• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.3
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• pp.197-201
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• 2017

The demand for electric power is increasing every year in Korea. All the systems adopted at power stations in order to generate and transmit electric power should operate in perfect condition or reliability. The device for transmitting the generated high-voltage electric power is 6 kV CV single core cables. The manufacturing companies of the cables makes an official announcement that the operating lifetime of their cables is about 30years. But from the moment of operation the deterioration precesses of worsening the characteristics of cables starts. Since the reliability for the status of installed cables in deterioration has not been diagnosed, the cables can be broken at any unexpected moments. In order to prevent the abrupt cable accident by systematically monitoring the cable status, we have invented the first device in Korea. We have installed our device at Korea Western Power Co. Ltd. in order to diagnose the live cables. In this paper, we present our research results of measured temperatures of inner conductor and surface and the compared results of those data with other cable company. We also show that our results agree with those made by other company.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.9
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• pp.1644-1651
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• 2010

VLF $tan{\delta}$ diagnosis technology is introduced in IEEE Std 400 and proposed as evaluation criterion in an effective way of detecting water tree which mainly causes the failure of XLPE insulated cables. In order to inspect the accuracy of the VLF $tan{\delta}$ method for XLPE insulated power cables in Korean distribution system, diagnosis for 41 cables which were being serviced in the fields has been carried out and they were removed for AC breakdown voltage test after. Regarding the 41 cables, it was hard to confirm any relation between the VLF $tan{\delta}$ values and AC breakdown voltages and also water tree in the insulation was not detected. However, the other cables were failed several days after the diagnosis of the 41 cables. Water trees were found and their VLF $tan{\delta}$ values were also much higher than the criterion of IEEE standard. It has been ascertained that we need to change the IEEE criteria in order to improve the accuracy of detecting water trees by additional analyzing of field examples of failure and case studies from overseas countries and therefore amended VLF $tan{\delta}$ test voltage and evaluation criteria have been proposed.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.502-505
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• 2004

The purpose of this experiment is to modify diagnosis criterion of isothermal relaxation current(IRC) measurement equipment which is using for distribution cable diagnosis. We're using this system for several years in the field instead of DC leakage current measurement and lots of cables were replaced. But we have to investigate on the reliability of this equipment for our cables because we didn't carried out condition assessment of extracted cables after field diagnosis by this equipment. It is important thing for cable maintenance. If the replacement criterion is improper we can not prevent failures or will waste budget on account of replacement of the sound cables. In this papar we selected field installed cables and injected silicone fluid to the cables for insulation rehabilitation. In order to prove reliability of the diagnosis equipment we compared diagnosis results and AC breakdown strength according to operating time after silicone treatment. This is the results of the field test for 1 year.

• Wind and Structures
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• v.23 no.3
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• pp.253-273
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• 2016

Ice accretions on stay cables may result in the instable vibration of galloping, which would affect the safety of cable-stayed bridges. A large number of studies have investigated the galloping vibrations of transmission lines. However, the obtained aerodynamics in transmission lines cannot be directly applied to the stay cables on cable-stayed bridges. In this study, linear and nonlinear single degree-of-freedom models were introduced to obtain the critical galloping wind velocity of iced stay cables where the aerodynamic lift and drag coefficients were identified in the wind tunnel tests. Specifically, six ice shapes were discussed using section models with geometric scale 1:1. The results presented obvious sudden decrease regions of the aerodynamic lift coefficient for all six test models. Numerical analyses of iced stay cables associated to a medium-span cable-stayed bridge were carried out to evaluate the potential galloping instability. The obtained nonlinear critical wind velocity for a 243-meter-long stay cable is much lower than the design wind velocity. The calculated linear critical wind velocity is even lower. In addition, numerical analyses demonstrated that increasing structural damping could effectively mitigate the galloping vibrations of iced stay cables.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1652-1656
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• 2022

Fire tests were conducted on cables using fire-retardant paint employed in nuclear power plants that transmit electrical power, control and instrument signals. The failure criteria of various power and control cables coated with fire retardant coating at three different coating thicknesses (~0.5 mm, 1.0 mm & 1.5 mm) were studied under direct flame test using Container Fire Test Facility (CFTF) based on standard tests for bare cables. A direct flame fire test was conducted for 10 min with an LPG ribbon burner rated at ten by fixing the cable samples in a vertical cable track. Inner sheath temperature was measured until ambient conditions were achieved by natural convection. The cables are visually evaluated for damage and the mass loss percentage. Cable functionality is ascertained by checking for electrical continuity for each sample. The thickness of cable coating on fire exposure is also studied by comparing the transient variation of inner sheath temperature along the Cable length. This study also evaluated the adequacy of fire-retardant coating on cables used for safety-critical equipment in nuclear power plants.

