• Journal of Electrical Engineering and Technology
• /
• 제12권5호
• /
• pp.2001-2006
• /
• 2017

This paper explains the effects of the weak signal of a rotating-type electric field mill sensor fabricated for measuring the intensity of the electric field generated by high-voltage direct current (HVDC) power transmission lines. The fabricated field mill consists of two isolated electrode vanes, a motor driver, and a ground part. The sensor plate is exposed to and shielded from the electric field by means of a rotary shutter consisting of a motor-driven mechanically complementary rotor/stator pair. When the uncharged sensor plate is exposed to an electric field, it becomes charged. The rotating electrode consists of several conductive vanes and is connected to the ground part, so that it is shielded. Determining the appropriate design variables such as the speed of the vane, its shape, and the distance between the two electrodes, is essential for ensuring optimal performance. By varying the speed, the weak signal characteristics which is used to signal processing and calibration experiment are quite different. Each weak signal pattern was analyzed along with the output voltage characteristics, in order to be able to determine the intensity of the electric field generated by HVDC power transmission lines with accuracy.

• Journal of Astronomy and Space Sciences
• /
• 제34권4호
• /
• pp.251-256
• /
• 2017

The electric coupling between the lithosphere and the ionosphere is examined. The electric field is considered as a timevarying irregular vertical Coulomb field presumably produced on the Earth's surface before an earthquake within its epicentral zone by some micro-processes in the lithosphere. It is shown that the Fourier component of this electric field with a frequency of 500 Hz and a horizontal scale-size of 100 km produces in the nighttime ionosphere of high and middle latitudes a transverse electric field with a magnitude of ~20 mV/m if the peak value of the amplitude of this Fourier component is just 30 V/m. The time-varying vertical Coulomb field with a frequency of 500 Hz penetrates from the ground into the ionosphere by a factor of ${\sim}7{\times}10^5$ more efficient than a time independent vertical electrostatic field of the same scale size. The transverse electric field with amplitude of 20 mV/m will cause perturbations in the nighttime F region electron density through heating the F region plasma resulting in a reduction of the downward plasma flux from the protonosphere and an excitation of acoustic gravity waves.

• 한국전기전자재료학회논문지
• /
• 제36권4호
• /
• pp.408-412
• /
• 2023

In this paper, in order to analyze high electrical insulation and cooling performance using mineral oil, the liquid insulating oil was changed in electrode shape and distance between electrodes to compare and analyze electrical characteristics according to equal electric field, quasi-equivalent electric field, and unequal electric field. As a result, the breakdown voltages were 36,875 V and 36,875 V in the form of sphere-sphere and plate-plate electrodes with equal electric fields. The breakdown voltage was 31,475 V in the sphere-plate electrode type, which is a quasi-equilibrium field, and the breakdown voltage was 28,592 V, 27,050 V, and 22,750 V in the needle-needle, sphere-needle, and needle-plate electrode types, which are unequal fields. Through this, it is possible to know the difference in breakdown voltage according to the type of electric field. The more equal the field, the higher the breakdown voltage, and the more unequal field, the lower the breakdown voltage. The difference in insulation breakdown voltage could be seen depending on the type of electric field, the insulation breakdown voltage was higher for the more equal electric field, and the insulation breakdown voltage was lower for the more unequal electric field. Also, it was confirmed that the closer the distance between the electrodes, the higher the insulation breakdown voltage, the higher the insulation breakdown current, and the insulation breakdown voltage and the insulation breakdown current were proportional.

• 대한기계학회논문집B
• /
• 제26권10호
• /
• pp.1451-1457
• /
• 2002

When an aqueous liquid such as water having high electric conductivity and high surface tension is discharged from a nozzle under a strong DC electric field, fine drops ranging from 30 to 450 microns can be obtained only through the spindle mode. In the present study, effects of the electric conductivity and the surface wettability of nozzle materials on formation of drops with this mode were investigated. For that, three nozzles with the same size but with different materials were prepared and tested; a stainless steel needle, and a plain and a metal (gold)-coated (except for the tip portion) silica needles. Uniform drops were obtained with the gold-coated silica nozzle over the wider range of the DC voltage input. That is, formation of the liquid cone and detachment of the liquid spindle (ligament) can be more stabilized and frequent with the needles having high electric conductivity but with low surface wettability at their tips.

