ISSN: 2278 – 8875 International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering Vol.1. Issue 6, December 2012 Copyright to IJAREEIE www.ijareeie.com 563 Effect of SVC on Composite Power System Reliability Level Abdullah M.Shaalan 1 , Mohammed AbdulqaderSurrati 2 , Zamil Chair for Electricity Conservation, King Saud University 1 Saudi Electric Company,Kingdom of Saudi Arabia 2 Abstract: The major goal of an electric power system is to provide its customers with a good service at a minimum cost and an acceptable reliability level. Power system reliability is based on two basic considerations, namely, adequacy and quality. This study investigates how to improve composite power system adequacy in the long- term. Specifically, to enhance system reliability level by using Power System Simulator for Engineering (PSSE), Static Var Compensators (SVCs) can be installed on each bus for the IEEERTS. It has been observed that the Expected Energy not Served (EENS) is reduced for all buses in the IEERTS, which means that the overall system reliability level has improved. Keywords: SVC – composite power system reliability level - EENS (expected energy not served) - PSSE, IEEE-RTS 1-INTRODUCTION OF PROBABILISTIC CALCULATIONS Electric power systems are continuously operating systems. Regular maintenance is needed to keep components in good condition and repairs are performed promptly in order to restore service. Therefore, each component can be represented as a two-state model. At any time, a component can reside in one of two states: in-service (available) and out-of-service (unavailable) [1]. The transition from available state to unavailable (outage)state is called a failure event, and is assumed to occur at a constant rate λ (failures per year). The transition from the out-of-service state to the in- service state is called a restoration event, and is also assumed to occur at a constant rate μ, in restorations per year. The mean duration that the equipment is in service is m years, while the mean duration that it is out of service is r years. The probability that the equipment is in-service is: = + (1) The probability that it is out-of-service is: = + (2) Thus, + =1 . The unavailability is the index adopted and used to assess reliability of the system; typically, its units are considered to be in hours/year or in minutes/year. The frequency, F (occurrences/year) to transition from the in-service state to the outage state is equal to the frequency of transition from the outage state to the in-service state, and is given by: = ∙ = ∙ (3) The average duration, D (in hours or days) per year that the equipment is in the outage state is: = (4) HenceEq. (2), to represent the probability of an outage for this equipment, only two parameters are required: F and D. Other characteristics can be derived from these two parameters: = 1 (5) = 1− . (6) = 1− . (7) The methodology used in PSSE™ program [3]for probabilistic indices calculations is based on state enumeration method . The sum of probabilities of all states is equal to1. Probabilistic indices of system failures are computed by identifying the set of states that satisfy failure criteria and the transition rates from any state inside the set to any state outside of the set. In Figure 1, a yellow node represents a state that has violations; all yellow ones form the set of states that satisfy failure criteria which is referred to as S. Failure criteria include branch overloads, bus voltages outside high or low limits, bus change exceeding deviation