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6.139
Date Code 20171021
Instruction Manual
SEL-421 Relay
Protection Applications Examples
Autoreclose Example
Unlatch the reclose command to Circuit Breaker 1 when all three poles are
closed.
ULCL1 :=
52AA1 AND 52AB1 AND 52AC1
.
Unlatch Closing for Circuit
Breaker 1 (SEL
OGIC
Equation)
Drive the autoreclose logic to lockout if the SEL-421 detects an LOP condition.
79DTL :=
LOP
.
Recloser Drive to Lockout (SEL
OGIC
Equation)
You can block the reclaim timing. However, it is not necessary for this single shot
application example.
79BRCT :=
NA
.
Block Reclaim Timer (SEL
OGIC
Equation)
When leaving the lockout condition, the recloser goes to the Ready or Reset state
after the 3PMRCD (Manual Close Reclaim Time Delay) timer has expired.
3PMRCD :=
900
.
Manual Close Reclaim Time Delay (1–99999 cycles)
If Circuit Breaker 1 reclose supervision conditions fail to occur within 300 cycles
after the three-pole open interval time delay expires, BK1CLST will assert, and
the autoreclose logic goes to lockout.
BK1CLSD :=
300
.
BK1 Reclose Supervision Delay (OFF, 1–99999 cycles)
Three-Pole Reclose
Set the three-pole open interval time equal to 30 cycles.
3POID1 :=
30
.
Three-Pole Open Interval 1 Delay (1–99999 cycles)
There is no need to enable fast three-pole autoreclose because we have already
used the first and only three-pole shot for this purpose.
3PFARC :=
NA
.
Three-Pole Fast ARC Enable (SEL
OGIC
Equation)
Set the reset time following a three-pole autoreclose cycle equal to 900 cycles.
3PRCD :=
900
.
Three-Pole Reclaim Time Delay (1–99999 cycles)
Initiate a three-pole autoreclose cycle when the SEL-421 three-pole trips because
of Zone 1 phase-distance protection. Communications-assisted tripping is not
enabled.
3PRI :=
3PT AND Z1P
.
Three-Pole Reclose Initiation (SEL
OGIC
Equation)
You can force the autoreclose logic to skip a three-pole shot. However, it is not
necessary for this application example.
79SKP :=
NA
.
Skip Reclosing Shot (SEL
OGIC
Equation)
Only attempt to reclose Circuit Breaker 1 if the bus is hot and the line is dead
(setting cannot be set to NA or logical 0).
3P1CLS :=
DLLB1
.
Three Pole BK 1 Reclose Supervision (SEL
OGIC
Equation)
Voltage Elements
The SEL-421 checks the Bus and Line conditions when you enable the voltage
check elements.
shows a typical checking scheme. Potentials VAY
and VAX are the default synchronism inputs for V
P
(setting SYNCP) and VS1
(setting SYNCS1), respectively (see
Summary of Contents for SEL-421-4
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