• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.636-639
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• 2004

This paper presents the fabrication and performance evaluation of zinc oxide varistors for the arresters used for station system. ZnO varistors were fabricated with typical ceramic production methods and the structural and electrical characteristics were investigated. All varistors exhibited high density, which were in the range of $5.41{\sim}5.49g/cm^3$. In the electrical properties the reference voltage increased in the range of $4.410{\sim}5.250kV$ with increasing their thickness and the residual voltage exhibited the same trends as the reference voltage. In the long duration current impulse withstand test, E-2 and F-1 samples failed in the two and four shots, respectively, but E-1 and F-2 samples survived 18 shots during the test. Before and after this test, the variation ratio of residual voltage of E-1 and F-2 samples were -0.34% and 0.05%, respectively, which were in the acceptance range of 5%. According to the results of tests, it is thought that if the fabrication process such as insulating coating, sintering condition, and soldering method is improved, these ZnO varistors would be possible to apply to the station class arresters in the new future.

• International Journal of Computer Science & Network Security
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• v.22 no.11
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• pp.308-318
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• 2022

Noise is a serious issue. While sending images via electronic communication, Impulse noise, which is created by unsteady voltage, is one of the most common noises in digital communication. During the acquisition process, pictures were collected. It is possible to obtain accurate diagnosis images by removing these noises without affecting the edges and tiny features. The New Average High Noise Density Median Filter. (HNDMF) was proposed in this paper, and it operates in two steps for each pixel. Filter can decide whether the test pixels is degraded by SPN. In the first stage, a detector identifies corrupted pixels, in the second stage, an algorithm replaced by noise free processed pixel, the New average suggested Filter produced for this window. The paper examines the performance of Gaussian Filter (GF), Adaptive Median Filter (AMF), and PHDNF. In this paper the comparison of known image denoising is discussed and a new decision based weighted median filter used to remove impulse noise. Using Mean Square Error (MSE), Peak Signal to Noise Ratio (PSNR), and Structure Similarity Index Method (SSIM) metrics, the paper examines the performance of Gaussian Filter (GF), Adaptive Median Filter (AMF), and PHDNF. A detailed simulation process is performed to ensure the betterment of the presented model on the Mini-MIAS dataset. The obtained experimental values stated that the HNDMF model has reached to a better performance with the maximum picture quality. images affected by various amounts of pretend salt and paper noise, as well as speckle noise, are calculated and provided as experimental results. According to quality metrics, the HNDMF Method produces a superior result than the existing filter method. Accurately detect and replace salt and pepper noise pixel values with mean and median value in images. The proposed method is to improve the median filter with a significant change.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.6
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• pp.78-84
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• 2009

This paper presents measurement results of transient impedance for small-sized ground electrodes in a discharge region of soil. For a realistic analysis of ionization characteristics near the ground electrode, three types of ground rod installed outdoors and high voltage impulse generator were used for injecting test current. From the analysis of response voltage and current flowing ground electrode to earth, it is verified that the ionization near the ground electrode contributes to reduction of ground impedance and limits the ground potential rise effectively in high resistivity soil. As a threshold electric field density for ionization is small in low resistivity soil, the shape of ground electrode rarely contributes to the transient impedance. And, from the experiment result with shape of ground electrode, the rod with needles is more effective to reduce the transient impedance than the plate electrode in the voltage range including with ionization regions of soil.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.186-188
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• 2003

The ZnO surge arrester is the protective device for limiting surge voltages on equipment by diverting surge current and returning the device to its original status. The occurrence of overvoltage appears in any phase to AC power supply system and it appears in mixing AC and impulse voltages, moreover because HVDC power supply system uses converter in semiconductor, it makes mixed DC and high harmonics voltages. In this study, the various mixed AC and DC voltages was made for investigating the degradation effect of ZnO arrester according to mixed voltage. As a result, the increase of DC component to mixed voltages causes the increase of resistive component of total leakage current to ZnO block. In changing V-I curve for mixed voltages, the cross-over point acts a factor as making the proper capacitor size of an equivalent circuit for ZnO block.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.456-458
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• 2006

