Sel 751A - Figure 2.20 SEL-751 A Provides Overcurrent Protection and Reclosing for a Distribution Feeder (Includes Fast Bus Trip Scheme) (Delta-Connected Pts)

2.24
SEL-751A Relay Instruction Manual Date Code 20100129
Installation
AC/DC Control Connection Diagrams
Voltage option is needed for voltage elements, synchronism-check elements, and metering (e.g., voltage, KW, KVAR).
INxxx and OUTxxx indicate user-configurable optional digital inputs and outputs. Voltage channel VS is shown connected
for use in voltage and synchronism-check elements and voltage metering. The VS voltage channel can be used for other
voltage input such as 3VO from a broken delta PT connection as long as care is taken to disable the synchronism-check
elements.
Channel IN provides current I
N
for the neutral ground overcurrent elements. Separate from Channel IN, the residual
ground overcurrent elements operate from the internally derived residual current I
G
(I
G
= 3I
0
= I
A
+ I
B
+ I
C
). But in this
residual connection example, the neutral ground and residual ground overcurrent elements operate the same because
I
N
= I
G
.
Figure 2.20 SEL-751A Provides Overcurrent Protection and Reclosing for a Distribution Feeder
(Includes Fast Bus Trip Scheme) (Delta-Connected PTs)
TC
Trip
Coil
52A
(+)
(—)
Trip
Circuit
IA
C
B
A
SEL-751A RELAY
OUT103
CC
Close
Coil
52B
(+)
(—)
Close
Circuit
IB OUT102
86
Lock
Out
86B
(+)
(—)
Breaker
Failure
Trip
Circuit
IC OUTxxx
IN
FEEDER
52
(+)
OUTxxx
(+)
52A
to Annunciator, RTU,
or SEL-2032/2030/2020
to Bus Relay
(Fast Bus Trip Scheme)
ALARM
OUT101
(+)
(—)
Breaker Status
INxxx
VCNVBVA
VS
NS