5-4
BE1-87T Test Procedures
9171300990 Rev R
In terms of current, the trip current is:
I
tap
trip
1
(2 0)
2 70
=
x
=
±
±
1.35 pu
= (1.35)
A
6%
100 mA
.
.
Using Equation 2a:
I
trip
1
2
3 8
3 8
0 35
2 7
=
+
⎛
⎝⎜
⎞
⎠⎟
=
.
.
.
. A
Example Two:
Assume:
tap
tap
slope
1
2
2
3 8
15%
=
=
=
,
. ,
Inputs I
A
pu
I
T
pu
I
A
pu
I
T
pu
:
(
)
.
(
)
.
.
1
1
1
2
2
2
6
3
6
2
3
11 4
3
11 4
3 8
3
=
=
=
⎛
⎝⎜
⎞
⎠⎟
=
=
=
⎛
⎝⎜
⎞
⎠⎟
Check:
I balance
slope
slope
1
0.35
100
1
100
< >
-
(in pu)
>
3
1.983
(
)
(
)
3 < >
0.35
0.15
1 - (0.15)
)
(
Therefore:
Use Equation 1 or 1a.
From Figure 1-2 (the percentage restraint characteristic of the BE1-87T at 15% slope), the minimum
current where trip occurs is:
I trip
1
1
15
3 pu
0
3.53 pu
=
-
=
.
In terms of current, the trip current is:
I trip
1
3.53 pu
tap
= (3.53) (2.0)
= 7.06 A
6%
100 mA
=
x
±
±
Using Equation 1a:
I
trip
1
11 4
1 0 15
2
3 8
7 06
min
.
.
.
.
=
−
×
=
A
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