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Carbon Black-PVC와 Carbon Black-HDPE 복합재료의 전기적 성질
정상기,노시태,임승순,Jeong, Sang-Gi,No, Si-Tae,Im, Seung-Sun 한국섬유공학회 1991 한국섬유공학회지 Vol.28 No.12
Electrical conductive PVC and HDPE composites were prepared by melt compounding method with electrical conductive carbon black. The electrical and mechanical properties of carbon black composites were affected by the particle size, surface area, density, aggregation morphology and dispersion state of carbon black, According to the carbon black contents, the composites have shown the behaviors of insulator, semiconductor and conductor. The percolation threshold of the carbon black composite was examined. From the temperature dependence of conductivity for the composites, we found that Carbon Black-PVC composites were very stable and reproducible to the temperature changes. Carbon Slack-HDPE composites have shown a PTC(positive temperature coefficient of resistively) effect which has a sudden resistively increase by thermal expansion of polymer at melting region. To prevent a NTC(negative temperature coefficient of resistively) effect and improve reproducibility of conductivity, the chemical crosslinking was accomplished.
객체지향모델를 이용한 경량전철 시스템의 성능 시뮬레이션
정상기,정락교,한석윤,Jeong, Sang-Gi,Jeong, Rak-Gyo,Han, Seok-Yun 한국시스템엔지니어링협회 2004 시스템엔지니어링워크숍 Vol.4 No.-
Most rail system related simulations currently used are designed to simulate only one discipline system. This obviously assunes the other discipline system are running regularly not being affected by the system being simulated. In this paper a multi discipline simulator is proposed and its design concept is presented.A multi discipline simulator is the simultor in which major subsystems with different technical discipline are simulated simultaneously. The advantage of the simulator is in that it makes it possible to analyze the systems behavior while other discipline system vary. With this we can identify the possible to analyze the systems ehavior find their solutions. A proto type simulator has bee developed using object oriented programming. Object concept was judged best suitable to model the various multi-discipline self-controlling railway subsystems. It was applied to the target system, which is under development by the Korea Railroad Research institute. The test results show it is very useful in design verification. It could also be a good tool in research and development work to make to improe the system.
정상기(Chung Sang-Gi),홍재승(Hong Jae-Seung) 한국철도학회 2000 한국철도학회 학술발표대회논문집 Vol.- No.-
Computer algorithms for the loadflow of the DC traction power supply system are examined. Algorithms to solve the nodal equation are reviewed and the two iterative methods to solve the nonlinear nature of the loadflow are analyzed and tested, which are so called conductance matrix method and current vector iterative method. The result of the analysis tells that the current vector iterative method makes faster convergency and needs less computing time, and it is verified by the test running of the programs based on each of the iterative methods.
정상기(Chung Sang-Gi),홍재승(Hong Jae-Seung) 한국철도학회 2000 한국철도학회 학술발표대회논문집 Vol.- No.-
The advance of traction motor control technology and the complexity of the traction power supply system makes the simulation essential in determining the dimension of the traction power supply system. The conventional method, use of the simplified and/or empirical equations, becomes inadequate in optimization of the design. The simulator presented in this paper is a numerical time based simulator running on a PC. The input to the simulator includes the track data, the train characteristic, network data and operating data. Basically the simulator conducts train running simulation and loadflow study repeatedly. The principle algorithms and its output is discussed in the paper.
전송로의 직렬리액턴스 산정 시 Carson 모델의 적용범위 검토
鄭相基(Sang-Gi Chung),權三榮(Sam-Young Kwon),倉相勳(Sang-Hoon Chang),張東旭(Dong-Uk Jang) 대한전기학회 2009 전기학회논문지 Vol.58 No.2
In this paper, it is shown that Carson's equation can still be applied for the calculation of the series reactance of transmission lines with no ground return current as well as the one with ground return. It is proved in the following method. First two voltage drop equations for three-phase three wire transmission line are derived, one without considering ground return and the other using Carson's equation. The impedance matrix of the two equations are different from each other. But if we put the condition of zero ground current, Ia+Ib+Ic = 0, those two equations becomes the identical equations. Therefore even a transmission line is not grounded, its line parameters can still be obtained using the Carson's equation. It has been confused whether or not Carson's equation can be used for an ungrounded system. It is because where ever Carson's equation is shown in the book, it also says that the system has ground return current paths as a premise. It is also verified with EMTP studies on the test circuit.
