Variation of dissipative properties of 6 (10) kV cable insulation as a supplementary diagnostic criterion

This article focuses on possible application of a supplementary mechanical criterion for assessment of varying insulation properties of 6(10) kV cable line during operation. The research is conducted on the samples of impregnated paper insulation of cables having been exposed to thermal stress caused by recurring short circuit currents during experiments. In addition to the variation of mechanical stress at break of the insulation samples, the paper investigates the integral criterion for assessment of energy dissipation in insulation subjected to recurring mechanical stress. It was calculated for samples before and after a series of recurring short circuit faults. Energy dissipation variations obviously depend on temperature of the insulation sample, frequency of recurring mechanical stress and insulation conditions. The data obtained demonstrate the benefits of the application of such parameter as a supplementary mechanical criterion for assessment of insulation life.