Schweitzer Engineering Laboratories SEL-311C - Page 498

13.44
SEL-311C Relay Instruction Manual Date Code 20060320
Testing and Troubleshooting
Test Procedures
angle of Z2MG is equal to the angle of positive-sequence
impedance, Z1ANG.
Because the element under test is not a Zone 1 element, the k0
value is defined by the relay settings k0M and k0A. When you
test the relay Zone 1 ground elements, use k01M and k01A to
define the magnitude and angle of k0.
Step 12. Calculate the value of Z
AG
•(1 + k0) based upon the information
above.
Equation 13.54
I
A
must lag V
A
by the angle of Z
TEST
to check the maximum
reach of the element under test. With V
A
applied at an angle of
0°, the angle of I
A
is:
Equation 13.55
Step 13. Calculate the magnitude of V
A
through use of Equation 13.56.
Equation 13.56
Step 14. Select V
B
= 67 ∠–120° volts and V
C
= 67 ∠120° volts.
With the above settings, the ground distance elements are
supervised by the negative-sequence directional element. It is
important to check the negative-sequence quantities applied
and verify that the 32GF element should assert, allowing the
forward-reaching distance element to operate.
Step 15. Calculate the magnitude and angle of negative-sequence
voltage and current applied for the test quantities listed above.
Step 16. Calculate the negative-sequence impedance, Z2c, applied
through use of Equation 13.58 and compare Z2c to the Z2FT
threshold that is a function of the Z2F setting and Z2m.
Equation 13.57
Equation 13.58
Equation 13.59
Z
AG
1k0+()• Z
TEST
Z2MG 1 k0M k0A∠+()• ==
Z
TEST
9.36 83.97° 1 0.726 3.69°–∠+()• ∠=
9.36 83.97° 1.725 1.55°–∠()• ∠=
16.15 82.42°∠=
I
A
2.5 82.42– °∠=
V
A
I
A
Z
TEST
• =
2.5 82.42° 16.15 82.42°∠• –∠=
40.4 0.0°volts secondary∠=
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
---------=