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6-28
Close and Reclose Logic
Date Code 20010625
SEL-311L Instruction Manual
Figure 6.8: Operation of SEL-311L Relay Shot Counter for Sequence Coordination With
Line Recloser (Additional Settings Example 1)
If the SEL-311L Relay is in the Reset State (79RS = logical 1) and then a permanent fault
beyond the line recloser occurs (fault current I
F
in Figure 6.7), the line recloser fast curve
operates to clear the fault. The SEL-311L Relay also sees the fault. The tapped load
instantaneous overcurrent element T50P asserts and then deasserts without tripping,
incrementing the relay shot counter from:
shot = 0 to shot = 1
When the line recloser recloses its circuit breaker, the line recloser fast curve operates again to
clear the fault. The SEL-311L Relay also sees the fault again. The tapped load instantaneous
overcurrent element T50P asserts and then deasserts without tripping, incrementing the relay
shot counter from:
shot = 1 to shot = 2
The line recloser fast curve is now disabled after operating twice. When the line recloser
recloses its circuit breaker, the line recloser slow curve operates to clear the fault. The relay
does not operate on its faster-set tapped load instantaneous/definite time-overcurrent element
T50PT (T50PT is “below” the line recloser slow curve) because the shot counter is now at shot =
2. For this sequence coordination scheme, the SEL
OGIC
control equation trip equation is:
TR = T50PT * (SH0 + SH1) + T51PT
With the shot counter at shot = 2, Relay Word bits SH0 (shot = 0) and SH1 (shot = 1) are both
deasserted to logical 0. This keeps the T50PT tapped load instantaneous time-overcurrent
element from tripping. The T50P element is still operative, and it can still assert and then
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