Measurement of no load losses and no load current
- Characterising the no load losses and the no load current of the transformer
- Checking that the characteristics are in conformity with the current standard
In real terms, no load losses are generated by the area marked within the dotted line below :
The low voltage (LV) winding is supplied with the rated voltage at the rated frequency, with the medium voltage (MV) winding open-circuited.
A three-phase precision wattmeter is used for measurements and gives directly :
- the applied voltage (true r.m.s.)
- the 3 currents (true r.m.s.)
- the average current
- the no load losses
NOTE: the values measured on transformers with several LV windings are obtained on the winding with the highest voltage, in other words the one offering the best accuracy.
Test rig diagram
Voltmeters and ammeters integrated on the test rig enable the values to which the transformer is subjected to be measured at any point in time.
The application of small tolerances on the no load losses is negotiable at the time of the request for tender.
|Title:||Test Guide for Cast Resin Dry Type Transformer ‘TRIHAL’ – Schneider Electric|
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many thanks for such useful information I have transmission lines by sf6 gases .
A customer made a measurement for windings resistance on a 20/0.4 kV 1000 kV trafo, with an microohm meter (μΩ). Do you thing is valid? Thank you, nice info everytime !
It is not correct to measure the winging resistance of higher capacity transformers with micro ohmmeter. Use winding resistance kit. If at all to use microohm meter, first connect only the current circuit leads and connect the voltage circuit leads after some seconds of time and allow the reading to settle for almost fixed reading.
Many Thanks for such useful information