정상기(Sang-Gi Chung),정락교(Rag-Gyo Jeong),이성혁(Sung-Hyeok Lee),김연수(Yun-Su Kim),조홍식(Hong-Sik Cho) 한국철도학회 2004 철도저널 Vol.7 No.4
In urban rail transit systems, ground faults in the DC traction power supply system are currently detected by the potential relay, 64P. Though it detects the fault it cannot identify the faulted region and therefore the faulted region could not be isolated properly. Therefore it could cause a power loss of the trains running on the healthy regions and the safety of the passengers in the trains could be affected adversely. Two new ground fault protective relay schemes that can identify the faulted region are presented in this paper. A current limiting device, called Device X, is newly introduced in both system, which enables large amount of ground fault current flow upon the positive line to ground fault. One type of the relaying schemes is called directional and differential ground fault protective relay which uses the current differential scheme in detecting the fault and uses the permissive signal from neighboring substation to identify the faulted region correctly. The other is called ground over current protective relay. It is similar to the ordinary over current relay but it measures the ground current at the device X not at the power feeding line, and it compares the current variation value to the ground current in Device X to identify the correct faulted line. Though both type of the relays have pros and cons and can identify the faulted region correctly, the ground over current protective relaying scheme has more advantages than the other.
정상기(Sang-Gi Chung),정락교(Rag-Kyo Jeong),김백현(Baek-Hyun Kim) 대한전기학회 2011 전기학회논문지 Vol.60 No.1
A PRT vehicle’s control method is presented in this paper. In the asynchronous vehicle control system, vehicles follow their leading vehicles. Leading vehicles are defined differently among the different types of track. The main topic of this paper is to present a method to define the leading vehicle among different types of track and the calculation algorithm of the safety length the following vehicle must maintain. Simulation program is developed using the algorithm and the results of the test run are presented. An asynchronous PRT vehicle control algorithm was presented by Szillat in the paper “A low level PRT Microsimulation, Dissertation, University of Bristol, 2001”. But it is different from the algorithm in this paper. In the algorithm proposed by Markus, vehicles in the merging track are controlled synchronously, and its safety distance between the leading and the following car is evaluated after the establishment of the complicated future time-location table instead of simple equations proposed in this paper.
비접지 DC 급전시스템에서의 Delta-I 지락보호계전 시스템
鄭相基(Sang-Gi Chung),權三榮(Sam-Young Kwon),鄭澔聖(Ho-Sung Jung),金周落(Ju-Rak Kim) 대한전기학회 2006 전기학회논문지A Vol.55 No.12
In DC tracking power supply system, ground faults are currently detected by the potential relay, 64P. Though 64P relay detects ground fault, it cannot identify the faulted region which causes long traffic delays and safety problem to passengers. A new ground fault protective relay scheme, △I ground fault protective relay, that can identify the faulted region is presented in this paper. In △I ground fault protective relaying scheme, ground fault is detected by 59, overvoltage relay, which operates ground switch installed between the negative bus and the ground. It preliminarily chooses the faulted feeder after comparing the current increases among feeders and trips the corresponding feeder breaker. After some time delay, it then recloses the breaker if it finds the preselected feeder is not the actual faulted feeder. Whether or not the preselected feeder is the actual faulted feeder is determined by checking the breaker trip status in the neighboring substation in the direction of the tripped breaker. If the corresponding breaker in the neighboring substation is also tripped, it finally judges the preselected feeder is actually a faulted feeder. Otherwise it recloses the tripped breaker. Its algorithms is presented and verified by EMTP simulation.