• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.89-96
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• 1996

This paper presents a study on the analysis and evaluation for ELF( Extremely Low Frequency) electric and magnetic fields under the transmission line according to the power system states. The power system states are classified into two types, normal state resulting from normal operation and alert state from outages. The current in a system is changed continually owing to the load fluctuations even in a normal operation. To calculate the current of the concerned line in a normal state, the system load level is devided into light, base and heavy load level. In case of contingency, an efficient algorithm based on matrix inversion lemma is developed to figure out the current changes. In order to analyze the variations of ELF field caused by the current fluctuations the electrostatic field approach which is far simpler than the electromagnetic field one based on Maxwell equation is introduced in this paper. The suggested method is applied to the IEEE 14 bus system to demonstrate the usefulness.

• Journal of the Korean Society of Safety
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• v.13 no.3
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• pp.80-87
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• 1998

This paper presents a study on the development of discharge model and computer program for assessing the risk of electrostatic discharge(ESD) of charged human body This ESD event is modelled as a two-body problem using spherical conductors, simulating the approach of a charged conductor (human body) to a second conductor (electronic equipment). The charge/discharge process for the model is formulated as a matrix of equations by Maxwell's method. Body potentials, energies and the charge transfer during a discharge are calculated. The developed program, based on the suggested scheme in this paper, is applied to a sample system. The results provide a better understanding of ESD event and demonstrate the usefulness of two-body model in practical applications.

• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.75-80
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• 1996

This paper presents a study on characteristics and safety for human body in ELF electric and magnetic fields using statistical method. The magnetic fields from a power line can be computed given a knowledge of the currents, voltage and geometry of the line. In this paper, a statistical method for predicting the magnetic fields given the inherent indetermination of the currents is presented. But the electric field is calculated given a knowledge of the voltage and geometry of the line. The effect of unexpected fluctuations in current is modeled by the Monte Carlo simulation. The suggested method is applied to the 345kV and 765kV transmission line system, the result shows that the maximum electric and magnetic field intensity is 6.8627kV/m and 284mG in 345kV system, 2. 5590kV/m and 35mG in 765kV system, respectively.

• Journal of the Korean Society of Safety
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• v.18 no.2
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• pp.22-27
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• 2003

The roller machines installed in the industrial field are operated under hazardous conditions due to no safety devices available, human error during operation, defective safety devices, and inadequate regulation even in case that safety devices are provided. Up to now, most roller machines installed in domestic field are provides with band breaking system as a safety device. In this study, the emergency stop distance is measured within the limit of domestic regulation but violates a foreign regulation(EN1417). Consequently, it is concluded that the roller machines with a band breaking system have high possibility of death or serious injury of the operator and the system should be improved with the introduction of additional safety devices. This thesis suggests the safety measures suitable for the roller machines with different drive systems based on the experiment results. The use of the newly developed safety system has been tested on many cases.

• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.54-58
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• 2012

This paper is purposed to analyze electric leakage component which can prevent electrical fires on breaker capacity expansion and power failure by operation of ELB(Earth leakage breaker) for stable sizes. In order to analysis for electric leakage component for stable sizes, this paper studied field state investigation which are at stable companies( 10 companies) in cheong-won location to deduce the problems of electric leakage component is analyzed. The field state experiment method is measured with electric leakage component which load part of ELB detected by electric loads(electrical fan, lighting, auto waterer, feeder and halogen lighting) and stable sizes. Results show that electric leakage component suggested in this paper are valuable and usable to electrical fire in leakage current based on environment factor, which will prevent severe damage to human beings and properties and reduce the electrical fires in stable.

• Journal of the Korean Society of Safety
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• v.22 no.1 s.79
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• pp.40-46
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• 2007

It is evaluated that electric shock risk in bath so that we made and designed a bathtub which is the same size in real public bath. And then, we did an experiment, provided of electric leakage in various conditions, so we measured how to form an electric potential and knew the electric potential is formed variously under exposed conductor in bath. Also, we made certain that electric shock risk is down if we insert an insulated pipe in bathtub pipe which is prevent from being formed the electric field sharply. The results show that the increased shock risk and safe distance are estimated by the bathtub of limited width and depth, and the voltage simulated on the basis of Flux 3D concept is compared with the measured value.

• Journal of the Korean Society of Safety
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• v.25 no.2
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• pp.24-28
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• 2010

The nuclear power Plant onsite AC electrical power sources are required to supply power to the engineering safety facility buses if the offsite power source is lost. Typically, Diesel Generators are used as the onsite power source. The 125 VAC buses are part of the onsite Class 1E AC and DC electrical power distribution system. The DC power distribution system ensure the availability of DC electrical power for system required to shutdown the reactor and maintain it in a safety condition after an anticipated operational occurrence or a postulated Design Base Accident. Recently, onsite DC power supply system trip occurs the loss of system function. To obtain the performance such as reliability and availability, we analyzed the cause of battery charger trip and described the improvement of DC power supply system reliability. Finally, we provide reliability performance criteria of charger in order to ensure the probabilistic goals for the safety of the nuclear power plants.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11a
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• pp.89-92
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• 2002

인터넷의 급속한 확산과 통신 기술의 발전으로 이용자들은 더욱 많은 컨텐츠를 요구하고 있고 이에 멀티미디어 스트리밍 기술이 많은 관심을 받고 있다. 이에 본 논문에서는 기존에 연구되어진 MPEG-4 Layering 기술을 바탕으로 용량이 큰 멀티미디어 데이터를 환경의 스트림으로 전송하는 방법이 아닌 여러 개의 스트림으로 분할하여 가변적인 네트웍 환경에 맞추어 전송할 수 있도록 하였으며, 클라이언트 측에서 QoS Level을 측정하여 이후 수신되는 스트림에 적용될 수 있도록 구현하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11a
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• pp.49-52
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• 2002

홈 서버의 킬러 어플리케이션으로써 홈 협동작업 서비스를 개발하였다. 홈 협동작업 서비스는 Q+라는 임베디드 OS를 사용하는 홈 서버에서 VoIP, SIP, RTP등의 인터넷 표준 프로토콜을 통합하여 영상 전화 기능을 제공하면서 T.120과 공동 브라우징 개념을 도입하여 서로 연결 중인 상대와 협동작업이 가능하도록 한다. 흠 서버 환경에서는 일반 PC 환경과는 다르게 사용자가 간단한 메커니즘으로 작업을 할 수 있어야 한다. 홈 협동작업 서비스에서는 일반 전화기로 사용자가 어플리케이션이 제공하는 모든 작업을 할 수 있다.

• Journal of the Korean Society of Safety
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• v.20 no.3 s.71
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• pp.47-52
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• 2005

Recently, power conversion equipment increased rapidly makes a lot of harmonics. Thus, it is growing that wrong operation and break down of sensitive devices. There are two kinds of causes of harmonics. One of them is lots of power conversion equipment as modem controller, inverter, converter and SWS(Switching Mode Power Supply). Another is nonlinear operating machines as transformer and motor. The more nonlinear loads like them grow, the more serious problems as harmonic current to source and low power factor because of increasing reactive power grow. It is installed for reactor and L-C Filter to decrease harmonic in general. This paper analysis and compares two of characteristics and harmonic from reactor and L-C Filter with operation of induction motor and power conversion equipment. In the result, L-C Filter more improves unbalance rate and THD than reactor.