Effect of Magnetic Field on Partial Discharge Behavior of Composite Insulation for Cryogenic Applications

The influence of a magnetic field on partial discharge due to voids such as butt gaps in composite insulation systems is reported. Experimental characterizations of an emulated butt gap in polypropylene laminated paper (PPLP) layers at room temperature in pressurized nitrogen gas and at 77 K in liquid nitrogen are described. A reduction in the partial discharge inception voltage was observed both at room temperature and 77 K when a 170 mT magnetic field was applied to the butt gap region. The differences in the phase resolved partial discharge patterns among the different cases studied are discussed. It was concluded that the presence of a magnetic field influences the PD dynamics at cryogenic temperatures.