• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2004년도 추계학술대회 논문집
• /
• pp.96-100
• /
• 2004

This paper deals with power quality disturbance generator with phase jump function. The proposed generator can be applied to the performance test of custom power devices. Voltage sag, swell, outage, unbalance and phase jump after outage are provided by the generator. The phase jump operating principle of the generator is described and analysed. The control scheme of the disturbance generator is simple and hardware setup is cost effective compared with the conventional scheme. The usefulness of the generator is verified through simulation and experimental results.

• International Journal of Precision Engineering and Manufacturing
• /
• 제9권4호
• /
• pp.63-65
• /
• 2008

The increased interest in reducing the environmental effects caused by releasing organic compounds and aqueous waste has motivated the development of polymeric materials in supercritical fluids. Recently, supercritical fluids have been used in material synthesis and processing because of their special properties, such as high diffusivity, low viscosity, and low surface tension. Supercritical carbon dioxide is the most attractive because it is non-toxic, non-flammable, and has moderate critical temperature and critical pressure values. Supercritical carbon dioxide can also swell most polymers. In this study, we prepared polymer/clay nanocomposites using supercritical fluids. Cloisites 10A, 15A, 25A, and 30B used in this study are montmorillonites modified with a quaternary ammonium salt. The nanocomposites of polymer/clay were characterized by X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1997년도 추계학술발표회논문집(1)
• /
• pp.401-406
• /
• 1997

발전소 기동 및 저출력 운전시 원자력발전소(PWR) 터빈운전원(T/O)들은 증기발생기 수위제어를 위해 배전반(MCR)에 증기발생기 수위제어 관련 경험이 있는 운전원 3명 이상이 좁은 보드앞에서 각자 S/G A, B, C의 주요 파라미터들을 감시하며 수동운전하게 된다. 이렇게 운전원들이 많은 위험부담을 안고 수동운전하는 이유는 증기발생기 수위제어는 증기발생기 내부의 광역수위 측정범위가 약 14.2(m)이고, 주요 제어변수를 측정하는 협역수위는 약 3.2(m)로 매우 적어서 물의 Swell, Shrink 현상과 급수온도의 영향으로 제어하기 매우 어렵기 때문이다. 그러나 DCS(Distributed Control System)내의 한 부분인 공정감시제어를 위한 MMI(Man Machine Interface) Software를 사용하면 한사람이 증기발생기 수위제어 전 계통의 감시 및 제어가 가능하게 된다. 또한 과거나 현재의 변화 추이 및 문제점 분석은 물론, 계통의 결함 발생시 경보가 발생하여 경보발생 화면을 선택할 경우 어느 부분에서 결함이 발생했는지를 보여준다. 만약 이 화면을 운전원이 아닌 현장 Engineer가 보았을 경우는 결함부분의 확인 및 결함카드 보수가 가능하여 운전원들의 작업부담 감소와 이로 인한 다른 계통 점검 시간을 충분히 확보할 수 있다.

• 한국태양에너지학회 논문집
• /
• 제33권1호
• /
• pp.66-72
• /
• 2013

In this study, the thermal conductive characteristics and basic properties of the nine commercial products of bentonite grouts were studied. Six of the nine products for ground heat exchanger systems are imported and others for civil engineering are domestic. The thermal conductivities of all bentonite products are nearly similar among products. The free swell indexes, viscosities and filter losses of the ground heat exchanger grouts are lower than those of the civil engineering ones. These characteristics seem to increase of the fluidity to fill the bentonite slurry to bore-hall perfectly, rather than to prevent underground water penetration. Thus, the mixtures of bentonites and sands are recommended for high thermal conduction grouts.

• 한국문화재보존과학회:학술대회논문집
• /
• 한국문화재보존과학회 2004년도 제20회 발표논문집
• /
• pp.66-71
• /
• 2004

When waterlogged wood dries up, it shrinks largely. And it is hard to recover original shape. Therefore it happens to lose the value of wood remains frequently. This paper studied how far dried waterlogged wood can recover original shape. Shape recovering course and extent are thoroughly investigated after waterlogged wood of Pinus densiflora, Quercus serrata and Styrax japonica oven-dries and instills varieties of test solution. At 1- step, oven-dried samples infiltrated by chlorous acid sodium or sodium hydroxide solution. At 2- step, wood tissues of samples were swelled by the fast decompression after infiltrating $CO_2-supercritical$ fluid at high pressure. The study investigated the possibility of shape recovering in waterlogged wood. Shape recovering rate is different with solution and wood species. Sample of sodium hydroxide solution doesn't swell anymore when using $CO_2-supercritical$ fluid. In general, the sample of sodium hydroxide solution has higher Shape recovering rate than $CO_2-supercritical$ fluid solution treated by chlorous acid sodium.

