SIST EN IEC 63461:2024

Pelton hydraulic turbines - Model acceptance tests (IEC 63461:2024)

IEC 63461:2024 applies to laboratory model tests of any type of Pelton hydraulic turbine with unit power greater than 5 MW. It contains the rules governing test conduct and provides measures to be taken if any phase of the tests is disputed.
The main objectives of this document are:
- to define the terms and quantities used;
- to specify methods of testing and of measuring the quantities involved, in order to ascertain the hydraulic performance of the model;
- to specify the methods of computation of results and of comparison with guarantees;
- to determine if the contract guarantees that fall within the scope of this document have been fulfilled;
- and to define the extent, content and structure of the final report.
Full application of the procedures herein described is not generally justified for machines with smaller power. Nevertheless, this document can be used for such machines by agreement between the purchaser and the supplier.

Hydraulische Pelton Turbinen - Modellabnahmeprüfungen (IEC 63461:2024)

Turbines hydrauliques Pelton - Essais de réception sur modèle (IEC 63461:2024)

IEC 63461:2024 s’applique aux essais de modèles de laboratoire de tout type de turbine Pelton d’une puissance unitaire supérieure à 5 MW. Il fixe les règles de conduite de ces essais et spécifie les mesures à prendre en cas de contestation d’une phase quelconque des essais.
Les principaux objectifs du présent document sont les suivants:
- définir les termes et les grandeurs utilisés;
- spécifier les méthodes d'essai et de mesure des grandeurs concernées, afin de déterminer les performances hydrauliques du modèle;
- spécifier les méthodes de calcul des résultats et de comparaison avec les garanties;
- déterminer si les garanties contractuelles qui relèvent du domaine d’application du présent document sont respectées;
- et définir l’étendue, le contenu et la structure du rapport final.
L’application intégrale des procédures décrites dans le présent document ne se justifie généralement pas pour les machines de puissance inférieure. Néanmoins, le présent document peut être utilisé pour de telles machines après accord entre l’acheteur et le fournisseur.

Peltonove vodne turbine - Prevzemni preskusi modela (IEC 63461:2024)

Standard IEC 63461:2024 se uporablja za laboratorijske preskuse modela Peltonove vodne turbine katere koli vrste z močjo enote, večjo od 5 MW. Vsebuje pravila, ki urejajo izvajanje preskusov, in določa ukrepe, ki jih je treba izvesti v primeru sporov glede ene od faz preskusov.
Glavni namen tega dokumenta je:
– opredelitev izrazov in količin, ki se uporabljajo;
– določitev metod za preskušanje in merjenje vključenih količin, da se opredeli hidravlična zmogljivost modela;
– določitev metod za izračun rezultatov in primerjavo z jamstvi;
– ugotovitev, ali so pogodbena jamstva, ki spadajo na področje uporabe tega dokumenta, izpolnjena; ter
– določitev obsega, vsebine in strukture končnega poročila.
Celotna uporaba postopkov, opisanih v tem dokumentu, na splošno ni utemeljena za stroje z manjšo močjo. Kljub temu pa je mogoče po dogovoru med kupcem in dobaviteljem ta dokument uporabiti tudi za take stroje .

General Information

• Status: Published
• Public Enquiry End Date: 27-Jul-2023
• Publication Date: 22-Aug-2024
• ICS: 27.140 - Hydraulic energy engineering
• Technical Committee: IEHT - Electrotechnics - Hydraulic turbins
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 21-Aug-2024
• Due Date: 26-Oct-2024
• Completion Date: 23-Aug-2024
• Ref Project: EN IEC 63461:2024 - Pelton hydraulic turbines - Model acceptance tests

Relations

• Replaces: SIST EN IEC 60193:2019 - Hydraulic turbines, storage pumps and pump-turbines - Model acceptance tests (IEC 60193:2019)
• Effective Date: 01-Oct-2024
• Corrected By: SIST EN IEC 63461:2024/AC:2025 - Pelton hydraulic turbines - Model acceptance tests (IEC 63461:2024/COR1:2025)
• Effective Date: 01-May-2025

Overview - IEC 63461:2024 (SIST EN IEC 63461:2024)

IEC 63461:2024 / SIST EN IEC 63461:2024 specifies requirements for laboratory model acceptance tests of Pelton hydraulic turbines with unit power greater than 5 MW. It defines terms and quantities, prescribes test conduct and measurement methods to ascertain hydraulic performance of turbine models, gives rules for computing and comparing results with contractual guarantees, and sets the required content and structure of the final test report. The standard can also be applied to smaller machines by agreement between purchaser and supplier.

