Power Quality Primer

International Journal of Electrical Engineering Education, Apr 2002 by Bollen, Math

This is still one of the few books on power quality. In fact, the only other book covering the whole power quality area is the one by Dugan et al. (Electric Power Systems Quality). Two books on the same subject, even by the same publisher, calls for a comparison. But first an overview of the contents of this book.

The book consists of nine chapters, each addressing the whole power quality field from one specific viewpoint. Each chapter is a rather closed text, without much reference to other chapters. The chapters can thus be read in an arbitrary order.

* Chapter 1 (introduction) explains the interest in power quality, introduces both sensitive load and nonlinear load, discusses deregulation, and presents the various players in the power quality field.

* Chapter 2 (power quality characteristics) introduces the various types of power quality disturbances and mentions some of the ways in which these can be quantified.

* Chapter 3 (power quality standards) gives a fairly complete overview of the various standard documents that are currently in place. The author discusses both IEEE and IEC standards.

* Chapter 4 (power quality solutions) presents a large number of mitigation devices available to solve power quality problems. Each of the devices is discussed briefly, with emphasis on the practical aspects. At the end of the chapter, a table is given relating various problems to various devices.

* Chapter 5 (wiring and grounding) looks at again another aspect of power quality. This chapter holds to the opinion that the majority of power quality problems originate at the customer's premises. This chapter can be seen as a sequel to Chapter 4: solving power quality problems without investing in mitigation devices.

* Chapter 6 (power quality measurement tools) discusses the various meters and analysers available to get a grip on power quality: from the good old kWh meter to internet-based multi-monitor based systems. The chapter even includes a picture of the type of monitor that we use in our own lab.

* Chapter 7 (power quality surveys) gives a lot of hints on how to perform a power quality survey: how to find out through measurements what the problem is. The author cites the old saying `it's better to prevent than to cure', but most of the text is directed towards finding problems, not towards preventing them.

* Chapter 8 (power quality economics) is the place where mathematics come in (or at least some equations). The trade-off between the costs due to the problem and the costs of solving the problem is the basis of this chapter. The text gives some useful information and in fact gives a better overview of available mitigation methods than Chapter 4.

* Chapter 9 (future trends) discusses the results of deregulation on power quality and introduces contracts as a way of solving power-quality problems.

* The book ends with a 40-page glossary and a 7-page biography for those interested in further reading into the subject.

This book is obviously not written for academics like me. It appears to be written for those who need a hands-on knowledge of power quality. In fact, it gives even less theoretical background than Dugan's book. And where Dugan et al. give an excellent, albeit somewhat superfluous in academic eyes, overview of power quality, Kennedy's volume touches on a lot of issues without giving the reader any understanding. Some information is even wrong, or at least outdated. One of the pictures shows a load current that is lagging the voltage by more than 90 degrees. This is not impossible, the load has become a generator, but the picture doesn't increase understanding. The statement that `harmonics are the major source of sinewave distortion' is simply not true. Harmonics are just a way of describing the distortion. And the Fourier series is not an approximation, but an exact description. In Chapter 4, the author gives a number of drawings related to the TVSS, without explaining how the device actually works. In Chapter 5, active and reactive voltage drops are treated in the same way. A minor point is that the author uses the old numbering for IEC standards (IEC 1000 is now IEC 61000).

Another problem with the book is that the various chapters appear to be written independently from each other. Chapter 4 states that the best solution is at the end-user equipment, whereas according to Chapter 5, wiring and grounding should be looked at first. Both statements are actually made quite often by power utilities, as if there is any difference between wiring and grounding at the customer premises and wiring and grounding within the utility network. In Chapter 6 it states that `presently, the power quality industry lacks an international standard on flicker'. This is nonsense. In fact Chapter 4 mentions such a standard (IEC 61000-4-15). Chapter 9 (future trends) lacks a discussion about the need for power-quality standards. Where the electromagnetic compatibility standards are mentioned in Chapter 3, they appear to be forgotten here. Treating power quality as within the EMC standards would ultimately solve all compatibility problems by defining 'exactly' who is responsible for providing the various solutions.