Abstract:DCcircuitbreaker(DCCB)isanindispensablekeyequipmentforbuildingvoltagesourceconverterbasedhighvoltageDC(VSC-HVDC)grid.Ahigh-speedmechanicalswitch(HMS)isthecorecomponentofDCCBtocarrycurrent,realizefastopeningandclosing,andwithstandopeningrecoveryvoltage.HMShasacomplexstructure,highspeed,severeelectricalstress,andhigh-reliabilityrequirements,soitsdesignanddevelopmentaredifficultandanyprobleminanylinkofHMSwillaffectthesafeandreliableoperationoftheDCCBandeventheVSC-HVDCgrid.However,atpresent,duetotheproblemsofunreasonabledesignandselection,laxprocesscontrol,andimperfecttestandassessment,HMShasfrequentfaultsinpracticalengineeringapplicationsofDCCB.ThecharacteristicsandcausesoftypicalfaultsofHMSinthedevelopment,commissioning,andoperationof500kVDCCBsthathavebeenusedintheZhangbeiVSC-HVDCgridprojectareanalyzed.Onthisbasis,focusingonthetypicalfaultsofHMSs,correspondingreliabilityimprovementmethodsfromtheaspectsofdesignandselection,productionandmanufacturing,testassessment,etc.areproposed,whichprovidesguidanceandbasisforthedesign,development,operation,andmaintenanceofHMSsof500kVDCCBs.Keywords:DCcircuitbreaker;high-speedmechanicalswitch;typicalfaultcharacteristic;reliabilityimprovementmethod摘要：直流断路器是构建柔性直流电网不可或缺的关键设备。快速机械开关是直流断路器中承载电流、实现快速分合闸、耐受分闸恢复电压的核心组件，其结构复杂、动作速度快、电气应力严酷、可靠性要求高，因而设计研制难度大，任一环节出现问题均会影响直流断路器乃至柔直电网的安全可靠运行。然而，目前快速机械开关由于存在设计选型不合理、工艺管控不严格、试验考核不完善等问题，导致在实际工程应用中故障率较高。针对已应用于张北柔性直流电网试验示范工程的500kV直流断路器，分析了直流断路器研制、调试、运行过程中快速机械开关典型故障的特性及原因。在此基础上，围绕快速机械开关典型故障从设计选型、生产制造、试验考核等方面入手，有针对性地提出可靠性提升措施，为500kV直流断路器快速机械开关设计研制和运维检修提供了指导和依据。关键词：直流断路器；快速机械开关；典型故障特性；可靠性提升措施0引言柔性直流电网不仅继承了柔性直流输电技...
