Condition Assessment of Valve-side Bushing of Converter Transformer Based on Extension Theory

The converter transformer occupies an important position in the power system. As an important part of the converter transformer, the safety of the valve side bushing is also crucial. Based on the extension theory, this study proposes a comprehensive evaluation method of the valve side bushing of the converter transformer combining the analytic hierarchy process and the extension evaluation method. First, according to the operation experience of the converter transformer and related guidelines, determine the typical failure types that can occur in the converter transformer, and construct an effective index set. Second, AHP is used to construct the judgment matrix. By calculating the normalized feature vector with positive components and consistency test, the single-layer weight factors of each evaluation index are accurately obtained, and the contribution degree of each index to the total goal is calculated by using the series principle, that is, the total weight. Then, using the extension analysis method, by calculating the correlation function between the material element to be evaluated and each evaluation level, a quantitative and qualitative analysis is carried out to achieve an accurate assessment of the state of the valve side bushing of the converter transformer. The correctness and effectiveness of this method are verified by examples.