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Power Quality and the Office Buildingby Peter Kratochvil, President - Cos Phi Inc.
This concern stems from the increased use of electronic equipment such as computers, laser printers, fax machines, electronic lighting ballasts, etc. Why this rapid increase? This is because there are constant pressures on businesses to be more efficient, faster, more accurate, more competitive and more technical. Technology is changing rapidly, becoming more and more user friendly. The equipment has become very accessible even to very small businesses. However, there are pitfalls that come with all the benefits of becoming more computerized and technologically advanced. Every office environment, regardless of size, is now equipped with one or more computers, printers and fax machines. Then we add the lighting factor with fluorescent lights using electronic ballasts. All this electronic equipment utilizes electrical energy in a different manner than the way it was used by non-electronic equipment. Electronic equipment draws electrical energy in spurts or pulses (see figure 1); however, the electrical utilities can only deliver electrical energy in a sinusoidal form of 60Hz (see figure 2). The electrical distribution system is also designed to operate at that 60Hz frequency in a sinusoidal form. As a result, a heavy concentration of electronic equipment alters the use of electrical energy, thus causing an incompatibility problem.
Incompatibility ProblemThe incompatibility problem is not a matter of "if", but rather a matter of "when". The next natural question is: how does a building owner/manager know when these problems will arise? Electronic equipment used in a one or two office setting will seldom create problems. High concentrations such as is found in office towers or buildings, however, will almost always create problems at some point in time. It is a matter of being either proactive or reactive. Do you wait until you are experiencing computer lock ups, burned out power supplies on printers, or a catastrophic failure of your UPS system? If you do, you must at this point take a reactive approach. On the other hand, one can be proactive. With careful planning, analysis of the existing electrical distribution, and a proper grounding system on the premises, any improvement in technology - such as the implementation of an energy saving project retrofitting the premises with electronic ballasts, or adding a number of new computers - should not create a problem. Disasters such as burning up the distribution transformer, or having overloaded neutral wires, can be avoided. And so can unnecessary maintenance costs. How to Avoid DisastersWe can avoid disasters first by analyzing the characteristics of the electrical system such as determining the type of load on the distribution panels and monitoring the addition of all new loads. Second, we can check the integrity of the grounding system. For some of these investigations, you may have to call upon an expert in the field of power quality. It is important to know that you may be creating a problem while trying to become more efficient. All power quality problems can be corrected, but correction after the fact is always more expensive than prevention. In some cases, the correction can be more expensive than the cost of the original implementation - not to mention the inconvenience and frustration. Most commercial buildings built prior to 1990 are very probable candidates for experiencing incompatibility problems with the electrical system. It is only within the past five years that power quality has become an issue, and it is only since then that the electrical distribution system in the building may have been brought up to date with the new demands of its users. The electrical code is also changing to allow for the new uses of electrical energy. However, some of the effects of concentrated electronic equipment are still going to be a concern, even with the newer installations. This is primarily because there is still a lack of guidelines in many areas of power quality. Too often the electronic equipment that is causing the problem is the equipment most sensitive to its own effects. Combine this with a heavy concentration of electronic and computerized equipment, and the problem can become uncontrollable. Cure for Problems
Before you run out to purchase correction or mitigation equipment - and further frustrated yourself - find out what causes the problem. All mitigation equipment is designed for a specific purpose. The shot in the dark approach may not proved to be effective, and many times it can make the problem worse. The impact of nonlinear equipment on the electrical system, as well as grounding, is a function of impedance. Remember all these effects are governed by the laws of physics - not by black magic. Also, optimization of the mitigation or correction is a question of experience in the field - knowing when to correct the source of the problem, or when to protect sensitive equipment. Recognizing that power quality is a matter of compatibility and upgrading the electrical distribution system accordingly is also a solution, but sometimes not always practical. As the technology evolves it is important to keep in mind that good power quality is more and more critical. As we acquire computers that are faster and smaller, the internal workings of these pieces of equipment become increasingly sensitive to the quality of the electrical power. It is becoming difficult to keep up with technological changes that affect us on a daily basis, and it is impossible to become a power quality expert overnight. However, it is possible to know when you need one, and how you find a good one. A good idea, as you read trade magazines on these issues, is to start collecting a file on some of the authors and presenters of power quality papers. It is our experience with clients that many times they have had a number of different people trying to solve the problems to no avail. Also, when a disaster occurs, there is no time to find, interview and select a power quality expert in the local yellow pages. As a result, the trial and error method to find a solution to the problem has gone totally out of proportion. It is also important to find out the experience of the power quality consultant and the area he/she specializes in, as there are a number of power quality areas such as grounding, transient problems, flicker problems, static problems, EMI, EMF, RFI and incompatibility. Power Quality AnalysisA power quality analysis is like a
total check-up of the function of the electrical distribution system. This may
include a grounding survey, a harmonic survey or infrared thermo graphic survey,
as well as physical inspection. This analysis will determine the possible
problem areas, as well as load thresholds for nonlinear equipment, which will
prepare the It is important to know what to do with the results from the analysis. This sometimes may require modelling the electrical distribution and conducing load flow studies in order to prescribe a proper cure for the problem. When solving a power quality concern, the mitigation may consist of efforts to redistribute loads, balance loads, upgrade the grounding, derate transformers and wiring, install filters and traps, and so on. Once the immediate power quality issues are dealt with, attention then turns to methods of ensuring that good power quality is maintained. It is a good idea to develop a power quality policy for the premises. This may mean a policy on the method of acquiring electronic equipment, monitoring additions of equipment, establishing a grounding procedure, and logging occurrences of nuisance problems and breakdowns. The maintenance of a policy on power quality will require some work, but just like the daily backup of computer data, the reward is a reliable operation of equipment as well as an improved and more efficient work environment. 
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There is no such thing as an
"off-the-shelf" cure for power quality problems.
building owner/manager for anticipated expansion plans or provide an early
warning of impending problems. |