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This paper studies the degradation effect of high-concentration toluene in dielectric barrier discharge (DBD) plasma under different operating conditions. The degradation efficiency and energy yield (EY) were comprehensively evaluated by a response surface method under different operating parameters (discharge powers, gas flow rate, and initial concentrations) in the DBD plasma system. The results showed that the EY and degradation efficiency could reach 22.17 g kWh−1 and 72.3% when discharge power, initial concentration, and gas flow rate were 5.49 W, 1374.5 ppm, and 529.5 ml min−1, respectively. Furthermore, a mineralization effect was also analyzed related to different operating parameters. When the gas flow rate was 600 ml min−1 and the initial concentration was 2500 ppm, the CO x selectivity could reach 98.5%. Through analysis of the effect of oxygen content in the background gas on high-concentration toluene degradation, it was found that oxygen content had a significant effect on the formation of oxygen-containing active substances. Emission spectra showed that normal air discharge occurred in the discharge space of the DBD plasma, and nitrogen-containing active substances were generated. Therefore, active substances containing oxygen and nitrogen played an important role in DBD plasma degradation of high-concentration toluene. [ABSTRACT FROM AUTHOR]

This article proposed a current commutation regulation (CCR) connected in parallel with a CO2 gas circuit breaker (GCB) in order to improve the dielectric recovery characteristics (DRC). The structure and principle of the CO2 GCB with CCR are proposed and analyzed. The CCR is composed of serial-connected thyristors and a current-limiting resistor. The current of the CO2 GCB will decrease to zero before the main current zero so that there is a zero-current duration between the current zero of the CO2 GCB and the main current zero, which supplies more recovery time for DRC of CO2 GCB. The DRC test platform of the CO2 GCB with or without CCR is set up. The current commutation characteristic is analyzed and tested. The effect of the CCR on the zero-current duration and the DRC of the CO2 GCB is gained by adjusting the applied time of the negative pulsed voltage. The results show that the CCR can create a zero-current duration of 0~1.5 ms, and the DRC of the CO2 GCB can be increased to twice when the zero-current duration is 0.8 ms. The current commutation characteristics and effects of CCR are verified. This article provides a new method to improve the DRC of the CO2 GCB, which is useful for the application of SF6 alternative gas. [ABSTRACT FROM AUTHOR]

At present, multibreak vacuum circuit breakers (VCBs) have attracted more attention in order to meet the requirement of the environmental protection, high-voltage VCBs, capacitive current switch-off, and the dc current breaking. The advantages and disadvantages of multibreak VCBs are analyzed and discussed according to the research status. Then, the synergy effect of multibreak VCBs is proposed, which is the interaction among the arc memory, current zero characteristic, and the postarc characteristic. The target of the synergy effect is the synergy between the dynamic dielectric recovery strength and the postarc dynamic voltage distribution. The maximum breaking capacity can be obtained in the above-mentioned synergy control. Finally, the optimization design, key technology, basic theory, and application of multibreak VCBs are discussed. With the development of multibreak VCBs, it will be widely used in high-voltage level, HVdc, and pulsed-power switchgear in the future. [ABSTRACT FROM AUTHOR]

This paper proposes the equivalent circuit of postarc dynamic voltage distribution (PDVD) in multibreak vacuum circuit breakers (VCBs). The equivalent circuit is composed of controlled postarc sources, postarc resistors, and equivalent capacitors. The sheath growth and the postarc process of double-break VCBs are analyzed. The PDVD is divided into four processes: the initial transient recovery voltage (TRV) process, the oscillating TRV process, the stable TRV process, and the power-frequency voltage process, which can be analyzed by the equivalent circuit. The novel equivalent circuit of the PDVD in multibreak VCBs is gained by introducing the controlled postarc current source. The test platform is set up in the synthetic circuit. The postarc current, grading capacitor current, and the TRV are measured to analyze the PDVD in the above four processes. The test results verify the theoretical analysis. Therefore, the mechanism of the PDVD in multibreak VCBs is obtained and described by the equivalent circuit, which is useful to gain even voltage distribution and improve the breaking capacity of multibreak VCBs. [ABSTRACT FROM AUTHOR]

When double‐break vacuum circuit breakers (VCBs) interrupt the fault current, the series arc will generate their individual magnetic fields in different breaks. The magnetic field in one break will influence the arc in another break if the magnetic field is strong enough or the two breaks are very close. In this case, an interactive magnetic field effect happens. This field is also called the bias magnetic field (BMF). BMF can cause anode erosion and affect the performance at current zero. The distribution of BMF and the optimal configuration of the double‐break VCBs were obtained by the electromagnetic field simulation using the Ansoft Maxwell software. Based on the simulated magnetic field data, in the experiments, the interaction between the series vacuum arcs in double‐break VCBs was equivalent to the interaction between a single vacuum arc and the magnetic field generated by a Helmholtz coil. A high‐speed CMOS camera was used to record the trajectory of the vacuum arc plasma under different BMFs with different types of contacts. The results show the BMF can increase the arc voltage, and the arc becomes unstable. When the BMF becomes stronger, the arc voltage increases, and the arc becomes more unstable. In addition, for different types of contacts, the development process of the arc and the influence level are different under the same BMF. For a Wan‐type transverse magnetic field (TMF) contact or strong BMF, metal sputtering is evident and anode erosion becomes serious. For a cup‐type axial magnetic field (AMF) contact, the influence of BMF on the series arc plasma in double‐break VCBs is less than that of the Wan‐type TMF contact. The results of this work may be helpful for the design of compact double‐break VCBs. [ABSTRACT FROM AUTHOR]

