• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.60-66
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• 2010

Mesh grounding electrodes in Korea and abroad are designed as lattice-shaped equidistance grounding grids. In case of a lattice-shaped grounding Grid, however, there is a problem of higher touch voltage at the corner of the grid relative to the center. To overcome this problem, we used oblique-shaped equidistance grounding grid to reduce the area of the corner where mesh voltage occurs. As a result the mesh voltage was reduced. Therefore, this paper suggests the use of oblique-shaped grounding grid instead of the existing lattice-shaped ones. It applied the same grounding design dimensions for both lattice-shaped and oblique-shaped grounding grids, compared and analyzed mesh voltage, GPR, ground resistance, total length of grounding conductor, verified that oblique-shaped grounding grid is superior to the lattice-shaped.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.2
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• pp.95-101
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• 2003

In this paper, partial discharges(PDs), lift off and breakdown voltage were measured when metal particles existed in a model GIS coated with epoxy resin on its bottom electrode, and the measured results were analyzed after comparing with the model DIS not coated. In order to presume the various fault case in GIS, we measured the experimental values with changing some experimental factors, such as the mixture ratio of SF$\_$6//N$_2$, the pressure of the gases, the kinds and diameter of the metal particles, and the coating thickness of the epoxy resin. As a result, the PDIV increased with the thickness of the epoxy resin, while the magnitude of PDs decreased at the same condition. The lift off voltages of steel alloy particles were higher than that of copper particles, and increased wit diameter of particles. Futhermore, the lift off voltages in the case of the electrode coated with epoxy resin were higher than that in the case of the uncoated one. In addition, the thicker the thickness of the epoxy resin was, the higher the breakdown voltage were. Thus, it was confirmed that the GIS coated with epoxy resin on its inner surface could be improved in insulation performance.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.5
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• pp.80-87
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• 2009

Recently, ozone has been utilized in various fields thanks to its effectiveness, and has been in ever-growing demand. Accordingly, various kinds of ozonizers have been examined among researchers. This paper is concerned with developing the cascade-type plate electrode ozonizer(PTO) for improvements of indoor air, water supply and drainage and investigating its characteristics. Four types of ozonizers have been devised according to their size, numbers and arrangement Electric discharge area of each type of ozonizer has the same size of 22,400[$mm^2$], and its discharge power has the maximum 40[w]. As the result of having studied ozone generation ozone concentration and ozone yield characteristics of each ozonizer, we found that the type of ozonizer in which eight plates were arranged into cascade type(PTO-4) was the most excellent one.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.32-37
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• 1999

The superposing effect of SPCP(Surfoce Induced Plasma Chemical Process) and corona discharge has been studied for rerroval of NOx from industrial flue gases. NOx rermval rates by SPCP, corona discharge and superposing discharge were monitored and compared. Parameters were the concentration and the flow rate of gas, frequency and the type of discharge. Experirrental results showed that NOx removal rate by sUIffPOSing discharge was 10-15[%] higher than that by the other two modes. The higher NOx. rermval rate was observed with the lower frequency of upper electrode in the combined reactor and with the higher frequency of lower electrode. 'The maximum obtainable NOx. rerroval rate by SPCP (18 [W]) and corona discharge (8.5 [W]) was 80[%] and 10[%], respectively. With the combination of the two modes, however, 90[%] of NOx removal rate was observed with the discharge power of 14 [W].14 [W].

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.8
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• pp.67-74
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• 2008

In this paper we describe discharge characteristics between needle-to-plane electrodes in water in various conditions such as different impulse voltages, polarities and water resistivities. Streamer corona is initiated at the tip of needle electrode and propagates toward plane electrode, and it experiences the final jump across the test gap. The branched channels of streamer coronas for lower water resistivities are much thicker and brighter than those for higher water resistivities at the same level of applied voltage. The negative streamer coronas not only have more branches but also widely spread out compared to the positive streamer coronas. A number of pulse-like currents ranging from some hundreds mA to a few A after streamer corona onset were produced with discharge developments. The time-lags-to breakdown for the positive polarity were remarkably shorter than those for the negative polarity. The pre-breakdown energy supplied into the test gap was inversely proportional to water resistivity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.5
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• pp.413-417
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• 2010

