Basler Electric BE1-87T User Manual
Page 80
4-38
BE1-87T Installation
9171300990 Rev V
HIGH
TERTIARY
LOW
)
7
.
0
(
28
3
=
B
V
6
.
19
=
)
7
.
0
(
22
3
=
B
V
4
.
15
=
)
7
.
0
(
35
3
=
B
V
5
.
24
=
Step 14. Determine the burden voltage for a line-to-ground fault (V
BG
).
•
For wye-connected CTs:
(
)
R
L
FG
BG
R
R
I
V
+
=
2
Where:
I
FG
= determined in Step 12
R
L
= one-way lead resistance in ohms
R
R
= relay resistance in ohms (< 0.05 ohm)
•
For delta-connected CTs: V
BG
is a function of the proportion of positive-sequence to zero-
sequence currents but may be approximated by the same equation.
Neglecting R
R
, use R
W
and R
L
from Figure 4-35:
HIGH
TERTIARY
LOW
(
)
)
7
.
0
(
2
28
=
BG
V
2
.
39
=
NONE
(
)
)
7
.
0
(
2
38
=
BG
V
2
.
53
=
Step 15. Determine the effective CT accuracy class (V
CE
):
HIGH
TERTIARY
LOW
Step 16. Determine the saturation factor (S
F
):
Note: V
B
is the largest burden voltage from steps 13 and 14.
HIGH
TERTIARY
LOW
400
2
.
39
=
F
S
1
.
0
=
800
4
.
15
=
F
S
02
.
0
=
240
2
.
53
=
F
S
22
.
0
=
V
V
N
N
CE
C
A
=
=
( )
(Base Accuracy) (Number of CT Turns in Use)
Maximum Ratio
V
CE
=
=
400 600
600
( )
400
V
CE
=
=
800 3000
3000
( )
800
V
CE
=
=
400 1200
2000
240
( )
S
F
V
B
V
CE
=