220kV power transformer is being tested

What is lightning impulse voltage test:

In order to test whether the impact strength of the main insulation and longitudinal insulation of the transformer conforms to the provisions of the national standard and to study and improve the insulation structure of the transformer, it is necessary to carry out the impact voltage test. The so-called lightning shock test is to apply a shock wave simulating the real lightning waveform on the terminal of the transformer winding. Transformers or other electrical equipment should be tested under the action of this shock wave to see if it can pass (or be damaged). The cut-off wave is equivalent to the waveform generated by the protection gap or air insulation flashover when the lightning wave enters the substation. It is a waveform in which the entire thunder wave is suddenly cut off and the voltage drops sharply to zero. The cut-off time can occur either in front of or after a wave. Shear wave test is also a test for transformer equipment. The test must have a shock-generating device. The device is called a pulse voltage generator. Some corresponding measuring instruments mainly include measuring spherical electrodes, dividers and high-voltage oscilloscopes for observing pulse waveform phenomena. The standard specifies that the full wave of the test waveform is 1.2±30%/50±20%μS (wave front/half peak time), and the zero crossing coefficient of the truncated wave (that is, the ratio of the first oscillation peak after truncation to the amplitude of the truncated wave) with the interception time of 2-6μS is in the range of 0.25 to 0.35. The impact test device is only suitable for large transformer plants and test research units. General units can entrust the transformer to test research units.

What is power frequency withstand voltage test:

Power frequency withstand voltage test device is the basic test equipment for power station, power supply and distribution system, scientific research institutions and other users. It is used to test the insulation strength of various electrical products, electrical components and insulating materials under the specified voltage, assess the insulation level of the product, find the insulation defect of the tested product and measure the ability of overvoltage.