Current differential protection of double-circuit transmission lines in modal domain
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ORIGINAL PAPER
Current differential protection of double-circuit transmission lines in modal domain Snehal Unde1
· Sanjay Dambhare1
Received: 20 December 2018 / Accepted: 8 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this paper, we present a new approach to protection of double-circuit transmission lines using modal transformation. The current differential principle is applied in the modal domain, and the relay characteristics are plotted in the alpha plane for numerical differential protection applications. Synchronized voltages and currents from both the ends are transformed to modal values. The transmission lines are modeled as equivalent π model in modal domain, and line charging current is compensated. Electromagnetic transient program EMTP-ATP is used to simulate the double-circuit transmission systems, and the algorithm is implemented in MATLAB. The extensive case studies demonstrate the utility and the superiority of the proposed current differential scheme. Keywords Current differential protection · Double-circuit transmission lines · Mutual coupling · Modal transformation
1 Introduction Double-circuit transmission lines are extensively used to enhance the reliability of the transmission system. Due to close proximity of these lines, magnetic mutual induction occurs prominently in zero sequence. Positive and negative sequence mutual coupling is less than 5% and hence neglected in most studies. The mutual coupling causes protection challenges with ground directional overcurrent protection and ground distance element [1,2]. Use of current differential principle has always been of interest to transmission line protection. The literature survey shows that the technological advancements like fiber optic communication with negligible latency, synchronized measurements using global positioning system (GPS), increased processing power have given rebirth to current differential protection [3,4]. The state-of-the-art high-speed communication systems used for protection purpose are discussed in [5,6]. The differential current calculated using time stamped phasors is immune to asymmetry and channel delays. Several authors have proposed new approaches to differential protection of high voltage transmission lines. A
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Snehal Unde [email protected] Electrical Engineering Department, College of Engineering, Pune, India
method which extracts the active current component using abc static to pq rotating transformation is proposed in [7] with the advantage of high sensitivity and strong capacity of enduring transition resistance. A new concept of differential impedance which is independent of line capacitive charging current and source strength is proposed in [8]. Differential protection based on an alternative alpha plane of incremental complex power with restraint characteristics as its left half plane is proposed in [9]. The literature survey shows that several researchers have taken the advantages of the new technologies in the recent past and used to conceive more secu
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