13.43
Date Code 20060320 Instruction Manual SEL-311C Relay
Testing and Troubleshooting
Test Procedures
Equation 13.49
so:
Equation 13.50
With a 50QF setting of 0.5 amps, 50QF picks up when I
TEST
is
greater than 0.5 amps.
Step 11. Select the magnitude of I
A
greater than the 50L2, 50GZ2, and
50QF settings, but less than the maximum current output
capability of the current test source.
In this example, select |I
TEST
| = 2.5 amps. This selection fulfills
the supervisory overcurrent conditions described above.
The reach of the distance element under test in secondary ohms
is defined by the element setting. In this case, Z2MG = 9.36 Ω.
The impedance measured by the relay for a ground fault is
determined by the faulted phase voltage, faulted phase current,
and the residual current multiplied by the zero-sequence
current compensation factor, k0. The SEL-311C uses k0M1
and k0A1 settings to define the zero-sequence current
compensation factor for Zone 1 ground distance elements.
When the advanced user settings are not enabled (EADVS =
N), the remaining zone settings, k0M and k0A, follow k0M1
and k0A1. The impedance measured by the relay ground mho
distance element for a Zone 2 fault is defined by the following
equation:
Equation 13.51
For a fault on a radial system and when testing a ground
distance element using a single current source, I
A
= I
R
. In this
case, Equation 13.51 can be simplified:
Equation 13.52
If we multiply both sides of Equation 13.52 by the quantity
(1 + k0), the result is the impedance applied by the A-phase test
signals, V
A
and I
A
.
Equation 13.53
Because we are testing the Zone 2 mho ground distance
element, the intended value of Z
AG
= Z2MG = 9.36 Ω. The
where:
k0 = k0M ∠k0A°
I
2
1
3
---
I
A
a
2
I
B
aI
C
• +• +()• =
3I•
2
I
A
a
2
I
B
aI
C
• +• +()=
I
A
I
TEST
and I
B
I
C
0===
3I
2
• I
TEST
=
Z
AG
V
A
I
A
k0 I
R
• +
------------------------------=
Z
AG
V
A
I
A
1k0+()•
--------------------------------=
Z
AG
1k0+()•
V
A
I
A
--------=
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