A key challenge for multi-break vacuum circuit breakers (VCBs) in gas-insulated switchgear (GIS) is the design of compact voltage grading solutions for vacuum interrupters (VIs). This paper addresses the non-uniform voltage distribution across VI shields and series-connected breaks in VCBs that is caused by the significantly increased stray capacitances in GIS. To address these issues, we propose a novel self-voltage sharing capacitor pattern (SSCP), and the equivalent circuit of the VI with SSCP is analyzed. Simulations of the SSCP and the conventional grading capacitor pattern (CGCP) were conducted, and the maximum external electric field strength of the VI with SSCP was reduced by 53.6%, while the temperature rise was also decreased by 33.9%. A 40.5-kV VI prototype with SSCP was developed based on ring capacitors, external shields, and integrated encapsulation. Experimental results for series-connected VIs with SSCP demonstrate that the potential distributions among the shields and breaks approach the ideal values. The withstand voltage of series-connected VIs with SSCP is increased by 12.5%, and the temperature rise is decreased by 32.2%. The feasibility of the VI with SSCP has been verified, providing a compact voltage-sharing design reference for ultra-high-voltage multi-break VCBs in GIS.

Self-voltage sharing capacitor pattern (SSCP) could meet the compact uniform voltage distribution demand of tank multibreak vacuum circuit breakers (VCBs). However, the consistency analysis of postarc sheath evolution in series-connected breaks with grading capacitors has drawn little attention in previous studies. This article focused on the dynamic development of postarc currents in series-connected vacuum interrupters (VIs) with various grading capacitor patterns. The concept of series-connected sheath consistency was introduced to quantitatively characterize the postarc sheath enhancement effect in series-connected VIs with SSCP, and the particle-in-cell (PIC) computational model was established. Furthermore, the influence of series-connected breaks, shield potential, and contact distance on postarc sheath evolution was investigated, which indicated that SSCP could affect the evolution process of postarc currents, sheath potential, and sheath thickness. Compared to conventional grading capacitor patterns (CGCPs), the postarc current peak was reduced by 20%. The maximum value of the consistency coefficient of SSCP is 0.20 (the ideal value is 0) in series-connected breaks. This article could be used for the evaluation of postarc sheath evolution consistency of series-connected SSCP, which promotes the advancement of ultrahigh-voltage multibreak tank VCBs.

Environment-friendly tank multibreak vacuum circuit breakers (TMVCBs) are a promising alternative to SF6 circuit breakers for high-voltage applications. However, the static and dynamic voltage distribution mechanisms among series-connected breaks in TMVCBs remain insufficiently understood. In this article, the static and dynamic voltage distribution characteristics of environment-friendly TMVCBs were investigated. A finite-element electric field model of environment-friendly TMVCBs was established to obtain the static voltage distribution among breaks, and the nonuniform static voltage distribution is discussed by solving the equivalent capacitance parameter matrix. Subsequently, the modified Langmuir postarc current model was proposed, and the influence of the main shield on the postarc current of vacuum interrupters under a tank structure was analyzed, which demonstrated the dynamic voltage distribution mechanism of TMVCBs. Based on the voltage distribution analysis and a grading capacitor comparison, the interruption tests of a 126-kV environment-friendly TMVCBs were conducted to validate the proposed static and dynamic voltage distribution mechanisms, which also provided the guidance for the grading capacitor design of TMVCBs at ultrahigh voltage and extrahigh voltage levels.

High-voltage vacuum circuit breakers (VCBs) are a crucial approach to the environment-friendly replacement of SF6 in power switchgear. However, the nonuniform voltage distribution of the multiple floating shields (MFSs) in high-voltage vacuum interrupter (VI) has hindered their development. In this article, we propose a new "self-voltage sharing" mechanism for MFS of high-voltage VCBs in series-connected gas-insulated switchgear (GIS). To analyze the mechanism of self-voltage sharing, a new self-voltage sharing capacitor pattern (SSCP) of high voltage VI is developed. The voltage distribution of MFS in conventional grading capacitor pattern (CGCP) and SSCP is calculated. The power frequency voltage distribution and voltage withstand test are conducted to verify the effectiveness of the self-voltage sharing mechanism. The results show that the SSCP can optimize the voltage distribution of the MFS in VI. When two 126 kV VIs are series-connected, the ring capacitor needs to be 4000 pF to meet the voltage distribution requirements of the MFS. When the grading capacitor reaches 4000 pF, the enhancement effect of SSCP is 9.4% compared with CGCP. This article aims to identify the voltage distribution mechanism and realize engineering application for double-break high voltage VCBs in GIS.

