GE LPS-O, Instruction Manual

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2-
20
LPS-O Line Protection System GE Power Management
2.3 PROTECTION SETTINGS 2 CALCULATION OF SETTINGS
2
Figure 2–8: LINE PICKUP FUNCTIONAL LOGIC
When the line is de-energized, the open breaker detector (formed by IB and the positive-sequence voltage
detector V1) produces an output indicating that the line is dead. The resulting output from AND4 causes timer
TL2 to operate 150 ms later.
If the line is energized and no fault exists, V1 picks up and timer TL1 will begin timing; 25 ms later the output of
TL1 resets timer TL2 via the fast reset input. AND1 and AND2 have the lower inputs removed at that time to
take Line Pickup out of service.
If the line is energized and a fault exists, current detector I1 or one of the Zone 2 distance functions will operate
and AND1 and/or AND2 will produce an output.
If BYPASSTL3 = YES, then the bottom input of AND3 is connected to (+), and AND3 immediately produces an
output to initiate tripping of the breaker. If BYPASSTL3 = NO then the bottom input of AND3 is connected to
reference (REF), and tripping will occur after the 45 ms pickup delay of timer TL3.
Timer TL3 is provided for those cases where simultaneous high-speed reclosing is employed at both ends of
the line, and where the I1 function must be set to pick up below the maximum load current that can occur at
that time. TL3 then allows time for the voltage to return to normal and take Line Pickup out of service before it
can trip on load current. If simultaneous high-speed reclosing is not used, timer TL3 can be permanently
bypassed.
Line Pickup via the I1 function is intended primarily to trip for zero-voltage bolted faults wherein the distance
functions connected to line-side potential will not operate. As an additional feature, operation of any one of the
Zone 2 distance functions will also initiate a line pickup trip. This is accomplished by routing the Zone 2 phase-
distance function outputs to the upper input of AND1. The other input to AND1 comes from the normal line-
pickup-enable output of timer TL2 as previously described. Operating time for the distance functions will be
slower than normal since the pre-fault voltage is zero (assuming line-side potential) and it takes the relay sev-
eral cycles to establish a memory polarizing voltage. However, this feature still results in faster tripping for per-
manent faults past the Zone 1 reach, and below the pickup of the I1 function.
Zone
2
I1
IB
V 1
BYPASSTL3 = YES
BYPASSTL3 = NO REF
(+)
L P U
T R I P
1
4
1
2
3
1
45
5
Any Zone 2 Function
Current Detector
Voltage Detector
Current Detector
Open Breaker Detected
Fast Reset
TL2
TL3
TL1