Wuhan UHV specializes in producing power frequency withstand voltage test equipment (also known as series resonance). Next, we will share with you the factors that affect the power frequency withstand voltage test site and the test precautions.
The main factors that affect the power frequency withstand voltage test are as follows:
1. Firstly, we need to choose testing equipment with appropriate capacity. If the capacity of the testing equipment is insufficient or too large, it will affect on-site testing.
2. The impact of altitude on testing requirements: As altitude increases, spatial density decreases, the average free path of electrons in the electric field increases, and electrons can collect more kinetic energy between collisions (compared to normal density), making ionization more likely, resulting in a decrease in the discharge voltage of the air medium.
3. To prevent overvoltage during the testing process: If the voltage does not gradually increase from zero during the power frequency withstand voltage test, but appears on the test product due to the earth frame voltage on the primary winding of the test transformer, it is caused by the excitation of surge overvoltage. If the power is suddenly cut off during the testing period, for small capacity test samples, overvoltage may occur due to self inductance potential. Both of the above situations may lead to accidental puncture of the test item. Therefore, when conducting power frequency withstand voltage testing, the testing operation rules should be strictly followed.
4. The impact of increased capacity on test values: In AC power frequency withstand voltage testing, the tested product is usually a capacitive load, and the high-voltage winding of the tested transformer is connected to the tested capacitor. In this way, the capacitive current flowing through the capacitive load will cause a voltage drop in the winding impedance of the test transformer, and the voltage on the secondary side of the test transformer will decrease, which is significantly higher than the calculated secondary side voltage. Conversion rate. This phenomenon is called the "capacity increase effect", which shows that the original transformation ratio is not applicable. The process of increase is proportional to the short-circuit impedance of the transformer, and the general increase range is about 4% to 30%.
5. The impact of pressure waveform distortion on test results: Due to the presence of many nonlinear loads in the power unit, the number of harmonic circuit components has increased, and the problem of voltage waveform distortion in the power grid is becoming more and more serious. In order to protect the accuracy of the test results, it is necessary to measure their peak values to eliminate measurement errors caused by voltage splash distortion.
In actual power frequency withstand voltage tests, the following points should also be noted:
1. The test transformer and control box should be reliably grounded;
2.During the testing process, the boost speed should not be too fast, and it is absolutely not allowed to suddenly turn on or off the full voltage;
3. The test items should be cleaned and absolutely dry to avoid damage to the test items and errors caused by testing;
4. During the testing process, if the tested product experiences a short circuit or breakdown, the overcurrent relay in the control box will operate. At this point, before removing the test product, reset the voltage regulator to zero and cut off the power supply.
5. When conducting high-voltage AC/DC testing, two or more personnel must participate, and the division of labor should be clearly defined, and the methods for each other should be clearly defined. And there is a dedicated person to supervise on-site safety and observe the testing status of the tested products;
6. During the boost or withstand voltage test, if any of the following abnormal situations are found, the voltage should be immediately reduced and the power supply should be cut off to stop the test, and the test should be conducted under the circumstances that caused the problem.