Lightning Surge Propagation on a Single Conductor in Free Space

Abstract

This paper introduces an analysis of lightning surge propagation on a conductor without any returning current path. The conductor can be either a free-space or grounded conductor as long as the reflected surge from the ground has not arrived. Unlike a TEM transmission line, this conductor is characterized with time/position-variant surge impedance as surge current attenuates during its propagation. In this paper a simplified formula was derived. Using the unique parameterattenuation coefficient of current, an iterative method was developed to evaluate actual propagation characteristics. This method was verified numerically, and is much more efficient in calculation and easier in implementation. It is found that the surge impedance is affected by the waveform of an impulse current source, but is independent of the slope of a ramp current source. It increases quickly if the source current has a short rising time or failing time. The simplified formula generates over-estimated results, but the difference decreases with increasing distance to the source. The proposed method can be used to address surge voltage on the tower upon the arrival of a reflected surge from the ground.

A distributed modelling method of the transmission tower and transient response analysis of lightning wave process

“…This point is consistent with the result of the literature [23]. Therefore, the wave impedance of the main body with bracings is equivalent to the wave impedance of bracings in parallel with the wave impedance of the main body without the bracings, as shown in Equation (14). And the specific expression of the wave impedance Z s of the bracings is shown in Equation ( 15):…”

“…Usually, the transmission tower model is an effective tool on both the lightning protection level and the lightning protection design of the transmission line. Thus, in recent years, a large number of researchers have carried out modelling studies on transmission towers [5], which can be roughly divided into the single-wave impedance model [6][7][8][9][10][11][12][13][14], frequency-dependent model [15,16] and multi-wave impedance model [17][18][19][20][21][22][23][24][25]. Among them, the multi-wave impedance models are mainly divided into the composite tower equivalent model [17,18], multilayer transmission tower model (MTTM) [19][20][21][22] and Hara model [23][24][25].…”

Lightning Surge Propagation on a Grounded Vertical Conductor

“…1(c). The surge propagation over such a line is able to be described with the theory of the vertical transmission line proposed in [9]. It is assumed that the conductor is perfectly conductive.…”

“…In these studies, it was assumed that the surge current would not attenuate during its propagation on the tower. However, it was reported in [8] and [9] that a vertical line above the ground would not support the TEM mode of surge propagation. The surge current is attenuated during its propagation even on a lossless line, although the surge voltage remained unchanged.…”

“…This letter presents an extended discussion on the surge propagation on a grounded vertical conductor resulting from the ground reflection, with the characteristic parameters of a vertical line [9]. The conductor is connected to the earth via a ground electrode, and is subject to a lightning stroke at its top end.…”