Sel SEL-421 - Page 53

U.1.7
Date Code 20020501 User’s Guide SEL-421/SEL-421-1 Relay
Introduction and Specifications
Applications
Figure 1.4 Single Circuit Breaker
Configuration With Line and Breaker CTs (ESS := 2).
Figure 1.5 Double Circuit Breaker Configuration (ESS := 3).
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