Basler Electric BE1-87T - 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
=