prBAS IEC TS 63111:2027

IEC TS 63111:2025 describes hydraulic transient phenomena of hydro turbines, storage pumps and pump-turbines and the factors that affect them, (2) provides modelling and measurement best practice guidelines and resulting limitations (3) defines relevant equipment design criteria, and (4) identifies potential mitigation solutions. Definitions of the relevant terms and quantities are provided along with descriptions of the system components that are considered. In this Technical Specification, abnormal transient phenomena are also defined and described, including component malfunction and catastrophic events like component rupture. The probability of the occurrence of these extreme events and how this can influence the relevant safety margin is described. This Technical Specification provides guidelines and commonly accepted practices to model and compute transient conditions. It provides a summary of the basic hypotheses and equations, together with relevant characteristic quantities and system time constants. Accepted methods of modelling hydraulic components, and related numerical simulation methods are identified. This specification details the input data, including best practices for model testing of hydraulic machines, valves, gates, etc. to acquire reliable transient modelling. This Technical Specification describes methodologies for on-site measurements with respect to transient such as load rejection tests, runaway tests, etc. Recommendations are provided for quantities to be monitored during these tests, with related instrumentation, calibration and data acquisition systems. Procedures for comparing on-site measurements with numerical simulation results are proposed.