TRÄNGSLET IN ÖSTERDALÄLVEN, SWEDEN — The project included transportation plus on-site installation and final assembly in this challenging location.
 

The 120-meter-tall hydropower dam belonging to Fortum, one of the country's largest hydropower producers, is one of the country’s largest, with a normal annual electricity generation of 651 gigawatt-hours. The dam’s electrical equipment is installed underground, via a narrow and steep tunnel, which made the design, delivery and installation of the new transformer challenging.

“It is difficult in terms of transport to get it here, and then adjustments are required to get it underground,” said Mikael Andersson, project manager at Fortum Hydro.

After the original transformer, which had been in operation for over 50 years, had begun to show signs of wear, a decision was made to replace it with a new model. The company ordered a 140 megavolt-ampere and 155/16 kilovolt power transformer, designed as a copy of the original unit. This would enable the installation of the new unit without additional costly electrical, mechanical or structural modifications. Thanks to modern technology requiring less space, the new transformer proved to be smaller in size and is also equipped with digital devices to monitor and analyse the health of the transformer, enhancing reliability and performance.

“There were many risks to take into account, but everything went well.” said Mikael Andersson. “The collaboration worked well. As always in projects, you try to prepare for everything, but things change along the way and therefore the relationship with the client is important. We always try to state that projects are done together towards a common goal.”

After the successful installation and commission of the transformer, operation was handed over to Fortum's operations centre, where it is being remotely monitored and controlled 370 kilometres away in Stockholm.

Source: Hittachi ABB Power Grids