Generator replacement in the Rupperswil-Auenstein HPP, Switzerland

The Rupperswil-Auenstein hydro power plant is located on the Aare River in the north-east of Switzerland. Construction of the HPP Rupperswil-Auenstein began in 1942 and was completed in 1945, resulting in an installed capacity of 45 MW. The run-of-river plant is equipped with two Kaplan units rated at 21.7 MW each plus an environmental turbine rated at 1.5 MW.

In the original power plant setup, one generating unit produced energy for the public 50 Hz multi-phase electricity grid, whereas the second generating unit produced power exclusively for the 16.7 Hz single-phase grid of the Swiss Federal Railways (SBB), the national railway company of Switzerland. The SBB decided to replace the 50 Hz generator by a 16.7 Hz single-phase machine for their own use. Consequently, both main units will be delivering 16.7 Hz power for the railway grid.

As Owner's Engineer (OE), AFRY was responsible for leading, managing and supervising the refurbishment works carried out by several different contractors.

The replacement of a three-phase generator with a single-phase unit implies a number of modifications in the power station. The project consequently included:

• adaptations to the civil structures
• cooling water system
• power evacuation and transformers
• auxiliary power supply system
• take-off structures and
• control and protection systems.

AFRY's engineering services

AFRY was hired to provide OE services for all project phases, from feasibility study to commissioning:

• Feasibility study / study of alternatives
• Basic design and detail design
• Preparation of tender documents for all replacement and refurbishment works as well as leading the tendering process, until contract award
• OE services during project execution:
  – Design review
  – Project management
  – Quality control
  – Site supervision
  – Schedule analysis and optimization
  – Commissioning.