Yoshihiko Matsui

Interruption characteristics of double-break vacuum circuit breakers

Since the majority of vacuum circuit breakers in use are of the single-break variety, there have been few studies of double-break vacuum circuit breakers. This report describes our investigations of the interruption characteristics of the double-break vacuum circuit breaker. In this investigation, the post arc current and recovery voltage distribution ratio were measured in order to clarify the relationship between them. The results show that a bias of the voltage distribution ratio occurs when the post arc current value becomes imbalanced. In addition, the measurements of the post arc current for circuit breakers with spiral contacts are very scattered as compared with those with axial magnetic field contacts. Normally, the double-break vacuum circuit breaker consists of two contacts of the same type. However, when two spiral contacts are used, the scattering of post arc current causes a current imbalance. As a result, a bias of the voltage distribution ratio may occur. It appears to be preferable to use double-break vacuum circuit breakers with axial magnetic field contacts.

Development and Technology of High Voltage VCBs; Breaf History and State of Art

Recently, high-voltage VCBs up to 168kV have been developed using newly developed technologies such as electrode materials, insulation, and magnetic field analysis which optimizes VI configurations. In this short review, the paper describes these methods and a number of high-voltage VCBs 72/84kV ceramic VI, 145kV single-break VCB, 72/84kV SF6 gas-free VCB, 120kV tank-type VCB and 168kV tank-type VCB

Withstand Voltage Characteristics of Two Series Vacuum Interrupters

To realize the high-voltage vacuum circuit breaker, we investigated the voltage-distribution ratio after current interruption at the double-break vacuum circuit breaker. We used the spiral CuCr (20%) electrodes and the axial magnetic-field CuCr (50%) electrodes as the experimental electrodes. At the double-break vacuum circuit breaker, where two vacuum interruptions that had the same and different characteristics of the electrode structure and contact materials were connected in series, there was a bias in the voltage-distribution ratio of each vacuum interrupter after current interruption. This seems to be because there was difference in the postarc current that passed through each vacuum interrupter after current interruption.

Insulation recovery characteristics after current interruption by various vacuum interrupter electrodes

Insulation recovery characteristics after current interruption for a vacuum interrupter were investigated. We used spiral and axial magnetic field electrodes for comparison of the electrode structure, while CuBi and CuCr were also used for comparison of the contact material. This paper describes how the axial magnetic field electrode and CuCr (50%) performed best in our experimental data. In addition, we discussed reasons for the variation in characteristics between electrodes.

Vacuum arc phenomena under various axial magnetic field and anode melting

Vacuum arc phenomena under various axial magnetic fields are observed using high speed VTRs. We use disk type contacts and axial magnetic fields generated by external coils.

Discharge Properties in Low Vacuum and Vacuum Monitoring Method for Vacuum Circuit Breakers

One of the causes leading to the low performance of vacuum interrupters (VIs) is a slow leak. If no measures are taken, this phenomenon cannot be detected and the VI will develop serious faults. Therefore, an effective monitoring technique is essential. We experimentally investigated the discharge properties in the low vacuum region of a VI. We measured the signal intensity of the discharge signal caused by the discharge occurring inside a model VI whose degree of vacuum could be varied. Pulse pattern and pulse waveforms were also measured in various pressures. To understand the pattern generating mechanism, we simulated these discharge patterns. Two noise reduction method using timer and frequency filter was examined. Finally, we introduce on-line vacuum-monitoring device with an alarm to warn of the deterioration of the vacuum degree of VIs

A withstand voltage characteristics of two series of a vacuum interrupter

To realize the high voltage vacuum circuit breaker, we investigated the voltage distribution ratio after current interruption at the double-break vacuum circuit breaker. We used the spiral CuCr (20 %) electrodes and the axial magnetic field CuCr (50 %) electrodes as the experimental electrodes. At the double-break vacuum circuit breaker, where two vacuum valves that had same and different characteristics of the electrode structure and contact materials were connected in series, there was a bias in the voltage distribution ratio of each vacuum valve after current interruption. This seems to be because there was difference in the residual current that passed through each vacuum valve after current interruption

Analysis and measurement of axial magnetic field in vacuum interrupter

A magnetic field parallel to the arcing current can improve the breaking capacity of vacuum circuit breakers. In this paper, magnetic field distribution in the radial direction were measured and compared with analysis. A series of short circuit tests were carried out with various condition of contact material and electrode structure. These results were compared with analysis and measurement of magnetic field distribution.

The experimental study of developing a divergent junction construction method bycutting through existing tunnel segments using shield machine

Recently, road tunnel construction using the shield tunneling method has been utilized on infrastructure projects in urban areas. Due to the strict site constraints in urban area, the divergent junctions are to be located underground. Normally, for the construction of an underground diversion junction, large-scale cut and cover methods or the NATM method with ground improvement works shall be adopted. However, these methods involve significant issues relating to safety, cost and the construction period. We then considered that we could construct a divergent junction with minimum section by cutting through the existing tunnel shield using another shield machine. For the development of a new construction method, various experiments have been carried out using specially designed segments for ease of cutting. This paper discusses the possibility of actually adopting this method based on the experiments undertaken.

Insulation recovery characteristics after current interruption for various electrodes of vacuum interrupter

The insulation recovery characteristic after current interruption for vacuum interrupter was investigated. We used spiral electrode and axial magnetic field electrode for comparison of structure, CuBi contact and CuCr contact were used for comparison of contact material. In this paper, we discussed reasons of different characteristics for each electrode.