High voltage environment-friendly tank circuit breakers impose significant challenges on the internal and external insulation performance of vacuum interrupters, whereas vacuum interrupters adopting the self-voltage sharing design can meet the requirements for compact insulation and effective voltage sharing in tank circuit breakers. However, the surface flashover characteristics of self-voltage sharing vacuum interrupters have not been comprehensively investigated. In this paper, the surface flashover simulation model of vacuum interrupter is established, and the influence of self-voltage sharing regulation methods on surface flashover characteristics is analyzed. In addition, the surface flashover voltages of vacuum interrupter ceramic along gas/solid interface are obtained under various regulation methods through experimental device, and the streamer evolution is captured by a high-speed camera. The results show that the surface flashover voltage is increased by 18.8% with the self-voltage sharing regulation methods. Moreover, the surface flashover process and streamer evolution are discussed, which reveals the mechanism of enhancing surface flashover voltages of vacuum interrupters with the self-voltage sharing regulation methods. The results can provide a reference for optimizing the surface insulation performance of vacuum interrupters in environment-friendly gas insulation switchgear.

The contact magnetic fields of vacuum interrupter are crucial for the stable operation of vacuum circuit breakers (VCBs). However, little attention has been devoted to the influence of contact magnetic fields on the post-arc residual plasma dissipation process in previous study works. To investigate the impact of different magnetic field control on the post-arc residual plasma dissipation process, we proposed a novel probe diagnostic method and a magnetic field control device. A new experiment system for post-arc residual plasma probe diagnostic and external pulse magnetic field control circuit was established. Then, the new diagnostic method is applied to investigate the post-arc residual plasma dissipation process in radial magnetic field (RMF) and axial magnetic field (AMF) of VCBs. The evolution of the vacuum arc and the extinction locations of cathode spots were observed using a high-speed CMOS camera. This research shows that compared to RMF arc control, AMF exhibits a lower initial electron density (4.78 x 1010 cm-3) and a shorter electron density decay time (35 mu s). The results of this study agree with prior optical diagnostics and are consistent with the development trends of post-arc residual plasma. This paper can verify the diagnostic effects of the post-arc residual plasma in vacuum interrupter under magnetic field control. It provides a low-cost probe technique for diagnostic of post-arc residual plasma in VCBs.

Environment-friendly tank vacuum circuit breakers utilizing vacuum interruption and environment-friendly gas insulation are considered an effective approach to replace SF6 circuit breakers. However, surface flashover along the gas–solid interface of the vacuum interrupter in dry air is one of the obstacles for expanding the application of tank vacuum circuit breakers. Thus, a simulation model of surface flashover along gas–solid interface of the vacuum interrupter is developed in this paper. The effects of two improving methods — installing the shielding and setting the main shield potential to 50

Achieving compact design with high insulation performance is a critical challenge for vacuum interrupters (VIs) in eco-friendly gas-insulated switchgear (GIS). This article addresses the severe nonuniform of potential distribution across the multiple floating shields (MFSs) in VIs for GIS by proposing a novel self-voltage sharing capacitor pattern (SSCP), which integrates grading rings and ring capacitors on the exterior of the VI. The simulation results show that, compared with the conventional VI, the SSCP improves the potential distribution on the MFS by 21.64%, 13.07%, and 6.05%. Furthermore, it achieves a 24.60% reduction in the maximum internal electric field strength and a 35.21% reduction in the external field. To validate these findings, an experimental platform was established for a 145-kV VI. The experimental results regarding the influence of grading capacitance on potential distribution are consistent with the simulation trends. Specifically, with a grading capacitance of 2000 pF, the MFS potential distribution reaches 74.95% $U$ , 48.87% $U$ , and 22.63% $U$ , closely approximating the ideal linear distribution. This research provides a theoretical basis and an optimized structural design for enhancing the insulation performance of high-voltage VIs in GIS.

