• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1658-1660
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• 2004

Use of higher voltage and higher capacity of power systems and their equipment is leading to an increase in the size of the entire system. In order to reduce the cost of constructing a substation, it is necessary to reduce the size of equipment. So, this paper described optical sensor, which exploited the electric and magnetic potentiometer to sense the measured voltage and current of medium voltage GIS. It can be used both in measurement and in protection relays as its well linearity, rapid response, broad dynamic range, wide frequency band, no magnetic saturation, small in volume, light weight, and saft in insulation.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.2
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• pp.55-62
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• 2005

The optical CT was developed to use twisted fibers for 170 kV GIS. The fiber sensor optimized on the optical CT was wound 3 turns and twisted 4 times per a turn at the pipe with a diameter of 130 mm. The measurement error for the linearity which was satisfied the criterion of 'IEC Class-1.0' was less than ± 0.44 % at the transmission type and ± 0.82 % at the reflection type to 2,000 A. At a low current to 200 A, the measurement error was ± 0.69% at the transmission type and ± 1.38 % at the reflection type.

• Current Optics and Photonics
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• v.7 no.1
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• pp.21-27
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• 2023

A highly sensitive optical-fiber humidity sensor is demonstrated in this paper. By using Nafion-PVA sol-gel and single-mode optical fibers, the Fabry-Perot humidity sensor is easily fabricated. In the humidity range of 29%-72%, humidity-response experiments are carried out with a cycle of rising and falling humidity to investigate humidity-response characteristics. The experimental results show 2.25 nm/%RH sensitivity and a 0.9997 linear correlation coefficient, with good consistency. The changes in optical-path difference (OPD) and free spectral range (FSR) with humidity are also discussed. The humidity sensitivities of a typical sensor are 80.3 nm/%RH (OPD) and 0.03 nm/%RH (FSR). Furthermore, many humidity sensors with different Nafion-PVA sol-gel concentration and initial cavity length are experimentally investigated for humidity response. The results show that the sensitivity increases with higher Nafion ratio of the Nafion-PVA sol-gel. The influence of changing cavity length on sensitivity is not obvious. These results are helpful to research on optical-fiber humidity sensors with good performance, easy fabrication, and low cost.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1823-1825
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• 2007

Based on Faraday effect, the variation of current flowing through the conductor can be encoded as that of azimuth angle of light polarization propagating through the fiber coil wound onto the conductor. The amount of current can be obtained by measuring the variation of the light intensity transformed from that of the azimuth angle through a polarization analyzer. In this paper we propose a fiber-optic current sensor system that employs a fiber polarization analyzer as a sensor interrogation device. The fiber polarization analyzer was prepared by inscribing a long-period fiber grating on a high birefringent fiber. At the fixed wavelength of 1522.5 nm, the fabricated fiber device has the polarization extinction ratio of more than 25 dB. The measurement of large current up to 600 Arms was accomplished based on a simple fiber interrogation device and the measurement output of the sensor system showed a good linearity.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.5
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• pp.542-548
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• 2001

A robust, accurate, broad-band, alternating current sensor using fiber-optics is being developed as a part of optical over current protection relay system. The sensor uses the Faraday effect in optical fiber and polarimetric measurements tc sense electrical current. The current sensing coil consists of a length of twisted optical fiber and Faraday rotator mirror to suppress the linear birefringence effect. Due to its single-ended closed path structure, it can not only be easily installed to the target with great isolation from other fields in the vicinity, but the sensitivity can be increased by using multiple turns. This paper reports on the theoretical backgrounds of the sensor design and the preliminary experimental results.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1846-1849
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• 1998

An optical magnetic filed sensor, YIG (Yittrium Iron Garnet), response rapidly, to the power-line currents to be measured. In response to Faraday effect, it shows wide-and-linear measurable range. This paper reports the development and implementation of an OOCR (Optoelectric OverCurrent Relay) using this sensor. This relay is free from environmental electro-magnetic noises and has excellent insulation characteristics inherently. By using this OOCR, we can reduce insulation cost of protective relaying systems and its maintenance cost, and can achieve high reliability of the system.

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.270-274
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• 2020

In this study, a read-out integrated circuit (ROIC) that can be applied to a colorimetry-based optical sensor for analyzing total phosphorus and total nitrogen was developed and characterized. The proposed ROIC minimizes the effect on temperature fluctuation, improves sensitivity, and extends the dynamic range by utilizing a dual optical path and feedback control circuit. Using a dual optical path makes it possible to calibrate the output signal of the optical sensor automatically, along with the temperature fluctuation. The calibrated voltage is fed back into the measurement stage; thus, the output current of the measurement is adaptively controlled. As a result, the sensitivity and dynamic range of the proposed ROIC are improved. Finally, a total-phosphorus analysis was conducted by utilizing the ROIC. The ROIC was found to operate stably over a wide temperature range.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.41-44
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• 2003

We propose portable equipment that monitors current and voltage of high-potential power transmission lines. In the equipment, a current and voltage sensor are attached to an insulator that supports a power transmission line: A clamped to the power line and the detected current signal is transmitted to the ground station by a wireless optical link using transmission line is detected by a high resistance element, zinc oxide (ZnO). That acts as a potential divider between the power line and ground. We make an experimental device for 66kV power line and demonstrate that it can monitor currents proposed equipment is small-sized, light, and inexpensive in comparison with the conventional CT (current transformer) and PT (potential transformer) since it does not require high potential insulators and magnetic cores, further, the equipment is easily installed owing to its small size and its simple structure.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.4
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• pp.80-87
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• 2007

This paper will suggest that the 1 cross orthogonal loop type sensor improves on the orthogonal loop form sensor-head, which is available a calibration of the linear birefringence, when a fiber optic current sensor was composed. An output characteristics of the 1 cross orthogonal loop form, a general closed loop form, the orthogonal loop form are compared by the IEC(International Electrotechnical Commission) 60044-8 standard, and the state of polarization is compared with three forms. As a result, when the closed loop form was changed to the orthogonal loop form, retardation decreased 15.3[%]. When the closed loop form was changed to the 1 cross orthogonal loop type, the retardation decreased 33.8[%]. As a result of the Faraday Effect measurement, the 1 cross orthogonal loop form has the highest output characteristic and the lowest error ratio. It met the 0.5 class of the IEC 60044-8 standard. Thus, in application of the 1cross orthogonal loop form, the possibility to develop high reliability fiber optic current sensors that have a high output and stable error ratio rises is increased.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.5
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• pp.17-23
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• 2017

Optical current sensors are suitable for operation in high voltage and high current environments such as power plants due to they are not affected by electromagnetic interference and have excellent insulation characteristics. However, as they operate in a harsh environment such as large temperature fluctuation and mechanical vibration, high reliability of the sensor is required. Therefore, many groups have been working on enhancing the reliability. In this work, an integrated optical current sensor incorporating polarization-rotated reflection interferometer is proposed. By integrating various optical components on a single chip, the sensor exhibits enhanced stability as well as the solution for low-cost optical sensors. Using this, we performed the characterization for the actual field application. By using a large power source, the current of 0.3 kA~36 kA was applied to the photosensor and the linear operation characteristics were observed. The error of the sensor was within $0{\pm}.5%$. Even when operating for a long time, the error range of the sensor was kept within $0{\pm}.5%$. In addition, the measurement of the frequency response over the range of 60 Hz to 10 kHz has confirmed that the 3-dB frequency band of the proposed OCT is well over 10 kHz.