The physical environment in which a transmission and distribution system resides has a significant impact on the resulting reliability of the network. The inclusion of weather conditions in the reliability analyses of transmission and distribution systems is discussed. A series of weather models is presented with application to a practical transmission/distribution system. The conventional approach to predictive reliability assessment using single- and two-state weather models is briefly illustrated. A three-state weather model is presented to incorporate failures occurring in major adverse weather conditions. The system reliability indices obtained using the weather models clearly show the need to incorporate weather effects into reliability analyses. Results obtained without weather considerations can be quite misleading and optimistic.

Application of adverse and extreme adverse weather: modelling in transmission and distribution system reliability evaluation

This paper presents a new approach for the evaluation of substation and switching station reliability performance in terms of outage frequencies and durations. All realistic component failure modes are included in the reliability predictions. The computer program described in the paper is fairly general. It performs failure modes and effects analysis and provides a concise and orderly description of the various combination of occurrences within the system that could result in an interruption. The application of the program is illustrated by considering two practical system examples. The concepts described are quite general and can be easily extended to the reliability evaluation of other power systems configurations.

A Computerized Approach to Substation and Switching Station Reliability Evaluation

Comparatively, distribution systems have received least consideration in the reliability evaluation of power systems although paradoxically they have the greatest average effect on loss of supply to the consumers. This paper discusses the inherent features of typical distribution systems and describes and evaluates models that more truly reflect the operational behaviour of such systems and their effect on the consumers. The analysis of a typical system is included which illustrates the additional and more meaningful results that can be achieved from the use of these improved system models.

Modelling and Evaluating the Reliability of Distribution Systems

A new method for reliability analysis of power systems is presented in this paper. This method is based on the artificial neural networks (ANNs), which as shown, need short training times. The objective of this paper is presentation of a new method which can solve difficulties of the previous reliability analysis methods, such as low accuracy, complex modelling and large computations. The proposed method is applied for reliability evaluation of generating units and the transmission system. Obtained results from this method for the IEEE reliability test system are mentioned, which confirm the validity of the developed approach. Other advantages of the proposed method for reliability evaluation are also explained.

Evaluation of power systems reliability by an artificial neural network

Power system reliability evaluation

This paper presents a further step in the development of accurate and consistent techniques for the reliability evaluation of transmission and distribution systems. A theoretically accurate Markov approach6is limited in application because of computer storage requirements and the rounding errors which occur in the solution of relatively large systems. This paper extends the modified approximate technique presented in reference (P) to permit evaluation of the contribution to the system reliability indices of different modes of component outage. The equations developed give results which compare very closely those predicted by the Markov approach. A three state weather model is developed to illustrate the effect of severe adverse weather periods on the system reliability performance. The load point failure modes considered are those which arise due to component permanent, temporary, maintenance and overload outages.

Reliability assessment of transmission and distribution schemes

This paper is primarily concerned with the formulation of a group of simple equations which can be used to provide numerical estimates of the rates and durations of system load point failures. The reliability indices obtained by an existing approximate technique2and by the equations developed in this paper are compared with those obtained by a Markov approach using a two state weather model. An equivalent component formation method suggested in the literature5is investigated. The paper shows that this method gives results which are no better than those obtained by the approximate technique2. The modified equations presented in this paper provide reliability indices which compare very closely with those calculated by the Markov approach. The concepts developed are extended to more complex configurations in which loadpoint reliability parameters are obtained by the technique of failure modes and effects analysis and therefore eliminate the necessity of forming equivalent components.

M.S. Grover

Papers

A Computerized Approach to Substation and Switching Station Reliability Evaluation

Reliability assessment of transmission and distribution schemes

Quantitative evaluation of permanent outages in distribution systems