How is the Induced Voltage Withstand Test for Transformers conducted?

The Induced Voltage Withstand Test for fully insulated transformers is conducted by opening the high-voltage winding and applying twice the rated voltage at a frequency of 100-250Hz to the low-voltage winding. Due to the higher frequency, the iron core can ensure twice the induced voltage when unsaturated, thereby testing the insulation performance of winding-to-winding, layer-to-layer, and phase-to-phase. This evaluates the longitudinal insulation level of the transformer.

For transformers with graded insulation, raising the neutral point voltage (supporting it) allows the assessment of the main insulation level. Consequently, the Induced Voltage Withstand Test not only tests the longitudinal insulation but also compensates for the inability of such transformers to undergo an External Withstand Voltage Test, effectively performing an equivalent external test.

In the case of a three-phase transformer with graded insulation, the Induced Voltage Withstand Test typically employs a phase-by-phase induction test method. The non-tested two phases (B, C phases in the diagram) are connected in parallel and grounded at the line end, while the neutral point (0) is raised to approximately 1/3 of the test voltage. This ensures that the line end of the test phase (A phase in the diagram) meets the requirements of an External Withstand Voltage Test, and the induced voltage of the test phase winding meets the requirements of the induction test.

If such adjustments cannot meet the test requirements, the tap position can be adjusted, or another transformer can be used as a supporting transformer to support the neutral point.

According to the requirements of the new standard, during the induction test, it is necessary to measure the local discharge quantity as well as the starting and extinguishing voltages of local discharge.

LuShan, est. 1975, is a Chinese professional manufacturer specializing in power transformers and reactors for 49 years. Leading products are single-phase transformer, three-phase transformers, DC inductors, AC reactors, filtering reactor, expoxy resin high-voltage transformer and intermediate, high-frequency products. Our transformers and reactors are widely used in 10 application areas: rapid transit, construction machinery, renewable energy, intelligent manufacturing, medical equipment, coal mine explosion prevention , excitation system, vacuum sintering, central air conditioning.

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