prEN IEC 60041:2026

• Status: Not Published
• Publication Date: 14-Feb-2028
• ICS: 27.140 - Hydraulic energy engineering
• Technical Committee: CLC/SR 4 - Hydraulic turbines
• Drafting Committee: IEC/TC 4 - IEC_TC_4
• Current Stage: 4020 - Enquiry circulated - Enquiry
• Start Date: 24-Jul-2026
• Due Date: 29-Dec-2023
• Completion Date: 24-Jul-2026
• Ref Project: oSIST prEN IEC 60041:2026 - Field acceptance tests to determine the hydraulic performance of hydraulic turbines, storage pumps and pump-turbines

• Revises: EN 60041:1994 - Field acceptance tests to determine the hydraulic performance of hydraulic turbines, storage pumps and pump-turbines
• Effective Date: 22-Jan-2023

Overview

prEN IEC 60041:2026 is an international standard developed by the International Electrotechnical Commission (IEC) and adopted by CENELEC (CLC). The standard specifies field acceptance tests to determine the hydraulic performance of hydraulic turbines, storage pumps, and pump-turbines. These tests are crucial for verifying that hydraulic machines meet contractual performance guarantees, ensuring efficiency, reliability, and safety in hydropower facilities. The procedures outlined provide a recognized and harmonized approach to performance assessment under actual operating conditions.

Key Topics

The standard addresses several core aspects related to the hydraulic performance testing of hydroelectric equipment:

• General rules and terminology: Definitions of key terms, symbols, and units used throughout the document, ensuring consistency and clarity.
• Performance guarantees: Procedures for specifying and assessing power output, discharge, efficiency, and other performance metrics. This includes the nature and extent of guarantees, such as maximum overspeed, pressure, and shut-off power.
• Test organization and planning: Guidelines on test preparation, including personnel roles, data acquisition systems, calibration, and approval of test procedures.
• Test methods: Detailed methodologies for conducting both steady-state and transient tests to assess machine performance under real-world conditions.
• Techniques for measurement: Multiple recognized methods for measuring key parameters like discharge (current-meter, Pitot tubes, pressure-time, dye dilution, weirs, acoustic transit time) and power (electrical and mechanical).
• Analysis and reporting: Techniques for computing and analyzing test data, addressing uncertainties, and comparing results against contractual guarantees.
• Uncertainty evaluation: Guidance on identifying sources of error, performing uncertainty analysis, and ensuring robustness of results.

Applications

The practical value of prEN IEC 60041:2026 lies in its widespread applicability across the hydropower industry:

• Contractual acceptance: Provides a common basis for acceptance testing between owners, operators, manufacturers, and contractors in hydropower projects.
• Commissioning of new installations: Ensures that new hydro turbines, storage pumps, and pump-turbines meet specified hydraulic performance criteria after installation.
• Routine performance monitoring: Facilitates ongoing assessment of machine efficiency and operational integrity, supporting maintenance and optimization efforts.
• Modernization projects: Used when upgrading existing equipment to verify improvements in efficiency or output.
• Regulatory compliance: Supports verification for compliance with national and international regulations regarding hydraulic energy performance.

Related Standards

Hydropower professionals often refer to related standards in conjunction with prEN IEC 60041:2026, including:

• IEC 60193: Laboratory model tests of hydraulic turbines, storage pumps, and pump-turbines, which complements field acceptance with laboratory-based assessments.
• IEC 61362: Guide to specification of hydraulic turbine tests, offering assistance in drafting test specifications.
• IEC 62270: Commissioning of electrical, mechanical, and control equipment at hydropower plants.
• ISO/IEC 17025: General requirements for the competence of testing and calibration laboratories.

Conclusion

Adopting prEN IEC 60041:2026 ensures standardized, accurate, and reliable assessment of the hydraulic performance of hydro turbines and pumps. It fosters trust among stakeholders in hydropower projects, protects investments, and drives operational excellence, underpinning sustainable hydropower development and efficient energy production. For engineers, plant owners, and equipment manufacturers, compliance with this standard is essential for the successful commissioning and long-term operation of hydraulic energy systems.

