로버트 카파

김백 한국철도학회 2023 철도저널 Vol.26 No.4

전철용 전력정보시스템의 구성 요소에 대한 연구

김백 철도전문대학교 2001 論文集 Vol.16 No.-

The conventional SCADA adopted for the electric railway has the mere function of controlling and monitoring the hardware itself. Lack of the functions necessary for the fault prevention and the system recovery requires the operators to depend on their intuition and experience. To make up for these shortcomings of the conventional SCADA, PIS(Power Information System) visually offers integrated information for the optimal operation of the power system by manipulating the raw data acquired from the SCADA. In this paper we have studied the variety of information and its feasibility that can be offered individually by PIS.

전철용 변압기의 차동보호방식에 관한 연구

김백 한국철도대학 2005 論文集 Vol.20 No.-

Scott transformer is mostly used as a power transformer in AC electric railway systems to clear up the unbalance problems occured in 3-phase source side. However the phase number difference between the primary and the secondary(3φ/2φ) makes the differential protection method, that is widely adopted in 3-phase transformer protection, somewhat difficult to adopt. So it is needed to examine thoroughly the current of both sides of transformer. In this study the differential protection method for the 3φ-2φ transformer is devised from the examination of this method to the 3φ-3φ transformer. Also the correction process for this method has been studied for the realization in the industry.

스코트 변압기 부하에 의한 전압 및 전류불평형율 연구

김백 한국철도대학 2008 한국철도대학논문집 Vol.23 No.-

This paper verifies the formulas concerned with voltage and current unbalance factors prescribed in the law by government for the electric railway. Through the rigid derivation, the constraint conditions included in the specified formula K_(V) = 1/P_(S)·|P_(T) - P_(M)| are revealed. Actually, this formula becomes more accurate as the power factor of the load approaches to 1.0 in reality. Moreover, since we can't sustain the unbalance factor to zero value at every instant, it is believed that the use of average load for 2 hours is reasonable to some extents.

AT급전계통의 단락임피던스 계산에 관한 연구

김백 철도전문대학교 2006 論文集 Vol.21 No.-

In this paper a new method of calculating short-circuit impedance for the AT feeding systems has been studied. The short-circuit impedance of the feeding systems is not proportional to the line distance because of boosting effect from ATs, that is different from commercial transmission lines. This non-linear behavior of the impedance make the calculation of fault currents and fault locating somewhat difficult. The widely used calculating method for this purpose is so called, 'method of reduced equivalent circuit'. However since this method has ambiguous stages in its derivation, the results from the method can't be fully confirmed. On the contrary the new method proposed here makes use of the analysis method of linear circuits, which is very clear in its derivation and has no constraints in its use. Example calculation of the impedance is illustrated to show the simplicity and accuracy of the proposed method.

전철 지중송전선로의 시스 접지에 관한 연구

김백 철도전문대학교 2003 論文集 Vol.18 No.-

In this study the surge voltage induced to the sheath of underground cable during the normal or abnormal operating states has been analyzed by systematic inspection of the various CCPU connection methods. The pros and cons of each connection method have been inspected through literature, former researches and computer simulation using PSB of Simulink. And hereby the more effective and safer design techniques can be revealed obviously. It is expected that the results from this study contribute to the development of techniques in the related field.

Scott변압기로 연결된 3상/2상 전철 전력계통의 고장 전류 계산

김백 철도전문대학교 2004 論文集 Vol.19 No.-

In this paper the calculation method of the fault currents in the electric railway systems that is connected by Scott transformer has been studied. Since the Scott transformer performs the 3Ø-to-2Ø transforming, we can't use directly the symmetrical method, a common method for fault analysis in 3-phase power systems. This problem has been worked out in this study by separating 3-phase systems faults and 2-phase systems faults. Also some useful formulas for exchanging impedances between two systems have been developed to calculate fault currents. It is expected that the results from this study contribute to the more stable operation of electrical railway systems.

부하의 전압의존성을 고려한 전압안정도 직접해석법에 관한 연구

김백 철도전문대학교 1996 論文集 Vol.12 No.1

This paper deals with the development of an appropriate energy function and its application in direct stability analysis to consider the voltage dependency of the loads. Time-simulation analysis shows that the power system stability is considerably affected by the load characteristics. No other method has been found yet to reflect the voltage-dependency of load in direct stability analysis. In this study, the complex load is approximated by the sum of constant impedance load, constant current load and constant power load. By using the approximated load model, an energy function is derived to reflect each load characteristics. Generally, an energy function of the power system includes an energy term associated with real power loads which is given by a path-dependent integral. In order to solve the path-dependency problem, this paper adopts the approximated evaluation of the path-dependent integral by a straight line integral. The proposed method has been tested for a 3-bus sample system.

전압원인버터로 구동되는 견인유도전동기의 과도상태 해석

김백 철도전문대학교 1999 論文集 Vol.15 No.-

This paper presents a variable frequency induction motor drive in which a pulse width modulated (PWM) voltage source inverter is used as a variable voltage variable frequency(VVVF) source to drive the inverter train in variable speed operation. The drive, including the motor, the inverter, and the speed control system is modeled by using simulink blocks. The drive operation is studied for different operating conditions; starting, steady state, and regenerative braking. The simulation results show that the proposed model reveals the dynamic behavior of voltage source inverter very well. Since the model is composed of blocks from simulink that is being used in a world wide, it can be linked with other models easily. The proposed model is expected to be useful in related research areas such as a noise reduction filter design, a fast reliable controller design and etc.

SVD에 의한 급전 모선의 전압안정도 해석

김백 철도전문대학교 1997 論文集 Vol.13 No.1

In this study, with the derivation of the rules related to the singular value, sensitivities, a new method has been presented. In this method a minimum singular value serves as a global voltage collapse proximity index while singular value sensitivities serve as local voltage collapse proximity indices. The usefulness of the presented method has been verified by being applied to a sample system. Consequently it is expected that this method can contribute to the actual power system operation. The main results are summarized as follows; 1) It is shown by mathematical operations that the minimum singular value of load flow Jacobian matrix can be served as a VCPI and verified through tests to a sample system. 2) Since the total amount of loads that cause voltage collapse has close relation with the pattern of load increase, the sensitivities of VCPI are necessary in practice. 3) The singular value sensitivity equation has been derived. By adopting this equation into the load flow Jacobian matrix, priority decision for reactive power compensation and index estimation can be done well 4) This study is for the verification of the method through simulations to a sample system, it is recommended to study continuously for the application to the actual power systems.