Schweitzer Engineering Laboratories SEL-421-4 - Page 497

6.161
Date Code 20171021 Instruction Manual SEL-421 Relay
Protection Applications Examples
Circuit Breaker Failure Application Examples
Circuit Breaker Failure Protection—Example 2
Use the SEL-421 to provide circuit breaker failure protection for both circuit
breakers in breaker-and-a-half schemes. This application example explains set-
ting the relay for Circuit Breaker BK1 (see Figure 6.45). You can apply these
same settings for Circuit Breaker BK2. You can apply circuit breaker failure
Scheme 2 protection for single-pole trip circuit breakers. Scheme 2 provides sep-
arate timers for multiphase faults (BFPU1) and single-phase faults (SPBFPU1).
For more information on Scheme 2 circuit breaker failure protection, see Failure
to Interrupt Fault Current: Scheme 2 on page 5.148.
NOTE: This application example is
for two circuit breakers. Apply the
same settings for Circuit Breaker BK2
as for Circuit Breaker BK1. For Circuit
Breaker BK2, substitute 2 for 1 in the
following settings.
This example uses a 500 kV power system with single-pole tripping enabled (see
Figure 6.45). Table 6.43 provides the power system parameters.
Breaker 1 Failure Logic (Group)
50FP1 Phase Fault Current Pickup—BK1 (0.50–50 A secondary) 5.94
BFPU1 Breaker Failure Time Delay—BK1 (0.000–6000 cycles) 10.000
RTPU1 Retrip Time Delay—BK1 (0.000–6000 cycles) 4.000
BFI3PI Three-Pole Breaker Failure Initiate—BK1 (SEL
OGIC Equation) 3PT
BFIA1 A-Phase Breaker Failure Initiate—BK1 (SEL
OGIC Equation) NA
BFIB1 B-Phase Breaker Failure Initiate—BK1 (SEL
OGIC Equation) NA
BFIC1 C-Phase Breaker Failure Initiate—BK1 (SEL
OGIC Equation) NA
BFIDO1 Breaker Fail Initiate Dropout Delay—BK1 (0.000–1000 cycles) 0.000
BFISP1 Breaker Fail Initiate Seal-In Delay—BK1 (0.000–1000 cycles) 0.000
ENCBF1 No Current/Residual Current Logic—BK1 (Y, N) Y
50RP1 Residual Current Pickup—BK1 (0.25–50 A secondary) 0.74
NPU1 No Current Breaker Failure Delay—BK1 (0.000–6000 cycles) 12.000
BFIN1 No Current Breaker Failure Initiate—BK1 (SEL
OGIC Equation) NA
ELCBF1 Load Current Breaker Failure Logic—BK1 (Y, N) N
EFOBF1 Flashover Breaker Failure Logic—BK1 (Y, N) N
BFTR1 Breaker Failure Trip—BK1 (SEL
OGIC Equation) FBF1 OR
NBF1
BFULTR1 Breaker Failure Unlatch Trip—BK1 (SEL
OGIC Equation) IN104
Main Board (Outputs)
OUT101 3PT
OUT103 RT1
OUT107 BFTRIP1
Table 6.42 Settings for Circuit Breaker Failure Example 1 (Sheet 2 of 2)
Setting Prompt Entry