Triple frequency induction withstand voltage generator The induced withstand voltage should be applied at 80% of the factory value, and the induced withstand voltage test is subject to the voltage standard and the rated withstand voltage of the neutral point terminal of the graded insulated transformer.
Note: For the highest voltage of the same equipment, two rated voltages are given for 220kV and above, considering the grid structure and voltage level, configuration and performance of overvoltage protection devices, equipment type and insulation characteristics, acceptable insulation failure rate, etc. Fully insulated transformers: For fully insulated transformers of 110kV and below, generally three-phase transformers, a three-phase symmetrical AC power supply is used, and 2 times the rated voltage at a frequency more than 2 times is applied to the low-voltage winding or other winding terminals of the test object, with other windings open. Graded insulated transformers: In China, for power transformers of 110kV and above, graded insulation is usually adopted, that is, the insulation level of the neutral point is lower than that of the line terminal.
Let's first talk about the test method of the triple frequency induction withstand voltage generator:
1. Test
Before conducting the frequency-multiplied induced withstand voltage test on the test object, a no-load test should be carried out on this device to check whether the device is intact.
(1) Wiring diagram of no-load test:
(2) Operation steps:
After confirming that the wiring is correct, input the three-phase voltage; turn on the power switch of the control box, and the green signal light will be on (if not, please return the voltage regulator handle to zero); then press the start button, the red working light will be on, and at this time you can start rotating the voltage regulator handle to boost the voltage, observe the voltmeter until the voltmeter reaches full scale. If there is no abnormal situation during this process, it indicates that the device is normal. Immediately return the voltage regulator handle to zero, disconnect the power supply, and the no-load test is completed.
2. Test
(1) Connect the triple frequency induction withstand voltage generator, control box, reactor (connected when needed) and the test object;
(2) Carefully check the connected lines, confirm that the wiring between the test object and this device is correct, and then input the three-phase voltage. The operation steps are basically the same as those of the no-load test; when the voltage rises to the required voltage value of the test object, stop boosting and maintain for 40 seconds; if no abnormal situation occurs, it indicates that the test object passes this test. At this time, immediately return the voltage regulator handle to zero and quickly disconnect the three-phase power supply. The test is completed.
