• Title/Summary/Keyword: current time

Search Result 13,121, Processing Time 0.05 seconds

A Novel Digital Over Current Relay with Variable Time-Current Characteristics for Protective Coordination

  • Park, M. S.;P. S. Cho;Lee, S. J.;S. H. Hyun;Kim, K. H.
    • KIEE International Transactions on Power Engineering
    • /
    • v.2A no.3
    • /
    • pp.83-88
    • /
    • 2002
  • An over current relay(OCR), one of the most frequently used protective devices, has time-current characteristics (TCC) to control its trip time according to the current level. It is because an appropriate operating time interval is necessary for coordination with other protective devices. A set of TCC curves of an OCR is, in general, given by the supplier from which a curve is selected by the operator. Therefore, in many cases, it is impossible to consider the operation condition of the given power system exactly. A novel concept of an OCR is suggested in this paper. The proposed OCR has an internal correction module so that it may produce the most adequate TCC curve according to the given protective information for coordination with other devices. With the generated TCC curve, a variety of operation and coordination conditions can be taken into consideration in an effective manner. The suggested OCR is applied to a simple test power system to show very promising results from a coordination point of view.

An Operation Grouping and Its Maximum Allowable Conductor Temperature Considering Facility-conditions of Transmission Lines (송전선로의 설비특성을 고려한 운영그룹 분류 및 최고허용온도)

  • Sohn, Hong-Kwan;Kim, Byung-Geol;Park, In-Pyo;An, Sang-Hyun;Jang, Tae-In;Choi, Jang-Kee
    • The Transactions of The Korean Institute of Electrical Engineers
    • /
    • v.57 no.11
    • /
    • pp.1922-1928
    • /
    • 2008
  • The thermal rating of a conductor are maximum continuous current capacity and short time emergency current capacity. The overload operation for a faults have an effect on a conductor lifetime. Its time duration and overload level are limited to facility conditions of transmission lines. The short time emergency current capacity in KOREA observe the KEPCO's DESIGN RULE 1210, but its rules are not included to concept of an allowable short time duration. This papers are described to the calculation concept of short time emergency current capacity considering a time duration and an overload level. And we suggested a operation grouping and its maximum conductor temperature considering facility conditions - conductor lifetime, stability of connection points, conductor height above ground and clearance, in the operating and new T/L.

Internal Model Control of UPS Inverter with Robustness of Calculation Time Delay and Parameter Variation (연산지연시간과 파라미터 변동에 강인한 UPS 인버터의 내부모델제어)

  • Park, Jee-Ho;Keh, Joong-Eup;Kim, Dong-Wan;An, Young-Joo;Park, Han-Seok;Woo, Jung-In
    • The Transactions of the Korean Institute of Electrical Engineers P
    • /
    • v.51 no.4
    • /
    • pp.175-185
    • /
    • 2002
  • In this paper, a new fully digital current control method of UPS inverter, which is based on an internal model control, is proposed. In the proposed control system, overshoots and oscillations due to the computation time-delay are compensated by explicit incorporation of the time-delay in the current control loop transfer function. The internal model controller is adopted to a second order deadbeat reference-to-output response which means that its response reaches the reference in two sampling time including computational time-delays. That is, the average current of filter capacitor is been exactly equal to the reference current with a time lag of two sampling intervals. Therefore, this method has an essentially overshoot free reference-to-output response with a minimum possible rise time. The effectiveness of the proposed control system has been verified by the simulation and experimental respectively. From the simulation and experimental results, the proposed system is achieved the robust characteristics to the calculation time delay and parameter variation as well as very fast dynamic performance, thus it can be effectively applied to the power supply for the critical load.

