Electrical generation and distribution equipment employs both liquid and solid materials in its construction. Unfortunately, when such equipment was brought into service many decades ago, little thought was paid to its environmental impact. SuperGen is a major government and industry funded project which tackles the issue of how we can generate and distribute electrical power in a responsible, sustainable and environmentally friendly manner. For our part at Southampton, we are looking at new materials to replace those currently used in such plant, which are less detrimental to the environment both in service and at the point of disposal. The project has two facets, dealing with liquids and solids.
The first part of the project deals with liquid insulation systems. Liquids are used both as an insulator and a coolant in many items of high voltage plant including cables, transformers and switchgear. However, the current oil employed in almost all of these applications is mineral oil which is toxic to the environment and comes from a non-renewable source (crude oil). To date, a biodegradable synthetic oil (dodecylbenzene) and a range of vegetable oils have been investigated as to thier suitability to replace mineral oil in existing and new plant. They have been thermally aged under different atmospheres (ranging from air to nitrogen) to simulate equipment conditions, and their ageing behaviour has been characterised by a variety of optical and electrical techniques. The various available oils have been sucessfully ranked in terms of thier ability to withstand ageing and suitable biodegradable oils for use in existing plant have been recommended. Current work concerns optimising and improving, through the use of additives and blending, thier ageing resistance.
The second part of the project deals with solid insulation systems. Currently, the majority of solid (extruded) power cables employ cross-linked polyethylene (XLPE) which has excellent thermal, mechanical and electrical properties but is not easily recycled and hence its use poses serious disposal problems. To replace XLPE, both ethylene and propylene based alternatives have been proposed which have the advantage of being recyclable after use. So far, the thermal, mechanical and electrical properties of a range of different systems have been investigated and compared to XLPE in order to assess thier suitability for future cable systems. Current work is focused on optimising the mechanical, thermal and electrical properties through suitable choice of material and processing conditions.