Page 9 - Power Electronic Control in Electrical Systems

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1

Electrical power

systems ± an overview

1.1 Introduction

The main elements of an electrical power system are generators, transformers,
transmission lines, loads and protection and control equipment. These elements are
interconnected so as to enable the generation of electricity in the most suitable
locations and in sufficient quantity to satisfy the customers' demand, to transmit it
to the load centres and to deliver good-quality electric energy at competitive prices.
The quality of the electricity supply may be measured in terms of:
. constant voltage magnitude, e.g. no voltage sags
. constant frequency
. constant power factor
. balanced phases
. sinusoidal waveforms, e.g. no harmonic content
. lack of interruptions
. ability to withstand faults and to recover quickly.

1.2 Background

The last quarter of the nineteenth century saw the development of the electricity
supply industry as a new, promising and fast-growing activity. Since that time
electrical power networks have undergone immense transformations (Hingorani
and Gyugyi, 2000; Kundur, 1994). Owing to the relative `safety' and `cleanliness'
of electricity, it quickly became established as a means of delivering light, heat and
motive power. Nowadays it is closely linked to primary activities such as industrial
production, transport, communications and agriculture. Population growth, techno-
logical innovations and higher capital gains are just a few of the factors that have
maintained the momentum of the power industry.