• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1425-1437
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• 2018

In this paper, a methodology was proposed to reduce the electrical level and spatial size of the smart grid with distributed generations (DGs) to a scale in which the electrical phenomena and control strategies for disturbances on the smart grid could be safely and freely experimented and observed. Based on the design methodology, a micro smart grid simulator with a substation transformer capacity of 190VA, voltage level of 19V, maximum breaking current of 20A and size of $2{\times}2m^2$ was designed by reducing the substation transformer capacity of 45MVA, voltage level of 23kV and area of $2{\times}2km^2$ of the smart grid to over one thousandth, and also reducing the maximum breaking current of 12kA of the smart grid to 1/600. It was verified that the proposed design methodology and designed micro smart grid simulator were very effective by identifying how all of the fault currents are limited to within the maximum breaking current of 20A, and by confirming that the maximum error between the fault currents obtained from the fault analysis method and the simulation method is within 1.8% through the EMTP-RV simulation results to the micro smart grid simulator model.

• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.137-144
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• 2006

This paper proposes novel protection schemes for grid-connected distributed generation (DG) units using the fault location algorithm. The grid-connected DG would be influenced by abnormal distribution line conditions. Identification of the fault location for the distribution lines at the relaying point of DG helps solve the problems of the protection relays for DG. The proposed scheme first identifies fault locations using currents and voltages measured at DG and source impedance of distribution networks. Then the actual faulted feeder is identified, applying time-current characteristic curves (TCC) of overcurrent relay (OCR). The method considering the fault location and TCC of OCR might improve the performance of the conventional relays for DG. Test results show that the method prevents the superfluous operations of protection devices by discriminating the faulted feeder, whether it is a distribution line where DG is integrated or out of the line emanated from the substation to which the DGs are connected.

• KIEE International Transactions on Power Engineering
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• 제3A권4호
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• pp.198-205
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• 2003

This paper proposes the adaptive relaying of protective devices applied in the neighboring distribution feeders for reliable and efficient operations of a wind farm interconnected with distribution networks by dedicated lines. A wind farm connected to an electric power network is one of the greatest alternative energy sources. However, the wind turbine generators are influenced by abnormal grid conditions such as disturbances occurring in the neighboring distribution feeders as well as the dedicated power. Particularly, in cases of a fault happening in the neighboring distribution feeders, a wind farm might be accelerated until protective devices clear the fault. Therefore, the delayed operation time of protective devices for satisfying the coordination might overly expose the interconnected wind turbine generators to the fault and cause damage to them. This paper describes the proper delayed operation time of protective relay satisfying the coordination of the distribution networks as well as reducing damage on the interconnected wind farm. The simulation results for the Hoenggye substation model composed of five feeders and one dedicated line using PSCAD/EMTDC showed that the proper delayed time of protective devices reflecting the fault condition and the power output of the wind farm could improve the operational reliability, efficiency, and stability of the wind farm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.399-402
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• 2003

In this paper, the on line volt/var control algorithms of the food Load Tap Changer (LTC) transformer and Shunt Capacitor(SC) are proposed for distribution volt/var regulation. In the existing volt/var control of the distribution substation, the voltage of feeders and var of distribution systems is mainly controlled by the LTC transformer tap position and on/off status of the shunt capacitor. The LTC and shunt capacitor bank has discrete operation characteristics and therefore it is very difficult to control volt/var at the distribution networks within the satisfactory levels. Also there is limitation of the operation times of the LTC and shunt capacitor bank because it is affects on their functional lifetime. The proposed volt/var control algorithm determine an optimal tap position of LTC and on/off status of shunt capacitors at a distribution network with the multiple feeders. The mathematical equations of the proposed method are introduced. Simple case study was performed to verify the effectiveness of the proposed method.

• 전기학회논문지
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• 제61권10호
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• pp.1412-1419
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• 2012

In this paper, we propose the protection coordination algorithm using communication methode based on IEC 61850. The communication protocol in power distribution management system has been issued by IEC standard, IEC61850 of them, which was made for substation automation system, has researched to apply into power distribution system, even though the standard is not a suitable for the system. In smart distribution management system' launched in 2009, the communication network based on the ethernet network for IEC 61850 has been designed to apply the self-healing concept, which is to perform the system protection through the communication between remote terminal units(RTU) according to the standard. However, it is first time to apply the scheme in the real. Thus, this paper proposed the protection algorithm and consideration for applying communication method and introduced the result of demonstration.

