• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.4
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• pp.387-394
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• 2009

Marine algal flora and community structure were examined seasonally at four study sites around Taean Power Plant, Korea from Jan. to Nov. 2006. A total of 73 algae species (12 green, 9 brown, 52 red) and 1 marine plant were identified. The number of species was maximal at the power plant Discharge (57 species) site followed by Hakampo (46 species), Intake (28 species) and Breakwater (15 species) sites during the study period. The average biomass in dry weight varied from 13.12g/m2 at Intake to 69.60g/m2 at Hakampo. Dominant and sub dominant species in terms of biomass were Gelidium divaricatum - Ulva pertusa at Intake, Chondria crassicaulis - Ulva pertusa at Discharge, Corallin a pilulifera - Chondrus ocellatus at Breakwater, and Corallina pilulifera - Sargassum thunbergii at Hakampo. Species richness of warm tolerant and green algae were greater at Discharge site than Hakampo, showing similar species richness. However, community indices were not distinguishable between Discharge and other study sites. In conclusion, species richness and biomass of seaweeds were greater at Discharge site compared to intake and breakwater sites, and the abundance of warm tolerant and green algal species were higher than Hakampo.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2345-2348
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• 1999

Existing $\psi$-AEA-t (phase-AEA-time) characteristic in polymer materials for power cable is good in general deterioration characteristic according to time variation, but it is difficult to clearly distinguish from deterioration state and diagnosis of deterioration is not enough to some extent. This paper is interpreted AE discharge statistics quantities measuring phase-amplitude variation of acoustic emission characteristic obtained from treeing breakdown experiment. Besides it can know useful discharge statistics quantities (AE average inception phase/amplitude, AE average maximum phase/amplitude) about so many for diagnosis of treeing deterioration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.199-202
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• 1998

Power capacitors are highly reliable equipment due to their completely enclosed configuration. Aging diagnosis system using partial discharge(PD) and acoustic emission(AE) is being highlighted as a research area for degradation of power capacitors. Their dielectric strength can be however reduced due to some stresses such as over-voltage or thermal degradation of the insulation material during their long period of operation. In this paper, it has been developed to express the AE of the EVENT(average amplitude) and HIT(pulse count) according to the source location. And real time measurement of PD signals for aging diagnosis of power capacitors.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.1
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• pp.10-14
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• 2003

The occurrence of partial discharge (PD) in solid dielectrics is very harmful because it leads to the deterioration of insulation by electrical, chemical, and thermal reactions as a combined action of the discharged ions bombarding the surface and by the action of chemical compounds that are formed by the discharge. Consequently, if any defects are present in the solid insulation system, performance decreases until the system breaks down. Therefore, removing or suppressing the defect is very important. Voids are a typical defect in the solid insulation system and are very harmful because they deteriorate insulation. As a basic step, studying the properties of PD in voids is important because an accurate knowledge of these properties is required to estimate the deterioration of voids. In this paper, the correlation between the size of voids and internal PD is discussed as a function of the time of the applied voltage and its magnitude. Magnitude, repetition rate, average discharge power, and average discharge current of PD in specimens with large voids were found to be larger than the others in this experiment. The smaller specimens had voids when the magnitude and number of PDs were reduced.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.246-248
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• 2002

This paper presents a high-frequency voltage source inverter for silent corona discharge ozonizer application, which is characterized by the power control based on pulse density modulation (PDM). The PDM inverter produces either a square -wave ac-voltage state or a zero-voltage state at its ac terminals to control the average output voltage under constant do voltage and operating frequency. This results in a wide range of power control in the silent corona discharge load with a strong nonlinear characteristics. And proposed addition circuit for maintain discharge on the center of the airgap. In this paper, schemed equivalent electric circuit of the discharge electrode for simulation. Finally, the effectiveness of this discharge tube character of silent corona ozonizer is investigated in the simulation results.

