How to Megger a Transformer

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Insulation tests rest primarily on the overall condition of the electrical equipment used to conduct the test. Dust, grime, humidity, oil, corrosion, vibration, electrical surges, mechanical pulls and lugging and other stressors contribute to the insulation's life expectancy, usually a slow and steady decline over time. The breakdown of insulation jeopardizes the remaining life of the electrical equipment it once protected. Insulation measurements allow the operator to assess the test item's resistance-to-time graph, which details the overall condition of the item. The operator can take the necessary steps to correct any discrepancies. Only trained and suitably competent individuals should use a Megger insulation tester.

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Be sure to free the Megger testing instrument's "test" button from its locking mechanism, establishing a connection with the test item, a transformer in this case.

Program the selector switch to meet the test voltage requirement. Attach the test lead connectors to the Megger testing instrument, then to the test item. Be sure to isolate the transformer before attaching the lead connectors.

Press the "test" button to activate the preset test voltage. Release the "test" button after completing the reading. Evaluate and record the insulation measurements provided from the reading. Note that the capacitive circuits charged while performing a test will automatically discharge without manual intervention. Note that "live circuit warning" displays if voltage remains after completing the test. Observe the safety delay default during the first three seconds on the first operation reading within the 1,000 volt range.

Remove the test lead connectors once the voltage clears.

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