A different kind of poison Every time I see the lights on a Christmas tree blinking on and off, I am reminded of the old adage, “One person’s medicine is another person’s poison.” Flickering lights in an office, factory or residential home can be more than an annoyance.
What do these statements have in common? • Lightning doesn’t strike the same place twice. • Electrical utilities correct a fault by sending a power surge to clear a short in a service line, transformer or other load grid short circuit.
Continuing to look at power quality’s biggest enemies As a continuation of last month’s article, here are a couple of additional “pictures” of the most popular PQ criminals for the office wall to help quickly identify what the squiggly lines mean and to find the source of problems.
Cooking Equipment Calculations, Part III 220.19 Electric Ranges and Other Cooking Appliances Article 220 of the National Electrical Code contains specifications for calculating branch-circuit, feeder and service loads.
Many changes have occurred to the National Electrical Code (NEC) since the first NEC was published on Aug. 31, 1897. Even though the electrical industry was in its infancy, this “first” NEC was remarkably insightful and has withstood the test of time.
Even without the pictures on the post office wall or the television show of almost the same name, being able to recognize the most popular power quality “criminals” can help quickly find the source of problems.
Specifications for calculating branch-circuit, feeder and service loads are in Article 220 of the National Electrical Code. This article is divided into four parts: I. General, II. Feeders and Services, III. Optional Calculations for Computing Feeder and Service Loads and IV.
At one time or other, all contractors have been faced with a decision to either recalculate the size of an existing service or feeder or just guess at the amount of spare load and install new circuits while hoping for the best. Guessing will usually only get you in trouble.
At the recent Power Quality World Conference, I chaired a session on “Specifying and Purchasing PQ Equipment.” Afterward, I met one of the presenters from an electric utility who said he planned to bring his lawyer with him to the session the next day.
Article 220 contains provisions for calculating branch-circuit, feeder and service loads. Following the requirements set forth in this article will provide the minimum size branch circuit, feeder or service.
A couple of months ago we dealt with lightning and the fast transients that can be coupled onto the electrical distribution system of the utility or within a facility, and the use of TVSS (transient voltage surge suppressors) to minimize the potential damage from such.