Rotor ground-fault diagnosis methods for synchronous condensers based on amplitude and phase-angle of voltage
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ORIGINAL ARTICLE
Rotor ground‑fault diagnosis methods for synchronous condensers based on amplitude and phase‑angle of voltage Mengyao Jiang1 · Hongzhong Ma1 · Shuai Zhao1 · Xiaozheng Tang2 · Yidan Liu2 Received: 18 February 2020 / Revised: 8 May 2020 / Accepted: 20 May 2020 © The Korean Institute of Power Electronics 2020
Abstract A single ground fault of the rotor windings in a synchronous condenser can cause serious damage if the fault is not eliminated in time. This paper proposes a new rotor ground-fault diagnosis method for synchronous condensers based on the amplitude of the 150 Hz component of the voltage across a grounding resistance (GR) placed in the neutral of an excitation transformer. It can be seen that the amplitude of the 150 Hz component of the voltage across the GR increases with a decrease of the groundfault resistance (GFR). This method is an improvement of existing algorithms for rotor ground-fault detection that requires less analyzing and can achieve online detection of the severity of a rotor ground fault at any point of the excitation winding. In addition, the influence of different excitation voltages on the algorithm based on phase-angle is analyzed considering actual working characteristics. Moreover, a model is built in the MATLAB/Simulink platform using the real parameters of a TTS-300-2 synchronous condenser to verify the effectiveness of the proposed method. Finally, a dual diagnostic criterion is given according to the results of simulations. The research conclusions can have a great significance on the healthy running of synchronous condensers and they can help to drastically reduce both cost and repair time. Keywords Fault diagnosis · Fault detection · Ground-fault resistance (GFR) · Grounding resistance (GR) · Rotor ground fault · Synchronous condensers
1 Introduction With the large-scale construction of long-distance highvoltage direct current (HVDC) transmission systems, the voltage level and the transmission capacity are constantly being improved, and the demand for the reactive power compensation capacity of converter stations is also increasing [1, 2]. In particular, dynamic reactive power compensation plays a very important role in the voltage stability of HVDC transmission systems [3–5]. Synchronous condensers have the characteristics of high reliability, large capacity and strong dynamic voltage maintenance capability [6]. They can release and absorb reactive power in time through over-excitation and under-excitation in the case of voltage fluctuations [7, 8]. Therefore, to ensure the safe, reliable and * Mengyao Jiang [email protected] 1
College of Energy and Electrical Engineering, Hohai University, Nanjing, China
Maintenance Branch Company of the State Grid Jiangsu Electric Power Co., Ltd., Nanjing, China
2
economical operation of large power grids, large-capacity synchronous condensers have been applied [9]. A synchronous condenser is a kind of synchronous motor under special operation conditions. The excitation system is a crucial part of a synch
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