• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.2
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• pp.65-71
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• 2001

This paper describes partial discharge phenomenon with SF6gas pressures in insulation consisting of insulation paper and SF6 gas. We made the specimens with SF6 gas gaps which exist between aramid papers and electrodes and calculated the electric field intensity in the these gaps. We measured the partial discharge inception voltages and the AC breakdown voltages with the test method of IEC 60060-2 and did the partial discharge degradation experiments with a constant voltage. According to gas pressures, the breakdown voltages in SF6gas gaps were calculated by Paschen's law. And these results showed the ability applying partial discharge inception voltages evaluation to Paschen's law and the relationship between the PD quantities occurring insulation breakdown and PD occurring area.

• Journal of Electrical Engineering and Technology
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• v.2 no.3
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• pp.396-400
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• 2007

A novel technique has been proposed and related experimental works have been performed in order to detect the partial discharges and the location of the possible defects introduced into the Gas Insulated Switchgear. For this purpose, a prototype HY Pockels sensor has been developed and then employed in order to investigate its field applicability for finding the location of the defects using a 170kV GIS mock-up. Our proposed sensor enables us to measure the electric field variation due to the PD occurrence. In addition, the different PD patterns are observed, which might be dependant on the location and the distance of the sensor with respect to the PD source. Throughout this work, its linear response has been proved to be admissible as a function of the applied voltage. And also the position of the PD source might be distinguished by comparing the PD patterns.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2001.11a
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• pp.121-126
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• 2001

In this paper, for n = 2m and odd prime p, new generalized bent functions from the finite field F$\_$p$^n$/ to the prime field F$\_$p/ are constructed from the partial spreads for F$\_$p$^n$/. Closed form expressions for the proposed generalized bent functions and their trace transform are derived in the form of the trace functions. The trace expressions for the bent functions and their trace transforms defined on F(equation omitted) constructed by using PS- are also derived.

• Proceedings of the KIEE Conference
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• 2008.09a
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• pp.224-226
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• 2008

In this paper, we developed HPF (high pass filter) consisted of lumped LC components to decrease the noises that are detected in PD (partial discharge) measuring test, and adapted it to field test.

• Bulletin of the Korean Mathematical Society
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• v.49 no.4
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• pp.875-883
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• 2012

Let $\mathbb{F}_q$ be a finite field with q elements and $\mathbb{F}_q((X^{-1}))$ be the field of all formal Laurent series with coefficients lying in $\mathbb{F}_q$. This paper concerns with the size of the set of points $x{\in}\mathbb{F}_q((X^{-1}))$ with their partial quotients $A_n(x)$ both lying in a given subset $\mathbb{B}$ of polynomials in $\mathbb{F}_q[X]$ ($\mathbb{F}_q[X]$ denotes the ring of polynomials with coefficients in $\mathbb{F}_q$) and deg $A_n(x)$ tends to infinity at least with some given speed. Write $E_{\mathbb{B}}=\{x:A_n(x){\in}\mathbb{B},\;deg\;A_n(x){\rightarrow}{\infty}\;as\;n{\rightarrow}{\infty}\}$. It was shown in [8] that the Hausdorff dimension of $E_{\mathbb{B}}$ is inf{$s:{\sum}_{b{\in}\mathbb{B}}(q^{-2\;deg\;b})^s$ < ${\infty}$}. In this note, we will show that the above result is sharp. Moreover, we also attempt to give conditions under which the above dimensional formula still valid if we require the given speed of deg $A_n(x)$ tends to infinity.

• Journal of Advanced Marine Engineering and Technology
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• v.12 no.1
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• pp.53-61
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• 1988

Most of the recent for the flow field hydrofoil in partially cavitating condition are the ones which are linearized, and the problem of cavity end region for hydrofoil is not verified. This paper deals with a study on characteristics of end region flow field for partially cavitating hydrofoil by using a characteristics of shear turbulence flow and nonlinear cavity flow theory. The results obtained as follows : 1) Shear layer thickness is decreased gradually going to the end section of hydrofoil. When attack angle is large, it is appeared largely at the region of partial cavitation after its collapsing. 2) The fluctuation velocity of a second-degree relative direction have minimum value at the front of hydrofoil or at the end of hydrofoil. The difference for the validity of attack angle is appeared largely at the surrounding of .chi.$_{e}$ point. 3) The fluctuation velocity of transverse direction decrease from the maximum thickness of cavitation to the end of hydrofoil, but it undergoes largely the effect of pressure recovery. The difference is larger at the region of partial cavitation after its collapsing than at the of hydrofoil. 4) The distribution of Reynolds stress have maximum values at the region of partial cavitation after its collapsing and the end of foil, and the larger attack angle, the larger the distribution of value.e.

• Journal of Electrical Engineering and Technology
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• v.7 no.6
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• pp.977-982
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• 2012

In order to find out partial discharge (PD) phenomena in the cable joint due to the poor workmanship during the installation, the relationship between PD inception voltages and joint defects was investigated. For the purpose, in the joint of 22.9kV CNCV cables, electric fields were calculated for various semiconductive layer wrong positioning (WP) defects. And, PDIV were investigated through the experiments and compared with the results of electric field analysis. In all WP defect cases, the PD inception field calculated using measured PDIVs was similarly shown to be the average value of 1.84kV/mm. In addition, the calculated PDIV and the measured PDIV were almost equal, from the PDIV calculation using maximum electric fields and the measured PDIV for the normal case. Throughout this study, it is possible to analyze WP defects due to the poor workmanship and to establish better joint design for the distribution grade extruded cable system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.27-27
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• 2010

The exact partial discharge pulse should be measured in order to estimate the discharge source in the solid insulation and diagnose the degree of deterioration. Partial discharges generated in the insulation occur in the internal voids or at the edge of the insulation, have unique characteristics following the type and location. When external voltage is applied, Partial discharges occurred in the restrictively presented voids increase the quantity of electrical charge at the discharge onset voltage. The discharge characteristics have remained constant as space is filled by the impurity such as a compound of gases accompanied with discharge. In this study, How to design the insulation about the problems of the built-in diagnostics in the transformer is discussed by the interpretation of electric field.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1171-1174
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• 2004

Leakage current of the polymer arrester(42kV, 10kA, Class3) for railroad line applied actually field was observed and electrical characteristics of arrester before and after applied actually field were investigated. During applied actually field, leakage current of arresters were $610{\sim}647{\mu}A$ in AN SAN line and $500{\mu}A$ in YUNG DONG line. After applied actually field, electrical characteristics of arrester, such as insulation test, reference voltage test, leakage current test and partial discharge current test, wasn't variation as before applied actually field.

• Journal of Mechanical Science and Technology
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• v.20 no.10
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• pp.1691-1701
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• 2006

The scan type magnetic camera is proposed to improve the limited spatial resolution due to the size of the packaged magnetic sensor. An image of the scan type magnetic camera, ${\partial}B/{\partial}x$ image, is useful for extracting the crack information of a specimen under a large inclined mag netic field distribution due to the poles of magnetizer. The ${\partial}B/{\partial}x$ images of the cracks of different shapes and sizes are calculated by using the improved dipole model proposed in this paper. The improved dipole model uses small divided dipole models, the rotation and relocation of each dipole model and the principle of superposition. Also for a low carbon steel specimen, the experimental results of nondestructive testing obtained by using multiple cracks are compared with the modeling results to verify the effectiveness of ${\partial}B/{\partial}x$ modeling. The improved dipole model can be used to simulate the LMF and ${\partial}B/{\partial}x$ image of a specimen with complex cracks, and to evaluate the cracks quantitatively using magnetic flux leakage testing.