Did you know that power transformers are one of the most expensive and strategic components of an electric power transmission and distribution (T&D) system? A possible failure may result in a long-term power outage, therefore, it is essential that power transformers work efficiently for many years.
Today, tens of thousands of power transformers are in operation across the globe. The normal life
expectancy of a power transformer is 30-40 years. Many of these transformers are reaching the end of their lives, which raises the question of their recycling potential. Did you know that around 95% of a power transformer’s materials could potentially be recycled? Some materials of high economic value such as copper, can be recycled and resold as secondary raw materials.
European Commission’s Circular Economy Plan
A circular economy aims to change habits from a so-called linear economy, which has a “take, make, dispose” model of production to a circular one, where wastes become a new resource. In early 2020, the European Commission adopted a Circular Economy plan with the ambitious goal to give back to the planet more than it takes. The initial focus of the eco-design regulation on transformers was on energy efficiency. However, the impact of materials is not negligible, mainly due to the high quantities of steel and copper used in the transformers. Also, at the end of life of the transformer, recycling of all these metallic materials should be ensured. This is the reason why the European Commission’s Circular Economy action plan will include some new requirements on material efficiency in the next revision of the eco-design regulation for transformers, expected in 2023.
Applying the Concept to Grid’s Power Transformers
GE’s Elodie Laruelle and Christophe Perrier, Materials Engineer from Grid Solutions’ ARC Materials Laboratory (led by Yannick Kieffel) and François Devaux, responsible of Grid Solutions Technology, Innovation and Competence Development Centre, shared their research, published in the REE magazine, as to how they have applied the concept of a circular economy to Grid’s power transformers.
1. Material efficiency
Material efficiency relates to the efficient use of materials over a product’s lifetime, including its fabrication, distribution, use and disposal. The benefits of recycling and reusing the materials used in power transformers was evaluated. For example, evaluating the possibility to replace conventional oils by renewable or re-refined oils is an important improvement in the circularity design of power transformers. One example that supports the concept of material efficiency is around biodegradable vegetable oil. At the end of last year, we signed an agreement with major Brazilian utility company Engie Brasil to supply power transformers that use biodegradable vegetable oil (natural ester) as an insulating medium and refrigerant instead of mineral oil. This is what we call “green transformers”.
2. Lifetime extension through oil monitoring
Although a transformer is a very reliable device, like our body, it can also get sick and needs the right diagnosis and medicine to get well quickly. Indeed, most, if not all, organic materials used within the transformer are subject to aging processes which lead to the gradual degradation of their physical, chemical and electrical properties. That’s the reason to apply mitigation techniques at the right time (maintenance, upgrade, oil treatment…), we are monitoring the “health” of the transformer based on its oil, just like we use blood tests on humans. So while the end of life failure is inevitable, oil monitoring is an efficient way to improve the lifetime extension of power transformer and thus their circularity. GE’s IEEE article published in 2016, gives an overview of efficient ageing markers.
3. End of life & recycling
At the end of its life, a transformer must be drained, prepared for transport off-site and then dismantled. During the dismantling, many materials are collected and sent for recycling. Waste management processes vary according to where the dismantling is taking place. However, the recommended recycling actions are generally the same for the four main materials constituting the transformer: steel, copper, cellulose and insulating liquid.
With high energy efficiency level, high recyclability rate, introduction of new innovative materials that are renewable, as well as a lifetime that is mastered and optimized due to regular oil monitoring, power transformers can be seen as a good example of a product in line with circular economy principles.