Power line communication: PLC which easy to install at anywhere near outlet for electric machine. PLC uses transmission line for voltage of which is 60 Hz. Signals don't affect to electric machine in PLC because they are very small voltage. One of the important thing is the processes of adding signal to power line and extracting the signal from power line, the other is to choose the strong modulation method which sends signals long distance without loosing in PLC channel. but PLC channel have very high and variable noise and attenuation and then it is very hard to transmit optimally between the transmitter and the receiver. After all, impedance and noise problems of PLC channel must be overcame. Noises of 2 kinds which are AWGN abd impulse noise and attenuation are orated. To overcome the noise. Recently, Multi-carrier Modulation: MCM methods like as OFDM and DMT which are divide the channel into many sub-channel have been studied. those are powerful communication methods in PLC. In this paper, PLC channels made up of 3 numbers of noise and attenuation are simulated for getting BER by Matlab simulink.

• Journal of Sensor Science and Technology
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• v.4 no.1
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• pp.15-20
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• 1995

This paper deals with the planar-type sensor which can measure the time-varying electric fields. To make an electric field measurement system having a wide bandwidth, a planar-type sensor is proposed. The theoretical principle and design rule of the measuring device are introduced, and also the calibration and application investigations are carried out. From the calibration experiments, the frequency bandwidth of the electric field measurement device ranges from 160 [Hz] to 25 [MHz] and the sensitivity of the sensor is 1.2 [mV/V/m]. As the application experiments, the electric fields caused by the impulse and oscillating transient voltage in high voltage laboratory are measured by the proposed device, and the results are excellent.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.5
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• pp.40-45
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• 2011

In this paper, to develop a broadband power line communication modem and network technologies, we analysis the characteristics of underground power line communication channel through actual tests. To measure the amount of attenuation by length and structure of broadband power line communication channel, we configure a measurement system of the channel with signal generator, spectrum analyzer and non-contacted coupler. For actual tests, we choose two of the longest lines among medium-voltage lines as a single line in the test lines and measure the characteristics of noise and signal attenuation level of the channel. The experimental results show that the channel has a impulse noise which can remarkably reduce communication capability. In the case of long lines, high-frequency attenuation appeared by length of the lines.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.265-267
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• 1991

In this paper, we describe the development of 345kv OF cables to contain also the cable employing new insulation paper, PPLP (Poly propylene Laminated paper). The cables all show very excellent properties, especially PPLP cable has less the dielectric loss and better the impulse & A.C strength than the one employing the conventional paper. Therefore, according to use PPLP cable, it seems to be several advantages such as the compact of system, the increasing capacity, and the decreasing energy loss etc.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.636-639
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• 1996

We have developed a part of hydraulic stroke sensing cylinder using magnetic sensor that can detect each position under severe construction fields. In this paper, for evaluating the developed cylinder under various environment condition, thermal control systems and two hydraulic systems to be coupled consist of. The former is composed of an heater case, temperature sensor, and interface circuits which include SCR(silicon controlled rectifier) for the control of the voltage's phase. The latter is composed of an hydraulic cylinder for position control with solenoid valve (ON/OFF motion) and a load cylinder with proportional reducing valve. To obtain the various performance evaluation, it is carried out under high temperature condition in thermal system controlled by using Ziegler-Nichols PID tuning method and artificial disturbances such as impulse or constant force. The results show that the developed cylinder has good performance under the various environment condition.

• Progress in Superconductivity and Cryogenics
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• v.13 no.3
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• pp.5-9
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• 2011

DC high-temperature superconducting(HTS) cable system has attracted a great deal of interest from the view point of low loss, dense structure and large capacity. A HTS cable system is made of cable and termination. The insulating materials and insulation technology must be solved for the long life, reliability and compact of cable system. In this paper, we will report on the dielectric breakdown characteristics of insulating materials for HTS cable and termination. The AC, DC and lightning impulse breakdown strength of laminated polypropylene paper(PPLP) and glass fiber reinforced plastic(GFRP) have been measured under nitrogen pressures in the range of 0.l-0.4MPa. PPLP and GFRP are found to have a significantly higher DC breakdown strength. Also, DC surface flashover voltage of negative polarity is slightly higher than that of positive polarity in GFRP.