(Please refer to ELECTRICAL CONTRACTOR magazine for referenced figures). On a single-phase circuit, the origin of a voltage sag is usually downstream if the neutral-to-ground voltage significantly increased during the sag.
For the past three years, this column has covered a different power quality-related topic each month. Now that most of the major areas have been covered, it seems as though it is time to use a different approach.
*Please see Electrical Contractor magazine for figure references.* 210.52(A) General Provisions Provisions stipulating the placement of receptacle outlets for dwelling units are covered in 210.52(A) through (H). Last month’s “In Focus” covered both paragraphs and the fine print note in 210.52.
Whenever energized electrical equipment is being examined, serviced, maintained or adjusted in any way, there is always the potential for an electrical explosion to occur, resulting in injury to the electrical worker and damage to the equipment.
• Please refer to ELECTRICAL CONTRACTOR magazine for referenced illustrations. 210.8(A) Dwelling Units Receptacles installed in certain locations must have ground-fault circuit-interrupter (GFCI) protection for personnel.
In a recent discussion about the virtues of power quality (PQ) monitoring with some less-than-knowledgeable business people, the point was raised that, “Why bother to figure out whose fault it is if you can’t fix it?” I responded to this comment by showing them some of the latest software tools avai
The upstream sags and interruptions caused by faults on the electric utility system are often blamed for being the root of all evil, yet studies have shown that most power quality (PQ) problems originate within the facility itself, as indicated from the following sources:
Last month’s article focused on power factor (PF) capacitor switching transients. Although most power quality (PQ) disturbances originated from within a facility, we will again focus on an upstream event relative to the point-of-common-coupling (PCC), alias the service entrance.
Having covered the basic laws governing how power quality events propagate through the electrical system, this column’s focus will shift now to “who done it,” or identifying the source of the power quality (PQ) events.
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.