Schweitzer Engineering Laboratories SEL-311A, Инструкция по эксплуатации, Страница: 369 / 476

Date Code 20011205 Testing and Troubleshooting 13-33
SEL-311A Instruction Manual
ondary sec volts 8 . 46 V
36 . 9 • 0 . 5 V
Z • I V
BC
BC
BC BC BC
=
=
=
Equation 13.7
Refer to Figure 13.8 and use the equations below to calculate the magnitude and
angle of V
B
and V
C
based upon the magnitude of V
BC
calculated above.
Figure 13.8: Phase Distance Element Test Voltage Signals
When the magnitude of V
BC
calculated above lies between 67 and 35 volts, use
b
=
150° and
│
V
B
│
=
│
V
C
│
=
│
V
BC
│
.
When the magnitude of V
BC
calculated above is greater than 67 volts, use
│
V
B
│
=
│
V
C
│
= 67 V. Calculate the angle
b
using Equation 13.8.
When the magnitude of V
BC
calculated above is less than 35 volts, use
│
V
B
│
=
│
V
C
│
= 35 V. Calculate the angle
b
using Equation 13.8.
( )
[ ]
deg V • 2 / V sin a 180
C BC
- ° = b
Equation 13.8
Select V
A
= 67
Ð
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
° Ð =
° - Ð =
° Ð =
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-311A 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