![Schweitzer Engineering Laboratories SEL-421-4 Instruction Manual Download Page 172](http://html.mh-extra.com/html/schweitzer-engineering-laboratories/sel-421-4/sel-421-4_instruction-manual_1216726172.webp)
5.12
SEL-421 Relay
Instruction Manual
Date Code 20171021
Protection Functions
Current and Voltage Source Selection
illustrates the tapped overhead transmission line with a motor-
operated disconnect (MOD) on the high side of a power transformer and two cir-
cuit breakers on the low side.
Figure 5.9
Tapped EHV Overhead Transmission Line
Figure 5.10
ESS := Y, Tapped Line
SEL-421
SEL-421
BK1S
BK1R
BK2S
CB1
CB2
BK2R
SEL-421
S
R
MOD
(HV)
(LV)
T
(HV)
(LV)
MOD
SEL-421 Relay
IW
VY
1
1
3
3
VAZ
VBZ
CB2
CB1
Analog Input
IW
VY
VAZ
VBZ
Function
Line protection
Line protection
Synchronism check Circuit Breaker 1
Synchronism check Circuit Breaker 2
Tripping
Direction
Summary of Contents for SEL-421-4
Page 6: ...This page intentionally left blank ...
Page 14: ...This page intentionally left blank ...
Page 30: ...This page intentionally left blank ...
Page 104: ...This page intentionally left blank ...
Page 128: ...This page intentionally left blank ...
Page 536: ...This page intentionally left blank ...
Page 584: ...This page intentionally left blank ...
Page 616: ...This page intentionally left blank ...
Page 696: ...This page intentionally left blank ...
Page 750: ...This page intentionally left blank ...
Page 755: ...Instruction Manual PM400 01 NB SEL 400 Series Relays Instruction Manual 20171006 ...
Page 776: ...This page intentionally left blank ...
Page 932: ...This page intentionally left blank ...
Page 976: ...This page intentionally left blank ...
Page 1024: ...This page intentionally left blank ...
Page 1038: ...This page intentionally left blank ...
Page 1064: ...This page intentionally left blank ...
Page 1128: ...This page intentionally left blank ...
Page 1206: ...This page intentionally left blank ...
Page 1316: ...This page intentionally left blank ...
Page 1350: ...This page intentionally left blank ...
Page 1464: ...This page intentionally left blank ...
Page 1468: ...This page intentionally left blank ...
Page 1492: ...This page intentionally left blank ...
Page 1518: ...This page intentionally left blank ...