Abstract

The Traveling Current Source (TCS) model describes the electrical processes during the lightning return stroke phase. The TCS model assumes that the lightning current is injected at the top of the increasing return stroke channel represented by a transmission line. The electric and magnetic field is calculated based on the spatial and temporal distribution of the lightning current along the return stroke channel. It is shown that the main characteristics of the measured electric and magnetic fields can be reproduced with the TCS model. These are the Initial Peak of the electric and magnetic fields for near intermediate and far distances, the Ramp (up to the maximum) of the near electric field, the Hump of the near magnetic field after the initial peak, and the Zero Crossing of the far distant electric and magnetic fields. The fundamentals of the model are presented, and the model is extended to consider the current reflections occurring at the ground and the upper end of the return stroke channel. To this end, the ground reflection factor ρ and the top reflection factor R are introduced. Due to the increasing return stroke channel, the top reflection factor is a function of the return stroke velocity. The total current is composed of the source current according to the TCS model and the reflected currents. It is shown that the ground reflection causes significant variation in the waveform of the channel-base current and the electric and magnetic fields.

Highlights

  • The threat of lightning can be classified into two separate groups, given by the direct and the indirect effects

  • In the electrical equivalent circuit, both processes can be represented by a current source traveling from the ground in the direction of the thundercloud with the return stroke velocity (v)

  • In the Traveling Current Source (TCS) model, it is not necessary to distinguish between both processes

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Summary

Introduction

The threat of lightning can be classified into two separate groups, given by the direct and the indirect effects. The economic losses caused by the indirect effects are much higher compared to the direct effects [3] This is attributed to the widespread use of electrical and electronic systems and devices in private buildings and industrial. The currents generate electric and magnetic fields, which may be so intense that they couple over-voltages of several kilo-volts into installations inside buildings Examining these over-voltages requires simulation models that consider the return stroke process, including the electric and magnetic fields. To this end, return stroke models were developed which calculate the electric and magnetic field from the spatial and temporal distribution of the lightning current along the return stroke channel [6–10]. The lightning channel is considered with vertical orientation

Physical background on TCS model
Connecting leader period
Discharge process of downward leader channel
Current on the return stroke channel
Source current iQ and channel base current iBase
Lightning current along return stroke channel
Special case of no ground reflections
Electric and magnetic fields
Examples
Influence of ground reflection
Findings
Electric and magnetic field at near, intermediate, and far distance
Full Text
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