Current Connections - GE MiCOM P40 Agile Technical Manual

P44x/EN CM/Hb6
(CM) 9-42
6.2

Current Connections

Measure the current transformer secondary values for each using a multimeter connected in
series with the corresponding relay current input.
Check that the current transformer polarities are correct by measuring the phase angle
between the current and voltage, either against a phase meter already installed on site and
known to be correct or by determining the direction of the power flow by contacting the
system control centre.
Ensure that the current flowing in the neutral circuit of the current transformers is negligible.
Compare the values of the secondary phase currents and phase angle with the relay's
measured values, which can be found in the MEASUREMENTS 1 menu column.
Note:
If cell [0D02: MEASURE'T SETUP, Local Values] is set to 'Secondary', the currents
displayed on the relay should be equal to the applied secondary current. The relay values
should be within 1% of the applied secondary currents. However, an additional allowance
must be made for the accuracy of the test equipment being used.
If cell [0D02: MEASURE'T SETUP, Local Values] is set to 'Secondary', the currents
displayed on the relay should be equal to the applied secondary current multiplied by the
corresponding current transformer ratio set in the 'VT & CT RATIOS' menu column. Again
the relay values should be within 1% of the expected value, plus an additional allowance for
the accuracy of the test equipment being used.
Under normal load conditions the earth fault function will measure little, if any, current.
It is therefore necessary to simulate a phase to neutral fault. This can be achieved by
temporarily disconnecting one or two of the line current transformer connections to the
relay and shorting the terminals of these current transformer secondary windings.
Commissioning
MiCOM P40 Agile P442, P444