Nondestructive Testing in Diagnostics of High-voltage Varistors

− High voltage varistors that consist of grained ZnO have to be tested before assembling. The recommended method for standard industrial testing of varistors demands application of high voltages and intensive currents that is inconvenient and needs extensive power consumption. Nondestructive methods for varistor quality and endurance evaluation have been proposed. They rely on the application of resonant ultrasound spectroscopy and nonlinearity testing. The parameters of assessment have been proposed and the results of measurements performed for several hundreds of varistor samples are quoted.