Abstract: In order to achieve effective online monitoring of the state of metering voltage transformers, the characteristics of group transformer voltage ratio difference data are theoretically analyzed. An anomaly detection method for voltage transformers is proposed based on the 3σ criterion, and an online monitoring system for voltage transformers is developed, which can effectively and economically realize the identification of transformer anomalies. The field data verification demonstrated that the sample proportion of ratio difference data within the 3σ interval is 99.52%, confirming the gaussian distribution characteristics. The anomaly probability for out-of-tolerance transformers fluctuates between 40% and 80%, significantly higher than that of normal transformers.

Key words: voltage transformer, anomaly detection, 3-sigma rule, gaussian distribution