Lightning impulse voltage (LIWL) tests and switching impulse voltage tests are carried out to assess the dielectric stress resulting from transient over - voltages induced by lightning strikes and switching operations respectively. An impulse voltage generator produces a steep - front voltage waveform, which is then applied to the test object. A measurement system, consisting of a voltage divider and a digital recorder, is used to measure and analyze the test voltages and their waveforms.
The figures present examples of a lightning impulse withstand voltage test conducted on a 420 kV live - tank circuit breaker. This test aims to evaluate the critical withstand voltage of the equipment under excessive voltage conditions that exceed the standard values.
This test is a mandatory requirement for every circuit breaker produced in the factory.
In addition to the various specified voltage withstand tests for evaluating the dielectric performance of equipment, after conducting other tests, it is necessary to perform conditioning checks as part of the type tests for switching equipment like circuit breakers. These procedures are carried out in accordance with standards such as IEC 62271 - 1 and IEC 62271 - 100.
