6.18
SEL-421 Relay Instruction Manual Date Code 20171021
Protection Applications Examples
500 kV Parallel Transmission Lines With Mutual Coupling Example
500 kV Parallel Transmission Lines With Mutual Coupling
Example
Figure 6.3 shows double-ended overhead 500 kV parallel lines with SEL-421
protection at each end of the first circuit. These transmission lines have zero-
sequence mutual coupling. This example explains how to calculate settings for
the SEL-421 at Station S that protects Line 1 in Figure 6.3 between Stations S
and R.
This application example uses communications-assisted tripping with a digital
communications channel to provide high-speed protection for faults along the
500 kV circuit. Distance protection is enabled.
ULTR Unlatch Trip (SELOGIC Equation) TRGTR
ULMTR1 Unlatch Manual Trip – Breaker 1 (SEL
OGIC Equation) NOT (52AA1
AND 52AB1
AND 52AC1)
TOPD Trip During Open Pole Time Delay (2.000–8000 cycles) 2.000
TULO Trip Unlatch Option (1, 2, 3, 4) 3
Z2GTSP Zone 2 Ground Distance Time Delay SPT (Y, N) N
67QGSP Zone 2 Dir. Neg.-Seq./Residual O/C Single Pole Trip (Y, N) N
TDUR1D SPT Minimum Trip Duration Time Delay (2.000–8000 cycles) 6.000
TDUR3D 3PT Minimum Trip Duration Time Delay (2.000–8000 cycles) 9.000
E3PT Three-Pole Trip Enable (SEL
OGIC Equation) 1
E3PT1 Breaker 1 3PT (SEL
OGIC Equation) 1
ER Event Report Trigger (SEL
OGIC Equation) R_TRIG Z2P OR
R_TRIG Z2G OR
R_TRIG 51S1 OR
R_TRIG Z3P OR
R_TRIG Z3G
Main Board (Outputs)
OUT101 (SELOGIC Equation) 3PT
a
Parameter
n
is 1 for BK1, 2 for BK2, and L for Line.
Table 6.6 Settings for 230 kV Overhead TX Example (Sheet 4 of 4)
Setting Prompt Entry
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