Abstract— Lightning performance of transmission lines is an important factor for the electric utility companies. Now a day, this matter is getting more priority with the increasing requirement for power quality. In order to understand the lighting surge phenomena clearly, the author used a reduced scale model of tower for the analysis. But in real life, the actual tower is subjected to the lightning. It is then necessary to analyze the characteristics of actual tower when subjected to lighting as in case of reduced scale model tower. So, the authors also simulate an actual tower to obtain the surge characteristics phenomena. In this case, the three-phase conductors and the earth wire have been considered for the analysis. The apparent characteristics of a tower may be influenced by the presence of an earth wire. However, this issue has been paid a little attention in the modeling of a tower for the well-known Numerical Electromagnetic Code (NEC-2) simulations. In this paper, firstly, a reduced scale model is analyzed in different aspect, and then the surge characteristics of an earth-wired tower as well as phase conductors of the tower struck by lightning are studied with the help of NEC-2 in case of direct and indirect stroke. Index Terms— Earth wire, Phase conductors, Surge impedance, Transmission tower, NEC-2 I. INTRODUCTION ransmission line faults caused by lightning strikes give serious damages, such as a massive blackout and instant voltage drop, on electric power systems. Therefore, the rational lightning protection measures should be adopted for ensuring a stable electric power system. Analysis of lightning surges is important for power systems, since lightning strokes on transmission towers, shield wires and phase conductors may cause insulation flashover which may lead interruption of continuous power transmission. When a lightning strike occurs on a tower or on a shield wire near potential on the phase conductor, which is the sum of nominal system operating voltage and induced potential due to lightning. For calculation of the potential across the insulator strings, the surges both on the tower and induced voltages on the phase conductors need to be determined. Manuscript received April 20, 2014; revised Dec 2, 2014. This work was supported in part by Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh & Universiti Sultan Zainal Abidin (UniSZA), Kuala Terengganu, Terengganu, Malaysia. M. S. Yusuf is with the Faculty of EEE, Khulna University of Engineering & Technology, Bangladesh. M. Ahmad is with the Faculty of EEE, Khulna University of Engineering & Technology, Bangladesh. M. A. Rashid is with the Faculty of Design Arts and Engineering Technology, Universiti Sultan Zainal Abidin (UniSZA), Terengganu, Malaysia (Corresponding author, phone: +609-668-8428, fax: +609-668- 8452, e-mail: marashid@unisza.edu.my). M. O. Goni is with the Faculty of ECE, Khulna University of Engineering & Technology, Bangladesh. Several studies on surge analysis of the transmission lines have been carried out to evaluate the effect of the lightning protection measures and to estimate the lightning outrage rates [1]-[3] There are many works that have been devoted to the analysis of lightning surges on transmission towers. Experimental studies on this subject have usually been carried out in Japan [4] and measured results have become an important base for computer simulations. In the experimental work done by Kawai surge response of transmission tower has been measured [1]. Later Ishii performed experiments on a full scale tower with phase conductors and ground wires [2, 3] and as a result of these experiments a multistory tower model has been proposed for multiconductor analysis in EMTP. Series of experiments later have been continued on a different tower configuration [4] to generalize the results obtained in previous works. On the other hand, in the area of numerical developments, Almeida and Correia De Barros [5] used finite element method for the EMTP simulation. Later Ishii and Baba [6] analyzed a large scale UHV transmission tower using moment method by solving electric field equations directly, and in their study the effect of slant elements, horizontal elements and crossarm has been investigated. Using the same method, they also investigated lightning surge characteristics of a transmission line comprising a tower, a shield wire and phase conductors [7]. Next, tower body and crossarms are modeled in details using short lines sections [8]. Mozumi et al. analyzed archorn voltages of a simulated 500 kV twin-circuit line [9]. In this paper, lightning surges on a transmission tower are analyzed using the numerical solution of the electric field integral equations used in NEC- 2 are first obtained. The measuring method of tower surge impedance are briefly explained and then this effects of the measuring methods and the arrangements of the measuring wires on the evaluated tower surge impedance are studied by the NEC-2. Lightning surge phenomena are analysis are given in [10]. Overhead transmission line modeling for over voltage calculation is explained by Juan A. Martínez et al. in [11]. Mohd Z. A. Ab Kadir et al. analyzed back flashover, shielding failure and determination of arrestor in details energy [12]. P. Yutthagowith et al. proposes the application of a partial element equivalent circuit method to lightning surge analyses in [13]. In [14], Y. Du, X. Wang and M. Chen, explained the transient surge response of a vertical conductor over the ground. In analyzing the lightning performance of overhead power transmission lines and substations, the lighting surge characterstics of transmission line components as well as the statistical data of lightning such as the ground flash density and the strock peak current distributions are essensial. Among the transmission line components, tower surge characterstics including the tower footing impedence charactersticsin the linear region are Analysis of Lightning Surge Characteristics on Transmission Tower M. S. Yusuf, M. Ahmad, M. A. Rashid, Member IAENG, and M. O. Goni T Engineering Letters, 23:1, EL_23_1_05 (Advance online publication: 17 February 2015) ______________________________________________________________________________________