Characteristic Analysis And Parameter Selection Of ZnO Arrester Used In HVDC-VCB System

As one of the key equipments to guarantee the safe and stable operation of the HVDC transmission system,the HVDC-CB affect the development of HVDC transmission systems to high voltage and multi-terminal transmission networks to a certain extent.When the DC circuit breaker forced current zero crossing,the residual energy stored in the system will cause the overvoltage across the main circuit breaker.In severe cases,it will cause the arc to restrike and cause the breaking failure.Absorbing this part of the residual energy has become one of the important issues to be solved for the development of HVDC circuit breakers.This paper,“Characteristic Analysis and Parameter Selection of ZnO Arrester used in HVDC-VCB System”,is related to the “Research on the theory of HVDC short-circuit breaking based on intelligent modules technology” of the National Natural Science Foundation of China.First of all,the working background of zinc oxide arresters is introduced.The theoretical analysis and calculation of the breaking principle and breaking process of the HVDC vacuum circuit breaker have been carried out,and the formulas for calculating the overvoltage and residual energy of the breaking system have been obtained.According to theoretical analysis,it can be seen that the overvoltage across the main circuit breaker increases with the increase of the inductance of the smoothing reactor and the breaking current,and the Surge arresters and other measures must be applied to absorb the remaining energy and suppress the overvoltage.This paper takes the 60kV/16 kA DC breaking system as the research object,and gives the parameter selection basis of the zinc oxide surge arrester.This paper designs and builds an impulse current generator.The electrical characteristics of ZnO Arrester are experimentally analyzed,and the experimental results of the dynamic and static volt-ampere curve and the impact of the impulse current waveform on the residual voltage are obtained.Finally,it is proposed that the parameters of the ZnO arrester need to be satisfied when the charging rate is 80% and the insulation coordination coefficient is 1.15.The residual voltage level should be limited to 70-87 kV,and a multi-or multi-column parallel structure is proposed.Based on the results of this study,the voltage-limit value and energy values derived from the analysis can be used along with other electrical and mechanical parameters to provide design parameters for MOA used in HVDC-VCB.Based on PSCAD software,the paper establishes the simulation model of the breaking of the HVDC vacuum circuit breaker.Comparing the simulation results of the system model and the experimental model,it is concluded that the overvoltage of the system model is not equivalent to the experimental model's.In addition,the influence of different arrester parameters on the performance of the breaking system is also analyzed.From the simulation results,it can be concluded that the lower the residual voltage of the arrester is,the better the protection performance is,and the more energy is absorbed;however,the higher the residual voltage level is,the more beneficial it is to reduce the removal time of the short-circuit current.The effectiveness of the theoretical analysis was verified by simulation analysis.At the same time,the validity of the theoretical analysis and the rationality of the zinc oxide surge arrester parameter selection are verified.Finally,some issues related to zinc oxide surge arresters for HVDC vacuum circuit breakers still need to be solved.Finally,the related issues that need to be further solved for the zinc oxide surge arrester used in HVDC-VCB system are put forward.