• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.55 no.1
• /
• pp.6-12
• /
• 2006

A popular method used by primary protection for power transformer is current ratio differential relaying (RDR) with 2nd harmonic restraints. In modern power transformer due to the use of low-loss amorphous material, the 2nd harmonic component during inrush is significantly reduced. The higher the capacitance of the high voltage status and underground distribution, the more the differential current includes the 2nd harmonic component during internal fault. Thus the conventional method may not operate properly. This paper proposes an advanced relaying algorithm and the prototype IED hardware design and it's real-time experimental results. To evaluate performance of the proposed algorithm, the study is well constructed power system model including power transformer utilizing the EMTP software and the testing is made through simulation of various cases. The proposed relaying that is well constructed using DSP chip and microprocessor etc. has been developed and the prototype IED has been verified through on-line testing. The results show that an advanced relaying based prototype IED never mis-operated and correctly identified all the faults and that inrushes that are applied.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.2
• /
• pp.122-130
• /
• 2012

Adhesive bend and shear tests of micro-sized bonded component have been performed to clarify the relationship between effects of heat-treatment on the adhesive strength and the bonded specimen shape using Weibull analysis. Multiple micro-sized SU-8 columns with four different diameters were fabricated on a Si substrate under the same fabrication condition. Heat-treatment can improve both of the adhesive bend and shear strength. The improvement rate of the adhesive shear strength is much larger than that of the adhesive bend strength, because the residual stress, which must change by heat-treatment, should effect more strongly on the shear loading. In case of bend type test, the adhesive bend strength in the smaller diameters (50 and $75\;{\mu}m$) widely vary, because the critical size of the natural defect (micro-crack) should vary more widely in the smaller diameters. In contrast, in case of shear type test, the adhesive shear strengths in each diameter of the columns little vary. This suggests that the size of the natural defects may not strongly influence on the adhesive shear strength. All the result suggests that both of the adhesive bend and shear strengths should be complicatedly affected by heat-treatment and the bonded columnar diameter.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.11 no.1
• /
• pp.74-78
• /
• 2015

Nuclear power plant steam generator that is one of the main component has several thousands of thin tubes. And the steam generator tube is subject to damage because of the severe operation conditions such as the high temperature and pressure. Therefore periodic inspections are conducted to ensure the integrity of steam generator component. Hanul unit 3 also has been inspected in accordance with in-service inspection program and is scheduled to be replaced for exceeding the plugging rate which was recommended by manufacturer. During the steam generator replacement activity, we found several clustered porosity on inner surface of main feed water pipe. Additionally crack-like indications were found at weld interface between base material and weld of main feed water pipe. This paper describes the field experience and visual testing results for inner surface of main feed water pipes. The destructive test result had shown that these indications were porosities which were caused by manufacturing process not by operation service.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.05a
• /
• pp.245-248
• /
• 2005

This paper is concerned with manufacturing technology of thin foil tensile specimen using CIP(Cold Isostatic Press) and measurement of precision mechanical property. This thin foil tensile specimen manufacturing technology is a method that can make a metal thin foil specimen for micro tensile testing. We can get a burr free micro metallic thin foil specimen using this technology. For testing mechanical property of this micro thin foil, we use a nano scale material testing machine that was developed by KITECH. In this paper, micro tensile specimens of nickel and copper thin foil are fabricated with CIP and precision mechanical properties of these materials could be measured. We will expect that precision mechanical property of micro/nano material and component. Micro and Nano mechanical property can be measured using this technology and mechanical property data base of micro/nano material and component can be constructed.

• Proceedings of the KIEE Conference
• /
• 2002.07b
• /
• pp.735-737
• /
• 2002

A current transformer for measuring current in high power testing laboratory is exactly proportional to the current including D.C component due to electrical transient. But, current transformer isn't designed to consider D.C component, therefore when data acquisition system measure that current. the error is increased because of saturation of core. This paper describe the concept of transient factor and how to design the current transformer.

