Dry-type transformer withstand voltage test

The external withstand voltage test is a test in which a labor frequency high voltage is applied to the tested dry-type transformer for 1 minute, which is also called a labor frequency withstand voltage test. This is used to investigate the insulation performance between windings on different sides and between windings and ground. In other words, in order to investigate the main insulation level of dry-type transformers, it is only applicable to fully-insulated dry-type transformers. Therefore, the test winding will be grounded on the other side of the dry-type transformer. When performing an external withstand voltage test, switch the switch when the power supply voltage is low; when the test power supply voltage reaches below 40% of the test voltage, the boost speed is arbitrary; when the test power supply voltage is more than 40%, it rises at a rate of 3% per second; After reaching the specified voltage and duration, the test voltage should be quickly and evenly reduced to less than 25% of the test voltage within 5S, and the power supply can be cut off.