Case Studies: New Options for Power Factor Correction

Utilities across the United States are increasingly using underground cable for both new construction and replacement of overhead facilities. The properties of the cable have a capacitive effect, which tends to raise voltage during light loading conditions and create leading power factor. Poor power factor can reduce the usable capacity of equipment, and transmission providers are increasingly pressuring distribution utilities to improve the power factor of their facilities. Longer, lightly used underground feeders, large motors, and other factors inherent to an electric distribution system can create voltage instability and other power quality issues which can compound the problem.Large motors also create an adverse effect on distribution systems, creating flicker and poor voltage conditions for other consumers sharing the same circuit. Combined with poor power factor, power quality issues are compounded.Historically, utilities have found it necessary to correct lagging power factor through the application of shunt capacitors. In recent years, trends have moved toward leading power factor, and along with it, the need to consider new options for power factor correction. The focus of this document is to highlight case studies of three rural electric cooperatives: provide an overview of their power factor issues, options that were considered, and final implementation.