• Journal of Broadcast Engineering
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• v.24 no.4
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• pp.670-675
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• 2019

AM radio broadcasting has the advantage that the sound quality is lower than that of FM radio but the service area is wide and at night it can be transmitted even to overseas due to ionospheric reflection. AM radio broadcasts usually transmit large amounts of several tens to several hundreds of kilowatts (KW), requiring a lot of power, which is a financial burden on broadcasters. Recently, it is required to introduce a way to reduce the power of AM radio broadcasting in Korea. Therefore, it is possible to save a certain amount of power compared to the conventional AM radio broadcasting, and it is possible to maintain the existing license service area and sound quality, and what policies are needed to introduce the technology. In this paper, we predict the reduction of transmission power when a high efficiency transmission system is applied to existing AM radio broadcasting transmission system. As a result of the research, AMC adopting the high efficiency transmission method instead of the conventional AM radio transmission method, and when the modulation ratio of AM radio is 70%, if -3 dB companding is applied, the annual transmission power charge is decreased from 5,185,838,160Won to 3,528,900,086Won with saving of 32.0%, When -6 dB companding is applied, it is expected to be reduced to 2,608,378,934Won, which is 49.7% savings.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1986.04a
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• pp.66-70
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• 1986

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.429-434
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• 2009

In this paper it was written about the safety management plan for underground power transmission cable, and it guarantees the reliable electric power supply and facility management to prevent an electric disasters according to that. Recently fires which happens on OF Cable lead to a breakdown of power system and cause a power outage of wide area and serious social problems. So it needs an improvement of inspection ability on OF cable as well as a strict inspection system to prevent that problems in advance and it will bring us the development of electric safety management and the reliable electric power supply.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2145-2157
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• 2018

Congestion Management (CM) is an attractive research area in the electrical power transmission with the power compensation abilities. Reconfiguration and the Flexible Alternating Current Transmission Systems (FACTS) devices utilization relieve the congestion in transmission lines. The lack of optimal power (real and reactive) usage with the better transfer capability and minimum cost is still challenging issue in the CM. The prediction of suitable place for the energy resources to control the power flow is the major requirement for power handling scenario. This paper proposes the novel optimization principle to select the best location for the energy resources to achieve the real-reactive power compensation. The parameters estimation and the selection of values with the best fitness through the Symmetrical Distance Travelling Optimization (SDTO) algorithm establishes the proper controlling of optimal power flow in the transmission lines. The modified fitness function formulation based on the bus parameters, index estimation correspond to the optimal reactive power usage enhances the power transfer capability with the minimum cost. The comparative analysis between the proposed method with the existing power management techniques regarding the parameters of power loss, cost value, load power and energy loss confirms the effectiveness of proposed work in the distributed renewable energy systems.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1647-1656
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• 2013

Although the demand for electricity has been increasing these days, it becomes more difficult to find new sites for large-scale power generation plants near urban areas due to environmental and economic issues. Therefore, new power plants are forced off to rural or desolate coastal areas. As a result, there is significant regional imbalance in power generation and consumption between urban and rural areas in South Korea. This paper investigates the feasibility of high-voltage DC (HVDC) system as a candidate for electric power transmission system from east-coastal sites to metropolitan area. To this end, this paper analyzes transient stability and dynamic impact of a HVDC transmission system and compares the results to conventional high-voltage AC (HVAC) transmission systems via PSS/E simulation. This paper also examines the effect of HVDC system to voltage variation and low-frequency resonance in the neighboring buses in the grid using ESCR(Effective Short Circuit Ratio)과 UIF(Unit Interaction Factor) indices.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.593-600
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• 1986