• Steel and Composite Structures
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• v.49 no.2
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• pp.125-141
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• 2023

Firstly, a new kind of prismatic tensegrity structures with redundant cables is defined, the topology, geometry and forming conditions of which are introduced further. The development of its mechanical properties including self-stress states and structural stiffness with the increment of the twist angle is also investigated carefully. Combined with the topology of this kind of structures, a reasonable erection scheme is proposed, in which some temporary lifting points need to be set and two groups of vertical cables are tensioned in batches. Then, a simplified dynamic relaxation method is employed to track the erection process inversely, which aims to predict each intermediate equilibrium state during the construction, and give the key structural parameters that can effectively guide the construction. The removal of the active cables, the relaxation or tension of the passive cables are simulated by controlling their axial stiffness, so that the structural composition as well as the serial numbers of the elements always keep invariant regardless of the withdrawal of the slack cables. The whole analysis process is clear in concept, simple to implement and easy to popularize. Finally, several examples are given to verify the practicability and effectiveness of the proposed method further.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.267-270
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• 2002

It is very important to analyze the superconducting power cables by the modeling for correct and reasonable cable design suitable for the domestic situation of power systems. This paper describes the basic modeling for superconducting power cables using ATPDraw. And also it is shown the line constants of cold dielectric coaxial type which is one of the HTS cables. It is compared with the line constants of general two kinds of power cables(OF, XLPE).

• Electrical & Electronic Materials
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• v.10 no.5
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• pp.447-452
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• 1997

Effects of metal impurities in insulation of distribution cables on electrical conduction of distribution cables was investigated. Samples of Al, Cu, Fe are fabricated as metallic impurities, and measured electrical conductivity in the voltage range of 0~10 KV. Temperature dependent effect of hysteresis curves and the relationship between forward and reverse current due to impurity content are discussed.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.257-260
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• 2006

This paper presents electromagnetic finite element analysis of power cables for wind turbine application. Eddy current losses are calculated due to high currents along metallic part, and dielectric strength on power cables is investigated for case study, which suggests the optimal cabling configuration for wind turbine construction.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.889-901
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• 2021

The tension of cables and motion response significantly affect safety of an immersed tunnel element in the immersion process. To investigate those, a hydrodynamic scale-model test was carried out and the model experiments was conducted under wind, current and wave loads simultaneously. The immersion standby (the process that the position of the immersed tunnel element should be located before the immersion process) and immersion process conditions have been conducted and illustrated. At the immersion standby conditions, the maximum force of the cables and motion is much larger at the side of incoming wind, wave and current, the maximum force of Element-6 (6 cables directly tie on the element) is larger than for Pontoon-8 (8 cables tie on pontoon of the element), and the flexible connection can reduce the maximum force of the mooring cables and motion of element (i.e. sway is expecting to decrease approximate 40%). The maximum force of the mooring cables increases with the increase of current speed, wave height, and water depth. The motion of immersed tunnel element increases with increase of wave height and water depth, and the current speed had little effect on it. At the immersion process condition, the maximum force of the cables decrease with the increase of immersion depth, and dramatically increase with the increase of wave height (i.e. the tension of cable F4 of pontoons at wave height of 1.5 m (83.3t) is approximately four times that at wave height of 0.8 m). The current speed has no much effect on the maximum force of the cables. The weight has little effect on the maximum force of the mooring cables, and the maximum force of hoisting cables increase with the increase of weight. The maximum value of six-freedom motion amplitude of the immersed tunnel element decreases with the increase of immersion depth, increase with the increase of current speed and wave height (i.e. the roll motion at wave height of 1.5 m is two times that at wave height of 0.8 m). The weight has little effect on the maximum motion amplitude of the immersed tunnel element. The results are significant for the immersion safety of element in engineering practical construction process.