Study On Lightning Breakage Of 10kV Overhead Insulated Line And Optimization Of Lightning Protection Measures

Distribution network lines have the characteristics of wide distribution and low insulation level.In the 1990s,China began to replace bare conductors in distribution lines with insulated conductors.Although this measure has improved the level of line insulation,it has also led to frequent occurrence of lightning strikes and disconnection accidents.Therefore,analyzing the mechanism of lightning strike and disconnection and proposing new lightning protection measures are the key research directions in the field of lightning protection of distribution networks at this stage.In this paper,an ablation model of insulated conductors is established through the COMSOL simulation platform,and the ablation conditions of the conductors when subjected to lightning current and power frequency short-circuit current are simulated.Then the wire force model is established to analyze the force when the wire is ablated.According to the simulation results,the lightning current only leaves a perforation in the insulation layer of the wire,and the burning of the power frequency arc can ablate and fuse the insulated wire.The mechanical simulation results of the insulated wire show that the tension of the wire at the ablation place changes abruptly,and is affected by the short-circuit electromotive force between the wires and the electromagnetic thrust of the arc.In addition to arc ablation damage,ductile fracture and brittle fracture also occur at the fracture.The simulation research provides a reference for the lightning protection of 10kV overhead insulated conductors.This paper proposes an improved guard gap structure.In this structure,an arc-pulling coil is installed next to the protection gap,and by changing the magnetic field distribution of the gap,the electromagnetic force on the arc is increased,and the arc is thinned,thereby accelerating the extinguishing of the arc.Through the COMSOL simulation platform,a simulation model of gap arc discharge is established based on the magnetohydrodynamics(MHD)model.The simulation calculation shows that the arc of the improved protective gap is pulled away by a far greater distance than the traditional protective gap,and the minimum arc radius is 47%of the traditional protective gap.Field experiments show that the arc of the improved protection gap can be extinguished within 5 ms,which shows that it is effective and feasible in lightning protection.