SEO keywords: Pelton hydraulic turbines, model acceptance tests, IEC 63461:2024, turbine model tests, hydraulic performance.

Key technical topics and requirements

• Definitions & units: standardized terms, symbols and units to ensure consistent reporting of performance data.
• Test installation & model requirements: criteria for choice of laboratory, test rig layout and model construction, including dimensional checks and permissible deviations in geometrical similarity between prototype and model.
• Measurement methods: accepted procedures for measuring discharge, pressures, free water levels, shaft torque and rotational speed. Emphasis on calibration, selection of measurement sections, pressure taps and transducers.
• Data acquisition & processing: requirements for data acquisition systems, component performance, sampling of fluctuating quantities, signal processing and verification checks.
• Uncertainty and error analysis: procedures for estimating measurement uncertainties and reporting confidence levels for test results.
• Test execution & reporting: organization of tests, inspection and calibration routines, handling of faults and test repetition, preliminary and final test report structure.
• Contractual acceptance: methods for computing performance metrics, comparing measured results to guarantees, and measures to follow if test phases are disputed.

SEO keywords: discharge measurement, pressure measurement, shaft torque, uncertainty analysis, dimensional checks.

Practical applications and users

This standard is essential for:

• Turbine manufacturers conducting model acceptance tests to validate Pelton turbine hydraulic performance.
• Independent testing laboratories and research institutes performing scaled model tests.
• Hydropower project owners and procuring authorities verifying contractual performance guarantees.
• Design and performance engineers using model test data for prototype validation, efficiency curves and cavitation assessment.

Benefits include consistent, comparable test data, reduced contractual disputes, and traceable uncertainty estimates.

Related standards

Relevant referenced standards (normative and bibliographic) include ISO and IEC measurement standards such as ISO 4373, ISO 5167-1, IEC 60041, and the superseded EN IEC 60193:2019. These provide complementary guidance on flow, pressure and instrumentation best practices.

Standards Content (Sample)

SLOVENSKI STANDARD
01-oktober-2024
Peltonove vodne turbine - Prevzemni preskusi modela (IEC 63461:2024)
Pelton hydraulic turbines - Model acceptance tests (IEC 63461:2024)
Hydraulische Pelton Turbinen - Modellabnahmeprüfungen (IEC 63461:2024)
Turbines hydrauliques Pelton - Essais de réception sur modèle (IEC 63461:2024)
Ta slovenski standard je istoveten z: EN IEC 63461:2024
ICS:
27.140 Vodna energija Hydraulic energy engineering
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 63461

NORME EUROPÉENNE
EUROPÄISCHE NORM August 2024
ICS 27.140 Supersedes EN IEC 60193:2019
English Version
Pelton hydraulic turbines - Model acceptance tests
(IEC 63461:2024)
Turbines Pelton - Essais de réception sur modèle Hydraulische Pelton Turbinen - Modellabnahmeprüfungen
(IEC 63461:2024) (IEC 63461:2024)
This European Standard was approved by CENELEC on 2024-08-02. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 63461:2024 E
European foreword
The text of document 4/460/CDV, future edition 1 of IEC 63461, prepared by IEC/TC 4 "Hydraulic
turbines" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2025-05-02
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2027-08-02
document have to be withdrawn
This document supersedes EN IEC 60193:2019 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 63461:2024 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standard indicated:
IEC 60041:1991 NOTE Approved as EN 60041:1994
IEC 60609-1:2004 NOTE Approved as EN 60609-1:2005 (not modified)
IEC 60609-2:1997 NOTE Approved as EN 60609-2:1999 (not modified)
IEC 60994:1991 NOTE Approved as EN 60994:1992 (not modified)
ISO 4006:1991 NOTE Approved as EN 24006:1993 (not modified)
ISO 4373:2022 NOTE Approved as EN ISO 4373:2022 (not modified)
ISO 5167-1:2022 NOTE Approved as EN ISO 5167-1:2022 (not modified)
ISO 20456:2017 NOTE Approved as EN ISO 20456:2019 (not modified)
ISO 80000-4:2019 NOTE Approved as EN ISO 80000-4:2019 (not modified)
ISO 80000-11:2019 NOTE Approved as EN ISO 80000-11:2020 (not modified)
ISO 21920-2:2021 NOTE Approved as EN ISO 21920-2:2022 (not modified)
IEC 60609 series NOTE Approved as EN 60609 series
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
ISO 2186 2007 Fluid flow in closed conduits_- Connections - -
for pressure signal transmissions between
primary and secondary elements
ISO 2533 1975 Standard Atmosphere - -
ISO 4185 1980 Measurement of liquid flow in closed EN 24185 1993
conduits - Weighing method
- - + AC 1993
ISO 8316 1987 Measurement of liquid flow in closed EN ISO 8316 1995
conduits - Method by collection of the liquid
in a volumetric tank
IEC 63461 ®
Edition 1.0 2024-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Pelton hydraulic turbines – Model acceptance tests

