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Vacuum interrupter is widely used in the medium-voltage power system. Controlling the arc by the magnetic field is an effective method to improve the breaking capacity. The transverse magnetic field (TMF) forces the constricted arc to rotate to reduce local overheating. In this paper, three kinds of TMF contacts, which are Swastika-type contact, cup-shaped contact, and double-TMF contact that combines Swastika-type and cup-shaped contacts coaxially, are investigated in a demountable vacuum chamber with a high-speed camera. The arc voltage and current are also recorded. The experiments were conducted with circuit currents from 5 to 20 kA (root mean square) with a frequency of 50 Hz. There are four current levels in the experiment, which are 5, 10, 15, and 20 kA, and at least three tests are taken for each current level. The results showed that under low current (I = 10 kA), the arc of the three TMF contacts did not rotate. Under high current (I = 20 kA), it was observed that the arc of Swastika-type and double-TMF contacts rotated in the gap. The arc speed of double-TMF contacts is higher than that of Swastika-type contacts. The cup-shaped contacts have the highest arc voltage and noise among the three TMF contacts. The Swastika-type contacts were eroded most seriously. The simulation results show the force distribution of the arc on different locations. The resultant force makes the arc rotate counterclockwise.

It is of great significance to achieve good cooperation between the fast vacuum switch driven by the electromagnetic repulsion mechanism and the buffer system. The purpose of this paper is to study the cooperation of the 40.5kV fast vacuum switch driven by the electromagnetic repulsive mechanism and the oil damper. Firstly, the dynamic characteristics of the electromagnetic repulsion mechanism during the opening process were simulated by MAXWELL software. Then, based on the dynamic characteristics of the electromagnetic repulsive mechanism, a simplified model of the oil buffer is established by AMESim software and its cushioning characteristics are simulated. Moreover, the influence of the buffer piston area and the annular gap width on the cushioning characteristics of oil buffer is analyzed. Finally, the dynamic characteristics of the electromagnetic repulsion mechanism under the action of the oil damper are simulated and analyzed. It provides some guidance for the cooperation of the fast vacuum switch driven by the electromagnetic repulsive mechanism and the oil damper.

Circuit breakers are important control and protection devices in power systems and are essential for ensuring safe and reliable operation of power systems. In recent years, the application of fast electromagnetic repulsive mechanism based on the principle of eddy current in vacuum circuit breaker has gradually become a hot research topic. However, due to the large mass of the moving mechanism and the large opening distance in the high voltage vacuum circuit breaker, it is difficult for the ordinary mechanism to break quickly. Therefore, a double-layer coil type fast electromagnetic repulsive mechanism is proposed, which can generate a larger electromagnetic repulsive force to achieve fast driving of the mechanism. Taking the 40.5kV/50kA vacuum circuit breaker as an example, the 2D finite element model was built by MAXWELL software, and its motion characteristics were simulated. In addition, the effect of the metal plate thickness, coil inner radius, number of coil turns and initial gap on the motion characteristics of the fast electromagnetic repulsive mechanism is investigated. The results show that the rise time of the electromagnetic repilsive force is very short. In contrast, the electromagnetic repilsive force has a long time to fall, and the peak value of the electromagnetic repilsive force is large. Thickening the metal plate, increasing the inner radius of the coil plate, increasing the number of coil turns and reducing the initial gap can increase the speed of the rapid electromagnetic repulsive mechanism. The simulation analysis provides a basis for further design of the electromagnetic repilsive mechanism.

Based on the operation of a Ground Source Heat Pump (GSHP) in Hefei, the heat exchange of the 100m depth vertical u-shaped pipe buried in the ground was analyzed, and the heat transfer performance, efficiency of the system and temperature variation of the ground were studied experimentally under the typical climate in Hefei. Temperature changes of the field near the heat exchanger after 8h and 24h were analyzed by numerical simulation. Results show that the system has a good performance in winter.

An improved two-dimensional axisymmetric swirl model based on former work has been developed to describe the detailed physical process in the formation and development of vacuum arc cathode spot. In the current model, the influence of plasma cloud, evaporation, backing ion, thermo-field (T-F) emission, back-diffused electron, self-generated magnetic field and Lorentz force are all considered. External parameters include electron temperature, near cathode voltage drop, average charge number, ion number density, space function and time function. The compositions of current density, energy flux density and external pressure are discussed and the influence of external parameters are studied. Simulation results show that electron current density from T-F emission is the most important component for current density; as for energy flux density and pressure, ion flux from plasma cloud is dominant. Ablation on a refractory metal is much less than that on a fusible metal under the same external conditions. The simulation results are in good agreement with other researchers' results.

In this paper, the arc characteristics of cup-shaped AMF contacts in vacuum arc experiments under different materials was studied. The experiment was conducted in a detachable vacuum chamber with a gas pressure of 10-4Pa. The arc voltage and current were measured at the same time by high-voltage probe and Rogowski coil, and the arc pictures were photographed with a high-speed camera. The cup and the rod of the contact are made of pure copper material, and the contact pieces are selected ten common contact materials for comparison (CuCr10, CuCr 20, CuCr 30, CuCr 40, CuCr 50, WCu10, WCu20, WCu30, CuW-WC). Fixed-distance trigger experiments were conducted with currents of 5kA (rms), 10kA (rms), and 15kA (rms) for each contact. The arc appearance, cathode surface morphology, and anode status morphology were observed. The shape of the arc was analyzed in conjunction with the voltage and current after the experiment. The morphology of cathode and anode surface was analyzed by combining the erosion after the experiment. The effect of various material properties was discussed under the AMF. It’s found that the center of the anode erosion area is approximately hexagonal, and the slot is burned more outward than the plane. WCu contact has better erosion resistance than CuCr contact. For CuCr, the erosion of CuCr30 is the slightest with low depth and small area.In this paper, the arc characteristics of cup-shaped AMF contacts in vacuum arc experiments under different materials was studied. The experiment was conducted in a detachable vacuum chamber with a gas pressure of 10-4Pa. The arc voltage and current were measured at the same time by high-voltage probe and Rogowski coil, and the arc pictures were photographed with a high-speed camera. The cup and the rod of the contact are made of pure copper material, and the contact pieces are selected ten common contact materials for comparison (CuCr10, CuCr 20, CuCr 30, CuCr 40, CuCr 50, WCu10, WCu20, WCu30, CuW-WC). Fixed-distance trigger experiments were conducted with currents of 5kA (rms), 10kA (rms), and 15kA (rms) for each contact. The arc appearance, cathode surface morphology, and anode status morphology were observed. The shape of the arc was analyzed in conjunction with the voltage and current after the experiment. The morphology of cathode and anode surface was analyzed by combining the erosion after the exp...