13-34
Testing and Troubleshooting
Date Code 20011205
SEL-311A Instruction Manual
above. We can then calculate the negative-sequence impedance, Z2c, applied using
Equation 13.1 and compare Z2c to the Z2FT threshold which is a function of the Z2F
setting and Z2m.
(
)
(
)
C
B
2
A
3
1
2
C
B
2
A
3
1
2
I
a
I
a
I
I
V
a
V
a
V
V
×
+
×
+
×
=
×
+
×
+
×
=
(
)
[
]
2
2
2
2
I
*
I
ANG
1
Z
1
V
Re
c
2
Z
×
°
Ð
×
=
Equation
13.1
2
2
I
V
m
2
Z
=
m
2
Z
25
.
0
F
2
Z
25
.
1
FT
2
Z
×
-
×
=
Equation
13.3
Taking the test signals from Table 13.3.
volts
150
V
8
.
46
V
volts
150
V
8
.
46
V
volts
0
V
0
.
67
V
C
B
A
°
Ð
=
°
-
Ð
=
°
Ð
=
(
)
volts
0
3
.
22
V
volts
150
8
.
46
120
1
150
8
.
46
240
1
0
0
.
67
V
2
3
1
2
°
Ð
=
°
Ð
×
°
Ð
+
°
-
Ð
×
°
Ð
+
°
Ð
×
=
Due to the test connections used, I
B
= -I
C
= I
TEST
.
°
Ð
=
°
-
Ð
=
°
Ð
=
03
.
6
A
5
.
2
I
97
.
173
A
5
.
2
I
0
A
0
.
0
I
C
B
A
(
)
amps
03
.
96
44
.
1
I
amps
03
.
6
5
.
2
120
1
97
.
173
5
.
2
240
1
0
0
.
0
I
2
3
1
2
°
Ð
=
°
Ð
×
°
Ð
+
°
-
Ð
×
°
Ð
+
°
Ð
×
=
Using Equation 13.1 to calculate Z2c, the result is:
ohms
47
.
15
c
2
Z
-
=
(
)
(
)
ohms
91
.
2
FT
2
Z
47
.
15
25
.
0
77
.
0
25
.
1
FT
2
Z
ohms
47
.
15
m
2
Z
-
=
×
-
×
=
=
The Z2FT threshold is -2.91
W
. Z2c applied (-15.47
W
) is less than the Z2FT
threshold based upon the Z2F setting (0.77
W
) and Z2m (15.47
W
), therefore, the
32QF element asserts when these signals are applied. If Z2c applied is greater than
the Z2FT threshold, select new test current and voltages using the steps outlined
above.
Step 5.
Turn on the voltage sources. Apply V
A
, V
B
, and V
C
at the magnitudes and angles
listed in Table 13.3. Turn on the current test source. Set the current angle to -174°.
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