• Journal of the Korean Institute of Telematics and Electronics
• /
• v.22 no.3
• /
• pp.43-47
• /
• 1985

This paper describes fiber-optic current sensor using SF-4 flint glass for the first time, ails the flint glass has been theoretically analyzed by jones matrix and experimentally verified. Verdet constant of SF-4 flint glass, which determines the sensitivity of current sensor, has been experimentally found as 0.0606(min/g.cm). It is relatively lower value than currently used faraday rotators such as FR-5, SF-6 flint glasses and YIG. The fiber.optic current sensor system was established and the current measurement was performed in the range of 100-600 (A) and 100- 500 (G). It has beenfhown by the experi-mental results that the detector output linearly increased in proportion to the current. Since these experimental results were in good agreement with theoretical results, it has been shown that SF-4 flint glass can be used for the magnetooptic current sensor.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.22 no.1
• /
• pp.73-78
• /
• 2008

A polarimetric fiber-optic CT has been developed by using a sensing coil made of a length of sun fiber. A Faraday rotator mirror is attached to the end of the sensor coil to double the sensitivity and to suppress the residual linear birefringence effect. From the current measurements, the linear error no more than ${\pm}2[%]$ was obtained. The output of spun fiber sensor coil was compared with those of the twisted- and the flint glass fiber's, and it fumed out to almost 50 times, 2 times more sensitive, respectively.

• Journal of the Optical Society of Korea
• /
• v.14 no.3
• /
• pp.240-244
• /
• 2010

In this work, we used PWM sampling for demodulation of a fiber-optic interferometric current transformer. The interference signal from a fiber-optic CT is sampled with PWM triggers that produce a 90-degree phase difference between two consecutively sampled signals. The current-induced phase is extracted by applying an arctangent demodulation and a phase unwrapping algorithm to the sampled signals. From experiments using the proposed demodulation, we obtained phase measurement accuracy and a linearity error, in AC current measurements, of ~2.35 mrad and 0.18%, respectively. The accuracy of the proposed method was compared with that of a lock-in amplifier demodulation, which showed only 0.36% difference. To compare the birefringence effects of different fiber-optic sensor coils, a flint glass fiber and a standard single-mode fiber were used under the same conditions. The flint glass fiber coil with a Faraday rotator mirror showed the best performance. Because of the simple hardware structure and signal processing, the proposed demodulation would be suitable for low-cost over-current monitoring in high voltage power systems.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.18 no.4
• /
• pp.28-33
• /
• 2004

We developed a fiber-optic CT for large current monitoring in power systems. We used a FRG fiber sensor coil to suppress CT output degradation caused by linear birefringence, and different optical sources were used to compare their noise characteristics. From the experiments, we obtained output variation less than $\pm$0.4(%) when the sensor coil suffered mechanical perturbations, and the ASE source showed -23(㏈) less noise in the output than singlemode laser diode.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2008.05a
• /
• pp.74-77
• /
• 2008

We improved an efficiency of fiber-optic current transformer by using a metal-coated sensor coil. To reduce the linear birefringence, we used a length of spun fiber as sensor coil, and then used a flint glass fiber coil for comparison. To make the sensor coil in the reflection type, we used different reflection mirrors at the end of the sensor coil, such as a Faraday rotator mirror, a simple mirror, a metal-coated fiber end and a simple fiber end. From the experimental results, the linear error of current measurements were less than ${\sim}$ 0.2 % regardless of the mirror types. The metal-coated sensor was the most cost-effective considering the fabrication cost and the simple structure.