IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 _______________________________________________________________________________________________ Volume: 03 Issue: 05 | May-2014, Available @ http://www.ijret.org 626 TRANSMISSION LINE LOADABILITY IMPROVEMENT USING FACTS DEVICE R.H.Bhesdadiya 1 , C. R. Patel 2 , R. M. Patel 3 1 Research Scholar, School of Engineering, RK University, Rajkot, Asst. Prof. L.E.C. Morbi, Gujarat, India 2 PG Scholar, Department of Electrical Engineering, L. E. College, Morbi, Gujarat, India 3 Principal, HJD institute of Technical Education and Research, Kera, Gujarat, India Abstract With the recent trends towards deregulating power systems around the world, transfer capability computation emerges as the key issue to a smoothly running power market with multiple transactions. Enhancement of available transfer Capability (ATC) is an important topic in current deregulation environment considering loop flows and heavily loaded lines. The thermal limits of transmission lines, voltage bounds of buses and upper and lower limits of generator power are considered. In this paper, optimal placement of the STATCOM is found based on Linear Sensitivity Index (LSI). The Modified IEEE 30-bus test system is selected to illustrate the placement of STATCOM and enhancement of ATC by using PSAT software version 2.1.8. Keywords: Available Transfer Capability, TTC, Linear Sensitivity Index, PSAT. ---------------------------------------------------------------------***--------------------------------------------------------------------- 1. INTRODUCTION Due to the significant power demand increases, the transmission line operators are required to increase transmission line power transfer capability. They have various options such as building an additional parallel transmission line which is not a cost effective option, using FACTS device for reactive power compensation is a very cost effective option with the former one. It has faster response than capacitor banks. In this present open access or deregulated environment all the producers and buyers of electrical energy desire to produce or consume large amounts of energy and may force the transmission system to operate beyond one or more transfer limits. This type of operation leads to congestion of the system. Therefore accurate determination of available transfer capability is essential to ensure the system security and reliability while serving a wide range of mutual and multilateral power transactions. There are several phenomenon can impose these transfer limits like thermal limits, voltage limits and stability limits [2]. For the understanding of these limits there are certain methods. Available transfer capability (ATC) is the measure of the ability of interconnected electric systems to reliably move or transfer power from one area to another over all transmission lines under specified system conditions [13]. For obtain ATC, the total transfer capability (TTC) is the largest power flow through selected interfaces of the transmission network which causes no thermal overloads, voltage limit violations or any other system problems [2]. Available transfer capability (ATC) calculation has been a research area of exponentially increasing interest particularly in the past two decades. Available transfer capability (ATC) is an important sub part of a TTC, which is calculated as [9]: ATC = TTC-TRM-CBM-ETC Where, TTC is the total transfer capability, TRM is Transmission reliability margin, ETC is the existing transmission commitment (including retail customer service), CBM is the capacity benefit margin. There are several methods for transfer capability calculations [1, 7, 11]. These methods mostly used are continuation power flow (CPF) method, optimal power flow (OPF) method and repetitive power flow (RPF) method, ANN based methods etc. In this paper presents an OPF based procedure for calculating the Available transfer capability (ATC) [3, 4].This method is based on an AC power flow solution which accurately determines voltage limits as well as the line flow effect. The objective function is to increase the loading capability of the transmission line. 1.1 Available Transfer Capability [ATC] Available transfer capability computations are necessary for successful operation of electric power deregulation where power producers and customers share a common transmission network for wheeling power from the point of generation to the point of consumption. The available transfer capability indicates the amounts which inter area bulk power transfers can be increased without compromising system security[1]. The value used for available transfer capability affects both system security and the profits made in mass power transactions. Moreover, market participants can have contradictory interests in a higher or a lower available transfer capability. Thus in