Thermal behaviour of a transformer mineral oil-tank surface under incipient turn-to-turn short-circuit fault

A slight turn-to-turn short-circuit fault in the incipient stage does not trigger fuse protection, and the regular transmission and transformation functions of the transformer within the power grid are not affected very much by the incipient turn-to-turn short-circuit fault. Therefore, the incipient turn-to-turn short-circuit faults are often undetected, resulting in massive accidents. Incipient turn-to-turn short-circuit faults lead to localized overheating in the transformer, which changes the transformer's oil-tank surface temperature (OTST). A thermal simulation model (TSM) is presented. Based on the TSM, OTST data with different load rates and fault parameters are collected. The steady-state and transient characteristics of OTST are analysed by extracting the OTST feature vector and the temperature difference of specific regions. The results show that the growth of the heat production value of faulty coils causes a rise in the OTST; higher faulty coils' locations lead to wider OTST differences; the temperature difference's area S can follow the incipient short-circuit fault in the first 20 min after it occurs, which is faster than the top oil temperature. This study gives insight into the thermal behaviour of OTST, assisting in fault detection and location at the incipient fault stage. This paper proposed a thermal simulation model of the oil-immersed transformer and analysed the oil-tank surface's steady-state and transient thermal behaviours under incipient turn-to-turn short-circuit faults. The oil-tank surface temperature (OTST) feature vector b is proposed to show the overall thermal behaviour of the oil-tank surface, and the temperature difference of the specific regions TF(S, hF) is analysed to show the local thermal behaviour. The proposed dynamic analysis and steady-state methods of analysing the thermal behaviour of OTST can help guide online monitoring and fault detection of transformers. image