Schweitzer Engineering Laboratories SEL-751 - Figure 2.25 Transmission Line Directional Overcurrent Protection and Reclosing with Current-Polarization Source Connected to Channel in (Wye-Connected Pts)

2.34
SEL-751 Relay Instruction Manual Date Code 20170927
Installation
AC/DC Control Connection Diagrams
Voltage Channel VS does not need to be connected. Here, it is shown connected for use in voltage and synchronism-
check elements and voltage metering. See Figure 2.21 (d and e) on for synchronism-check VS connection (VSCONN :=
VS) and broken-delta VS connection (VSCONN := 3V0).
In this example, current Channel IN provides current polarization for a directional element used to control 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
).
Figure 2.25 Transmission Line Directional Overcurrent Protection and Reclosing With Current-Polarization
Source Connected to Channel IN (Wye-Connected PTs)
TC
Trip
Coil
52A
(+)
(—)
Trip
Circuit
IA
C
B
A
SEL-751 RELAY
OUT103
Forward Tripping Direction
CC
Close
Coil
52B
(+)
(—)
Close
Circuit
IB OUT102
86
Lock
Out
86B
(+)
(—)
Breaker
Failure Trip
Circuit
IC OUTxxx
IN
VS
NS
LINE
52
(+)
52A
to Annunciator, RTU,
SEL-2032/2030/2020,
or SEL-3530 RTAC
OUT101
ALARM
(+)
(—)
Breaker Status
INxxx
(+)
(—)
From Feeder Relays
(Fast Bus Trip Scheme)
INxxx
TRANSFORMER BANK
VCNVBVA