Sel 421 - Figure 1.3 Single Circuit Breaker Configuration (ESS:= 1); Figure 1.4 Single Circuit Breaker Configuration with Line Breaker Cts (ESS:= 2); Figure 1.5 Double Circuit Breaker Configuration (ESS:= 3)

U.1.9
Date Code 20090715 User’s Guide SEL-421 Relay
Introduction and Specifications
Applications
Figure 1.3 Single Circuit Breaker Configuration (ESS := 1)
Figure 1.4 Single Circuit Breaker Configuration With Line Breaker CTs
(ESS := 2)
Figure 1.5 Double Circuit Breaker Configuration (ESS := 3)
SEL-421 Relay
BUS
CB1
3
3
IW
VAZ
VY
1
Analog Input
IW
VY
VAZ
Function
CB1 protection, line protection
Line protection
Synchronism check
SEL-421 Relay
BUS
CB1
3
1
3
IW
IX
VAZ
VY
3
Analog Input
IW
IX
VY
VAZ
Function
CB1 protection, line protection
CB1 breaker failure
Line protection
Synchronism check
SEL-421 Relay
BUS 1 BUS 2
CB1 CB2
3
3
3
IW
IX
VAZ
VY
VBZ
1
1
Analog Input
IW+IX
IW
IX
VY
VAZ
VBZ
Function
Line Protection
CB1 protection
CB2 protection
Line protection
Synchronism check Circuit Breaker 1
Synchronism check Circuit Breaker 2
Courtesy of NationalSwitchgear.com