Non-uniform dynamic voltage distribution (DVD) across series-connected breaks is a critical factor limiting the development of multi-break vacuum circuit breakers (VCBs) towards higher voltage levels. However, the mechanism underlying the non-uniform DVD across the series-connected breaks remains unclear. An equivalent circuit model of double-break VI was proposed in this paper based on the post-arc plasma transport characteristics derived from Particle-in-Cell (PIC) method, considering the effects of charge collection of the shields and middle electrode. Based on the established model, the charge collection characteristics under varying initial plasma densities were investigated, yielding a quantitative relationship between the charge collection on the shields and middle electrode and the resulting DVD. The study reveals that non-uniform charge collection by the shields and the middle electrode alters the charge state of external grading capacitors, significantly affecting the DVD. Quantitative analysis indicates that at an initial plasma density of 1×1017 m-3, a 1000 pF grading capacitor reduces the voltage sharing non-uniformity to 9.4%. The accuracy of the model was validated by the strong consistency between simulation results and experimental measurements. This work provides a theoretical reference for research on the mechanism of series DVD in high-voltage vacuum switches.

High-frequency, fast-rising nanosecond pulses have attracted considerable interest in various fields, particularly for driving dielectric barrier discharge plasma jets. The rapid reverse cutoff of diodes enables the diode opening switch (DOS) to generate ultrashort nanosecond pulses. However, it relies on small resistors and a high-power dc source for high-frequency operation, leading to low charging voltage gain and significant charging losses. Additionally, the limited controllability of diodes makes it difficult to adjust output polarity. Herein, a new DOS utilizing GaN with LC charging (L-DOS) is proposed. An inductor stores energy that is dissipated in the charging resistor of traditional DOS, achieving a higher charging voltage gain. Additionally, a new modular L-DOS circuit with IGBT isolation is designed. IGBT provides a controlled current path for the fast-rising pulses generated by the diodes, allowing for bipolar output with adjustable stacking. Results show that L-DOS achieves a fivefold increase in charging voltage gain with only 25% of the charging loss of traditional DOS, thereby enabling the generation of 5.8-kV pulses with a duration of 6.8 ns under a low input voltage of 100 V. The 4-stage prototype can not only output bipolar pulses but also achieve amplitude stacking up to 10.6 kV and bipolar frequency stacking up to 2 MHz.

With the proposal of carbon peak and carbon neutrality target, the tank multi-break vacuum circuit breakers with environment-friendly gas insulation is an effective methods to replace SF6 gas in the field of high voltage and ultra-high voltage. Firstly, the electric field simulation of tank multi-break vacuum circuit breakers is carried out. The scale test electrode is designed for the key position according to the electric field distribution, and the lightning breakdown test with different pressures, electrode distances and electrode structures are carried out. The results show that 0.9 MPa dry air and 0.9 MPa CO2 can satisfy the insulation configuration requirements of the tank multi-break vacuum circuit breaker. In addition, the surface flashover characteristics of the ceramic shell interface of vacuum interrupter are studied, the effects of gas pressure, metal particle attachment location on the surface flashover voltage of the ceramic shell are investigated, which provides guidance for the development of vacuum interrupters in ultra-high voltage field.

To meet the compact voltage-sharing configuration requirements of high-voltage multi-break tank vacuum circuit breakers, a simulation study on post-arc particles in a double-break series vacuum interrupter under main shield voltage-sharing was conducted. A PIC computational model for the post-arc phase in a double-break series vacuum interrupter under main shield voltage-sharing was established, revealing the variations in post-arc particles, post-arc potential, post-arc current, and post-arc sheath thickness. The study indicates that main shield voltage-sharing affects the development of the post-arc sheath in the double-break series main shield voltage-sharing vacuum interrupter. Compared to the traditional break voltage-sharing method, the main shield voltage-sharing method resulted in the smallest peak value of post-arc current (10 A) and the best consistency in sheath development between the series breaks (consistency coefficient approaching 0). This research provides valuable reference for the design of series main shield voltage-sharing vacuum interrupters in multi-break tank vacuum circuit breakers.

