• 상하수도학회지
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• 제26권3호
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• pp.409-421
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• 2012

Ethanolamine (ETA) is mainly used to prevent corrosion of pipe in secondary cooling system of nuclear power plant. Condensed ETA in wastewater could increase COD and T-N when it was emitted to natural water system. Compared to conventional treatments, electrochemical oxidation process using packed bed bipolar electrodes was adopted to treat COD and T-N. According to arrangement of feeder electrode, single packed bed bipolar electrode reactor and multi-paired packed bed bipolar reactor were developed and conventional zero-valent iron (ZVI) was selected as conducting bipolar electrode. Bipolar electrodes were coordinated three-dimensionally in the reactor. The experimental results showed that COD and T-N was little removed in unit system at different pH condition (pH 8 and 11) on 100V. However, in multi-paired system that applied 600V, COD was eliminated 80.85% (anode-cathode-anode, A-C-A) and 85.11% (cathode-anode-cathode, C-A-C), respectively. T-N was also removed 96.88% (A-C-A) and 90.63% (C-A-C), simultaneously. Current efficiency was estimated both single and multi-paired system. At unit bipolar packed bed reactor, current efficiency was almost zero, however in multi-paired system, current efficiency was 300~500% at A-C-A and 250~350% at C-A-C. Current efficiency was over 100% hence it was confirmed that this system is more effective than conventional electrochemical oxidation system.

• Journal of Biosystems Engineering
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• 제32권6호
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• pp.455-461
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• 2007

The electric current of a flow injection type enzyme-sensor was measured to confirm the stable operating conditions of the sensor. The current of the sensor was decreased as the buffer solution velocity increased. Under the limitation of the cycle time to be below 10 minutes, the effective ranges of the buffer solution velocity were suggested $0.10{\sim}0.26$, $0.12{\sim}0.24$, $0.1{\sim}0.25$ and $0.05{\sim}0.10\;cm/s$ of 1.0, 1.4, 2.4 and 3.4 mm of the electrode diameters, respectively. As the reaction time of the enzyme and the substrate was increased, the current was decreased because of the dilution between the sample and buffer solution. Therefore, it could be recommended that the reaction time was able to be selected as shortly as possible in consideration of the total cycle time. As the result of the experiments using a different volume ratio of the enzyme to substrate, it was concluded that the substrate had to be mixed with the same amount of the enzyme. The current have increased remarkably in proportion to the electrode diameter under 0.1 cm/s of the buffer solution velocity but there was no difference over 0.1 cm/s of the buffer solution velocity. The cross type arrangement of the electrode was highly suggested for application and machining of the sensor.

• 조명전기설비학회논문지
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• 제27권8호
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• pp.83-89
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• 2013

In this paper, discharge characteristics of air in the vertical arrangement of three rods(dome-shaped, cylinder-shaped, and needle-shaped rod) and plane gap having propane flame on the plane electrode are examined under the application of a.c. and d.c. high-voltages. As the result of the experiment, flashover voltages in the presence of the flame are substantially lowered than those in the absence of flame, and relative a.c. flashover voltages in the dome-shaped, cylinder-shaped, and needle-shaped rod gaps are found 32.5%, 32.1%, and 26.4% respectively. The polarity effects with the d.c. voltages are shown, and flashover voltages in negative polarity are much lowered than those in positive one. The negative flashover voltages in the dome-shaped and cylinder-shaped gaps are found 18.3% and 18.7% respectively, but the positive ones are found 53.5% and 43.2% respectively. In the needle-shaped rod gaps, meanwhile, the flame is extinguished by corona wind, and the quenching voltages are found 28.4% under the application of a.c. voltages. The ion winds of corona and the reduction of air density are the main factors of flashover reduction owing to the flame in the case of a.c. voltages, but the electrifications of the positive ion by thermal ionization besides the above factors are remarkably found in the case of d.c. voltages.

• 전기학회논문지
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• 제62권11호
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• pp.1571-1577
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• 2013

Electrical tree structure is one of the most important influencing factors for electrical treeing characteristics in polymers. In this paper, we focused on the structure characteristics of electrical treeing in epoxy resins (original) insulation under different high-frequency voltages (60, 500, 1000Hz). Effects of voltage frequency on the ac electrical treeing phenomena in an epoxy resins were carried out in needle-plate electrode arrangement. To measure the treeing initiation and propagation, and the breakdown rate, constant AC of 10 kV with three different voltage frequencies (60, 500 and 1,000 Hz) was applied to the specimen in needle-plate electrode specimen at $30^{\circ}C$ of insulating oil bath. At 60 Hz, the treeing initiation time was 360 min and the propagation rate was $6.85{\times}10^{-4}mm/min$, and the morphology was dense branch type. As the voltage frequency increased, the treeing initiation time decreased and the propagation rate increased. At 1,000 Hz, the treeing initiation time was 0 min and the propagation rate was $7.81{\times}10^{-2}mm/min$, and the morphology was dense bush type.

