THESIS - Retrofilling of step-up transformers for hydropower plants

Background 

In a normal electrical power system, the step-up transformers are vital components of the grid and the chain of power production. Many of our step-up transformers within hydropower are located underground in the mountain. The transformers are filled with mineral oil and requires fire extinguishing systems, which are expensive to purchase and maintain. Questions have been raised if there is a possibility in existing transformers, to change the mineral oil to ester fluids; a so called retrofilling. Fortum has actual cases for transformers located underground with an operating voltage of 145 kV.  

Today, retrofilling is common to perform on transformers connected up to 36 kV operating voltage. But on higher voltage levels a lot of other parameters will influence and no guarantees will be issued. If a transformer is filled up with ester, this may be considered equal to a fire extinguishing system, as ester fluids are expected not to burn. 

Objective 

The Master Thesis project is expected to perform a case study on retro-filling of high voltage transformers (up to 220 kV) with ester fluids and what impact it may have on the transformer in terms of dielectric and thermal properties, BIL-level. Different properties for mineral oil and ester fluids will be investigated, viscosity issues, impact of flash-point etc. Investigation of design of existing transformer. 

The project aims at explaining the general challenges with this action and should be performed for one of our hydropower plants. 

Our offer 

At Fortum we see a Thesis Project as a good way to get to know you during your study time and for you to learn more about Fortum and how our business is working. A Supervisor will be appointed to support and guide you through the Thesis Project and you will also be part of the network of people within the Company and with other Students doing their Thesis by us.  

For a well performed and approved work, we will pay a taxable lumpsum award. 

This Thesis Project is preferably executed at any of our offices in Sweden; Stockholm/Solna, Västerås, Borlänge, Karlstad, Östersund or Arbrå. 

Site visit and field measurements are expected to be included. 

Your Qualifications 

The Master Thesis project is preferably conducted by one or two students, studying at Master programs related to Power Systems, Electrical or Energy Technology. The Project may be executed in Swedish or English.  

We expect you to have a theoretical insight in Energy Economics and interest in the development of the power system.   

Interested? 

To apply, register your CV and a personal letter of maximum one page or a Power Point presentation of maximum two slides, in our Recruitment Tool via “Apply now”, latest by 24th November 2024. Applications will be evaluated continuously and an applicant may be on-boarded before this date. 

The personal letter shall include an approach on how you would like to investigate the idea. Mark your application with the reference number HYG-177. 

If you apply for this together with someone else, each shall submit an application, stating with whom one wants to co-work on this project. 

If you have General questions about Theses or Internship at Fortum, please address those to fortumcareers@fortum.com. 

Please note that we have more Master Thesis Projects open for application at our recruitment site.