Please cite this article in press as: Z. Yu, et al., Calculation of surface electric field on UHV transmission lines under lightning stroke, Electr. Power Syst. Res. (2012), http://dx.doi.org/10.1016/j.epsr.2012.05.015 ARTICLE IN PRESS G Model EPSR-3527; No. of Pages 7 Electric Power Systems Research xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Electric Power Systems Research jou rn al h om epage: www.elsevier.com/locate/epsr Calculation of surface electric field on UHV transmission lines under lightning stroke Zhanqing Yu a,∗ , Qian Li a , Rong Zeng a , Jinliang He a,1 , Yong Zhang b , Zhizhao Li a , Chijie Zhuang a , Yongli Liao c a State Key Lab of Control and Simulation of Power Systems and Generation Equipments, Department of Electrical Engineering, Tsinghua University, Beijing 100084, China b Department of Mathematical Sciences, Tsinghua University, Beijing 100084, China c Electric Power Research Institute, China Southern Power Grid, Guangzhou, China a r t i c l e i n f o Article history: Available online xxx Keywords: Surface electric field UHV Transmission lines Leader progression model Charge simulation method a b s t r a c t Lightning is the major cause of interruptions in power transmission lines. Ultra-high voltage (UHV) AC transmission line has been put into operation in China. Due to the large tower height up to 90 m and the high operation voltage up to 1000 kV, the shielding failure probability increase obviously. Nowadays the leader progression model is an advanced method to evaluate the shielding failure probability of transmission lines. The surface electric field is the key issue for lightning failure analyzing, because the upward leader inception mainly depends on the surface electric field. In this paper, the lightning leader model is introduced. A charge simulation method based piecewise linear function is adopted to analyze the surface electric field on phase conductors and ground wires. The influence factors, such as operation voltage, lightning peak current, lightning down leader position, protection angle, on surface electric field were analyzed. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The shielding failure is the major cause of interruptions in power transmission systems. The rational design to improve the shield- ing effect of transmission line against lightning is one of the key problems of transmission line design. Now 1000-kV ac ultra-high voltage transmission line has been put into operation in China. The transmission tower reaches about 70–90 m high, and 30–60 m wide, thus, the lightning attraction area of 1000-kV transmission line is much wider. Meanwhile, with the increment of opera- tion voltage of the long-distance transmission lines, proportion of shielding failure rises [1]. Due to the high insulation level of the 1000-kV transmission line, the threaten of direct lightning stroke is very small, but the probability of shielding failure increases obvi- ously due to very high towers. According to the statistical results of power system failure clas- sification, above 50% of power system failures were caused by lightning in Japan [1]; about 40–70% of the total tripping numbers of transmission lines in high voltage power system were caused by lightning in China [2]. According to the operation experiences ∗ Corresponding author. Tel.: +86 13611013023/10 62795423; fax: +86 10 62795423. E-mail address: yzq@tsinghua.edu.cn (Z. Yu). 1 Fellow, IEEE. of 1150-kV ac transmission lines in Russia, the lightning trip-out rate was 84.4%, its length is 493.2 km. The first double circuit UHV transmission line which has a length of approximate 490 km was completed in Japan in 1999, and it has being operated in 500 kV [3]. Field observation of the characteristics of direct lightning strokes to the double circuit UHV transmission line was carried out by The TEPCO during 1998–2004 [4]. The Electro-geometry Method (EGM) [5–7] treats the light- ning strike process as a geometry drawing, the effect of conductor dimension cannot be considered, so for 1000-kV transmission line with the tower height taller than 70 m, this effect would have strong influence on the upward leaders from tower, shield wires and phase conductors, certainly on the downward lightning leader, too. With the progress of the long air gap discharge research, leader progress model (LPM) has become the new approach to analyze the shielding failure of transmission line. Many researchers had studied LPM [8–11] and proposed different models. LPM considers the variation of space electric field and its effect on the lightning developing progress during the lightning striking the conductor. It is much more approaching to the physics of lightning, is able to overcome the difficulty of EGM. The LPM proposed a description of the whole developing process of descending leader to upward leader. An assessment model is pro- posed here in the conception of LPM, based on the lightning survey data and the physics of leader discharge. The LPM is an advanced 0378-7796/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.epsr.2012.05.015