Basler Electric BE1-87T - Manual (Page 101)

9171300990 Rev V BE1-87T Test Procedures 5-5
OR I
slope
I
T
T
trip 2
1
100
1
2
1
max
= −

 

× × (Equation 3a)
2) When:
the maximum trip point is established as:
(Equation 4)
OR I T I
T
trip 2 2
1
1
0 35
max
. = −

 

(Equation 4a)
Example Three:
Assume:
Check:
Therefore: Use Equation 4 or 4a.
From Figure 1-2 (the percentage restraint characteristic of the BE1-87T at 15% slope), the minimum
current where trip occurs is:
In terms of current, the trip current is:
Using Equation 4a:
I
trip 2
38 2
2
0 35
2 47
= −

 

=
. .
. A
Example Four:
Assume:
I balance
slope
2
0 35
100
(in pu) <
.
) (
I trip I balance
2 2
- 0.35 (in pu) =
tap = 2, tap = 3.8, slope = 15%.
1 1
Inputs: = 2 A (1 pu)
= 3.8 A (1 pu)
I
I
1
2
I balance
slope
2
0.35
100
< > (in pu)
1 < > 0.35
0.15
< 1 2.333
) (
I trip
2
1 pu - 0.35
= 0.65 pu
=
I trip
2
(0.65 pu) (Tap)
= (0.65) (3.8)
=
=
2.47 A 6% 100 mA ± ±
tap = 2, tap = 3.8, slope = 15%.
1 2
Inputs: = 6 A (3 pu)
= 11.4 A (3 pu)
I
I
1
2