What Are the Transformer Test Procedures?


Quick Answer

Testing procedures for transformers include general inspection, resistance measurements, temperature rise testing, load loss and impedance testing. Equipment necessary to perform these tests include a polarity test kit, multimeter, ohmmeter and autotransformers.

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Full Answer

General inspection of transformers entails checking compliance of the device with the manufacturer's manuals and drawing, assessing nameplate ratings and terminal markings, and ensuring that HV and LV cable connections are tight enough. It also involves checking the oil levels and inspecting for leakage.

The electrical check procedure includes troubleshooting equipment grounding, reviewing fuse ratings on the secondary side of the transformer and performing insulation resistance, polarity and transformer turns ratio tests. Insulation resistance tests verify that the correct conductor size is in place and that the contact resistance is within acceptable limits. This test takes place at a predetermined temperature at least 24 hours after oiling.

During the load loss and impedance testing procedure, electricians apply a voltage to the high voltage side of the transformer and gradually increase this voltage while shorting connections on the low voltage side to achieve a full load operation. This procedure helps in calculating the actual load loss and impedance voltage. The insulator power factor test involves the use of a capacitance bridge to measure capacitance between transformer windings and the ground. Engineers compare these measurements to those taken during previous routine maintenance tests to detect deterioration of the insulation structure of the transformer.

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