Minfu Liao

Experimental Investigation Into the Synergy of Vacuum Circuit Breaker With Double-Break

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.

Initial Plasma Development of Field-Breakdown Triggered Vacuum Switch

A triggered vacuum switch (TVS) is an important component in pulsed power systems due to its quick switch, rapid dielectric recovery, small volume, convenient trigger system, simple structure, etc. A sample of field-breakdown TVS is fabricated, and its turning-on process is described in this paper. The initial plasmas play an important role in the process of TVS operation; its development includes two parts: (1) generation and (2) expansion. Based on the field breakdown principle, an electron emission model is chosen to describe the generation of initial plasmas. A heat conduction model is set up to deduce the expansion of initial plasmas. The model calculated result is accordant with the delay experiment.

Plasma Stability in a Triggered Vacuum Switch

A triggered vacuum switch (TVS) has found fast growing applications in the fields of pulse power system. However, its popularization is still limited due to the trigger stability and accuracy. Research on the trigger process of TVS is one of valid ways to enhance the TVS performances. A sample of TVS was fabricated in this paper. An LC test circuit of two groups of parameters was set up. The trigger pulse parameters were adjustable, and trigger processes were stored by digital oscilloscope and high-speed camera, respectively. Experimental tests were made in three different kinds of trigger power according to the numerical degree. The different trigger power leads to different initial plasmas, i.e., sufficient initial plasma, insufficient initial plasma, and the transition stage between them. The trigger process and its stability are discussed based on the waveforms and photographs. Field emission causes the point discharge of trigger pin and leads to the primary stage of initial plasma. The development of initial plasma is analyzed by theoretical analysis and experimental data. The results show that sufficient initial plasma is a prerequisite for the stability of turning-on TVS, while insufficient initial plasma leads to chopping both in trigger current and voltage when triggering TVS. Sufficient initial plasma can also promote the trigger lifetime and accuracy, with a trigger delay limited in hundreds of nanoseconds.

Experimental investigation on the matching characteristics of vacuum circuit breaker with double-break

In the paper, the prototype of vacuum circuit breaker with double-breaker was set up. In order to find the matching characteristics of VCB with double-break by means of breaking test, the matching characteristics test includes different vacuum gaps, different type electrodes and different grading capacitors. The optimal combination of AMF and TMF type electrodes was gained 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 in lower side is largest because the voltage distribution is most even caused by the different equivalent capacitance of different interrupters. The optimal matching vacuum gaps of the best combination were got by matching characteristics test of different vacuum gaps. The combination of maximum breaking capacity was series AMF type electrodes with suitable grading capacitors. According to the voltage distribution and breaking capacity, the appropriate range of grading capacitors is from 500pF to 2000pF. Moreover, the influence of grading capacitors was discussed by detecting the current of grading capacitors. The research was useful to series VCBs witch replacing SF6 circuit breaker to apply in high voltage level.

Property of 126kV vacuum circuit breaker based on three 40.5kV fiber-controlled vacuum interrupter modules in series

Interest in the application of vacuum circuit breaker (VCB) with multiple breaks arises from technical and economic considerations. Based on analysis on previous work, a 126kV VCB with triple breaks based on fiber-controlled vacuum interrupter modules (FCVIMs) in series is presented in this contribution. A FCVIM is composed of its own outer insulation, vacuum interrupter, permanent magnetic actuator with its controller and power supply. In order to make a VCB with multiple breaks that can be used for higher voltages, the fiber-controlled vacuum interrupter module can be placed in series just like the building blocks. The fiber-controlled technology is used to control the modules at the low voltage area while permanent magnetic actuator operates at the high voltage area. The VCB with double or triple breaks based on FCVIMs in series were set up for research to obtain the dielectric and breaking capacity property. Dielectric experiments were carried out on a single break FCVIM and the VCB with triple breaks based on FCVIMs in series under lightning impulse voltage. It shows that the 126kV VCB with three breaks in series has a higher breakdown voltage improvement factor. As a result, the breaking capacity was verified and the VCB with triple-breaker are eligible to be applied in the power system.