• Journal of IKEEE
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• v.28 no.2
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• pp.131-135
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• 2024

In this study, the sensor such as current transformer type was developed for measuring non-contact partial discharge in power electrical facilities, and the results of the characteristic evaluation were discussed. The frequency response characteristics of the HFCT sensor were shown to be measurable from 20 [kHz] to 20 [MHz]. The average sensitivity for the positive direction was 0.308 [mV/pC], and the negative direction was 0.459 [mV/pC]. Which showed that the sensitivity for the negative direction was better than that for the positive direction. The developed HFCT sensor is possible to measure very small partial discharge pulse signals and can be measured various types of partial discharge that may occur at power electrical facilities.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.293-296
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• 1998

Surface electrical conduction in insulator is most important factor to assess the insulation performances of outdoor insulating materials. In this paper, contamination performance of the widely used materials for outdoor insulator - porcelain, EPDM, Silicone rubber - were discussed by measuring properties of average leakage current and scintillation discharge pulses under artificial contamination conditions. The artificial contaminations used were deionized distilled water fog, 0.5wt% NaCl salt fog of light pollution and 2wt% NaCl salt fog of medium pollution. The average leakage current was appeared linearly with applied voltage at dry and clean surface condition. The magnitude of leakage current was almost same at different kinds of samples. In case of deionized distilled water fog, the characteristics of leakage current and applied voltage was most different to that in case of dry and clean condition. In case of salt fog pollution condition, The leakage current was increased above critical voltage. The scintillation discharges were also activated at the level. the leakage current and scintillation discharges were increased with increasing pollution degree. The resistance to pollution properties of silicone rubber appeared excellent among them.

• Journal of Electrical Engineering and information Science
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• v.1 no.2
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• pp.45-51
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• 1996

This paper presents a neural network approach for on-line estimation of partial discharge(PD) location using advanced correlation technique in power transformer. Ultrasonic sensors detect ultrasonic signals generated by a PD and the proposed method calculates time difference between the ultrasonic signals at each sensor pair using the cross-correlation technique applied by moving average and the Hamming window. The neural network takes distance difference as inputs converted from time difference, and estimates the PD location. Case studies showed that the proposed method using advanced correlation technique and a neural network estimated the PD location better than conventional methods.

• ALGAE
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• v.23 no.2
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• pp.151-162
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• 2008

Marine algal flora and community structure were seasonally examined at three sites in the vicinity of the Wolseong nuclear power plant in Korea from February to November 2006. A total of 126 seaweeds including 25 green, 31 brown, 70 red algae, and 1 marine plant were identified. The greatest number of species occurred at Jeonchonri (101 species) followed by intake (88 species) and discharge (29 species) during the study period. Of 126 seaweeds, 76 annuals and 13 warm tolerance species were recorded. Dominant species based on important value (IV > 10) were Ulva pertusa and Enteromorpha linza at intake, U. pertusa and Padina arborescens at discharge, and Sargassum horneri and Corallina pilulifera at Jeonchonri shore. Annual average biomass exhibited a wide range of variations, from 40.67g m-2 in dry weight at discharge to 133.69g m-2 at Jeonchonri. Among six functional groups, dominant group was coarsely-branched form at intake and Jeonchonri, but it was different at discharge site as filamentous form. Seaweed community structures of discharge site were distinguishable in decreasing species richness, biomass, species diversity index (H’), richness index (R), and evenness index (J’). Also, the ratios of green algae, warm tolerance species, annual algae, filamentous form and dominance index (DI) remarkably increased. Such phenomenons of discharge site are usually found under environmentally stressful conditions such as high disturbance. Thus, I can conclude that the heated effluents of nuclear power plant act as environmental stress influencing seaweed community structures and it can be detected with various community indices.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.118-126
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• 2003

In this study, a battery charge and discharge regulator of modular type is designed as paralleled bi-directional converter that is possible to provide the power without failure not only in the steady state but also in the transient period by the step load variation or the unexpected faults among the converter modules. Each converter module is designed to get stability, performance, reliability, and maintainability and the average current mode method used for controller has the advantages such as noise immunity, fast response, and the real average current signal acquisition. The equivalent model and small signal model for the paralleled battery chargerIdischarger are presented, and also the transfer functions are analyzed for the CCM(Continuous Charge Mode), CDM(Continuous Discharge Mode) and DDM(Discontinuous Discharge Mode). The experiments of the paralleled bi-directional converter are carried out in the step load variation, and in faults of one converter module respectively. And the performance of paralleled bi-directional converter is verified via the experimental results.