Validity Analysis of Effective State Quantities of Oil Immersed Transformer

With the demand of condition-based maintenance conducted in power transformers, it is crucial to select effective state quantities so as to evaluate the health status of transformers. This article comprehensively analyzes the validity of various state quantities based on historical data in transformer maintenance. According to approximately 800 abnormal events over ten years of operation and maintenance, most transformer faults are detected by inspection accounting for 71.93%, followed by oil tests and electrical tests. Putting it in detail, different detection methods of state quantities are categorized. By analyzing the validity of effective quantities, the most effective variables are sorted after, including dissolved gas analysis in oil, DC resistance, insulation resistance of iron core clamps, grounding current of iron core clamps, and short-circuit impedance. Besides, some state variables which need power outage can be equivalent to those with no need of power outage. In order to reduce the use of power outage detection, a process for obtaining the optimized quantities without power outage is proposed. The research results have reference significance for the reliability operation and maintenance of power transformers.