• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.1047-1051
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• 2004

Charge amplifier systems benefit from the very wide dynamic range of PE accelerometers by offering flexibility in adjusting the electrical output characteristics such as sensitivity and range. They are well suited for operation at high temperatures. Modern charge systems feature improved low noise operation, simplified digital controls, and dual mode operation for operation with charge or IEPE voltage mode sensors. high impedance circuitry is not well suited for operation in adverse field or factory environments. The resolution of a PE accelerometer may not be specified or known since noise is a system consideration determined by cable length and amplifier gain. IEPE accelerometrs operate from a constant current power source, provide a high-voltage, low-impedance, fixed mV/g output. They operate through long, ordinary, coaxial cable in adverse environments without degradation of signal quality. They have limited high temperature range. IEPE sensors are simple to operate. Both resolution and operating range are defined specifications. Cost perchannel is lower compared to PE systems since low-noise cable and charge amplifiers are not required.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.325-332
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• 1999

As part of the conceptual disign of cable and membrane structures, the adequate shape is decisive with respect to load bearing behaviour and aesthetic expression of the structure. The force densities which are the force-length ratio are very useful parameters for the description of equilibrium state of any general cable-net structures. Because equilibrium states are obtained by solving linear equations the force desity method has a advantage compared with other solution strategies. But if there are futher restrainted conditions in force density the linear method will be extended to nonlinear one. The numeriacl methods are based upon least square and general inverse method for sieving nonlinear eqations. In this paper, the results from two methods is compared through several examples.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1972-1974
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• 2000

In this paper, we made an experiment on fault location of underground cables with travelling wave. The 5C2V coaxial cables of 100, 200m length, connected with discharge gap, are used for simplifying model cable lines of power cable. And 100KHz -2MHz CT and HV probe are installed at one side of the ends. We made travelling pulse in discharge gab and then pulse travelled along the cable to the both ends. Therefore, it is detected in CT and HV probe. Measuring the time difference of the pulse start and arrival, we were able to obtain the distance of pulse travelling. Consequently, our experimental results show the possibility to detect fault location of underground cables with travelling wave.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.119-125
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• 2008

A new type of swivel unit is suggested in order to complement weak points of the existing. This new type of Swivel unit is developed by adopting a spring type cable which has elasticity and restoring force. To minimize the troubles in the process of manufacturing during operating the new type system, strength analysis and the check of interference between parts are accomplished with CATIA. The check of rotating performance is also carried out to determine the diameter and length of spring type cable by SimDesigner motion analysis. Swivel unit used in the robot spot welding is developed with spring type cable and its usefulness in the industrial field is verified through experiments. This system has been registered for patent.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.274-277
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• 1994

This paper describes a very fast rising high voltage pulse generation for studying surge phinomenon and prebreakdown of liquid dielectric by appling the traveling wave theory of the distributed circuit. This very fast rising high voltage pulse generator consists of a charging coaxial cable, a discharging switch, and a terminating resistance. As results, the rising time of pulses are about 31(nsec), which is very fast, and its duration is 950[nsec] when using 200[m] coaxial cable. The length of the coaxial cable and changing voltage can regulate the duration and the amplitude or the polarity of the pulse. When terminated the resistance, capacitor and inductor, the measured waveform corresponds with simulated waveform.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.150-156
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• 2017

This study examined the stress recovery length due to the local damage of a 7-wire strand, which is applied widely to PSC (Post Tensioned Concrete) bridges and cable-stayed bridges. The 7-wire strand is a multiple stranded steel of PC prestressing strand. Owing to the nature of the material, it is damaged continuously after completion with corrosion being the main cause of damage. On the other hand, due to its structural characteristics, it is difficult to grasp the degree of damage inside the cable and the pattern of stress variation. In the case of cables applied to bridges, the parts that are susceptible to corrosion are generated depending on the water supply and installation shape, which may cause local damage. This study analyzed the tendency of performance degradation and stress recovery length according to local damage of a 7-wire strand, which is applied mainly to bridge post-tensioning or stay cables. This study developed a computer-based simulation model that was validated with experimental results. The model developed in this study can be used to evaluate the safety level and estimate the remaining life span of P SC bridges or cable-stayed bridges.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.8 no.3
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• pp.96-104
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• 1983

In wire transmission systems using a coaxial cable or cable pair, the cable loss caused by the transmission characteristic of the cable varies depending on the length of the cables or variation in the ambient temperature, and usually takes the form close to a $\sqrt f$ characteristic. In order to compensiate for such loss, an actove variable automatic equalizer with a tandam combination of feedback and feedforward was presented. The automatic equalizer to be described here overcomes many of the disadbantages associated with the conventional passive variable equalizers, which include the need for inducters, a complex design procedure, and incompatibility with modern dldctronic control systems that are very complicated. This design has advanatges over other active variable equalizer design and it is especially applicable to precision equalization at frequencies bellow 1MHz.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.10
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• pp.1761-1769
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• 2010

This paper describes switching surge analysis on reclosing decision in 154kV combined transmission line with power cables. Reclosing should be operated in combined transmission line based on the technical evaluation because of insulation problem of power cable section. If the surge strikes on power cable, the breakdown can occur at week point of cable insulation. Therefore the detailed analysis is required by considering several conditions such as length ratio of power cable, arrester, fault resistance, charging rate and grounding resistance, etc.. In addition, sheath voltage on IJ(Insulated Joint) is analyzed to confirm the protective level. Simulation is performed by EMTP/ATP. Analysis results show that reclosing can be operated without any special problem by the single line-to-ground fault with fault resistance of $1\Omega$ to $50\Omega$ occurred at the overhead transmission section in 154kV combined transmission lines and trap charge of 100% and 110%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.3
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• pp.273-279
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• 2006

High-$T_c$ superconducting (HTSC) power cable is one of the interesting parts in power application using HTSC wire. However, its stacked structure makes the current distribution between conducting layers non-uniform due to difference between self inductances of conducting layers and mutual inductances between two conducting layers, which results in lower current transmission capacity of HTSC power cable. In this paper, the transport current distribution between conducting layers was investigated through the numerical analysis for the equivalent circuit of HTSC power cable with a shield layer, and compared with the case of without a shield layer. The transport current distribution due to the increase of the contact resistance in each layer was improved. However, its magnetization loss increased as the contact resistance increased. It was confirmed from the analysis that the shield layer was contributed to the improvement of the current distribution between conducting layers if the winding direction and the pitch length were properly chosen.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.894-901
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• 2006

In general, the tension fores of hanger cable in suspension bridges play an important role in evaluating the bridge state. The vibration method, as a conventional one, has been widely applied to estimate the tension fores by using the measured frequencies on hanger cables. However, the vibration method is not applicable to short hanger cables because the frequency of short cables is severely sensitive to the flexural rigidity. Thus, in this study, the tension forces of short hanger cables, of which the length is shorter than 10meters, were estimated through back analysis of the cable frequencies measured from Gwang-An suspension bridge in Korea. Direct approach to rock analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method is able to search the optimal tension forces without regard to the initial ones and has a rapid convergence rate. To verify the feasibility of back analysis, the results from back analysis and vibration method are compared with the design tension forces. From the comparison, it can be inferred that back analysis results are more reasonable agreement with the design tension forces of short hanger cable. Therefore, it is concluded that back analysis applied in this study is an appropriate tool for estimating tension forces of short hanger cables.