• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1123-1128
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• 2008

The necessity of online dynamic security assessment is getting apparent under Electricity Market environments, as operation of power system is exposed to more various operating conditions. For on-line dynamic security assessment, fast transient stability analysis tool is required for contingency selection. The TEF(Transient Energy Function) method is a good candidate for this purpose. The clustering of critical generators is crucial for the precise and fast calculation of energy margin. In this paper, we propose a new method for fast decision of mode of instability by using stability indices and energy margin. The method is a new version of our previous paper.[1] Case studies are showing very promising results.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1798-1806
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• 2018

When a contingency occurs in a large transmission route in a power system, it can generate various instabilities that may lead to a power system blackout. In particular, transient instability in a power system needs to be immediately addressed, and preventive measures should be in place prior to fault occurrence. Measures to achieve transient stability include system reinforcement, power generation restriction, and generator tripping. Because the interpretation of transient stability is a time domain simulation, it is difficult to determine the efficacy of proposed countermeasures using only simple simulation results. Therefore, several methods to quantify transient stability have been introduced. Among them, the single machine equivalent (SIME) method based on the equal area criterion (EAC) can quantify the degree of instability by calculating the residual acceleration energy of a generator. However, method for generator tripping effect evaluation does not have been established. In this study, we propose a method to evaluate the effect of generator tripping on transient stability that is based on the SIME method. For this purpose, the measures that reflect generator tripping in the SIME calculation are reviewed. Simulation results obtained by applying the proposed method to the IEEE 39-bus system and KEPCO system are then presented.

• 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.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.239-241
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• 2003

The time domain simulation method of transient stability presents accuracy and reliability, but it demands much computational time. Therefore it is necessary to filter out very stable and very unstable cases from a large set of contingencies. Following a disturbance, the shape and magnitude of representative generator angle which is most increased after fault clearing are the measure of transient stability. This paper propose a method that is not a calculation of the exact CCT of contingency, but a fast assessment of transient stability. Also it can help operators identify transient stability immediately without analyzing the graphical results. The proposed method is applied to the KEPCO system. The PSS/E is used as a time domain simulation engine by IPLAN.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.9
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• pp.441-448
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• 2005

On-line dynamic security assessment is becoming more and more important for the stable operation of power systems as load level increases. The necessity is getting apparent under Electricity Market environments, as operation of power system is exposed to more various operating conditions. For on-line dynamic security assessment, fast transient stability analysis tool is required for contingency selection. The TEF(Transient Energy Function) method is a good candidate for this purpose. The clustering of critical generators is crucial for the precise and fast calculation of energy margin. In this paper, we propose a new method for fast decision of mode of instability by using stability indices. Case study shows very promising results.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.5
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• pp.225-233
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• 2001

SIME(SIngle Machine Equivalent) method has been recognized as a useful tool to determine transient stability of power systems. In this paper, SIME method is used to develop the KEPCO transient stability assessment (TSA) tool. A new screening algorithm that can be implemented in SIME method is proposed. The salient feature of the proposed screening algorithm is as follows. First, critical generators are identified by a new index in the early stage of the time domain simulation. Thus, computational time required to find OMIB(One Machine Infinite Bus) can be reduced significantly. Second, clustering critical machines can be performed even in very stable cases. It enables to be avoid extra calculation of time trajectory that is needed in SIME for classifying the stable cases. Finally, using power-angle trajectory and subdividing contingency classification have improved the screening capability. This algorithm is applied to the fast TSA of the KEPCO system.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.131-136
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• 1995

This paper presents a functional ability improvement of auto-reclosing relay in the power transmission line protection. When the high speed auto-reclosing is successful, Auto-reclosing is practically valuable to improve the transient stability limit of a power system, but it is fail due to surviving fault, both electrical and mechanical stresses can result on the transformers and turbine-generator. It is true that the longer dead time of the reclosing relay gives the higher rate of successful reclosing, On the other hand, the power system does not always need high speed reclosing because of enough stability margin. This paper proposed "stability margin based dead time reclosing" in order to decrease not only the rate of unsuccessful reclosing, but the possibility of the harmful stress also. On-line transient stability assessment using artificial neural network, for implementing the proposed scheme, has studied and tested with resonable results.

• Journal of KIEE
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• v.11 no.1
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• pp.55-61
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• 2001

SIME(Single Machine Equivalent) method has been recognized as a useful tool to determine transient stability of power system. In this paper, SIME method is used to develop the KEPCO transient stability assessment (TSA) tool. A new screening algorithm that can be generators are identified by a new index in the early stage of the time domain simulation. Thus, computational time require to find OMIB(One Machine Infinite Bus) can be reduced significantly. Second, clustering critical machines can be performed even in very stable cases. It enables to be avoid extra calculation of time trajectory that is needed in SIME for classifying the stable cases. This algorithm is applied to the fast TSA of the KEPCO system in the year of 2010.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.4
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• pp.567-575
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• 2008

Transient security assessment(TSA) is becoming an essential requirement not only for security monitoring but also for stabilizing control of power systems under new electricity environments. It has already been pointed out that fast transient stability study is an important part for monitoring and controlling system security. In this paper, we discuss an energy function method for stabilizing control of transiently unstable systems by introducing generator tripping system to enhance the transient stability of power systems. The stabilization with less tripped power can be obtained by tripping the generators faster than out-of-synchronism relay. Fast transient stability assessment based on the state estimation and direct transient energy function method is an important part of the stabilizing scheme. It is possible to stabilize the transiently unstable system by tripping less generators before the action of out-of-synchronism relay, especially when a group of generator are going to be out-of-synchronism. Moreover, the amount of generator output needed for tripping can be decided by Transient Energy Function(TEF) method. The main contribution of this paper is on the stabilizing scheme which can be running in the Wide Area Control System.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.94-100
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• 2008

Available transfer capability(ATC) quantifies the viable increase in real power transfer from one point to another in a power system. ATC calculation has predominantly focussed on steady-state viability. But ATC assessment with transient stability constraints has a dominant part in overall ATC calculation. ATC assessment requires a reputation of (n-1) security assessment with constraints of thermal limits, voltage stability and dynamic stability. An estimation of determinant contingency screening method is used for computing eigenvalue of Jacobian matrix. This paper proposed a methods to ATC calculation using energy function. Constraints is used thermal limits, voltage stability and transient stability.