In the field of transformer manufacturing, lightning impulse voltage test is the "ultimate test" for testing the insulation performance of products. However, many transformer manufacturers often only focus on the lightning full wave test capability when purchasing impulse voltage generators, while neglecting the importance of the cutoff function. In fact, for the special product of transformers, the lack of a surge voltage generator for waveform testing is like an eagle without a wing - no matter how high it flies, it cannot complete a complete flight.
Why do transformers need to undergo a cutoff test?
According to national standards, transformers must pass lightning full wave and cutoff impulse tests to comprehensively assess the strength of their main insulation and longitudinal insulation. The full wave test mainly assesses the main insulation (winding to ground and between windings), while the cut wave test is an extremely rigorous test of the longitudinal insulation (between turns and between cakes).
The truncated waveform simulated is the waveform formed by lightning overvoltage flashover in the external gap of the equipment. When lightning waves invade a transformer, if flashover occurs externally and the waveform is suddenly cut off, this cutting process will generate a huge oscillation voltage inside the winding, causing the most severe impact on the inter turn insulation. Therefore, the fixed sequence for transformer standard testing is to first test the full wave and then test the cut-off wave. If a transformer only undergoes full wave testing without waveform cutting, its insulation assessment is incomplete.
The accuracy of wave interception determines the success or failure of the experiment
The technical difficulty of the truncated wave test is much higher than that of the full wave test. The precise control of truncation time and the stability of truncation time are directly related to the effectiveness of experimental results. If the dispersion of the cutoff wave is too large and the waveforms of different tests are inconsistent, it will be impossible to make accurate judgments on the longitudinal insulation strength of the transformer.
The Wuhan UHV series lightning impulse voltage generator adopts a truncation device to generate lightning waves with a truncation time of 2-6 μ s, and the dispersion of the waves is less than 100ns. This level of accuracy ensures the waveform consistency of multiple truncation tests, providing reliable guarantee for the accurate evaluation of transformer longitudinal insulation. The equipment supports lightning impulse voltage full wave and cutoff tests for transformers and mutual inductors that require cutoff tests.
In terms of configuration selection, users who require waveform truncation function should choose models with truncation devices, oscilloscopes, or acquisition cards. The technical team of Wuhan UHV can provide a complete configuration plan for the cutoff test system based on the specific product type and testing standards of the transformer manufacturer.
From standard to practice: wave cutting capability is a "must-have" for transformer manufacturers
For transformer manufacturers, whether their products can pass the cut wave impact test is directly related to whether they can obtain type test reports and enter the market. Especially for export-oriented transformer manufacturers, international standards also have clear requirements for the cut-off test. A set of impulse voltage generators without stable cutoff output capability will directly limit the product certification ability and market expansion space of transformer manufacturers.
Wuhan UHV is deeply involved in the field of high-voltage electrical measurement, and its UHV series lightning impulse voltage generator has been widely used in various types of impulse voltage tests for standard lightning impulse, lightning cutoff wave, operational impulse, and non-standard impulse waves required by users for power transformers, reactors, transformers, and other high-voltage electrical appliances. The company's products have won industry reputation for their high-quality performance and reliable quality.
For transformer manufacturers, when purchasing lightning impulse voltage generators, they not only need to consider the full wave testing capability, but also pay attention to the presence and accuracy of the cutoff function. The cut-off test is an indispensable "touchstone" for transformer impact testing; A shock generator with high-precision cutoff output capability is a key equipment for transformer manufacturers to ensure product quality and pass standard certification.