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The essence of the mathematical model of disconnectors' multiple reignition arc is the repeated breakdowns of SF6. In this study, the kinetic properties of microparticles are studies based on the streamer discharge theory, and a fluid arc mathematical model applied in centimetre clearance is established. Ultra-High Voltage (UHV) disconnector manufactured by Pingao Electric Co. Ltd of Henan Province is selected as the object and the resistance change process of contact clearance multiple reignition arc is simulated by finite difference method-finite element method-flux corrected transport self-programming in MATLAB based on the chamber structure and operating characteristics. UHV gas-insulated switchgear very fast transient overvoltage (VFTO) test platform is built to gain the characteristics of VFTO waveforms generated by the disconnector's operation. Compared with simulation results, the test data shows that the fluid arc mathematical model can scientifically explain the dynamic development process of microparticles in the contact clearance and the calculation results are consistent with the test data. In addition, the arc fluid mathematical model combines the structure and operating characteristics of the switch with the development process of microparticles, which can better guide the design of the switch, and provide a theoretical basis for the suppression of VFTO with the disconnector itself.

In this article, we take a 126 kV single-break vacuum circuit breaker as the research object and study the application of high-energy-density PM motor in the high-voltage circuit breaker for the first time. The PM motor maintains maximum power density and torque density during the start-up phase. Note that most of the faults of high-voltage circuit breakers are mechanical faults. We designed a set of mechanical fault prediction systems for high-voltage circuit breakers. We present the prediction method of the opening and closing action curve of the high-voltage circuit breaker. It is inspired by Chaos Ant Colony Algorithm (CAS) and an optimized Long- and Short-Term Memory (LSTM) cycle neural network. We constructed the main structure of the neural network expert system and established the fault prediction model of the high-voltage circuit breaker, based on the LSTM cycle neural network, optimized by CAS. We used the improved least-square method to achieve the operation accuracy of the phase control switch. Finally, we completed the development and experiment of the prototype.

In order to study the cold dielectric recovery characteristics of high voltage SF 6 circuit breaker, a mathematical model is established for the airflow field and electric field inside the circuit breaker arc extinction chamber, and numerical calculation and analysis were made for electric field intensity and airflow characteristics. The variation curve of the electric field non-uniform coefficient $f$ with the contact open distance is obtained by electric field calculation; the electric field calculation result is introduced into the flow field, while the spatial distribution dynamic characteristics like pressure, mass density were analyzed through the flow field, and the critical breakdown field strength of contact gap is calculated according to the stream theory; Based on the electric field calculation result, the circuit breaker arcing chamber structure is a slightly uneven electrical field, the breakdown voltage of the SF 6 gas under different pressures is calculated by breakdown voltage empirical formula of SF 6 gas under slightly uneven electrical field. The results show that the dielectric recovery strength is affected by the open distance of the circuit breaker, the nonuniformity coefficient of the electric field structure and the particles number density of SF 6 gas. Near the open distance of 3mm, there is a sharp point in the electric field nonuniformity coefficient, the minimum particles number density of SF 6 gas between the arc contacts, and the low breakdown voltage of SF 6 gas, which is the relatively weak area of SF 6 dielectric insulation strength in breaking process. Under the same conditions, the higher the pressure of arc extinction chamber, the higher the recovery strength of the dielectric. The dielectric recovery strength at 0.5MPa is 71.4% to 0.7MPa. The analytical method of this paper provides a new idea for the study of dielectric recovery characteristics of SF 6 and its alternative gas.

The insulation strength of high-voltage switchgear opening and closing break is the basis to ensure its safe operation, and it is also one of the important factors affecting its successful closing and breaking. In order to study the break insulation characteristics of the mixed gas of perfluoroisobutyronitrile (C 4 F 7 N) and carbon dioxide (CO 2 ), Build a test and research platform for dynamic insulation characteristics of C 4 F 7 N/CO 2 mixed gas break of the prototype circuit breaker closing-opening process under no-load high DC voltage, Measure the base pressure of 0.7MPa arc extinguishing chamber, the dynamic breakdown voltage of pure SF 6 , 5%C 4 F 7 N/95%CO 2 , 9%C 4 F 7 N/91%CO 2 and 13%C 4 F 7 N/ 87%CO 2 mixed gas, study mixed gas break insulation strength changes. The results show that, compared with pure SF 6 , C 4 F 7 N/CO 2 mixed gas break dynamic breakdown voltage dispersion is greater, the expected penetration time is longer than SF 6 ; increase the content of C 4 F 7 N in the mixed gas, The rate of change of the dielectric strength of the mixed gas break is improved.

