Schweitzer Engineering SEL-387-0, Instruction Manual

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H.10
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Protection Application Examples
Transformer Winding and CT Connection Compensation Settings Examples
Non-Standard CT Connections: Reversed CT Polarity.
Figure H.13
shows the X-side CT polarity marks toward the transformer. However,
because the connections to the relay remain the same, the relay currents flow
the same, as in
Figure H.12 . No additional adjustments need to be made
because of this type of non-standard CT connection.
Figure H.13 Current Flow With Reversed X-Side CT Polarity
Non-Standard CT Connections: Reversed CT Polarity and Reversed
Connections.
In Figure H.14 , the polarity marks of the X-side CTs are
toward the transformer, as in Figure H.13 , but the neutral sides of the CTs are
away from the transformer. With these connections, the H-side and X-side
currents are both entering the relay at the relay polarity mark.
B (H2)
C (H3) A (H1)
Winding 1 Winding 2
A
B
C
a
b
c
SEL-387
(Partial)
IAW1
IBW1
ICW1
IAW2
IBW2
ICW2
H3
H2
H1
X3
X2
X1
IA System Ia System
IA Relay Ia Relay
c (X3)
b (X2)
a (X1)