Liao Minfu

Study of a Three-Stage Reconnection Electromagnetic Launcher Using Triggered Vacuum Switches

The reconnection electromagnetic launcher is a type of induction launcher whose propulsive force is the interaction between the eddy current induced in the projectile and the pulsed high magnetic field generated by the coil. A three-stage reconnection electromagnetic launcher system has been fabricated and tested. Box-shaped helical coils are constructed to launch the flat-plate projectile. Capacitor banks are used as the power supplies. Triggered vacuum switches (TVS) are used instead of spark gaps as the closing switches because of the advantages such as small volume, no maintenance and low electromagnetic interference. Owing to the special arc extinguishing performance of TVS, energy saving potential is studied. When the arc extinguishes at the second current zero, the remaining energy of the capacitor banks contributes to higher efficiency

Dielectric strength and statistical property of single and triple-break vacuum interrupters in series

The maximum possible improvement factor of vacuum circuit breaker (VCB) with multiple breaks compared with one-break, which had the same total gap length, was deduced. Based on the research on the breakdown weak points in high voltage vacuum gaps, a theoretic model was set up for describing the statistical property of multi-break VCB. Dielectric experiments were carried out on a commercial vacuum interrupter arrangements with single break or triple breaks in series under lightning impulse voltage. It shows that the more numbers in series are, the higher the breakdown voltage improvement factor is. The statistical results show that the triple-break vacuum interrupters in series have lower breakdown probability compared with a single-break one. It can be demonstrated in a preliminary study that the experimental results confirm the previous theoretical studies.

Operational Characteristics of a Field-Breakdown Triggered Vacuum Switch

Triggered vacuum switch (TVS) is one of the important switch apparatuses in the fields of high-pulsed power system. Its working lifetime is due to trigger failure of the trigger pin, so the parameters of trigger source become the key of lifetime dilatation. A sample of field-breakdown TVS coated with nothing is fabricated, which has much longer lifetime than the TVS coated with trigger materials, but more trouble in the trigger process. A trigger system and a LC test circuit are designed to find the operational characteristics of the TVS sample. The trigger system generates a negative pulse with peak value of 30 kV/500 A, the system delay and its scatter is controlled in 70~100 mus, and the triggered rate of success reaches 96%. Test results show that the sample has a wide working voltage range of 0.3~40 kV. The delay of its switching-on is stable in hundreds of nanoseconds, which will be reduced with the increase of main gap voltage. The arcing is steady in the conducting process, keeping arc voltage at 20 V approximately. The arc current drops to zero as current zero is approached, leading to a voltage remained in the capacitance.

Delay Characteristics and Controller Design of a Triggered Vacuum Switch

Two types of triggered vacuum switches (TVSs) named TVS-1 and TVS-2 with different configuration in trigger unit were described for investigating the delay characteristics. A design circuit for controlling the TVS is proposed herein. The trigger energy of the controller can be adjusted conveniently. By means of changing the trigger energy, the experimental data show that the delay and jitter times decrease with increasing trigger energy. The delay and jitter times decreases magnificently with the increasing voltage in the main gap. By increasing the main-gap voltage, the triggered probability increases. The TVS-2 has better performance in delay characteristics than TVS-1 because of the improvement in the trigger structure. With a trigger energy of 0.064 J, it is possible to fire both of the TVSs. For the TVS-2 case, the delay time decreases to 2.3 mus, and its jitter time decreases to 1.2 mus when the trigger energy is 1.6 J.

The Voltage Distribution Characteristics of a Hybrid Circuit Breaker During High Current Interruption

Hybrid circuit breaker (HCB) technology based on a vacuum interrupter and a SF6 interrupter in series has become a new research direction because of the low-carbon requirements for high voltage switches. The vacuum interrupter has an excellent ability to deal with the steep rising part of the transient recovery voltage (TRV), while the SF6 interrupter can withstand the peak part of the voltage easily. An HCB can take advantage of the interrupters in the current interruption process. In this study, an HCB model based on the vacuum ion diffusion equations, ion density equation, and modified Cassie-Mayr arc equation is explored. A simulation platform is constructed by using a set of software called the alternative transient program (ATP). An HCB prototype is also designed, and the short circuit current is interrupted by the HCB under different action sequences of contacts. The voltage distribution of the HCB is analyzed through simulations and tests. The results demonstrate that if the vacuum interrupter withstands the initial TRV and interrupts the post-arc current first, then the recovery speed of the dielectric strength of the SF6 interrupter will be fast. The voltage distribution between two interrupters is determined by their post-arc resistance, which happens after current-zero, and subsequently, it is determined by the capacitive impedance after the post-arc current decays to zero.

