• 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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• 1991.07a
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• pp.314-317
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• 1991

The waveforms of high voltage and current pulse were measured using laser measuring systems. Existing potential transformer and current transformer have low measuring precision because of resonance phenomena and waveform distortion due to the magnetic saturation. But using laser measurement, it is possible to obtain clear waveforms which have no effect of distortion and harmonic resonances. And electromagnetic interferences (EMI) in the measuring of high voltage and current pulse, but the optical measuring systems are not subjet to the influence of EMI. Using laser measuring systems based upon Pockels effect and Faraday effect is not free from any errors yet, but it could replace existing measuring systems by routine experiments and error corrections. And it needs that more research and development of optical crystals and equipments would be taken.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.328-329
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• 2003

최근 전력 계통의 전압 상승과 측정 정밀도에 대한 요구가 증대됨에 따라 전력 설비의 고장 검출이나 측정 분야의 기술과 비용면에서 경쟁력을 갖춘 광을 이용한 고전압 대전류 측정이 주목받고 있다. 본 연구는 광섬유를 이용하여 보다 안전하고 정밀한 대전류 측정 장치 개발에 목적을 두고 있다. 광을 이용한 전류 센서는 편광된 광이 광섬유를 통과할 때 광섬유 주위의 자장에 의해서 편광면이 회전하는 패러데이 회전을 이용한 것이다. (중략)

• 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.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.418-421
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• 2006

현재 국내 외에서 GIS(Gas Insulated Switchgear)용 광 CT(optical current transformer)가 활발히 연구 개발되고 있다. 이러한 광 CT는 전력선에 발생하는 자기장에 의해 레이저 빛의 파장 각도가 변하는 현상인 Faraday Effect를 기련 원리로 한 전류측정용 기기이다. 본 논문에서는 GIS용 광 CT 개발을 목적으로 한 기초적 연구로써 자기장이 발생하는 전력선에 장착되는 센서부가 도선을 중심으로 해서 어떻게 위치하느냐에 따른 광 CT의 출력신호를 측정하여 연구하였다.

• Journal of the Optical Society of Korea
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• v.14 no.3
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• pp.240-244
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• 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
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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 Power Electronics
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• v.15 no.5
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• pp.1402-1408
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• 2015

A MOSFET's gate driver based on magnetic coupling is investigated. The gate driver can meet the demands in applications for wide range of duty cycles and high frequency. Fully galvanic isolation can be realized, and no auxiliary supply is needed. The driver is insensitive to the leakage inductor of the isolated transformer. No gate resistor is needed to damp the oscillation, and thus the peak output current of the gate driver can be improved. Design of the driving transformer can also be made more flexible, which helps to improve the isolation voltage between the power stage and the control electronics, and aids to enhance the electromagnetic compatibility. The driver's operation principle is analyzed, and the design method for its key parameters is presented. The performance analysis is validated via experiment. The disadvantages of the traditional magnetic coupling and optical coupling have been conquered through the investigated circuit.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1978-1980
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• 2003

본 논문에서는 광을 이용한 전류 측정 장치의 연구 내용에 대하여 기술하였다. 광을 이용한 전류 측정 장치의 가장 큰 문제점은 감도 저하를 주는 선형 복굴절 양이며, 이러한 선형 복굴절을 줄이는 방법은 광섬유를 비틀어서 선형 복굴절 양에 비해 원형 복굴절의 양을 크게 해주는 방법을 사용하였다. 광섬유를 비틀어서 측정한 결과는 측정 감도가 약 3배의 증가를 보였으며, 측정오차의 경우도 1 % 이내의 선형성을 나타내었다. 본 실험의 결과로 광섬유를 비트는 방법이 광을 이용한 전류 측정 장치의 선형 복굴절을 크게 감소시킴을 알 수 있었으며, 대전류 측정에 측정도를 높일 수 있다고 판단된다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.4
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• pp.50-56
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• 2003

It is well known that a partial-discharge(PD) in insulation oil is the source of various physical and chemical phenomena, such as heat, light, gas, chemical transformation, electric current, electromagnetic radiation and ultrasonics. The PD can be detected by measuring one of these changes. Although some techniques are employed in this purpose, several obstacles interfere with an on-line measurement. Ultrasonic-wave detection is a useful method for the diagnosis of the transformer-insulation condition. Conventionally, ulyrasonic waves are detected by Piezo-electric transducer, but we use optical method that has many advantages. In this paper, we constructed a Mach-Zehnder interferometer with optical fiber and investigated the principle of operation. Test arrangement is based on the needle-plane electrode system in oil and applied AC high voltage. Ultrasonic waves were detected and analyzed with wavelet transform.