• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2411-2413
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• 1999

Regarding the application of diagnistic technology using PD signal to power apparatus, it is necessary to discriminate the type of defect as well as to determine whether the PD occurs or not. In this research, PD characteristics of multi-defects insulating system were presented, the PD signals were detected from three kinds of electrode systems, IEC(b), needle-plane and CIGRE method II. To make multi-defect systems artificially, we combined three electrode systems and applied same test voltage simultaneously.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.5
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• pp.320-325
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• 2015

This paper dealt with a defect identification algorithm which is based on single partial discharge (PD) pulse analysis in gas insulated structure. Four types of electrode systems such as a needle-plane, a plane-needle, a free particle and a crack inside spacer were fabricated to simulate defects in gas insulated switchgear (GIS). We measured single PD pulse by an oscilloscope with a sampling rate of 5 GS/s and a frequency bandwidth of 1 GHz. Data aquisition and signal processing were controlled by a LabVIEW program. Physical shapes of PD pulses were compared with kurtosis, skewness and time-based parameters as rising time, falling time and pulse-width. These parameters were analysed by an algorithm with a back propagation algorithm (BPA). By applying the algorithm, the identification rate was 97% for the needle-plane electrode, 96% for the plane-needle electrode, 91% for the free particle and 93% for the crack inside spacer. The results verified that the algorithm could identify the type of defects in GIS.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.4
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• pp.247-252
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• 1999

In this paper, in order to investigate availability of the OW-PD measurement method which has been proposed as an alternative of AC-PD measurement method to an after laying test and/or diagnosis for the power cable system, partial discharges owing to the needle-type defect integrated into the cable have been measured using AC and OW(Oscillating Wave) voltages. In the AC-PD measurement, the magnitude, phase and pulse number of partial discharges have been changed with the duration of voltage application, which can be analyzed through the relation with the process of the electrical tree initiation and propagation. In addition, the characteristics of partial discharges using OW voltage are appeared to be similar to those in case of AC-PD measurement and to be different with the shapes of electrical tree. From these results, it is concluded that the OW-PD measurement method is available to the tests for the cable system.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.970-972
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• 1998

In practice, there may be various defects in an insulating system, so that the PD signals can be produces from these defect simultaneously. Regarding these situations, we have to discriminate the type of defect as well as to determine whether the PD occurs or not. In our research. some analysis results of the PD signals from multi-defects insulating system will be presented. We measure the PD signals using three kind of electrode system: IEC(b). Needle-Plane and mixed electrodes. To simulate multi-defect systems, we combine two electrode systems and apply test voltage simultaneously. Neural network, statistical analysis methods will be tested, and the possibilities and limitations of each method will be clarified.

• Journal of Pharmacopuncture
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• v.25 no.4
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• pp.382-389
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• 2022

Objectives: The Korean Industrial Standard (KS) for sterile acupuncture needles was established in 2009 based on research on the quality control of acupuncture needles. We aimed to determine the quality of acupuncture needles available in South Korea in 2021 by examining their surface condition and chemical composition using field-emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS). Methods: In South Korea, there are 23 brands of acupuncture needles, and we examined 10-15 needles from each brand, resulting in a total of 285 needles. The microstructures of the needles were assessed by SEM. Using SEM images, we evaluated the acupuncture needle tips for the following defects/aspects: scratches, lumps, detached coating, bent tip, and tip sharpness. EDS was used to determine the chemical composition of the selected acupuncture needles. Results: Overall, 88.4% of 285 needles were found to have at least one type of abnormality. The most frequently observed abnormalities were scratches and dents on the surface (68.1%), followed by detached coating (63.2%), and lumps (61.8%); blunt tips were observed in about 24% of them. Of 252 needles with at least one defect, 86.9% had two or more types of defects. The ratio of the number of needles with any defect to that of needles without any defect varied among brands, ranging from 50% to 100%. Regarding foreign materials, higher proportions of Si and O were observed on the needles, indicating incomplete or detached silicone coating. Conclusion: The quality of acupuncture needles varied among brands, suggesting that further improvements can be made through various inspection methods.

• Journal of Electrical Engineering and information Science
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• v.3 no.2
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• pp.170-173
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• 1998

In practice, there may be various defects in an insulating system, so that the PD signals can be produced from these defects simultaneously. Regarding these situations, we have to discriminate the type of defect as well as determine whether the PD occurs or not. In this paper, some analysis results of the PD signals from multi-defects insulating system were presented. We measure the PD signals by using three kind of electrode system, IEC(b), Needle-Plane and mixed electrodes. To simulate multi-defect systems, we combined to electrode systems and apply test voltage simultaneously. Neural network, statistical analysis methods were tried, and the possibilities and limitations of each method were clarified.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1468-1473
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• 2013

This paper dealt with the propagation characteristics of acoustic signals produced by partial discharges and the positioning of PD origin in insulation oil to develop insulation diagnostic techniques of oil-immerged transformers. Electrode systems such as needle to plane, plane to plane, and particle electrodes were fabricated to simulate some defects of power transformers. In addition, the frequency spectrum and propagation characteristics of acoustic signals with partial discharge (PD) in insulation oil were analyzed. Although there were differences based on the type of defect, the frequency spectra of the acoustic signals measured by wide and narrow band acoustic emission (AE) sensors were distributed in the range of 50 kHz-400 kHz. Therefore, a narrowband AE sensor is suitable for the diagnosis of oil-immersed power transformers. We could find the position of the PD source with an error margin of 10% in the experiments by calculating the position of the PD occurrence using the time difference of arrival measured by five AE sensors.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.3
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• pp.45-50
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• 1998

This paper presents experimental results on the application of very low frequency(VLF) voltage to replace conventional DC test as an after laying test for underground distribution cables. We carried out several tests to prove defects detecting ability of VLF test on the 5m length real cables having knife-cut or needle type defects which is made in our La.. Through this experiment we proved it is very difficult to initiate electrical tree from the defects inside of the cable insulation but once the electrical tree is initiated it grows very fast and VLF does not make new defects and expand the defect. Therefore VLF test equipment for quality inspection test of manufacture is more effective than field application for underground distribution cables.