• Journal of the Korean Data and Information Science Society
• /
• v.13 no.2
• /
• pp.87-95
• /
• 2002

In this paper we consider optimal designs of partially accelerated life testing which is devised for multi-component mixed systems with the considerably long lifetime. Test items are run at both use condition and accelerated condition until a specified censoring time. The optimal criterion for the sample-proportion allocated to accelerated condition is to minimize asymptotic variance of the maximum likelihood estimators of the acceleration factor and hazard rates.

• Proceedings of the Korean Information Science Society Conference
• /
• 2002.04b
• /
• pp.376-378
• /
• 2002

재사용이 가능한 컴포넌트들을 사용하는 컴포넌트 기반 소프트웨어 개발 기술은 현재 소프트웨어 개발의 핵심 기술로써, 많은 소프트웨어들이 이 기법을 이용해 개발되고 있다. 컴포넌트 기반 스프트웨어를 보다 효율적으로 시험하기 위한 많은 노력이 있었으나, 아직까지 자동으로 시험을 쉽게 수행해 주는 도구는 별로 없으며 이미 개발된 도구들도 그 효용성이 미약하다. 본 논문에서는, 이전에 제안했던 컴포넌트 기반 소프트웨어 자동화 시험 도구인 CTM(Component Testing Manager)의 확장 내용으로써 XMI(XML Metadata Interchange) 형식으로 표현된 UML(Unified Modeling Language) 모델로부터의 시험 데이터 생성 및 수행기법에 대해 제시한다. 본 기법은 기존의 UML모델을 이용한 다른 시험기법과는 달리 표준화된 XML를 사용함으로써 XML모델링 도구와 독립적이고 분산환경에서 쉽게 사용할 수 있는 장점을 제공하여 보다 쉽게 컴포넌트 기 반 소프트웨어 의 시험을 가능하게 해 준다

• Journal of the Korean Society for Nondestructive Testing
• /
• v.30 no.6
• /
• pp.564-568
• /
• 2010

When ultrasound propagates to a crack, transmitted and reflected waves are generated. These waves have useful information for the detection of the crack lying in a structure. When a crack is under residual stress, crack surfaces will contact each other and a closed crack is formed. For closed cracks, the fundamental component of the reflected and transmitted waves will be weak, and as such it is not easy to detect them. In this case, higher harmonic components will be useful. In this paper, nonlinear characteristic of a closed crack is modeled by a continuum material having a tensile-compressive unsymmetry, and the amplitude of the second harmonic wave was obtained by spectrum analysis. Variation of the second harmonic component depending on the nonlinearity of the inclusion was investigated. Two-dimensional plane strain model is considered, and finite element software ABAQUS/Explicit is used.

• Communications for Statistical Applications and Methods
• /
• v.12 no.1
• /
• pp.101-115
• /
• 2005

We propose in this article a procedure for testing unit and fractional orders of integration, with the roots simultaneously occurring in the trend, the seasonal and the cyclical component of the time series. The tests have standard null and local limit distributions. However, finite sample critical values are computed, and several Monte Carlo experiments conducted across the paper show that the rejection frequencies against unit (and fractional) orders of integration are relatively high in all cases. The tests are applied to the UK consumption and income series, the results showing the importance of the roots corresponding to the trend and the seasonal components and, though the unit roots are found to be fairly suitable models, we show that fractional processes (including one for the cyclical component) may also be plausible alternatives in some cases.

• The Korean Journal of Applied Statistics
• /
• v.17 no.3
• /
• pp.547-556
• /
• 2004

This paper consider the testing problem of variance component for the unbalanced two-way error component model with nuisance parameter. We derive the one-sided LM test statistic for testing zero individual(time) effects assuming that the other time-specific(individual) effects are present. Using the Monte Carlo experiments, the computational more demanding LR test slightly underestimates the nominal size and has the low powers relative to LM test statistic.