IEC TS 63111:2025
(Main)Hydraulic turbines, storage pumps and pump-turbines – Hydraulic transient analysis, design considerations and testing
Hydraulic turbines, storage pumps and pump-turbines – Hydraulic transient analysis, design considerations and testing
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.
General Information
Standards Content (Sample)
IEC TS 63111 ®
Edition 1.0 2025-10
TECHNICAL
SPECIFICATION
Hydraulic turbines, storage pumps and pump-turbines – Hydraulic transient
analysis, design considerations and testing
ICS 27.140 ISBN 978-2-8327-0605-3
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CONTENTS
FOREWORD . 9
INTRODUCTION . 11
1 Scope . 12
2 Normative references . 13
3 Terms, definitions, symbols and units . 13
3.1 General . 13
3.2 General terminology . 14
3.3 Units . 14
3.4 Terms, definitions, symbols and units . 15
3.4.1 List of terms, definitions, symbols and units . 15
3.4.2 Subscripts and symbols . 15
3.4.3 Geometric terms . 16
3.4.4 Physical quantities and properties . 19
3.4.5 Discharge, velocity, speed terms and time symbols . 19
3.4.6 Pressure terms . 20
3.4.7 Specific energy terms . 20
3.4.8 Height and head terms . 21
3.4.9 Power and torque terms . 22
3.4.10 General terms relating to fluctuating quantities . 23
3.4.11 Fluid dynamic and scaling terms . 25
3.4.12 Dimensionless terms . 25
3.5 Abbreviated terms . 26
4 Hydraulic transient basics . 27
4.1 Elements related to hydraulic transient . 27
4.1.1 General . 27
4.1.2 Waterways system components . 27
4.1.3 Equipment . 31
4.1.4 Hydraulic machine . 35
4.1.5 Electro-mechanical equipment . 48
4.1.6 Other devices . 49
4.1.7 Opening and closing laws of flow control devices . 50
4.2 Hydraulic transient phenomena . 51
4.2.1 Waterhammer . 51
4.2.2 Mass oscillation . 51
4.2.3 Hydraulic machine transients . 51
4.2.4 Counter thrust and unit uplift . 54
4.3 Relevant hydraulic transient constant . 54
4.3.1 Water starting time T . 54
w
4.3.2 Unit acceleration constant T . 55
a
4.3.3 Small-signal stability indicator . 55
4.3.4 Penstock reflection time T . 55
r
4.3.5 Period of mass oscillations T . 56
mo
4.3.6 Thoma critical cross sections A . 56
Th
4.3.7 Ratio between surge tanks . 57
4.4 Types of transient load cases . 57
4.4.1 General . 57
4.4.2 Normal load cases (NOR) . 57
4.4.3 Exceptional load cases (EXC) . 59
4.4.4 Catastrophic load cases (C) . 60
4.4.5 Combination of load cases (CO) . 60
4.5 Depths of transient analysis at different project stages . 61
4.5.1 General . 61
4.5.2 New power plants . 61
4.5.3 Plant modification projects . 62
4.6 Limitations and exclusions of the specifications . 63
4.6.1 General . 63
4.6.2 Two phase flow. 64
4.6.3 Cavitation . 64
4.6.4 Water column separation . 64
4.6.5 Free surface flows . 64
4.6.6 Turbine governor . 64
4.6.7 Countries with extremely low temperatures . 65
4.6.8 Fluid structure interactions . 65
4.6.9 Unsteady friction . 65
4.6.10 Viscoelasticity . 65
4.6.11 Flow induced pressure fluctuations . 65
4.6.12 Variable-speed machines . 66
5 Modelling and computation methods . 66
5.1 Governing equations . 66
5.1.1 General . 66
5.1.2 Friction factor . 66
5.1.3 Wave speed . 68
5.2 Solution methods . 71
5.2.1 Analytical methods . 71
5.2.2 Graphical method . 73
5.2.3 Method of characteristics . 75
5.2.4 Finite difference method . 77
5.2.5 Remarks to the solution methods . 78
5.3 Wave speed adaptations and accuracy . 79
5.4 Hydraulic components modelling . 81
5.4.1 General . 81
5.4.2 Elastic column model of pipes . 81
5.4.3 Rigid water column model . 82
5.4.4 Equivalent pipes . 82
5.4.5 Singular head losses . 83
5.4.6 Valves . 84
5.4.7 Surge tanks . 85
5.4.8 Hydraulic turbines . 89
5.5 Limitations of the models for different purposes . 94
5.6 Validation (Performance) of transient analysis software . 96
6 Hydraulic transient calculation . 97
6.1 General . 97
6.2 Transient load case definition and computation methodology . 98
6.2.1 Transient load case definition . 98
6.2.2 Methodology for transient load case computation . 99
6.3 Short list of load cases . 109
6.3.1 General . 109
6.3.2 Normal load cases . 109
6.3.3 Exceptional load cases . 112
6.3.4 Catastrophic load case . 116
6.3.5 Load case combination . 117
6.4 Identification of load cases by critical values .
...
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