A New Surge Protection System and a New Method of Surge Detection Using Fiber Optics

Abstract

A new, economical protection system using fiber optics has been developed to protect existing local metallic cable systems from lightning. A field trial system was installed at a hilltop microwave relay station which is often struck by lightning. The characteristics of the system and its fiber optics were investigated using a specially developed surge detection method employing fiber optics. A direct lightning strike demonstrated that the whole system functions very successfully and provided valuable data on surges. Replacing the whole length of metallic cable with fiber cable would eliminate surge problems completely, but would be prohibitively expensive. We believe that a hybrid system presents the most economical solution. Using the system described to protect from direct surges requires the replacement of only the first few hundred meters of metallic cable. The rest of the system can be protected from induced surges by conventional means. Thus by applying this system to existing telecontrol or telecommunication cables, their reliability can be greatly increased at relatively little cost. Further, the new method of surge detection developed in relation to this system shows many advantages over previous methods, and has the potential for wide application.