H.11
Date Code 20170601
Instruction Manual
SEL-387-0, -5, -6 Relay
Protection Application Examples
Transformer Winding and CT Connection Compensation Settings Examples
Figure H.14
Current Flow With Reversed X-Side CT Polarity and Reversed Connections
, the resulting IAW2 current measured by the relay is
now shifted 180 degrees, as compared to
.
Figure H.15
Results of Reversed X-Side CT Polarity and Reversed
Connections
One method to correct this is to reverse the current connections at the relay.
Connect the non-polarity terminal of the CT to the polarity terminal of the
relay current input and the polarity terminal of the CT to the non-polarity
terminal of the relay current input. These changes result in the connections
shown in
An alternate method to correct the phase shift is to use the CT compensation
setting, W
n
, each CTC setting results in a
counter-clockwise phase shift that is a multiple of 30 degrees for an ABC
system phase rotation. Selecting a compensation setting of 6 effectively shifts
the current by 180 degrees (6 • 30° = 180°). Further explanation for selecting
the final settings for non-standard CT connections is provided in
Example H.3
.
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)
Primary
30°
IA
Ia
Secondary
30°
IAW1
IAW2
Содержание SEL-387-0
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