Sel SEL-421 - Page 54

U.1.8
SEL-421/SEL-421-1 Relay User’s Guide Date Code 20020501
Introduction and Specifications
Applications
Figure 1.6 Double Circuit Breaker
Configuration With Bus Protection (ESS := 4).
Figure 1.7 Tapped Line (ESS := Y).
SEL-421 Relay
BUS 1 BUS 2
CB1 CB2
33
3
3
IW
IX
VAZ
VY
VBZ
1
1
Analog Input
IW+IX
IW
IX
VY
VAZ
VBZ
Function
CB2 protection
Line protection
CB1 protection
Line protection
Synchronism check Circuit Breaker 1
Synchronism check Circuit Breaker 2
(HV)
Tripping
Direction
(LV)
MOD
SEL-421 Relay
IW
VY
1
1
3
3
VAZ
VBZ
CB2CB1
Analog Input
IW
VY
VAZ
VBZ
Function
Line protection
Line protection
Synchronism check Circuit Breaker 1
Synchronism check Circuit Breaker 2