Breakdown Voltage Of Air Gap Research Articles

AC breakdown performance and voltage correction of rod-plane short air gap under rain conditions

According to the operation experience and investigation in China, the insulation performance of transmission line can be reduced due to the effect of strong rain, which is not considered in the external insulation design. Meanwhile, there is no correction reference regarding the breakdown voltage of air gap under rain conditions in IEC standards. Therefore, a series of experimental tests were conducted in the artificial climate chamber and at Xuefeng Mountain Natural Site with the usage of rod-plane air gap to analyze the relationship between ac breakdown voltage and rain precipitation rate, rain conductivity and ambient temperature. It is shown that the breakdown voltage of air gap decreases with an increase of rain precipitation rate and rain conductivity, and increases with an increase of ambient temperature. In addition, according to the test results, the correction formula of ac breakdown voltage of rod-plane air gap under rain condition is proposed and verified in this paper.

Physical mechanisms for reduction of the breakdown voltage in the circuit of a rod lightning protector with an opening microswitch

The effect of air gap breakdown voltage reduction in the circuit with an opening microswitch is substantiated from the physical point of view. This effect can be used to increase the efficiency of lightning protection system with a rod lightning protector. The processes which take place in the electric circuit of a lightning protector with a microswitch during a voltage breakdown are investigated. Openings of the microswitch are shown to lead to resonance overvoltages in the dc circuit and, as a result, efficient reduction in the breakdown voltage in a lightning protector-thundercloud air gap.

Analysis of Space Charge Generating Devices for Lightning Protection: Performance in Slow Varying Fields

This paper starts with a review of anode corona modes with particularly streamer-free glow known as ultra-corona, with the view of exploring its application in lightning protection. Due to the inherent intensification of the ambient electric field atop a tall structure, strict conditions have to be imposed on the streamer-free space charge generation and the stability of that mode of corona when exposed to rapid field variations due to remote lightning. A novel ultra-corona electrode satisfying the above conditions is introduced. High voltage test results on such electrodes are presented including corona current, charge and laboratory air gap breakdown voltage. By applying dimensional analysis, a generalized formula for corona currents from such a device atop a tall structure is presented which includes the effects of the ambient ground field, structure height, ambient electric field at the top of the structure, electrode dimensions, and wind speed.

Impulse breakdown voltages of air gaps: a new approach to atmospheric correction factors applicable to international standards

In the design of high-altitude high-voltage transmission systems and in the optimization of the reliability of power sources in aeronautical environments, it is important to have reliable data concerning the effect of air density and humidity on reducing air insulation performance under local conditions. This is helpful also in the modeling of discharges and lightning in mountainous regions. This paper describes a systematic laboratory investigation of the combined effects of humidity and gas density on the breakdown strength of a 0.2 m rod/plane air gap that is subjected to positive-polarity lightning impulses, using a test chamber to reproduce the conditions commonly found in such regions. The results show that there are appreciable deviations between the measured humidity and air density correction factors and those of the 1973 and 1989 IEC Standards when extended to low air density. The paper proposes the adoption of a radically different correction procedure, based upon the influence of density and humidity on streamer propagation field, and including the effect of the high gradient in the anode region.

Theoretical investigation on barrier effect on point-plane air gap breakdown voltage based on streamers criterion

A model is developed for the computation of the electric field and potential in the presence of a space charge, which is determined after the knowledge of the efficient ionisation factor. The computation is performed in a point–barrier–plane air gap under a positive voltage using finite elements. As a typical electrostatic application, the electric field distribution is computed in the presence of a space charge and a dielectric barrier in the air gap. The proposed model deals with the phase of electronic avalanches.

Effect of humidity and temperature on the DC breakdown of rod-rod and rod-plane gaps

Breakdown voltage of air gaps is strongly affected by atmospheric conditions such as temperature and humidity. Detailed information on the effect of atmospheric conditions on the AC breakdown is available. However, similar data on the DC breakdown characteristics, particularly at high humidities, is scarce. DC data on the effects of humidity and temperature existing in tropical countries is presented. Humidity correction factor curves for rod-rod and rod-plane air gaps are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design of an environmental chamber for high voltage testing in simulated dust and sand storms

Abstract This paper describes the design and the construction of an environmental chamber which enables the breakdown voltage of practically used electrodes to be determined during sand/dust storm conditions. The dust particles used were ⩽ 150 μm in dia. and ranged from a few mgm−3 to a few gm−3 in concentration. Studies were done using switching as well as lightning impulse voltages of up to 1 MV in addition to the high a.c. voltages of up to 200 kV. Using this facility, it was found that the presence of sand/dust particles can greatly affect the breakdown voltages of air gaps. This effect is dependent on the electrode shape, the gap length, and the type of applied voltage. Typical results are shown in this paper.

Electron Attachment Coefficients in Oxygen, Dry Air, Humid Air and Water Vapour

Electron attachment coefficients were measured in oxygen, dry air, air saturated with water vapour at room temperature and in water vapour. An electron filter type apparatus was used. The results have been compared with those of other workers. An approximate evaluation has been made of the influence of humidity on the breakdown voltage of air gaps in a uniform field using the present results and the known ionization coefficient data.