• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.454-455
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• 2010

This paper surveys recent works in line impedance estimation. Inverters used in distribution system are often connected to the grid through LCL filter. Different methods are investigated for estimating the line impedance. Advantages and disadvantages with brief summary for each method are presented. Simulation results for a specified grid are shown for two main different methods and the results are compared with estimation error.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.65-75
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• 2016

Aiming at analyzing the power flow of the distribution systems with distribution transformer (DT) branches and PV nodes, a hybrid three-phase power flow methodology is presented in this paper. The incidence formulas among node voltages, loop currents and node current injections have been developed based on node-branch incidence matrix of the distribution network. The method can solve the power flow directly and has higher efficiency. Moreover, the paper provides a modified method to model DT branches by considering winding connections, phase shifting and off-nominal tap ratio, and then DT branches could be seen like one transmission line with the proposed power flow method. To deal with the PV nodes, an improved approach to calculate reactive power increment at each PV node was deduced based on the assumption that the positive-sequence voltage magnitude of PV node is fixed at a given value. Then during calculating the power flow at each iteration, it only needs to update current injection at each PV node with the proposed algorithm. The process is very simple and clear. The results of IEEE 4 nodes and the modified IEEE 34 nodes test feeders verified the correctness and efficiency of the proposed hybrid power flow algorithm.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2001.11a
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• pp.51-58
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• 2001

This paper gives a type and high-frequency waves analysis of in-rush current cab be flowed into distribution automatic machine to be installed in distribution line in order to use minimizing operation error of failure indicator to have been issue recent with obtaining high-frequency component that can be different from current. The in-rush and fault current data studied in this paper is to be surveyed actually in USA distribution system substation line of Bryan Power Company near Texas A. M University, to be occurred high impedance fault.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.50-50
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• 2002

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.62.1-62
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• 2002

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2619-2627
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• 2009

The ground fault is occupying 70% among the total number of faults in ungrounded distribution power system. When the ground fault occurs in ungrounded system, the fault current is so small that it is hard to detect. But fault handling is very important because to continue power supply during fault conditions may cause the fault spreading and the distribution device in trouble. This paper presents the fault line detection method by using GPT signal detecting zero sequence voltage, and the fault section detection method by detecting whether GPT signal is disappeared or not during shifting normally open switch, which is connecting switch between distribution lines with open state in order to restore the outage area under emergency situation, and during isolating each section one by one which belongs to the fault line. This method is efficient because there is no whole power interruption during the fault section detection, and it is possible to perform both the fault section detection and the service restoration for the outage area at the same time, and it can apply to various distribution system configuration. Program for the fault restoration was developed applying proposed method, and it has been validated by applying to the pilot project of distribution automation system in Vietnam which has the ungrounded distribution system.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.11
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• pp.610-618
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• 2004

With the development of industry and the improvement of living standards, better quality in power electric service is required more than ever before. Under these circumstances, to deliver reasonable voltage regulation methods in distribution systems need to be developed. So, This paper deals with optimal introduction of the line voltage regulator (SVR : Step Voltage Regulator) in power distribution systems. First, This paper investigates characteristics of SVR and performs economic evaluation of SVR's introduction by using Present Worth Method. This paper, also suggests proper location and optimal voltage regulation algorithm. In order to deliver suitable voltages to as many customers as possible, the optimal sending voltage of SVR should be decided by the effective operation of voltage regulators at the distribution feeders. The simulation results using a model distribution system and real distribution systems show that the proposed methods can be a practical tool for the voltage regulation in distribution systems.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.114-120
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• 2004

The paper proposes a method calculate the allocations of real power losses in transmission lines to individual loads based on loss distribution factors and compares them with those using marginal loss factors. The proposed method is implemented by defining loss distribution factors and analysing the individual loads' shares in the transmission line losses. Computer simulations on a 9-bus sample system verify effectiveness of the algorithm proposed and give an assertion that it is desirable to allocate power losses to loads using loss distribution factors rather than based on marginal loss factors.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.7
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• pp.355-362
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• 2003

The fault analysis problem of a distribution network has many difficulties comes from the unbalance of loads or networks and the lacks of load information. The unbalance of loads or networks make the fault location difficult when it use the classical sequence transformation. Moreover the amount of load in the distribution networks fluctuates with time. This paper introduces a recent fault location algorithm using iterative method which handle the unbalance of the problem. But, the fault location errors comes from the load fluctuations still left. For the real application of the new fault location algorithm in distribution networks, this paper studied the effect of the load fluctuations in the algorithm.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.102-104
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• 2005

This paper describes the model of the distribution grid for the broadband power line communication based on lumped-element circuits. In addition, this paper discusses various configurations of the MV distribution network in PLC. The distribution grid is not designed for communication so that it involves unfriendly conditions for PLC. The characterization of the MV distribution grid for PLC should be determined such as noise, attenuation, and mismatched impedance. For theses reasons, the PLC networks is described in using the scattering parameters. Finally, the n-port network is explained.