SLOVENSKI STANDARD
01-september-2026
Terenski prevzemni preskusi za ugotavljanje zmogljivosti vodnih turbin,
akumulacijskih črpalk in črpalnih turbin
Field acceptance tests to determine the hydraulic performance of hydraulic turbines,
storage pumps and pump-turbines
Abnahmeversuche zur Bestimmung der hydraulischen Eigenschaften von
Wasserturbinen, Speicherpumpen und Pumpturbinen
Essais de réception sur place des turbines hydrauliques, pompes d'accumulation et
pompes-turbines, en vue de la détermination de leurs performances hydrauliques
Ta slovenski standard je istoveten z: prEN IEC 60041:2026
ICS:
27.140 Vodna energija Hydraulic energy engineering
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

4/557/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 60041 ED4
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2026-07-24 2026-10-16
SUPERSEDES DOCUMENTS:
4/453/CD, 4/466A/CC
IEC TC 4 : HYDRAULIC TURBINES
SECRETARIAT: SECRETARY:
Canada Mrs Christine Geraghty
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):

ASPECTS CONCERNED:
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft
for Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of
which they are aware and to provide supporting documentation.
Recipients of this document are invited to submit, with their comments, notification of any relevant “In Some
Countries” clauses to be included should this proposal proceed. Recipients are reminded that the CDV stage is
the final stage for submitting ISC clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Field acceptance tests to determine the hydraulic performance of hydraulic turbines, storage
pumps and pump-turbines
PROPOSED STABILITY DATE: 2028
NOTE FROM TC/SC OFFICERS:
download this electronic file, to make a copy and to print out the content for the sole purpose of preparing National
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IEC CDV 60041 © IEC 2026
1 CONTENTS
2 FOREWORD . 13
3 SECTION ONE – GENERAL RULES . 16
4 1 Scope and object . 16
5 1.1 Scope . 16
6 1.2 Object . 16
7 1.3 Types of machines . 16
8 1.4 Excluded topics. 17
9 2 Normative references . 17
10 3 Terms, definitions, symbols and units . 18
11 3.1 General . 18
12 3.2 Units . 18
13 3.3 List of terms, definitions, symbols and units . 18
14 3.3.1 Subscripts and symbols . 18
15 3.3.2 Geometric terms . 20
16 3.3.3 Physical quantities and properties . 20
17 3.3.4 Discharge, velocity and speed terms . 22
18 3.3.5 Pressure terms . 23
19 3.3.6 Specific energy terms . 24
20 3.3.7 Height and head terms. 26
21 3.3.8 Power terms . 33
22 3.3.9 Efficiency terms . 35
23 4 Nature and extent of hydraulic performance guarantees . 36
24 4.1 General . 36
25 4.2 Main guarantees . 37
26 4.2.1 Practical plant operation . 37
27 4.2.2 The conditions of the unit . 37
28 4.2.3 Power . 37
29 4.2.4 Discharge . 38
30 4.2.5 Efficiency . 38
31 4.2.6 Choice of power, discharge and efficiency guarantees . 38
32 4.2.7 Maximum momentary overspeed and maximum/minimum momentary
,
33 pressure (see 3.3.4.14 and 3.3.5.7) . 38
34 4.2.8 Maximum steady state runaway speed (see 3.3.4.15) . 39
35 4.2.9 Maximum zero-discharge specific hydraulic energy and zero-discharge
36 (shut-off) power of a pump (see 3.3.6.5 and 3.3.8.6) . 39
37 4.3 Other guarantees . 39
38 4.3.1 General . 39
39 4.3.2 Speed governing systems . 39
40 4.3.3 Cavitation pitting . 39
41 5 Organisation of test . 40
42 5.1 Adequate provision for test . 40
