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7-36
Maintenance and Testing
Date Code 20011026
SEL-321/321-1 Instruction Manual
When the magnitude of V
BC
calculated above is greater than 67 volts, use
│
V
B
│
=
│
V
C
│
= 67 V. Calculate the angle
β
using Equation 7.9.
When the magnitude of V
BC
calculated above is less than 35 volts, use
│
V
B
│
=
│
V
C
│
= 35 V. Calculate the angle
β
using Equation 7.9.
(
)
[
]
deg
V
•
2
/
V
sin
a
180
C
BC
−
°
=
β
Equation
7.9
Select V
A
= 67
∠
0° volts. For the Zone 2 B-C element test, based upon the example
settings, the magnitude of V
BC
equals 46.8 volts. From the equations above, select
the following test voltage magnitudes and angles.
volts
150
8
.
46
V
volts
150
8
.
46
V
volts
0
0
.
67
V
C
B
A
°
∠
=
°
−
∠
=
°
∠
=
The phase distance element maximum reach is measured when faulted phase-to-
phase current lags faulted phase-to-phase voltage by the distance element maximum
torque angle. In the SEL-321 Relay, the phase distance element maximum torque
angle is defined by the angle of the relay Z1ANG setting.
For the example relay settings, I
BC
should lag V
BC
by 83.97°. Based upon the test
voltages selected above, V
BC
lags V
A
by 90°, so I
BC
should lag V
A
by 173.97°.
As stated above, the phase distance elements are supervised by the negative-
sequence directional element. It is important to check the negative-sequence
quantities applied and verify that the 32QF element should assert allowing the
forward-reaching distance element to operate. We can calculate the magnitude and
angle of negative-sequence voltage and current applied for the test quantities listed
above. We can then calculate the negative-sequence impedance, Z2c, applied using
Equation 7.2 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
⋅
°
∠
⋅
=
Equation
7.2
2
2
I
V
m
2
Z
=
m
2
Z
25
.
0
F
2
Z
25
.
1
FT
2
Z
⋅
−
⋅
=
Equation
7.4
Taking the test signals from Table 7.3.
volts
150
V
8
.
46
V
volts
150
V
8
.
46
V
volts
0
V
0
.
67
V
C
B
A
°
∠
=
°
−
∠
=
°
∠
=
Содержание SEL-321
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Страница 78: ...2 54 Specifications Date Code 20011026 SEL 321 321 1 Instruction Manual Figure 2 4 Logic Symbol Legend ...
Страница 87: ...Date Code 20011026 Specifications 2 63 SEL 321 321 1 Instruction Manual Figure 2 21 Load Encroachment Logic ...
Страница 94: ...2 70 Specifications Date Code 20011026 SEL 321 321 1 Instruction Manual Figure 2 29 Voltage Element Logic ...
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Страница 171: ...Date Code 20011026 Event Reporting 4 9 SEL 321 321 1 Instruction Manual ...
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