Under the Paris Agreement and Dual Carbon Goals, environment-friendly tank multi-break vacuum circuit breakers, which utilize dry air insulation and vacuum interruption, has become the effective approach to replace SF6 circuit breakers in high-voltage filed. However, the surface flashover along vacuum interrupter insulator surface in dry air is one of the obstacles for expanding the application field of vacuum circuit breakers. Thus, this paper investigates the surface flashover characteristics of vacuum interrupters, and the surface flashover mechanism along vacuum interrupter insulator surface is analyzed considering the influence of main shield. The surface flashover simulation was conducted, and the electron density distribution is obtained, which shows that the surface flashover development process of vacuum interrupter with main shield on insulator surface is accelerated. The surface flashover experiments are performed under various conditions, and the surface flashover voltage of vacuum interrupters is reduced with main shield on insulator surface, which validated the surface flashover mechanism analysis.

—The environment-friendly tank multi-break vacuum circuit breaker has been regard as the promising method to replace SF6 circuit breaker in high voltage field. Nevertheless, the complicated insulation configuration demand have not been concerned comprehensively, and the feasibility of applying environment-friendly gas as insulation medium in tank multi-break vacuum circuit breakers has not been verified. In this paper, the electric field distribution of tank multi-break vacuum circuit breakers is obtained and the insulation weakness area is discovered. Furthermore, The breakdown experiments of C4F7N/CO2 mixtures, dry air and CO2 are conducted under quasi-uniform electric fields through the gas-insulated experimental device. The AC and DC breakdown characteristics of these insulation gases are gained under various gas pressure, mixing ratio and nonuniform coefficient. Meanwhile, the critical breakdown electric field strength of environment-friendly insulation gases are calculated. The application sensitive of insulation gases has been discussed through polarity effect and arc streamer evolution. Furthermore, the prototype construction and insulation test verify the feasibility of the insulation configuration method. The results can provide a basis for environment-friendly gas-insulated circuit breakers.

Gas Insulated Switchgear (GIS) was a crucial electrical equipment that provides the safety and security of power systems, and finding the eco-friendly alternatives of sulphur hexafluoride (SF6) as insulating medium in GIS has been an urgent demand in past decades. However, few studies reported the specific dielectric strength under various electrodes and partial discharge (PD) decomposition products detection of applying the eco-friendly gas in GIS. In this paper, the insulation properties among C4F7N/CO2 mixtures, dry air and CO2 were explored under the reduced-scale gas-insulated experimental device. The relationship between AC breakdown voltage and gas pressure was gained under the different electrodes and gap distances, and 0.6 MPa 7% C4F7N/93% CO2, 0.9 MPa dry air, 0.9 MPa CO2 all possess the capacity to be the insulating medium in eco-friendly gas insulated switchgear. Furthermore, the partial discharge experimental was also carried out to realize the decomposition products detection of dry air, which designs three common defect types including metal protrusion defects, air gap defects, and metal contamination defects. The decomposition products detection result shows that the contains of CO2, CO, and NO2 linearly increase with the increasing applied voltages and times, and the partial discharge defects are distinguished according to the ratios of c(CO2 + CO)/c(NO2) and c(CO2)/c(CO). The results can provide the basis for the further development of eco-friendly gas insulated switchgear.

This paper analyzes the principle of insulation gain in high voltage vacuum interrupter with series-connected asynchronous interlinking between main and auxiliary gaps, focusing on a newly integrated structure. A simulation prototype of the vacuum interrupter with asynchronous interlinking between the gaps was constructed. The study explored how variations in the gap opening distances at different incoming line ends affect the voltage distribution and conducted experiments on the breakdown characteristics of series-connected main and auxiliary gaps. The findings indicate that the voltage distribution on the high-voltage side is higher, and the proportion of the total voltage attributed to the main gap increases with its widening and decreases as the auxiliary gap widens. Voltage partitioning measures significantly mitigate the impact of stray capacitance, ensuring a 2:1 voltage distribution ratio between the main and auxiliary gaps. When the moving end of the vacuum interrupter is the incoming line end, the insulation of the integrated structure of the main and auxiliary gaps improves by 16.25% compared to a single chamber with a gap of 15 mm, and with voltage partitioning measures, the insulation gain of the prototype is approximately 1.17, indicating substantial insulation enhancement. The research provides valuable guidance for the development of high-voltage vacuum arc-extinguishing chambers, with the potential to realize units for voltage levels of 252kV and above.

