GE L60, Инструкция по эксплуатации, Страница: 365 / 498

GE Multilin L60 Line Phase Comparison Relay 8-25
8 THEORY OF OPERATION 8.2 SINGLE-POLE TRIPPING
8
• initiate either single or three pole reclosing
• notify the Phase Selector when a trip operation is imminent
When notified that a single pole operation has been initiated Open Pole Detector will:
• initiate blocking of protection elements that could potentially maloperate when a breaker pole is open
• instruct the Phase Selector to de-assert all outputs, as an Open Pole invalidates calculations.
The operation of the scheme in a single breaker arrangement will be described. The line is protected by a L60 using the
87PC, Line Pickup, and Zone 1 Phase and Ground Distance elements. 87PC and/or Zone 1 is configured to issue a single-
pole trip when appropriate (
TRIP 1-POLE INPUT-1:
“
GND DIST Z1 OP
”,
TRIP 1-POLE INPUT-2:
“
PHS DIST Z1 OP
”). It is assumed
that when tripping three-poles both Zone 1 and 87PC shall initiate three-pole reclosing. This is achieved by setting
TRIP
RECLOSE INPUT-1:
“
87PC OP
”,
TRIP RECLOSE INPUT-2:
“
GND DIST Z1 OP
”, and
TRIP RECLOSE INPUT-3:
“
PHS DIST Z1 OP
”.
It is assumed for this discussion that the relay features that are shown on Single Pole Operation diagram above have all
been programmed for the application and are in service. The description begins with line breakers open at both the local
and remote ends, and the operation of the scheme is described in chronological order.
Because the line is de-energized the Line Pickup element is armed. The Recloser is presently enabled. An operator
requests that Breaker Control close the breaker, and it operates output relays to close breaker poles A, B and C. This oper-
ator manual close request is also forwarded from Breaker Control to recloser, which becomes disabled, de-asserting its
“Enabled” output. This output is transferred to Trip Output, where it converts any input request for a single pole operation
into a three-pole operation. At the Recloser, the
AR1 BLK TIME @ MAN CLOSE
timer is started.
The breaker closes and status monitoring contacts on the breaker poles change state; the new breaker pole states are
reported to Breaker Control, which in turn transfers these states to the recloser, Trip Output, Breaker Failure and Open Pole
Detector. Because a fault is not detected the
AR1 BLK TIME @ MAN CLOSE
times out and the Recloser is enabled, which
asserts the “Enabled” output, informing the Trip Output element that single pole trip operations are now permitted. When
normal voltage appears on the line the Line Pickup element is disarmed. As the local line breaker has not tripped the oper-
ator closes the breaker at the remote end of the line, placing the line in service.
Several scenarios are considered below.
The 87PC element must be applied according to the Single Pole Tripping Applications section in Chapter 9.
b) SLG FAULT
An AG fault occurs close to the considered relay. Immediately after the fault, the Disturbance Detector (50DD) picks-up and
activates the Phase Selector. The Phase Selector recognizes an AG fault by asserting its
PHASE SELECT AG
operand.
87PC and/or Ground distance zone 1 (AG element) responds to the fault. As the fault is close to the relay, phase distance
zone 1 (AB, CA elements) may respond to this fault as well. In any case, a single-pole operation is requested by zone 1 via
87PC and/or the
GND DIST Z1 OP
and/or
PHS DIST Z1 OP
operands.
At this moment the request to trip is placed for the Trip Output. As the fault is recognized as an AG fault, the TRIP PHASE
A operand is asserted by the Trip Output. This signal is passed to the Breaker Control scheme and results in tripping pole A
of the breaker.
Simultaneously with the
TRIP PHASE A
operand, the
TRIP 1-POLE
operand is asserted. This operand activates the open pole
detector. The latter detector responds to the
TRIP PHASE A
signal by declaring phase A open by asserting
OPEN POLE OP
Φ A
(even before it is actually opened). The
TRIP PHASE A
signal resets only after the breaker actually operates as indicated
by its auxiliary contact. At this moment the Open Pole Detector responds to the breaker position and continues to indicate
phase A opened. This indication results in establishing blocking signals for distance elements (
OPEN POLE BLK AB
,
OPEN
POLE BLK CA
operands are asserted). If neutral and negative-sequence overcurrent elements are mapped into the Trip Out-
put to trigger single-pole tripping, they must be blocked with the
OPEN POLE BLK N
operand, specifically provided for this
purpose. The
OPEN POLE BLK N
operand must be assigned through the block setting of the overcurrent element. The two
latter operands block phase distance AB and CA elements, respectively (all zones); the
OPEN POLE Φ A OP
blocks the
ground distance AG elements (all zones). As a result, the Z1 OP and Z2 PKP operands that were picked-up reset immedi-
ately. The following distance elements remain operational guarding the line against evolving faults: BG, CG and BC.
Depending on response times, the actual trip is initiated either by zone 1 or by 87PC. At the moment
TRIP 1-POLE
operand
is asserted, the Phase Selector resets and no other trip action could take place. After the trip command is issued all the
picked up elements are forced to reset by the Open Pole Detector.
NOTE