Application of mineral oil in HV power transformers

Summary form only given. High-voltage (HV) power transformers are exposed to a large variety of electric stresses during final testing as well as in service. In addition to the dielectric strength requirement, the insulation system must meet further requirements. Thermal and mechanical aspects also have to be taken into consideration when dimensioning the insulation. In consequence, oil ducts of different sizes and volumes are exposed to different types of stresses. The approach taken by the transformer industry to the design of their products for safe operation has been considered.