The grading capacitor is a conventional method to guarantee the uniform voltage distribution (VD) of double-break vacuum circuit breakers (VCBs). However, the main shield voltage unevenness problem of each vacuum interrupter drew little attention in previous study. This article focused on the voltage sharing of the main shield and designed a novel grading capacitor pattern. A dynamic charge compensation (DCC) theory was proposed, which was derived from the novel grading capacitor pattern. Subsequently, an equivalent circuit model, which contained the influence of the DCC, was established for dynamic VD of double-break VCBs. The tests were performed in a synthetic test circuit, and VDs with different grading capacitors patterns were compared, respectively. The results showed that the novel grading capacitor pattern could not only improve the main shield VD but also enhance the effect of balancing the VD ratio between interrupters. The images of cathode spots extinction process correlated the initial condition with postarc sheath growth process. With 83-pF grading capacitors, the compensation effect could reach nearly 50%. Theoretical analysis and test results show the feasibility of the novel grading capacitors pattern, which provides a candidate to put VCBs toward transmission voltage.

The natural transfer time of medium-voltage large-capacity hybrid DC circuit breaker is long or even fails. Therefore, this paper proposes a hybrid DC circuit breaker topology based on vacuum and gas integrated series switch, and analyzes the basic principle of vacuum and gas integrated series for current transfer performance. The experimental prototype of vacuum and gas integrated series switch in medium voltage field is designed by double over-range linkage operation structure. The influence of gas type, pressure, contact structure and contact material on arc voltage characteristics is studied. The W70 Cu bridge two contact structure, hydrogen and nitrogen mixed gas (H2: $\mathrm{N}_{2}=2:3$ ), pressure 0.3MPa and other related parameters are determined. The arc voltage can be increased from 20 V to 121 V, and the current transfer time is reduced to 1/6 of the original. The feasibility and effectiveness of vacuum and gas integrated series switch applied to medium voltage hybrid DC circuit breaker are verified.

The uneven potential distribution of the multi-stage suspension shield in high-voltage vacuum interrupters has a significant impact on the breaking process, in order to investigate the effect of shield voltage equalization configuration on the post arc particle transport characteristics, this paper constructs a 126kV self-voltage sharing vacuum interrupter PIC (Particle In Cell) model. The influence of shield voltage equalization configuration on the macroscopic electrical parameters and microscopic particle movement process in the post arc stage of the 126kV vacuum interrupter with single-break and double-break is studied. The post arc current, post arc electric field, sheath development and particle transport dynamics were analyzed. The results show that for the 126kV single-break vacuum interrupter, the shield equalization configuration can reduce the post arc current, optimize the distribution of the post arc electric field and accelerate the development of the post arc sheath, among which the self-voltage sharing configuration using multi-stage suspension shield voltage equalization has the best effect. Secondly, for the 126kV double-break vacuum interrupter, the self-voltage sharing configuration can not only reduce the post arc current, accelerate the development of the sheath and improve the electric field distribution, but also make the development of the sheath of the two breaks more synchronized, which is more favorable for the post arc dielectric recovery process of the series vacuum interrupter. The research work in this paper has a certain guiding significance for the study of the development of high voltage level self-voltage sharing vacuum interrupters.

The mixed gas technology of sulfur hexafluoride (SF6) gas and nitrogen (N2) gas for gas insulated switchgear (GIS) has been proven to be an effective method to the traditional GIS with single sulfur hexafluoride (SF 6 ) gas, which can effectively reduce carbon emissions. However, for GIS equipment using mixed gas technology, the characteristic components of internal decomposition products under different partial discharge types are not clear. A rapid diagnosis and analysis method of internal decomposition products after partial discharge in GIS field is proposed, and four typical partial discharge defects of GIS equipment, namely metal protrusions, metal contamination on insulator surface, air gap between metal and insulator, and suspension discharge, are investigated by building a test platform, respectively. Characteristic components and the trend of discharge voltage and discharge amount, which provide a potential solution for accurate and rapid evaluation and diagnosis of equipment defects.