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2.3 PROTECTION SETTINGS
Line Pickup provides tripping in the event that the breaker is closed into a zero-voltage bolted three-phase
fault, such as occurs if the grounding chains are left on the line following maintenance. Figure 2–11: LINE
PICKUP FUNCTIONAL LOGIC shows the functional logic for Line Pickup.
2
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 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 or ground-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 several cycles to establish a memory polarizing voltage. However, this feature still results in
faster tripping for permanent faults past the Zone 1 reach, and below the pickup of the I1 function.
901: LINEPICKUP - Select Line Pickup
Set LINEPICKUP = YES if the line pickup logic is to be used, otherwise set LINEPICKUP = NO.
2-
32
Zone
2
Any Zone 2 Function,
Phase or Ground
I1
Current Detector
Open BreakerDetected
IB
4
Current Detector
Fast Reset
2 5
V1
1
Voltage Detector
(+)
BYPASSTL3 = YES
BYPASSTL3 = NO
REF
Figure 2–11: LINE PICKUP FUNCTIONAL LOGIC
LPS-D Line Protection System
1
TL3
4 5
2
5
TL2
150
3
9 0
TL1
POLE DISAGREEMENT
(Single-Pole Schemes Only)
0
2 CALCULATION OF SETTINGS
2.3.10 LINEPICKUP
1
5
LPU
TRIP
GE Power Management
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