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6.4
SEL-421 Relay
Instruction Manual
Date Code 20171021
Protection Applications Examples
230 kV Overhead Distribution Line Example
Breaker Monitor
Circuit Breaker Configuration
Set the relay to indicate that Circuit Breaker 1 is a three-pole trip circuit breaker.
BK1TYP :=
3
.
Breaker 1 Trip Type (Single-Pole = 1, Three-Pole = 3)
Circuit Breaker 1 Inputs
The SEL-421 uses a normally open auxiliary contact from the circuit breaker to
determine whether the circuit breaker is open or closed.
52AA1 :=
IN101
.
A-Phase N/O Contact Input -BK1 (SEL
OGIC
Equation)
Group Settings
Line Configuration
The SEL-421 has four transformer turns ratio settings that convert the secondary
potentials and currents that the relay measures to the corresponding primary val-
ues. These settings are the potential transformer and current transformer ratios
PTRY, PTRZ, CTRW, and CTRX.
Use the Y potential input for line relaying and the Z potential input for synchro-
nism check. Use the W current input for line relaying. The settings VNOMY and
VNOMZ specify the nominal secondary line-to-line voltage of the potential
transformers (see
).
CTRW :=
100
.
Current Transformer Ratio—Input W (1–50000)
PTRY :=
2000
.
Potential Transformer Ratio—Input Y (1–10000)
VNOMY :=
115
.
PT Nominal Voltage (L-L)—Input Y (60–300 V secondary)
PTRZ :=
2000
.
Potential Transformer Ratio—Input Z (1–10000)
VNOMZ :=
115
.
PT Nominal Voltage (L-L)—Input Z (60–300 V secondary)
Enter the secondary value of the positive-sequence impedance of the protected
line. See
for the secondary line impedances.
Z1MAG :=
1.95
.
Positive-Sequence Line Impedance Magnitude
(0.05–255
secondary)
Z1ANG :=
84.00
.
Positive-Sequence Line Impedance Angle (5.00–90 degrees)
Enter the secondary value of the zero-sequence impedance of the protected line.
Z0MAG :=
6.20
.
Zero-Sequence Line Impedance Magnitude
(0.05–255
secondary)
Z0ANG :=
81.50
.
Zero-Sequence Line Impedance Angle (5.00–90 degrees)
Enable the fault locator.
EFLOC :=
Y
.
Fault Location (Y, N)
The LL setting is the line length. This value has no defined unit; you can set the
line length in miles, kilometers, ohms, etc. For this example, set the length in
miles.
LL :=
50
.
Line Length (0.10–999)
Summary of Contents for SEL-421-4
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