43 5.2 Authority for test . 41
44 5.3 Personnel . 41
45 5.3.1 General . 41
46 5.3.2 Chief of test . 41
47 5.3.3 Choice of personnel . 41
IEC CDV 60041 © IEC 2026
48 5.3.4 Presence at test . 41
49 5.4 Preparation for test . 41
50 5.4.1 Submission of drawings and relevant data . 41
51 5.4.2 Inspection on site . 41
52 5.4.3 Measurements before test . 42
53 5.5 Agreement on test procedure . 42
54 5.5.1 Approval of procedure . 42
55 5.5.2 Date of test . 42
56 5.5.3 General programme . 42
57 5.6 Data Acquisition and Processing System . 43
58 5.6.1 General . 43
59 5.6.2 General requirements . 43
60 5.6.3 Observation sheets . 44
61 5.6.4 Components of a Data Acquisition System . 45
62 5.6.5 Calibration of components . 47
63 5.6.6 Check of the data acquisition system . 47
64 5.6.7 Manual instrument readings . 47
65 5.6.8 Data acquisition and data processing . 47
66 5.6.9 Preliminary calculation . 48
67 5.6.10 Signing of readings and recordings . 48
68 5.7 Procedure in case of dispute or repetition . 48
69 5.8 Inspection after test . 48
70 5.9 Final report . 48
71 5.9.1 Preparation of final report . 48
72 5.9.2 Content. 48
73 SECTION TWO – EXECUTION OF TEST FOR THE DETERMINATION OF THE
74 STEADY STATE PERFORMANCE OF THE MACHINE . 50
75 6 Test conditions and procedure . 50
76 6.1 General test procedure . 50
77 6.1.1 Methods of measurement . 50
78 6.1.2 Number of runs, readings and points . 50
79 6.1.3 Recommended test procedures . 50
80 6.1.4 Particular procedure for double regulated turbines . 51
81 6.1.5 Particular procedure for single regulated or double regulated pumps . 51
82 6.2 Test conditions to be fulfilled . 52
83 6.2.1 General . 52
84 6.2.2 Fluctuations and variations during a run (see 3.1) . 52
85 6.2.3 Deviations of average specific hydraulic energy and rotational speed
86 from specified values during a run (see 3.1) . 52
87 6.2.4 Net positive suction specific energy (see 3.3.6.9) and tailwater level
88 during the measurement of a point (see 3.1) . 53
89 7 Computation and analysis of results . 53
90 7.1 Computation of test results . 53
91 7.1.1 Compilation of a point . 53
92 7.1.2 Conversion and correction of test results to specified conditions . 53
93 7.1.3 Test curves . 57
94 7.2 Uncertainties in measurements and presentation of results . 58
95 7.2.1 Definition of error . 58
96 7.2.2 Definition of uncertainty . 58
IEC CDV 60041 © IEC 2026
97 7.2.3 Types of errors . 58
98 7.2.4 Total uncertainty . 60
99 7.2.5 Analysis of results . 60
100 7.2.6 Presentation of results . 60
101 7.3 Comparison with guarantees . 61
102 7.3.1 General . 61
103 7.3.2 Power (see 4.2.3) . 61
104 7.3.3 Discharge (see 4.2.4) . 63
105 7.3.4 Efficiency (see 4.2.5) . 64
106 SECTION THREE – EXECUTION OF TEST FOR THE DETERMINATION OF THE
107 TRANSIENT CHARACTERISTIC OF THE MACHINE . 69
108 8 Test conditions and procedure . 69
109 8.1 Test conditions . 69
110 8.1.1 General . 69
111 8.1.2 Speed variations . 69
112 8.1.3 Pressure variations . 69
113 8.2 Test procedure and instrumentation . 70
114 8.2.1 General requirements . 70
115 8.2.2 Measurement of speed variations . 70
116 8.2.3 Measurement of pressure variations . 70
117 8.2.4 Measurement of the movement of shut-off devices . 70
118 9 Computation and analysis of results . 70
119 9.1 Conversion of results . 70
120 9.2 Comparison with guarantees . 71
121 9.2.1 Nature and extent of guarantees . 71
122 9.2.2 Fulfilment of guarantees . 72
