• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.675-682
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• 2016

Sudden voltage drops and outages frequently disturb the operation of sensitive loads for domestic, commercial, and industrial use. In some cases, these events may even impair the functioning of relevant equipment. To maintain power under such conditions, a UPS system is usually installed. Once a disturbance happens at the grid side, the line-interactive UPS system takes over the load to prevent an interruption. But, due to magnetic saturation of the transformer, a significant inrush current may occur for the transformer-coupled loads during this transition. The generation of such transient currents may in turn decrease the line voltage and activates over-current protecting devices of the system. In this work, a cost-effective, line-interactive UPS system is proposed that eliminates the inrush current phenomenon associated with transformer-coupled loads. The strategy was implemented by connecting a standard current-regulated voltage source inverter (CRVSI) to the secondary winding of the load transformer. During any transient condition at the grid side, the load current is monitored and regulated to achieve either seamless compensation of the load current or complete transferal of load from grid to the inverter. Experimental results were obtained for a prototype under all possible operating conditions so as to validate the performance of the proposed topology.

• Fisheries and Aquatic Sciences
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• v.3 no.2
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• pp.156-162
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• 2000

Model experiments for a purse seine were carried out in order to measure the geometry of net shape and to estimate an enclosed volume by using 1177 scale model purse seine of 12.62m float line from an offshore mackerel purse seine. A model purse seine was set from a net box of shooting equipments and then pursing and hauling net by hauling equipment. The 3- D geometry shape of the purse seine net during hauling operation was measured by video image processing and tension of purse line by load cell. The 3-D geometry of the model purse seine during hauling operation could be represented with variables such as a ratio of shooting diameter or maximum net depth and a ratio of hauling operation time. Horizontal shapes of float line and lead line were varied from a circle after shooting to an ellipse with pursing and hauling. Projected lateral shape of purse line was observed and formulated as a shape of a water drop. The cross sectional shapes of curved net from two directions were varied such as sine function or polynomial curves. Therefore, enclosed volume of a purse seine in relation to fish school behaviour can be approximated using two main variables from relevant equations.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1255-1260
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• 2008

This study is simulation of high elevated liquid line of a modular heat pump system to observe longitudinal subcooling variation. In a high elevated tube, subcooled refrigerant(R410A) through a condenser changes its states by heat transfer with surrounding air and by pressure drop from elevation. In this study, the liquid line was simulated through correlations of heat transfer and pressure drop for the variation from single-phase into two-phase flow. Pressure drop, heat transfer rate and vapor quality were calculated as key parameters. Two-phase turning heights and variations of the key parameters were confirmed from the simulation. As a result, high elevation of liquid line has great influence on upward flow, which requires additional equipment to compensate the variation.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.276-278
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• 2000

In KwangYang steel works power system operation, the ON-LINE application of power system diagnosis technology is indispensable to not only power quality, but also stable operation and economical generation. In cases of stability constraint violation. stable power system operation is obstructed. Steel works power system is consist of 154kV transmission lines, and 345, 154, 22, and 6.6[KV] distributed lines, 5 numbers of substation, 17 units of generators. For this power system operation. loadflow program is developed. Database is tied with Windows GUI application, is designed, and is interfaced with this program. This program put up with loadflow solution of assembled MMI power system, and planed to diagnose of overloads or to imitate entrance, and isolation of equipment.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.1-5
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• 2014

When renewable sources are connected to the distribution network in the form of a distributed generators(DGs), the effect of intermittent output appears as voltage fluctuation. The surplus power at the consumer ends results in the reverse power flow to the distribution network. This reverse power flow causes several problems to the distribution network such as overvoltage. Application of the reactive power control equipment and power flow control by means of BTB inverter have been suggested as the general solutions to overcome the overvoltage, but they are not economically feasible since they require high cost devices. Herein, we suggest the feeder loop line switch control method to solve the problem.

• Journal of the Korean Solar Energy Society
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• v.23 no.4
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• pp.1-9
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• 2003

In this study, a manufacturing process for PV module has been developed using an automatic arraying equipment. It is expected that this process could improve the productivity and curtail the production cost in the photovoltaic module production line. From the results, it is proved that this process reduces Line-stop and enhances the productivity more than 15% a day which can be related directly to the production line cost.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.1954-1961
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• 2009

This paper describes the development of a three-phase line-interactive dynamic voltage restorer with hybrid detection method, which is composed of three H-bridge inverter modules and super-capacitors. The operational feasibility was verified through computer simulations with PSCAD/EMTDC software, and experimental works with a 3kVA prototype. The developed system can compensate the input voltage sag and interruption within 2ms. The maximum allowable duration of voltage interruption is about 4 seconds. The developed system can be effectively used to compensate the voltage interruption in the sensitive load, such as computer, communication devices, and automation devices, and medical equipment. The developed system has a simple structure to be easily implemented with commercially available components, and to be highly reliable in operation.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.190-195
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• 2008

Surge proof equipment is an installation to make surge flow on the ground promptly so as to reduce surge-related damage on infrastructure, not to prevent surge from falling down on infrastructure directly. Compared with classical line individual earth, High speed line common earth has higher surge characteristic and plays a significant role to prevent infrastructure damage and injuries from surge, or short circuit accident between 25kV catenary and rail. In this paper, we analyzed the case of accident that caused communication/signaling system impaired while a tractor crossing level crossing at Honam line; in addition, we examined the accident reduction measures to minimize injury and property damage from cutting accidents with respect to common earth network.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1458-1464
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• 2007

Today, domestic and foreign manufacturing industries have to cope with obsolescence of manufacturing equipment because the shifting market trends drive the rapid changes in the production process resulting in stressful operation. Quality control process for manufacturing and production involves a familiar step - when the production process is completed, every item is subjected to various routine tests to determine that it meets the minimum quality standards. Typically, when a faulty product is found, the production line has to be stopped and the current batch is marked for further inspected and exhaustive testing. In this research, we propose a quality monitoring system for productivity enhancement. Our approach aims to reduces the operational down time in the production line of a car-component factory. The proposed monitoring system for productivity enhancement is designed to collect the data through testing at each phase of the assembly line and uses predictive methods on the collected data to achieve early detection of faults in the production process and minimize the number of products in a faulty batch thus minimizing the losses incurred from defective products. More importantly, this system aims to forecast and proactively detect faults and activate warnings when they are detected thus minimizing items in the defective batch, reducing the damage to manufacturing equipment and ultimately reducing the operational downtime or the delay in the resumption of normal factory operation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.67-74
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• 2010

Most of domestic low-voltage consumers are supplied from the TN-C system of KEPCO, but their load installations have established according to the national statutory standard for electrical installations based on the TT system. In this work, to propose the proper system earthing arrangements of ensuring the protection of information-technology equipment against lightning surges, the protection performance of TT and TN systems against lightning surges was investigated. As a result, when lightning surge was injected to the neutral line of distribution system, the potential difference between the equipment earth terminal and neutral point of low-voltage mains in a TT system was significantly raised. The TT system is not advised due to the risk of damage to the sensitive computer equipment. Main equipotential bonding is an important requirement for protection of low-voltage installations against lightning surges. The TN system provides the best means to reduce the incoming lightning surges through the neutral line of low-voltage service systems. In addition, It is highly recommended to install the additional earthing at the service position of low-voltage consumers.