Skip to main content
main-content

Über dieses Buch

Digital Signal Processing in Power System Protection and Control bridges the gap between the theory of protection and control and the practical applications of protection equipment. Understanding how protection functions is crucial not only for equipment developers and manufacturers, but also for their users who need to install, set and operate the protection devices in an appropriate manner.

After introductory chapters related to protection technology and functions, Digital Signal Processing in Power System Protection and Control presents the digital algorithms for signal filtering, followed by measurement algorithms of the most commonly-used protection criteria values and decision-making methods in protective relays. A large part of the book is devoted to the basic theory and applications of artificial intelligence techniques for protection and control. Fuzzy logic based schemes, artificial neural networks, expert systems and genetic algorithms with their advantages and drawbacks are discussed. AI techniques are compared and it is also shown how they can be combined to eliminate the disadvantages and magnify the useful features of particular techniques.

The information provided in Digital Signal Processing in Power System Protection and Control can be useful for protection engineers working in utilities at various levels of the electricity network, as well as for students of electrical engineering, especially electrical power engineering. It may also be helpful for other readers who want to get acquainted with and to apply the filtering, measuring and decision-making algorithms for purposes other than protection and control, everywhere fast and on-line signal analysis is needed for proper functioning of the apparatus.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract
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, considering it as a primary good and even as one of the human rights.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 2. Abnormal States in Power Systems and Criteria for Their Recognition

Abstract
The protection equipment is applied with the aim of minimizing the effects of faults and other abnormal phenomena on the operation of electrical power systems. An electrical power system is considered as all the plants required to generate, transmit and distribute electrical power, including generators, power transformers, lines and cables, circuit-breakers, etc.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 3. Hardware and Functional Development of Protection Devices and Systems

Abstract
The age of protection began some 105 years ago, when control apparatus were for the first time connected to current and voltage transformers, which reduced the primary currents and voltages to secondary levels. The secondary currents and voltages could be processed to generate TRIP or NO-TRIP decisions.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 4. Fundamentals of System Analysis and Synthesis

Abstract
Synthesis of digital power system protection systems is possible with application of many advanced and complex mathematical tools. Understanding of digital systems, digital signal processing, analysis and synthesis of digital filters require transformations between time and frequency domain as well as transitions between continuous and discrete data and systems. All of them belong to the family of methods being a part of signal and system theory and use Fourier, Laplace and Z transforms as well as Fourier series as the most important mathematical basis.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 5. Infinite Impulse Response Filters

Abstract
Digital filters allow to pass assumed spectrum part or particular component of the signal and prevent from passing the other signal components, sometimes called noise. Similarly to analog filters one can distinguish: low pass, high pass, band pass and band rejection digital filters.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 6. Finite Impulse Response Filters

Abstract
Digital finite impulse response (FIR) filters produce output signal realizing weighting sum of actual and preceding input signal samples.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 7. Correction of Errors Introduced by Instrument Transformers

Abstract
Whatever sophisticated algorithms of signal processing are further used, the overall performance of the protection relay is also a function of quality of the analog signal pre-processing path including current and voltage transformers, analog antialiasing filters and A/D converters.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 8. Measurement Algorithms for Digital Protection

Abstract
In case of protection devices of pre-digital era that were made in analogue technique the processes of measurement and decision-making were integrated. Magnitude or phase comparators were applied and thus the measurement of criterion values could not be realized directly.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 9. Characteristics of Measurement of Criterion Values and Adaptive Algorithms

Abstract
Standard control systems are designed and evaluated taking into account dynamics and required accuracy for various input signals. Digital protection systems should also be evaluated in a similar way, however, the fundamental parameter is time needed to take decision concerning the state of protected element of the power system. Sometimes it is as short as a fraction of period of the fundamental frequency component. This decision time, different for various power system elements, is usually fixed to avoid possible extended damage of protected plants. For some criterion values and some decision-making methods the final decision is to be done even during transient states of measurement when one can still expect substantial errors criteria values determination. This is why while designing a protection system one must take dynamic features of measurement algorithms into consideration and perform optimization of its elements and the entire system as a decision-making device.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 10. Decision Making in Protective Relays

Abstract
Having in mind that protective relays are devices that are supposed to evaluate the state of the protected plant and to react properly in case of abnormal operating conditions, the relay final output is usually the command to trip the protected element or to raise an alarm, whenever it is necessary. Before a tripping signal to the associated circuit breaker or an alarm is issued the decision is to be taken that is based on the locally measured criteria values and additional information from other protective relays and/or control centers. While in preceding chapters the measurement techniques and algorithms were presented, here the possible approaches to the decision making are outlined and the detailed decision procedures are described.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 11. Elements of Fuzzy Logic in Protective Relays

Abstract
As mentioned, in the preceding chapter on decision-making, the protective relay equipped with standard, deterministic signal processing algorithms (measurement with fixed data window, discrimination with fixed thresholds or characteristics) may not perform properly for all conceivable power system operating conditions.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 12. Application of Artificial Neural Networks

Abstract
The signal processing methods and algorithms described in preceding chapters were expressed in form of explicit equations, transfer functions and/or logic rules, either in crisp or in fuzzy versions. There are, however, specific tasks and power system operation conditions when, especially for the problems that are complex and difficult to express in terms of traditional means, other solutions should be applied. In such situations, both for signal processing and decision making Artificial Neural Networks may constitute a good solution.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 13. Genetic and Evolutionary Algorithms for PSP

Abstract
In this chapter the procedures originating from biological evolution are presented that can be applied e.g. for intelligent searches and optimization in power systems. The procedures belong to the so-called “biological programming” family, which is not limited to the genetic algorithms only. In wider sense the neural networks described in Chap. 12, being an analogy of human brain, are also good examples of this family.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 14. Expert Systems

Abstract
Expert System (ES) is a kind of software that simulates the problem-solving behavior of a human expert of given domain. ES can be used to solve a complex problem or give an advice, mainly in cases when the amount of data to be processed is very high. There is no sense to apply ESs for simple decision problems, they should be used wherever a conventional data processing (DP) solution is not possible or may appear troublesome. Referring to Fig. 14.1 one can say that instead of traditional DP by algorithmic, well-defined methods, expert systems perform processing of knowledge and make intelligent searches.
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Chapter 15. Artificial Intelligence: Summary and Hybrid Schemes

Abstract
The artificial intelligence methods presented in Chaps. 11–14 require a lot of computational power but, in return, provide flexibility and possibility of handling imprecise or missing data. Despite their differences, they all offer soft-signal processing skills, thus one can say that they all form a family of soft computing that can be defined as follows:
Waldemar Rebizant, Janusz Szafran, Andrzej Wiszniewski

Backmatter

Weitere Informationen