Voltage regulated distribution transformers to become a key component of smart grids

High-efficiency distribution transformers with on-load tap changers can help distribution network operators and owners of commercial distribution rings to secure supply in light of increasing voltage fluctuations from renewable energy generation.

The growing popularity of wind and solar power is fundamentally changing the way distribution networks operate. Many traditional energy consumers - from businesses to homeowners - have now also become generators, feeding various amounts of energy into the grid, depending on the weather and their own consumption. This two-way flow of electricity is making it increasingly challenging for distribution network operators (DNOs) to maintain the optimal bandwidth. If the voltage drops too low, supply is effectively cut off. Overvoltage, however, could potentially damage vital electrical equipment.


"Traditionally, energy generation would be stepped up by designated power plants according to predictable peaks in consumption, such as during the ad break of a popular television programme. However, the way that renewable energy is generated by many different parties today means that it can be difficult for DNOs to control when and how much energy is fed into the grid. Energy might be contributed at a time when grid voltage is already high, for example, or sometimes not at all. There have always been peaks and troughs in grid voltage but the difference between them is coming greater and more unpredictable," says Erika Wilson, joint managing director of Wilson Power Solutions.

"And so far we have only scratched the surface with renewable energy," she adds. "The UK Conservative government has committed to switching off all coal fire electricity generation capacity by 2020 but we haven't got the required renewable energy generation capacity already in the pipeline. Supply is going to become more and more insecure unless DNOs and private industrial or commercial owners of small distribution rings take steps to upgrade their infrastructure."

Help is on the way

Leeds-based transformer manufacturer Wilson Power Solutions has developed an answer to this growing problem in its Wilson e2+ range of distribution transformers with on-load tap changers. The integration of an advanced on-load tap changer enables the transformers to redress fluctuations in grid voltage at a distribution point, maintaining usable supply while also protecting electrical equipment from hazardous overvoltage.

"Our Wilson e2+ transformers have attracted a lot of interest from customers so far because they see a problem that going to become even more important in years to come. We believe that voltage regulated distribution transformers will be a key component of a safe and reliable smart grid in the future," she says.

Ahead of the curve

Although this technology is nothing new - tap changers are widely used in larger power transformers and also in distribution transformers in countries, such as India, where grid voltage has a history of unreliability - it is unique when combined with the super low-loss core of Wilson Power Solutions' transformers. The company was the first transformer manufacturer in the UK, if not Europe, to produce transformers with an amorphous metal core, offering even greater efficiency than those made from the highest grades of grain-oriented electrical steels. Wilson e2 and e2+ transformers (the plus signifies the on-load tap changer) are so efficient that they already exceed the requirements of the EU Ecodesign Directive for transformers coming into effect in 2021.

"We urge customers to think about the future when selecting their transformers - what grid conditions will be like and the running costs over the transformers' lifetime. The minimum life expectancy for a distribution transformer is 25 years but when we made a freedom of information request to Ofgem - the government regulator for gas and electricity markets in Great Britain - we found that the actual age of distribution transformers in the UK is more like 62 years. When a transformer is going to be operational for that length of time, it makes sense to pay a little bit more upfront for a model that will perform better in terms of resilience and energy efficiency and generate huge savings in the long run," Wilson says.

Despite their higher initial purchase price, Wilson e2 and e2+ transformers begin to generate savings for customers after an average of three years. "Some of our customers are saving in excess of £25,000 per year in running costs. Times that by the average life of a transformer and it's an absolute fortune! Total cost of ownership is so important," she adds.

Wilson discussed the growing need for highly-efficient distribution transformers with on-load tap changers in a recent CWIEME Berlin seminar, entitled ‘Voltage regulated low loss distribution transformers - the answer for improved elasticity?'. Wilson was also be joined on stage by Dr. Manuel Sojer from Maschinenfabrik Reinhausen, the global market leader in on-load tap-changers, which launched a groundbreaking new product at this year's exhibition.

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