The influence of the breakdown electric field in the lightning corona sheath on the dynamics of the return stroke

WITHDRAWN - [ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] In the not-so-distant future, a need is foreseen for a high-performance, compact switch that is capable of repetitively switching kilovolts to megavolts and several hundred joules, all while delivering a square pulse with a fast current rise time. Many industrial and military applications currently exist that could take advantage of these operating characteristics, and many more are surely to be developed in the coming years. The proposed approach to realizing the goal of producing a fast rise time, high voltage, high energy, repetitive switch technology is to employ a pressurized, flowing oil dielectric switching medium. Oil pressure and oil flow will be used to increase the rate of dielectric recovery following a high energy discharge, thus enabling a much higher operating repetition frequency; oil pressure will be utilized to control gaseous switching byproducts, and oil flow will be utilized to control solid and gaseous switching byproducts. The well-known increase in breakdown electric field strength with increasing oil pressure will be utilized to reduce the gap separation, thus reducing the inductance of the electrical arc and increasing the rise time of the current pulse produced during breakdown. An experiment was designed and undertaken to evaluate the complete statistical performance of the breakdown electric field of an emerging dielectric liquid, poly-[alpha]olefin, with respect to variations in oil pressure, oil flow rate, peak rate of rise of the voltage, and gap separation.

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Evaluation of Horizontal Electric Field from the Lightning Channel by Electromagnetic Field Equations of Moving Charges

International Journal of Antennas and Propagation ◽

10.1155/2019/4091586 ◽

2019 ◽

Vol 2019 ◽

pp. 1-8

Author(s):

Yunfeng Zhang ◽

Erchun Zhang ◽

Jialiang Gu

Keyword(s):

Electromagnetic Field ◽

Electric Field ◽

Finite Conductivity ◽

Lightning Flash ◽

Horizontal Distance ◽

Field Equations ◽

Long Distance ◽

Return Stroke ◽

Lightning Channel ◽

Soil Conductivity

The horizontal electric field from the lightning return-stroke channel is evaluated by the electromagnetic field equations of moving charges in this paper. When a lightning flash strikes the ground, the charges move upward the lightning channel at the return-stroke speed, thereby producing the electromagnetic fields. According to the electromagnetic field equations of moving charges, the detained charges, uniformly moving charges, and decelerating (or accelerating) charges in each segment of the channel generate electrostatic fields, velocity fields, and radiation fields, respectively. The horizontal component of the sum is the horizontal electric field over the perfectly conducting ground. For the real soil with finite conductivity, the Wait formula is used here for the evaluation of the horizontal electric field over the realistic soil. The proposed method can avoid the oscillation of the fields in the long distance by the FDTD method and the singularity problem of the integral equation by the Sommerfeld integral method. The influences of the return-stroke speed, distance, and soil conductivity on the horizontal electric field are also analyzed by the proposed method. The conclusions can be drawn that the horizontal electric field decreases with the increasing of the return-stroke speed; the negative offset increases with the increasing of horizontal distance and with the decreasing of the soil conductivity, thereby forming the bipolar waveform. These conclusions will be practically valuable for the protection of lightning-induced overvoltage on the transmission lines.

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