• Title/Summary/Keyword: Transmission line fault

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The Optimal Operating Points of Multiple UPFCs for Enhancing Power System Security Level (전력시스템 안전도 향상을 위한 다기 UPFC의 최적 운전점 결정)

  • 임정욱;문승일
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.50 no.8
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    • pp.388-394
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    • 2001
  • This paper presents how to determine the optimal operating points of Unified Power Flow controllers (UPFC) the line flow control of which can enhance system security level. In order to analyze the effect of these devices on the power system, the decoupled model has been employed as a mathematical model of UPFC for power flow analysis. The security index that indicates the level of congestion of transmission line has been proposed and minimized by iterative method. The sensitivity of objective function for control variables of and UPFC has been derived, and it represents the change in the security index for a given set of changes in real power outputs of UPFC. The proposed algorithm with sensitivity analysis gives the optimal set of operating points of multiple UPECs that reduces the index or increases the security margin and Marquart method has been adopted as an optimization method because of stable convergence. The algorithm is verified by the 10-unit 39-bus New England system that includes multiple FACTS devices. The simulation results show that the power flow congestion can be relieved in normal state and the security margin can be guaranteed even in a fault condition by the cooperative operation of multiple UPECs.

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A study on Protection Coordination Method for Electric Vehicle Charging Facility based on the Wireless Power Transmission (무선전력전송 전기충전설비용 전원공급장치의 최적운용방안에 관한 연구)

  • Ryu, Kyung-Sang;Kim, Byungki;Kim, Dae-Jin;Jang, Moon-Seok;Rho, Daeseok;Ko, Hee-Sang
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.9
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    • pp.42-51
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    • 2017
  • This paper deals with the power supply facility providing wireless power transmission for a type of electric vehicles called the on-line electric vehicle(OLEV) and proposes optimal protection coordination methods which analyze the faultsin the 60Hz and 20kHz bands using PSCAD/EMTDC, which is the typical commercial software for the distribution system. The simulation results show that the proposed methods can reduce the fault current by introducing an NGR (Neutral Ground Resistor) in the 60Hz band and prevent the malfunctioning of the protection device by installing a CT in the neutral wire in the 20kHz band when a ground fault occurs.

The Implementation of Load Resistance Measurement System using Time-Frequency Domain Reflectometry (시간-주파수 영역 반사파 계측방법을 이용한 부하 저항 측정 시스템 구현)

  • Kwak, Ki-Seok;Park, Tae-Geun;Yoon, Tae-Sung;Park, Jin-Bae
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.55 no.10
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    • pp.435-442
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    • 2006
  • One of the most important topics about the safety of electrical and electronic system is the reliability of the wiring system. The Time-Frequency Domain Reflectometry(TFDR) is a state-of-the-art system for detecting and estimating of the fault on a wiring. In this paper, We've considered the load resistance measurement on a coaxial cable using TFDR in a way of expanded application. The TFDR system was built using commercial Pci extensions for Instrumentation(PXI) and LabVIEW. The proposed real time TFDR system consisted of the reference signal design, signal generation, signal acquisition, algorithm execution and results display part. To implement real time system, all of the parts were programmed by the LabVIEW which is one of the graphical programming languages. Using the application software implemented by the LabVIEW, we were able to design a proper reference signal which is suitable for target cable and control not only the arbitrary waveform generator in the signal generation part but alto the digital storage oscilloscope in the signal acquisition part. By using the TFDR real time system with the terminal resistor on the target cable, we carried out load impedance measurement experiments. The experimental results showed that the proposed system are able not only to detect the location of impedance discontinuity on the cable but also to estimate the load resistance with high accuracy.

Jeju 80kV HVDC Controller Modeling Using PSCAD/EMTDC Program (PSCAD/EMTDC 프로그램을 이용한 제주 80kV HVDC 제어기 모델링)

  • Choi, Soon-Ho;Lee, Seong-Doo;Kim, Chan-Ki
    • The Transactions of the Korean Institute of Power Electronics
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    • v.16 no.6
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    • pp.533-541
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    • 2011
  • This paper studies modeling of Jeju 80kV HVDC system and its controller by using PSCAD/EMTDC program. Reduced ac network is applied to verify interaction between ac network and dc system. Design parameter is applied to the converter transformer, harmonic filter and dc transmisstion line to simulate dc system. HVDC controller is divided into a rectifier controller and a inverter controller according to the converter operating mode. The inverter controller is composed of current control, voltage control and extingtion angle control. The rectifier controller is composed of current control and voltage control. Both controller has VDCOL characteristics so that current order is dependant on voltage variation. Step response, ac network single phase fault, three phase fault is simulated to verify the dynamic performance of controller model in both transient state and steady state.

An Study on Effective Maintenance and Operation System of Fiber Optic Lines (효과적인 광선로 유지 보수를 위한 시스템 개발에 관한 연구)

  • Jang, Eun-Sang;Park, Kap-Seok;Kim, Seong-Il;Choi, Sin-Ho;Lee, Byeong-Wook
    • Proceedings of the IEEK Conference
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    • 1998.06a
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    • pp.54-57
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    • 1998
  • As the physical layer on telecommunication network is replaced fiber optic lines, it is increased the need of systematic maintenance for fiber optic lines. Korea Telecom has developed FLOMS in order to establish maintenance processes for optical fiber lines. FLOMS has functions which manages optical facilities and tests optical fiber lines automatically. As a resuls, this system can check and/or report a fault. Operator, who is reponsible for management of optical fiber lines, can test the characteristics of optical fiber lines remotely using FLOMS. As interpoerable with Digital Transmission Management System, FLOMS provides efficient management for optical fiber lines. This system improves the work process to find fault location fast, detect the degradation of fiber quality, and make database of optical facilities efficiently.

