The Factors Influencing the Measurement Errors of All Fiber-Optical Current Transducer and Solutions

Using optical methods for measuring electrical currents have significant advantages. Optical current transducers are typically done by means of the Faraday magneto-optic effect. All fiber-optical current transducer (AFOCT) is a new kind of optical current transducer, with many merits over traditional current transducer. It is usually used for monitoring, protection and measurement in high-voltage power grid. This thesis presents basic theory of all fiber-optical current transducer. And three main types of it and their principles are introduced. Linear birefringence in optical fiber is a fundamental reason influencing the performance and sensitivity of all fiber-optical current transducer, so it severely limits practical application of all fiber-optical current transducer. The causes of linear birefringence in optical fiber are discussed and some methods are devised to solve this problem. They are including using some special kinds of optical fiber, such as low linear birefringence optical fiber, high circular birefringence optical fiber, spun optical fiber, twisted optical fiber or annealed optical fiber. Light source and other optical devices also introduce measurement errors. It is important to choose appropriate optical devices. This paper discusses their effect upon all fiber-optical current transducer and suggests several solutions to reduce measurement errors. And some environmental factors, such as temperature fluctuation and vibration also affect all fiber-optical current transducer significantly. So the temperature compensation and vibration-proof measures are also essential.