Research On Limited Asynchronous Breaking Of Vacuum Circuit Breaker With Multi-breaks

As an important equipment to ensure the safe and stable operation of the power system,the vacuum circuit breaker(VCB)is widely used in the medium and low voltage fields due to its strong arc-extinguishing ability,small size,long service life,maintenance-free,pollution-free,etc.,but due to the saturation effect of breakdown voltage of VCB and vacuum gaps limits the development of high voltage.At present,the high voltage field is still dominated by SF6 circuit breakers,but SF6 is a strong greenhouse gas.The application of SF6 circuit breakers will be more and more limited.VCB has become one of the main alternative directions of SF6 due to the above advantages.It is of great strategic significance and technical background to study the serial technology of VCB with multi-breaks and push it to a higher voltage level.Synchronous operation is an important research direction for VCB with multi-breaks.Therefore,this paper will take asynchronous operation of VCB with multi-breaks as the background,the dynamic dielectric strength recovery characteristics of each VCB under different asynchronous breaking conditions are studied,aimed to enrich the theory of dynamic dielectric strength recovery of VCB with multi-breaks and solved the technical obstacle of synchronous control.In this paper,based on the equivalent model and static voltage distribution of each series breaker of VCB with triple-breaks,the dielectric strength recovery process of VCB and the transient recovery voltage(TRV)distribution of VCB with multi-breaks are analyzed,and the influencing factors of TRV are discussed fron capacitance,post-arc characteristics and operational synchronization.A new idea of limited asynchronous breaking of VCB with multi-breaks is proposed and pointed out that when the VCB with multi-breaks is breaking from high voltage side to low voltage side,the TRV distribution of each series VCB is more uni form.Then the working principle,characteristics and control of the pennanent magnetic actuator of the VCB are analyzed.The radial basic function(RBF)neural network technology is introduced into the algorithm of open-close operation time of permanent magnetic actuator,and the function of time error of the permanent magnetic actuator is obtained,so as to realize more accurate time prediction.The experimental results show that the maximum error of the operation time of VCB based on RBF neural network is 0.3ms.Based on this,VCB with triple-breaks is controlled synchronously,and the maximum opening time difference of the three series VCB can be controlled within 0.6ms,which satisfies the national standard on the synchronous control precision of VCB with multi-breaks.High-precision synchronous control is the basis of limited asynchronous breaking of VCB with multi-breaks and provides technical support for active asynchronous compensation of dielectric recovery.In order to improve the tolerance of the overall transient recovery voltage of the circuit breaker,the concept of limited asynchronous breaking of VCB with multi-breaks is implemented,and a two-dimensional static model of the pennanent magnet mechanism of VCB unit is established in Ansoft.It is proved that limited asynchronous breaking can be realized by changing the excitation current of the external circuit.Using the Electromagnetic Transient Program/Alternative Transients Program establishes a continuous transition model for sheath growth,and realizes the simulation of limited asynchronous breaking by changing the operating time of each series VCB.These are two strategies for implementing limited asynchronous breaking.Combined with the insulation breakdown voltage gain and static breakdown statistical distribution model of limited asynchronous breaking,the feasibility of limited asynchronous breaking of VCB with multi-breaks is analyzed.Then the concept of dynamic dielectric recovery compensation for VCB with multi-breaks by limited asynchronous breaking is perfected,and a new path is given to improve tihe dynamic insulation level of VCB with multi-breaks.The application background of this study is the national science and technology support program.Based on the 40.5kV fiber-controlled vacuum interripter module(FCVIM),a 126kV VCB with triple-break is formed by U-shaped series connection,and 126kV voltage grade type test on the prototype of VCB with triple-breaks is carried out,including insulation test,temperature rise test and breaking test.On this basis,with the two methods of adjusting the moving speed and operating time of the moving contact,the 126kV VCB with triple-breaks prototype is tested by limited asynchronous breaking.According to the breaking test,the compensation for dynamic dielectric strength recovery of the VCB with triple-breaks is realized by active asynchronous breaking.It is effective only in the short arc interval,and has little influence on the breaking of long arc interval,and the maximum asynchronous time difference of the three series VCB should not exceed 4ms.In this paper,the theoretical analysis and test of dynamic dielectric strength recovery of VCB with multi-breaks are carried out,and the concept of limited asynchronous breaking is proposed.Based on this,the concept of active compensation for dynamic dielectric strength recovery of VCB with multi-breaks is proposed by limited asynchronous breaking,and the feasibility of this method is verified by a prototype of VCB with triple-breaks,which provides theoretical and technical support for the development of VCB with multi-breaks to higher voltage levels.