Over the past 10 years, I have transitioned from the engineering side of power quality in industrial/commercial facilities to a hands-on home improvement construction business. I am still amazed at how many power quality problems are encountered in the typical home. When there is an issue with power quality, especially in industrial applications, the financial stakes can be high and the issues often easily visible—though few know their problems are PQ-related.
If a financial institution experiences downtime because the backup power system had undetected damage to the rectifier circuits, or the mail is delayed because harmonic resonance caused the power factor capacitors to frequently explode, or the lights go out during halftime at the Super Bowl, these problems make the news. In any residence, however, many of the same problems exist and go undetected for years, unless they lead to a fire or other similarly destructive event.
The RMS voltage variations that occur on distribution systems are experienced in homes, office buildings and factories. A 20-cycle sag to 70% of nominal voltage in a plastic extrusion factory, causing the injection molding machine to trip offline and the plastic to solidify in the machine as a result, is more costly to mitigate than the oven shutting off and not automatically restarting to finish cooking dinner.
An obvious solution
Sometimes the power quality problem is obvious. For example, the intermittent sags became a single-phasing problem at a residence, leaving the left half of the house without power for hours. After a recent occurrence of this issue, the homeowner contacted the company that was contracted for 24/7 service. They couldn’t come to look at the problem that occurred on Sunday afternoon until Monday, so I was called in to investigate the deafening beeping.
The situation pointed to their hard-wired fire alarm and phone system, which were not operational due to dead backup batteries. If the voltage sag problem had been properly addressed by the utility company when the PQ monitoring report was sent to them six months prior, and if the homeowner had been periodically testing her detectors and not ignoring those annoying beeps every minute, this wouldn’t have become a safety issue for the residents.
Common sources of PQ problems
Flicker, or “voltage fluctuations that cause modulated visible light output,” affects residences as much as commercial facilities. The resulting “sick building” syndrome can occur in the home, though few people would recognize the source. Lately, it is the flickering of LED bulbs on incompatible dimmer switches that is a common complaint, though the source is usually different from the cause of flicker in the past.
Voltage transients, especially resulting from direct or indirect lightning strikes, can have destructive results if not properly mitigated. In past articles, case studies illustrated the destructive results from lack of adequate surge protective devices and improper wiring and grounding. The 2020 NEC requires that a Type 1 or Type 2 surge protector be installed with service replacements and upgrades. There is still the problem with telecommunication and other external wires that enter a dwelling unprotected, but it’s a start.
One of the most common sources of PQ problems is in the wiring and grounding. Nearly every residence I have done renovation work on in the past 10 years has had one or more PQ issues. There have been missing grounds, reversed line and neutral conductors, inadequate wiring size, illegal neutral-to-ground connections in junction boxes and unbalanced current loading resulting in voltage unbalance.
Though I am not suggesting that a financially successful business could be based on solving PQ problems in homes, it is worth the effort to correct them (with the homeowner’s consent) for safety and power quality.
On a personal note, this is the 300th article I have written for ELECTRICAL CONTRACTOR on a subject that has captivated my interest for all 45 years of my professional career. It might seem odd that any subject would take that many words to explain (300 x 800 words), yet PQ problems are often very complex and interdependent situations. I credit the NFPA 70B Electrical Equipment Maintenance committee members of the 1990–2010 era and the editors of this magazine for helping to teach me how to turn such a technically challenging subject into a discussion that is understandable for those tasked with finding and fixing PQ-related problems. I also am indebted to those who have raised questions on the topics covered in the magazine, conferences and seminars I have contributed to. As the saying goes, the way to really know what you think you know is to try to teach it to someone else.
Header image source: Shutterstock / Moloko_Vector
About The Author
BINGHAM, a contributing editor for power quality, can be reached at 908.499.5321.