In direct contact power transmission from primary driver to a secondary follower system, one of the important problems is the vibration transmission. In some applications the reduction of vibration level at the follower as low as possible is utmost important. The magnetically coupled power transmission system is often used for this purpose. In this paper, we report the results of a study on the nonlinear torsional vibration transmission characteristics of the rotating system with face-type magnet coupling. The equation of motion is solved analytically up to 3rd harmonics. The frictional force of the sliding bearing which is used to support the follower shaft is considered as the damping term. Numerical calculations are carried out by the Newton-Raphson method, and the calculated results are compared with the experiment for face-type magnet coupling. The experimental result shows that the reasonant frequency of the magnet coupling is very low and is in good agreement with the theoretical result when the average damping constant per unit area of the sliding bearing is 0.5kg*f*sec/cm$^{3}$.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.1
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• pp.37-43
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• 2009

Fluctuations in the ocean are closely related with the underwater acoustic propagation. Internal waves are generated by fluctuation of isopycnal layer in the upper part of the stratified ocean, which are propagated from offshore to coastal area. Physical characteristics of the internal waves existed in the East Sea were derived from the five field experimental data and the ocean monitoring buoy nearshore the mid-east coast of Korea. The dominant periods are appeared in the near-inertial period about $17{\sim}20hours$ and the short period about a few minutes. The wavelengths of them are $10{\sim}50km$ and $300{\sim}1000m$, and the phase speeds are $20{\sim}100cm/s$ and $30{\sim}70cm/s$, respectively The maximum amplitudes are about $20{\sim}25m$. Under the environment of short depression internal wave propagation, the variations of transmission loss field were investigated using an range-dependent acoustic transmission loss model(RAM). The result shows that the large irregular variations of transmission loss caused by progressing the internal wave from offshore toward coast.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.3
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• pp.53-58
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• 2016

The underground transmission lines which have been built to expand the suppling facilities will be continuously accompanying with high growth of the increase of power demand in the metropolitan area in recent years. So, it is necessary to maximize the ability and reliability of power supply with the current-carrying capability of the underground transmission lines. Design criteria of KEPCO is to be presented and used frequently. But it has to be studied about the installation methods of power cable buried in ground. In this study, we used the program for calculating the current-carrying capability of underground transmission power cables. We estimated the maximum permissible current values by the horizontal arrangement in the installation methods of power cable(154kV XLPE $600mm^2$) buried ducts in ground. To see the general tendency of the analysis, we researched a statistical analysis with such parameters as the maximum permissible current values. Through the regression analysis, we analyze the most highly values of the maximum permissible current on the Ra type duct arrangement.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.560-565
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• 2010

This paper presents the design factor of an overhead transmission tower structure in order to reduce the tower weight. The behaviour of transmission tower structures are affected by the horizontal angle of the tower structure, the equivalent wind pressure group, the slope of the main post of the tower, the separation of the internode and the use of high-strength materials in their construction. Tower weight can be reduced by approximately 30% reduce weight by means of optimal design based on a consideration of all the above factors. In addition, the design of the foundation of the tower with the shear key installation to increase horizontal support together with a modified angle of inclination to the ground can reduce by about 37% the amount of concrete used during construction. The area of ground disturbed by the construction of the tower foundation can thus be reduced by approximately 33%. Therefore it is possible to build an environmently-friendly T/L tower with the mechanical properties of existing towers.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.53-56
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• 2015

In this paper, we want provide improved services with faster transmission, IEEE 802.11n was standardized. A-MPDU (Aggregation MAC Protocol Data UNIT) is a vital function of the IEEE 802.11n standard, which was proposed to improve transmission rate by reducing frame transmission overhead. In this paper, we show the problems of TCP retransmission with A-MPDU and propose a solution utilizing the property of TCP cumulative ACK. If the transmission of an MPDU subframe fails, A-MPDU mechanism allows selective re-transmission of failed MPDU subframe in the MAC layer. In TCP traffic transmission, however, a failed MPDU transmission causes TCP Duplicate ACK, which causes unnecessary TCP re-transmission. Furthermore, congestion control of TCP causes reduction in throughput. By supressing unnecessary duplicate ACKs the proposed mechanism reduces the overhead in transmitting redundant TCP ACKs, and transmitting only a HS-ACK with the highest sequence number. By using the RACK mechanism, through the simulation results, it was conrmed that the RACK mechanism increases up to 20% compared the conventional A-MPDU, at the same time, it tightly assures the fairness among TCP flows.