• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1552-1553
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• 2011

The HVDC transformer which is one of the main equipments for HVDC(High Voltage Direct Current) electric power transmission systems is exposed to not only AC voltage but also the inflowing DC voltage which comes from the DC-AC converter systems. Therefore, the HVDC transformer insulation system is required to withstand the electric field stress under AC, DC and DC polarity reversal conditions. However the electric field distributions under those conditions are different because the AC electric field and DC electric field are governed by permittivity and conductivity, respectively. In this study, the changes of electric potential and electric field of conventional AC transformer insulation system under DC polarity reversal test condition were analyzed by FEM(Finite Element Method). The DC electric field stress was concentrated in the solid insulators while the AC electric field stress was concentrated in the mineral oil. In addition, the electric stress under that condition which is affected by the surface charge accumulation at the interfaces between insulators was evaluated. The stress in some parts could be higher than that of AC and DC condition, during polarity reversal test. The result of this study would be helpful for the HVDC transformer insulation system design.

• Journal of the Korean Society of Safety
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• v.5 no.3
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• pp.44-50
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• 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.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.3
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• pp.148-151
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• 2004

For turn on high pressure sodium vapor lamp, Starting Voltage is very important factor. This starting voltage supply to high pressure sodium vapor lamp as electric discharge lamp, Electric field is producted in electric discharge tube, So accelerative electron collide against vapor atom and second electron is generated, And rapidly the current flow to electric discharge tube. This starting voltage is high voltage and source for melting contact that relay is according as turn on/off high pressure sodium vapor lamp. Consequently, This paper propose that the prevention of melting contact in accordance relay of controller for turn on/off high pressure sodium vapor lamp.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.155-158
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• 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).

• Journal of IKEEE
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• v.22 no.4
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• pp.916-921
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• 2018

In this paper, we analyzed the power MOSFET devices for high voltage and high current operation. 4H-SiC was used instead of Si to improve the static characteristics of the device. Since 4H-SiC has a high critical electric field due to wide band gap, 4H-SiC is more advantageous than Si in high voltage and high current operation. In the conventional VDMOSFET structure using 4H-SiC, the breakdown voltage is limited due to the electric field crowding at the edge of the p-base region. Therefore, in this paper, we propose a Curvature VDMOSFET structure that improves the breakdown voltage and the static characteristics by reducing the electric field crowding by giving curvature to the edge of the p-base region. The static characteristics of conventional VDMOSFET and curvature VDMOSFET are compared and analyzed through TCAD simulation. The Curvature VDMOSFET has a breakdown voltage of 68.6% higher than that of the conventional structure without increasing on-resistance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12A
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• pp.1136-1146
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• 2005

In this paper, the radiative electric field intensity due to the communication signal and conductive noise is calculated in overhead medium voltage power lines for power line communication. The input impedance is calculated by means of 2 port equivalent model of medium voltage power line network and basic transmission line theory. And then, currents is calculated by calculated input impedance and finally, the emissive electric field is calculated. The input impedance appears like a standing wave form with a fixed cycle because high reflection at the input terminal due to the characteristic impedance of medium voltage power line is very large. A calculated current and radiative electric field also appears like this form. From the measurement results, the measured results are very similar to the calculated results.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.8-14
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• 2011

The optimal geometry of the gate field plate in AlGaN/GaN-on-Si HEMT has been proposed using two-dimensional device simulation to achieve a high breakdown voltage for a given gate-to-drain distance. It was found that the breakdown voltage was drastically enhanced due to the reduced electric field at the gate corner when a gate field plate was employed. The electric field distribution at the gate corner and the field plate edge was investigated as functions of field plate length and insulator thickness. According to the simulation results, the electric field at the gate corner can be successfully reduced even with the field plate length of 1 ${\mu}m$. On the other hand, when the field plate length is too long, the distance between field plate and drain electrode is reduced below a critical level, which eventually lowers the breakdown voltage. The highest breakdown voltage was achieved with the field plate length of 1 ${\mu}m$. According to the simulation results varying the $SiN_x$ film thickness for the fixed field plate length of 1 ${\mu}m$, the optimum thickness range of the $SiN_x$ film was 200 - 300 nm where the electric field strength at the field plate edge counterbalances that of the gate corner.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.4
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• pp.659-665
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• 2017

Power semiconductor devices required the low on-resistance and high breakdown voltage. Wide band-gap materials opened a new technology of the power devices which promised a thin drift layer at an identical breakdown voltage. The diamond had the wide band-gap of 5.5 eV which induced the low power loss, high breakdown capability, low intrinsic carrier generation, and high operation temperature. We investigated the p-type pseudo-vertical diamond Schottky barrier diodes using a numerical simulation. The impact ionization rate was material to calculating the breakdown voltage. We revised the impact ionization rate of the diamond for adjusting the parallel-plane breakdown field at 10 MV/cm. Effects of the field plate on the breakdown voltage was also analyzed. A conventional diamond Schottky barrier diode without field plate exhibited the high forward current of 0.52 A/mm and low on-resistance of $1.71{\Omega}-mm$ at the forward voltage of 2 V. The simulated breakdown field of the conventional device was 13.3 MV/cm. The breakdown voltage of the conventional device and proposed devices with the $SiO_2$ passivation layer, anode field plate (AFP), and cathode field plate (CFP) was 680, 810, 810, and 1020 V, respectively. The AFP cannot alleviate the concentration of the electric field at the cathode edge. The CFP increased the breakdown voltage with evidences of the electric field and potential. However, we should consider the dielectric breakdown because the ideal breakdown field of the diamond is higher than that of the $SiO_2$, which is widely used as the passivation layer. The real breakdown voltage of the device with CFP decreased from 1020 to 565 V due to the dielectric breakdown.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1473_1474
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• 2009

To develop electrically reliable high voltage apparatuses, the experimental study on the electrical breakdown field strength is needed, as well as theoretical approach. In this paper, lightning impulse breakdown characteristics considering utilization factors are investigated for the establishment of insulation design criteria of an high voltage apparatus. The utilization factors are represented as the ratio of mean electric field to maximum electric field. Dielectric experiments are performed by using five kinds of sphere-plane electrode systems made of stainless steel. As a result, it is found that dielectric characteristics are affected by not only gap length but also utilization factor of electrode systems. The results are expected to be applicable to the design of high voltage apparatuses.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.2001-2006
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• 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.