Accuracy improvement of impedance-based fault location method for power distribution network using distributed-parameter line model Rahman Dashti and Javad Sadeh * ,† Electrical Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran SUMMARY Power Distribution System (PDS) is spread on different places. Therefore, PDS has many laterals and load taps. Accurate fault locating in PDS causes to improve reliability indices and its efficiency. In this paper, an improved method is suggested for fault location in PDS, which has a high accuracy. In the proposed algorithm, by using phase domain of distributed-parameter line model, a fifth-order algebraic equation of fault distance is obtained, which can improve the accuracy of determined fault distance for all types of faults. The proposed method is tested under different fault resistances in which the results show low sensitivity to this parameter. To evaluate the accuracy of the proposed method, the modified IEEE 34 Node Test Feeder is used, and its efficiency and accuracy is proved. Copyright © 2012 John Wiley & Sons, Ltd. key words: power distribution network; fault location; distributed-parameter line model 1. INTRODUCTION Distribution networks are dispersed in each urban and rural region and are crossed from each alley and street. Each distribution feeder has many laterals, sub laterals, load taps, balanced and unbalanced load and different types of conductors. Power distribution systems (PDSs) are subjected to fault conditions caused by various sources such as adverse weather conditions, equipments failure and external object contacts. Owing to the expansion of distribution network, it is very difficult and complicated to locate the fault in these networks. Most of the researches presented so far in the field of fault location are focused on the fault location on the transmission lines; however, these algorithms are not directly suitable for locating the fault on the distribution networks because distribution systems are usually unbalanced in nature, such as mixed single-phase and three-phase laterals, non-homogeneous feeders, non-homogeneous phase conductor and unbalanced loading. These features can cause some problems in fault location algorithm. Generally, fault location methods are divided into two main categories: (i) Traveling wave-based methods; in these methods, high frequency components of voltage and/or current that are measured at substation are applied [1,2]. The disadvantage of these methods is the need for high-sampling frequency; consequently, applying these methods is very expensive. (ii) Impedance- based methods, in which the fundamental frequency component of voltage and current that are measured at substation are used [3–5]. These methods generally can be easily applied and are cheaper than the other. Distribution fault location system (DFLS) is proposed in [6]. In this paper, fundamental components of voltage and current at the beginning of feeder are used for determining the distance of fault by calculating apparent impedance. In this method, static load and short-line model are assumed. The suggested algorithm is tested on PDS, which has some laterals, load taps and unbalanced load. The proposed method in [6] is developed in [3] by considering the dynamic load model and estimating the amount of load. However, this method is based on the statistical equations for determining the *Correspondence to: Javad Sadeh, Electrical Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran. † E-mail: sadeh@um.ac.ir Copyright © 2012 John Wiley & Sons, Ltd. INTERNATIONAL TRANSACTIONS ON ELECTRICAL ENERGY SYSTEMS Int. Trans. Electr. Energ. Syst. (2012) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/etep.1690