Voltage uprating of overhead transmission lines

In recent years, uprating of existing overhead power line has become a popular option for electric utilities to address increasing demand for power. Uprating overhead line by increasing voltage allows considerable increase in power transfer capability. This paper initially examines technical issues and conventional methods of uprating the voltage of overhead transmission lines. It then considers a case of existing 275kV line in L3 tower to analyse these issues and propose appropriate process for its possible uprating to 400kV system. In this case, phase-to-earth clearance was found to be a key issue for voltage uprating. Application of line surge arresters along the line was proposed for controlling overvoltage thereby reducing the minimum required clearance for 400kV system.