NOTE
This procedure calculates the “Saturation Factor” as:
SF
= (I * R) (/ (ANSI C-Class voltage rating)
where R includes CT resistance.
See Setting Note 3 for additional information on other definitions of Saturation Factor.
Step 1. Determine the maximum CT secondary fault current for external faults at F
H
, F
L
, F
T
(I
F3
for three-
phase and I
FG
for single-phase). Refer to Figure D-1 for this example.
HIGH
LOW
TERTIARY
A
.
1
43
160
6900
I
F3
A
.
8
30
800
24600
I
F3
A
.
7
29
300
8900
I
F3
9365200990 Rev F
BE1-CDS240 Settings Calculations
D-3
As previously noted, a more complete analysis of CT performance would include examining the
cu
ring the external fault. For brevity, this check is not done in these
calculations.
Step 2 Determine the worst case CT burden voltage for a three-phase fault (V
B3
).
•
For wye-connected CTs:
V
B3
= I
F3
(R
C
+ R
L
+ R
R
)
•
elta-connected CTs, for three-phase fault:
3 I
F3
(R
CT
+ R
L
+ R
R
)
N e th
Setting Note 1).
where:
R
= one-way lead resistance in ohms (wire from CT to Relay)
L
TERTIARY
Step 3
.
Determine the worst-case burden voltage for a line-to-ground fault (V
BG
).
•
For wye-connected CTs:
V
BG
= I
FG
(R
C
+ 2R
L
+ R
R
)
rrent seen by every CT du
.
T
For d
V
B3
=
ot
at the wye connection produces a lower burden on the CTs (see
R
CT
= CT internal resistance
L
R
R
Neglecting
R
R
, use R
= relay resistance in ohms (< 0.05 ohm)
from Table D-1.
HIGH
LOW
T
A
.
6
50
160
I
FG
8100
A
.
7
32
9800
300
I
FG
.
*
.
.
3
0
47
0
1
43
V
V
.
8
25
.
*
.
.
3
0
57
0
7
29
V
B3
V
.
.
*
.
.
2
46
3
0
2
1
8
30
V
B3
V
.
2
33
B3
Summary of Contents for BE1-CDS240
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Page 292: ...ii BE1 CDS240 Human Machine Interface 9365200990 Rev F This page intentionally left blank ...
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Page 349: ...Figure 12 5 Horizontal Rack Mount Front View 9365200990 Rev F BE1 CDS240 Installation 12 5 ...
Page 361: ...Figure 12 17 Typical DC Connection Diagrams 9365200990 Rev F BE1 CDS240 Installation 12 17 ...
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