123 SECTION FOUR – METHODS OF MEASUREMENT . 73
124 10 Methods of measurement . 73
125 10.1 General . 73
126 10.2 Efficiency . 73
127 10.3 Hydraulic power . 73
128 10.3.1 Definition . 73
129 10.3.2 Mass flow rate . 74
130 10.3.3 Hydraulic power correction . 74
131 10.3.4 Water density . 74
132 10.4 Mechanical power . 75
133 10.5 Machine openings . 75
134 11 Discharge . 75
135 11.1 General . 75
136 11.1.1 Recommendations at the development stage . 75
137 11.1.2 Choice of the method of measurement . 75
138 11.1.3 Uncertainty of measurement . 76
139 11.1.4 General requirements . 76
140 11.1.5 Computational fluid dynamics (CFD) . 77
141 11.2 Current-meter method . 77
142 11.2.1 Principle of velocity-area method . 77
143 11.2.2 General requirements . 77
144 11.2.3 Measurements in closed conduits (penstocks) . 79
IEC CDV 60041 © IEC 2026
145 11.2.4 Measurements in short penstocks or intake structures . 80
146 11.2.5 Measurements in open channels . 83
147 11.2.6 Computation of discharge . 85
148 11.2.7 Uncertainty of measurement (see 11.1.3) . 86
149 11.3 Pitot tubes . 86
150 11.3.1 General . 86
151 11.3.2 Standardized Pitot tubes . 86
152 11.3.3 Non-standard devices . 86
153 11.4 Pressure-time method . 87
154 11.4.1 Principle of the method . 87
155 11.4.2 General requirements . 89
156 11.4.3 Measurement Methods . 91
157 11.4.4 Signal conditioning, data acquisition system and recordings . 93
158 11.4.5 Checking of the pressure measurements . 94
159 11.4.6 Computation of discharge . 95
160 11.4.7 Uncertainty of measurement . 97
161 11.5 Dye dilution method (Tracer methods). 98
162 11.5.1 Principle of the method . 98
163 11.5.2 Variants of the method . 100
164 11.5.3 Choice and properties of dye . 101
165 11.5.4 Setting up of initial and standard solution . 101
166 11.5.5 Types and calibration of fluorometer . 106
167 11.5.6 Injecting and extraction positions and methods . 108
168 11.5.7 Evaluation of measurement . 110
169 11.5.8 Uncertainty of measurement . 111
170 11.6 Weirs . 111
171 11.6.1 Principle of measurement . 111
172 11.6.2 Description of the measuring device . 111
173 11.6.3 Conditions of installation . 112
174 11.6.4 Measurement of head . 113
175 11.6.5 Discharge formulae. 116
176 11.6.6 Uncertainty of measurement (see 11.1.3) . 116
177 11.7 Standardized differential pressure devices . 116
178 11.7.1 Principle of the method . 116
179 11.7.2 Field of application . 117
180 11.7.3 Uncertainty of measurement . 117
181 11.8 Volumetric gauging method . 118
182 11.8.1 Principle of the method . 118
183 11.8.2 Basins for volumetric measurements . 118
184 11.8.3 Operation of measurement . 119
185 11.8.4 Analysis of the test results . 120
186 11.8.5 Uncertainty of measurement (see 11.1.3) . 120
187 11.9 Acoustic transit time. 121
188 11.9.1 General . 121
189 11.9.2 Principle of measurement . 121
190 11.9.3 Methods of discharge calculation . 123
191 11.9.4 Methods of velocity calculation . 127
192 11.9.5 Methods of transit time determination . 129
193 11.9.6 Methods of acoustic signal detection and qualification . 130
IEC CDV 60041 © IEC 2026
194 11.9.7 Tests . 130
195 11.9.8 Selection of measuring section and conditions of installation . 130
196 11.9.9 Conditions of use and limitations . 132
197 11.9.10 Agreement Issues . 132
198 11.9.11 Uncertainty of measurement . 132
199 12 Specific hydraulic energy of the machine . 133
200 12.1 General . 133
201 12.1.1 Object . 133
202 12.1.2 Method of determination . 133
