Chapter 1 - System Studies

Abstract

This chapter describes three main areas of transmission and distribution network analysis, namely, load flow, system stability, and short circuit analysis. Such system studies necessitate a thorough understanding of network parameters and generating plant characteristics for the correct input of system data and interpretation of results. The analysis work, for all but the simplest schemes, is carried out using tried and proven computer programs. The application of these computer methods and the specific principles involved are described by the examination of some small distribution schemes in sufficient detail to be applicable to a wide range of commercially available computer software. A load flow analysis allows identification of real and reactive power flows, voltage profiles, power factor, and any overloads in the network. Once the network parameters have been entered into the computer database the analysis allows the engineer to investigate the performance of the network under a variety of outage conditions. The effect of system losses and power factor correction, the need for any system reinforcement, and confirmation of economic transmission can then follow. A short circuit analysis allows the engineer to determine the make and break fault levels in the system for both symmetrical and asymmetrical, low or high impedance faults. This in turn allows the correct determination of system component ratings, for example, the fault rating capability of circuit breakers. A full analysis will allow investigation of protection requirements and any changes to the system that might be necessary to reduce fault levels.