Contents lists available at ScienceDirect Electric Power Systems Research journal homepage: www.elsevier.com/locate/epsr An intelligent-reduced time method to analyze lightning performance of communication towers and validation using experimental tests F. Aslani a, ⁎ , M. Yahyaabadi b , B. Vahidi c a Dept. of Electrical Engineering, Islamic Azad University of Khomeinishahr, Isfahan, Iran b Dept. of Power Generation Company, Isfahan, Iran c Dept. of Electrical Engineering, Amirkabir University of Technology, Tehran, Iran ARTICLE INFO Keywords: Downward lightning leader Lightning rod Leader progression model Imperialist competitive algorithm ABSTRACT This paper introduces an optimized numerical analysis approach to calculate the number of direct lightning strokes to tall towers. In the conventional numerical method, the lightning leader progression is performed for all possible lightning current values and for all lightning leader tip positions in the space above the tower. In the proposed approach, these time-consuming calculations are reduced by using an intelligent optimization algo- rithm. Here, a telecommunication tower is selected as a case study, and the original imperialist competitive algorithm (ICA) is applied to determine its lightning performance in terms of the number of direct lightning strokes and the computing time. In order to evaluate the potential accuracy and consistency of the proposed method, this algorithm has been applied on a test system including the characteristics of a scaled-down com- munication tower. The simulation results are compared with those of impulse tests conducted on a constructed model in a high voltage laboratory. Finally, the analyses are performed on some effective parameters of lightning performance such as ground slope, breakdown voltage and communication tower height to derive more flexible and comparable results. The simulation results verify the merits of the proposed approach. 1. Introduction Lightning Protection System (LPS) includes equipment by which a lightning discharge can enter or leave the earth without passing through and damaging people, facilities and structures. It controls lightning strike points and prevents damage by providing a safe path for discharging its energy. An external LPS consists of the lightning rod, down conductor and earth termination system. The lightning rod is essentially exposed to direct stroke, the first and foremost task in a protective action [1–5]. In order to analyze a lightning protection system performance, several methods have been proposed and applied [6–9]. The well- known electro-geometrical model (EGM) has been proposed based on the striking distance definition which has the basic concept in the electro-geometric model [10]. The striking distance is defined as the “distance between the target object and the tip of the downward lightning leader at the instant that upward leader is initiated from the object” [11]. The rolling sphere method (RSM) is one of the best pro- cedures which is proposed based on the electro-geometric model (EGM). This method is widely used to design lightning protection sys- tems of complex 3-D geometries. The modified electro-geometrical model (MEGM) and a model that became widely known as the collec- tion volume method (CVM) were also derived from EGM [12,13]. However, in these methods the concept of striking distance is used without having clear referral to the electric field intensification at the top of the equipment and the upward leader propagation is ignored [14,15]. The leader progression model (LPM) was proposed to evaluate lightning performance of tall structures accurately [16–19]. This method models complicated lightning phenomena, mainly based on the propagation of downward lightning leader and the inception and pro- pagation of upward leaders from earthed structures [20–22]. In the conventional numerical method named direct search, all the probable lightning conditions such as the starting points and the current ranges are analyzed, so the processing time of a complete evaluation is un- acceptably high [16–19,23–27]. In this paper, an idea is provided to apply an intelligent optimization algorithm, named imperialist com- petitive algorithm (ICA) in cooperation with the leader progression model to reduce the execution time appropriately besides reasonable accuracy. The idea is based on the finding of the riskiest lightning po- sitions and current ranges which are used to calculate the number of direct lightning strokes to the structure. In order to evaluate the https://doi.org/10.1016/j.epsr.2019.04.017 Received 25 March 2018; Received in revised form 18 February 2019; Accepted 12 April 2019 ⁎ Corresponding author. E-mail addresses: farshadaaslani@gmail.com (F. Aslani), yahyaabadi_aut@yahoo.com (M. Yahyaabadi), vahidi@aut.ac.ir (B. Vahidi). Electric Power Systems Research 173 (2019) 143–152 Available online 29 April 2019 0378-7796/ © 2019 Elsevier B.V. All rights reserved. T