Research on Over-temperature Online Rapid Early Warning Methods of Oil-immersed Transformer under the Condition of Three-Phase Unbalance

Abstract

The number of oil-immersed transformers in the distribution network is huge, and the real-time electrical quantity information of a single device is little in number and longer in period in comparison with the main network device. Owing to the randomness of the load, the transformer has long been dynamic three-phase unbalance. The short-term emergency load formed by the rapid rise of residents’ load in summer and winter causes the hotspot temperature of the single-phase winding to rise, the insulation quickly ages, the operating life suffer serious losses, and even cause the transformers in the area to be burned out in large areas. On the basis of the existing data resources, the feasible judgment methods is made from the overall interests, which can avoid damage of the equipment and inform the operating personnel of the residual margin simultaneously. This paper fully proposes the over-temperature online early warning method of oil-immersed transformers under three-phase unbalance, analyzes the compatibility of various commonly used three-phase unbalance algorithms and the hotspot temperature of winding, establishes the logic model of transformer over-line and abnormal warning, and assesses the life loss during the extreme operation of the equipment for reliability. The results of the calculation examples show that the research on the over-temperature online early warning method of oil-immersed transformer under the condition of three-phase unbalance has the capacity to prevent extensive burning of equipment and predict the extreme residue of the transformer.