Electrical Power and Energy Systems 125 (2021) 106549 Available online 2 October 2020 0142-0615/© 2020 Elsevier Ltd. All rights reserved. The failure arc paths of the novel device combining an arrester and an insulator under different pollution levels Xinhan Qiao a, b , Zhijin Zhang a, * , Raji Sundararajan b , Xingliang Jiang a , Jianping Hu c , Zhen Fang c a Chongqing University, No. 174, Shazheng Street, Shapingba District, Chongqing 400044, China b Purdue University, 401 N. Grant St., West Lafayette, IN 47907, USA c State Key Laboratory of Disaster Prevention and Reduction for Power Grid Transmission and Distribution Equipment State Grid, Disaster Prevention and Reduction Center, State Grid Hunan Electric Power Company Ltd., Changsha 401205, China A R T I C L E INFO Keywords: Failure arc path Impulse voltage waveform Arresters Lightning protection Pollution levels ABSTRACT Lightning strokes on transmission lines could trigger insulation failure if no protective measures are taken. Typically, a lightning arrester is used for this purpose. In order to combine the insulator and the lightning arrester as a single entity, a novel lightning protection composite insulator, combining an arrester and an insulator was developed for 10 kV distribution lines. Studied in this paper are the various arc paths of the novel insulator. The arc path tests under both AC and impulse voltage were conducted. The fndings indicate that low, medium, high, very high, and extremely heavy pollutions caused different types of arcings under AC voltage. In addition, arc paths were affected by both the pollution level and the magnitude of impulse voltage. Based on the arc paths recorded by a high-speed camera, the fashover modes can be divided into three categories (fashover of the air gap, fashover of silicone rubber sheds in insulation section, and fashover of the whole insulator). More spe- cifcally, we defned and analyzed 14 types of arc paths in detail, and the critical pollution level (0.1 mg/cm 2 ) of normal operation were obtained. Further, the statistical probability of each arc under impulse voltage was calculated. Due to the complexity of the arc paths under the switching impulse voltage, a 90% probability distribution fgure of arc paths with different U s (switching impulse voltage) and ESDD (equivalent salt deposit density) was presented according to the test results. At last, we discuss the impulse voltage waveform corre- sponding to the typical arc path and describe the research prospect. The research results in this paper present the failure modes of the novel lightning protection insulator, and the results can be used for designing insulators for various pollution levels. 1. Introduction Lightning strokes on transmission lines could trigger insulation failure if protective measures are not taken [1–3], causing power failure, resulting in economic losses [4,5]. The lightning strokes have gradually become the most leading cause of power grid trip-out on high voltage lines. Taking the operation data of 500 kV transmission lines of South China Power Grid in a specifc year as an example, 62 grid trip-outs occurred, 54 of which were caused by lightning strikes, accounting for 87.1% [6]. For 10 kV distribution networks, taking the operation data in Qingcheng District Guangzhou Province as an example, 310 grid trip- outs occurred in 2016, 164 of which were caused by lightning strikes, accounting for 52.9% [7]. To prevent lightning fashover accidents, overhead grounding lines and transmission-line arresters are used in service [8–12]. Some scholars focus on the development of new arresters and their applications [13,14]. Two types of transmission-line arresters are mainly adopted [15]: air-gapped and gapless arresters. Gapless arresters are generally installed in the substation or on the frst foundation tower near the substation. It is used to protect the electrical equipment of substation from the damage of lightning. During the operation of the gapless arrester, the voltage is applied to the arrester, which accelerates the aging of the arrester. Besides, the performance of the arrester should be tested before the thunderstorm season every year, and it involves lots of repetition work and costs much time and labor. Compared with gapless arrester, air-gapped arresters is easier to maintain. However, when * Corresponding author. E-mail address: zhangzhijing@cqu.edu.cn (Z. Zhang). Contents lists available at ScienceDirect International Journal of Electrical Power and Energy Systems journal homepage: www.elsevier.com/locate/ijepes https://doi.org/10.1016/j.ijepes.2020.106549 Received 11 June 2020; Received in revised form 12 August 2020; Accepted 20 September 2020