Studying influence of two effective parameters on network losses in transmission expansion planning using DCGA H. Shayeghi a, * , S. Jalilzadeh b , M. Mahdavi b , H. Hadadian b a Technical Engineering Department, University of Mohaghegh Ardabili, Ardabil, Iran b Technical Engineering Department, Zangan University, Zanjan, Iran article info Article history: Received 11 November 2007 Accepted 18 June 2008 Available online 8 August 2008 Keywords: Transmission network expansion planning Network losses Inflation rate Load growth factor DCGA abstract Transmission network expansion planning (TNEP) is a basic part of power network planning that deter- mines where, when and how many new transmission lines should be added to the network. Its task is to minimize the network construction and operational cost, while meeting imposed technical, economic and reliability constraints. Up till now, various methods have been proposed for solution of the static transmission network expansion planning (STNEP) problem. But, in all of them, the effect of two impor- tant parameters i.e., inflation rate and load growth factor on network losses has not been investigated. Thus, in this paper, STNEP is being studied considering the effect of inflation rate and load growth factor on the network losses in a transmission network with different voltage levels using a decimal codification genetic algorithm (DCGA). The effectiveness of the proposed idea is tested on the Garver’s six-bus net- work. The results evaluation reveals that the inflation rate and load growth factor have important effect on the network losses and subsequent network arrangement. In addition, considering the effect of two above-mentioned parameters (inflation rate and load growth factor) in expansion planning of transmis- sion networks with various line voltage levels is caused that the total expansion cost of the network (expansion costs and the operational cost) is calculated more exactly and therefore the network satisfies the requirements of delivering electric power more safely and reliably to load centers. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Transmission network expansion planning (TNEP) is an impor- tant component of power system planning. It determines the char- acteristic and performance of the future electric power network and influences power system operation directly. TNEP should be sat- isfied required adequacy of the lines for delivering safe and reliable electric power to load centers during the planning horizon [1–3]. The basic principle of the TNEP problem is to minimize the network con- struction and operational cost, while meeting imposed technical, economic and reliability constraints. Calculation of the investment cost for power system expansion is very difficult work because this cost should be determined from grid owners with agreement of cus- tomer and considering the various reliability criteria [4]. Generally, transmission network expansion planning can be classified as static or dynamic. Static expansion determines where and how many new transmission lines should be added to the network up to the plan- ning horizon. If in the static expansion the planning horizon is sep- arated for several stages we will have dynamic planning [5,6]. In majority of power systems, generating plants are located far from the load centers. In addition, the planned new projects are still so far from completion. Due to these situations, the investment cost for transmission network is huge. Thus, the STNEP problem ac- quires a principal role in power system planning and should be evaluated carefully. After Garver’s paper that was published in 1970 [7], much research has been done on the field of TNEP prob- lem until now. Some of this research such as [1–3,6,8–24] is related to problem solution method. Some others, irrespective of solution method, proposed different approaches for solution of this problem considering various parameters such as uncertainty in demand [5], reliability criteria [4,25,26] and economic factors [27]. Also, some of them investigated this problem and generation expansion plan- ning together [28,29]. Recently, different methods such as GRASP [3], Bender decomposition [6], HIPER [17] branch and bound algo- rithm [30], sensitivity analysis [15], genetic algorithm [1,11,20,24], simulated annealing [16] and Tabu search [12] have been proposed for solution of the STNEP problem. In all of these methods, the problem has been solved regardless to effect of inflation rate and load growth factor on network losses. In Ref. [8], a neural network based method was proposed for solution of the TNEP problem con- sidering both the network losses and construction cost of the lines. But the role of inflation rate and load growth factor has not been investigated in this study. In Ref. [10], the network expansion costs and transmitted power through the lines have been included in objective function and the goal is optimization of both expansion 0196-8904/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.enconman.2008.06.013 * Corresponding author. Tel.: +98 451 5519262; fax: +98 451 5512904. E-mail address: hshayeghi@gmail.com (H. Shayeghi). Energy Conversion and Management 49 (2008) 3017–3024 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman