Thermal–Fluid Characteristics of Transformer Winding Inter-Turn Short Circuits and Their Application to Fault Localization

Abstract

Internal temperature monitoring is an important approach for assessing the operating condition of power transformers. Temperature-rise characteristics not only indicate faults such as inter-turn short circuits but also indirectly reflect the diffusion and transport behaviors of characteristic dissolved gases within the transformer oil. To enable early warning and localization of inter-turn short circuits in transformer windings, this paper proposes a method based on monitoring the oil temperatures at the inlets and outlets of the transformer cooling system. First, a simulation model of a 110 kV transformer was developed, and coupled thermal–fluid simulations were performed to analyze the oil-temperature distributions in the transformer body and cooling system under normal operating conditions and representative inter-turn short-circuit conditions. Next, a simulation-based fault-localization strategy is proposed to investigate whether the spatial temperature distribution of cooling-system oil can be used to infer the vertical position; faulty phase; and, for certain fault locations, the winding side of an inter-turn fault. Finally, the temperature sensor locations were selected, and the performance of the localization strategy was evaluated. The simulation results demonstrate the feasibility of using the temperature distribution of cooling-system oil for the detection and localization of inter-turn short-circuit faults.