Protective Relaying of Power Systems Using Mathematical Morphology
The basic operating principles of the most common types of protection relays have not changed for more than half a century. However, the calculations used to measure power system fault signals continue to cause problems with relay performance. As a result
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Q.H. Wu · Z. Lu · T.Y. Ji
Protective Relaying of Power Systems Using Mathematical Morphology
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Authors Prof. Dr. Q.H. Wu Dr. Z. Lu T.Y. Ji Dept. Electrical Engineering and Electronics University of Liverpool Brownlow Hill Liverpool L69 3GJ UK
ISSN 1612-1287 ISBN 978-1-84882-498-0 e-ISBN 978-1-84882-499-7 DOI 10.1007/978-1-84882-499-7 Springer Dordrecht Heidelberg London New York British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Control Number: 2009927244 c Springer-Verlag London Limited 2009 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms of licenses issued by the Copyright Licensing Agency. Enquiries concerning reproduction outside those terms should be sent to the publishers. The use of registered names, trademarks, etc., in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. Cover design: deblik, Berlin Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com)
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Preface
The basic principle of protective relaying of power systems has not changed for more than half a century. Almost all power system protective relaying algorithms are dominated by integral transforms such as the Fourier transform and the wavelet transform. The integral transform can only provide an average attribute of the signals or their components. The accuracy of the attribute extraction is significantly sacrificed by the assumption of periodicity of the signals if the integral transform is applied to transient signals. It is also well known that the signals are liable to be contaminated by noise in the form of exponentially decaying DC offsets, high frequency transients, harmonic distortion, errors caused by non-linearity in the response of the sensors, and unwanted behaviour of power systems. This contamination is often provoked by fault conditions, just at the time when the protection relay is required to respond and trip the circuit breaker to limit damage caused by the fault. On the other hand, as we know, in most protection relays, complex computation has to be undertaken within a sampling interval, no matter how small the interval, to calculate the coefficients relevant to the attributes of the signals by using the integral transform based on a window of samples, and to calculate the relaying algorit
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