ABB RELION REX640 - Page 731

A B C
W1
W2
1/5A
N
1/5A
N
1/5A
N
A1
B1
C1
A B C
1/5A
N
1/5A
N
1/5A
N
W2
A2
B2
C2
1/5A
N
1/5A
N
1/5A
N
A1
B1
C1
1/5A
N
1/5A
N
1/5A
N
A2
B2
C2
W3
W1
W3
Figure 415: Connection of current transformers of Type 1 and example of currents
during an external fault
A B C
1/5A
N
1/5A
N
1/5A
N
W1
W2
A2
B2
C2
1/5A
N
1/5A
N
1/5A
N
A1
B1
C1
A B C
1/5A
N
1/5A
N
1/5A
N
W1
W2
A2
B2
C2
1/5A
N
1/5A
N
1/5A
N
A1
B1
C1
W3 W3
Figure 416: Connection of current transformers of Type 2 and example of currents
during an external fault
Similar connections are done for a three-winding transformer.
If the rated primary current of the current transformers is not equal to the rated
current of the power transformer on a side of the transformer, setting parameters
CT ratio Cor Wnd 1 , CT ratio Cor Wnd 2 and CT ratio Cor 3 must be used to correct
1MRS759142 F
Protection functions
REX640
Technical Manual
731