P.3.322
SEL-411L Relay Protection Manual Date Code 20151029
Protection Functions
Protection Application Examples
Use the positive-sequence shunt susceptance and nominal line voltage to
calculate the steady-state charging current.
Equation 3.106
Equation 3.107
Dividing by the largest CT primary, we obtain the following:
Equation 3.108
Charging current compensation is not necessary because this value is
significantly less than the typical minimum pickup of the current differential.
We would have the following at both terminals:
E87LCC := N Enable Line Charging Current Compensation (Y,N)
Enable two mho phase and ground distance zones for backup protection.
The SIR that Relay S sees for a fault at the Zone 1 (80 percent of the line)
reach will be as follows:
Equation 3.109
This value is less than 5, so CVT transient detection is not necessary.
Use common time delays to reduce the likelihood of a timer reset during an
evolving fault. Set separate phase and ground time delays to OFF.
We would have the following at both terminals:
E21MP := 2 Mho Phase Distance Zones (N, 1–5)
E21MG := 2 Mho Ground Distance Zones (N, 1–5)
ECVT := N CVT Transient Detection (Y, N)
ECDTD := Y Distance Element Common Time Delay (Y, N)
Enable SOTF, out-of-step blocking, load encroachment, single-phase
instantaneous overcurrent (for SOTF), and loss-of-potential. Disable all other
functions.
We would have the following at both terminals:
ESOTF := Y Switch-Onto-Fault (Y, N)
EOOS := Y Out-of-Step (Y, Y1, N)
ELOAD := Y Load Encroachment (Y, N)
E50P := 1 Phase Inst./Def.-Time O/C Elements (N, 1–4)
E50G := N Res. Ground Inst./Def.-Time O/C Elements (N, 1–4)
E50Q := N Neg.-Seq. Inst./Def.-Time O/C Elements (N, 1–4)
E51 := N Enable Inverse-Time Overcurrent Elements (N, 1–10)
E81 := N Enable Frequency Elements (N, 1–6)
E27 := N Enable Under Voltage Elements (N, 1–6)
E59 := N Enable Over Voltage Elements (N, 1–6)
I
CH
V
Nominal ph n–
Line Length B1L• • =
I
CH
500 kV
3
------------------ 70 mi 0.009•
mS
mi
-------- 182 A primary=• =
I
CH
182 A
2000 A
------------------ 0.091 per unit==
SIR
Z1S
0.8 Z1L•
----------------------------
3.556
0.8 2.514•
--------------------------- 1.78===
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