2.39
Date Code 20170927 Instruction Manual SEL-751 Relay
Installation
AC/DC Control Connection Diagrams
A core-balance current transformer is often referred to as a zero-sequence, ground fault, or window current transformer.
Directional control for a Petersen coil-grounded system is selected with setting ORDER containing P (see Table 4.19–
Table 4.21). Nondirectional sensitive earth fault (SEF) protection is also available.
Figure 2.30 SEL-751 Provides Overcurrent Protection for a Petersen Coil-Grounded System
(Wye-Connected PTs)
TC
Trip
Coil
52A
52A
(+)
(—)
Trip
Circuit
IA
C
B
A
SEL-751 RELAY
OUT103
Forward Tripping Direction
Core-Balance CT
CC
Close
Coil
52B
(+)
(—)
Close
Circuit
IB OUT102
86
Lock
Out
86B
(+)
(—)
Breaker
Failure
Trip
Circuit
IC OUTxxx
OUT101
FEEDER
ABc
52
(+)
ALARM
(+)
(—)
Breaker Status
INxxx
IN
Petersen
Coil
TRANSFORMER BANK
+
+
to Annunciator, RTU,
or SEL Communications Processor
VCNVBVA