• Transactions on Electrical and Electronic Materials
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• 제15권2호
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• pp.77-80
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• 2014

The effect of reactive diluents on the ac electrical treeing in epoxy/nanosilicate systems was studied, in a needle-plate electrode geometry. Diglycidyl ether of bisphenol A (DGEBA) type epoxy was used as a base resin, and layered silicate was used as a nano-sized filler. Polyglycol (PG) or 1,4-butanediol diglycidyl ether (BDGE) was introduced as a reactive diluent to the DGEBA/nanosilicate system, in order to decrease the viscosity of the nanocomposite system. PG acted as a flexibilizer, and BDGE acted as a chain extender, after the curing reaction. To measure the treeing propagation rate, a constant alternating current (ac) of 10 kV/4.2 mm (60 Hz) was applied to the specimen, in a needle-plate electrode arrangement, at $30^{\circ}C$ of insulating oil bath. When 10 kV/4.2 mm (60 Hz) was applied, the treeing propagate rate in the DGEBA system was $1.10{\times}10^{-3}$ mm/min, and that in the DGEBA/PG system was $1.05{\times}10^{-3}$ mm/min. As 1.5 wt% of nanosilicate was added to the DGEGA/PG system, the propagation rate was $0.33{\times}10^{-3}$ mm/min. This meant that the nano-sized layered silicates would act as good barriers to treeing propagation. The effect of chlorine content was also studied, and it was found that chlorine had a bad effect on the electrical insulation property of the epoxy system.

• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.2050-2058
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• 2018

Impulse characteristic of transmission tower grounding grid is needed for lightning protection of transmission line. This paper describes an outdoor experimental test facility established for large-scale grounding grid of transmission tower, made up of four impulse current generators and a circle current return electrode. The amplitude of impulse current is up to 100 kA. The results of the CDEGS simulation and GPR measurement reveal the uniform current distribution in the test arrangement. An impulse test for a square electrode with extended conductors is carried out in condition of three current waveforms with different amplitude. Based on the electrical network model and iterative algorithm method, a calculation model is proposed to simulate the impulse characteristic of large-scale grounding grid considering soil ionization. The curve of impulse resistance against the current amplitude shows the soil ionization both from the simulation and test. Deviation between the simulation and test result is less than 15%.

• 전기학회논문지P
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• 제63권4호
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• pp.301-306
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• 2014

Recently in accordance with the rapid development of the industrial society, the accidents caused by dielectric breakdown have been increasing in power grid. It is important to prevent the dielectric breakdown of a high voltage apparatus to reduce the damage from electrical hazards. To establish an electrically reliable database of insulation design criteria for high voltage apparatus, a study on dielectric characteristics test is indispensable. In this study, dielectric characteristics according to field utilization factors (${\xi}$) which are represented as the ratio of mean electric field to maximum electric field are investigated. the dielectric breakdown experiments by using several kinds of electrode systems made with stainless steel are performed by AC breakdown voltage under air-insulation. Also, the experimental results are analyzed by the Weibull distribution. As a result, it is found that the dielectric characteristics of air-insulation are determined by ${\xi}$ as well as arrangement of electrode systems. It is considered that the results of this study would be applicable to designing the air-insulated high voltage apparatuses.

• 한국주조공학회지
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• 제14권6호
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• pp.576-589
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• 1994

Water modeling experiments and computer simulation for the predictions of defects of die castings are very important to produce high quality castings with less cost. The relation between the variable air vent system and the characteristics of the fluid flow in the die cavity is studied by using water modeling tests, which give ideas on reasonable designing of die cavity, vent arrangement and gating system. In order to test the water modeling, injection is done by using water containing NaCl. Flow behaviors in cavities are visualized by high speed camera and video tape recorder, and local filling time is measured with electrode sensors. Special attention is paid to the configuration of die cavity. Simulated results by computer are examined and compared with the results of water modeling experiments. There are close correlations between the simulated results and water modeling ones.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기물성,응용부문
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• pp.205-207
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• 2001

This study is characteristic analysis to optimize triggering of a high-power trigatron by FEM which is used to analyse electric field distribution in the trigatron. Triggering characteristics of a trigatron depends on arrangement of voltage polarity applied on electrodes and configuration of electrodes. This study is the preliminary stage for an experiment and make it possible to experiment effectively by finding optimal triggering characteristics though 3-dimensional node-based FEM which can practically model the complex structured electrode system.

• 한국전기전자재료학회논문지
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• 제28권5호
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• pp.326-331
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• 2015

In this paper, we study the insulating properties of the liquid nitrogen(LN2) including the thermal bubbles. The shape of the thermal bubbles in accordance with the current change was observed in the 77 K and 65 K LN2. According to the temperature of liquid nitrogen, bubbles were generated differently. The round shape of the bubble is occurred in 77 K LN2. But the layer shape of bubble is occurred in 65 K LN2. When the bubbles present, the dielectric strength of liquid nitrogen is low. However, the breakdown patterns were different according to the electrode arrangement. AC breakdown voltage(BDV) was lower than the DC BDV due to the influence of bubbles. Therefore, the design of a high-voltage superconducting equipments should consider the bubbles.