6-30
Close and Reclose Logic
Date Code 20001006
SEL-351 Instruction Manual
Assume that the line recloser is set to operate twice on the fast curve and then twice on the
slow curve. The slow curve is allowed to operate after two fast curve operations because the
fast curves are then inoperative for tripping. The SEL-351 Relay phase time-overcurrent
element 51PT is coordinated with the line recloser fast curve. The SEL-351 Relay single-
phase time-overcurrent elements 51AT, 51BT, and 51CT are coordinated with the line
recloser slow curve.
Figure 6.9: Operation of SEL-351 Relay Shot Counter for Sequence Coordination With Line
Recloser (Additional Settings Example 1)
If the SEL-351 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 6.8), the line recloser fast curve operates to clear
the fault. The SEL-351 Relay also sees the fault. The phase time-overcurrent pickup 51P 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-351 Relay also sees the fault again. The phase time-overcurrent pickup
51P 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 phase time-overcurrent element 51PT (51PT 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 = 51PT * (SH0 + SH1) + 51AT + 51BT + 51CT
Summary of Contents for SEL-351
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