Thermal Fault Model Validated in Mineral Oil for Dissolved Gas Analysis

This paper presents a thermal fault model that reliably reproduces the gases generated by hot spots in transformer insulation systems. The model, designed without paper insulation, is based on a configuration of four stacked transformer core plates that enable the controlled simulation of fault scenarios over a temperature range from 200 to 800 °C through direct thermocouple measurements. Thus, core faults such as inter-lamination short circuits caused by circulating currents, as well as mechanical issues like a loose bushing bolt, can be emulated. Experimental validation was carried out using mineral oil, a liquid with well-established behavior and extensive field experience, ensuring that the model generates fault conditions consistent with real operational environments. A case study with a soybean-based natural ester further demonstrates the model’s adaptability to alternative insulating liquids. The proposed model offers a robust, scalable platform for advancing transformer fault diagnosis and supports the development of improved diagnostic techniques in the field of Dissolved Gas Analysis (DGA).