Sel SEL-351S - Page 71

2.35
Date Code 20080103 Instruction Manual SEL-351S Relay
Installation
SEL-351S 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 Table 4.3–Tab le 4. 5).
Nondirectional sensitive earth fault (SEF) protection is also available.
Figure 2.27 SEL-351S 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-2032/2030/2020
ALARM
(+)
(—)
Breaker Status
IN101
IN
Ungrounded
TRANSFORMER BANK