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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.
Long stator LSM을 적용한 초고속 튜브 자기부상열차를 위한 급전시스템 설계
정상기(Chung Sang-Gi),김형철(Kim Hyung-Chul),박현준(Park Hyun-Jun),장동욱(Chang Dong-Uk) 한국철도학회 2009 한국철도학회 학술발표대회논문집 Vol.2009 No.11월
The concept of the traction power supply system for the high speed tubed maglev system is presented, and the general idea to calculate the rated capacity of the main equipments in the substation is also presented. The imaginary powering characteristics of the linear synchronous motor are calculated from the train's dynamic force requirement, which is function of the train speed. The guide way condition, maximum design speed and efficiency of the motor are used to calculate the required power converter unit capability. The capacity of the power converter unit is calculated and discussed for the test target system.
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.
AC 전기철도 급전선 선로정수 산정시 Carson 모델 적용 검토
정상기(Sang-Gi Chung),권삼영(Sam-Young Kwon),창상훈(Sang-Hoon Chang),장동욱(Dong-Uk Chang) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-
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, I<SUB>a</SUB>+I<SUB>b</SUB>+I<SUB>c</SUB>, 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.
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),조홍식(Hong-Sik Cho),이성혁(Shung-Hyuk Lee),이안호(An-Ho Lee),이승재(Seung-Jae Lee) 한국철도학회 2003 철도저널 Vol.6 No.4
Most rail system related simulators currently used are designed to simulate only one discipline system. This obviously assumes the other discipline systems 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 simulator 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 multi-discipline problems and even find their solutions. A proto type simulator has been 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 shows it is very useful in design verification. It could also be a good tool in research and development work to improve the system.
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.