Development of the switched capacitor bank controller for independent phase switching on the electric distribution system

Summary form only given. Alabama Power Company has an ongoing program to improve the voltage profile of the 115 kV transmission system. This program includes the installation of a large number of distribution line capacitors. Initially, the distribution line capacitors were installed in the traditional fashion as fixed installations. However, with the wide spread deployment of Distribution Automation, consideration was given to switch the distribution capacitor installations to dynamically meet the electric distribution system´s reactive load requirements, while supporting the 115 kV transmission system. Since the beginning of the Distribution Automation project, the distribution line has been monitored on a per phase basis with the deployment of each Distribution Automation device. This deployment strategy clearly demonstrated the dynamics and independent operation of the individual phases in the distribution line. This paper describes the development of the switched capacitor controller for application on the electric distribution system at Alabama Power Company. The development and operation of the switching algorithm will be reviewed. The packaging solution includes running the switching algorithm in the polemounted Remote Terminal Unit to facilitate one enclosure on the pole. The switching of the capacitors on a per phase basis is reviewed with closing being performed on zero voltage crossing and opening being performed on zero current crossing to minimize the impact and disturbance on the electric distribution system. The switched capacitor banks are monitored and controlled by the distribution system operator using the Supervisory Control And Data Acquisition (SCADA) technology that has been installed for Distribution Automation. The effect and impact on power quality is briefly discussed.