Schweitzer Engineering Laboratories SEL-311A, Instruction Manual

Page: 359 / 476

Date Code 20011205 Testing and Troubleshooting 13-23
SEL-311A Instruction Manual
Step 3. Connect the voltage source to the A-phase to neutral relay voltage input. Connect
the current source to the A-phase relay current input. Refer to the A-phase voltage
and current connections shown in Figure 13.5 as an example. The B-phase and C-
phase voltage connections are not required for this test.
Step 4. As described above, the relay 32Q element operates based upon the magnitude and
angle of negative-sequence voltages and currents. You can calculate the magnitude
and angle of V
2
and I
2
, given the magnitude and angle of each of the phase quantities
using the equations below.
( )
( )
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
+ + =
+ + =
Using single-phase signals simplifies the V
2
and I
2
calculations.
( )
( )
A
3
1
2
A
3
1
2
C B
C B
I • I
V • V
amps 0 I I
volts 0 V V
=
=
= =
= =
Assume that you apply a test voltage V
A
= 18.0
Ð
180
°
volts secondary.
( )
volts 180 0 . 6 V
volts 180 0 . 18 • V
2
3
1
2
° Ð =
° Ð =
Determine the test angle of A-phase current from the Z1ANG relay setting. Equation
13.1 yields a positive result when I
2
lags V
2
by the angle of Z1ANG°. Equation 13.1
yields a negative result when I
2
leads V
2
by (180° -
Ð
Z1ANG°).
We are testing for positive values of Z2c, so I
2
should lag V
2
by Z1ANG.
Assuming that V
A
= 18.0
Ð
180° volts, the angle of I
A
for this test should be 96°.
Determine the magnitude of A-phase current where Z2 equals Z2R or Z2F using
Equation 13.6:
( )
2 2 A
Z / V • 3 I
=
Equation 13.6
For Z2R = 5.45
W
:
( )
amps 3 . 3 I
ohms 45 . 5 volts 0 . 6 • 3 I
A
A
=
=
Calculate Z2m:
ohms 45 . 5 m 2 Z
A 1 . 1
V 0 . 6
m 2 Z
I
V
m 2 Z
2
2
=
=
=
Because Z2R is positive, use Equation 13.4 to calculate Z2RT.