Impulse Voltage Waveforms Research Articles

Reproducibility of Steep and Short-Tailed Lightning Impulse Voltage Waveform by Detailed Equivalent Circuit

The overvoltage waveforms on a medium-voltage (MV) line generated by lightning have a steep front and a short tail due to behavior of protection devices. To discuss the occurrence of sparkover on a MV line, it is necessary to estimate the insulation characteristics of the distribution instruments by using such waveforms. Therefore, it is of practical importance to develop an equivalent circuit of an impulse generator, applicable to the case of generation of such waveforms. In this letter, the authors verify the reproducibility of a steep and short-tailed lightning impulse voltage waveform by the detailed equivalent circuit.

各種インパルス波形を用いた場合の配電線と樹木の放電特性に関する基礎検討

各種インパルス波形を用いた場合の配電線と樹木の放電特性に関する基礎検討

Transient Impulse Breakdowns of SF6 Gas in Inhomogeneous Electric Fields

In this paper, we describe the dielectrics and predischarge developments of gaseous SF6 stressed by nonoscillating and oscillating impulse voltages in inhomogeneous fields caused by a metallic protrusion. The breakdown voltage-pressure curves and the formative time lags to breakdown were measured in the gas-pressure range extending from 0.05 to 0.3 MPa. The predischarge processes were simultaneously investigated through measurements of the current induced by moving space charges and photomultiplier records. The predischarge propagates into the gap with a stepwise leader, and the basic physical mechanisms leading to electrical breakdown are the same for nonoscillating and oscillating impulse voltage waveforms. While for the other, the quickly changing macroscopic electric field due to space charges in the gap affects the leader propagation under the oscillating impulse voltage waveform. In the case of negative polarity, the predischarge growth processes at the increasing and decreasing parts of the oscillating wave tail are not very similar. It is inferred that the breakdown at the decreasing part of the oscillating impulse voltage originates from ion depletion due to recombination.

雷サージ解析のための新フラッシオーバモデルの開発

This paper describes a new flashover model for lightning surge analysis. It is shown, at first, that starting conditions of leader propagation and leader propagation processes with the short tail light-ning impulse voltage waveform, which appears across the insulator strings on the transmission line by a lightning stroke, are clarified by experimental results. The new flashover model based on the experimental results is proposed in this paper. The proposed model consists of simple two equations, that give expression to the leader propagation processes, and can be realized very easily on the EMTP and other transient analysis programs. A comparison of results calculated by the proposed model with the experimental results shows good agreements.

Review of research on nonstandard lightning voltage waves

Although the impulse insulation level of a power apparatus is specified under the standard 1.2/spl times/50-/spl mu/s voltage wave, the apparatus seldom encounters such a voltage wave in the field. A wealth of knowledge exists on the behavior of air gaps under nonstandard lightning impulse voltages. The objective of the Task Force was to compile a bibliography on the nonstandard lightning impulse voltages and review the present state of research. This paper reviews the present status of research including the behaviour of air gaps under transient voltages, and the generation and measurement of fast-front impulse voltage waveforms. >

Effects of humidity on corona inception in a diverging electric field

The distribution of time lags to corona inception is examined theoretically and experimentally for the case where a double-exponential positive impulse voltage waveform is applied, at a fixed repetition rate, to a rod/plane gap. The influence of atmospheric humidity, temperature and pressure on the conditions for corona formation are discussed. Experimentally, the spread of the time-lag distribution is studied primarily as a function of humidity. The results are related to the variation, with humidity, of the negative-ion density prior to each impulse. Models for the conditions for detachment of electrons from negative ions, and for corona formation, which are derived from experiments using small air gaps, have been shown to agree with the results obtained in large air gaps.