Unbalanced currents of EHV multi-circuit lines and coordination of zero-sequence overcurrent relayings. (March 2021)

• Record Type: Journal Article
• Authors: Li, Bin; Wang, Wenbo; Wen, Weijie; Yao, Bin; He, Jiawei; Wang, Xingguo
• Is Part Of: International journal of electrical power & energy systems. Volume 126(2021)Part A
• Publication Date: 2021-03
• Subjects: Multi-circuit line -- Electromagnetic coupling -- Current unbalance -- Zero-sequence overcurrent relaying -- Lateral coordination; Electrical engineering -- Periodicals; Electric power systems -- Periodicals; Électrotechnique -- Périodiques; Réseaux électriques (Énergie) -- Périodiques; Electric power systems; Electrical engineering; Periodicals; 621.3
• DOI: 10.1016/j.ijepes.2020.106607
• Languages: English
• ISSNs: 0142-0615

Abstract

Highlights: A lateral coordination scheme for zero-sequence overcurrent relaying is proposed. The mechanism and influence factors of unbalanced current are researched. The impact of ground faults on unbalanced current of adjacent circuit is analyzed. Abstract: With features of large transmission capability and high utilization efficiency of transmission corridor, multi-circuit transmission lines sharing tower or corridor are widely applied in extremely high voltage (EHV) systems. However, mal-operation of zero-sequence overcurrent relaying for multi-circuit transmission lines could occur, and this paper is focused to solve this problem. Overview of typical multi-circuits transmission lines, including phase arrangement and erection form, are introduced first. Then, simulation model of a typical 500 kV triple-circuit transmission line in real project is established in Power Systems Computer Aided Design (PSCAD), and it is verified by real record data provided by power utility in China. By using this simulation model, factors on current unbalances are discussed in detail, and the simulation results have shown that mal-operation of zero-sequence overcurrent relaying is caused by large unbalanced current in normal operation and under faults. Consequently, a lateral coordination scheme for zero-sequence overcurrent relayings among multi-circuit lines is proposed to avoid the mal-operation caused by unbalanced current to the greatest extent without receiving samples from remote end or adjacent circuits, and the reliability of protective relaying is improved significantly.