Dielectric Strength and Statistical Property of Single and Triple-Break Vacuum Interrupters in Series

The maximum possible improvement factor of VCB with double or multiple breaks compared with one-break, which have the same equivalent gap length, is deduced. Simultaneously, from the research on the breakdown weak points in high voltage vacuum gaps, their turn out and distribution, a theoretic model was set up for describing the statistical property of multi-breaks VCBs. This paper describes dielectric experiments on the commercial vacuum interrupter arrangements with single break or triple breaks in series. The experiments were carried out under lightning impulse voltage (LIV). It shows that the more numbers in series are, the higher the breakdown voltage improvement factor is. The statistical results show that the triple-break vacuum interrupters in series have the lower breakdown probability compared with the single-break one. It can be demonstrated in a preliminary study that the experimental results do confirm with the previous theoretical studies

Verification of a Fast Making Switch Based on Triggered Vacuum Switch and Vacuum Circuit Breaker

During synthetic making test a high speed making device is necessary to connect the switching device under test immediately after pre-strike during closing operation under applied voltage. A new kind of fast making device is emphatically expounded in this research, which is composed of triggered vacuum switch (TVS) and a fast vacuum circuit breaker (FVCB) with permanent magnetic actuator. Parallel-connected TVS and FVCB make up the basic optic-controlled module. And basic modules arranging in series can be increase the hold-off (withstand) voltage. When the closing command is triggered, TVS acts in several microseconds and carries the high making current first FVCB acts as the parallel protecting device for TVS, its closing command is sent simultaneously with TVS. Once FVCB closed the making current will shift to this branch, the erosion in TVS can be remarkably decreased. In this paper, a theoretical analysis is made and typical result is simulated with the power system simulation software EMTDC/PSCAD. The simulation result is similar to the experiment one. From the experiment and theoretical result it is known that the new kind of fast making device is feasible for synthetic making test of high voltage circuit breakers

Analysis on dynamic dielectric recovery and statistical property of vacuum circuit-breakers with multi-breaks

Based on the analysis of dynamic dielectric recovery process on vacuum gaps in series, investigations were made on vacuum circuit breakers with double and multi-breaks. From the research on the breakdown weak points in high field vacuum gaps, their turn out and distribution, a theoretic model was set up for describing the statistical property of multi-breaks vacuum circuit-breakers, that can explain the mechanism on the improvement of breaking capacity for multi-breaks units compared with single-break ones which have the same equivalent gap length.

3d electric field calculation of vacuum circuit breakers with multiple breaks using the ANSYS finite element program

The finite element method has proven to be a very useful tool for calculating the electric field in vacuum interrupters. A number of infinite element programs have been developed for this special task. For those who do not have access to one these specialized programs and do not wish to develop their own program, another option is available to use the commercial finite element programs such as the ANSYS finite element program. Recently a new vacuum circuit breaker (VCB) technology with multi-breaks is proposed by means of placing the fiber-controlled vacuum interrupter modules (FCVIMs) in series just like the building blocks. This contribution uses the ANSYS finite element program to calculate the electric field in VCB with double or triple breaks that are composed of FCVIMs. The model of a 12kV vacuum interrupter is set up to calculate the three dimensional (3D) electric field as well as its self-capacitance the three VCB with double or triple breaks are also set up for calculation while the capacitance equivalent circuit is proposed for stimulating the voltage distribution of the breaks. By means of calculation of different collocation of VCB with triple breaks, the optimized electric field calculation is put forward. It shows that it is really an effective method for the design of VCB with multi-breaks using the ANSYS finite element program.

Static electric field distribution of hybrid circuit breaker based on Ansoft

Hybrid circuit breaker (HCB) based on the series of vacuum interrupter and SF6 interrupter uses strong interruption capacity of vacuum and the linear insulation property of SF6 gas to be a high-voltage and high-current breaker. The numerical calculation of 3D electric field is an important way to analyze reasonable and optimization of its structure. The 3D model of the vacuum interrupter and SF6 interrupter are established; the internal electric field distribution of vacuum interrupter and SF6 interrupter are calculated by Ansoft software, and their self-capacitances are solved. Then a 3D computational model of HCB based on models of vacuum interrupter and SF6 interrupter is established, and the distribution characteristics of its electric field are analyzed. The simulation result of electric field distribution of HCB is obtained, and the structure of HCB is optimized designed. It provides a theoretical basis for the structural design of the experimental prototype of HCB.