• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.1
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• pp.15-19
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• 2004

In this paper, we present the fabrication and characteristic analysis of Sagnac interferometric optical fiber senior(OFS) system for detecting pulsed ultrasonic signal in underwater. The hollow cylindrical mandrel wound round by single mode optical fiber is used as sensing component. The ultrasonic signal source is simulated by the PZT actuator operated by an function generator. The distance dependency of the OFS's sensitivity was measured. The sensitivity has been shown to be inversely propotional to the square-root of distance between ultrasonic source and sensing component. It has also been shown that the OFS could detect the signals less affected by ultrasonic path comparing to conventional acousto-electric sensor. and accurate location of ultrasonic signal could be carried out using two OFSs.

• Journal of the Korean Society of Safety
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• v.33 no.2
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• pp.21-27
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• 2018

The expansion and stable operation of electric power facilities are important factors with development of industrial facilities in modern society. In high-voltage equipment such as GIS, the insulation characteristics may be deterioated by environment-friendly gas adaption and miniaturization. There is also the possibility of accidents due to insulation breakdown due to the deterioration of power facilities. Therefore, it is necessary to extend the diagnosis system to continuously monitor the danger signals of these power equipment and to prevent accidents. Most of the internal defects in the GIS system are conductive particles, floating electrode defects, protrusion defects, and the like. In this case, a partial discharge phenomenon is accompanied. These partial discharge signals occur irregularly and various noise signals are included in the field, so it is difficult to evaluate the reliability in the development of the diagnostic system. In this paper, a study was made on equipment capable of generating a partial discharge simulated signal that can be adjusted in size and frequency to be applied to a diagnostic device by electromagnetic wave detection method. The PD simulated pulse generator consists of a user interface module, a high-voltage charging module, a pulse forming circuit, a voltage sensor and an embedded controller. In order to simulate the partial discharge phenomenon similar to the actual GIS, a discharge cell was designed and fabricated. The application of the prototype pulse generator to the commercialized PD diagnosis module confirmed that it can be used to evaluate the performance of the diagnostic device. It can be used for the development of GIS diagnosis system and performance verification for reliability evaluation.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.1
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• pp.44-51
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• 2000

In this paper, using a wide-band AE sensor with the frequency range from 100[kHz] to 1.5[kHz], the frequency spectra of AE signals generated from the corona discharges of the needle-plane gap and from the partial discharges of an epoxy void were analyzed to determine the proper ultrasonic sensor with optimum frequency range according to the patterns of corona discharges. We also examined the propagation characteristics of AE signals in oil and the relationship between the magnitude of corona discharge and the magnitude of AE signals in peak-to-peak value under the application of 60[Hz] ac high-voltage. From these results, the main frequency spectra of AE signals emitted from the corona discharges of the needle-plane gap were about 130[kHz] by the fast fourier transform, but the main frequency spectra appeared to be 230[kHz] in the partial discharges of an epoxy void. The magnitude of AE signals was proportional to the magnitude of corona discharge and discharge current pulse with increasing the applied voltages.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1183-1186
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• 2004

Degradation and insulation failure of traction motor depend on the continuous stress imposed on it. And knowing on insulation condition is important thing for safety operation of EMU(electric multiple unit). In this paper, PD(partial discharge) characteristics for degradation analysis of stator coil is studied. For PD data acquisition, two models are made; one is normal condition coil, the other is aged condition coil. And PD data for discrimination were acquired from PD detector. And these data making use of a computer-aided discharge analyser, statistical and other discharge parameters is calculated to discrimination between different discharge sources. And also these parameter is applied to classify PD sources by neural networks. Neural Networks has good recognition rate for degradation of stator coil.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.4
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• pp.35-40
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• 2012

In this study, the ultraviolet (UV) intensity of polymer insulator was measured using the Anti-Reflective (AR) coating lens on the occurrence of corona discharge. The UV intensity was compared before and after the AR coating. Under the 200-260[nm] of UV lens, the reflection rate before AR coating was 7.5~5.5[%] with 85-89[%] of transmission rate. After AR coating, however, the reflection rate decreased to 1.3~1.22[%] with improved transmission (97.4~97.6[%]). Then, the UV intensity by distance was measured in the polymer insulator. According to the measurement, the UV intensity increased 6.5 times at 37.5[%] of Vm/Vbd with 5[m] of distance. As distance increased, the growth rate declined. As high voltage increased, in addition, AR coating was less effective due to the count error caused by the UV sensor pulse signal overlap. Therefore, it appears that it would be more effective to detect corona discharge with 5[m] or less of distance at diagnosis of power facilities by AR coating and UV sensor sensitivity.

