Schweitzer Engineering Laboratories SEL-421-4, Instruction Manual

Page: 359 / 1518

6.23
Date Code 20171021 Instruction Manual SEL-421 Relay
Protection Applications Examples
500 kV Parallel Transmission Lines With Mutual Coupling Example
CTRW := 400 .
Current Transformer Ratio—Input W (1–50000)
CTRX := 400 .
Current Transformer Ratio—Input X (1–50000)
PTRY := 4500 .
Potential Transformer Ratio—Input Y (1–10000)
VNOMY := 111 .
PT Nominal Voltage (L–L)—Input Y (60–300 V secondary)
PTRZ := 4500 .
Potential Transformer Ratio—Input Z (1–10000)
VNOMZ := 111 .
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
Table 6.8 for the secondary line impedances.
Z1MAG := 3.98 .
Positive-Sequence Line Impedance Magnitude
(0.05–255

secondary)
Z1ANG := 87.6 .
Positive-Sequence Line Impedance Angle (5.00–90 degrees)
Enter the secondary value of the zero-sequence impedance of the protected line.
Z0MAG := 14.48 .
Zero-Sequence Line Impedance Magnitude
(0.05–255

secondary)
Z0ANG := 82.1 .
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. Set the length in miles.
LL := 75.00 .
Line Length (0.10–999)
The relay fault locator uses the values you enter for Z1MAG, Z1ANG, Z0MAG,
Z0ANG, and LL.
Relay Configuration
You can select from zero to five phase mho (E21P), ground mho (E21MG), and
ground quadrilateral (E21XG) distance zones. You can independently select the
number of zones per type of distance protection. Select only the number of zones
needed. For this application example, use three zones of phase and ground-dis-
tance protection.
E21P := 3 .
Mho Phase-Distance Zones (N, 1–5)
E21MG := 3 .
Mho Ground-Distance Zones (N, 1–5)
E21XG := 3 .
Quadrilateral Ground-Distance Zones (N, 1–5)
Now enable the other logic you will need for this application example.
You do not need CVT transient detection if the SIR (Source Impedance Ratio) is
less than five. SIR is equal to the ratio of the local source impedance to the relay
reach. Calculate the ratio based on the Zone 1 reach because you do not want
Zone 1 distance protection to overreach during an external fault. Double the
source impedance magnitude because the relay measures half the total fault cur-
rent when the parallel line is in service and the fault is located at the remote bus.