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Proceedings Paper

General review of optical current sensors
Author(s): Z. P. Wang; Yanong N. Ning; Andrew W. Palmer; Kenneth T. V. Grattan
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Paper Abstract

In recent years, a considerable research effort has been expended on the field of optical current measurement in order to replace the conventional curient transformer (CT) used in power distribution 1 Although current measurement schemes based upon the use of an optical fibre as the sensing element were proposed as early as 1976, and a number of new methods which employ optical fibre, or bulk glass, or even electro-optic hybrid sensing elements have been explored and aviable commercial product has not yet emerged, despite the considerable level of research that has been devoted to the concept. An opticai current sensor consists of an optical current sensing element which measures the integral of the magnetic field along a closed (or nearly closed) optical loop around the current to be measured, an optical fibre link which connects the sensing element to an opto-eletronic control/processing unit, used to launch a light beam into the optical fibre and detect/demodulate the modulated optical signal collected from the fibre. According to the sensing mechanism employed and the sensing materials used, the optical current measurement devices may be categorized into three main groups: (i) optical current sensors (OCS) employing optical fibre as their sensing elements, (ii) the OCS type using bulk glass to sense the current, and (iii) the OCS type using electro-optic hybrid devices. In general, the principle ofthe operation ofthe first two types of sensors is based upon the so-called "Faraday magneto-optic effect", in which the polarization azimuth, 1F' a linearly polarized light beam propagating inside an optical material is rotated under the influence of a magnetic field, H, generated by the electrical current to be measured and is given by (Formula available in paper) (1) where V is the Verdet constant ofthe fibre core and 1 is the interaction length. Ifthe medium is subject to the magnetic field within a long solenoid this then becomes (Formula available in paper) (2) where N1 and NC the number of passes of the light through the solenoid and the number of turns of wire in the solenoid respectively, and I is the electric current. The electro-optic hybrid current sensors are often constructed from a conventional current Iransfonner interrogated with different electro-optic or fibre optic sensing schemes. Among these groups ofsensor, optical fibre current sensors have been discussed and reviewed by a number of scientists 1 3. Hence, in this paper, we will summarize the possible solutions for dealing with the stability problems associated with bendinduced linear birefringence in optical fibre current sensors and review the recent development in the area of current measurement using optic bulk glasses and electro-optic hybrid sensing techniques.

Paper Details

Date Published: 5 August 1994
PDF: 4 pages
Proc. SPIE 2321, Second International Conference on Optoelectronic Science and Engineering '94, (5 August 1994); doi: 10.1117/12.182157
Show Author Affiliations
Z. P. Wang, City Univ. (United Kingdom)
Yanong N. Ning, City Univ. (United Kingdom)
Andrew W. Palmer, City Univ. (United Kingdom)
Kenneth T. V. Grattan, City Univ. (United Kingdom)


Published in SPIE Proceedings Vol. 2321:
Second International Conference on Optoelectronic Science and Engineering '94
Wang Da-Heng; Anna Consortini; James B. Breckinridge, Editor(s)

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