National Conference on Recent Advances in Electrical Machines and Energy Systems (REMES) 2008, Changa, Gujrat. 1 Abstract—The Transfer Capability Computation and its improvement emerges a key role in the deregulated electricity market over the last decade around the world. It is highly recognized that, with the capability of flexible power flow control and rapid action, FACTS technology has a wide spectrum of impacts on the way the transmission system operates, in particular with respect to thermal, voltage and stability constraints[6]. This paper represents repeated power flow (RPF) approach for Total Transfer Capability (TTC) calculation and further improvement of the same has been investigated with the application of FACTS devices (TCSC/ SVC). The devices were tested on a 4 bus test system and IEEE 30 bus system. It has been observed that TCSC is more effective than SVC for the improvement of TTC when both the thermal limits and voltage limits are considered simultaneously and the location of such devices play an important role. Index Terms— TTC, RPF, Flexible AC Transmission System (FACTS), Thyristor Controlled Series Compensator (TCSC), Static Var Compensator (SVC). I. INTRODUCTION HROUGHOUT the entire world, the electric power industry has undergone considerable changes in the past decade in order to promote competition to meet peak load demand. The Federal Energy Regulatory Commission (FERC), USA realizing the need for real competition ensured that the transmission facility should be open to all participants of the power market. According to FERC, Available Transfer Capability (ATC) information must be available through Open Access Same time Information System (OASIS). ATC is *Corresponding Author T. Malakar, Electrical Engineering Department, National Institute of Technology, Silchar. Assam. Puja Dash, Department of Electrical Engineering, DRIEMS, Cuttack, Orissa. defined as a measure of transfer capability in the physical transmission network, for transfer of power for further commercial activity, over and above already committed uses. According to NERC definition [3], ATC is determined as a function of increase in power transfers between different areas through selected interfaces. As the transfers increase, the flows in transmission lines increase. The Total Transfer Capability (TTC) is the largest value of electric power that can be transferred over the interconnected transmission network for which there is no thermal overloads, voltage limit violations, voltage collapse or any other system security problem with or without a contingency. The TTC minus the base case flow and appropriate transmission margin is the ATC for the selected interface. The most common approaches for transfer capability calculation are: 1) Security Constrained Optimal Power Flow (SCOPF) method. 2) Continuation Power Flow (CPF) method [4]. 3) Tracing Load Flow (TLF) method [7]. 4) Repeated Power Flow (RPF) method. The SCOPF method maximizes the total generation supplied and load demand at specific buses by optimal distribution of generation and load. CPF method finds the maximum value of a scalar parameter in a linear function of changes in injection at a set of buses in a power flow problem where as it ignores the optimal distribution. TLF is basically a load flow program that has the flexibility to change any input parameters in a systematic way and trace the state variable changes. The RPF method repeatedly solves power flow equation at a succession of points along the specified transfer directions. The advantage of the RPF approach is its simple implementation and ease with which it can take voltage stability constraints into account. In this work, RPF method is applied to compute TTC. The effect of contingency 1 is also considered in the TTC calculation for each case. Since TTC is limited by most heavily loaded lines or buses with relatively low voltages, Flexible AC Transmission System (FACTS) technology can play a major role for improving TTC by controlling bus voltage magnitude, phase angle and line reactance. Thyristor Controlled Series Compensator (TCSC) and Static Var Compensator (SVC) are two main generic types of FACTS devices commercially available [11, 12]. By controlling the firing angle of thyristors, TCSC can change line apparent reactance smoothly and rapidly whereas SVC is Enhancement of Total Transfer Capability in Restructured Electricity Market using FACTS Devices (July 2008) T. Malakar*, Puja Dash T