• KIEE International Transactions on Power Engineering
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• v.3A no.1
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• pp.7-16
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• 2003

A new method to evaluate the protection capability of distribution systems is reported in this paper. This work describes the fuzzy evaluation attributes and aggregation method of evaluation results based on a hierarchical model and the modified combination rule. An evaluation grade index called "protectability" is proposed and is expected to be a very uscful tool in defining an optimal protection and realizing the adaptive protection.rotection.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.6
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• pp.1129-1138
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• 2019

Since substations are structurally complex due to the concentration of protection coordination facilities with substation facilities for long distance power transmission, it is difficult to design a protection coordination system to minimize the spreading effect of the fault when a fault occurs on transmission line or distribution line. Therefore, in this paper, the bus configuration and the basic logic of protection coordination that have a major influence on the reliability of substation power supply were analyzed, and the substation protection coordination logic to detect internal and external faults was developed based on EMTP-RV. As the basic logic of substation protection coordination, the percent differential protection relay logic for substation internal fault detection and the overload protection relay logic for inference of external failure were modeled. Finally, the 154kV substation including the protection coordination logic was modeled using EMTP-RV, and the effectiveness of the protection coordination design methodology was confirmed through the several fault simulation cases based on EMTP-RV.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.2
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• pp.85-92
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• 2016

The paper presents a method to assess system voltage sag performance considering sag durations as well as magnitudes. In general, voltage sag assessment for large power systems is performed only considering sag magnitudes at sensitive load points. However some equipment can be affected by certain sag durations. The duration of the voltage sag is depend on the time of fault current flow in the system. Therefore, the duration can be determined by analyzing the operating characteristic of the protection system. In this paper, an effective method to evaluate sag durations regarding the characteristics and failure rates of the protection system is described. The proposed method can be used to assess the long-term performance of the voltage sags in large power system.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.533-535
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• 2002

In Korea, power requirement has been increasing. But the large generation unit is hardly installed because of economic and environment problem. Therefore, the concern of dispersed generation system(DGS) is growing. The power distribution system is generally operated with radial type. The protection system is composed of one directive source. But power distribution system inserted DGS changes it to two directive source system. Therefore, the insertion of DGS has the problem of protection coordination. In this paper, we argue fault current affected by interconnected DGS. We analyze fault current flow affected by DGS placement. Then, we find protective coordination problem. Consequently, we study advance point for protection scheme of power system interconnected DGS.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.543-547
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• 2001

A protection scheme for Unified Power Quality Conditioner (UPQC) is presented and analyzed in this paper. The proposed UPQC has the series active power filter operated as a high impedance k($\Omega$) to the fundamentals when short-circuit faults occur in the power distribution system, and three control strategies are proposed in this paper. The first is the method by detecting the fundamental source current through the p-q theory, the second is the method by detecting the fundamental component of load current in Synchronous Reference Frame(SRF) and the third is the method by detecting the input voltage. When the short-circuit fault occur in the power distribution system, the proposed scheme protects the UPQC without additional protection circuits. The validity of proposed protection scheme is investigated through simulation results.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.736-740
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• 2004

In order to overcome the problems of simulation methods, the power system transient stability assessment method using critical fault clearing time functions has been developed. Using the above method, this paper has developed the new method which can assess accurately and efficiently the effects of control and protection systems on transient stability which is the most important characteristic to assess in power systems. At first, critical fault clearing time functions CCT(W:load) are defined by taking notice of the fact that transient stability is mainly controlled by fault clearing time and load. Next, the method to be enable to assess accurately and efficiently the effects of control and protection systems on transient stability has been newly developed by using the above functions. Finally, it has been applied to the effect assessment in the occurrence of a three-phase fault in a model power system. Results of application have been clarified its effectiveness.

• Corrosion Science and Technology
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• v.14 no.1
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• pp.12-18
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• 2015

Since the operation period of nuclear power plants has increased, the degradation of buried pipes gradually increases and recently it seems to be one of the emerging issues. Maintenance on buried pipes needs high quality of management system because outer surface of buried pipe contacts the various soils but inner surface reacts with various electrolytes of fluid. In the USA, USNRC and EPRI have tried to manage the degradation of buried pipes. However, there is little knowledge about the inspection procedure, test and manage program in the domestic nuclear power plants. This paper focuses on the development and build-up of real-time monitoring and control system of buried pipes. Pipes to be tested are tape-coated carbon steel pipe for primary component cooling water system, asphalt-coated cast iron pipe for fire protection system, and pre-stressed concrete cylinder pipe for sea water cooling system. A control system for cathodic protection was installed on each test pipe which has been monitored and controlled. For the calculation of protection range and optimization, computer simulation was performed using COMSOL Multiphysics (Altsoft co.).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.4
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• pp.47-53
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• 2015

The electrical safety and efficiency is the most important thing of the electric vehicle charging system. The prior system is contact charging system that is contacted directly by human. So, it has riskiness such as electric shock in the case of poor insulation or contact problems. To solve these safety issues and the convenience problems, a wireless power transmission system has been developed and is currently in trial operation. However, because high frequency is used in wireless power transmission system instead of commercial frequency, we need to apply protection measures concerning electric shock and equipment protection. Also, it should be accompanied by measuring efficiency for the effective operation of the wireless power transmission system. Therefore, we structured monitoring system in trial operation area of wireless power transmission system and applied decision algorithm for protection of human and equipment and economic operation of it.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1727-1731
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• 2003

In this paper we proposed backward fuzzy Petri-net to diagnoses faults in power systems by using the time sequence information of protection system. As the complexity of power systems increases, especially in the case of multiple faults or incorrect operation of protective devices, fault diagnosis requires new and systematic methods to the reasoning process, which improves both its accuracy and its efficiency. The fuzzy Petri-net models of protection system are composed of the operating process of protective devices and the fault diagnosis process. Fault diagnosis model, which makes use of the nature of fuzzy Petri-net, is developed to overcome the drawbacks of methods that depend on operator knowledge. The proposed method can reduce processing time and increase accuracy when compared with the traditional methods. And also this method covers online processing of real-time data from SCADA (Supervisory Control and Data Acquisition)

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.10
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• pp.102-108
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• 2011

The existing power flow has a single direction to the line end but the bidirectional power flow will possibly occur depending on the output capacity in the 22.9[kV] distribution power system connected with the dispersed generation(DG). So these characteristics would influence the power system management. The DG have many advantages such as assistance source, Load share etc. So the utility must apply the bidirectional protection system so as to maximize an advantage of DG. This paper describes the field test case of bidirectional protective device in order to investigate the device performance when applied to bidirectional power system. We have tested in the power system test site of KEPCO and these tests provide the basis for performance verification test of bidirectional protective device in the power system.