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The integration of non-predictable, intermittent and non-storable renewable energies is driving electricity producers to modify the operating patterns of existing power plants and to look for more storage capability. Pumped Storage Power Plants (PSP) are recognized as the most viable means of large-scale energy storage. PSPs are required to reach several thousand starts and stops per year and to accept frequent load variations to support balancing and network regulation needs. This high number of starts/stops of the units induces transient pressure fluctuation in the penstocks. This paper presents the impact of these phenomena on the fatigue life of high pressure penstocks of PSPs and the mandatory analysis that is part of a safe design. Site test feedback and calculation results are covered, including: Comparison with on-site measurements; impact of pressure cycling on fatigue strength; impact of distributor closing laws on pressure fluctuation in the penstock; mandatory aspects when using High Strength Steels (HSS) for penstocks (construction code & impact on fatigue behaviour and erection). The conclusion outlines the current knowledge of various phenomena impacting the fatigue life of penstocks under high pressure and some guidelines which should be taken into account for a safe design.