Comparison of alternative insulating fluids

In times when personal safety and the security of electrical power supply become more and more important, the usage of alternative insulation fluids is demanded in large power transformers too. The minimizing of fire loads is another significant reason for new transformers. Several companies offer such alternative insulation liquids and they are already used in distribution transformers. On the other hand there is only few experience with those fluids in large power transformers. Alternative insulation liquids should be compared with mineral oil at equal conditions and voltage levels of several hundred kV AC. Comparison methods and test situations must be found. In this paper it will be shown how the new insulation liquids can be compared with conventional mineral oil and among each other.