Proposal of a New Sensitive Ground Overcurrent Protection for High-Impedance Faults
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Proposal of a New Sensitive Ground Overcurrent Protection for High-Impedance Faults Eduardo Cesar Senger · Giovanni Manassero Junior · Eduardo Lorenzetti Pellini
Received: 24 October 2012 / Revised: 18 March 2013 / Accepted: 24 May 2013 © Brazilian Society for Automatics–SBA 2013
Abstract This paper presents the development of a sensitive ground overcurrent protection algorithm. The proposed algorithm is able to detect high-impedance faults produced by downed conductors in solidly grounded primary distribution networks. It presents a higher level of accuracy when compared to conventional overcurrent protection functions. The algorithm is based only on current measurements and uses additional conditions to generate the trip signal, in order to prevent false tripping due to its high level of sensitivity. This paper presents a detailed description of the proposed algorithm, the hardware prototype developed during the research and its performance in laboratory tests. Keywords High-impedance · Power system protection · Distribution networks 1 Introduction Distribution systems are usually radial or interconnected networks (e.g., spot networks). Radial distribution networks, which consist of medium-voltage power lines that leave the substations and have no connection to any other power supply, are frequently more common due to economic reasons. Protection systems used to protect these distribution networks are based almost exclusively on overcurrent protection functions such as ANSI 50/50N and 51/51N. Therefore, they E. C. Senger · G. Manassero Junior (B) · E. L. Pellini Av. Prof. Luciano Gualberto, 158, travessa 3, sala A2-14, CEP 05508-900 São Paulo, SP, Brazil e-mail: [email protected] E. C. Senger e-mail: [email protected] E. L. Pellini e-mail: [email protected]
are much less complex than the systems used in high-voltage and extra-high-voltage transmission networks. Despite the simplicity of such protection systems, highimpedance faults still pose as an unsolved protection problem. The reason lies with the magnitude of the fault currents, which are usually smaller than typical load currents and may not be detected by conventional overcurrent protection devices. The most recurrent and dangerous high-impedance faults occur when energized primary conductors break and fall to the ground. This situation is particularly dangerous due to the risks of electrocution and fire hazards (Kawady et al. 2009). Several methodologies for high-impedance fault detection in distribution networks have been proposed (Senger et al. 2000; Yang et al. 2004; Sedighi et al. 2005; Bretas et al. 2006; Michalik et al. 2006; Haghifam et al. 2006; Ramezani et al. 2007; Hou and Fischer 2007; Cui et al. 2008; Samantaray et al. 2008, 2009; Vico et al. 2010; Siadatan et al. 2010; Milioudis et al. 2011; Yong et al. 2011; Torres and Ruiz 2011; Abdel Aziz et al. 2011; Sarlak and Shahrtash 2011). High-impedance fault detection can be accomplished with the use of power frequency signals (voltage and current signals) (Senger et al. 2000; Hou and Fischer 2007
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