13.42
SEL-311C Relay Instruction Manual Date Code 20060320
Testing and Troubleshooting
Test Procedures
Step 9. Connect the current source to the A-phase relay current input.
Refer to the voltage and current connections shown in
Figure 13.5 as an example.
Step 10. Select the magnitude of the test signals, I
A
and V
A
.
Table 13.6 summarizes the test quantities for the Zone 2 A-G
ground distance element based upon the example relay settings.
The following text describes a hand calculation method you can
use to calculate relay distance element voltage and current test
signals. If you do not want to review this information, go to
Step 17.
The relay ground distance elements operate based upon the
magnitude of applied phase-ground impedance. The impedance
calculation is supervised by the functions described. To
effectively test the distance elements, select test signals that
fulfill the impedance and supervisory requirements of the relay,
but are within the ability of the test sources to produce
accurately.
The Zone 2 ground distance element is forward reaching. Thus,
it is supervised by the forward directional element 32GF, as
well as the 50L2 and 50GZ2 phase and residual overcurrent
elements. Applied phase current must exceed the 50L2 setting,
applied residual current must exceed the 50GZ2 setting, and
applied 3I
2
must exceed the 50QF setting.
The 50L overcurrent elements operate based upon the
magnitude of the phase current. Using the current connections
shown in Figure 13.5, the magnitude of I
A
is equal to the
magnitude of the applied test current. With a 50L2 setting of
0.50 amps, 50L2 picks up when I
TEST
is greater than 0.90
amps.
The 50GZ overcurrent elements operate based upon the
magnitude of the residual current. Using the current
connections shown in Figure 13.5, the magnitude of I
R
is equal
to the magnitude of the applied test current, I
A
. With a 50GZ2
setting of 0.50 amps, 50G2 picks up when I
TEST
is greater than
0.50 amps.
The 50QF negative-sequence overcurrent element operates
based upon the magnitude of 3I
2
applied. Using the current
connections shown in Figure 13.5, we can calculate the
magnitude of 3I
2
applied based upon the magnitude of I
TEST
.
Table 13.6 Test Quantities for Zone 2 Ground Mho Distance Element
Test Vo l tages Te s t Cur re n t
V
A
= 40.4 ∠0° volts I
TEST
= 2.5 ∠ –82.42° amps
V
B
= 67.0 ∠–120° volts
V
C
= 67.0 ∠120° volts
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