• 전기학회논문지
• /
• 제61권10호
• /
• pp.1454-1460
• /
• 2012

In order to develop an new electric insulation material for heavy electric equipments, epoxy/micro/nano composite (EMNC) was prepared by mixing micro-silica with nano layered silicate, where the nano layered silicate was synthesized by our electric field dispersion method, EMNSC was prepared by treating the EMNC with a silane coupling agent. Thermal properties such as glass transition temperature (Tg) and thermal expansion coefficient, and DMA characteristics were studied, and mechanicla properties such as tensile and flexural tests were performed. AC electrical insulation strength was also tested. All properties of EMNSC were modified by treating EMNC with silane coupling agent and it was confirmed that our new developed composites could be used in the heavy electric equipments.

• 전기학회논문지P
• /
• 제57권3호
• /
• pp.265-269
• /
• 2008

Output voltage value of AC high voltage source has usually been obtained by measuring the low arm voltage of high voltage divider or the secondary voltage of high voltage transformer. In this study, we have fabricated the AC 400 kV high voltage divider using high voltage electrode and electric field measurement sensor. The dividing ratio of the fabricated 400 kV high voltage divider was evaluated using reference 400 kV capacitive divider. The dividing ratio of 400 kV high voltage divider is found to be 12,322 and has the good linearity within 0.63 % against AC high voltage up to 400 kV. Therefore, the developed 400 kV high voltage divider could evaluate 400 kV high voltage supply and voltage divider used in industry.

• 한국안전학회지
• /
• 제5권3호
• /
• pp.44-50
• /
• 1990

This study is conducted to examine the theoretical background of characteristics for electric shock encountered in special high-voltage electric lines among the accidents of electric shock, and to calculate applied current to human body and field strength over the head by means of numerical anaysis through FEM(Finite Element Method), and to make clear the hazard level to the human body, and to establish the approach limit distance of human body to the electric lines, which could be applied to the safety standard while working in the vicinity of special high-voltage electric lines.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
• /
• pp.155-158
• /
• 1988

The fabrication of devices using plans technology could lend to n serious degradation in the breakdown voltage as a result of high electric field at the edges. An elegant approach to reducing the electric field at the edge is by using field limiting ring. The presence of surface charge has n strong influrence on the depletion layer spreading at the surface region because this charge complements the charge due to the ionized acceptors inside the depletion layer. Surface charge of either polarity can lower the breakdown voltage because it affects the distribution of electric field st the edges. In this paper we discuss the influrences of fixed oxide charge on the breakdown voltage of the p+/n junction with field limiting ring(or without field limiting ring).

• 대한전자공학회논문지SD
• /
• 제48권12호
• /
• pp.8-14
• /
• 2011

본 논문에서는 이차원 소자 시뮬레이션을 활용하여 주어진 게이트-드레인 간격에서 AlGaN/GaN-on-Si HEMT (high electron mobility transistor) 의 고항복전압 구현을 위한 게이트 전계판의 최적화 구조를 제안하였다. 게이트 전계판 구조를 도입하여 게이트 모서리의 전계를 감소시켜 항복전압을 크게 증가시킬 수 있음을 확인 하였으며, 이때 전계판의 길이와 절연막의 두께에 따라 게이트 모서리와 전계판 끝단에서 전계분포의 변화를 분석하였다. 최적화를 위하여 시뮬레이션을 수행한 결과, 1 ${\mu}m$ 정도의 짧은 게이트 전계판으로도 효과적으로 게이트 모서리의 전계를 감소시킬 수 있으며 전계판의 길이가 너무 길어지면 전계판과 드레인 사이의 남은 길이가 일정 수준 이하로 감소되어 오히려 항복전압이 급격하게 감소함을 보였다. 전 계판의 길이가 1 ${\mu}m$ 일 때 최대 항복전압을 얻었으며, 게이트 전계판의 길이를 1 ${\mu}m$로 고정하고 $SiN_x$ 박막의 두께를 변화시켜본 결과 게이트 모서리와 전계판 끝단에서의 전계가 균형을 이루면서 항복전압을 최대로 할 수 있는 최적의 $SiN_x$ 박막 두께는 200~300 nm 인 것으로 나타났다.

• 한국기술혁신학회:학술대회논문집
• /
• 한국기술혁신학회 2000년도 추계 학술대회(The 2000 Autumn Conference of korea Technology Inovation Society)(한국기술혁신학회)
• /
• pp.177-193
• /
• 2000

In foreign countries, high-efficiency electric machineries have been developed in view of cost reduction, environmental issues, energy conservation etc. Especially they focus on developing energy conservation measures and demand-side management. Thus, patent application and secure of patent claims are on the rise as important issues in this field. In this paper, we analyzed patent application trends about inverters, ac/dc converters, reactive power control equipments, high-efficiency transformers and electric ballasts among high-efficiency electric machineries. First, we analyzed general technology trends, and constructed patent technology data. Second, we graphed patent application trends in terms of application years, assignees and nations.