Grey Correlation Risk Evaluation Method Of Converter Transformer

Converter transformer is the key equipment in ultra hvdc transmission system, but also the core equipment connecting the converter station and the inverter station in AC and DC transmission systems. Therefore, the risk evaluation of converter transformer is very significant to the success for the condition-based maintenance, which is performed timely and accurately. Because it can reduce the maintenance cost, shorten the power-off maintenance time, increasing the equipment electricity utilization and improve the reliability of the transmission system.Fistly, the converter transformer is analysed based on FMEA (failure mode and effect analysis); secondly, the risk assessment model of the converter transformer is constructed, and the determination method of risk probability assessment index and risk consequence assessment index are proposed. Mainly includes the following:①In comprehensive consideration of the function and the parts of converter transformer, the FMEA table of the converter transformer is completed applying failure mode and effect analysis method. And the main fault modes of converter transformer are identified.②The risk assessment index system including the risk probability, risk severity, risk detection and risk maintenance costs is established. The assessment method of the risk probability is proposed based on Weibull distribution and fuzzy membership function. For the risk severity, the risk detection and risk maintenance costs, the quantitative standard rate method is established.③Grey correlation risk evaluation method of converter transformer is proposed. On the basis of the risk assessment matrix of the fault modes, Fistly, the dynamic weights of the risk assessment indexs are calculated applying entropy method; secondly, the risk indexs of the fault modes are calculated using grey correlation theory. This avoids the deficiency that the same priority index (RPN) can't give the accurate evaluation results in FMEA method.④The risk evaluation of the converter transformers in±500 kV Tian Guang converter station,±500 kV An Shun converter station and±500 kV Qing Yan converter station are carried out. The evaluation results show that the evaluation method can make correct assessmen according to the relevant test data of the converter transformers and has certain practical value.