The frequency stability of the interconnected electric grid in North America is a marvel of engineering. As shown in Figure 1, the deviation is rarely beyond 0.05 Hz from the nominal 60 Hz. In fact, during a given hour time period, this deviation is more like +/-0.02 Hz from the nominal value.
Supplemental and supplementary grounding electrodes are very similar in name but vastly different in their permitted uses. Understanding the differences in these two electrodes can be critical in providing a safe, Code-compliant installation.
In the latest edition of “Electrical Power Systems Quality” by Dugan, McGranaghan, Santoso and Beaty, the authors point out that “it is commonly stated at power quality conferences and in journals that 80 percent of all power quality problems reported by customers are related to wiring and grounding
When most people think of the word “government,” the word “regulation” is usually close behind. The government regulates the speed that you can drive on the highways, how much income tax you pay, how much pollution a factory can emit, even which drugs can be sold (legally).
The federal government has been driving the process to develop an interconnected standard to establish the criteria and requirements of distributed generation (also called distributed resources or dispersed generation) to be connected into the utility-owned electric power grid.
210.70 Lighting Outlets Required Article 210 specifies provisions for all branch circuits except for branch circuits supplying only motor loads. Article 430 contains motor load requirements. Provisions stipulating the placement of receptacle outlets are covered in 210.52 through 210.63.
CODE CITATIONS Article 210 Branch Circuits Article 220 Branch Circuit, Feeder and Service Calculations Article 250 Grounding Article 334 Nonmetallic Sheathed Cable: Types NM, NMC, and NMS Article 422 Appliances The General Information for Electrical Equipment Directory published by Underwriters Labo
210.63 Heating, Air-Conditioning and Refrigeration Equipment Outlet Article 210 specifies provisions for all branch circuits except for branch circuits supplying only motor loads, which are covered in Article 430.
As commercial, industrial and educational facilities become more dependent on information technology (IT) equipment for performing the day-to-day tasks, the quality of electrical supply that powers these growing loads becomes more of a factor.
A presentation at the PQ World 2002 Conference in October re-enforced the need to continue to make the electrical workplace a safer place to work in. While it would be ideal, it’s not always possible to de-energize electrical systems before working on them.