• The Journal of Information Technology
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• v.7 no.3
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• pp.113-118
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• 2004

Recently, diagnosis techniques have been investigated to detect a partial discharge associated with a dielectric material defect in a high voltage electrical apparatus. However, the properties of detection technique of PD aren't completely understood because the physical process of PD. Therefore, this paper analyzes the process on Surface Discharge of Polymer Insulator using Wavelet transform. Wavelet transform provides a direct quantitative measure of spectral content in the time frequency domain. As it is important to develop a non-contact method for detecting the Contamination Degree, this research analyzes the electromagnetic waves emitted from PD using Wavelet transform. This result experimentally shows the process of PD as a two-dimensional distribution in the time-frequency domain. The method is shown to be useful for detecting prediction of contamination degree.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.10
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• pp.485-491
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• 2006

This paper describes that the distribution of electromagnetic field occurred by PD(Partial Discharge) pulse was calculated with simulation program and characteristics of calibration and PD pulses measured with folded dipole types sensors were analyzed. As the distribution of electromagnetic field in simulation was very random the wide band measuring methods were good. Therefore three folded dipole antenna types sensors which had different their widths were designed and made. The signal according to direction and distance between sensor and pulse source in these sensor was measured and the spectrum of surface PD were acquired in the experiment of model transformer. In this result the characteristics of sensor which had middle width was better than others and the main spectrum of PD signals in surface discharge were existed in around 220MHz, 320MHz and from 450MHz to 750MHz.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1954-1956
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• 2000

In this paper, when void of XLPE was existed, electrical tree was growth in branch-type, and it was growth in bush-type when void of XLPE was not existed. Moreover, charge magnitude of partial discharge by deterioration time of XLPE sample was about proportion to output voltage of AE signals. When void was existed, charge magnitude of partial discharge, the output voltage Vp-p value of AE signals were increased with increasing deterioration time. However, when void were not existed, charge magnitude of partial discharge, the output voltage Vp-p value of AE signals were increased in fast deterioration time, but it were decreasing at after in middle deterioration time. Frequency spectrum response of AE signal was about 100-250[kHz].

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1975-1977
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• 2000

In this study, a relationship between AC discharge progress and the radiated electromagnetic waves were investigated by measuring electromagnetic waves using a biconical antenna and a spectrum analyzer. The characteristics of frequency spectrum of the radiated electromagnetic waves was measured at the atmospheric pressure in liquid nitrogen($LN_2$) during partial discharges progress in nonuniform electric field depend on AC power supply. From this results, it was confirmed that when partial discharge was produced in liquid nitrogen, the signal of partial discharge was detected by frequency spectrum of the radiated electromagnetic waves. It is considered that these results obtained from this investigation may be used as fundamental data for diagnosis and prediction of insulation on superconducting and cryogenic power equipments.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.805-810
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• 2011

This paper deals with the method and algorithm used to find fault locations in gas insulated transmission line. The method uses UHF sensors and digital oscilloscope to detect discharge signals emitted to the outside through insulating spacer in the event of breakdown inside GIL. UHF sensors are the external type and installed at outside of insulating spacers of GIL. And we used wavelet signal processing to analyze the discharge signals and confirm the exact fault location findings in the GIL test line. This method can overcome demerit of TDR(Time Domain Reflectometer) method having been applied to detect fault location for conventional underground transmission lines, and Ground Fault Sensors used in conventional GIS systems. TDR method requires high level of specialty and experience in analyzing the measured signals. Ground fault sensors are installed inside GIL and can be destroyed by high transient voltage. This paper's method can simplify the fault location process and minimize the damage of sensors. In addition, this method can estimate the fault location only by the time difference when discharge signals are arrived to detecting sensors at the ends of GIL sections without reasons of breakdown. To test the performance of our method, we installed sensors at the ends of test line of GIL(84m) and sensed discharge signals occurred in GIL, energized with AC voltage generator up to 700kV.