The breakdown voltage of mineral oil is an important parameter that indicates its insulating properties, directly relating to the dielectric strength of transformer oils. Generally, mineral oils used in transformers should have a breakdown voltage of at least 30 kV or higher to ensure proper insulation and prevent electrical breakdown. The actual breakdown voltage can vary depending on factors such as oil contamination, temperature, and additives. Regular testing with appropriate devices, such as the Globecore oil testing equipment, is essential to monitor the dielectric strength and ensure optimal performance and safety of transformers.