In some casesthese power supplies make up a major portion of commercial building loads. The switch modepower supply draws current in narrow pulses from the utility. The produced harmonic currentstravel through cables, transformers, circuit breakers and produce voltages at the variousfrequencies. If these voltages become excessive, the equipment that produced them can shutdown, or potentially destroy itself. The solution to harmonic problems require detailed knowledge of the distribution system and theconnected loads.
Complexity is added in commercial buildings because most of the connectedload is random.
Any potential solution must be evaluated based on the effect to the entire powersystem, rather than a particular load. For a solution to be acceptable it must reduce the levels ofharmonics for all, or at least most, load conditions and never create adverse conditions. At times acombination of solutions is required to adequately reduce the harmonics present in the system. The site of the study was B.C. Systems, which is a communications centre for most provincialgovernment operations. A UPS is commonly used to supply critical loads such ascomputers.