Abstract

The object of the research is a circuit that simulates a lightning strike to a tower of 220 kV power transmission line, taking into consideration the reflection of a current wave from 10 nearest towers. Computation of the voltage arising at the top of the stricken tower is necessary further to determine the lightning performance of transmission line by various methods. For Indian conditions, the average number of lightning strikes to this power line per 100 kilometers per year is about 77, which is a fairly high figure. As a rule, for the tasks of lightning protection, the lightning current is approximated by some analytical expression. In most cases, such expressions are various combinations of exponential functions. However, the waveform of real lightning currents on oscillograms differs significantly from the waveform attributed to them and approximated by relatively simple exponential expressions. For a more detailed study of transient processes caused by thunderstorm activity, there is a need to use oscillograms of real lightning currents when modeling. The problem of determining the voltage at the top of the stricken transmission line tower was solved using circuit simulation. To simulate the lightning current, digitized oscillograms of real lightning currents with peak values of –5.256 kA and –133.586 kA were applied. The article shows that the proposed approach gives a more accurate and visual representation of the transient process at the top of the stricken tower than the approximation of the lightning current by simple exponential expressions. Applying a simplified exponential description of the lightning current leads not only to a simplification of the nature of the transient process at the tower top, but also to an underestimation of the results to 8.8%. The selection of the equivalent circuit for the power line towers also affects the result. Representation of towers in the equivalent circuit with lumped inductances leads to slightly higher values compared to application of surge impedances in the circuit. In this case, the smaller the current amplitude, the greater the difference (8.6 % in the domain of low currents and 1.9 % in the domain of high currents). Since this leads to some reserve during the computations of lightning performance, it is recommended to use an equivalent circuit with lumped inductance for a transmission line tower. The conducted research contributes to the development of methods for calculating the lightning performance of power lines and extends the scope of application of circuit simulation programs.

Highlights

  • A lightning strike directly to components of an overhead power line, to the ground or to other objects nearby can lead to insulation flashover and automatic outage of the line

  • Oscillograms of real lightning currents recorded in power systems were digitized and converted into an array of points

  • Voltage arising at the top of a double-circuit tower of a 220 kV power transmission line, stricken by lightning, using the curves of real lightning currents with peak values of –5.256 kA and –133.586 kA was simulated and visualized

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Summary

Introduction

A lightning strike directly to components of an overhead power line, to the ground or to other objects nearby can lead to insulation flashover and automatic outage of the line. In this case, a lightning strike to the power line causes the power supply interruptions to electricity consumers. In order to minimize the number of lightning outages, studying the lightning performance of power transmission lines is recommended. Since the subject of the authors’ research is the power transmission lines of India, for this purpose it is necessary to take into consideration the available data on thunderstorm activity in this country. According to the Indian standard IS 2309:1989 [2], the number of thunderstorm days per year varies from 1 (Azamgarh, Rajgangpur) to 103 (Sibsagar)

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