Insulation Resistance Test Standard For Transformer

A rated line to line voltage for three phase ac machines line to ground voltage for single phase machines and rated direct voltage for dc machines or field windings.

Insulation resistance test standard for transformer.

Value at 60 seconds after application of the test voltage is referred to as the insulation resistance of the transformer at the test temperature. Insulation resistance is the ratio of the applied voltage dc to the total leakage current. Apply the test voltage and note the reading. Insulation resistance decreases in temperature or moisture.

Adjust megger tester at 1000 v dc. Isolation required for the test. Value at 60 seconds after application of the test voltage is referred to as the insulation resistance of the transformer at the test temperature. Measure insulation resistance between low voltage windings and the main body of the transformer.

Leakage current should be as small as possible therby ir value should be as high as possible r v i. Ansi neta mts 2015 table 100 11 insulation resistance test values rotating machinery for one minute at 40 c. The transformer neutral bushing is to be disconnected from earth during the test. Apply the test voltage and note the reading.

Insulation resistance test of transformer is divided into three parts. Steps of this test. Clean the terminals of the transformer. Ieee guide for short circuit testing of distribution and power transformers csa standard can csa c88 m90 csa standard for power transformers and reactors 6 routine design other remark oil quality tests x quality resistance measurement x quality winding insulation resistance x quality core clamp insulation resistance x quality ratio test x.

This test can be repeated during the service life of the transformer and verified against the result obtained during manufacturing as a check to determine if the insulation is malfunctioning or decaying. The test is performed with a power factor test kit and the connections are the same as for the megger test the insulation resistance test. Use the megger test at a low voltage side. With a little record keeping and common sense however you can get a good picture of the insulation condition from values that are only relative.

Values based on ieee std 43 2013.