203 12.1.3 Steady-state conditions . 133
204 12.2 Determination of the specific hydraulic energy . 133
205 12.2.1 Measuring sections . 133
206 12.2.2 Reference levels . 134
207 12.2.3 Water density . 136
208 12.2.4 Specific kinetic energy . 136
209 12.2.5 Simplified formulae . 136
210 12.3 Determination of the net positive suction specific energy . 143
211 12.3.1 Definition . 143
212 12.3.2 Simplified formulae . 143
213 12.4 Pressure measurements . 144
214 12.4.1 Choice of pressure measuring section . 144
215 12.4.2 Number and location of pressure taps . 145
216 12.4.3 Pressure taps . 145
217 12.4.4 Gauge piping . 146
218 12.4.5 Measuring apparatus . 147
219 12.4.6 Checking of pressure gauges . 150
220 12.4.7 Vacuum measurements . 151
221 12.5 Free water level measurements . 151
222 12.5.1 General . 151
223 12.5.2 Choice of water level measuring sections . 152
224 12.5.3 Number of measuring points in a measuring section . 152
225 12.5.4 Measuring apparatus . 152
226 12.6 Determination of the specific hydraulic energy measurement uncertainty . 156
227 13 Power . 156
228 13.1 Indirect method of power measurement. 156
229 13.1.1 General . 156
230 13.1.2 Electrical power Pa . 157
231 13.1.3 Determination of losses . 165
232 13.1.4 Uncertainty of measurement . 171
233 13.2 Bearing losses . 171
234 13.2.1 General . 171
235 13.2.2 Calculation of thrust bearing losses . 171
236 13.2.3 Calculation of guide bearing losses . 172
237 13.2.4 Hydraulic thrust measurement . 173
238 14 Rotational speed . 173
239 14.1 General . 173
240 14.2 Speed measurements . 173
241 14.3 Uncertainty of measurements . 174
242 15 Thermodynamic method for measuring efficiency . 174
IEC CDV 60041 © IEC 2026
243 15.1 General . 174
244 15.1.1 Principle . 174
245 15.1.2 Excluded topics and limitations . 174
246 15.1.3 Instrumentation . 174
247 15.2 Efficiency and specific mechanical energy . 175
248 15.3 Procedure for measurement of specific mechanical energy . 176
249 15.3.1 General . 176
250 15.3.2 Direct operating procedure . 178
251 15.3.3 Cross check of mechanical energy. 178
252 15.3.4 Thermometer calibration . 179
253 15.4 Apparatus . 179
254 15.4.1 Main measurements . 179
255 15.4.2 Auxiliary measurements . 181
256 15.5 Test conditions to be fulfilled . 181
257 15.5.1 Measuring sections and sampling conditions . 181
258 15.5.2 Particular flow arrangements . 184
259 15.5.3 Unfavourable operating conditions . 184
260 15.6 Corrective terms . 184
261 15.6.1 General . 184
262 15.6.2 Variations of temperature . 184
263 15.6.3 Extraneous heat exchange . 185
264 15.6.4 Limit of corrections . 186
265 15.7 Uncertainty of measurement . 187
266 15.7.1 General . 187
267 15.7.2 Evaluation procedure of the energy distribution . 187
268 16 Index tests . 188
269 16.1 General . 188
270 16.1.1 Object . 188
271 16.1.2 Definition of index value and relative value . 189
272 16.1.3 Applications . 189
273 16.2 Index discharge measurement . 190
274 16.2.1 General . 190
275 16.2.2 Index discharge measurement by differential pressure methods . 190
276 16.2.3 Index discharge measurement by velocity measurement methods . 194
277 16.2.4 Relative discharge measurement by means of the regulating apparatus
278 device . 194
279 16.2.5 Other methods of obtaining relative discharge . 195
280 16.3 Measurement of other quantities . 195
281 16.3.1 Specific hydraulic energy . 195
282 16.3.2 Power . 195
283 16.3.3 Rotational speed. 195
