The basic laws of physics have been unchanged for the most part since Newton postulated gravity. These include the two principal laws that we use in solving many power quality problems, namely Kirchoff’s Law and Ohm’s Law.
When changes occur and a system doesn’t work properly anymore, it is often good to go back and review the events leading up to the change to determine the why’s of the past, along with the why’s of the present.
As non-linear loads proliferate in the industrial and commercial sectors, problems due to harmonic currents caused by these loads are becoming more common. However, the presence of harmonic currents is often not, in itself, a problem. The real problem may be some secondary effect they cause.
There are two worlds of overcurrent and overvoltage. The first is with AC power. The second is for twisted pair copper and the other lines, which are used in telephony and computer networks. It is the latter that we’ll cover here.
Power quality is very important because of its direct impact on your customer’s business. It used to be that if the power was on, your customer was in business. Today, it isn’t a question of whether the power is on; rather, it is a question of whether the power provided meets the equipment’s needs.
CODE CITATIONS Article 210—Branch Circuits Article 250—Grounding Article 424—Fixed Electric Space Heating Equipment Article 700—Emergency Systems Bonding gas piping Q: The November 2000 issue of Electrical Contractor magazine included a question about the required size of the bonding conductor to be
As I was preparing to disembark in the mother country after instructing a tutorial on flicker at the Institute of Electrical and Electronic Engineers (IEEE) Power Engineering Society winter meeting, I reflected upon the difficulties with communication, even among English speakers.
When I went through “Firefighter 101” training, the instructors emphasized that the primary purpose of a fire department is to prevent fires, not to put them out. The old adage that, “An ounce of prevention is worth a pound of cure,” applies to the power quality world as well.
One of my favorite scenes from the “Wizard of Oz” is when Dorothy stops at the traveling magician’s (soon-to-be Wizard’s) trailer. He tells her future by looking into the crystal ball while rummaging through her belongings for information about her when she closes her eyes.
If one plots the speed of the pendulum as it swings back and forth, the graph would be a sine wave. At the top of the arc, the speed is zero. Then it begins to travel faster and faster until the bottom of the arc.
While the screwdriver may still be one of the best tools for troubleshooting power- quality-related problems, another tool is very useful in determining the equipment’s susceptibility to the quality of the electrical supply.
Writing while listening to the sounds of the ocean surf can be therapeutic. The rise and fall of the waves is like the sine wave of the ac voltage waveform that is often used as the basis to compare with the quality of the power supply.
A plethora of solutions, often called “mitigating devices,” is being marketed for power quality-related problems. Choosing the best one for a particular facility and its problems is similar to prescribing the right medicine for an illness.