Validation of condition of natural esters

摘要

Demands on current electrical insulating systems have increasing trend toward tolerance to environmental safe conditions. This trend of course subsequently requires finding a new way in the field of application of materials compatible with the surrounding environment, e.g. easy biodegradable. This applies particularly for electrical insulating liquids used in distribution transformers since their deployment is in large numbers - 50,000 pieces only in the Czech Republic - are often in areas with increased demands on the environment - urban areas, natural preserves or close water sources. These electrical insulating fluid therefore has excellent electrical insulation properties in addition having another important feature - are biodegradable. Therefore, when eventual unwanted leakage was occurring, they are absorbed by soil bacteria and it is not necessary to perform sanitization of the soil. This is advantage to the petroleum products. Fluids, which are in this area currently in center of legitimate interest, are natural esters. Their introduction to full application will however require the implementation of a number of following studies so that these substances can fully cope with properties of currently used mineral oils. Mineral oils have excellent electrical properties, but they are intolerant to the environment. One of the essential aspects of the verification of the long-term durability of natural esters, namely the rapeseed oil to long term thermal exposure. This verification is necessary for electrical insulation fluids especially because of their operation in transformers, where they become liquid component of the insulating system. The liquid in transformer are subjected to permanent thermal stresses during operating mode. The aim of this study was therefore to investigate the life time of natural esters and compared it with selected synthetic and mineral oil.