During the breaking process of the self-blasting circuit breaker, the pressure characteristics greatly affect the action characteristics of the valve and the pressure in the expansion chamber, thus affecting the arc blowing effect. Therefore, a 550kV single-break selfblasting circuit breaker is taken as the research object. Based on the theory of magnetohydrodynamics (MHD), a two-dimensional transient model considering arc radiation is established, and the numerical calculation of the breaking process under two typical breaking conditions with short- circuit current of 63kA and 40kA and arcing time of 12ms is completed. The pressure and temperature distribution in the expansion chamber, and the action characteristics of the valve are obtained. Besides, combined with the test conditions, the 63kA short-circuit current, the pressure and temperature characteristics under short, medium and long arcing conditions are studied, and the valve action time under different conditions is obtained. The results show that the maximum temperature of the arc core region is 33219K at 63kA, which is about 3332K higher than the 40kA condition. The maximum pressure in the expansion chamber is 2.94MPa under the condition of 63kA and 2.36MPa at 40kA. The check valve is mainly affected by the temperature and pressure in expansion chamber side under the two breaking conditions, and the force received on the side of the cylinder is substantially same. The action time of the check valve under 63kA is 0.06ms earlier than the 40kA, and relief valve advance acts 0.05ms. Corresponding to different arcing time, the action time of check valve is 16.38ms, 16.28ms and 16.48ms and the time of relief valve is 17.52ms, 17.42ms and 17.67ms.

Combining load characteristics of 126kV high voltage circuit breaker, a design scheme of high power density permanent magnet motor is proposed. A control strategy with different control parameters in different travel stages of motor operating mechanism of high voltage circuit breaker is proposed, in order to satisfy the requirement that the control system can effectively control the speed of motor operating mechanism in the whole movement process. The experimental results show that the requirements of the opening and closing time and speed of 126kV vacuum interrupter can be satisfied. The opening and closing time have good stability.

High voltage SF 6 circuit breaker must meet the breaking requirement for large short-circuit current, and ensure absence of breakdown after breaking small current. A 126kV high voltage SF 6 circuit breaker was used as the research object in this paper. Based on the calculation results of non-equilibrium arc plasma material parameters, the distribution of pressure, temperature and density were calculated during the breaking progress. The electric field distribution was calculated in the course of flow movement, considering the influence of space charge on dielectric voltage. The change rule of the dielectric recovery progress was given based on the stream theory. The dynamic breakdown test circuit was built to measure the values of breakdown voltage under different open distance. The simulation results and experimental data are analyzed and the results show that: 1) Dielectric recovery speed (175kV/ms) is significantly faster than the voltage recovery rate (37.7kV/ms) during the arc extinguishing process. 2) The shorter the small current arcing time, the smaller the breakdown margin, so it is necessary to keep the arcing time longer than 0.5ms to ensure a large breakdown margin. 3) The calculated results are in good agreement with the experimental results. Since the breakdown voltage is less than the TRV in some test points, restrike may occur within 0.5ms after breaking, so arc extinguishment should be avoid in this time range.

In the research of lightning protection in UHV substation, overvoltage will cause serious damage to the substation when the transmission line enters the lightning strikes. In this paper, combined with substation electrical main wiring, the UHV lightning transient characteristics of the module are considered. Then in the ATP-EMTP simulation environment, the GIS transient model of the key equipments such as pole tower, high voltage reactor and transformer are established under the lightning impulse. When the counterattack or the shielding failure strikes, the lightning intrusion wave overvoltage of a UHV substation GIS in different operating modes is calculated by comparing and analyzing the different types of arrester configuration. The results show that the outlet section and the high resistance share a set of arrester, and the main transformer installs a set of arrester to meet the equipment insulation margin requirement. The research results can provide reference for the arrester configuration of the station, and provide the theoretical basis for the lightning overvoltage protection of the UHV AC substation.

