Application of Low Frequency Dielectric Spectroscopy to Estimate lifetime of Low-Voltage EPR Insulation

Abstract

This paper deals with the application of integral values of dielectric spectroscopy as the characteristic values from 10Hz to 1Hz for estimating the lifetime of low-voltage ethylene propylene rubber( EPR) insulation cables aging in the lab. The elongation-at-break and the dielectric dissipation factor (tanδ) were measured to study the characteristics of curve and to analyze sensitive measurement range. Based on the failure criterion of elongation-at-break, the correlation between the mechanical and dissipation curve was investigated and the effectiveness among three ways to assume values of dielectric dissipation factor was compared. Meanwhile, a time multiplicative shift factor was found with the same characteristics value at different aging temperatures and a prediction equation after selected reference temperature was obtained. Combined with integral equation of the deterioration tendency under reference temperature, a life model of dielectric dissipation factor integral for insulation material was derived. Results showed that testing parameters on integral value of tanδ had a contrary tendency with elongation-at-break and reflected the degradation trend in sensitive range within 10Hz~1Hz. Compared life model calculation results with measurements of cable in field, the measurement error was 3.33%. It had been found that this method could effectively evaluate the aging lifetime of low-voltage cable EPR insulation materials.