Il-Hyung Lim

Security Protocols Against Cyber Attacks in the Distribution Automation System

As a communication technology plays an integral part in a power system, security issues become major concerns. This paper deals with the security problems in the distribution automation system (DAS) which has an inherent vulnerability to cyber attacks due to its high dependency on the communication and geographically widely spread terminal devices. We analyze the types of cyber threats in many applications of the distribution system and formulate security goals. Then we propose an efficient security protocol to achieve these goals. The protocol avoids complex computation of any encryption algorithm, considering resource-constraint network nodes. We also propose a secure key distribution protocol. Finally, we demonstrate the feasibility of the proposed security protocol by experiments.

Distributed Restoration system applying Multi-Agent in distribution automation system

In this paper, as make up for the weak points of the centralized restoration in DAS, distributed restoration method applying multi-agent is proposed for increasing the efficiency and saving time of the restoration time of blackouts. Distribution restoration method is difficult to deal with a fault quickly because DAS manage, judge and order the states of distribution network after gathering all information from FRTUs when the fault occurs. If Feeder Remote Terminal Unit (FRTU) in distribution network performs restoration and separates minimized fault section itself by exchanging information using communication to each other, the efficiency and time of the restoration can be enhanced by much. In the case studies, this paper is proposed a distributed restoration method which can make up the weak points of the centralized restoration in DAS by converting FRTUs into multi-agents. The proposed method has been testified in Gochang power test field in Korea and the result in the restoration shows its performance.

Multi-Agent System-based Protection Coordination of Distribution Feeders

A protection system adopting multi-agent concept for power distribution systems is proposed. A device agent, embedded in a protective device, detects faults or adapts in the network in an autonomous manner and changes its operating parameters to new operation conditions by collaborating with other protection agents. Simulations of the agents and their operations for a sample distribution system with a variety of cases show the feasibility of the agent-based adaptive protection of distribution networks.

Applying security algorithms against cyber attacks in the distribution automation system

As the communication technology weighs heavily in the power system, so the security issues becomes major concerns. So far most security research has focused on the SCADA system. In this paper we consider the security problems in the network environment of the distribution automation system (DAS) which is much different from the SCADA system. First we analyze the types of cyber threats in many applications of the distribution system, and formulate the security goals. Then we propose the efficient security algorithms to achieve these goals. The algorithm avoids complex computation of any encryption algorithm, considering the resource-constraint network nodes. We also propose the efficient secret key distribution algorithm without resort to the public key encryption. Finally we demonstrate the feasibility of the proposed security protocol by experiment.

A Robust Fault Location Algorithm for Single Line-to-ground Fault in Double-circuit Transmission Systems

This paper proposes an enhanced noise robust algorithm for fault location on double-circuit transmission line for the case of single line-to-ground (SLG) fault, which uses distributed parameter line model that also considers the mutual coupling effect. The proposed algorithm requires the voltages and currents from single-terminal data only and does not require adjacent circuit current data. The fault distance can be simply determined by solving a second-order polynomial equation, which is achieved directly through the analysis of the circuit. The algorithm, which employs the faulted phase network and zero-sequence network with source impedance involved, effectively eliminates the effect of load flow and fault resistance on the accuracy of fault location. The proposed algorithm is tested using MATLAB/Simulink under different fault locations and shows high accuracy. The uncertainty of source impedance and the measurement errors are also included in the simulation and shows that the algorithm has high robustness.

Intelligent Distributed Restoration by Multi-Agent System Concept in DAS

This paper is proposed a method to improve Distribution Automation System (DAS) restoration efficiency by including Multi-Agent System (MAS) and changing from centralized to distributed system. Multi-Agent concept in this paper is defined by a notion from the IEEE Power Engineering Societys (PES) Intelligent System Subcommittee (within the PSACE Committee) Working Group. Intelligent Distributed Restoration is a novel restoration method to use mutual information exchange, automatic fault section separation, and more quick, reliable, exactly restoration. Its suggested some application methods for distributed restoration including MAS in DAS. Proposed system is proved by field test at Gochang field test center in Korea and integrating in DAS for future (IDMS: Intelligent Distribution Management System).

An Intelligent Fault Detection and Service Restoration Scheme for Ungrounded Distribution Systems

Electric load components have different characteristics according to the variation of voltage and frequency. This paper presents the load modeling of an electric locomotive by the parameter identification method. The proposed method for load modeling is very simple and easy for application. The proposed load model of the electric locomotive is represented by the combination of the loads that have static and dynamic characteristics. This load modeling is applied to the KTX in Korea to verify the effectiveness of the proposed method. The results of proposed load modeling by the parameter identification follow the field measurements very exactly.

A fault section detection method using ZCT when a single phase to ground fault in ungrounded distribution system

A single line to ground fault (SLG) detection in ungrounded network is very difficult, because fault current magnitude is very small. It is generated by a charging current between distribution line and ground. As it is very small, is not used for fault detection in case of SLG. So, SLG has normally been detected by switching sequence method which makes customers experience blackouts. A new fault detection algorithm based on comparison of zero-sequence current and line-to-line voltage phases is proposed. The algorithm uses ZCT installed to ungrounded distribution network. The proposed in this paper algorithm has the advantage that it can detect fault phase and distinguish a faulted section as well. The simulation tests of proposed algorithm were performed using Matlab Simulink and the results are presented in the paper.

Ungrounded System Fault Section Detection Method by Comparison of Phase Angle of Zero-Sequence Current

In this paper, an integrated fault section detection and isolation strategy is proposed based on the application of the Distribution Automation System (DAS) utilizing advanced IT and communication technologies. The Feeder Remote Terminal Unit (FRTU) has been widely used to collect data in the Korean distribution system. The achieved data is adopted in this method for detecting multiple fault types. Especially in the case of single phase-to-ground fault, the fault section is detected by comparison of the zero-sequence current phase angle. The test results have verified the effectiveness of the proposed method in a radial distribution system through extensive simulations in Matlab/Simulink. Furthermore, a communication-based demo system identical to the simulation model has been developed, and it can be applied as an online monitoring and control program for fault section detection and isolation.

Load Flow Analysis for Distribution Automation System based on Distributed Load Modeling

In this paper, a new load flow algorithm is proposed on the basis of distributed load modeling in radial distribution networks. Since the correct state data in the distribution power networks is basic for all distribution automation algorithms in the Distribution Automation System (DAS), the distribution networks load flow is essential to obtain the state data. DAS Feeder Remote Terminal Units (FRTUs) are used to measure and acquire the necessary data for load flow calculations. In case studies, the proposed algorithm has been proven to be more accurate than a conventional algorithm; and it has also been tested in a simple radial distribution system.