The Optical Fiber Electrical Current Sensor

Abstract

In this work an optical fiber current sensor was designed and implemented using helium-neon laser (with wavelength of 632.8 nm and power of 1 mW) as light source, single mode fiber based sensing element and photomultiplier as detector. The optical sensors used for measuring electrical currents are, in fact, magnetic field sensors based on the magneto-optic Faraday Effect in optical fiber, and its importance is coming from the fact that measuring electrical currents in high voltage substations using conventional current transformers (CT) utilize an iron core and windings ratio to step down the current measured in the primary to a more manageable current level for secondary devices such as meters and relays. This signal may be distorted due to saturation of the magnetic core or electromagnetic waves interference, and it is usually an issue that involves a great deal of insulation. The use of optical technology in this field greatly reduces the need for insulation considering its intrinsic dielectric characteristics and immune from electromagnetic interference. This sensor is presently designed to cover current in the range of (20 A to 450 A). Preliminary experimental results for an optical fiber current sensor are presented. The sensor gave good results under various V ‫‪electrical current supply values, and responded in a linear fashion to an‬‬ ‫‪electrical curr‬‬ ‫‪applied electric current. The results proved that the optical fiber current‬‬ ‫‪sensors can be used in high voltage substations due to their superior‬‬ ‫.‪accuracy, bandwidth, dynamic range and inherent isolation‬‬