Relevant Theory And Experimental Investigation On Hybrid Circuit Breaker

Our country currently need circuit breakers whose breaking capacity, dynamic stability and thermal stability reach63kA in the EHV power system. With the grid development of1000kV voltage level, it needs larger capacity circuit breakers. The rate of decline of interruption current and rise rate of recovery voltage after current zero restricted the breaking capacity of SF6circuit breaker. In order to ensure good high-current interruption capacity, it needs sufficient pressure of SF6and takes higher process cost. Meanwhile, SF6gas has a strong greenhouse effect and its exhaust leak is harmful. Vacuum circuit breakers are widely used in the distribution field because vacuum has excellent ability to withstand rate of decline of interruption current and rate of rise of recovery voltage. It shows more superior breaking capacity than SF6circuit breaker in the power system above50kA fault current. We can combine the strong insulation characteristics of SF6circuit breakers and good interruption characteristics of vacuum circuit breaker to develop the economic and practical ultra-high voltage large-capacity circuit breaker. Hybrid circuit breaker (HCB) based on vacuum interrupter and SF6interrupter in series can overcome their shortcomings in the maximum extent. In addition, we can reduce the pressure of SF6circuit breaker and compensate its breaking capacity loss by series vacuum circuit breaker to solve the problems of SF6gas liquefaction temperature increase in high altitude and the need of breaking capacity.This paper reviews the research status of HCB, technical difficulties and problems need to be studied; illustrates its practical significance to study and mainly research works; theoretically analyzes the static insulating properties and dynamic insulation recovery characteristics of vacuum and SF6gas; clarifies the feasibility of further research; calculates the properties of static electric field distribution of the vacuum interrupter and SF6interrupter by using Ansoft software; sets up sevel HCB models under different connection models; analyzes its structure in a three-dimensional electric field numerical simulation; contrasts the more reasonable model structures of HCB models; provides a theoretical basis for the structural design of the prototype; builds the electromagnetic transient simulation platform by ATP software and sets the parameters of the system simulation; developes a HCB arc model based on vacuum circuit breaker and SF6circuit breaker in series; studies the characteristics of vacuum arc and SF6arc and their interactions in the interruption process; proves up voltage distribution relationship between current interruption and dielectric recovery process under different collaborative action strategies; contrasts the breaking capacity properties between SF6circuit breaker and HCB, and proposes the control accuracy requirements of actuator of HCB prototype.Combined with the above analysis of prototype structure design and actuator control accuracy requirements, the design concept of fiber-controlled HCB module based on vacuum circuit breakers and SF6circuit breakers in series is given; the experimental prototype is designed in a form of vacuum circuit breaker placing on the top of SF6circuit breaker. The interrupter and actuator of vacuum circuit breaker are equipotential connection; a coordination actuator control system and a constant speed adaptive control system of permanent magnetic actuator are completed; fiber optic control technology is used to achieve the action coordinated control between two circuit breakers; an actuator self-energy power supply of the vacuum circuit breaker is design; the entire control system is conducted EMC test.The breakdown mechanism of HCB series gap is studied under static conditions; the external voltage waveform, electrode polarity, electrodes distance and SF6inflation pressure are changed in experiment to get change law of static dielectric strength; the actuator mechanical properties and the performance and electrical life of self-energy power supply are tested in HCB prototypes (24kV and40.5kV); the interaction between vacuum circuit breaker and SF6circuit breaker during short-circuit current interruption is studied, and its optimal coordinated action interval is obtained; finally, a breaking capacity gain characteristics between HCB and SF6circuit breaker is obtained by a plenty of experiments.The experimental results verify the calculation results of electric field distribution by Ansoft software; proves the high controllability and reliability of the experimental prototype, that meet the experimental research needs of HCB; the interaction between vacuum dynamic arc and SF6dynamic arc is correspond well in both of simulation and experimentation. It establishes the theoretical and experimental foundation for further study of HCB technology. Meanwhile, research work has a strong reference value for the research of low-carbon high-voltage large-capacity circuit breaker which is constituted by vacuum circuit breaker and gas circuit breaker (non greenhouse gas).