PROJECT: Hydropower transformers | Switzerland
ESTER TYPE: Shell MIDEL 7131 synthetic ester
PURPOSE: Improve fire safety and reduce construction costs
[ OVERVIEW ]
Kraftwerke Oberhasli AG (KWO) is one of the leading hydropower companies in Switzerland. KWO has nine power plants, with 26 turbines and a total capacity of 1,125MW. These assets are spread over eight reservoirs on the Grimsel and Sustenpass areas. In total these plants produce around 7% of the electricity coming from Swiss hydroelectric power plants.
For a specific project KWO needed four 50MVA converter transformers along with a number of auxiliary distribution transformers for an underground installation. In the past these transformers had always been filled with mineral oil, which necessitated the installation of a
complicated fire suppression system.
[ SITUATION ]
A meeting including personnel from KWO, the Utility BKW and the Swiss Institute for the Promotion of Safety and Security (SWISSI) was held to discuss fire safety requirements for the mineral oil converter transformers.
Shell MIDEL 7131 was discussed and the Shell MIDEL technical team met with the interested parties to discuss the benefits of using Shell MIDEL 7131 in place of mineral oil for the transformers. The fire safety credentials of Shell MIDEL impressed all those present so much that they decided to evaluate in depth whether the fire suppression could be removed if Shell MIDEL 7131 was used in place of mineral oil.
The transformers for this project were already on order, so there was a need to change the fluid from mineral oil to Shell MIDEL 7131. The Shell MIDEL team worked in collaboration with KWO and the transformer manufacturer ABB to ensure that Shell MIDEL 7131 was suitable for this particular application. In the meantime a comprehensive risk assessment was carried out by SWISSI, to demonstrate that Shell MIDEL 7131 was of equal safety to the mineral oil and a fire suppression system combination.
[ RESULT ]
The conclusion of this study was that Shell MIDEL 7131 was a viable, and in some cases superior, alternative to using mineral oil with fire suppression. Following the successful outcome of the interaction with ABB and the SWISSI report, KWO received and installed the Shell MIDEL 7131 filled transformers, without any fire extinguishing system. This allowed them to save substantial costs in terms of capital installation, but also removed the ongoing expense of maintenance on the extinguishing system.
Based on this project a joint paper was written by Shell MIDEL and KWO technical personnel and was presented at the Cigre 2012 Paris session. This collaborative approach is a hallmark of the Shell MIDEL team’s commitment to sharing expertise with their customers.