Analysis of Electromagnetic Transient Program (EMTP) of Lightning Surge of a Vertical Conductor and its Invasion to a Control Building

Abstract

The lightning surge characteristics of transmission line components as well as the statistical data of lightning such as the ground flash density and the stroke peak current distributions are very essential for analyzing the lightning performance of overhead power transmission lines and substations. Lightning over-voltages must be taken into account when designing a vertical tower model and the insulation system of a cable. In the world, specially in Japan various studied, therefore, have been done to measure the characteristics of the line components and to develop their equivalent circuit models for the Electromagnetic Transient Program (EMTP) simulations. EMTP has been widely used in Japan to analyze switching and lightning over-voltages to design power stations and substations from the viewpoint of insulation coordination. The Japanese standard of' high voltage testing, JEC-0102-1994, and the insulation design and the coordination of an 1 l()()-kV line of lokyo electric power company were mostly based on EMTP simulations. 'I'his research demonstrates the electromagnetic behaviour of transient i-espouse of lightning surge strike on single vertical conductor, base-broadened tower, actual tower and the control building. Vertical conductor surge responses are analysed using EMTP. The accuracy of this method is shown to be satisfactory with the simulation result based on the numerical electroiiiagnctic code (NEC-2) that were carried out on vertical tower as reduced scale model. Surge iiiipcdancc is calculated by both the vertical and horizontal stroke analyses method. In addition, line constant program of different frecuency of EMTP is also verified in the work for evaluating (lie voltage and current due o lightning surge. lhcrc have been considerations sonic methods to evaluate the transient characteristics of a tower, such as : (i) theoretical studies, (ii) simulation of reduced scale models and (iii) simulation of lill-sized tower. The simulation analysis of surge response are carried out in the several arrangements of the current lead wire: (i) vertical and at the top of vertical conductor. (ii) vertical and a little far from the top of vertical conductor, and (iii) horizontal and far from the top of vertical conductor.In all the cases, the voltage measuring wire is also placed perpendicular to the current lead wire. Each of the arrangement of the current lead wire affects the measured surge impedance of' the vertical conductor and that has been explained in this research in detail. If a travelling wave propagates along the vertical conductor at the velocity of light, the reflected wave from the ground should return to the top of the vertical conductor just after the round-tril) time of the travelling wave in the vertical conductor.In all the cases, the voltage measuring wire is also placed perpendicular to the current lead wire. Each of the arrangement of the current lead wire affects the measured surge impedance of' the vertical conductor and that has been explained in this research in detail. If a travelling wave propagates along the vertical conductor at the velocity of light, the reflected wave from the ground should return to the top of the vertical conductor just after the round-tril) time of the travelling wave in the vertical conductor.