A New On-Line Dead-Time Compensator for Single-Phase PV Inverter (단상 PV 인버터용 온라인 데드타임 보상기 연구)

  • Vu, Trung-Kien;Lee, Sang-Hoey;Cha, Han-Ju
    • The Transactions of the Korean Institute of Power Electronics
    • /
    • v.17 no.5
    • /
    • pp.409-415
    • /
    • 2012
  • This paper presents a new software-based on-line dead-time compensation technique for a single-phase grid-connected photovoltaic (PV) inverter system. To prevent a short circuit in the inverter arms, a switching delay time must be inserted in the pulse width modulation (PWM) signals. This causes the dead-time effect, which degrades the system performance around zero-crossing point of the output current. To reduce the dead-time effect around the zero-crossing point of grid current, a harmonic mitigation of grid current is used as an additional part of the synchronous frame current control scheme. This additional task mitigates the harmonic components caused by the dead-time from the grid current. Simulation and experimental results are shown to verify the effectiveness of the proposed dead-time compensation method in the single-phase grid-connected inverter system.

An Experimental Study on Short Circuit Characteristics by the Interior Wiring Length (옥내배선 길이에 따른 단락 특성의 실험적 연구)

  • Song, J.Y.;Kim, J.P.;Cho, Y.J.;Choi, D.M.;Oh, B.Y.;Kil, G.S.
    • Journal of the Korean Society of Safety
    • /
    • v.27 no.4
    • /
    • pp.38-42
    • /
    • 2012
  • This paper describes electrical fire on residential environment such as apartment and detached house caused by defect of interior wiring. We carried out experimental study on short circuit characteristics by the interior wiring length. We were measured arc current, arc energy and interrupting time of earth leakage current circuit breaker(ELB), when an interior wiring break out short circuit in residential environment. From the experiment results, the longer of the interior wiring, the magnitude of arc current decreased and the interrupting time of ELB increased. When applied the A maker's ELB, the strength of arc current and interrupting time of ELB was 254 A and 245 ms respectively at 30 m interior wiring length. In 3 m interior wiring length, arc current and interrupting time was 716 A and 4.24 ms respectively. Arc energy was dependent on the magnitude of arc current and the interrupting time of ELB, the longer the interrupting time, arc energy increasing. In this paper, minimum arc energy was 277 J using C maker's ELB and 3 m interior wiring length(arc current 283 A, interrupting time of breaker 6.28 ms). Therefore in the residential environment, short circuit caused by defect of the interior wiring lead to electrical fire.

Fusing Time Characteristics Analysis of Cable according to Temperature and Insulator (온도 및 절연체에 따른 케이블의 단선시간 특성 해석)

  • Kim, Ju-Hee;Kang, Sin-Dong;Kim, Jae-Ho
    • Journal of the Korean Society of Safety
    • /
    • v.33 no.5
    • /
    • pp.15-20
    • /
    • 2018
  • This paper describes the fusing time characteristics of Light PVC Sheathed Circular Cord(VCTF) and Tray Frame Retardant(TFR) cables according to increased temperature under over current condition. The experimental equation will be used to determine the validity and reliability of the test results. The over current flowed 3, 5 and 10 times higher than the amount of allowable current using DC power supply with DAQ(Data Acquisition) measurement system. An infrared radiation heater, which was controlled by a variable AC auto transformer, was used to increase the temperature from room temperature to 50, 100 and 150 degrees Celsius. First, two type of cables were analyzed those with different cross-sectional areas with in the same structure and those with different structures with in the same cross-sectional areas. Then, it was determined how fusing time had been influenced according to the cross-sectional areas and different structures, respectively. The cable resistance was increased by joule heating according to increasing temperature. Therefore, the allowable current of cable is decreased. Finally, the fusing time of the cable was decreased due to increased temperatures at current flow, which were 3 times the amount of allowable current. The instantaneous breakdown was observed when current flow was 5 and 10 times over the amount of allowable current. The fusing time is directly affected by the structure of cable insulation.

