Arab J Sci Eng (2018) 43:2779–2792 https://doi.org/10.1007/s13369-017-2778-6 RESEARCH ARTICLE - ELECTRICAL ENGINEERING Simultaneous Network Reconfiguration with Distributed Generation Sizing and Tap Changer Adjustment for Power Loss Reduction Using Imperialist Competitive Algorithm G. Ing Koong 1 · H. Mokhlis 1,2 · J. J. Jamian 3 · H. A. Illias 1,2 · W. M. Dahalan 4 · M. M. Aman 1 Received: 3 October 2014 / Accepted: 1 August 2017 / Published online: 20 September 2017 © King Fahd University of Petroleum & Minerals 2017 Abstract This paper presents a simultaneous network recon- figuration with DG sizing and tap changer adjustment to minimize power loss in a distribution system. Imperialist Competitive Algorithm is used to identify the best set com- bination of reconfiguration, DG size and tap changer. The performance of the proposed method has been tested on 33 bus distribution system at different load levels and differ- ent scenarios of DGs location. The test results indicated an improvement of power loss reduction as compared to exist- ing method. Furthermore, the simultaneous approach is able to produce lowest power loss than any combination of two components simultaneously. At the same time, voltage also maintains within allowable limit. Keywords Network reconfiguration · Distributed genera- tion · Tap changer · Power loss · Imperialist competitive algorithm B H. Mokhlis hazlie@um.edu.my 1 Department of Electrical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia 2 University of Malaya Power Energy Dedicated Advanced Centre (UMPEDAC), Level 4, Wisma R&D UM, Jalan Pantai Baharu, University of Malaya, 59990 Kuala Lumpur, Malaysia 3 Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia 4 Department of Electrical Engineering, Malaysian Institute of Marine Engineering Technology, University Kuala Lumpur, 32000 Kuala Lumpur, Perak, Malaysia 1 Introduction Power system is the most bulky system in the world, which can be subdivided into three main parts: generation, trans- mission and distribution. A transmission system transfers electrical energy from the power plant to various substations. Meanwhile, a distribution system carries the electricity from the substations and delivers to the consumers. Among all, the greatest power loss of the power system is contributed by the distribution systems. Since single power source is at the grid of the distribution system, electrical energy is dissipated as power loss during the delivery process. In order to reduce the power loss, well-known approaches like network reconfiguration and installation of distributed generation (DG) are commonly employed. Distribution net- work reconfiguration is a process that involves opening sectionalizing switches and closing tie switches, while radial configuration of the distribution system is maintained. The earliest work on network reconfiguration named ‘branch and bound’ method has been proposed by Merlin and Back [1]. In this work, all switches in the entire distribution network are closed to establish a mesh network. Then, one by one of the switches will be opened until the radial configuration is found. The process is then repeated until the minimum power loss is obtained. This method is extended by Shirmohammadi and Hong [2]. However, the only difference is that the switch with the lowest current flow obtained from the load flow anal- ysis will be opened. Civanlar [3] proposed a simple formula to calculate the change in power loss due to branch exchange. These heuristic algorithms are time-consuming because only one pair of switching operation can be considered at a time. With the advacement in optimization methods, meta- heuristic algorithms have been applied for network recon- figuration problem with single [4] and multi-objective [5]. For example, a refined GA is proposed in [6] with reduced 123