Opto-electronic current transformer for Intelligent (HVAC) Networks / Ramy Ramadan Mostafa Elbashar ; Supervised Yehia Abdelhamed Badr , Rabah Yosef Amer , Jala Mahmoud Elazab

Thesis (M.Sc.) - Cairo University - National Institute of Laser Enhanced Science - Department of Laser Application in Engineering

Nowadays, Optical current sensing becomes an opponent to conventional current transformer in measuring high current in high voltage systems. Since it provides more advantages such as its safe operation, immunity to electromagnetic interference, low power consumption, suitable to measure DC and AC currents, no needing for insulation, and low installation cost. Thus, it is relevant for current monitoring in the new generation of intelligent grids. Most of optical current sensors are based on Faraday Effect where the linear polarized light rotates when passing through magneto-optic materials parallel to magnetic flux lines. The intensity of the magnetic field affecting the polarized light corresponds to the conductor current value. The sensitivity of the sensor is directly proportional to the length of the material subjected to the magnetic field. A smaller glass sensor may be used while compensating the reduced sensor length using a concentrator magnetic core to increase the magnetic field. In this work, an optical current transformer system with different polarimetric schemes is evaluated by using different lengths of magneto-optic glass SF-59 into an air gapped iron core of a conventional current transformer. To prevent reflection induce birefringence and improve the integration of the glass sensor to the fiber optics, an innovative design of a small hollow along the air gapped iron core is presented. The uniformity of magnetic field distribution along the cross section area of the air gap and along the gap optical path are maintained and verified experimentally. The experimental setup is composed of a He-Ne laser source of 5 mW at 632.8 nm, a toroidal concentrator with air gap 15.2 mm and some optical components. The maximum AC current measured is nearly 2800 AT while referring to the line frequency; far away from the core saturation, with maximum and r.m.s error of 1 % and 0.47 %, respectively, using a dual quadrature scheme. The maximum current measured has been limited by the maximum output of Variac

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