Current Differential Relaying Algorithm for Power Transformer Protection Operating in Conjunction with a CT Compensating Algorithm (보상 알고리즘을 적용한 변압기 보호용 전류차동 계전방식)

  • Kang, Yang-Cheol;Park, Jong-Min;Lee, Mi-Sun;Jang, Sung-Il;Kim, Yong-Gyun;So, Soon-Hong
    • The Transactions of The Korean Institute of Electrical Engineers
    • /
    • v.56 no.11
    • /
    • pp.1873-1878
    • /
    • 2007
  • Current differential relays may maloperate during magnetic inrush and over-excitation because a significant differential current is produced. To prevent maloperation, the relays adopt some harmonic components included in the differential current. The harmonic restraints may increase the security of a relay but cause the operating time delay of a relay when an internal fault occurs. Moreover, the operating time delay is more increased if a current transformer (CT) is saturated. This paper describes a current differential relaying algorithm for power transformer protection with a compensating algorithm for the secondary current of a CT. The comparative study was conducted with and without the compensating algorithm. The performance of the proposed algorithm was investigated when the measurement CT (C400) and the protection CT (C400) are used. The proposed algorithm can compensate the distorted current of a CT and thus reduce the operating time delay of the relay significantly for an internal fault with CT saturation.

A Fast Response Integrated Current-Sensing Circuit for Peak-Current-Mode Buck Regulator

  • Ha, Jung-Woo;Park, Byeong-Ha;Kong, Bai-Sun;Chun, Jung-Hoon
    • JSTS:Journal of Semiconductor Technology and Science
    • /
    • v.14 no.6
    • /
    • pp.810-817
    • /
    • 2014
  • An on-chip current sensor with fast response time for the peak-current-mode buck regulator is proposed. The initial operating points of the peak current sensor are determined in advance by the valley current level, which is sensed by a valley current sensor. As a result, the proposed current sensor achieves a fast response time of less than 20 ns, and a sensing accuracy of over 90%. Applying the proposed current sensor, the peak-current-mode buck regulator for the mobile application is realized with an operating frequency of 2 MHz, an output voltage of 0.8 V, a maximum load current of 500 mA, and a peak efficiency of over 83%.

A Study on the Predictive Current Controller with the Compensation of Computation Time Delay in a Digital Control Systems (디지털 제어 시스템의 연산시간 지연을 고려한 예측전류제어기에 관한 연구)

  • Woo, Myung-Ho;Jeong, Seung-Gi
    • Proceedings of the KIEE Conference
    • /
    • 1997.07f
    • /
    • pp.2028-2032
    • /
    • 1997
  • When a high performance current control is desired, a computation time delay of a digital control system may deteriorate the control performance of a current controller. Such a non-negligible effect can be considerable in transient state. This paper deals with the modified predictive current control that compensates the time delay effects of a conventional predictive current control. The method is closely related to a local average current control and a symmetrical PWM pattern generation. Also some theoretical approaches are presented to describe the voltage saturation boundary of the power converter. For validation, the proposed method is applied to an active power filter system. The experimental results show considerable improvement in current tracking capability.

  • PDF

Average Current Control of Active Power Filters Using Predictive Current Controller (예측전류제어기를 이용한 능동전력필터 시스템의 평균치 전류제어)

  • Kim, Min-Keuk;Woo, Myung-Ho;Jeong, Seung-Gi;Park, Ki-Won;Choi, Chang-Ho
    • Proceedings of the KIEE Conference
    • /
    • 1996.07a
    • /
    • pp.295-299
    • /
    • 1996
  • When the current of a power converter is controlled with a digital controller, it generally shows the error due to execution time delay. The error may be considerable in such systems as active power filters wherein the current varies steeply even in steady state, as well as in transients. Therefore, it is of particular importance to compensate the time delay effect in a digitally-controlled active power filter. This paper introduces a modification of so-called predictive current control, by taking the control time delay into consideration. The results of simulation and experiment with a 10 kVA active power filter prototype show considerable improvement in current tracking capability, validating the proposed current control method.

  • PDF