GE L60 Instruction Manual

Also see for L60: Communications manual Communications guide Instruction manual Instruction manual Instruction manual

Contents

8-34 L60 Line Phase Comparison System GE Multilin8.2 SINGLE-POLE TRIPPING 8 THEORY OF OPERATION8• 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 the87PC, 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 assumedthat when tripping three-poles both Zone 1 and 87PC shall initiate three-pole reclosing. This is achieved by setting TRIPRECLOSE 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 allbeen programmed for the application and are in service. The description begins with line breakers open at both the localand 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 requeststhat breaker control close the breaker, and it operates output relays to close breaker poles A, B and C. This operator man-ual 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 arereported to breaker control, which in turn transfers these states to the recloser, trip output, breaker failure and open poledetector. Because a fault is not detected the AR1 BLK TIME @ MAN CLOSE times out and the recloser is enabled, whichasserts the “Enabled” output, informing the trip output element that single pole trip operations are now permitted. When nor-mal voltage appears on the line the line pickup element is disarmed. As the local line breaker has not tripped the operatorcloses 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 FAULTAn AG fault occurs close to the considered relay. Immediately after the fault, the disturbance detector (50DD) picks-up andactivates the phase selector. The phase selector recognizes an AG fault by asserting its PHASE SELECT AG operand. Theline phase comparison element (ANSI 87PC) and/or ground distance zone 1 (AG element) responds to the fault. As thefault 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 line phase comparison element (ANSI 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 Aoperand is asserted by the trip output. This signal is passed to the breaker control scheme and results in tripping pole A ofthe breaker.Simultaneously with the TRIP PHASE A operand, the TRIP 1-POLE operand is asserted. This operand activates the open poledetector. The latter detector responds to the TRIP PHASE A signal by declaring phase A open by asserting OPEN POLE OPΦA (even before it is actually opened). The TRIP PHASE A signal resets only after the breaker actually operates as indicatedby its auxiliary contact. At this moment the open pole detector responds to the breaker position and continues to indicatephase A opened. This indication results in establishing blocking signals for distance elements ( OPEN POLE BLK AB , OPENPOLE 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 thispurpose. The OPEN POLE BLK N operand must be assigned through the block setting of the overcurrent element. The twolatter operands block phase distance AB and CA elements, respectively (all zones); the OPEN POLE ΦA OP blocks theground 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 the line phase comparison element (87PC).At the moment TRIP 1-POLE operand is asserted, the phase selector resets and no other trip action could take place. Afterthe trip command is issued all the picked up elements are forced to reset by the open pole detector.NOTE