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1.9
Date Code 20171021
Instruction Manual
SEL-421 Relay
Introduction and Specifications
Applications
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
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
Summary of Contents for SEL-421-4
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