• 한국초전도ㆍ저온공학회논문지
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• 제7권1호
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• pp.37-41
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• 2005

This paper describes the construction scheme of new distribution system using HTS(High Temperature Superconducting) power equipments such as cable, transformer and FCL(fault current limiter). At present, one of the most serious problems in distribution power system, especially for metropolitan complex city, is to obtain the ROW for cable line routes, space for downtown substations and satisfy the environmental protection caused by NIMBY phenomena. Unfortunately, it is expected that this situation will get more and more worse. As the HTS technology to apply in power system Is developed, HTS cable utilizing mass-capacity characteristic can be a useful countermeasure to overcome this problem. This paper describes the application methodology of 22.9kV HTS cable with low-voltage, mass-capacity characteristics replacing the 154kV conventional cable. By applying 22.9kV HTS cable, the HTS transformer with higher capacity for the reduction of space and transformer numbers of downtown substation is necessary. Also, if the leakage Impedance of HTS transformer is same as or lower than that of conventional transformer, the fault current of 22.9kV bus will increase because the HTS transformer capacity is larger than that of the conventional transformer. This means the parallel application of HTS-FCL to reduce the fault current in addition to the HTS cable and transformer can be necessary. With the basic construction scheme of new distribution system, this paper describes the future study points to realize this new distribution system using HTS equipments.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제10권7호
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• pp.199-204
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• 2021

디지털변전소는 전력망 지능화를 위해 감시, 계측, 제어·보호, 운전 등 변전소를 구성하는 전력설비 기능과 통신방식을 국제표준인 IEC61850 기반으로 디지털화한 변전소를 말한다. 지능화된 운영시스템을 기반으로 효율적인 전력설비의 감시제어가 가능하며, 사고 발생 시 자동 복구 기능과 원격제어가 가능해 신속한 전력 장애 복구가 가능하다. 디지털 기술의 발달과 친환경 신재생에너지 및 전기차의 도입이 확대 되면서 직류 배전시스템의 보급이 확대될 전망이다. MVDC는 기존 송전계통에 적용되는 HVDC와 수용가에서의 LVDC 사이의 전압 레벨 및 전송용량을 갖는 직류 선로를 활용한 시스템이다. 대부분의 전력설비들이 교류 중심인 기존변전소의 기존 선로를 직류 선로로 변환하면 송전 손실 감소 및 더 큰 전류 용량이 확보된다. 디지털변전소의 프로세스 버스는 베이 레벨과 프로세스 레벨의 설치된 장치 간을 연결하는 이더넷스위치 등의 통신장비로 구성된 통신네트워크이다. 기존 디지털변전소에 MVDC 연계를 위해 프로세스 레벨을 교류부와 직류부로 나누어 두 개의 버스로 구성을 하였고 감시, 제어만 아니라 진단 IED와 연계되어 종합적으로 관리할 수 있는 시스템을 제안하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.74_76
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• 2009

This paper presents a discrete wavelet analysis based algorithm to address the fault impedance calculation under transient state in radial power distribution networks. The fault impedances have been derived under different fault conditions. Furthermore, a recursive fault distance estimation method is proposed utilizing the measured fault impedance and power line parameters. The proposed scheme can resolve the errors caused by the non-homogeneous power lines, the presence of lateral loads since, the fault impedance will always be updated with the recursive form. For the verification of the proposed scheme, a filed test has been peformed with varying fault resistances in the 22.9(kV) radial system. Power meters and fault locators were installed at the substation. It was figured out that the performance of the discrete wavelet and the recursive scheme are very good even for high fault resistance condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.159_160
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• 2009

In this paper proposes a new algorithm of efficiency outage restoration using a outage load switching to a healthy MTR a fault occurrence at a MTR. In addtion, proposed algorithm includes a outage restoration method which keeps MTR optimal capacity with reorganization of distribution network in case it can not restore outage state loads caused by shortage of healthy MTR remain capacity. In case that proposed sequence still can not complete restoration, this paper suggests a efficiency outage restoration with objective function included priority in outage loads.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.495-498
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• 2001

The distribution line through which electricity is supplied from substation to customer generally varies by underground line and overhead line. In contrast that the underground line is shielded, the overhead lines do not have the shield layer. To overcome this weak point of the overhead lines, the aerial bundled cable(ABC) connection systems have been developed. The basic concept of the ABC connection system is the application of the underground cable system containing complete shield layer to the overhead cable system. The ABC system is the innovative technologies which enable the prevention of electric shocks, reduction of the maintenance charge and damage of the cable. This paper give a full detail of vertical connection system applied within a country.