Schweitzer Engineering SEL-387-0, Instruction Manual

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H.13
Date Code 20170601 Instruction Manual SEL-387-0, -5, -6 Relay
Protection Application Examples
Transformer Winding and CT Connection Compensation Settings Examples
Figure H.16 Delta-Wye Transformer With Standard Phase-to-Bushing Connections
Select the delta winding as the reference winding. The H-side delta
current is connected to Terminal W1 of the SEL-387 Relay. Therefore,
set W1CTC = 0. The X-side currents are connected to Terminal W2 of
the SEL-387 Relay, so W2CTC must be determined.
Figure H.17 Primary Currents and Secondary Currents as Measured by the
Relay
IAW2 must be rotated 30 degrees (1 multiple of 30 degrees) in the
counterclockwise direction for a system with an ABC phase rotation
to be 180 degrees out-of-phase with IAW1. Therefore, set W2CTC = 1.
The resulting compensation settings for this system are W1CTC = 0
and W2CTC = 1.
EXAMPLE H.2 Delta-Wye Transformer With Non-Standard
Phase-to-Bushing Connections, Standard CT Connections, and an
ABC System Phase Rotation
This example uses the transformer and relay connections of
Figure H.18. This is the same transformer as in Example H.1, but with
non-standard phase-to-bushing connections. Figure H.19 shows that
for this connection, the system current Ia (X-side) leads the system
current IA (H-side) by 30 degrees, or lags by 330 degrees. The CT
connections are standard, which results in IAW2 lagging IAW1 by
B (H2)
C (H3) A (H1)
Winding 1 Winding 2
A
B
C
a
b
c
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)
SEL-387
(Partial)
Primary
30°
IA
Ia
Secondary
150
°
30°
IAW1
IAW2 IAW2 (Compensated)