Introduction

Abstract

Modern day power systems are complicated networks with hundreds of generating stations and load centers being interconnected through power transmission lines. An electric power system has three separate components — power generation, power transmission and power distribution. Electric power is generated by synchronous alternators that are usually driven either by steam or hydro turbines. Almost all power generation takes place at generating stations that may contain more than one such alternator-turbine combinations. Depending upon the type of fuel used for the generation of electric power, the generating stations are categorized as thermal, hydro, nuclear etc. Many of these generating stations are remotely located. Hence the electric power generated at any such station has to be transmitted over a long distance to load centers that are usually cities or towns. Moreover, the modern power system is interconnected, i.e., various generating stations are connected together through transmission lines and switching stations. Electric power is generated at a frequency of either 50 Hz or 60 Hz. In an interconnected ac power system, the rated generation frequency of all units must be the same. For example, in the United States and Canada the generation frequency is 60 Hz, while in countries like United Kingdom, Australia, India the frequency is 50 Hz. In Japan both 50 Hz and 60 Hz systems operate and these systems are interconnected by HVDC links.