New Technologies, Standards, and Maintenance Methods in Spacer Cable Systems

The overhead distribution lines with bare conductors for medium-and low-voltage circuits are being substituted due to their failure rate and security level, particularly in adverse areas i.e., heavy trees and high isokeraunic levels. The failure rate in CEMIG´s medium-voltage overhead distribution lines, in urban areas, is 0.9 failure/km-year. More and more customers ask for better services and lower costs. These types of systems are greatly influenced by external causes such as lightning, rain, trees, collision, and vandalism. In Brazil, based on U.S. experience, the Aerial Spacer Cable System has been shown as the best system to improve its reliability. The low-maintenance cost, easy operation, high security level, and the attractive cost benefits have justified its use, mainly in urban areas, by CEMIG, a Brazilian utility. In the MV Spacer Cable System were included other technologies, such as the CSP transformer, SF6 switch, medium-and low-voltage polymeric arresters, low-voltage multiplex cable, and wedge and piercing connectors. The CEMIG´s Spacer Cable System has been performing at an average failure rate of 0.04 failure/km-year. This paper describes the line design, equipment, standards, and maintenance methods in live-line and field experiences of Spacer Cable System in our company, with the technical support of Hendrix Wire & Cable, USA, and Wirex Cable, Brazil. Other utilities in Brazil are now using this system, to meet one of the government´s requirements of improved reliability. It is a great alternative for companies searching for high reliability for their distribution electrical system.