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Reliability evaluation of a large composite power system involves the consideration of numerous outage events and consequently extensive calculations. Therefore, applying justifiable simplifications such as the determination of an equivalent networks can be very useful in reliability evaluation of large systems. This paper presents a review of procedures which are directly or indirectly applicable to the determination of composite system adequacy equivalents. Following a brief discussion on the basic characteristics of the various methods, their limitations are presented. Concluding points regarding the methods and modeling schemes related to adequacy equivalent are presented at the end of... 

In many applications, the requirements of static data and large computation times are still major concerns. This paper presents a practical equivalent model of a small area in a large scale system which needs less statistical data of system equipments with acceptable level of accuracy. The proposed technique is designated as the Branch-Cutting Method in which tie lines between the area of interest (AI) and the other parts of the network are cut and the network behavior is modeled with some load and generating units in marginal load points. The load at marginal load points is represented as a multi state load model with the associated state probability. Load uncertainty is modeled using the... 

Electricity companies have been under a great pressure to improve their technical and financial performances in order to survive and thrive in the deregulated environment. Therefore, these companies are seeking for innovative approaches to take the most out of the restricted resources. These approaches inherently concentrate the available budgets to the most critical components. In this regard, prioritizing the system components and identifying the most critical ones play a vital role in the planning and operation of the system. This paper presents a novel approach to prioritize power transmission system components. In the proposed methodology, a criticality factor is defined and implemented... 

Variability and uncertainty of wind and photovoltaic (PV) generations greatly influence technical and financial aspects of power systems. This paper examines the potential impacts of large-scale wind and PV farms on reliability level of composite generation and transmission systems. At first, reliability models of renewable-based units are developed. In these models, both component failure rates and uncertainty nature of renewable resources are taken into account. Using the proposed technique, the multi-state analytical models of a wind farm placed in Manjil and a PV farm placed in Jask both in Iran are extracted. Then, reliability studies of high renewable-energies penetrated power system... 

Well-Being reliability indices (Health, Margin and Risk), provide a comprehensive measure to assess the adequacy of composite power systems. Conventional reliability information about power system operation only considered health and risk states, which were not often adequate criteria in both power system planning and operation. Well-being approach for power system generation adequacy evaluation incorporates deterministic criteria in a probabilistic framework, and provides system operating information in addition to risk assessment and can be evaluated using analytical techniques. The most important part of this approach is the algorithm for calculating the probability of the states.... 

Variability and uncertainty of wind and photovoltaic (PV) generations greatly influence technical and financial aspects of power systems. This paper examines the potential impacts of large-scale wind and PV farms on reliability level of composite generation and transmission systems. At first, reliability models of renewable-based units are developed. In these models, both component failure rates and uncertainty nature of renewable resources are taken into account. Using the proposed technique, the multi-state analytical models of a wind farm placed in Manjil and a PV farm placed in Jask both in Iran are extracted. Then, reliability studies of high renewable-energies penetrated power system... 

The modeling and evaluation of enormous numbers of contingencies are the most challenging impediments associated with composite power system adequacy assessment, particularly for large-scale power systems. Optimal power flow (OPF) solution, as a widely common approach, is normally employed to model and analyze each individual contingency as an independent problem. However, mathematical representations associated with diverse states are slightly different in one or a few generating units, line outages, or trivial load variations. This inherent attribute brings a promising idea to speed up the contingency evaluation procedure. In this paper, postoptimal analysis (POA), as a well-recognized... 

The paper illustrates an extended effective load model including the capacities and uncertainties of generators and transmission lines. The conventional effective load model only considers the uncertainties of generators. An extended ELDC (effective load duration curve) based on the effective load model is proposed in the paper. The proposed nodal ELDC is able to supply information on nodal indices for probabilistic production cost simulation and reliability evaluation at the load points in a power system. It is expected that the effective load model presented in the paper will prove useful in many problems dealing with nodal and decentralised operation and control of electric power systems... 

Considerable attention has been devoted to demonstrate reliability enhancement of power systems with power wheeling transactions. The impacts of power wheeling on power systems depends on various factors such as direction, amount of power/energy wheeled, system topology and sink or source nodes of power system. The effects on Iran Composite Power System (ICPS) reliability of wheeling energy from Azerbaijan to Turkmenistan are presented in this paper. This transaction is done through the transmission facilities on north part of ICPS. The sensitivity of ICPS to the direction and amount of power wheeling is attended. Finally, the optimum value for power wheeling is determined and the associated... 

In this paper, Bayesian Network (BN) is used for reliability assessment of composite power systems with emphasis on the importance of system components. A simple approach is presented to construct the BN associated with a given power system. The approach is based on the capability of the BN to learn from data which makes it possible to be applied to large power systems. The required training data is provided by state sampling using the Monte Carlo simulation. The constructed BN is then used to perform different probabilistic assessments such as ranking the criticality and importance of system components from reliability perspective. The BN is also used to compute the frequency and... 

Reliability assessment of power systems is very vital particularly in the market-driven environment. As the power systems are nonlinear and large-scale systems, extracting their reliability indices involves much uncertainty. Calculation of power system reliability using stochastic methods is a complex and relatively difficult procedure. However, using fuzzy logic methods it would be possible to calculate the reliability in accordance with the existing uncertainties. In this paper, a new fuzzy logic based method is proposed to calculate the reliability indices of composite power systems. Then, the suggested method is examined on a sample network as a case study. © 2007 IEEE