Hisatoshi Ikeda

Parallel Interruption of Heavy Direct Current by Vacuum Circuit Breakers

A newly developed d.c. circuit breaker successfully interrupts the current up to 130 kA d.c. under 44 kV d.c. recovery voltage. The breaker also can carry out the respective 4000 times operations of the above breaking duty every ten minutes without any trouble. The essential breaking mechanism is composed of two series and four parallel construction of vacuum valves with current commutation capacitor.

Development of novel hybrid puffer interrupting chamber for SF/sub 6/ gas circuit breaker utilizing self-pressure-rise phenomena by arc

A novel puffer interrupting chamber is developed which is designed to evaluate pressure rise by guiding the thermal energy of the arc effectively into a puffer cylinder. This interrupting chamber has high blasting pressure, suitable for interrupting from low up to high current levels, providing interrupting performance considerably better than that of conventional interrupting puffer chambers. Particularly, its performance during short arcing is excellent, providing reduced minimum arcing time. For an 84 kV, 31.5 kA interrupting chamber, pressure calculations on an arc model and interruption tests were conducted to compare the interrupting performance of the new chamber with that of a conventional double-flow puffer interrupting chamber. >

Computer simulation of phenomena associated with hot gas in puffer-type gas circuit breaker

To analyze hot-gas flow in puffer-type gas circuit breakers (GCBs), a program was developed by adding functions for dealing with opening process, gas compression, and arcing to a program for the analysis of axially symmetric compressive fluids. The accuracy of the program is demonstrated by comparing the results of computation by this program with the results of two different tests: the observation of hot-gas backflows using the Schlieren method and the measurement of breakdown voltage drops resulting from hot gas generated by current interruptions. The results of both tests show trends similar to calculated results obtained by simulating the tests, proving that this program is applicable to interruption phenomena associated with hot gas to a certain extent. The program is applied to the calculation of pressure rise phenomena in a puffer chamber caused by hot-gas backflows and dielectric strength to ground in a tank-type GCB. The program is expected to be useful as a means of estimating test results. >

The characteristics of vacuum arcs with magnetic fields parallel to its columns

Abstract Vacuum arcs subjected to an axial magnetic field have many peculiar characteristics. These characteristics are favorably applied to vacuum interrupters. Nowadays, they are widely used around the world [1]. However, their characteristics are not fully understood. In order to quantitatively understand such phenomena, we measured the plasma parameters by the spectroscopic method. Assuming that the local thermal equilibrium is obtained in the vacuum arcs, the following data were found. Electron temperature and electron density are around 7000–9000 K and about 10 16 –10 17 cm -3 , respectively, under the condition that the magnetic field parallel to its column is between 0.02 and 0.2 T and the arc current is 5 and 10 kA rms. These values depend upon the arc column shapes.

On the hot gas exhaustion in the exhaust chamber of a gas circuit breaker after short-circuit current interruption

The hot gas inside the exhaust chamber of a gas circuit breaker (GCB) is investigated after short-circuit current interruption. It is found that the exhausted hot gas generates a compression pressure wave. When the interrupting arc energy is low, the velocity of the hot gas is low and the hot gas is delayed relative to the pressure wave at the exit of the exhaust chamber. The interaction between the pressure wave and the hot gas is weak and the hot gas is found concentrated near the centre of the exhaust chamber. When the interrupting arc energy becomes high, the velocity of the hot gas becomes high and it is found that the hot gas area overlaps the area of increased pressure. The interaction between the pressure wave and the hot gas is strong, the hot gas density distribution becomes flat due to the pressure increase and the pressure increase is enhanced by the hot gas flow. The pressure increase clogs the exit of the exhaust chamber and the gas near the upstream area loses its dielectric strength.

Highly sensitive Shack–Hartmann sensor for two-dimensional electron density imaging over extinguishing arc discharges

Highly sensitive Shack–Hartmann-type laser wavefront sensors incorporating meniscus microlens arrays with a long focal length of 238 or 467 mm were developed for imaging two-dimensional electron density distributions over extinguishing atmospheric arc discharges. The use of the novel microlens arrays also had the advantage of realizing the spatial synchronization of the measuring system. The highly sensitive Shack–Hartmann sensors were successfully used for the single-shot imaging of two-dimensional electron density distributions over the extinguishing arc discharges with currents of several amperes and were proven to have improved the measurement sensitivity by two orders of magnitude from 1023 to 1021 m−3. Spatiotemporal evolution of the electron density images showed that just before arc extinction the electron densities at outer radial positions with respect to the interelectrode gap were higher than those on the geometrical axis defined by the electrodes.

Analyses of Axial Energy Distribution in Decaying Arc of SF6 Gas Circuit Breaker

Adopting a transient arc analyzing program, the authors analyzed the axial distribution of arc characteristics near the current-zero point, proving that while almost all portions of total arc resistance were shouldered in downstream arc, zero conductivity was achieved in the nozzle throat arc. It was also proved that in the presence of transient recovery voltage (TRV) with initial fluctuations, such as initial TRV (ITRV), an interruption was accomplished by combined effects of the downstream and the nozzle throat arc.

Investigation of interruption performance of newly developed 300 kV 3-phase-in-one-tank-type GCB and its application to a reduced size GIS

With the objective of diminishing the distance between bays of SF/sub 6/ gas insulated switchgear (GIS), a 300 kV three-phase-in-one-tank-type gas circuit breaker (GCB) has been developed. The size of the interrupting chamber has been reduced to decrease the diameter of the GCB tank. Hot gas flow has been optimized analytically and the deterioration of insulation performance caused by the hot gas between the poles has been investigated. A more compact GIS with fewer parts and easier to install results from the study. >

Numerical Study of Delayed-Zero-Current Interruption Phenomena Using Transient Analysis Model for an ARC in SF 6 Flow

Arcs in gas circuit breakers have been regarded as resistances when a zero-miss current interruption phenomenon has been simulated by a computer. However, the model involved is unable to simulate the thermal inertia effect of the arc. This fact is proved to result in a deteriorated simulation accuracy in the vicinity of the current zero point through conducting a short-circuit test. To simulate thermal inertia of the arc, an arc model based on the conservation laws of mass, momentum, and energy is developed. By applying this model to circuit analysis, zero-miss current interruption phenomena are shown to be simulated more precisely up to the current zero point than the conventional method.

Developing of 550 kV 1-break GCB. I. Investigation of interrupting chamber performance

The interrupting chamber for a 550 kV 1-break gas blast circuit breaker (GCB) is developed. To cope with voltages and interrupting capacities of nearly double per break compared with 2-break GCBs, the shape of the interrupting chamber was optimized, and an interrupting chamber scheme using arc energy is employed. Small-current interrupting performance is improved by selecting a nozzle shape with pressure fluctuations due to a supersonic flow at the downstream side of the nozzle and by taking into account the dielectric recovery characteristics. By using an interrupting chamber scheme utilizing arc energy, the opening speed is increased by minimizing the reaction due to pressure rises in the puffer chamber in small-current interruptions, or the pressure is sharply raised due to the effect of arc energy in large-current interruptions. The nozzle shape is also optimized for a large-current interruption by improving the efficiency of treating hot gas. >