In order to improve the intelligent operation level of the motor operation mechanism of 126kV vacuum circuit breaker, A control method of PWM rectifier real-time adjusting drive motor speed is proposed. The equations of motion of Brushless DC motor are given, the speed response characteristic of motor is analyzed, and the controllability of motor is studied. The working principle of PWM rectifier is analyzed, the simulation model of the motor operation mechanism control system is established. The speed curve and stroke curve of motor actuating mechanism are obtained through simulation. Test results show that the closing time difference between the stroke curve of the motor actuator and the preset curve is 1.2ms. By controlling the output voltage of the rectifier, the purpose of the motor actuating mechanism to track the preset curve is realized.

The insulation characteristic of high voltage circuit breaker in cold regions is the basis for the design of high voltage circuit breaker. In this paper, several gas of physical and insulated properties can be used in cold region circuit breaker are compares, CF4 gas was fed to use gas for cold region circuit breaker is obtained. Breakdown experiment of CF4 under typical electrodes was investigated, and the insulation performance of CF4 under short gap is obtained. The necessary basic data of CF4 mixed gas circuit breaker insulation and interruption performance research for cold region are provided.

Vacuum circuit breakers switch off shunt reactors, when the low voltage ride-through (LVRT) experiments are performed in Photo-voltaic (PV) system. Transient over-voltage is occurred and gotten a high amplitude in the experiments. It would cause external insulation breakdown of reactor and equipment damage. Base on circuit theory, this paper focused on factors which impacted on the transient over-voltage in the 35kV PV-LVRT experimental system. And then according to 35kV LVRT experimental line, a simulation model of experimental system was established in ATP/EMTP. The simulation results indicated that the closure value of vacuum circuit breaker the size of invested short-circuit reactance and the size of shunt capacitor were major influencing factors on the transient over-voltage caused by vacuum circuit breaker operation. A 0.1 μF shunt capacitor and a 100Ω shunt resistor could effectively reduce the peak value of transient over-voltage what were set to test point in the experiment.

A kind of monitoring and recording system of mechanical characteristics of high voltage circuit breaker is designed in this paper. The system that has the characteristic with microsecond single point acquisition speed and microvolt level amplitude resolution can collect information data of different mechanical characteristics of high voltage circuit breaker and automatic distinguishing data to fault category to establish the correct information and fault information database, and can monitor seven kinds of mechanical characteristics that include displacement, vibration, current of energy storage motor, current of opening/closing release coil, current of permanent magnet coil, voltage of permanent magnet coil of high voltage circuit breaker with the spring operation mechanism or the permanent magnet operation mechanism, and so on. The system can analysis time domain and frequency domain waveform with wavelet analysis method that have characteristics of multi-resolution analysis, and the ability of characterization the partial information of time domain and frequency domain signal for mechanical characteristics of high voltage circuit breaker. That make the target signal frequency division for removing high frequency noise to get pure signal waveform. The waveform can reflect trend of mechanical movement characteristics of high voltage circuit breaker accurately and clear.

When circuit breaker repeatedly breaks small capacitive current of compensation equipments,serious burning loss phenomenon is placed on the surface of static arc contact, which will lead to changing of contact shape. It may finally result in electric field distortion and adversely affect dielectric recovery characteristic. The mathematical models of electric field and flow field have been established in 126 kV SF6 circuit breaker. According to gas breakdown criterion of the streamer theory, dielectric recovery characteristic curves in the condition of burning loss angle θ=60° and no-burning loss have been researched. Then electric field distributions in various burning loss angles have been calculated. Results illustrate that seriously impacts critical breakdown voltage,maximal reduction is 130% at the distance of 95 mm. Values of point A are increasing along with larger burning loss angles. Compared with non-burning loss, the value is 7.7 times higher in θ=80° when separation of contact is 17 mm.

