Electric Power Systems Research 154 (2018) 266–275 Contents lists available at ScienceDirect Electric Power Systems Research j o ur nal ho me page: www.elsevier.com/lo cate/epsr New fault location scheme for three-terminal untransposed parallel transmission lines Ahmed Saber ∗ , Ahmed Emam, Hany Elghazaly ElectricPowerandMachineDepartment,CairoUniversity,Cairo,EgyptEgypt a r t i c l e i n f o Article history: Received 15 March 2017 Received in revised form 13 July 2017 Accepted 30 August 2017 Keywords: Cross-country faults Evolving faults Fault location Phasor Measurement Unit (PMU) a b s t r a c t This paper proposes a new fault location scheme in the phase-domain for three-terminal untransposed double-circuit transmission lines utilizing synchronized voltage and current measurements obtained by GPS technique. The proposed scheme is derived taking into consideration the distributed line model and the mutual couplings effect between the parallel lines to obtain accurate results. The proposed scheme is derived based on the transmission line theory and Taylor series expansion of the distributed line model parameters. All fault types including normal shunt faults, evolving faults, and cross-country faults can be discriminated from each other and the fault location can be obtained for all fault types. The evolving faults include earth faults occurring at the same location in two phases of one circuit or two phases of different circuits at different fault inception time. While cross-country faults include earth faults occurring at different locations in two phases of one circuit or two phases of different circuits at same or different fault inception time. The proposed scheme is tested under different fault locations, different fault resistances, different fault inception angles, and all fault types including cross-country and evolving faults. Also, the effect of different sampling rate, measurement and synchronization errors, earth resistivity variations, and transmission line parameters errors on the proposed scheme is considered. Simulations studies conducted by MATLAB software demonstrate that the maximum estimation error in fault location does not exceed 3.06%. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Transmission lines are very important for continuity of power supply. Since transmission lines are permanently exposed to dif- ferent faults, the precise fault location is essential to repair the faulted line and minimize the outage time [1,2]. The transmission line faults include normal shunt faults (line to ground (LG), double line to ground (LLG), double line (LL), and three line (LLL)), evolving faults, and cross-country faults. Cross-country faults include earth faults occurring at different locations in two phases of one circuit or two phases of different circuits at same or different fault inception time. Cross-country faults which occur at same location between two different circuits are also defined as inter-circuit faults which appear in double-circuit transmission line. Inter-circuit faults are easily located because the inter-circuit faults occur at one location compared with the cross-country faults occurring at two different locations. Cross-country faults which include two phases in dif- ferent locations at same or different fault inception time are very ∗ Corresponding author. E-mail address: a saber 86@yahoo.com (A. Saber). difficult to obtain their locations. While the evolving faults include earth faults occurring at the same location in two phases of one circuit or two phases of different circuits at different fault incep- tion time. In other words, the evolving faults consist of primary earth fault which beginning in one line and secondary earth fault in another line at the same location. For single pole tripping func- tion, the secondary faulted phase must be recognized. However, the faulty phase selector cannot easily recognize the secondary faulted phase because the evolving faults are more complex than normal shunt faults. Generally, conventional fault location techniques can be divided into four main categories. The first category uses the fundamen- tal frequency components measurements [3–8]. The second one includes techniques based on the fault generated traveling waves [9–14]. The third category applied soft computing methods such as artificial neural network [15,16], genetic algorithm [17], combined wavelet-fuzzy [18,19], and adaptive neuro-fuzzy [20] for transmis- sion line fault location. The last category is based on fault-induced transient analysis for high frequency signals [21,22]. Moreover, the use of synchrophasor measurements for multi-terminal parallel transmission lines has been presented in open literature [23–29]. http://dx.doi.org/10.1016/j.epsr.2017.08.038 0378-7796/© 2017 Elsevier B.V. All rights reserved.