Table of Contents
Advertisement
41-347.12C
1. Select ct Ratio:
(
)
KVA
M
I
--------------------- - =
=
P
V 3
------------ -
1000
Select Ratio
2. Select Relay Taps:
I
P
I
=
---- - =
S
N
I
=
R
Select Tap
Desired Tap
3. Determine Mismatch:
% Mismatch =
(
⁄
)
(
I
I
–
RL
RH
100
-------------------------------------------------------- -
⁄
T
T
L
H
4. Check ct Performance:
Z
=
T
N
N P
------- - =
=
N
T
N
V
P
CL
------------------- =
100
(
) Z
>
N
V
/100
P
CL
14
TWO-WINDING TRANSFORMER CALCULATIONS
,
200 000
---------------------- -
=
12.4 3
1000/5
930
4.65 amp.
--------- -
=
200
I
4.65 3
=
RL
T
8.7
=
L
⁄
)
T
T
L
H
=
3.4 R
+
L
×
3.4 0.4
+
1.41 ohms
200
--------- -
=
0.833
240
×
0.833 200
------------------------------ -
100
T
See figure 15
LOW
930 amp.
(N = 200)
8.05 amp.
=
(
⁄
8.05 4.18
100
-------------------------------------------------------------- - =
100
0.45
---------- - =
T
0.45
1.36
0.05 =
---------- -
=
+
8.7
1.67
=
Yes
HIGH
,
20 000
------------------ -
=
167 amp.
69 3
500/5
(N = 40)
167
4.18 amp.
--------- -
=
40
I
4.18 amp.
=
RH
4.18
×
T
---------- -
8.7
=
=
H
8.05
T
4.6
=
H
)
(
⁄
)
8.7 4.6
–
⁄
8.7 4.6
1.92 1.89
–
---------------------------- - =
1.89
1.6%
0.15
1.13R
---------- - =
+
L
T
0.15
×
1.13 0.4
+
---------- -
+
4.6
0.48 ohms
40
--------- -
=
0.333
120
×
0.333 200
0.67
------------------------------ -
=
100
4.64
0.03
Yes
Advertisement
Table of Contents
