Schweitzer Engineering Laboratories SEL-751 - Figure 4.87 Sequence Coordination between the SEL-751 and a Line Recloser; Figure 4.88 Operation of SEL-751 Shot Counter for Sequence Coordination with Line Recloser (Additional Settings Example 1)

4.151
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Group Settings (SET Command)
Figure 4.87 Sequence Coordination Between the SEL-751 and a Line
Recloser
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-751 phase time-overcurrent element 51P1T is coordinated
with the line recloser fast curve. The SEL-751 single-phase time-overcurrent
elements 51AT, 51BT, and 51CT are coordinated with the line recloser slow
curve.
q Fault occurs beyond line recloser; w fault cleared by line recloser fast curve; e line recloser recloses into fault;
r fault cleared by line recloser slow curve.
Figure 4.88 Operation of SEL-751 Shot Counter for Sequence Coordination With Line Recloser (Additional
Settings Example 1)
If the SEL-751 is in the Reset State (79RS = logical 1) and then a
permanent fault beyond the line recloser occurs (fault current I
F
in
Figure 4.87), the line recloser fast curve operates to clear the fault.
Fast Curve
(Line Recloser)
51P1
Slow Curve
(Line Recloser)
t
I
F
I
51P1T
(SEL-751)
51AT, 51BT, 51CT
(SEL-751)
SEL-751
R
Line Recloser
I
F
79SEQ := 79RS AND 51P1P
SH0 OR SH1
SH1
SH0
Shot Counter 0 1 2 3
4
qw ew e r e r