Test factors affecting the power frequency withstand voltage test

HV HIPOT specializes in manufacturing power frequency withstand voltage test equipment (also known as series resonance). Now, let’s introduce the test factors that affect power frequency withstand voltage tests.
Some of the main factors affecting the power frequency withstand voltage test are as follows:
1. We need to select the appropriate capacity of the testing equipment. If the capacity of the testing equipment is insufficient or too large, it will have an impact on the on-site testing.
2. The influence of altitude on the test requirements: As the altitude increases, the spatial density decreases, the average free path of electrons in the electric field increases, and electrons can accumulate greater kinetic energy between two collisions (compared to normal density), making them more likely to ionize, thereby causing the discharge voltage of the air medium to decrease.
3. Preventing the generation of overvoltage during the test: During the power frequency withstand voltage test, if the voltage is not gradually increased from zero but instead is applied through the secondary winding of the test transformer with an external voltage, then overvoltage will occur on the test sample due to the excitation surge current; if the power supply is suddenly cut off during the test, for small-capacity test samples, overvoltage may be caused by self-induced electromotive force. Both of these situations may lead to false breakdown of the test sample. Therefore, during the power frequency withstand voltage test, the test operation procedures should be strictly followed.
4. Influence of capacitance rise effect on test values: During the AC power frequency withstand voltage test, the tested item is usually a capacitive load. The high-voltage winding of the test transformer is connected to the capacitance of the tested item. Thus, the capacitive current flowing through the capacitive load generates a voltage drop in the impedance of the test transformer winding. The secondary voltage of the test transformer increases, which is significantly greater than the secondary voltage calculated based on the transformation ratio. This phenomenon is called “capacitance rise effect”. Therefore, the original transformation ratio is no longer applicable. The increase ratio is proportional to the short-circuit impedance of the transformer. Generally, the increase range is approximately 4% to 30%. To avoid misjudgment caused by measurement errors, for tested items with larger test capacitors, the voltage on the high-voltage side should be directly measured.
5. Impact of waveform distortion on test results: Due to the fact that power-consuming units have introduced a large number of nonlinear loads, which has increased the harmonic circuit components and made the distortion of the grid voltage waveform increasingly severe. To ensure the accuracy of the test results, it is necessary to measure their peak values in order to eliminate the measurement errors caused by the distortion of the voltage waveform.