Tracking failure of polyethylene/BN composite with pulse voltage under low temperature

Polyethylene (PE) is widely used as insulating materials in superconducting motors because of its excellent insulation properties. Tracking failure is a typical thermal breakdown which is caused by thermal accumulation on polymer surface. In this paper, the tracking failure behaviors of PE/BN (boron nitride) composites under low temperature were studied to clarify the effects of low temperature and BN particles on tracking performance. Tracking failure process under different pulse frequency was measured with a digital camera and an infrared thermal imager. The CCD camera was used to observe the failure process while the infrared imager was used to measure the thermal accumulation and decay process. Obtained results showed that the low temperature and the addition of BN fillers had a significant inhibitory effect on tracking failure process. In liquid nitrogen environment, the time to tracking failure increased obviously. It is concluded that the ability to inhibit tracking is improved by reducing the temperature at the concentrated discharge region and increasing the heat dissipation region.