International Journal of Computer Applications (0975 – 8887) Volume 78 – No.16, September 2013 41                   !                          !"           ABSTRACT This paper proposes, various design procedures for computing Power System Restoration Assessment Indices (PSRAI) for a TwoArea HydroThermal Reheat Interconnected Power System (TAHTRIPS) in a restructured environment with a load frequency controller optimized using Bacterial Foraging Optimization (BFO) algorithm. In the restructured scenario, as various types of apparatus with large capacity may enhance fast power consumption which causes serious problem in the frequency oscillations. The oscillation of system frequency may sustain and grow to cause stability problems in the system if no adequate damping is provided. The disturbances to the power system due to a small load change can even result in wide deviation in system frequency which is referred as loadfrequency control problem. Quick system restoration is of prime importance not only based on the time of restoration and also stability limits also plays a very vital role in power system restoration problems due to unexpected load variations in power systems. The simple conventional Proportional plus Integral (P I) controllers are still popular in power industry for frequency regulation as in case of any change in system operating conditions new gain values can be computed easily even for multiarea power systems. This paper focus on the computation of various PSRAI for TAH(with mechanical governor) TRIPS and TAH (with Electric governor) TRIPS unit based on the settling time concept, The design of the Proportional plus Integral (PI) controller gains are tuned using Bacterial Foraging Optimization (BFO) algorithm. These controllers are implemented to achieve a fast restoration time in the output responses of the system when the system experiences with various step load perturbations. In this paper the PRSAI are calculated for different types of possible transactions and the necessary remedial measures to be adopted are also suggested. Keywords Bacterial Foraging Optimization, Electric Governor, Load Frequency Control, Proportional plus Integral Controller, Restructured Power System, Power System Restoration Assessment Indices. 1. INTRODUCTION The electric power business at present is largely in the hands of Vertically Integrated Utilities (VIU) which own generation, transmission and distribution systems that supply power to the customer at regulated rates. The electric power can be bought and sold between the interconnected VIU through the tielines and moreover such interconnection should provide greater reliability [1]. The major change that had happened is with the emergence of Independent Power Producer (IPP) that can sell power to VIU. In the restructure environment it is generally agreed that the first step is to separate the generation of power from the transmission and distribution companies, thus putting all the generation on the same footing as the IPP [2]. In an interconnected power system, a sudden load perturbation in any area causes the deviation of frequencies of all the areas and also in the tieline powers. This has to be corrected to ensure the generation and distribution of electric power companies to ensure good quality. This can be achieved by optimally tuning LoadFrequency controller gains. Many investigations in the area of LoadFrequency Control (LFC) problem for the interconnected power systems have been reported over the past six decades. A number of control strategies have been employed in the design of loadfrequency controllers in order to achieve better dynamic performance. The efficient incorporation of controllers will modify the transient response and steady state error of the system. Among the various types of loadfrequency controllers, the most widely employed is the conventional Proportional plus Integral controller (PI). A lot of studies have been made related to LFC in a deregulated environment over last decades. These studies try to modify the conventional LFC system to take into account the effect of bilateral contracts on the dynamics [3] and improve the dynamical transient response of the system [47] under various operating conditions. With the restructured electric utilities, the LoadFrequency Control requirements especially the nominal frequency in an interconnected power system besides maintaining the net interchange of power between control areas at predetermined values should be enhanced to ensure the quality of the power