Lightning Impulse Voltage Test
The lightning impulse voltage test is implemented to verify that the main and longitudinal insulation impact strength of transformers complies with national standard requirements, as well as to optimize and improve transformer insulation structures. This test applies standard lightning impulse waveforms to transformer winding terminals to simulate actual lightning strikes, checking whether transformers and other electrical equipment can withstand transient overvoltage damage under lightning shock conditions.
Two typical waveforms are adopted in the test: full lightning wave and chopped lightning wave. The chopped wave simulates the actual voltage waveform formed by flashover of protective gaps or air insulation in substations. It is generated by sudden truncation of a complete lightning wave, resulting in an instantaneous sharp drop of voltage to zero, with truncation positions occurring on either the wave front or wave tail.
The test system mainly consists of an impulse voltage generator and supporting measuring devices, including ball electrodes, voltage dividers and high-voltage oscilloscopes for waveform monitoring. According to standard specifications, the full lightning wave features a front time of 1.2±30% μs and a half-peak time of 50±20% μs. The truncation time of chopped waves is controlled within 2–6 μs, and its zero-crossing coefficient (the ratio of the first oscillating peak after truncation to the truncated wave amplitude) ranges from 0.25 to 0.35.
Professional lightning impulse test equipment is only equipped in large transformer manufacturers and professional research and testing institutions. Ordinary enterprises can entrust qualified third-party institutions to complete the test.
Power Frequency Withstand Voltage Test
The power frequency withstand voltage test is a fundamental insulation performance test for power equipment. Widely applicable to power stations, power supply and distribution systems and scientific research institutions, it is used to detect the insulation strength of various electrical products, components and insulating materials under rated power frequency voltage.
This test can effectively evaluate the overall insulation level of products, expose potential internal insulation defects, and verify the overvoltage resistance capability of electrical equipment, serving as a crucial routine test to ensure the safe and stable operation of power equipment.
