Slg Fault Scenario For Single-Pole Tripping - GE D90 Plus Instruction Manual

CHAPTER 15: THEORY OF OPERATION

SLG fault scenario for single-pole tripping

PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
: "GND DIST Z1 OP"
Trip 1-Pole Input 1
: "PHS DIST Z1 OP"
Trip 1-Pole Input 2
By default the POTT scheme will issue a single-pole trip. It is assumed that when tripping
three-poles both the zone 1 and the POTT shall initiate three-pole reclosing. This is
achieved by making the following settings.
Trip Reclose Input 1 : "POTT TRIP 3P"
: "GND DIST Z1 OP"
Trip Reclose Input 2
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 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.
Since the line is de-energized, the line pickup element will be 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 operator 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
Block Time Upon Manual Close
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
Block Time Upon Manual Close
enabled. This 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 operator closes
the breaker at the remote end of the line, placing the line in-service.
Several scenarios are considered in the following sections.
An AG fault occurs close to the considered relay. Immediately after the fault, the
disturbance detector (ANSI 50DD) picks-up and activates the phase selector. The phase
selector recognizes an AG fault by asserting its
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 the
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
the breaker control scheme and results in tripping pole A of the breaker.
Simultaneously with the
TRIP PHASE A
operand activates the open pole detector. The latter detector responds to the
signal by declaring phase A open by asserting the
is actually opened). The
TRIP PHASE A
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 (the
operands are asserted). If neutral and negative-sequence overcurrent elements are
BLK CA
mapped into the trip output to trigger single-pole tripping, they must be blocked with the
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
operand blocks the ground distance AG elements (all zones). As a result, the
POLE ?A OP
timer is started.
timer times out and the recloser is
PHASE SELECT AG
GND DIST Z1 OP
operand is asserted by the trip output. This signal is passed to
operand, the
TRIP 1-POLE
OPEN POLE OP ?A
signal resets only after the breaker actually operates
SINGLE-POLE TRIPPING
operand. Ground distance
or operands.
PHS DIST Z1 OP
operand is asserted. This
TRIP PHASE A
operand (even before it
and
OPEN POLE BLK AB OPEN POLE
OPEN POLE BLK N
OPEN
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