Vaud Jura: replacement of transformers

Les Clées power station on the Orbe river in Ballaigues was built in 1955. As part of the refurbishment of its high-voltage installations, Romande Energie chose to replace the 40 kV substation and 12 MVA 13/40 kV transformers on the three production machines.

The task entrusted to HYDRO Exploitation proved to be a delicate one. The raw materials market is currently tight and features long materials delivery times and volatile prices. It was therefore decided to opt for a grouped delivery of the three units.

A challenge in terms of logistics and safety

However, given the weight of the equipment (21 tonnes per transformer), the logistics, particularly in respect of storage, were a relatively complex challenge. The premises had to be modified, and the proximity of springs and the Orbe river called for a number of environmental and safety studies.

In the end, this project incorporated the following aspects:

• Disposal and recycling/recovery of the old transformers
• Refurbishment and upgrading of retention pits
• Adaptation of the transformer refrigeration
• Installation of an aerosol fire detection and extinguishing system
• Replacement of the cover plates for the transformer rooms
• Modification of access to the premises to comply with fire standards
• Adaptation of control systems, testing and commissioning

The outcome of this intervention was positive: the installations were commissioned on time and without any major problems thanks to excellent coordination both internally and with all the contractors involved in the project.