Ryuzo Kimata, Koji Yoshida, T.A.Scheeade, Dr. Lazlo Varga, Dr. Otto Guter
Composite cables with optical-fiber ground wire (OPGW) support both power transmission and data communication, making more effective use of real estate and line facilities. The inclusion of optical fibers within the cable structure, however, means that the temperature rise limit differs from that of conventional overhead ground wires. Specifically, in power line ground faults, virtually all of the short-circuit current flows in the ground wire, resulting in large instantaneous rises in temperature that are a major factor in power line design. Further the OPGW structure incorporates elements not previously used in power lines, such as pipes, spacers, etc., and this increases the error in calculating ordinary short-circuit temperature rise. A study was therefore carried out to calculate short-circuit temperature rise, taking into account the structural features specific to OPGWs, and personal computer software was developed. Comparisons with results from short-circuit tests at a representative conductor size confirmed that calculations were accurate to within 5%.