International Journal of Innovative Technology and Exploring Engineering (IJITEE) ISSN: 2278-3075, Volume-9 Issue-3, January 2020 908 Published By: Blue Eyes Intelligence Engineering & Sciences Publication Retrieval Number: B8031129219/2020©BEIESP DOI: 10.35940/ijitee.B8031.019320 Abstract: The present-day power system is vulnerable to instability and security threats due to the continuously changing load pattern. To enhance the security of the power system and to avoid the electrical power system from collapsing, the condition of the system security has to be inspected by security analysis tools and it can be enhanced by the proper integration of FACTS devices into the network. This paper presents a methodology in which the security of the system can be analyzed with the help of an index called Line Overload Severity Index (LOSI). Unified Power Flow Controller (UPFC) is preferred to improve the security of the power system. Owing to the cost involved in placing UPFCs it is obligatory to use minimum number of devices, by optimally placing them in the network. It is obligatory to recognize an ideal location to install UPFC. Considering the Line overload Sensitivity Index, the optimal location identification for UPFC is done. The paper also presents the formulation of a new severity function using transmission line loadings. The severity function combines the objectives of reducing transmission line loadings and improvement of voltage profile during multi line contingencies. In the event of multi-line contingencies, the objective function for reducing the fuel cost and the severity function are analyzed. Optimal power flow method is followed to analyze the security of the electrical power system during contingency situations. This optimal location identification procedure and the OPF are solved using a metaheuristic technique, Whale Optimization Algorithm (WOA). The whole methodology that is proposed is experimented on a standard IEEE-30 bus test system. Keyword: Contingency, Power system security, Severity function, Unified power flow controller, Whale optimization I. INTRODUCTION The existing power grid is a more intricate, interconnected system due to hazardous increase in load demand and the continuously changing load pattern. The load will normally be unevenly distributed and it affects the voltage profile which may make the system security more vulnerable. The condition even worsens during contingencies. So, in recent days, operating and controlling the power system has become one of the challenging tasks to sustain the . Revised Manuscript Received on January 5, 2020 * Correspondence Author H. Arul Devi*, Research Scholar, Department of Electrical Engineering, Annamalai University, Annamalainagar, Chidambaram, Tamilnadu, India.Email: aruldevi90@gmail.com R. Kannan, Associate Professor, Department of Electrical Engineering, Annamalai University, Annamalainagar, Chidambaram, Tamilnadu, India. Email: kannanr79@gmail.com S. Padma, Associate Professor, Department of Electrical Engineering, Annamalai University, Annamalainagar, Chidambaram, Tamilnadu, India. Email: spadmapnr@gmail.com reliability and continuity of the supply. The security of the system should be examined to evade unrestrained conditions such as overloading of lines, violations in bus voltages, and the extreme case of system collapse . Adding new infrastructure like installing new transmission lines and increasing power generation capabilities by inclusion of new generating units are restricted to technical and economical boundaries. So, the most preferable solution is to exaggerate the capabilities of existing power system infrastructure and generating capacities by the incorporation of FACTS devices into the network. The integration of FACTS devices is the best substitute for improving the performance of the electrical power system by enhancing the voltage profile, improving the power transfer capability and reducing the losses. The applications of FACTS devices includes the enhancement of power transferring capacity of transmission line and regulation of different parameters in transmission network like line voltage, line current, line impedance and phase angle. The power flow can be made flexible or controllable with the help of the FACTS devices. FACTS devices aids in increasing the network’s lodability by decreasing the flow of apparent power in the overloaded lines. Because of this the transmission line losses can also be reduced. FACTS devices are capable of tackling voltage collapse issues and system security improvement. Congestion management can be easily handled by the usage of such devices. The power system easily accommodates the changes that will occur with the addition of the FACTS devices. For upgrading the system performance and improving economic benefits, optimaly locating FACTS devices and settings the parameters of the controllers is very essential. To evade uninhibited conditions such as overloading of lines, violation of bus voltages and system collapse the analysis of system security is mandatory [1]. Since the power system operating conditions continuously changes dynamic security analysis is essential in finding the condition of the system.[3]. It can be analyzed based on loading of transmission lines and variations of bus voltages. The security constraints combined with Optimal Power Flow (OPF) can resolve this problem.[1]. FACTS devices perform a vital part in Demand Side Management (DSM) and by this means controls the transmission line congestion. Integration of the FACTS devices boosts the desirable parameters of the power system like bus voltage magnitudes, apparent power flow in lines and diminishes the overall system losses [4-7]. The chore of security augmentation can be verbalized as a problem with multiple objectives. The numerous objectives considered are minimization of fuel cost and the cost involved in installing UPFC [2-3][15]. The UPFC can be designed as a power injection device. Optimal Placement of FACTS Devices Based on Whale Optimization Algorithm for Power System Security Enhancement H.Arul Devi, R. Kannan, S.Padma