Locating nearby cloud to ground lightning from measurements of induced voltages on overhead conductor's ends

Abstract

The lightning locating methods are applied to large areas with an array of sensors that is connected to a central computer, using either Time of Arrival techniques or Magnetic Direction Finding techniques, or both. However, a relatively significant error would be present in the assessment of ground flash density for a much smaller area due to the weaknesses of the location accuracy for smaller areas. This thesis introduces an alternative method of locating nearby lightning, which maximized the benefits of the induced voltages at terminated ends of an overhead conductor. It utilises the time differences to peak (�tp) and percentage differences of peak voltages (�vp), between lightning induced voltages (LIV) at both ends. Research work includes field measurements of LIV on ends of a 210 meter overhead conductor and computations of the same. Computation using established electromagnetic mathematical model programmed in C++ in time domain is presented and discussed. Results were validated against other researchers’ work and measurements. A parametric study from the model with varying parameters in inducing voltage at both ends is also presented. Further analysis shows that �tp and �vp of the conductors were not significantly affected by the changes of the return stroke peak current, uniform finite ground conductivity, conductor’s intrinsic inductance and terminating resistances. The mathematical model was also extended to longer conductors (350 meter span ground wires and 5 mile distribution cable) by taking into account of the effects of finite ground conductivity and earth return current. The results thus support the applicability of the proposed method. It is also shown that measurement of the induced voltage at both ends of the overhead conductor, with particular attention to �tp and �vp enables the inference of nearby cloud to ground (CG) lightning location. The modelling work is currently limited to vertically aligned CG lightning, un-attenuated and undistorted lightning return stroke current through the lightning channel with a uniform velocity and interference free.