Power quality considerations for installing sensitive electronics equipment-a utility´s perspective

Memphis Light, Gas and Water Division (MLGW) is the largest three-service public utility company in the United States. The electrical division is the largest customer of the Tennessee Valley Authority setting a peak demand of 2821 MW in the summer of 1995. In a company of this size, many issues compete for attention and resources. One of the priorities MLGW has set in allocating resources is to assist its customers in mitigating power quality issues and concerns relating to the installation of sensitive power electronics equipment such as adjustable speed drives, programmable logic controllers and electronic ballast lighting. Power quality issues such as voltage sags created by faults on the power system, transient overvoltages caused by the switching of the utility´s capacitor banks and harmonic currents injected into the power system by nonlinear loads are discussed in this paper. Information related to these concerns is essential for the successful interfacing of today´s “hi-tech” equipment with the utility´s power system. Several actual power quality field data are presented to affirm the aforementioned power quality concerns