Schweitzer Engineering Laboratories SEL-351A - Figure 2.22 SEL-351 A Provides Overcurrent Protection for an Ungrounded System (Wye-Connected Pts)

2.30
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.
Directional control for an ungrounded system is selected with setting ORDER=U (see Tab le 4 .1–Table 4 .3 ). Nondirectional
sensitive earth fault (SEF) protection is also available.
Note: The SEL-351A-1 is not equipped for this application.
Figure 2.22 SEL-351A Provides Overcurrent Protection for an Ungrounded System (Wye-Connected PTs)
TC
Trip
Coil
52A
52A
(+)
(—)
Trip
Circuit
IA
C
B
A
NVCVB
SEL-351 RELAY
VA
OUT101
Forward Tripping Direction
Core-Balance CT
CC
Close
Coil
52B
(+)
(—)
Close
Circuit
IB
OUT102
86
Lock
Out
86B
(+)
(—)
Breaker
Failure
Trip
Circuit
IC
OUT103
FEEDER
ABc
52
(+)
to Annunciator, RTU,
or SEL-2032/SEL-2030/SEL-2020
ALARM
(+)
(—)
Breaker Status
IN101
IN
Ungrounded
TRANSFORMER BANK
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