Investigating the impacts of temperature on the dielectric response of oil-paper insulation system

In recent decades, Dielectric Response Technique is widely used by power utilities for assessment of the condition of electrical equipments as a non-destructive dielectric testing tool, especially for oil-paper insulation systems. For on-site measurements, comparing the results at different temperature is usually difficult as the temperature uncertainty of devices, so understanding its effects on dielectric response is of great significance for the condition assessments of oil-paper insulation. In this paper, accelerated thermal aging experiments of oil-impregnated pressboard are performed to obtain aged samples. Return Voltage (RV) and Frequency domain spectroscopy (FDS) measurements are carried out on some new and aged oil-impregnated pressboards with temperature varying from 12°C to 60°C. The relationship between dielectric response and temperature is investigated both in time and frequency domain, and it is verified that temperature dependency to the response of oil-paper insulation follows an Arrhenius law. Results show that the dominant time constant of RV spectrum decreases exponentially with temperature increasing. It can be concluded that the curve of dissipation factor shifts towards higher frequencies with the same shape while temperature changes, and the whole insulation exhibits higher dissipation factor and permittivity with the aging of cellulose.