Development of Optical Fiber Current Sensors and Their Applications

In this paper, a development of optical fiber current sensors is presented, and examples of their applications are also introduced. Optical fiber current sensors based on the Faraday effect were expected for a long time as compact and high performance current sensors in place of conventional current transformers. However, widespread practical application of them has not come true yet, because of complex means necessary for securing stable characteristics. In the development stated here, such problems were solved by using a special sensor fiber made from flint glass, and by constructing sensing systems matching with features of the fiber. The developed sensors are immune to the effects from outer environment such as vibration and temperature changes. Also they are compact and flexible, and can be attached easily around the current conductors. Examples of application of the sensors are also introduced. They are field tests of the sensors for application to protective relaying systems, cable current measurement using a portable type sensor, a fault section locating system using the sensors.