• Transactions on Electrical and Electronic Materials
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• 제14권6호
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• pp.308-311
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• 2013

The effect of an electric field on the ac electrical treeing in various epoxy/reactive diluent systems was studied in a needle-plate electrode geometry. Diglycidyl ether of bisphenol A (DGEBA) type epoxy was used as a base resin, and 1,4-butanediol diglycidyl ether (BDGE) or polyglycol (PG) as a reactive diluent was introduced to the DGEBA system, in order to decrease the viscosity of the DGEBA epoxy system. BDGE was acted as a chain extender, and PG acted as a flexibilizer, after the curing reaction. To measure the treeing initiation time and the propagation rate, three constant alternating currents (ac) of 10, 13 and 15 kV/4.2 mm (60 Hz) were applied to the specimen, in a needle-plate electrode arrangement, at $30^{\circ}C$ of insulating oil bath. When 10 kV/4.2 mm (60 Hz) was applied, the treeing initiation time and the propagation rate in the DGEBA system were 356 min and $1.10{\times}10^{-3}$ mm/min, respectively, those in the DGEBA/BDGE system were 150 min and $1.14{\times}10^{-3}$ mm/min, respectively. Those in the DGEBA/PG system were 469 min and $1.05{\times}10^{-3}$ mm/min, respectively. As 15 kV/4.2 mm (60 Hz) was applied, the propagation rate in the DGEBA system was $5.41{\times}10^{-3}$ mm/min, and that in the DGEBA/PG system was $1.42{\times}10^{-3}$ mm/min. These values meant that PG could be used as a reactive diluent in the DGEBA system, without the deterioration of the insulation breakdown property.

• 한국염색가공학회지
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• 제13권2호
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• pp.42-42
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• 2001

Following the prior studs regarding that 1.0g of cotton fabric cound be dyed uniformly with a reactive dye in the solvent mixture of 2㎖ of water and 23㎖ of dichloromethane, silk fabric was dyed with C. I. Reactive Blue 203 in the water/dichloromethane two-phase immiscible solvent media. In order to minimize dye loss due to its hydrolysis, the reactive dyeing was carried out in dichloromethane containing a small amount of water. With only 3㎖ of water in 22㎖ of dichloromethane, 1.0g of silk fabric could be dyed perfectly. The uptake ratio was increased greatly, compared with that of normal reactive dyeing in a water medium. It would seem that the one of hydrophobic solvents, dichloromethane, can assist the even dyeing as it disperses a small amount of dye-dissolved water phase and conveys this water phase to the fabric entirely and uniformly.

• 한국염색가공학회지
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• 제13권2호
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• pp.128-134
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• 2001

Following the prior studs regarding that 1.0g of cotton fabric round be dyed uniformly with a reactive dye in the solvent mixture of $2m\ell$ of water and $23m\ell$ of dichloromethane, silk fabric was dyed with C. I. Reactive Blue 203 in the water/dichloromethane two-phase immiscible solvent media. In order to minimize dye loss due to its hydrolysis, the reactive dyeing was carried out in dichloromethane containing a small amount of water. With only $3m\ell$ of water in $22m\ell$ of dichloromethane, 1.0g of silk fabric could be dyed perfectly. The uptake ratio was increased greatly, compared wish that of normal reactive dyeing in a water medium. It would seem that the one of hydrophobic solvents, dichloromethane, can assist the Even dyeing as it disperses a small amount of dye-dissolved phase and conveys this water phase to the fabric entirely and uniformly.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.77-82
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• 2001

As electric power systems have been moving from vertically integrated utilities to a deregulated environment, the charging of reactive power management is a new challenging theme for market operators. This paper proposes a new methodology to compute the costs of providing reactive power management service in a competitive electrical power market. The proposed formulation, which is basically different from those shown in the literature, consists of two parts. One is to recover investment capital costs of reactive power supporting equipment based on a reactive power flow tracing algorithm. The other is to recover operational costs based on variable spot prices using the optimal power flow algorithm. The charging shapes resulted from the proposed approach exhibit a quite good meaning viewed from a practical sense. It turns out that reactive power charges are mostly due to recovery of capital costs and slightly due to recovery of operational costs. The method can be useful in providing additional insight into power system operation and can be used to determine tariffs of a reactive power management service.