Study on breaking characteristics of high voltage hybrid circuit breaker

The theory of improving the breaking ability of hybrid circuit breaker based on the vacuum interrupter and SF6 interrupter in series was discussed, the dielectric recovery process of two interrupters in hybrid circuit breaker were analyzed, the breaking capacity between SF6 circuit breaker and hybrid circuit breaker based on the same SF6 circuit breaker and vacuum circuit breaker in series were compared. Combination with the improve mechanism of breaker capacity, the requirements of hybrid circuit breaker actuator control mechanism were proposed. Finally, an experimental model of hybrid circuit breaker based on fiber-controlled vacuum circuit breaker modular and SF6 circuit breaker modular in series was designed. The experimental model can satisfies the research requirements of the breaking capacity gain characteristic at the different coordination moment between vacuum circuit breaker and SF6 circuit breaker. Experiments prove that the time dispersion of coordinated action in the microsecond level.

Study on dynamic arc model for high voltage hybrid circuit breaker using vacuum interrupter and SF6 interrupter in series

Hybrid circuit breaker, consisting of a vacuum interrupter and an SF6 interrupter in series, which take the place of single SF6 circuit breaker, is a research area to low-carbon technology for high-voltage switch. In this paper, the model simulation system of hybrid circuit breaker was established by Alternative Transients Program. The system simulation model establishment mainly includes building the electromagnetic transient simulation platform, setting system circuit parameter, improving SF6 arc model and vacuum arc model, whose parameters were obtained by program calculating. The aim of this paper was to investigate the interactions of vacuum arc and SF6 arc during the breaking process, the voltage distribution of the two breakers, the gain characteristics of the coordination action between two breakers by simulation. The results of simulation showed that vacuum interrupter cooperates with SF6 interrupter well in the current zero period, and a higher breaking capacity can be obtained. The results of simulation were in accordance with the theoretical prediction and prove the validity of theoretical model very well.

Influence of the AMF Arc Control on Voltage Distribution of Double-Break VCBs

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.

Controlled Switching of Shunt Capacitor Banks with Vacuum Circuit Breaker

Controlled switching has been used extensively throughout the whole world for shunt capacitor banks. By precisely controlling where on the voltage waveform the contacts touch, it is possible to greatly reduce the magnitudes of the switching electrical transients. This paper presents the basic principle and the software algorithms of controlled switching for three-phase shunt capacitor banks with ungrounded neutral. The stringent performance requirement of the controlled vacuum circuit breaker with independent-pole-operated permanent magnetic actuator (PMA) and the synchronous controller based on the digital signal processor TMS320LF2407A that switching target tolerances should be within plusmn1ms was achieved. Numerous successful switching experiments on the 12kV voltage system demonstrated the well performance of the controlled switching system

Post-arc current measurement based on current transfer characteristic

The paper proposes a novel post-arc current measuring equipment (PACME), which is composed of vacuum switch, transfer resistance, protective gap and high-precision current sensor. The principle of the measurement is based on current transfer characteristic between the vacuum switch and transfer resistance. The current-transfer model of the post-arc current measurement is established to gain the characteristic of vacuum arc conductance and the completion time of current transfer influenced by the transfer resistance, current of main circuit and the contacts opening time. The vacuum arc of PACME extinguished just before the main current approach zero while the main current is completely transferred to the transfer resistance. According to the simulation result, the PACME is designed, especially; the transfer resistance is non inductive and over current protection. The post-arc current of vacuum switch with axial magnetic field (AMF) and transverse magnetic field (TMF) contacts was measured in synthetic short-circuit test. The measuring result of post-arc current is accurate and small interference, which satisfied the post-arc current measurement of vacuum circuit breakers.