Schweitzer Engineering Laboratories SEL-421-4 - Figure 6.39 Potential Sources

6.147
Date Code 20171021 Instruction Manual SEL-421 Relay
Protection Applications Examples
Autoreclose and Synchronism-Check Example
Voltage Elements
Enable the voltage check elements.
EVCK := Y. Reclosing Voltage Check (Y, N)
Set the dead line voltage threshold equal to 15 V secondary.
27LP := 15.0. Dead Line Voltage (1.0–200 V secondary)
Set the live line voltage threshold equal to 50 V secondary.
59LP := 50.0. Live Line Voltage (1.0–200 V secondary)
Set the dead bus voltage threshold for Circuit Breakers 1 and 2 equal to 15 volts
secondary.
27BK1P := 15.0. Breaker 1 Dead Busbar Voltage (1.0–200 V secondary)
27BK2P := 15.0. Breaker 2 Dead Busbar Voltage (1.0–200 V secondary)
Set the live bus voltage threshold for Circuit Breakers 1 and 2 equal to 50 V sec-
ondary.
59BK1P := 50.0. Breaker 1 Live Busbar Voltage (1.0–200 V secondary)
59BK2P := 50.0. Breaker 2 Live Busbar Voltage (1.0–200 V secondary)
Trip Logic
If you want Circuit Breaker 2 to always three-pole trip, except when Circuit
Breaker 2 is the leader, program SEL
OGIC control equation E3PT2 as follows:
E3PT2 := NOT LEADBK2. Breaker 2 3PT (SELOGIC Equation)
Synchronism-Check Application
Reclose Circuit Breaker 1 following a three-pole trip if the line is dead and Bus 1
is hot. Reclose Circuit Breaker 2 following a three-pole trip if a synchronism
check across the hot line to Bus 2 is successful or Circuit Breaker 1 is out of ser-
vice and the line is dead and Bus 2 is hot.
Figure 6.39 Potential Sources
BUS 1
VAZ
VY
(Bus Potential) (Bus Potential)
(Line Potential)
Follower
Line Disconnect
SEL-421 Relay
Leader
VBZ
from BUS 2
CB1 CB2
3
11