La Grande-3 Hydro Power Plant

Hydro Quebec
Baie-James, Quebec
2019–2021

In close collaboration with Hydro-Québec’s engineering team, SIMCO (previously Cosigma) played a key role in the preliminary project for rehabilitating the turbine-generator units (TGUs) at the La Grande-3 (LG-3) power plant.Located on the Grande River in the Baie-James region, the LG-3 plant is an engineering landmark, built during the first phase of the James Bay Project between 1976 and 1983 and commissioned between 1982 and 1984. Equipped with twelve turbine-generator units, it delivers an impressive 2,417 MW of power, contributing significantly to Québec’s energy supply.

Clear, Precise Definition of Structural Requirements for Subsequent Project Phase

Hydro-Québec planned to rehabilitate or modify the TGUs to increase hydroelectric production capacity. This power increase involved replacing TGUs and transformers installed on the plant’s roof, as well as modifying various electrical equipment such as bus ducts, circuit breakers, and the control system. The mandate was to provide advanced technical support for structural analyses, ensuring optimization of existing assets and a clear, precise definition of structural requirements for subsequent project phases.

• Assessment of the current capacity of the steel superstructure, including the roof, mezzanines, and crane runway beams.
• Evaluation of loads, including dead loads, live loads, mobile loads on the roof, crane loads, and environmental loads.
• Analysis of current stresses on the steel superstructure and capacity for increased loading.
• Assessment of structural impacts based on several load increase scenarios provided by Hydro-Québec, and identification of required work to support them.
• Finite element modeling of the superstructure with variable inertia elements and detailed modeling of the runway beam.
• Preparation of a bill of quantities for structural reinforcement work required for each rehabilitation scenario.
• Evaluation of the structural capacity of the reinforced concrete generator floor for rehabilitation work (rewinding of units).
• Enlargement of existing floor openings to allow the installation of new bus ducts.
• Extension of the plant on the right bank to create a second service area with a new steel structure.

Image credit: Hydro-Quebec