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A Simultaneous Perturbation Stochastic Approximation (SPSA)-Based Model Approximation and its Application for Power System Stabilizers

  • Ko, Hee-Sang;Lee, Kwang-Y.;Kim, Ho-Chan
    • International Journal of Control, Automation, and Systems
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    • v.6 no.4
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    • pp.506-514
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    • 2008
  • This paper presents an intelligent model; named as free model, approach for a closed-loop system identification using input and output data and its application to design a power system stabilizer (PSS). The free model concept is introduced as an alternative intelligent system technique to design a controller for such dynamic system, which is complex, difficult to know, or unknown, with input and output data only, and it does not require the detail knowledge of mathematical model for the system. In the free model, the data used has incremental forms using backward difference operators. The parameters of the free model can be obtained by simultaneous perturbation stochastic approximation (SPSA) method. A linear transformation is introduced to convert the free model into a linear model so that a conventional linear controller design method can be applied. In this paper, the feasibility of the proposed method is demonstrated in a one-machine infinite bus power system. The linear quadratic regulator (LQR) method is applied to the free model to design a PSS for the system, and compared with the conventional PSS. The proposed SPSA-based LQR controller is robust in different loading conditions and system failures such as the outage of a major transmission line or a three phase to ground fault which causes the change of the system structure.

Current Limiting and Interrupting Operation of Hybrid Self-Excited Type Superconducting DCCB

  • Choi, S.J.;Lim, S.H.
    • Progress in Superconductivity and Cryogenics
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    • v.20 no.4
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    • pp.55-59
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    • 2018
  • Currently, the development of industry makes needs larger electric supply. Providers must consider the efficiency about losses and reliability of the system. In this case, DC power system can save electrical energy; long-distance transmission line losses. Relevance to switch technology with a voltage-source converter (VSC) in AC-DC conversion system have been researched. But, protection device of DC-link against fault current is still needed to study much. VSC DC power system is vulnerable to DC-cable short-circuit and ground faults, because DC-link has a huge size of capacitor filter which releases extremely large current during DC faults. Furthermore, DC has a fatal flaw that current zero crossing is nonexistence. To interrupt the DC, several methods which make a zero crossing is used; parallel connecting self-excited series LC circuit with main switch, LC circuit with power electronic device called hybrid DC circuit breaker. Meanwhile, self-excited oscillator needs a huge size capacitor that produces big oscillation current which makes zero crossing. This capacitor has a quite effective on the price of DCCB. In this paper, hybrid self-excited type superconducting DCCB which are using AC circuit breaker system is studied by simulation tool PSCAD/EMTDC.

Damping Analysis using IEEEST PSS and PSS2A PSS

  • Lee Sang-Seung;Kang Sang-Hee;Jang Gwang-Soo;Li Shan-Ying;Park Jong-Keun;Moon Seung-Il;Yoon Yong-Tae
    • Journal of Electrical Engineering and Technology
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    • v.1 no.3
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    • pp.271-278
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    • 2006
  • This paper scrutinized the damping effects of installing the prototype PSSs by a transient analysis for eight buses of faults in the South Korean power system. The PSSs used have the co-PSS blocks for IEEEST model with a single input and the co+power PSS blocks for PSS2A model with dual inputs. The simulation tool was a TSAT(Transient Security Assessment Tool) developed by Powertech Labs Inc. The voltages of the transmission line for simulations were 765kV and 345kV, and the faults for eight cases were sequenced by considering the open state and the close state of the lines. In the simulations, the three-phase line to ground (L-G) fault generated different points for each region. The simulations were compared to the cases of no PSS, partial IEEEST and PSS2A, absolute IEEEST, and absolute PSS2A to show that the power system oscillation can be effectively damped by PSS modules. Simulations were conducted to confirm the effectiveness for the KEPCO (Korea Electric Power Corporation) power system.

A Conceptual Design of Maintenance Information System Interlace for Real-Time Diagnosis of Driverless EMU (무인전동차의 실시간 상태 진단을 위한 유지보수 정보시스템 인터페이스에 대한 개념설계)

  • Han, Jun-hee;Kim, Chul-Su
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.10
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    • pp.63-68
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    • 2017
  • Although automated metro subway systems have the advantage of operating a train without a train driver, it is difficult to detect an immediate fault condition and take countermeasures when an unusual situation occurs. Therefore, it is important to construct a maintenance information system (MIS) that detects the vehicle failure/status information in real time and maintains it efficiently in the depot of the railway's vehicles. This paper proposes a conceptual design method that realizes the interface between the train control system (TCS), the operation control center train control monitoring system (OCC-TCMS) console, and the MIS using wireless communication network in real-time. To transmit a large amount of information on 800,000 occurrences per day during operation, data was collected in a 56 byte data table using a data processing algorithm. This state information was classified into 4 hexadecimal codes and transmitted to the MIS by mapping the status and the fault information on the vehicle during the main line operation. Furthermore, the transmission and reception data were examined in real time between the TCS and MIS, and the implementation of the failure information screen was then displayed.