Schweitzer Engineering Laboratories SEL-421-4 - Page 360

6.24
SEL-421 Relay Instruction Manual Date Code 20171021
Protection Applications Examples
500 kV Parallel Transmission Lines With Mutual Coupling Example
Equation 6.8
ECVT := N. CVT Transient Detection (Y, N)
NOTE: The SEL-421-4 does not
provide series-compensated line
protection logic.
The transmission line is not series compensated.
ESERCMP := N. Series-Compensated Line Logic (Y, N)
You can select a common time delay or an independent time delay per zone for
phase and ground-distance protection. If you choose independent timing, evolv-
ing faults (such as those changing from single phase to multiphase) cause the
timer to reset and result in additional delay. Select common time delay for this
application.
ECDTD := Y. Distance Element Common Time Delay (Y, N)
The SOTF logic permits tripping by specified protection elements for a settable
time after the circuit breaker closes.
ESOTF := Y. Switch-Onto-Fault (Y, N)
Do not enable the Out-of-Step logic for this application example.
EOOS : = N. Out-of-Step (Y, N)
Do not enable the load-encroachment logic, as the minimum apparent load
impedance is outside the mho phase-distance characteristics.
ELOAD := N. Load Encroachment (Y, N)
Use Level 1 high-set instantaneous phase overcurrent element for SOTF
protection.
E50P := 1. Phase Instantaneous/Definite-Time Overcurrent Elements (N, 1–4)
This application does not require residual ground overcurrent protection.
E50G := N. Residual Ground Instantaneous/Definite-Time Overcurrent Ele-
ments (N, 1–4)
This application does not require negative-sequence overcurrent protection.
E50Q := N. Negative-Sequence Instantaneous/Definite-Time Overcurrent Ele-
ments (N, 1–4)
Use inverse-time overcurrent protection to provide backup protection for high-
resistance ground faults. The 51S1 element provides backup protection for unbal-
anced faults if both the communications-assisted and step distance protection fail
to operate.
E51S := 1. Selectable Inverse-Time Overcurrent Element (N, 1–3)
Set E32 to AUTO or AUTO2 and the relay automatically calculates the settings
corresponding to the ground directional element (32G).
E32 := AUTO2. Directional Control (Y, AUTO, AUTO2)
SIR
2Z
1S
•
0.8 Z
1L
•
--------------------------=
2 • 4.45 
0.8 • 3.98 
------------------------------=
2.76, SIR 5=