International Journal of Electrical and Computer Engineering (IJECE) Vol. 8, No. 4, August 2018, pp. 2602~2607 ISSN: 2088-8708, DOI: 10.11591/ijece.v8i4.pp2602-2607  2602 Journal homepage: http://iaescore.com/journals/index.php/IJECE Characteristic and Surge Impedance Variation Impact on Transmission Line Performance Muhyaddin J. H. Rawa Department of Electrical and Computer Engineering, King Abdulaziz University, Saudi Arabia Article Info ABSTRACT Article history: Received Jan 19, 2018 Revised Mar 28, 2018 Accepted Apr 5, 2018 Modeling of power systems is essential to perform various network analyses. Voltage regulation, line losses and transmission line efficiency are greatly affected by transmission line parameters. Hence, accurate modeling of transmission line is required. The aim of this paper is to study the impact of characteristic and surge impedances on voltage profile, voltage regulation and transmission line efficiency. Keyword: Characteristic impedance Surge impedance Transmission line modeling Voltage regulation Copyright © 2018 Institute of Advanced Engineering and Science. All rights reserved. Corresponding Author: Muhyaddin J. H. Rawa, Department of Electrical and Computer Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabia. Email: mrawa@kau.edu.sa 1. INTRODUCTION Modeling of power systems is essential in order to perform various power system analyses such as load flow studies, short circuit calculations, contingency analyses and transient analyses. Electric power generation, transmission and distribution networks need to be modeled carefully for accurate results. This paper aims to study the effect of characteristic and surge impedance on transmission line performance; therefore, accurate modeling of transmission lines are considered. In general, a “per-phase” model is used to represent equivalent circuits of transmission lines with appropriate circuit parameters. Depending on the length of the line, three different models are considered. Short transmission line model for length less than 80 km (50 mile) long, medium transmission line model for length between 80 km (50 mile) and 240 km (150 mile) long and long transmission line model for transmission lines longer than 240 km (150 mi) [1]-[5]. All lines are made up of distributed series resistance and inductance as well as shunt capacitance and conductance. They are called line parameters and denoted as R, L, C, and G. The most important parameters are R, L and C as they impact voltage drop, line losses and overall transmission line efficiency [6]-[9]. The paper is organized as follows. Short introduction regarding transmission line is given in Section 1. Modeling of transmission lines is discussed in Section 2. Section 3 describes transmission line voltage regulation and efficiency. The effects of characteristic impedance on transmission line performance are discussed in Section 4. The impacts of surge impedance on transmission line performance are introduced in Section 5. Summary and conclusion are discussed in Section 6.