4-2
BE1-50/51B-233 Installation
9252000897 Rev A
reclosing relay is set for two reclose attempts at 3 and 15 seconds after the initial trip. If a permanent fault
occurs (magnitude ten times pickup), calculate the feeder breaker trip time for each of the three
operations. Refer to Section 1 for characteristic curve constants.
From the time characteristic curve equation.
K
BD
C
M
AD
T
N
Trip
+
+
−
=
(
)
028
0
2
02758
.
0
1
10
2
7624
7
0938
2
.
.
.
+
×
+
−
×
=
(
)
028
0
05516
.
0
1
10806
124
5248
15
.
.
.
+
+
−
=
seconds
0.29
=
From the reset characteristic curve equation.
1
M
RD
T
2
Reset
−
=
seconds
15.5
1
0
2
7.75
2
−
=
−
×
=
M = 0 if current goes to zero.
Negative result indicates reset time.
Results:
Full trip = 0.209 seconds and full reset = 15.5 seconds if current goes to zero.
In Figure 4-1,
T
A
= 0.209 seconds (relay was at reset).
T
B
= value < T
A
because rewind has not gone to zero.
T
C
= value < T
A
because rewind has not gone to zero.
Figure 4-1. Coordination Timing Diagram
Summary of Contents for BE1-50/51B-233
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