Advanced lifetime assessment and stress control of steam turbines

摘要

At high shares of intermittent, renewable energy power, the demand for more flexible operation of power plants will increase beyond the flexibility they were originally designed for. Such an excessive use results in poor efficiency, increased emissions, high operational costs and raised lifetime consumption at a decreased capacity factor due to longer standstills and frequent low load operation. In order to keep the power plant in the market, the operation and maintenance cost of flexibility must be reduced despite the demand for faster load changes and start-up and shutdown procedures. To enable the planning of the lifetime use by increasing flexibility, the remaining lifetime of the steam turbine is required. The lifetime assessment (LTA) is a standardized process for proprietary impulse and reaction turbines, which takes the huge variability of long-term field operation data into account. This well proven, automated process was recently extended to also apply to turbines of other manufacturers, having different materials and designs. Presented are results of the validation study combining long-term operation data with finite element calculations, subjected to a parametrical variation of materials and designs. As shown, the resulting precision in the lifetime assessment is sufficient to set up an economically optimized lifetime management based on an up to date stress controller in place, allowing the power plant to actively taking part on the day ahead and inter-day flexibility market. One key component of the up to date stress controller is a new, validated stress control probe, having a higher precision and a clearly improved dynamic.