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Converter transformer bushing as a piece of important power equipment in HVDC transmission, need to withstand AC voltage, DC voltage, and polarity reversal voltage during operation, the complexity of the operating conditions leads to high requirements on the insulation performance of the converter transformer bushing. The dry-type SF 6 gas-insulated DC bushing meets the requirement of no oil in the valve hall, is the bushing of the current mainstream converter transformer, and it uses SF 6 gas as the upper additional insulation. Analyze the electric field distribution in SF 6 gas of converter transformer bushing under different voltages, Especially important for the design of SF 6 gas internal voltage equalization device. This paper selects ±400kV dry-type SF 6 gas insulated bushing as the research object, establishes a simulation analysis model, and uses the finite element analysis method to calculate the electric field intensity distribution of the converter transformer bushing under different voltages. Mainly analyze the distribution law of electric field intensity in SF 6 gas. The results show that under DC excitation, the distribution of equipotential lines in SF 6 gas is relatively concentrated, and the electric field intensity near the top of the capacitor core is the highest. Under the condition of polarity reversal, the electric field intensity in SF 6 gas showed a downward trend.

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.

Through the analysis of the characteristics of most of rural indoor cable routing adopting wall concealed laying and there being more nodes in the lines, for the problems of leakage detection and location of rural indoor cables presenting small leakage current and different cable parameters in the same house, this paper designs a kind of handheld testing device with a certain precision and convenience. According to the magnetic field signal being generated by leakage current, inspection tour method is applied to leakage detection and location of rural indoor cable. The mathematical model of magnetic field generated by current carrying cable is established through Biot-Savart's Law. It is to calculate the size of a magnetic field generated by the leakage current. The leakage points are located by using the magnetic field signal's differences before and after it. Applying MULTISM simulation verifies the feasibility of the signal processing circuit. Set up the testing platform, and measure the magnetic field generated by the current of less than 30mA, and further verified the feasibility of the analog circuit.

Extra-high (EHV) transmission system has the characteristics of high voltage and large capacity, and a high amplitude current will be generated through the grounding line and ground net when failure occurs. Step voltage caused by the diffusion of fault current in soil is an important parameter affecting the normal operation of the system. The calculation and analysis of the step voltage in IEEE Std 80-2000 standard is rough, unable to reflect the soil surface potential distribution in substation comprehensively. This paper present an algorithm combined transmission line theorem and finite element analysis to calculate the electric potential distribution accurately, getting the attenuation law of surface potential and the step voltage. Analysis shows that the soil surface electric potential is well-distributed in normal operation and the step voltage is very small, only a dozen volt; The potential value can achieve kilovolt during short trouble and there will be a great attenuation within one meter; Soil resistivity, earth current amplitude and buried depth of ground net are the important factors influencing the surface potential distribution and step voltage.

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.

In order to improve the lightning calculating accuracy of transmission lines, the impact of surge corona is considered in this paper with the software of Electromagnetic Transient Program (EMTP) and a new improved corona model is proposed. The model is based on the concept of corona's radius. The region between the transmission lines which are under lightning and the ground is divided into corona region and no corona region. The analysis of lightning transient process shows that the influence of the corona is so great that the corona's impact should be taken into account to determine the insulation level. Besides, the effect of the power frequency voltage and the velocity changes are also studied. The simulation results show that considering the power frequency voltage and the smaller velocity due to the surge corona, the voltage of the top of tower is much higher than ignoring them, so these factors should be integrated when determine the insulation coordination for the transmission lines.

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.

In order to improve the performance of circuit-breakers, the influence of different magnetic materials on permanent magnetic actuators'(PMA) exciting current and operating characteristics are researched, and the finite element method(FEM) is used to establish the electromagnetic-mechanical coupled model. The electromagnetic equation, electrical equation and motion equation are solved to study dynamic characteristics of PMA. The yoke iron of PMA is made of cold-rolled silicon steel sheet and electrical pure iron respectively, the curves of the PMA parameters changing with time are obtained. The results show that the PMA with cold-rolled silicon steel sheet has better speed performance and less eddy current loss. A vacuum circuit-breaker with cold-rolled silicon steel sheet PMA is carried out, and in the corresponding experiments the operating characteristics are measured and the exciting current curves are also obtained. It is confirmed that the simulation results are accurate and have a certain actual significance.

In order to study the effect of pollution un-uniform distribution on insulation performance of outdoor insulators, in the paper, the size of the dirt layer conductivity is used to describe the pollution extent of insulators and then the three-dimension harmonic quasi-static electric field of XP-160 insulators under pollution un-uniform distribution is calculated. The effects of different conductivity of dirt layers and several typical pollution un-uniform distributions to the electric field distribution along the surface of insulators are investigated. Comparing the leakage current obtained from artificial contamination test with the results of calculation, the reliability of the model is verified.

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.

The permanent magnet motor, which is applied in the high voltage disconnecting switch, used for reducing the VFTO in the operation of disconnecting switch and enhancing the operating performance, and therefore achieves the opening and closing operation and brings quicker response ability and control performance, is presented. The structure and the parameters of the motor are designed according to the characteristics requirement of 550kV GIS disconnecting switch. The dynamic mathematical model of the motor is developed and the dynamic performance is carried out by using the transient finite element method. The simulation results verify the reasonable of motor design and gain the characteristic curves. The analysis results indicate that the permanent magnet motor have an excellent performance in the sense that it gives an opening or closing speed that meets the requirements of the disconnecting switch. Furthermore, it serves to provide a theoretical base for designing that permanent magnet motor applied in disconnecting switch.

The frequent appearance of switching disconnecting link in the electrical system leads a very large economic loss. A design of on-line monitoring system against ground wire based on GSM (global system of mobile communication) and SMS (short message service) was introduced in this paper. The configuration of the system, operating principle, the construction of the hardware, and the software design etc, were also given. This system realizes remote data communication and the real-time monitoring of ground wire site terminal. (4 pages)

On extra-high-voltage (EHV) power transmission line, the secondary arc influence to power system can't be ignored. The secondary arc is a key factor for success of single-phase auto reclose. The amplitudes of secondary arc current and recovery voltage are two decisive factors to extinguish secondary arc. High speed grounding switch (HSGS) is one of the important electric equipments, which is applied to the power system gradually. HSGS can not only earth when power system is fault, but also extinguish secondary arc current rapidly and reduce recovery voltage. This paper bases on the characteristic of secondary arc in 750 kV system, develops a sort of HSGS. This paper mainly studies the system of contactor of HSGS; calculating pressure, electric dynamic of contactor and the open distance. Finally, the whole mentality of design and the integral structure map of HSGS are shown. (5 pages)