• Journal of Korean Society of Environmental Engineers
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• v.32 no.4
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• pp.357-362
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• 2010

Electricity can be directly generated from organic matter even wastewaters using a microbial fuel cell. To achieve high power in MFCs, finding factors decreasing activation and Ohmic losses is very important. In this study we determined activation loss at the anode and cathode and Ohmic loss using the current interruption technique in a H-type MFC. Activation loss at the cathode was four times higher that that of anode activation loss even if pt-coated carbon (0.5 $mg/cm^2$;10%Pt) was used as the cathode. Ohmic loss determined using current interruption technique (1146 ${\Omega}$) was almost same as the internal resistance (1167 ${\Omega}$) measured using AC impedance. The sum of activation losses at the anode and cathode was the same as the value of activation loss of the cell.

• Progress in Superconductivity and Cryogenics
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• v.19 no.4
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• pp.40-44
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• 2017

This paper analyzed the fault current limiting characteristics of the previously proposed transformer superconducting fault current limiter (TSFCL) interruption system according to its transformer type. The TSFCL interruption system is an interruption technology that combines a TSFCL, which uses a transformer and a superconductor, and a mechanical DC circuit breaker. This technology first limits the fault current using the inductance of the transformer winding and the quench characteristics of the superconductor. The limited fault current is then interrupted by a mechanical DC circuit breaker. The magnitude of the limited fault current can be controlled by the quench resistance of the superconductor in the TSFCL and the turns ratio of the transformer. When the fault current is controlled using a superconductor, additional costs are incurred due to the cooling vessel and the length of the superconductor. When the fault current is controlled using step-up and step-down transformers, however, it is possible to control the fault current more economically than using the superconductor. The TSFCL interruption system was designed using PSCAD/EMTDC-based analysis software, and the fault current limiting characteristics according to the type of the transformer were analyzed. The turns ratios of the step-up and step-down transformers were set to 1:2 and 2:1. The results were compared with those of a transformer with a 1:1 turns ratio.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2146-2156
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• 2017

When a failure occurs in active distribution system, it will be isolated through the action of circuit breakers and sectionalizing switches. As a result, the network might be divided into several connected components, in which distributed generations could supply power for customers. Aimed at decreasing customer interruption cost, this paper proposes a theoretically optimal island partition model for such connected components, and a simplified but more practical model is also derived. The model aims to calculate a dynamic island partition schedule during the failure recovery time period, instead of a static islanding status. Fluctuation and stochastic characteristics of the renewable distributed generations and loads are considered, and the interruption cost functions of the loads are fitted. To solve the optimization model, a heuristic search algorithm based on the hill climbing method is proposed. The effectiveness of the proposed model and algorithm is evaluated by comparing with an existing static island partitioning model and intelligent algorithms, respectively.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.3
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• pp.163-168
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• 2014

In this paper, when photovoltaic systems are connected to distribution system, most effective capacity and location of PV system are studied considering customer interruption costs of power distribution system. The reliability model of PV system considering the duration of sunshine, the model of time-varying load and Roy Billinton test system (bus2 model) are used. To simulate the effects of PV system, various cases are selected; (1) base case which is no connection of PV system to power distribution system when faults are occurred, (2) 3MW case which is 3[MW] connection of PV system (3) 4[MW] case, and (4) 20[MW] case which is 20[MW] connection of PV system to the bus of power distribution system. The capacity limit of connected PV system is settled to 14[MW] for all cases except case 4. The reliability and customer interruption costs for residential, general, industrial, and educational customer is evaluated.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.8
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• pp.81-86
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• 2007

This paper proposes the scheme to improve the current direct load control(DLC) program by inspecting the problems of the DLC program. In order to increase the number of the customers participating DLC program, a reduction of the base incentive and an increase of the direct load control incentive are suggested based on the interruption cost of electric power considering the characteristics of load types and the introduction of demand side bidding is recommended. Secondly, the standards of power system operations is required to control DLC program efficiently for the penalty, interruption times, the number of interrupting loads, notice time for the load interruption and the periods of the DLC program contract.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.11
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• pp.519-526
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• 2005

This paper presents computer simulation results for developing new type of SF$_{6}$ Circuit Breaker in terms of cold gas flow after small current interruption. This cold gas flows down a nozzle into the chamber of a circuit breaker. There are many difficult problems in analyzing the gas flow due to complex geometry, moving boundary, shock wave and so on. When predicting the dielectric capability of a gas circuit breaker after interruption, the gas pressure and density distributions due to the cold gas must be considered in addition to the electrical field imposed across the gas. A self-coded computational fluid dynamics (CFD) program is used for the simulation of cold gas flow in order to evaluate the electrical field characteristic across open contacts and transient characteristics of insulations after small current interruption.

