9252000898 Rev —
BE1-50/51B-235/-236 Installation
4-3
Figure 4-2. Typical DC Connections
APPLICATION COORDINATION
In a typical application coordination scheme, a BE1-50/51B-235 or BE1-50/51B-236 is used to provide
primary protection for a radial distribution feeder. An electromechanical overcurrent relay with extremely
inverse timing provides protection for the transformer and bus. To improve coordination with the
electromechanical relay, the BE1-50/51B-235 or BE1-50/51B-236 is configured with the following
settings:
•
Integrating reset enabled (SW3-4 ON)
•
ABB type curves selected (SW3-3 OFF)
The feeder reclosing relay is set for two reclose attempts at 3 and 15 seconds after the initial trip. If a
permanent fault occurs (magnitude 10 times pickup), calculate the feeder breaker trip time for each of the
three operations. Refer to Appendix A for the characteristic curve constants and definition of the terms
used in the following time characteristic curve equations.
From the time characteristic curve equation:
K
BD
C
M
AD
T
N
T
+
+
−
=
028
.
0
)
2
02758
.
0
(
1
10
2
7624
.
7
0938
.
2
+
×
+
−
×
=
= 0.209 seconds
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