1 BG or 87PC element picks up, no trip command will be issued until the
AR FORCE 3-P TRIP
is
asserted. This happens 1.25 cycles after the first trip. If at this time or any time later a request for trip is placed (due to an
evolving fault), a three-pole trip is initiated. The
TRIP 1-POLE
operand is de-asserted by the
TRIP 3-POLE
operand, resetting
the open pole detector. Shortly all three-poles are opened.
When the dead time expires, the Recloser signals the Breaker Control to close the breaker. At this time all the protection
elements are operational, as the Open Pole Detector is not blocking any elements. If the line-side VTs are used, the Line
Pickup element is armed as well. If there is a fault on the line, these elements will pickup the fault and issue next request for
trip. This request results in three-pole trip as the
AR FORCE 3-P TRIP
is still asserted.
The response of the system from this point is as described above for the second trip, except the Recloser will go to lockout
upon the next initiation (depending on the number of shots programmed).