• KIEE International Transactions on Power Engineering
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• 제5A권3호
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• pp.228-234
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• 2005

This paper presents the evaluation of reactive power pricing through the control of generator voltages under the assumption that the reactive power market has been transformed into the real power market. By applying the concept of economic dispatch, which minimizes the total cost of real power generation to reactive power generation, the algorithm for implementing reactive power pricing is proposed to determine the optimum voltage profiles of generators. It consists of reactive power voltage equation, the objective function that minimizes the total cost of reactive power generation, and linear analysis of inequality constraints in relation to the load voltages. From this algorithm, the total cost of the reactive power generation can be yielded to the minimum value within network constraints as the range of load voltages. This may provide the fair and reasonable price information for reactive power generation in the deregulated electricity market. The proposed algorithm has been tested on the IEEE 14-bus system using MATLAB.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.251-254
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• 2003

A voltage stability assessment consists of the contingency screening, voltage stability analysis, and counter measures. A widely used index for the voltage stability assessment of power system is the reactive power margin. It shows some factors of voluntariness as following the status of power system and load levels for the target analyzing area. Therefore, it has a demerit that the absolute amounts of reactive power margin is not to be applied by the quantized margin criterion. This paper selects a vulnerable area by assigning the voltage instability for the particular contingency for the selection of vulnerable area in the respect of the investigation of reactive power margin or VQVI as an index of V-Q margin sensitivity in order to overcome the demerit. This will be able to grasp the V-Q margin sensitivity for the target analyzing area by presenting the ratio of power margin between the margin before and after contingency as following the calculation of reactive power margin. The presented method is applied to the voltage stability assessment for the Metropolitan area of 2003 KEPCO summer peak system.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1377-1382
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• 2015

Power system restoration following a massive blackout starts with re-energizing Primary Restorative Transmission (PRT) systems at first. As power systems have been gradually enlarged and become more complex, periodical evaluation and reassignment of PRTs are needed. So far it has been decided by try and error approach by corresponding human experts to analyze and evaluate them. This paper presents an intelligent system that finds optimal primary restoration paths using analytic and heuristic knowledge from PSS/E data, and suggests an optimal PRTs depending on the condition of Ferranti effect or a reactive power capability margin of black-start generator. This system was tested in Korea Electric Power system, and showed a promising result.

• 전기의세계
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• 제31권5호
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• pp.375-382
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• 1982

The optimum control of voltage and reactive power in large system requires large amounts of complicated calculation. If the large power system is controlled by the centralized control scheme, the necessary computing time, memory requirments and data transmission channels increase exponetially, and computer control of the system becomes difficult. Piecewise method which aims at the reduction of the difficulties of centralized control scheme is to decompose a large power system into several subsystems, each of which is controlled by a local computer and the control efforts of each subsystem are coordinated by a central computer. Unless sufficient coordination is made between subsystems, the control quality may become very poor. This paper describes how piecewise method can be applied in the optimal control of voltage and reactive power in large system, and presents effective calaulating algorithm for the solution of the problem. The numerical example for model system is presented here.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.9-11
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• 2003

In power system planing and operation, voltage and reactive power control are very important. The voltage deviation and system losses can be reduced through control of reactive power sources. In general, there are several different reactive power sources, we used UPFC and switched shunt capacitor to improve the voltage profile and to reduce system losses in this study. Since there are many switched shunt capacitors in power system, so it is necessary to coordinate these switched shunt capacitors. In this study, Genetic Algorithm(GA) is used to find optimal coordination of UPFC and switched shunt capacitors in a local area of power system. In case study, the effectiveness of the proposed method is demonstrated in KEPCO's power system. The simulation is performed by PSS/E.

• 자연과학논문집
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• 제9권1호
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• pp.9-17
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• 1997

염색가공 폐액중의 반응성 염료에 대한 탈색효과를 검토하기 위하여 산화력이 강한 오존을 사용하여 염료의 농도, 처리용액의 pH, 처리용액의 온도조건 등을 변화시켜 가며 오존의 농도와 피로시간에 대한 염료의 탈색과정에 대하여 연구하였다. 오존의 처리 능력은 염료 폐액의 농도가 높아지면 그만큼 오존이 많이 필요하게 되므로 처리 속도도 떨어졌다. 반응성 염료의 탈색 속도는 진한 색상인 blue가 제일 늦었으며 옅은 색상일수록 빠르게 탈색이 진행되었다. 오존의 처리 시간이 경과함에 따라 반응성 염료의 색상은 중간색을 거쳐 무색으로 변하여 색상이 파괴됨을 보였다. 반응성 염료는 색상에 따라 약간의 차이는 있지만 알칼리 영역에서보다는 산성영역에서 더 빠르게 탈색이 진행되었다. 오존처리 온도가 낮을수록 탈색속도가 빠르게 나타났지만 그 차이는 적었다.