A while back, I wrote about a house with 14 kilowatts (kW) of solar panels installed on the southern exposure roof. Voltage and current monitoring at the breaker panel prior to the solar panel installation had shown 10–12-volt (V) deep sags occurring as frequently as every 22 minutes.
At a recent meeting, a comment was made that many power quality (PQ) monitor users purchase equipment that is just “good enough.” PQ monitors can be a significant capital equipment purchase for some companies, particularly smaller electrical contracting firms.
When people send in data from a power quality monitor to be reviewed, some common questions include “Is my site normal?” and “Does this data look OK to operate my facility?” Such questions usually get the same ambiguous answer: “It depends.” The quality of electric power as supplied and how much is
Maybe it is because they are rarely seen by the human eye or because the proliferation of surge protector strips makes everyone feel immune, but transients still exist and can wreak havoc with electrical equipment.
While few would argue about of the wealth of information on the Internet, there isn’t a mechanism for qualifying its accuracy. Basically, anyone can post anything. Even such peer-reviewed sites as Wikipedia can fall short of the facts. A relatively simple concept in power is a good example.
I often give my power quality (PQ) 101 course to new engineers or salespeople. This introduction starts with the basics: an overview of PQ phenomena based on IEEE 1159 Table 4.2 followed by Ohm’s and Kirchhoff’s laws and how they apply to power quality.
The electrical energy usage in most industrial and commercial facilities follows a reasonably consistent pattern from week to week, so a one-week monitoring program usually is adequate to determine what can be done to save 10–20 percent on electric bills.
When considering power quality disturbances or the quality of the electrical supply, phenomena such as rms variations (sags, swells and interruptions), harmonics, unbalance and flicker usually come to mind.
There is an old saying that liars figure and figures lie, which implies that the truth can be a challenge to discern from both people and data. At a recent standards-making conference, I encountered some examples of this concept that seemed worth sharing.
A customer recently called me about the information on his power quality monitor screen. He said about a dozen different events were showing up, but the lights had just blinked once. He wanted to know what all of the other nonsense was supposed to tell him.
A hot summer’s evening usually begets long lines at the local ice cream shop. Recently, at one such shop, the line grew extra long when the cash registers and credit card machines mysteriously powered off and on.
The blinks and flickers referred to here can best be described as “voltage fluctuations on electric power systems [that] sometimes give rise to noticeable illumination changes from lighting equipment.” The Institute of Electrical and Electronics Engineers (IEEE) standard that covers this is about to
When one of the coaches was asked before the “big game” what would be the key to his team’s success, he said, “executing the fundamentals.” While blocking, tackling, passing and catching may work for football, Ohm’s and Kirchhoff’s Laws are fundamental to understanding any power quality issue.