Power quality solutions for low and medium voltage critical loads

The growing use of power electronic and computers sparked the need for more precise power quality solutions. Variable frequency drives (VFDs) and programmable logic controllers (PLCs) provided the precision and control needed to accelerate industrial automation; and, large-scale computers revolutionized every business including medical systems in hospitals. As these devices provided huge productivity gains, their susceptibility to malfunction caused by voltage disturbances became apparent. Utility voltage fluctuations that were considered tolerable forty years ago now cause major problems with the performance of these devices. This paper addresses alternatives that are available to mitigate these events and provide cost effective solutions. This paper covers voltage sag, voltage flicker and outage mitigation systems ranging from 300 kVA at low voltage to over 10 MVA at medium voltage levels. Examples of actual installations will be presented along with information as to how the mitigation system choice was made.