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P54A/B/C/E
If the Local Values cell is set to Secondary, the values displayed should be equal to the applied secondary
voltage. The values should be within 1% of the applied secondary voltages. However, an additional allowance must
be made for the accuracy of the test equipment being used.
If the Local Values cell is set to Primary, the values displayed should be equal to the applied secondary voltage
multiplied the corresponding voltage transformer ratio set in the CT & VT RATIOS column. The values should be
within 1% of the expected values, plus an additional allowance for the accuracy of the test equipment being used.
15.3
MEASURE CAPACITIVE CHARGING CURRENT
1.
With the feeder energised from one end only, compare the local and remote measured currents in the
MEASUREMENTS 3 column to confirm that the feeder capacitive charging current is similar to that expected
on all three phases.
2.
Check that GROUP 1 CURRENT DIFF > Phase Is1 is set higher than 2.5 times the capacitive charging current.
If this is not the case, notify those concerned of the setting required to ensure stability under normal
operating conditions.
15.4
CHECK DIFFERENTIAL CURRENT
With the feeder supplying load current, check that the measurements in the MEASUREMENTS 3 column are as
expected and that the differential current is similar to the value of capacitive charging current previously
measured for all.
15.5
CHECK CURRENT TRANSFORMER POLARITY
The load current should be high enough to be certain that the main current transformers are connected with the
same polarity to each device in the group. On cable circuits with high line capacitance, it is possible that the load
current could be masked by the capacitive charging current.
1.
If necessary reverse the connections to the main current transformers and check that the 'A' current
differential in MEASUREMENTS 3 > IA Differential cell is significantly higher than for the normal connection.
If the differential current falls with the connection reversed, the main current transformers may not be
correct and should be thoroughly checked.
2.
Repeat the test for phases B and C using the IB Differential and IC Differential cells respectively.
15.6
ON-LOAD DIRECTIONAL TEST
This test ensures that directional overcurrent and fault locator functions have the correct forward/reverse
response to fault and load conditions. For this test you must first know the actual direction of power flow on the
system. If you do not already know this you must determine it using adjacent instrumentation or protection
already in-service.
For load current flowing in the Forward direction (power export to the remote line end), the A Phase Watts
●
cell in the MEASUREMENTS 2 column should show positive power signing.
●
For load current flowing in the Reverse direction (power import from the remote line end), the A Phase
Watts cell in the MEASUREMENTS 2 column should show negative power signing.
Note:
This check applies only for Measurement Modes 0 (default), and 2. This should be checked in the MEASURE'T SETUP column
(Measurement Mode = 0 or 2). If measurement modes 1 or 3 are used, the expected power flow signing would be opposite to
that shown above.
In the event of any uncertainty, check the phase angle of the phase currents with respect to their phase voltage.
P54xMED-TM-EN-1
Chapter 20 - Commissioning Instructions
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Troubleshooting
