Introduction - Digital Signal Processing in Power System Protection and Control - page 1

Chapter 1
Introduction
Electric power system is a backbone of contemporary technical civilization and
today's economy. One cannot imagine functioning without stable, uninterruptable
supply of electric energy that is needed both in industry and in most areas of our
private lives. The users of electric energy treat it sometimes as granted, consid-
ering it as a primary good and even as one of the human rights.
Electric energy is produced in power plants and then transmitted over long
distances and distributed to the final consumers, industrial and domestic. The
electric network is a vast structure embracing a lot of generators in power plants or
distributed energy sources, hundreds of thousand kilometers of lines, thousands of
transformers, busbars, and other equipment. This structure has to be maintained,
controlled and protected against possible faults and other abnormal phenomena.
Thus a great variety of protection and control devices aimed at smooth and stable
running of power systems have been developed and installed in modern power
networks. Most of them are nowadays produced in digital technology, performing
their functions through numerical calculations and signal analysis.
Many topics related to power system protection and control describe the basic
theory as well as applications of protection principles, which result from under-
standing of physical nature of encountered phenomena, to protection of particular
elements of power networks and to maintaining system integrity. Therefore the
authors are not going to cover the same field again. Instead, deeper insight into
functioning of digital protection and control devices is proposed, which includes
both hardware and software details. This topic is meant to provide thorough
information on signal processing methods and algorithms that are used for mea-
surement of protection criteria values, being a basis for final decision making in
protective relays.
This topic is aimed at bridging the gap between theory of protection and control
and practical applications of protection equipment. Understanding the ways of
protection functioning is crucial not only for equipment developers and manu-
facturers but also for their users that are going to install, set and operate the