6.151
Date Code 20171021 Instruction Manual SEL-421 Relay
Protection Applications Examples
Circuit Breaker Failure Application Examples
Circuit Breaker Failure Application Examples
NOTE: The following discussion
designates Circuit Breaker 1. For
Circuit Breaker 2, replace the 1 with 2.
Under normal operating conditions, local station primary protection operates to
remove faulted equipment from service. Zones of protection are arranged to min-
imize service disruption when local primary protection operates. Backup protec-
tion clears the fault when local protection fails to do so, typically removing more
equipment from service than the primary protection would have removed for a
correct operation.
Protection systems typically employ both local and remote backup protection.
Local backup protection uses dedicated additional equipment to clear a fault if
the local primary protection fails. Remote backup protection consists of overlap-
ping, time-coordinated protection zones situated at remote locations with respect
27BK1P Breaker 1 Dead Busbar Voltage (1.0–200 V secondary) 15.0
59BK1P Breaker 1 Live Busbar Voltage (1.0–200 V secondary) 50.0
27BK2P Breaker 2 Dead Busbar Voltage (1.0–200 V secondary) 15.0
59BK2P Breaker 2 Live Busbar Voltage (1.0–200 V secondary) 50.0
Trip Logic (Group)
E3PT2 Breaker 2 3PT (SELOGIC Equation) NOT LEADBK2
Relay Configuration (Group)
E25BK1 Synchronism Check for Breaker 1 (Y, N, Y1, Y2) N
E25BK2 Synchronism Check for Breaker 2 (Y, N, Y1, Y2) Y
Synchronism-Check Element Reference (Group)
SYNCP Synchronism Reference
(VAY, VBY, VCY, VAZ, VBZ, VCZ)
VAY
25VL Voltage Window Low Threshold
(20.0–200 V secondary)
60.0
25VH Voltage Window High Threshold
(20.0–200 V secondary)
70.0
Breaker 2 Synchronism Check (Group)
SYNCS2 Synchronism Source 2
(VAY, VBY, VCY, VAZ, VBZ, VCZ)
VBZ
KS2M Synchronism Source 2 Ratio Factor (0.10–3) 1.00
KS2A Synchronism Source 2 Angle Shift (0, 30, 60, 90, 120,
150, 180, 210, 240, 270, 300, 330 degrees)
0
ALTS2 Alternative Synchronism Source 2 (SEL
OGIC Equation) NA
25SFBK2 Maximum Slip Frequency—BK2 (OFF, 0.005–0.5 Hz) OFF
ANG1BK2 Maximum Angle Difference 1—BK2 (3.0–80 degrees) 20.0
ANG2BK2 Maximum Angle Difference 2—BK2 (3.0–80 degrees) 20.0
TCLSBK2 Breaker 2 Close Time (1.00–30 cycles) 1.00
BSYNBK2 Block Synchronism Check—BK2 (SEL
OGIC Equation) 52AA2 AND 52AB2
AND 52AC2
a
These settings cannot be set to NA or logical 0.
Table 6.40 Settings for Autoreclose and Synchronism Check Example
(Sheet 3 of 3)
Setting Prompt Entry
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