Investigation on dynamic characteristics of water-tree discharge in underground cable

In underground cable water tree is the main defect, of which discharge plays an important role in the aging process of insulating materials. To investigate the microscopic mechanism of water-tree discharge in underground cable, a numerical plasma-chemical model is developed. The dynamic characteristics of water-tree discharge are analyzed, including voltage waveform, current waveform, the electron density, electron temperature, ion density, electric field and electron capacitance power deposition. Our results reveal that these waveforms of current and voltage show periodic behaviors. As the increase of the formation of pulse current, the spatiotemporal distributions of electron density and ion density significantly increase, which change the electric field polarity in water tree. Meanwhile the distorted electric field becomes the energy source of electron avalanche and electron temperature. In addition, it was found that capacitive power dissipation gathered on dielectric surface, which aggravates the aging process of the insulation material.