Electric Power Systems Research, 8 (1984/85) 155 - 169 155 Operating Reserve Determination and its Influence on the Operating Costs of Interconnected Power Systems JORGE F. RIVERA, FRANCISCO GARCES and PEDRO E. MERCADO lnstituto de Energia El~ctrica, Universidad Nacional de San Juan, Av. Libertador San Martin 1109 (Oeste), 5400 San Juan (A rgentina) (Received August 4, 1984) SUMMARY A methodology to carry out reliability studies to compute operating reserve require- ments of in terconnected systems is formulated. This paper shows the application of devel- opments carried out at 'Instituto de Energia Eldctrica' in order to calculate the operating reserve requirements, their composition in relation to the access times of different kinds of reserve, and the influence that equipment variations will have on the electric power system operation costs. The calculation of power interchange between areas is performed with a stochastic model of the system. In this model the differ- ent levels of assistance capacity of each area are associated with their occurrence probabil- ities. Covering of own demand has priority. Interconnecting lines between areas are modeled by probabilities associated with their possible states. This methodology allows adequate consider- ation of operating conditions in power systems planning. System optimal operation costs are calculated under the constraint that there is suf- ficient operating reserve (stand-by plus spinning reserve) to guarantee a given reliability level. The main aim of this work was the applica- tion of this methodology to the Sistema Nacional Interconectado Argentino (Argentine National Interconnected System) for assessing a first approach to operating reserve composi- tion and requirements. In addition, the influence on the operating costs of including a pumped storage power plant located in the province of Buenos Aires is evaluated. 1. INTRODUCTION Generation and transmission facilities are required to meet the demand at a certain time and in a certain place, and so generation reserve and reliability must be considered in relation to the network configuration. In the development of more complete studies on the interconnected system of interest, some relevant aspects which have to be taken into account are the operating reserve in the system, the generating system capability which constitutes such a reserve, the probabil- ity of assistance between areas and the influence on the operating costs of the reserve configu- ration adopted. From such studies carried out with modern computational algorithms based on probabilistic models, the advantage of introducing modifications to generating facilities can arise. 2. OBJECTIVES AND SCOPE OF THE RESEARCH In this work, the main purpose is to formu- late a methodology for reliability studies relating to the operating reserve configuration of interconnected systems including hydro- thermal and nuclear generating plants. By means of these studies, computation of the operating reserve requirements, composition and operating costs is possible. A practical application of such a methodol- ogy to a real interconnected system is presented in §7. The research covers the following aspects: • Formulation of basic criteria for operation, with special emphasis on the operating reserve of generating facilities and interconnected networks already determined for the electrical system under study. • Definition of operating reliability measure- ments for the electrical system in question. • Discussion of fuel costs with reference to the interconnected system's optimum operat- ing mode and to the required reliability level, 0378-7796/85/$3.30 © Elsevier Sequoia/Printed in The Netherlands