The early detection of short-circuit fault in the active low-voltage AC system

• Published in: International journal of electrical power & energy systems 2024-01, Vol.155, p.109476, Article 109476
• Main Authors: Zhuang, Shengbin, Miao, Xiren, Lin, Yating, Liu, Qitong
• Format: Article
• Language: English
• Subjects: AC short-circuit fault; Active low-voltage AC system; Short-circuit breaking and current limiting; Short-circuit early detection; Short-circuit time-varying vector
• ISSN: 0142-0615; 1879-3517
• DOI: 10.1016/j.ijepes.2023.109476

•A time-varying vector analysis method for short-circuit fault is proposed, and a vector modulus length calculation model for discrete sampled data is constructed.•Combining the differential information of short current and voltage vector modulus length, a criterion for early detection of short-circuit fault is proposed.•Realizing fault detection within 2.6 ms of photovoltaic grid-connected branch short -circuit and 0.5 ms of normal branch short-circuit.•Combining the proposed short-circuit early detection method with a fast protection mechanism can achieve the short-circuit breaking and current limiting function. The distributed power supply decentralized access to the low-voltage side of the distribution network transforms the existing low-voltage AC system into an active low-voltage AC system. The original low-voltage AC short-circuit detection methods are no longer applicable. In this paper, a short-circuit early detection method suitable for different branch types in the active low-voltage AC system is proposed. Based on the analysis of the transient characteristics of the active low-voltage AC short- circuit, a short-circuit time-varying vector theory and a fast method for solving its modulus length are proposed. Then, we construct a branch state variable containing time-varying vector modulus length difference information of current and voltage. The constructed branch state variable can reflect the characteristics of short-circuit state in real-time, which greatly improving the reliability of fast short-circuit detection. Finally, the early detection of short-circuit fault can be realized by comparing the branch state variable with the set detection threshold. The physical experiment system experiments show that the proposed short-circuit early detection method is effective and reliable. Compared with the existing short-circuit fast detection method, the detection time is reduced by 3–5 ms. Moreover, the short-circuit breaking and current limiting can be achieved by combining with the fast protection mechanism, and the current limiting ratio is as low as 0.33.