Kenichi Natsui

Voltage distribution characteristics of series connected SF/sub 6/ gas and vacuum interrupters immediately after a large AC current interruption

Transient voltage distribution characteristics of a hybrid interrupter module have been examined using an experimental model of a hybrid breaker. Tests were conducted to study the voltage distribution between the SF/sub 6/ gas and the vacuum interrupters immediately after a long current interruption. It is found that the voltage distribution is determined by the resistive impedances of respective interrupters during the post arc current flow and by the capacitive impedances of the interrupters contact gaps after the post arc current diminishes. >

A Method and Applications of a Theoretical Calculation for on-load Pressure Rises in Puffer Type Gas Circuit Breakers

An on load pressure rise in a puffer chamber of puffer type gas circuit breakers (GCB) is higher than a no-load pressure rise. A method of calculation of the on-load pressure rise has been developed. The calculation results show good agreement with the on-load pressure rises measured with an experimental puffer type GCB.

Bucket type ion source using a microwave plasma cathode

Abstract For plasma processes one wants a large diameter and long life ion source. A filamentless ion source is desired when using reactive gases. We examined microwave plasma regarding its capability as an electron source and succeeded in extracting an electron current in the ampere range from the plasma. Then we developed a bucket type ion source using a microwave plasma cathode which replaces the conventional filament.

Post arc current of vacuum interrupter after large current interruption

Postarc current characteristics of a vacuum interrupter have been examined under a condition of high-current interruption. A measurement technique was developed in which a shunt for measuring postarc current was set in a synthetic test circuit voltage source. Postarc current was measured after a 20-57 kA current interruption. The magnitude was greatly influenced by the rate of current decline. Residual resistance between electrodes was calculated from the measured values of recovery voltage and postarc current. The recovery of residual resistance was very rapid immediately after current zero and become slow later. >

Interruption ability of a self extinguishing type gas circuit breaker

Interruption ability of a self-extinguishing-type gas circuit breaker has been investigated while varying several structural factors. With a thermal puffer cylinder (0.7 l volume), excellent interruption ability (9.5 to 31.5 kA at 84 kV) was obtained for the condition of a breaker-terminal fault (BTF). In the condition of a short-line fault (SLF), however, its interruptible arcing time width at the same current levels was only 0.2 to 0.3 cycles, where 0.5 cycles was proposed. The critical current, which is the minimum current which the breaker can interrupt, was several kiloamperes. >

Interrupting Characteristics of Puffer and Suction Type SF 6 Gas Interrupter Especially in Thermal Breakdown Region

Interrupting characteristics in thermal region within the range of 30-60kA current levels have been examined with an experimental model breaker under some SF6 gas pressures of 4.5-15 bars. The interrupter tested with the breaker was designed to shorten the arcing time based on the puffer principle with the aid of a suction chamber. Arcing time was shortened with the fastly established gas-flow into the suction chamber in comparison with conventional puffer type interrupters. Interrupting characteristics in short arcing time region were much influenced by interrupter structures, interrupting currents, filling gas pressures and rates of rise of recovery voltage (rrrV). Particularly, in large current region over 50kA, the minimum arcing time was sensitively affected by moving side interrupter structures. Using a newly developed interrupter characterized by a follower type insulating nozzle, it has demonstrated a minimum arcing time of 0.37 cycles for the 63kA 90% short line fault (SLF) condition for two breaks per pole under an SF6 gas pressure of 10 bars, and also has demonstrated 0.33 cycles for the 50kA 90% SLF condition under a pressure of 6 bars.