
2.28
SEL-351A Relay
Instruction Manual
Date Code 20080213
Installation
SEL-351A AC/DC Connection Diagrams for Various Applications
A core-balance current transformer is often referred to as a zero sequence, ground fault, or window current
transformer.
The lower CT wiring option (with the core-balance current transformer) is the preferred option (greater sensitivity; no
false residual currents due to CT saturation, etc.).
Directional control for a low-impedance grounded system is selected with setting ORDER containing S. Directional
control for a high-impedance grounded system is selected with setting ORDER=U (see
Nondirectional sensitive earth fault (SEF) protection is also available.
Note: The SEL-351A-1 is not equipped for this application.
Figure 2.20
SEL-351A Provides Overcurrent Protection for a High-Impedance or Low-Impedance Grounded
System (Wye-Connected PTs)
TC
Trip
Coil
52A
(+)
(—) Trip
Circuit
IA
C
B
A
N
VC
VB
SEL-351 RELAY
VA
OUT101
Forw
ar
d T
ripping Dir
ection
CC
Close
Coil
52B
(+)
(—) Close
Circuit
IB
OUT102
86
Lock
Out
86B
(+)
(—) Breaker
Failure Trip
Circuit
IC
OUT103
IN
FEEDER
52
(+)
52A
to Annunciator, RTU,
or SEL-2032/SEL-2030/SEL-2020
ALARM
(+)
(—)
Breaker Status
IN101
IA
Forw
ar
d T
ripping Dir
ection
IB
IC
IN
A
N
B
C
CT Wiring
Pass neutral (N) through
core-balance CT only if
neutral is brought out and it
is grounded only at the
source
Low-Impedance
or
High-Impedance
Grounded
Summary of Contents for SEL-351A
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