Improving the reliability of decisions taken in the organization of maintenance and repair of electric power systems is one of the most important and difficult problems. It is important because erroneous solutions lead, first of all, to an increase in operating costs. The difficulty in solving this problem is associated with the lack of appropriate methods to reduce the risk of erroneous decisions. The article presents one of the aspects of this problem, i.e. improving the reliability of the decision on the nature of the relationship of technical and economic indicators of electric power systems. Traditionally, increase of reliability of the decision is reached by reduction of a Type I error. Usually it is accepted to be equal to 5%, occasionally – to 1%, and at researches – even to 0.5 %. The corresponding critical values of correlation coefficients are given in mathematics reference books. This method implicitly assumes that the consequences of a Type I error significantly exceed the consequences of Type II errors, and the distribution of correlation coefficients corresponds to the normal law. Therefore, the risk of an erroneous decision concerning the absence of a significant statistical relation is not controlled. But even if there is a wish to estimate the Type II error, it is almost impossible to fulfill it, because there are no critical values for correlation coefficients of dependent samples. No less relevant is the problem of deciding on the statistical relationship between technical and economic indicators in conditions of equality of consequences of erroneous decisions, i.e. it is necessary to take into account both a Type I error and a Type II error. To overcome the mentioned difficulties a new method for estimating the critical values of correlation coefficients has been developed. The novelty consists in the application of fiducial approach; the calculation of critical values are fulfilled with the aid of computer technologies of simulation of possible realizations of the correlation coefficients for the two assumptions, viz. technical and economic indicators of the independent and dependent; simulation is fulfilled with the method of solving the “inverse problem”, which enables the possible implementation of the correlation coefficients for the really dependent and independent samples of random variables at a given sample size; the developed algorithms and programs for calculation made it possible to obtain the critical values of correlation coefficients for independent and dependent samples; in conditions of the sameness of the consequences of erroneous decisions it is proposed to make a decision not based on critical value but based on the boundary values of the correlation coefficients that correspond to the minimum total risk of erroneous decisions; the exemplification of the recommendations application was made on example of technical and economic parameters of boilers of power units of 300 MWt. The significant impact of the availability of interrelated technical and economic indicators on the result of the ranking of boiler plants by the reliability and efficiency of their work is demonstrated.
It becomes more and more obvious that focusing solely on economic efficiency is not a good strategy for business development. Moreover, a quantitative assessment of the integral operation indicators, including complex indicators of efficiency, environmental performance and safety, can help to protect a business against possible bankruptcy [1]. In the electric power industry, this is reflected in the modified concept of operational efficiency (OE). OE is not only the usual economic efficiency, but also operational reliability and safety. There is a good reason for such modification of the concept. In electric power systems (EPS), the actual service life of about 60% of the main equipment, devices and installations exceeds the rated value. We shall refer to such equipment as “overage facilities” (OF). The failure of such OF is the main cause of unacceptable system emergencies. During the rated service life of EPS, only a quantitative assessment of operational economic efficiency is performed. Operational reliability and safety (for example, the average monthly values) are not calculated, since they are guaranteed by the manufacturer. However, after the warranty period is over, operators still do not evaluate complex indicators of operational reliability and safety, since there is no methodology for their assessment. Moreover, it is necessary to be able to calculate the integral OE indicators which reflect the actual values of economic efficiency, operational reliability and safety. It can significantly reduce the risk of mistakes when choosing the methods for organizing operation, maintenance and repair. Then, decisions will be made based on comparing these integral indicators. The random nature of changes in technical and economic indicators (TEI) is determined by the random nature of changes in the integral OE indicators. The article presents new methods and algorithms for determining the feasibility of classifying the integral OE indicators of OF.
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