Mineral oils are still the standard in most transformers and tap changers. But there are more sustainable alternatives. Rainer Frotscher, expert for insulating fluids at MR, explains what’s important here.
What are the arguments against mineral oils?
Major disadvantages include their high flammability and risks to soil and water protection. However, fire safety, environmental friendliness, and conservation of limited resources are criteria that are becoming increasingly important. Due to the increased use of renewable energies and the associated decentralization of power generation, the number of smaller, distributed power plants and transformers is increasing. They are often installed in ecologically sensitive areas, such as in watersheds or on the open sea. At the same time, the demand for electricity is growing. High-voltage lines are being routed into cities, meaning that power transformers need to be installed directly in urban environments. It is especially important here to fill the equipment with biodegradable and/or flame-retardant fluids instead of mineral oils.
What sustainable alternatives to mineral insulating oils are available?
In the past few years, a wide range of various alternative insulating fluids has been developed. Biodegradable fluids are particularly relevant to transformers and tap changers.
These can be bio-based hydrocarbons or synthetic and natural ester fluids. However, not all fluids are equally well-suited for use in tap changers.
What factors are important?
Many factors need to be taken into account, such as, for example, the tap-changer technology to be used, the exact operating conditions, and the relevant electrical, mechanical, and thermal requirements. In our test center, we have carried out extensive tests for various applications. And our tap changers with alternative insulating fluids have now been proven in hundreds of uses in the field—including in special applications, such as traction transformers, test-field transformers, transformers for offshore wind parks, and mobile emergency transformers.
Natural esters are ideal as alternative insulating oils and are based on renewable raw materials such as canola.