Study on formation of dry band on wet polluted surface attached with float potential metal based on distributed parameter optimization simulation

Under the condition of contamination and damp, the metal bolts on the composite tower become float potential conductor. Serious partial arc discharge appears near the metal bolt, which threatens the safe operation of the transmission line. The artificial pollution test is carried out on the small size specimen to reproduce the discharge phenomenon and obtain the characteristic parameters. Based on the parameter optimization method with infrared temperature data as constraints, the distributed parameter finite element model of the specimen is calculated to obtain the electric field and current density distribution. The results reveal that when the dry band is newly formed, the current density and temperature at both ends of the dry band are very high, which make the dry band propagate to both sides and pass through the pollution layer. When the dry band just passes through the pollution layer, the leakage current is blocked and the electric field on dry band is intensified, leading to dry band discharge. It can be inferred from the electric field of the pollution layer that the arc cannot develop forward, but it will appear intermittently on the dry band.