BIL software is used for calculation of voltage distribution inside windings insulation during impact of the basic impulse level tests and comparing with acceptable voltage in order to optimize winding insulation.
Power transformers are important and expensive elements of power systems. Consequently one of the fundamental problems of their design is a protection from emergency operations one of which is lightning overvoltage. In order to prevent damage of transformer insulation from the lightning overvoltage, basic impulse level tests including full and chopped lightning impulses were approved. One of the criteria for passing the tests is a correct choice of insulation in designed transformer that can be obtained by comparing calculated (measured) voltage distribution inside the insulation and permissible voltage during impact of the lightning impulses. The voltage distribution is highly depends on windings structure of the transformer and often it should be improved in order to optimize insulation for basic impulse level tests passing.