In the past 12 months, I have celebrated two career milestones. It has been 40 years since I began working as a junior development engineer, being the fifth engineer hired at Dranetz Engineering Laboratories when it was on the brink of explosive growth. At the time, the Model 606 Universal Disturbance Analyzer had features that were revolutionary for such an instrument—a microprocessor, a rectified input switch power supply, a thermal printer and 4 kilobytes of assembly language code—making it the first in a long line of power quality instruments that made the power-quality-monitoring industry. Now in its fifth generation, gigabytes of data are communicated wirelessly to handheld devices or servers, which are capable of capturing more data in one second than can be analyzed by hand in a week.
Equally important is my 20th anniversary of writing the Power Quality column for ELECTRICAL CONTRACTOR. Taking over from Bruce Lonie, one of the industry’s top experts at PowerCET, it was a new adventure to write about technical topics for nonengineers. While I had numerous papers published and presented at conferences around the world, it was a real test of what I knew to “write for the intended reader,” as the members of the NFPA 70B committee had re-educated me to do for the Electrical Equipment Maintenance book.
I know from doing PQ seminars for several years that I learned as much as I taught—or thought I taught. Tests aren’t just to see how much the students learn; they tell the teacher how well they teach.
Being an engineer, I like to track the topics I have covered, how often and when. From seminar audience and reader feedback, I address the more popular topics more often but ensure the full spectrum of power quality topics receive some air time. As the table above shows, for the past 20 years, the most common topics are about finding the PQ and how to improve it.
Another common question is “How bad is my power quality?” Standards help provide a basis for comparison. In nearly all of the PQ studies I have seen, the most common phenomena are sags and swells, the variations in rms voltage that can interrupt processes and cause large financial losses in just milliseconds. With the change in the electrical loads (and now supplies) over the past 40 years, it is not induction motors that are the biggest consumers of electrical power but nonlinear loads, which are the main source of harmonics.
To solve most PQ problems or do a benchmark survey, you need tools. While the instruments have changed considerably since the introduction of the Model 606, the fundamental rules that we use are still the same. Ohm’s and Kirchhoff’s laws still form the basis of just about every PQ analysis I have ever done.
Some of our “rule tools” have changed, such as the traditional power triangle using real power (watts) and reactive power (volt-amperes reactive) equaling the hypotenuse of apparent power (volt-amperes) when connected vectorially. Harmonic power distortion, as well as power factor being simply the cosine of the angle between the fundamental voltage and current waveforms, has made that obsolete. That’s now referred to as displacement power factor, while the “true” measure of power factor is watts divided by volt-amperes.
Other power quality phenomena—including transients, flicker, unbalance, rapid voltage change and frequency—aren’t unimportant. They just are less frequently found to be the source of problems in many systems. Though safety is not in the top 10, it is understood to be No. 1 when connecting a PQ monitor. Fortunately, the adoption of the requirements found in NFPA 70E have made significant inroads into working in an electrically safe work environment and keeping electrical contractors safer from injury or death.
Despite claims of some less knowledgeable but highly paid executives in companies I have dealt with over time, power quality is still an issue affecting the productivity, profitability and safety of businesses and the public. As distributed electrical energy resources continue to be deployed in the grid, the PQ challenges remain and can even be more complex. Fortunately, we have our expanding bag of tools to take up the challenge to keep the beer cold and the pizza hot.
Thanks for reading all these years, and I hope, with the continued help of the amazing editorial staff, I can help you to keep learning too.