Influence of moisture on dielectric strength in polyamide (aramid) paper

This paper presents the influence of absorbed moisture and variation in environmental temperature on DC breakdown strength in 125 μm polyamide (aramid) paper. Polyamide (aramid) paper also known as Nomex® type 410 is widely used in a majority of electrical equipment applications. The combination of electrodes used for the investigation of breakdown strength was of diameter 12.5mm and 50mm. Specimens A-D, used for the investigation were prepared under four different environmental conditions. It is concluded that the electrical behavior of these material varies both with the environmental temperature and with the absorbed moisture. Variations in the breakdown strength were observed between 5.5-15.5% for specimens A-C, where as tremendous drop in the electrical breakdown strength was recorded for specimen D. The breakdown results were presented by using two-parameter Weibull statistical distribution. The statistical analysis was performed on large population of data, which leads to an effective design of electrical insulation.