Fuzzy logic and evidence reasoning-based transformer insulation stress calculation and evaluation method

Abstract

The invention discloses a fuzzy logic and evidence reasoning-based transformer insulation stress calculation and evaluation method. The method comprises the following steps of firstly normalizing field data, namely, converting input data for describing a normal value, a limit value and the like of a transformer into dimensionless variables of a [0,1] region; secondly fuzzifying the input data, namely, mapping the input data to a fuzzy membership function, wherein a trapezoidal membership function, a generalized bell-like membership function or a Gaussian membership function can be used; thirdly building a transformer stress evaluation tree model, namely, establishing nodes from the input data of the transformer to an insulation stress of the transformer, and a connection mode of the nodes, and correlating the nodes of upper and lower layers by using a fuzzy correlation matrix; fourthly determining a weight value between the nodes, namely, obtaining a synthesized weight value by using a subjective weight value of an analytic hierarchy process and an objective weight value of eigenvector analysis; and finally obtaining the insulation stress of the transformer, namely, determining a total stress level of the transformer by using a reasoning mechanism and an evidence synthesis rule. The method has the advantages in accuracy, flexibility and capability of processing measurement uncertainty.

Description

【Technical field】 [0001] The invention relates to the technical field of power systems, in particular to a method for calculating and evaluating transformer insulation stress based on fuzzy logic and evidence reasoning. 【Background technique】 [0002] One of the most critical devices in a power system is the transformer, the availability and reliability of which must not be compromised. Load optimization of existing transformers is a priority for many utilities, necessitating that the equipment operate within the limits of the stress levels for which it was designed. As transformer MVA and kV ratings continue to increase, inevitably leading to premature failure of legacy codes, stress levels on transformers need to be assessed and managed as planned. Transformers typically age over time, so their ability to withstand operational stress gradually decreases. [0003] Transformer cores, bushings and windings are generally considered to have an infinite life due to the very sl...

AI Technical Summary

Problems solved by technology

Events such as short circuits, overvoltages and moisture ingress can overload transformers and accelerate the degradation of their insulation

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