The AC withstand voltage test of the transformer is a test in which a sinusoidal power frequency AC test voltage exceeding a certain multiple of the rated voltage is applied to the tested transformer winding together with the bushing, and the duration is 1min. The purpose is to use a test voltage higher than a certain multiple of the rated voltage to replace the atmospheric overvoltage and internal overvoltage to assess the insulation performance of the transformer. It is the most effective way to identify the insulation strength of the transformer, and it is also an important experimental project to ensure the safe operation of the transformer and avoid the occurrence of insulation accidents. The AC withstand voltage test can find the main insulation of the transformer is damp and concentrated defects, such as cracking of the main insulation of the windings, loose windings Defects such as displacement, lead insulation distance is insufficient, and dirt is attached to the insulation. The AC withstand voltage test is a destructive test in the insulation test. It must be carried out after other non-destructive tests (such as insulation resistance and absorption ratio test, DC leakage test, dielectric loss correction and insulating oil test) are qualified. . After this test is passed, the transformer can be put into operation. The AC withstand voltage test is a key test, Therefore, the preventive test regulations stipulate that transformers with 10kV and below should be tested for AC withstand voltage after 1~5 years, 66kV and below after overhaul, after replacing windings and when necessary.
HV HIPOT GDTF series Frequency resonant Test Set
Experiment method
(1) Wiring
External AC withstand voltage test wiring for small and medium-sized power transformers below 35kV. All windings should be tested. During the test, the lead wires of each phase winding should be short-circuited together. If there is a lead wire at the neutral point, the lead wire should also be short-circuited with the three-phase.
(2) Voltage Testing
The handover test standard stipulates that the transformer whose capacity is below 8000kV and whose winding rated voltage is below 110kV should be subjected to AC withstand voltage test according to the test voltage standard listed in Appendix I of the standard.
The preventive test regulations stipulate: the test voltage value of oil-immersed transformers is detailed in the regulations table (regular test replaces the winding voltage value according to the part). When all the windings of the dry-type transformer are replaced, the voltage value of the factory test shall be used; when the windings of the dry-type transformer are partially replaced and periodically tested, the voltage value of the factory test shall be 0.85 times.
Post time: Jun-27-2022