• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.881-885
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• 2001

The study about a drainpipe of water closet was performed as reduction of drainage noise for water closet. The Drainage noise is composed two characteristics. One is Low frequency noise and the other is high frequency noise. Low frequency noise is dominant in the first stage and high frequency noise is dominant in the last stage. This is due to water splashing and that is caused by formation of chamber pot. In this experiment, for the purpose for reducing the noise, we choose the hollow rubber pipe element. As a result, we reduced drainage noise about 11㏈A.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.3
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• pp.16-20
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• 2000

Most of speech recognition systems are using Hidden Markov Model based on statistical modelling frequently. In Korean isolated telephone digit speech recognition, high recognition rate is gained by using HMM if many training data are given. But in Korean continuous telephone digit speech recognition, HMM has some limitations for similar telephone digits. In this paper we suggest a way to overcome some limitations of HMM by using discriminant learning based on minimal classification error criterion in Korean continuous telephone digit speech recognition. The experimental results show our method has high recognition rate for similar telephone digits.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.806-812
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• 2005

This paper proposes a new reliability evaluation for traction power system. The electric railway consists of traction power systems, various vehicles, operating equipment, track, overhead line and electric equipment. It is a fundamental function of traction power systems that supply customers with reasonable price, acceptable reliability and high quality power. In a general way, the power system reliability deals with the ability to satisfy load demands in supply capability or rating of every factor. On the other hand, the reliability of traction power systems has been focused on train time delay caused by power outage. In this paper, we make a selection optimum reliability indices for the reliability evaluation of electric traction power systems. The reliability study not only applies a plan for traction supply system after detecting the vulnerable point of existing traction supply systems but also makes a role in stable operating railway.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.867-872
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• 2005

This paper describes the measurement and location method of partial discharges in high voltage CV cables. Coupling capacitors were used to detect partial discharge signal. Impedance characteristic of the coupling circuit and an amplifier with a high Common Mode Rejection Ratio(CMRR) were studied to improve sensitivity of the circuit. From the calibration experiment, the sensitivity of the partial discharge detection circuit was about 100pC. Also, we confirmed that the location of partial discharges in cables can be estimated by calculation of time difference between the first pulse and the second one reflected from the other end of the cable.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.819-824
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• 2005

This paper describes the measurement result of leakage current flowing arresters connected in feeder lines to propose an optimal management method. Twenty seven arresters set in seven areas were analyzed on a regular basis for 4 months. The results showed that the RMS and the peak value of the total leakage currents for soundness arresters were a range of $200uA{\sim}00uA$. respectively. During the period of measurement, the magnitude of the leakage current didn't show conspicious changes and there were impossible places to analyze arrester's status due to including high THD rate in a feeder line, From the study, leakage current measurement has to be performed at a condition without running an electric train in the line, and the allowable RMS value of soundness arrester is bellow 600uA.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.236-241
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• 2007

DC feeding system is mainly floating but the rail potential and the leakage current are created because of long parallelism between rails and ground. Rail potential causes electric shock to human and leakage current causes electrolytic corrosion to nearby the buried metals. Therefore the design technologies to reduce, protect and monitor these effects are important recent DC feeding system. Normally during designing DC feeding system in terms of rail potential and leakage current, there are about 10 parameters. Four design parameters among those is analysed based on propagation theory that is utilized in order to simulate grounding system.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.852-857
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• 2007

For electric traction using a large power converter, harmonic problem in the p-ower quality and regenerating energy in side of efficiency are important. Recently, by advance in power electronics technology, some countries are considering regenerative inverter from the points of view. when the electric tractions are stopped or driven through the falling slope way, it is very useful to supply surplus energy to the power source by regenerating system in the efficient side of energy and it is very economical. these regenerating energy are supported electrical equipment through DC line. In this research, the purposes are suppressing extra DC-line voltage and saving energy generated while electric traction is been driving on the falling slope way or reducing speed for railway using a 1500V DC-voltage. Besides, the accompanied defects of current distortion, low power factor and the voltage unbalance will be solved by developing the algorism of inverter having ability to compensate current harmonic.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.498-506
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• 2010

The neutral section was installed in order to prevent conflict with different phase angle source in electric railway catenary system. The speed of electric train reduced due to coasting operation by notch off when it passed the neutral section. And, the catenary wire was damaged and the accident might be happened because of the arc generation when the electric train passed the neutral section with notch on condition. This project has a goal to develop the automatic changeover system using by noncontactless semiconductor device in neutral section of catenary system so that the train pass as notch-on condition. In this first year, we obtain as following results such as domestic and international systems applications and completion requirements, development and analysis of stability for automatic changeover system, design of static switching device on automatic changeover system in neutral section and drawing up interface design and specifications according to equipment.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.171-176
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• 2010

Railway has recently played an important role in preventing global warming caused by green house gases and furthering a low carbon green growth, The various railway research centers have conducted facilitated studies on saving energy. In particular, urban railway has emerged as the best means of public transportation in terms of punctuality, safety and environmentally friendliness. There are various ways to save energy in terms of operation of urban railway system, and they can be generally divided into hardware aspects that pertain to structure of vehicles and development of control system and software aspects that pertain to effective operation of trains based on operation patterns and diagram control. In this paper, we investigated drive assistance system for railway energy efficiency. The railway operation patterns and train diagram management programs were researched.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1878-1884
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• 2010

Currently in Korea, neutral sections in front of substations and sectioning posts are greatly divided into AC/DC sections and AC/AC sections. Considering catenary damage and safety issues trains pass crossover by coasting driving at notch-off. However in cases of Japan, China, or Taiwan, the usage of automatic crossover system makes it possible to pass at notch-on, enhancing high-speed railway operation for efficiency, and stability. These are the purposes of developing automatic power crossover system in neutral sections. This paper introduces two methods to detect the position of a train required to activate automatic crossover systems in neutral sections. The optimal method is expected in terms of the distance of neutral section.