Turbine and generators is one of four research areas in HydroCen. A paradigm shift in design and operation of the power plants is possible by introducing power electronic converters. Reversible pump-turbines will operate smoothly, ramping rates will be faster, efficiency will be higher and the operating range of Francis turbines will be wider when introducing variable speed turbines and generators.

By introducing converter-fed synchronous machines (CFSM), the dynamic capability will be strengthen due to “synthetic inertia” and the converter improves the fault ride through by decupling the generator from the grid frequency. “Variable speed operation is a new degree of freedom” says the R&D director for hydraulic development and risk management at Alstom.

High head hydro turbines are known to operate with high fatigue loads originating from; off-design operating condition, start-stop and speed no-load conditions. Studies have shown the large fatigue load from such operating conditions, but they lack the ability to carry out fatigue lifetime analysis for turbine components. Variable speed operation will change the operating conditions in the turbines and reduce the fatigue loads.

Breakdown of the electrical turn or ground insulation in the hydropower generator stator winding are the significantly most frequent failures and those that produce the greatest extent of damage. This includes e.g. thermal ageing caused by long time operation at high temperature, deterioration caused by frequent load changes and fast transient voltage stress from frequency converters.

Norway has many hydropower plants that operate between large reservoirs, being ideal for pumped storage power plants, and a natural realization of this is retrofitting of pumping capabilities in existing power plants. However, the existing power plants are insufficiently submerged to avoid cavitation in pumping mode. Thus, there is a need for new technology to realize the pump-storage potential in existing plants.

Main objective: Develop new technologies to strengthen the capabilities of the hydropower system and enhancing the operational and system flexibility.

Sub-objectives:

• Develop new technical solutions for variable speed operation for future hydropower plants

• Enable calculation of the fatigue loads on turbines

• New technology for retrofitting reversible pump turbines in existing power plants

• Reliable operation and lifetime for turbines and evaluation criteria for electrical insulation

Tasks:

• T 2.1 Variable speed operation  
• T 2.2 Fatigue loads on turbines
• T 2.3 Pump turbines in existing power plants
• T 2.4 Turbine and generator lifetime