Turbines Pelton – Essais de réception sur modèle

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.140  ISBN 978-2-8322-9236-5

– 2 – IEC 63461:2024 © IEC 2024
CONTENTS
FOREWORD . 9
1 Scope . 11
2 Normative references . 12
3 Terms, definitions, symbols and units . 12
3.1 General . 12
3.2 Terms and definitions. 12
3.3 Units . 14
3.4 Terms, definitions, symbols and units . 14
3.4.1 List by topics . 14
3.4.2 Subscripts and symbols . 15
3.4.3 Geometry . 16
3.4.4 Physical quantities and properties . 17
3.4.5 Discharge, velocity and speed . 18
3.4.6 Pressure . 18
3.4.7 Specific energy . 19
3.4.8 Height and head . 19
3.4.9 Power and torque . 20
3.4.10 Efficiency . 22
3.4.11 Fluctuating quantities . 22
3.4.12 Fluid dynamics and scaling . 25
3.4.13 Dimensionless terms and definitions . 25
3.4.14 Additional performance data . 26
4 Physical properties . 26
4.1 General . 26
4.2 Acceleration due to gravity . 26
4.3 Physical properties of water . 27
4.3.1 Density of water . 27
4.3.2 Kinematic viscosity . 30
4.3.3 Vapour pressure . 30
4.4 Physical conditions of atmosphere . 31
4.4.1 Density of dry air . 31
4.4.2 Ambient pressure . 31
4.5 Density of mercury . 31
5 Requirements of tests . 32
5.1 Requirement of test installation and model . 32
5.1.1 Choice of laboratory . 32
5.1.2 Test installation . 32
5.1.3 Model requirements . 33
5.2 Dimensional check of model and prototype . 35
5.2.1 General . 35
5.2.2 Explanation of terms used for model and prototype. 36
5.2.3 Purpose of dimensional checks. 36
5.2.4 General rules . 36
5.2.5 Procedure . 37
5.2.6 Methods . 38
5.2.7 Accuracy of measurements . 41
5.2.8 Dimensions of model and prototype to be checked . 41

IEC 63461:2024 © IEC 2024 – 3 –
5.2.9 Permissible maximum deviations in geometrical similarity between
prototype and model . 43
5.2.10 Surface waviness and roughness . 44
5.3 Test procedures . 46
5.3.1 Organization of tests. 46
5.3.2 Inspections and calibrations . 48
5.3.3 Execution of tests . 50
5.3.4 Faults and repetition of tests . 54
5.3.5 Preliminary test report . 55
5.3.6 Final test report . 55
6 Data acquisition . 55
6.1 Data acquisition and data processing . 55
6.1.1 General . 55
6.1.2 General requirements . 56
6.1.3 Data acquisition . 56
6.1.4 Component requirements . 58
6.1.5 Check of the data acquisition system . 61
6.2 Data acquisition and processing for measurement of fluctuating quantities . 63
6.2.1 General . 63
6.2.2 Data acquisition . 64
6.2.3 Data processing. 66
6.3 Error analysis . 67
6.3.1 Definitions . 67
6.3.2 Determination of uncertainties in model tests . 69
7 Methods of measurement . 74
7.1 Discharge measurement . 74
7.1.1 General . 74
7.1.2 Choice of the method of measurement . 75
7.1.3 Accuracy of measurement . 75
7.1.4 Primary methods . 76
7.1.5 Secondary methods . 77
7.2 Pressure measurement . 80
7.2.1 General . 80
7.2.2 Choice of pressure-measuring section . 80
7.2.3 Pressure taps and connecting lines . 81
7.2.4 Apparatus for pressure measurement . 84
7.2.5 Calibration of pressure measurement apparatus . 90
7.2.6 Vacuum measurements . 91
7.2.7 Uncertainty in pressure measurements . 91
7.3 Free water level measurement (see also ISO 4373) . 91
7.3.1 General . 91
7.3.2 Choice of water level measuring sections . 92
7.3.3 Number of measuring points in a measuring section . 92
7.3.4 Measuring methods . 92
7.3.5 Uncertainty in free water level measurement . 93
7.4 Shaft torque measurement . 94
7.4.1 General . 94
7.4.2 Methods of torque measurement . 94
7.4.3 Methods of absorbing/generating power . 95

