More? Or Less?

The word "government" often invokes “regulation” (at least until it was replaced with “bailout”). However, governmental regulation of power quality is basically nil in North America, especially in the United States. This is in contrast to other places, where aspects of power quality beyond just nominal voltage range and frequency are covered. Phenomena such as harmonics, voltage fluctuations that cause light flicker and the somewhat obscure “mains signaling voltage” are covered by numerous standards that carry the weight of law. While the exact reason for the difference is subject to debate, there are few regulations that the electrician, facility manager or homeowner can cite to determine if the power being received is adequate to run the equipment being powered.

Many documents from U.S. standards--making organizations—the Institute of Electrical and Electronics Engineers (IEEE), the American National Standards Institute (ANSI) or the National Electrical Manufacturers Association (NEMA)—are referred to as “recommended practices” or guides, rather than standards. A standard uses mandatory language, such as “shall,” while recommended practices use “should” or “may” and could not be adopted into law since they are written in an informative style rather than the form of a legal requirement. IEEE Std 519-2005, Recommended Practices and Requirements for Harmonic Control in Electric Power Systems, is among the most-often cited and perhaps most misused power quality documents. It applies to the point-of-common-coupling (PCC) between the electric service and the customer, yet is often applied to transmission systems as well as at the point of utilization.

So, what leverage can the end-user have with regard to the quality of the supply from his or her electricity provider? Two documents carry some clout in the United States. The first is ANSI C84.1-2006: The American National Standard for Electrical Power Systems and Equipment—Voltage Ratings (60 hertz), which has been adopted by many Public Utility Commissions since its inception more than 50 years ago. Even this has some confusion about it, as there are the service-voltage tolerances (95 to 105 percent) from the nominal voltage that must be maintained up to the PCC as well as utilization voltage tolerances (87 to 106 percent) at the connection point of the equipment. Then there are Range A and Range B. Range A includes these tolerances, and Range B affords wider tolerance for voltage levels that are limited in the number, extent or duration of their occurrence. However, there is no restriction for the limits or for the occurrence of voltages beyond Range B—just that they should be addressed in a timely manner.

The other enforceable standard in many states is the National Fire Protection Association’s (NFPA) 70-2008, the National Electrical Code (NEC). The NEC allows for a 5 percent difference between the service and utilization voltages, which normally is allocated as 3 percent on the feeder circuit and 2 percent on the individual branch circuit. The Code addresses harmonics somewhat by dealing with the issues of the neutral or grounded conductor when there are significant nonlinear loads in a facility. But the NEC does not, nor was it intended to, cover power supply quality any more than the plumbing codes cover the quality of the water or gas that flows through the pipes installed by plumbers following those codes.

Then, there is the problem of voltage unbalance in a three-phase system, which can have a damaging effect on motors and other electromagnetic equipment. NEMA MG-1 recommends derating a motor by 10 percent for a

3 percent unbalance. IEEE 1453 indicates that a reading of voltage fluctuation of perceptibility short term greater than 1 will be noticeable by most people as light flicker, but then what? Impulsive transients, oscillatory transients, interharmonics, DC offset, noise, notching, or something as potentially damaging as even-order harmonics, have little chance of being limited in the United States in the near future, as we tend to favor recommended practices over regulation.

The future of regulations

We seem to prefer a market approach to resolution of such matters, which can work if none of the parties have monopolistic control of the situation. But having seen my electricity rates double in the past two years following the end of the initial regulations applied to electric utilities by the “deregulation” legislation, I am not sure which direction would really improve the quality of the supply, improve productivity, and reduce the carbon footprint. And did you hear that the government is now going to help make the grid “smart,” the definition of which is subject to interpretation by no less than 80 different organizations?

BINGHAM, a contributing editor for power quality, can be reached at 732.287.3680.

About the Author

Richard P. Bingham

Power Quality Columnist
Richard P. Bingham, a contributing editor for power quality, can be reached at 732.287.3680.

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