Open AccessCORRECTION OF TRANSFORMER OIL BREAKDOWN VOLTAGE MAXIMUM PERMISSIBLE VALUES BY THE MINIMUM RISK METHOD
Author(s) -
Оleg Shutenko,
Serhii Ponomarenko
Publication year - 2020
Publication title -
vestnik nacionalʹnogo tehničeskogo universiteta "hpi". ènergetika: nadežnostʹ i ènergoèffektivnostʹ
Language(s) - English
Resource type - Journals
ISSN - 2224-0349
DOI - 10.20998/2224-0349.2020.01.16
Subject(s) - weibull distribution , transformer , mathematics , voltage , distribution transformer , breakdown voltage , transformer oil , statistics , electrical engineering , engineering
The method of correction of maximum permissible values of breakdown voltage of transformer oils in order to minimize possible economic damage in case of making erroneous decisions during diagnostics of the condition of transformer oils according to the results of periodic tests is proposed. An algorithm for statistical processing of the periodic test results is described, the use of which allows forming arrays with homogeneous values of the indicators under a priori limited measuring information. Analysis of distribution laws of breakdown voltage values for the transformer oils suitable and unsuitable for operation according to the values of this indicator is done. According to the results of the analysis, it was found that the breakdown voltage values of oils with different states have Weibull distribution. It was determined that the values of mathematical expectations of breakdown voltage of serviceable oils with the ageing of transformer oils shifts to the area of low values. It means that the breakdown voltage maximum permissible values of oils for the given distributions should be different. It is confirmed by the previously known fact that for unimodal distributions, the maximum permissible values of indicators that provide a minimum of risk are in an interval bounded by the mathematical expectation of the indicator distributions with different states. A decisive rule is formulated and an average risk function is compiled to adjust the maximum permissible breakdown voltage values of transformer oils. Based on the minimisation of the average risk function by Newton's method, the maximum permissible values of the breakdown voltage of oils have been determined. The made comparative analysis has shown that the correction of maximum permissible values of breakdown voltage of oils allows decreasing the risk values by 1.52÷19.13 times in comparison with risks, which provide the use of maximum permissible values, regulated in standards. It was found that the maximum permissible values of the breakdown voltage of oils, providing a minimum value of average risk, are not constant. They vary depending on the values of faulty decision prices and the probabilities of occurrence of different defective and defect-free oil states of transformers.