This paper establishes a model for the conductivity of non-equilibrium dual temperature arc plasma during small capacitive current interruption in a SF6 circuit breaker. Considering the contributions of electron-ion-neutral particle collision frequency and collision cross-section, we obtain the conductivity of SF6 plasma as a function of temperature and pressure and establish a dynamic arc model for small capacity currents. Based on the model, a numerical simulation is performed on the flow field with a load of small current of 1600 A for a 126 kV SF6 circuit breaker. Density, pressure and temperature distributions inside the circuit breaker chamber are obtained. With the electric field inside the same interrupter, dielectric recovery characteristic curves are described. In addition, the effect of arc duration on the dielectric recovery characteristics for small capacitive current is studied and the influence mechanism is discussed.

A novel motor operating mechanism is presented which applied in the high voltage circuit breaker. The new motor is a permanent magnet motor with limited angle and only working in the starting stage. Based on the operation requirement of high voltage circuit breaker, the structure and parameters of motor are designed, including the rotor and stator structure, electric load, magnetic load, number of pole pair, air-gap, pole-arc coefficient and etc. The magnetic field analysis and dynamic simulation of motor operating mechanism is achieved by employing the finite element method. The dynamic parameters of motor, such as the torque, current, speed and location is obtained. Finally, the opening and closing stroke curve of moving contact is obtained through the performance testing with the circuit breaker. The results indicate that the motor operating mechanism have a good mechanical characteristics and reach the operation of high voltage circuit breaker.

A limited angle three-phase permanent magnet brushless DC (BLDC) motor operating mechanism for the 126kV high voltage vacuum circuit breaker is proposed and designed. The simulation model of motor operating mechanism is established by using the transient finite element method in according with the counter-force and the moment of inertia. The influence factors of the output mechanical characteristics is calculated and carried out, such as the rotor excitation structure, flux density, pole embrace, length-diameter ratio, turns-diameter ratio of the armature winding under the same poles etc. The simulation results indicated that the type of rotor excitation is employed the inset permanent magnet, which using the radial magnetization, the range of length-diameter ratio is 1.85 to 2.5, the pole embrace is bigger than 0.844, and the turns- diameter ratio of armature winding under the same slot is 14.28 to 23.7. So a larger air-gap flux density about 0.9T can be obtained, and the output mechanical properties parameters (such as output torque, speed and angle) meet with the requirement of circuit breaker.

A novel risk forecasting model of high voltage circuit breaker insulation based on double artificial neural networks is proposed in the paper by analysis of the relationship between ESDD, flashover voltage and environmental factors. The data used to build the forecasting model is obtained from artificial pollution test. The proposed insulation fault risk forecasting model calculates the insulation fault probability under given environmental factors. Results of artificial pollution text indicate that the forecasting of this method is satisfied to practical application and useful to theoretical research.

To improve the accuracy and speed of fault current computation, a variable step size window length adaptive algorithm based on the adaptive filtering theory is proposed in the paper. Digital signal processing algorithm is one of the most important factor for the current protection algorithm. The paper analyzes the principle of the proposed algorithm and the way how to vary the step size and window length. The proposed adaptive algorithm can change the step size of the length changeable window in the filtering algorithm. It is sensitive to fault signals and has a fast response speed, and also have a more efficiently performance. The results of simulations show that the algorithm possesses good performance and is suitable for realizing the fast current protection function to the intelligent high voltage circuit breaker. According to the definite criterions to choosing the fault line, both theoretical analysis and simulation results show that the method has satisfactory reliability and sensitivity.

The mechanical properties monitoring system of permanent magnet motor operating mechanism is developed base on the indoor 40.5kV vacuum circuit breaker in order to improve the security and reliability of power system. The high-precision linear displacement sensor is used to measure the stroke of moving contact, the angular sensor is employed to test the rotation angle of motor, and the hall current sensor is fit for detect the current of armature winding. The digital signal processor (DSP) is designed as the core of the monitoring system and the detection methods of mechanical characteristics are analyzed by considering the principles of the sensor and the signal translation circuit The mechanical parameters of circuit breaker are gained through debugging and running, which it can achieve the function of high precision real-time monitoring of circuit breaker and provide a data platform for the control of operating mechanism in the next step.