Effects of nano-SiO2 doping on tracking growth and thermal accumulation in silicone rubber insulation

Dry band arcing initiates the growth of conductive carbonized tracking on the weathershed of outdoor high voltage insulators. This is one of the key failure modes which can adversely affect the reliability of power transmission networks. Thermal accumulation in the discharge area is a primary factor for temperature build-up and tracking growth. This work investigates how nano-size SiÜ2 doping transforms the thermal accumulation and tracking growth on the surface of silicone rubber. Five samples of each type were tested by following the inclined plane test (IPT) procedure as described in IEC 60587. The step-wise tracking voltage (method 2) was adopted for the IPT with initial voltage of 3 kV, ramping rate of 250 V/h and duration of 4 h. From experimental results, excellent resistance to tracking growth is found in nano-SiÜ2 doped samples. Temperature distribution measurements show that heat is mainly accumulated in the middle discharge area. Also, nano-SiÜ2 with increasing filler content restricts the thermal accumulation effectively and this may impart better resistance to tracking growth.