H.6
SEL-387-0, -5, -6 Relay
Instruction Manual
Date Code 20170601
Protection Application Examples
Transformer Winding and CT Connection Compensation Settings Examples
Figure H.5
Standard System Phase-to-Transformer Bushing Connections
Kirchhoff’s Current Law is used at each H-node to determine the primary
phase currents on the H-side of the system:
IA = Ia – Ib
IB = Ib – Ic
IC = Ic – Ia
The following examples start with the currents on the wye-side of the
transformer to graphically derive the currents on the delta side of the
transformer.
shows that system primary current Ia (X-side) lags the
system primary current IA (H-side) by 30 degrees.
Figure H.6
X- and H-Side Current Phasors for Figure H.5
The primary load phase shift determined in
applies for the
phase-to-bushing connections shown in
. In each of these
phase-to-bushing connections, the order of the phases (A, B, C) matches the
order of the bushings (H1, H2, H3).
Non-Standard Phase-to-Bushing Connections.
Consider the
transformer connections in
. This is the same transformer discussed
, but with different phase-to-bushing connections: A-phase to
H3, B-phase to H2, C-phase to H1, a-phase to X3, b-phase to X2, and c-phase
to X1.
C (H3)
B (H2)
A (H1)
Winding 1
Winding 2
A
B
C
a
b
c
H3
H2
H1
X3
X2
X1
b (X2)
c (X3)
a (X1)
IC
IB
IA
Ic/N
Ib/N
Ia/N
Ic
Ib
Ia
Table H.2
(A, B, C) to (H1, H2, H3) Phase-to-Bushing Connections
Bushing
H1
H2
H3
X1
X2
X3
System
Phase
A
B
C
a
b
c
B
C
A
b
c
a
C
A
B
c
a
b
Ic
Ib
Ia
IB
IC
IA
–Ib
Ia
IA = Ia–Ib
X-Side Currents
H-Side Currents
Содержание SEL-387-0
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