| Lightning damage has always been one of the main factors that threaten the safe and stable operation of the power grid.During line operation,due to the existence of thunder and lightning weather,the power system is affected by lightning waves,causing insulators to flashover,lightning strikes and other accidents.According to statistics,lightning strikes account for more than 60% of trip accidents that occur on high-voltage overhead transmission lines,which is an important factor causing line trips.In addition,multiple lightning strikes will cause the circuit breaker to break down again during the opening process,reignite the arc between the fractures,cause the switch to break down in the reclosing process,and fail to reclose the circuit,which will affect the safety and stability of the power grid and the power system run.In the context of the rapid development of power systems,studying the switching arc characteristics of circuit breakers is of great significance to ensure that the arc of the circuit breaker is successfully extinguished and safe and stable operation.In response to the frequent,destructive,and multiplicity of lightning accidents in China Southern Power Grid.This article has carried out the research of arc characteristics under the condition of multiple lightning strikes.Combining with the structural characteristics of 110 k V switchgear,a magnetohydrodynamic(MHD)model of the arc is established,the arc development process during the opening and closing process of the switch contacts,and the plasma temperature distribution characteristics are studied,and 110 k V disconnection under multiple lightning conditions is proposed.The optimal design plan of the circuit breaker is proposed,and the specific work is as follows:The arc distribution characteristics of the circuit breaker arc under the condition of double lightning strikes are analyzed,and the dielectric breakdown and recovery characteristic model of the 110 k V circuit breaker under multiple lightning conditions is established.Use the finite element simulation software COMSOL to establish a 110 k V circuit breaker contact model,input the physical parameter model of the arc,set the corresponding boundary conditions and mesh division,and combine the characteristics of multi-physics coupling.The influence of the contact distance of the circuit breaker,the contact ablation condition,and the contact breaking speed on the electric field distribution are calculated;the temperature characteristics and the air flow field distribution characteristics of the arc between the contacts of the circuit breaker are compared under different pressures.Arc characteristics of arc chamber.The 110 k V circuit breaker structure optimization method considering multiple lightning is obtained.Designed and invented a circuit breaker adjustable gap,studied the arc voltage distribution characteristics of the circuit breaker under lightning conditions,and established a 110 k V circuit breaker dielectric recovery and breakdown model under lightning conditions.A simulation platform was established through the lightning overvoltage generator,the adjustable gap of the circuit breaker and the test system to measure the voltage changes between the contacts of the circuit breaker under lightning voltage conditions,and the relationship between the contact breakdown voltage and the contact spacing was obtained curve.Finally,the characteristics of the influence of contact ablation on the arc temperature of the circuit breaker under the condition of double lightning strikes and the change of the arc temperature of the circuit breaker under different lightning current intervals are studied.In order to improve the ability of the circuit breaker to break the arc and successfully extinguish it without re-ignition,an optimization scheme for increasing the breaking speed is proposed. |
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