• Journal of Families and Better Life
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• v.29 no.1
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• pp.21-40
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• 2011

This research is intended to find out the causes of the career interruption of highly-educated housewives, their experiences of caring for their children after career interruption, their psychological conflicts and coping strategies, and their attitudes toward reemployment. The participants were university-graduated housewives in their thirties who have pre-school children older than 2 years. The participants in this research consisted of twenty-nine participants. The essence of this study is the belief system that career and maternal roles are not compatible. Specifically, the participants possessed a certain motherhood ideology, so they gave up working in order to care for their children, deferring their careers for a while. The participants had ambivalent feelings about working mothers, and described their children by highlighting their negative aspects. Additionally, the participants experienced persistent conflicts about developing their careers and caring for their children during their period of career interruption. The participants seemed to possess a vague sense of hope about their careers, and their attitudes toward their careers were ambiguous in the past, present, and even in the future.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1159-1164
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• 2018

Vacuum circuit breakers(VCB) are widely used for current interruption of high-voltage inductive loads such as induction motors. This VCB can be chopped off before the current zero due to its high arc-extinguishing capability. One of the outstanding features of VCB is that it can cut off high frequency re-ignition current more than other circuit breakers. If the transient recovery voltage generated in the arc extinguishing is higher than the dielectric strength of the circuit breaker, a re-ignition phenomenon occurs. The surge voltage of the re-ignition is very high in magnitude and the steepness of the waveform is so severe that it can act as a high electrical stress on the winding. If the high frequency current of one phase affects the other two phases when the re-ignition occurs, it may cause a high surge voltage due to the virtual current chopping. If the magnitude of the voltage allowed in the motor winding is high or the waveform level is too severe, it may lead to insulation breakdown. Therefore, it is necessary to reduce the voltage to within a certain range. In this study, we briefly explain the various phenomena at the time of interruption, analyzed the magnitude of the dielectric strength and the transient recovery voltage at the simultaneous three-phase interruption that can give the greatest influence to the inductive load, proposed a method to reduce the impact.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.365-369
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• 2006

It is concentrated on a methodology to establish a scheme of investment on power distribution systems of components. This paper provides a methodology to estimate the scheme as using a customer interruption cost regarding reliability indices in power distribution systems. The proposed method basically uses the failure rate depending on time for explaining the deterioration of a component. Therefore, the theory of the sensitivity is used for deciding the precedence of the investment to consider an effect of each component's failure rate on the system reliability. After Estimating the sensitivity on component investment cost making incremental reliability level is produced by component's investment cost accumulated according to the precedence of the sensitivity. After that, the failure rate corresponding with reliability level on the curve of investment cost is used as producing the curve of customer interruption cost. Two curves have the crossing point that is proposed to acceptable reliability level for customer and utility. In this paper, the acceptable reliability level for customer with the utility is assessed to analyze customer interruption cost and sensitivity of reliability indices. In conclusion the result of investment based on this method is shown to the reliability level with two cost.

• Resources Recycling
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• v.30 no.5
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• pp.3-9
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• 2021

In Korea, base metals such as lead, zinc, copper, tin, nickel, and aluminum have a polarized supply and demand structure. Despite the presence of world-class producers of lead, zinc, and copper, and their production is insufficient. And there are no domestic producers of tin, nickel, and aluminum, Thus, most of the domestic demand is dependent on imports. Therefore, it is necessary to prepare for the risk of supply interruption, such as the disruption of the import of base metals or interruption of domestic production. In this study, we estimated the quantity required to respond to the risk of import disruption, the quantity to which the market can respond, and the quantity to which the government needs to respond for six base metals (copper, lead, zinc, aluminum, nickel, and tin).