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Note on power frequency withstand voltage test

time:2020/12/9   source:华天电力  reading:339 time

The oil-immersed test transformer is suitable for the power system to test the insulation strength of various high-voltage electrical equipment and insulating materials under power frequency or DC high voltage. The capacity of the oil-immersed test transformer is 3kVA~300kVA, and the capacity can be customized according to the test requirements.


Operation precautions when the oil-immersed test transformer is suitable for power frequency withstand voltage test


1. The test personnel should do a good job in the division of labor, clarify the methods of mutual contact, and have a dedicated person to supervise the site safety and observe the status of the test product.


2. The oil-immersed test transformer should be cleaned first and kept dry to avoid damage to the tested product and errors caused by the test.


Hipot Test Set.png


3. For large-scale tests, the air-lift test should generally be carried out first, that is, when the oil-immersed test transformer is not connected, the voltage is boosted to the test voltage, various meters are calibrated, and the ball gap is adjusted.


4. The oil-immersed test transformer must not increase the voltage too fast, and it must be prevented from being suddenly pressurized and the non-regulator is not at the zero position. The power supply cannot be cut off suddenly, and the switch should generally be opened when the voltage regulator drops to zero.


5. When the voltage rises to the test voltage, start timing. After 1 minute, the power can be turned on when the voltage drops below the test voltage quickly.


6. In the process of boost or withstand voltage test, if the following abnormal conditions are found, the voltage should be reduced immediately, the power supply should be cut off, the test should be stopped and the reason should be found out: 1) The voltmeter pointer swings greatly. 2) The insulation is found to be burnt or smoke. 3) There are abnormal sounds in the test product.


7. The insulation resistance of the oil-immersed test transformer should be measured before and after the withstand voltage test to check the insulation.


In the power frequency withstand voltage test of the oil-immersed test transformer, the measured voltage (instrument voltage) on the low-voltage side is not very accurate. The reason is that the test transformer has a leakage pit, and there must be a voltage drop or a voltage drop on the leakage reactance. The capacity rises, so that the voltage on the test product is lower or higher than the voltage reflected on the low-voltage side measuring voltmeter. During the power frequency withstand voltage test, the voltage on the test product is higher than the output voltage of the test transformer, which is the so-called capacity During the induction withstand voltage test, there must be a voltage drop in the leakage reactance of the test transformer.


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