• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제55권5호
• /
• pp.245-249
• /
• 2006

Corona characteristics of conductors are dependent on the electric field conditions in the immediate vicinity of the conductors. In case of DC transmission line, particularly, the space charge plays an important role in the electric field distribution. Therefore, DC corona cage simulation is necessary for long-term test in the same conditions. This paper presents the results of designing and constructing hardwares such as DC power supply, measurement system and DAS to carry out the simulation. The corona cage longitudinally is divided into five equal length sections and three inner sections of those are isolated from the ground of outer cage. The measurement items are radio noise, corona current, television noise, audible noise and meteorological conditions. In the next step, various simulations about the type and configuration of two or three candidate conductors will be conducted. And then finally an environmentally-friendly conductor for HVDC overhead transmission line will be decided.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
• /
• pp.67-69
• /
• 2001

It is required to develop a rational transmission tariff system to ensure the fair participation of the players in the market. This study suggests an improved transmission tariff system which classifies the line capacity into line usage and reliability capacity based on their use and reasonably allocates the costs incurred by each of them to users. In addition, it takes the system load variations into consideration.

• International Journal of Automotive Technology
• /
• 제7권7호
• /
• pp.785-793
• /
• 2006

The topic of this study is the control strategy of a mild hybrid electric vehicle (HEV) equipped with a continuously variable transmission (CVT). A brief powertrain and vehicle configuration is introduced followed by the control strategy of the HEV with emphasis on two key parts. One of them is an ideal operating surface (IOS) that operates the CVT powertrain optimally from the viewpoint of the tank-to-wheel efficiency. The other is a charge sustaining energy management to maintain the battery state of charge (SOC) within an appropriate level. The fuel economy simulation results of the HEV over standard driving cycles were compared with those of the baseline vehicle. Depending on the driving cycle, 1.3-20% fuel saving potential is predicted by the mild hybridisation using an integrated starter alternator (ISA). The detailed energy flow analysis shows that the majority of the improvement comes from the idle stop function and the benefits for electrical accessories. Additionally, the differences between the initial and the final SOC are in the range $-1.0{\sim}+3.8%$ in the examined cycle.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
• /
• pp.450-453
• /
• 1988

A numerical scheme is considered for computing charge distributions and drawing equipotential lines for multiconductor transmission lines with arbitrary cross sections. Two-dimensional integral equation superposed by the charges is numerically calculated by the method of moments. Here in Galerkin's method special pulses cut into halves chosen for expansion and testing functions facilitate the numerical computations in solving the integral equation. Numerical examples are given for some system of which the shell conductor is grounded as the reference zero of potential.

• 대한전기학회논문지:전력기술부문A
• /
• 제53권8호
• /
• pp.461-465
• /
• 2004

This paper analysed the induced current density by electric field of human body under the 765 kV transmission line considering permittivity and conductivity. As permittivity of human body is very high as $10^6$ at 60 Hz, special numerical computation technique in Surface Charge Method(SCM) for composite media with extremely different properties is applied to reduce calculation error of induced current density and electric field inside the human body. Calculation results show that the average of the induced current density inside human body is about 3mA/$m^2$, which is less than ICNIRP criterion (10mA/$m^2$).

• Transactions on Electrical and Electronic Materials
• /
• 제16권5호
• /
• pp.241-249
• /
• 2015

Phase-locked-loops (PLL) have been employed in high-speed data transmission systems like wireless transceivers, disk read/write channels and high-speed interfaces. The majority of the researchers use a charge pump (CP) to obtain high performance from PLLs. This paper presents a review of various CMOS CP schemes that have been implemented for PLLs and the relationship between the CP parameters with PLL performance. The CP architecture is evaluated by its current matching, charge sharing, voltage output range, linearity and power consumption characteristics. This review shows that the CP has significant impact on the quality performance of CP PLLs.

• 대한전기학회논문지:전력기술부문A
• /
• 제50권12호
• /
• pp.556-560
• /
• 2001

To solve aeolian noise, we have tried several special conductor bundles equipped with spiral rod and one kind of low aeolian noise conductor with a special shape. Charge simulation method was applied to analyze electric field distributions of them in transmission line and corona cage for investigating the corona characteristics. This paper describes the electric field distributions and the performances of audible noise and radio interference from the special bundles in 765 kV transmission line by using corona characteristics obtained from corona cage simulation.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.491.1-491.1
• /
• 2014

Heteroatom phosphorous-doped graphene aerogel (PGA) with high surface area is successfully synthesized via hydrothermal method for high power and energy supercapacitors, including the advantage of three dimensional internetwork and constitutive graphene skeletons. The morphology of PGA was investigated by the scanning electron microscope, transmission electron microscope. The chemical structure and circumstances were confirmed by Raman and X-ray photoelectron spectroscopy, the phosphorus is successfully incorporated with the graphene sheets. As evidenced by electrochemical measurements, cyclic voltammetry and galvanostatic charge discharge, the hierarchically PGA has an unprecedented high capacitance, which contributes to the excellent high-rate performance of this material for supercapacitor application.

• 반도체디스플레이기술학회지
• /
• 제20권4호
• /
• pp.102-107
• /
• 2021

In this paper, the measurements of received power was shown and compared in two developed 5.8GHz 25W wireless charging systems. One is the system using commercial transmission antenna, and the other is the system using transmission antenna combined with metamaterial. The system combined with metamaterial shows higher received power due to negative reflective index of metamaterial. In addition, a comparative analysis of the systems shows that the transmission efficiency in the systems can decrease the real gain of transmission antenna due to higher side robe of beam pattern. The side robe beams of transmitting antenna interferes transmitted beam with the reflected beams from the bottom region due to the side robes. The failure problems of the RF wireless charging systems are discussed and proposed in order to charge mobile devices through the RF wireless charging system.

• Journal of Electrical Engineering and Technology
• /
• 제13권6호
• /
• pp.2412-2420
• /
• 2018

The thermal degradation of low density polyethylene (LDPE) will accelerate the production of carbonyl groups (C=O), which can act as the induced dipoles under high voltage. In this paper, we researched the dielectric properties and space charge behavior of LDPE after thermal aging, which can help us to understand the correlation between carbonyl groups (C=O) and electrical properties of LDPE. The spectra results show that LDPE exhibit obvious thermooxidative reactions when the aging time is 35 days and the productions mainly contain carboxylic acid, carboxylic eater and carboxylic anhydride, whose amount increase with the increasing of aging time. The dielectric properties show that the real permittivity of LDPE is inversely proportional to temperature before aging and subsequently become proportional to temperature after thermal aging. Furthermore, both the real and imaginary permittivity increase sharply with the increasing of aging time. The fitting results of imaginary permittivity show that DC conductivity become more sensitive about temperature after thermal aging. On this basis, the active energies of materials calculated from DC conductivity increase first and then decrease with the increasing of aging time. In addition, the space charge results show that the heterocharges accumulated near electrodes in LDPE change to the homocharges after thermal aging and the mean volume charge density increase with the increasing of aging time. It is considered that the overlaps caused by electrical potential area is the main reason for the increase of DC conductivity.