• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.5
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• pp.79-84
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• 2012

As the huge economical loss and function paralysis of information technology-based systems can be caused by the misoperation of residual current devices(RCDs) due to surge voltages and currents, RCDs shall not operate by surge currents. In this paper, in order to evaluate the reliability of residual current operated circuit-breakers with integral overcurrent protection for household and similar uses((RCBOs) stressed by surges, the unintended trip characteristics of RCBOs under surge currents were experimentally investigated using the combination wave generator. Seven different types of single-phase RCBOs being present on the domestic market were investigated according to KS C IEC 61009-1 standard. As a result, all kinds of specimens were satisfied the requirements for 0.5 [${\mu}s$]/100[kHz] ring wave impulse currents. Most of specimens stressed by the 8/20[${\mu}s$] impulse current tripped at least one or more, and some of them were broken down during consecutive tests. It was found that only one type of specimens meets the L-N mode immunity to the combination wave of 1.2/50[${\mu}s$] impulse voltage and 8/20[${\mu}s$] impulse current.

• Journal of the Korea Convergence Society
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• v.10 no.2
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• pp.201-206
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• 2019

The flooding and overtopping due to unexpected large ocean wave may occur serious problems to environments and structures. Generally fixed wave breakers and several structures were installed to prevent such damages, however, they may affect to environments and charted path of ships badly. In this regard, new type of initial wave breaker was investigated in both of experimentally and numerically. For the experiments, conceptual devices were built by authors with stereo vision system. The moving particle semi-implicit method was adopted for simulation. It is revealed that the initial wave breaker reduce the damages from ocean waves by energy dissipated earlier. Furthermore, the effects of position of the initial wave breaker was also considered.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.4
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• pp.525-532
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• 2010

In this paper, wave breakers which occur in two dimensional coasts are simulated using a SPH(Smoothed Particle Hydrodynamics) method which represents the movement of fluidic physical volume with particles. As continuative fluid is approximated to the particles, the simulations are performed using fully Lagrangian method without any grid system. Two-dimensional Navier-Stokes equations and continuity equation are used for the numerical simulations. To generate incident waves, a piston type wavemaker is employed. The accuracy of the wave which is numerically generated by the wavemaker is verified by comparing with analytical results. The computations are carried out with various wave heights and slopes. The wave patterns generated through the numerical simulations are compared with several existing experimental and computational results. Agreement between the experimental data and the computation results is comparatively good. Also, the breaker depth index and the breaker height index from the present calculations are compared with the existing experimental results, and the tendency is very similar.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.2
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• pp.87-94
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• 1999

The Morison's formula has been commonly used in the determination of wave forces of sinusoidal waves acting on coastal or ocean structures of pile-supported type. In the case that plunging breakers are incident, the structures are subjected to impulsive breaking wave forces which are normally much larger than the Morison's. However, the impulsive breaking wave forces act in a very short time, and hence a dynamic structural analysis should be done to determine whether or not to include the forces in the design force items. In the present study, numerical methods for calculating the dynamic response of a vertically located cylindrical pile are developed. Static and dynamic displacements are then compared through several example analyses varying the structural properties of pile.

• 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 Ocean Engineering and Technology
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• v.24 no.1
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• pp.106-115
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• 2010

This study described the stability of riprap, which was examined by a two-dimensional physical model of a scattered riprap submarine breakwater. Artificial reef structures made of scattered riprap are used like artificial intertidal zone structures as waterfront seaside structures. To prevent topography change in such an artificial intertidal zone the energy is reduced at the scattered riprap submarine breakwater by intercepting high waves. The breaking waves are converted into flow on the front surface slope of the submarine breakwater, which follows the upper part of the artificial intertidal zone. Because of this phenomenon of resisting water flow, it is very important to calculate the required weight of the riprap to maintain its stability. The results of a physical model can be abstracted as shown below. First, distribute the wave breaking types occurring on the front surface slope of the submarine breakwater and arrange it in relation to the movement of riprap. Second, using the hydraulic phenomenon that occurs at the depth of the scattered riprap submarine breakwater, propose a calculation formula for the velocity distribution showing the influence on the stability of the riprap. Third, propose and compare values, which can be obtained by experiments and calculations for riprap stability on the front surface of the artificial intertidal zone. Fourth, calculate the required weight for riprap stability.