Line Pickup - GE ALPS Instruction Manual

1.4 AUXILIARY PROTECTION FUNCTIONS
1
a) THREE PHASE TRIPPING
The Line Pickup (close-onto-fault) logic provides tripping in the event that the breaker is closed into a zero-voltage bolted
fault, such as occurs if the grounding chains were left on the line following maintenance. For this three phase zero voltage
fault, the Mho distance functions can not operate because they do not have a source of polarizing voltage. The logic is
shown below:
O V E R R E A C H I N G P H A S E O R
G R O U N D D I S T A N C E
I 1 C U R R E N T
D E T E C T O R
A L L P H A S E S O P E N
A L L P H A S E V O L T A G E S
H I G H
When the line is de-energized, the open breaker is detected by the All phases Open signal as shown in the above logic.
The resulting output causes timer TL401 to pickup 150 ms later. Consequently, when the line is energized and a fault cur-
rent higher than the setting of I1 exists, current detector I1 picks up and AND402 produces an output. If the Timer Bypass
setting is set to YES, AND403 immediately produces an output to initiate tripping of the breaker. If the Timer Bypass setting
is set to NO, then tripping occurs after the 45 ms pickup delay of timer TL403. Line Pickup is primarily intended to trip for
closing into zero-voltage bolted faults where the distance functions connected to line-side potential will not operate. How-
ever, regardless of the I1 pickup setting, it can also be used to trip on any type of permanent fault along the entire line
length that produces voltage at the relay location that is sufficient to operate a Zone 2 distance function, but not enough to
pickup the All Phase Voltages High signal. This is accomplished by routing Zone 2 phase-distance or ground-distance func-
tion outputs to AND401. The step distance backup timers are bypassed by the Line Pickup logic.
If the line is energized and no fault exists, the all Phase Voltages High signal picks up and timer TL401 will begin timing; 40
ms later the output of TL402 resets timer TL401 via the fast reset input. AND401 and AND402 have their lower input
removed at that time to take the three phase Line Pickup out of service.
Timer TL403 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. TL403 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 simul-
taneous high-speed reclosing is not used, timer TL403 can be permanently bypassed.
b) SINGLE PHASE TRIPPING
Logic is included to provide high speed tripping when a single phase reclose onto a permanent fault occurs. When a phase
of the circuit breaker is open, the associated timer (TL404, TL405, and TL406) picks up to provide one input to an AND
gate (AND404, AND405, or AND406). This AND gate allows the associated Zone 2 ground distance function to trip without
time delay, and without receiving a permissive channel signal from the remote terminal. The single phase line pickup logic
will be blocked 90 ms after the breaker pole has been closed by the dropout of the timer.
1-12
M T
M T G
I1
T L 4 0 1
1 5 0
9 0
T L 4 0 2
4 0
0
F A S T
R E S E T
Figure 1–4: LINE PICKUP LOGIC DIAGRAM (THREE PHASE TRIPPING)
ALPS Advanced Line Protection System
4 0 1
4 5
5
T L 4 0 3
4 0 2
4 0 3
T I M E R
B Y P A S S
1 PRODUCT DESCRIPTION

1.4.2 LINE PICKUP

LINE PICKUP
4 0 1
T R I P
GE Power Management