6-10
Close and Reclose Logic
Date Code 20010625
SEL-311L Instruction Manual
where:
3P59
= all three Bus 1 phase voltages (VA, VB, and VC) are hot
27S
= monitored single-phase transmission line voltage (channel VS) is dead
SEL-311L(2) Relay
The SEL-311L(2) Relay verifies that Bus 2 voltage is hot, the transmission line voltage is hot,
and in synchronism after the reclosing relay open interval times out, before allowing circuit
breaker 52/2 to be reclosed. This requires reclose supervision settings:
79CLSD = 0.00 cycles
(only one check)
79CLS
=
25A1
where:
25A1
= selected Bus 2 phase voltage (VA, VB, VC, VAB, VBC, or VCA) is in
synchronism with monitored single-phase transmission line voltage (channel
VS) and both are hot.
Other Setting Considerations for SEL-311L(1) and SEL-311L(2) Relays
Refer to
Skip Shot and Stall Open Interval Timing Settings (79SKP and 79STL, Respectively)
in the following
Reclosing Relay
subsection.
SEL
OGIC
control equation setting 79STL stalls open interval timing if it asserts to logical 1. If
setting 79STL is deasserted to logical 0, open interval timing can continue.
The SEL-311L(1) Relay has no intentional open interval timing stall condition (circuit breaker
52/1 closes first after a transmission line fault):
79STL =
0
(numeral
0)
The SEL-311L(2) Relay starts open interval timing after circuit breaker 52/1 at the remote end
has reenergized the line. The SEL-311L(2) Relay has to see Bus 2 hot, transmission line hot, and
in synchronism across open circuit breaker 52/2 for open interval timing to begin. Thus, SEL-
311L(2) Relay open interval timing is stalled when the transmission line voltage and Bus 2
voltage are not in synchronism across open circuit breaker 52/2:
79STL =
!25A1
[=NOT(25A1)]
Note:
A transient synchronism check condition across open circuit breaker 52/2 could possibly
occur if circuit breaker 52/1 recloses into a fault on one phase of the transmission line.
The other two unfaulted phases would be briefly energized until circuit breaker 52/1 is
tripped again. If channel VS of the SEL-311L(2) Relay is connected to one of these
briefly energized phases, synchronism check element 25A1 could momentarily assert to
logical 1.
So that this possible momentary assertion of synchronism check element 25A1 does not
cause any inadvertent reclose of circuit breaker 52/2, make sure the open interval timers
in the SEL-311L(2) Relay are set with some appreciable time greater than the momentary
energization time of the faulted transmission line. Or, run the synchronism check element
25A1 through a programmable timer before using it in the preceding 79CLS and 79STL
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