284 16.3.4 Machine openings . 195
285 16.4 Computation of results . 195
286 16.5 Uncertainty of measurement, considerations and evaluation . 196
287 16.5.1 General . 196
288 16.5.2 Winter Kennedy coefficient and changes in velocity distribution . 196
289 16.5.3 Multiple velocity inputs for reducing uncertainty and as a base for
290 analysing uncertainty . 196
291 17 Comparative tests . 198
IEC CDV 60041 © IEC 2026
292 Annex A (informative) Systematic uncertainties in performance measurements at
293 steady state conditions . 200
294 A.1 Usual values of systematic uncertainties in the various quantities . 200
295 A.2 Uncertainty analysis for thermodynamic test . 202
296 A.2.1 General . 202
297 A.2.2 Uncertainty in specific mechanical energy E . 202
m
298 A.2.3 Uncertainty in specific hydraulic energy E . 205
299 A.3 Example of calculation of systematic uncertainty in the specific hydraulic
300 energy of machine and in the derived efficiency . 206
301 A.4 Example of calculation of systematic uncertainty in the specific mechanical
302 energy at runner and in the derived efficiency . 207
303 A.5 Evaluation procedure of the energy distribution . 211
304 A.5.1 Measuring arrangement according to 15.5.1.3.1, “Open measuring
305 section”: . 211
306 A.5.2 Measuring arrangement according to 15.5.1.3.2, “Closed measuring
307 section”: . 214
308 A.6 Uncertainty for a comparative test . 214
309 Annex B (informative) Rejection of outliers . 215
310 Annex C (informative) Analysis of the random uncertainty for a test at constant
311 operating conditions . 217
312 C.1 General . 217
313 C.2 Standard deviation . 217
314 C.3 Confidence levels . 218
315 C.4 Student’s t distribution . 218
316 C.5 Maximum permissible value of uncertainty . 219
317 C.6 Example of calculation . 219
318 Annex D (informative) Analysis of the random uncertainties for a test over a range of
319 operating conditions . 221
320 D.1 General remarks . 221
321 D.2 Determination of the best smooth curve . 221
322 D.3 Estimation of uncertainty . 222
323 D.4 Example of calculation . 223
324 Annex E (normative) Physical data . 225
325 E.1 Acceleration due to gravity as a function of latitude and altitude . 225
326 E.2 Density of water . 226
327 E.3 Density of air . 227
328 E.4 Isothermal Throttling coefficient of water . 229
329 E.5 Specific heat capacity of water . 231
330 E.6 Vapour pressure of distilled water . 233
331 E.7 Formulation of the thermodynamic properties of sea water . 233
332 E.8 Formulation of the thermodynamic properties of water . 233
333 E.9 Dynamic viscosity of the water . 235
334 Annex F (normative) Derivation of the equation for the specific hydraulic energy of a
335 machine . 238
336 F.1 Theoretical equation . 238
337 F.2 Specific pressure energy term . 238
338 F.3 Specific potential energy term . 239
339 F.4 Practical equation . 239
340 Annex G (normative) Measurement of electric power – Determination of the correction
341 for a single-phase measuring system . 240
IEC CDV 60041 © IEC 2026
342 Annex H (normative) Thermodynamic method – Balance of power and computation of
343 the specific mechanical energy . 242
344 H.1 Extracting a discharge q . 242
345 H.2 Adding a discharge q . 243
346 Annex I (informative) Acoustic scintillation method of discharge measurement . 245
347 I.1 General . 245
348 I.2 Principles of Measurement . 245
349 I.2.1 General . 245
350 I.2.2 Sequence of Measurements .
...