Transmission voltage unbalance evaluation

This paper presents transmission level voltage unbalance as measured by two different methods across the Tennessee Valley Authority (TVA) Transmission system. It also discusses the recent focus on distribution voltage control. Two national standards mentioning voltage unbalance are discussed as well as TVA´s operations and limitations on voltage balancing. An example of equipment malfunction creating voltage unbalance is discussed. A team was formed to address voltage unbalance concerns and this team made a number of measurements across the TVA system. The team determined the average transmission system unbalance delivered to customer sites to be 0.59% (method 1) and 0.64% (method 2).