Line to ground faults by deterioration of insulators has frequently occurred in power system, and the main cause is surface contamination of the insulators. The contamination of insulator is analyzed by monitoring the surface leakage current flowing them. The suspension insulator is monitored by installation of a zero-phase current sensor(ZCT), but the line-post insulator is impossible to apply the same method because of its large diameter structure. This paper proposed a detection method of surface leakage current for a line-post insulator, and it can easily be applied to new and/or built insulators. The leakage current is indirectly calculated from the potential difference between the metal electrode attached on the surface of insulator and the ground connector. To evaluate the performance of the proposed method, the leakage current is compared as a function of contamination condition controlled by the density of NaCl solution. The leakage current is proportioned to the density of NaCl solution, and the voltage detected by the electrode showed the same trend. From the experimental results, we designed and fabricated a monitoring device which is composed of a detection electrode, signal converter, microprocessor, and ZigBee, and its measurement range is $10{\mu}A{\sim}5mA$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.3
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• pp.187-192
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• 2017

This paper presents an ongoing study to develop a novel pressure sensor by means of a Nano Carbon Piezoresistive Composite (NCPC). The sensor was fabricated using the 3D printing process. We designed a miniaturized cantilever-type sensor electrode to improve the pressure sensing performance and utilized a 3D printer to build a small-sized body. The sensor electrode was made of 2 wt％ MWCNT/epoxy piezoresistive nano-composite, and the sensor body was encapsulated with a pipe plug cap for easy installation to any pressure system. The piezoresistivity responses of the sensor were converted into stable voltage outputs by using a signal processing system, which is similar to a conventional foil strain gauge. We evaluated the pressure-sensing performances using a pressure calibrator in the lab environment. The 3D-printed cantilever electrode pressure sensor showed linear voltage outputs of up to 16,500 KPa, which is a 200％ improvement in the pressure sensing range when compared with the bulk-type electrode used in our previous work.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1613-1621
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• 2002

An electromagnetic flowmeter(EMF) essentially averages the velocity distribution over the pipe cross- sectional area, and the measured value is dependent on the velocity profiles. In this study, installation effects of 90$^{\circ}$long elbow(KS B 1522, ISO 3419) on the EMF characteristics was investigated. A commercial EMF was adopted and the distribution of magnetic field in the electrodes cross section was measured. In the experiment, the national flow standard system, of which measurement uncertainty was evaluated in accordance with ISO 17025 recommendation, was used fur characterization of EMF. The leading line has 150D long straight pipe to established a fully developed flow before entering into the elbow and the elbow was installed downstream of it. then the flowmeter was tested within 50 D from the elbow. The installation effects of the flowmeter were investigated by varying the mean velocity(Reynolds No.)in pipe section, the locations and the direction of electrodes plane.($\phi$) From the experimental results, we find the optimal conditions to get most accurate measurements. Generally, the deviations from the calibration value were less than 0.5 % in farther than 10D distance from the elbow and the direction of electrode plane. $\phi$ = 90$^{\circ}$yielded the smallest measurement deviation. These characteristics were shown consistently in turbulent region regardless of the mean Reynolds number.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.2
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• pp.93-101
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• 2016

This paper presents the surface discharge characteristics in Dry-Air on laminated epoxy solid dielectrics and conductive particles in order to provide the valuable information for the insulation design of eco- friendly gas insulated switchgear. To improve insulation performance, the three types of the laminated epoxy solid dielectrics were proposed, and it was revealed that their surface discharge characteristics were similar to the bakelite dielectrics of same-laminated types. From the surface discharge characteristics of dry air, it was demonstrated that the effect of conductive particles on surface discharge voltage was dominant when there are this particles at the shortest electrode gap and that the degradation of insulation performance on the conductive particles was evident in epoxy than teflon. These phenomena were interpreted in terms of particle-triggered discharge mechanism and electric field of triple junction, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.4
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• pp.95-101
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• 2015

This paper presents experimental results about characteristics of soil discharge as a function of moisture content when the $1.2/50{\mu}s$ lightning impulse voltage is applied. The laboratory experiments, for this study, were carried out based on factors affecting the transient behavior in soils. The electrical breakdown in soils was measured over a 0-6% range of moisture content for sands and a 0-4% range of moisture content for gravels. Needle-plane electrode systems was used As a result, the conduction current prior to ionization growth in dry soil is a little, but it in wet soil is increased with the applied voltage because the wet soil particles act as conductors. The soil impedance curves show an abrupt reduction just after breakdown. The general tendency measured in different soils is that the higher the water content, the lower the breakdown voltage and the shorter the time-lag to breakdown.