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.
Insulation resistance test standard for transformer.
B kv is the rated machine terminal to terminal voltage.
Clean the terminals of the transformer.
Isolation required for the test.
Insulation resistance test of transformer is divided into three parts.
Value at 60 seconds after application of the test voltage is referred to as the insulation resistance of the transformer at the test temperature.
Adjust megger tester at 1000 v dc.
Ansi neta mts 2015 table 100 11 insulation resistance test values rotating machinery for one minute at 40 c.
Insulation resistance decreases in temperature or moisture.
Values based on ieee std 43 2013.
Leakage current should be as small as possible therby ir value should be as high as possible r v i.
The transformer neutral bushing is to be disconnected from earth during the test.
Measure insulation resistance between low voltage windings and the main body of the 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.
Apply the test voltage and note the reading.
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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.
The megger insulation tester is a small portable instrument that gives you a direct reading of insulation resistance in ohms or megohms.
Use the megger test at a low voltage side.
Apply the test voltage and note the reading.
Steps of this test.
The transformer neutral bushing is to be disconnected from earth during the test.