Performing a hydropower plant assessment can be compared with human health examination. Utilities need to get, regularly over the HPPs’ life time, information about the condition of main systems and key components to take management decision about necessary/profitable investments in order to ensure the plant safety and long-term value and to improve the operating results (increase revenues, reduce O&M costs, …). The plant assessment should give an overview of the current condition of all systems and clearly identify the weak points. A proposal of further specific inspections for a closer problem investigation is also an outcome in order to define the necessary future measures, as well as a necessary repair/overhaul or modernization/upgrading scope. Generally, the hydropower plant assessment covers the following four main aspects which are interrelated and forming the basis for further decisions.
The identification of critical components in the sense of a risk evaluation is an integral part of a hydropower plant assessment. The main focus here is, to detect those components which can endanger the reliability of the plant, nevertheless, whether the said components are kept unchanged and unaffected by a modernization or upgrading scenario or whether some modification are necessary to them. The risk rating is based on a systematic evaluation of single components showing their actual risk status and the future risk level for the related modernization or upgrading scenario.
The aspect of limitations is coming close along with the risk identification but is not limited to it. Limitations can be deciding for the choice of the modernization or upgrading scenario. There are hydraulic, mechanic and electric limitations which have to be evaluated to achieve the boundary conditions for a modernization or upgrading project.
E.g. typical mechanical limitations are thrust bearing capacity, shaft dimensions and material (stresses), servomotor stroke, etc., on the electric side e.g. the capacity of the generator and/or transformer, runaway design speed.
An important outcome of a hydropower plant assessment is the extent of a possible modernization or upgrading potential. This could result in e.g. an increased energy production, a higher operational flexibility, reduced maintenance costs or use of state-of-the-art technical solutions with higher reliability.
With the fourth main aspect of a hydropower plant assessment a rough overview of the scope of work should be given. This scope should include the necessary overhaul, repair, modernization and/or upgrading works and related components to be reused or replaced. The scope thereby forms an executive summary of the assessment taking into account the other three main aspects.