In order to reveal the mechanism of the residual magnetic field in vacuum interrupters (VIs), the vacuum arcs and the postarc characteristic with external AMF at current zero are investigated. The magnetic field of the 10-kV/20-kA VIs is analyzed. And then, the phase shift and the residual AMF are obtained. The test platform is established in the synthetic test circuit. The pulsed AMF is applied at current zero with the pulsewidth of 4 ms, and the magnitude can be adjusted from 0 to 200 mT. The transparency VIs with external AMF at current zero is observed by the high-speed CMOS camera to analyse the vacuum arcs development. The postarc current and transient recovery voltage are measured by the postarc current measuring equipment and the voltage divider so that the postarc characteristic such as postarc current and postarc charge can be obtained. The influence of the pulsed AMF at current zero on the vacuum arc development and postarc characteristic is gained and the mechanism of the AMF at current zero is analyzed, which can be useful to special AMF contact design for different applications. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamic dielectric recovery synergy (DDRS) of hybrid circuit breakers (HCBs) with CO2 gas and vacuum gaps in series. The interaction between the vacuum arc and CO2 gas arc is simulated by the continuous transient arc model and Mayr arc model. The simulation results indicate that the extra methods, for example, dividing capacitors, are needed to obtain optimal DDRS of HCB. The prototype of HCB and the test circuit are established. The influence of the coordination of arcing time, dividing capacitors, and the CO2 gas pressures on the transient recovery voltage (TRV) distribution and the breaking capacity is investigated. The differences of HCBs with SF6 gas and CO2 gas are also compared. According to the results, favorable DDRS in HCB can be obtained in the condition that the vacuum gap endures the initial TRV while the following major TRV distribution is mainly depended on the dynamic dielectric in CO2 gas gap. However, the dynamic dielectric recovery of CO2 gas gap is limited by the structure of rotating arc CO2 gas interrupter in this paper. In the future, the interruption capacity of HCB based on CO2 gas can be improved by synergy control, as the development of CO2 gas circuit breakers. [ABSTRACT FROM PUBLISHER]

This paper focuses on the vacuum arc commutation between the vacuum arc and the parallel-connected insulated gate bipolar transistor (IGBTs) of dc microgrid hybrid circuit breakers (HCBs). The principle of the dc HCB is analyzed and the vacuum arc commutation is the important process in dc HCB interruption, in which the arcing time and the interrupting time are depended. The test circuit of the vacuum arc commutation is established by simplifying the parallel-connected IGBTs to an on-state resistance with large thermal capacity. The influence of the magnitude of the main current, the resistance of the IGBTs, and the externally applied transverse magnetic field (TMF) on the vacuum arc commutation is investigated by the electrical measure and the development of vacuum arc which is observed by a high-speed CMOS camera. The criteria of the vacuum arc commutation are obtained. The interaction between the vacuum arc commutation and the externally applied TMF is researched and the optimal magnitude of the TMF is gained. The vacuum arc commutation characteristics of dc HCB can be useful for parameters design and control strategy. [ABSTRACT FROM PUBLISHER]

This paper focuses on the vacuum arc commutating characteristic (VACC) between the parallel-connected vacuum arc and the shunt resistor, which is the base of the postarc current (PAC) measure. The test platform is established in the synthetic test circuit. The influence of the current magnitude, shunt resistor, arcing time and current frequency on time of the current commutation and the current in the moment of the completion transition is investigated. The mathematic description of the VACC is obtained, which is useful to parameter design of the PAC measure. The PAC of 10-kV vacuum circuit breakers is measured in synthetic test circuit. The photos of the vacuum arc and the waveform of the current commutation are gained to verify the success of the commutation. In conclusion, the VACC is gained and applied to measure the PAC. [ABSTRACT FROM PUBLISHER]

This paper investigates the influence of the axial magnetic field (AMF) arc control on voltage distribution (VD) of double-break vacuum circuit breakers (VCBs) in order to gain balanced VD, and thus enhance the breaking capacity. The interaction of vacuum arc plasma, postarc current (PAC), and AMF is discussed. We conduct the breaking test of double-break VCBs with externally applied AMF of a different pulsewidth, magnitude, and a different moment. The PAC, postarc charge, and the VD are measured to analyze the relationship between the AMF arc control and the VD. The optimal AMF arc control and the relationship between the AMF magnitude and the unbalanced voltage ratio are gained when the grading capacitors were 400 pF. The experimental test showed that the proper AMF arc control can improve the unbalanced VD. The mechanism is that the proper AMF arc control can make the postarc charge small and stable, so the unbalanced postarc charge, which caused the unbalanced VD is limited. [ABSTRACT FROM AUTHOR]

In order to find the synergy of double-break vacuum circuit breakers (VCBs), we conducted a synthetic test including different vacuum gaps, different type electrodes, and different grading capacitors. The double-break VCBs are composed of Axial Magnetic Field (AMF) and Transverse Magnetic Field (TMF) contact VCBs, which can constitute four combinations. The optimal combination of AMF and TMF type electrodes was obtained by comparing with the breaking capacity and voltage distribution of the four combinations. The breaking capacity of double-break VCB with AMF and TMF type electrodes in series while the AMF interrupter is on the lower side is largest because the voltage distribution is the most even which is caused by the different equivalent capacitances of different interrupters. The optimal matching vacuum gaps of the best combination were obtained by a synthetic test of different vacuum gaps, which may make the grading capacitors of double-break VCBs small, even obsolete. The combination of maximum breaking capacity was series AMF type interrupters with suitable grading capacitors of 500–2000 pF. The experimental results provide the best combination and matching control mode for VCBs with double-break. [ABSTRACT FROM PUBLISHER]