13.50
SEL-311C Relay Instruction Manual Date Code 20060320
Testing and Troubleshooting
Test Procedures
Step 13. Calculate the magnitude and angle of negative-sequence
voltage and current applied for the test quantities listed above.
Then calculate the negative-sequence impedance, Z2c, applied
through use of Equation 13.76.
Equation 13.75
Equation 13.76
Equation 13.77
Equation 13.78
Taking the test signals from Table 13.7:
V
A
= 40.4 V ∠0°
V
B
= 67.0 V ∠–120°
V
C
= 67.0 V ∠120°
Equation 13.79
I
A
= 2.49 A ∠–90.0°
I
B
= 0.0 A ∠0.0°
I
C
= 0.0 A ∠0.0°
Equation 13.80
Through use of Equation 13.76 to calculate Z2c, we obtain the
following result:
Equation 13.81
The relay example Z2F setting is 0.77 Ω. The value of Z2c
applied (–10.84 Ω) is less than the Z2FT threshold (–4.46 Ω),
so the 32GF element asserts when these signals are applied. If
Z2c applied is greater than the Z2FT setting, select new test
current and voltages through performance of the steps outlined
above.
V
2
1
3
---
V
A
a
2
V
B
aV
C
• +• +()• =
I
2
1
3
---
I
A
a
2
I
B
aI
C
• +• +()• =
Z2c
Re V
2
1 Z1ANG°∠ I
2
• ()*• []
I
2
2
----------------------------------------------------------------------------=
Z2m
V
2
I
2
---------=
Z2FT 1.25 Z2F 0.25 Z2m• –• =
V
2
1
3
---
40.4 0° 1240° 67.0 120°–1120° 67.0 120°∠• ∠+∠• ∠+∠()volts• =
9.0 180°volts∠=
I
2
1
3
---
2.49 90.0°–∠()amps• =
0.83 90.0°amps–∠=
Z2c 10.84 ohms–=
Z2m 10.84ohms=
Z2FT 1.25 0.77()0.25 10.84()• –• =
Z2FT –4.46 ohms=
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