Customer: Göteborg Energi Nat ABGöteborg Energi Nat AB
Location: Göteborg, Sweden

Application: GSU Power Transformers
Highest Voltage: 135kV
Rating: 40MVA


There has been a long history of use of MIDEL filled power transformers in Sweden, with Vattenfall having installed their first 151kV unit in 2002. Following the success of Vattenfall’s experience other utilities started to take up the MIDEL option, in order to greatly improve fire safety and reduce environmental impact.

Among the utilities switching to MIDEL to improve fire safety, were Göteborg Energi who are responsible for the larger Göteborg region of Sweden. This region uses over 50 power transformers (40MVA and larger) and more than 2000 distribution transformers of 630kVA and larger rating.

As part of their operation Göteborg Energi has a number of rock stations where the main transformers are housed underground. In each rock station there are typically three transformers, with at least two online at any one time. Fire safety is critical for this type of installation; hence they had an interest in using MIDEL 7131.

From the outset of the project the M&I team were involved to provide advice on the use of MIDEL ester-based fluid. Both the MIDEL technical and commercial teams provided support to the transformer OEM, Koncar, during the development phase. This included providing support on topics such as correct handling of the fluid, as well as electrical and thermal characteristics. Members of the team visited Koncar on a number of occasions to ensure that the right information was made available in a timely manner.

This close cooperation between the end user, transformer manufacturer and the MIDEL team is typical of our holistic approach that helps make MIDEL the world’s leading brand of ester transformer fluids.

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