• 한국해양공학회지
• /
• 제18권1호
• /
• pp.75-79
• /
• 2004

Organic coatings are widely used to control of the corrosion of a steel structure. The water in coatings may cause the coatings to swell, leading to the degradation of the coatings. In addition, water affects the permeation of oxygen and other corrosive agents, and consequently, the presence of such substances at coating-metal interface promotes corrosion of the metal substrate. In this study, the anticorrosive properties of 4 types of coating, such as epoxy-epoxy, epoxy-urethane, urethane-epoxy, urethane-urethane, were evaluated. The evaluation tests were conducted under cyclic water-absorption/desorption conditions, consisting of alternative exposure to diluted 0.001M-LiCl(a$H_2O$≒1) and concentrated 10M-LiCl(a$H_2O$≒0.15). The anticorrosive performance of coatings was found to decrease in the order of urethane-urethane > urethane-epoxy > epoxy-epoxy coating.

• Journal of Electrical Engineering and Technology
• /
• 제13권2호
• /
• pp.790-799
• /
• 2018

This paper proposes a single-phase unified power quality conditioner (S-UPQC) for maintaining power quality issues in a microgrid. The S-UPQC can compensate the voltage and current harmonics, voltage sag, and swell as a dynamic voltage restorer (DVR), regardless of variations in the grid frequency. Odd harmonics are treated as even-order harmonics in a rotating frame to implement the harmonic compensators with only one repetitive controller (RC) without any harmonic extractor. The dynamic performance is improved and the delay time is reduced in the RC. The S-UPQC control scheme is designed to maintain accurate and stable operation under deviations of the grid frequency by using the Lagrange interpolation-based finite-impulse-response (LIFIR) filter approximation method. The proposed control schemes were validated through a simulation and experiment.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2005년도 전력전자학술대회 논문집
• /
• pp.185-188
• /
• 2005

The recent growth in the use of impactive and nonlinear loads, electronic devices sensitive to power quality has caused many power quality problems. Dynamic voltage restorers(DVR) are known as the best effective and economic means to compensate for power quality problems(especially, voltage sag and swell). In this paper, we addresses the detecting algorithms of an voltage sag and phase for operating DVR. Experimental results are included to illustrate the efficacy of the proposed algorithm.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2005년도 전력전자학술대회 논문집
• /
• pp.552-554
• /
• 2005

This paper deals with a simple structured voltage disturbance generator for power quality improving devices. The proposed generator can be applied to the performance test of custom power devices. Voltage sag, swell, outage, unbalance and phase jump after outage are provided by the generator. The improving phase jump operating principle of the generator is described and analysed. The usefulness of the generator is verified through simulation.

• 전기의세계
• /
• 제53권7호
• /
• pp.31-35
• /
• 2004

본 고에서는 현재 개발 및 필드테스트되고 있는 전력품질 보상기기인 STATCOM(Static Compensator), DVR(Dynamic Voltage Restorer), 고속전력절체스위치 SSTS(Solid State Transfer Switch)들이 국내 22.9kV급 배전계통에 도입되어 운용될 경우, 배전계통의 전력품질상의 외란, 즉 voltage sag, voltage swell, interruption등에 대해서도 부하기기가 문제없이 잘 동작할 수 있어야 하는 전력품질향상기기의 성능(전력품질향상기준)에 대한 평가방법 에 대하여 기술하고자 한다. 먼저, 전력품질향상기기인 DVR, D-STATCOM, SSTS들이 만족해야할 전력품질향상기준을 국내 전력 품질 실태를 고려하여 제시하고, 또한, 이들 전력품질향상기기에 대한 국내 배전계통적용에 적합한 성능평가방안을 제안/소개하기로 한다. (중략)