Loadflow analysis

Abstract

The main objective of a modern electrical power system is to satisfy the load demand as economically as possible, and with, a reasonable level of continuity and quality. Obviously, to satisfy these requirements, the primary requisite is a generation capacity which provides a reasonable assurance of meeting the bulk load and which allows preventive maintenance of generation units without endangering ·the electrical system. Given an adequate generation capacity, it is essential to have a properly designed and operated power system structure, which provides the demanded energy at the various load points. The transmission capacity of the system, the character of the load and its effect on the overall system performance take on a special significance. The power flow calculations in the various links making up the network, is a basic tool in this area. One of the most important factors that affects the performance of the energy system, is the system structure. This future is usually classified into different areas: according to voltage levels! However, for analysis of the system, it is advantageous to divide the whole transmission network into two main areas, the bulk transmission and distribution facilities, which are not distinguished· on a voltage level criterion alone. The local power network consists of two such areas. The distribution section is, as in most larger systems, almost completely disassociated from the rest of the system. Once the· location and size of the terminal station issuing the bulk power have been determined, the distribution system planning becomes almost independent process. The bulk transmission section consists of a small bulk power feeder system, operated at 33 KV, which interconnects the main distribution centres to the power station, and a larger sub transmission section operated at 11 KV. The difference between these two areas is also highlighted in the structure of the network. The distribution level tends to have a radial structure with energy flowing in a predominant direction. The bulk transmission level has a loop structure which gives more path combinations and several branches are characterized by parallel feeders. The transmission level is, of course, the most important section of the power network since its designed and development is governed by present and future load flow patterns and load volume. Due to its loop structure, the analysis of this part of the .network is necessarily complex and the use of the computer is indispensable. Such computer-based analysis proved to be of high efficiency and relevant accuracy. The development of such a computer program for the need of the local power station is the main objective of this project. The difficulties and the importance of the loadflow problem has fascinated mathematicians and engineers for a number of years. With the advent of the digital computer attention has been directed towards the use of numerical methods for analysis. Today sophisticated loadflow computer programs exist especially for large interconnected power systems. Such programs, one may assume, are the result of a certain amount of effort and technical ability, for they are still expensive to procure. For this reason, I tried to contact several major power companies in Europe, particularly in West Germany and Italy, to provide me with a loadflow program for this project, to no avail. Consequently, I decided to develop a computer program which was tailored to the specific local needs, making use of available library books and publications. Naturally, I had to give special consideration to the computer facilities afforded to me at the University and by a local private company, to which I am most grateful.