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NK Transformers

Transformer Oil Breakdown Voltage Testing Services


To assess the insulating property of dielectric transformer oil, a sample of the transformer oil is taken and its break down voltage is measured. The lower the resulting breakdown voltage, the poorer the quality of the transformer oil.

  • The transformer oil is filled in the vessel of the testing device. Two standard-compliant test electrodes with a typical clearance of 2.5 mm are surrounded by the dielectric oil.
  • A test voltage is applied to the electrodes and is continuously increased up to the breakdown voltage.
  • At a certain voltage level breakdown occurs in an electric arc, leading to a collapse of the test voltage.
  • An instant after ignition of the arc, the test voltage is switched off automatically by the testing device.
  • The transformer oil testing device measures and reports the root mean square value of the breakdown voltage.
  • After the transformer oil test is completed, the insulation oil is stirred automatically and the test sequence is performed repeatedly: typically 5 repetitions, depending on the standard.
  • As a result the breakdown voltage is calculated as mean value of the individual measurements.

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