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7.4.4 Layout of arrangement . 95
7.4.5 Checking of system . 99
7.4.6 Calibration . 100
7.4.7 Uncertainty in torque measurement (at a confidence level of 95 %) . 100
7.5 Rotational speed measurement . 102
7.5.1 General . 102
7.5.2 Methods of speed measurement . 102
7.5.3 Checking . 102
7.5.4 Uncertainty of measurement . 102
8 Test execution and results . 102
8.1 General . 102
8.2 Determination of E . 103
8.2.1 General . 103
8.2.2 Determination of the specific hydraulic energy E . 103
8.2.3 Simplified formulae for E . 106
8.3 Determination of power and efficiency . 108
8.3.1 Hydraulic power . 108
8.3.2 Mechanical power . 109
8.3.3 Hydraulic efficiency . 109
8.4 Hydraulic similitude . 110
8.4.1 Theoretical basic requirements and similitude numbers . 110
8.4.2 Conditions for hydraulic similitude as used in this document . 110
8.4.3 Similitude requirements for various types of model tests . 111
8.4.4 Reynolds similitude . 111
8.4.5 Froude similitude . 111
8.4.6 Other similitude conditions - Weber number . 111
8.5 Test conditions . 112
8.5.1 Determination of test conditions . 112
8.5.2 Minimum values for model size and test conditions to be fulfilled . 112
8.5.3 Stability and fluctuations during measurements . 113
8.5.4 Adjustment of the operating point . 113
8.6 Computation and presentation of test results . 113
8.6.1 General . 113
8.6.2 Power, discharge and efficiency in the guarantee range . 114
8.6.3 Computation of steady-state runaway speed and discharge . 118
9 Nature and extent of guarantees related to hydraulic performance . 119
9.1 General . 119
9.1.1 Design data and coordination . 119
9.1.2 Definition of the hydraulic performance guarantees . 120
9.1.3 Guarantees of correlated quantities . 120
9.1.4 Form of guarantees . 120
9.2 Main hydraulic performance guarantees verifiable by model test . 121
9.2.1 Guaranteed quantities for any machine . 121
9.2.2 Specific application . 121
9.3 Guarantees not verifiable by model test . 121
9.3.1 Guarantees on cavitation erosion . 121
9.3.2 Guarantees on maximum momentary overspeed and maximum
momentary pressure rise . 121
9.3.3 Guarantees covering noise and vibration . 122

IEC 63461:2024 © IEC 2024 – 5 –
9.3.4 Measurements not covered by this document . 122
9.4 Comparison with guarantees . 122
9.4.1 General . 122
9.4.2 Interpolation curve and total uncertainty bandwidth . 122
9.4.3 Power, discharge and/or specific hydraulic energy and efficiency in the

guarantee range . 123
9.4.4 Prototype mechanical losses . 124
9.4.5 Runaway speed and discharge . 124
9.4.6 Penalty and premium . 125
10 Additional performance data – Methods of measurement and results . 125
10.1 Additional data measurement . 125
10.1.1 General . 125
10.1.2 Test conditions and test procedures . 126
10.1.3 Uncertainty in measurements . 126
10.1.4 Model to prototype conversion . 127
10.2 Hydraulic loads on control components . 127
10.2.1 General . 127
10.2.2 Pelton needle force and deflector torque . 128
10.3 Influence of tail water level . 131
10.4 Testing in an extended operating range . 131
10.4.1 General . 131
10.4.2 Scope of tests . 131
10.4.3 Methods of testing in the extended operating range . 132
10.5 Differential pressure measurement in view of prototype index test . 133
10.5.1 General . 133
10.5.2 Purpose of test . 133
10.5.3 Execution of test . 133
10.5.4 Analysis of test results . 134
10.5.5 Transposition to prototype conditions . 135
10.5.6 Uncertainty . 135
10.6 Nozzle flow discharge calibration in view of prototype index test . 135
Annex A (informative) Dimensionless terms . 136
Annex B (normative) Physical properties, data . 138
Annex C (informative) Summarized test and calculation procedure . 146
C.1 General . 146
C.2 Agreements to be reached prior to testing . 146
C.3 Model, test facility and instrumentation . 147
C.3.1 Model manufacture and dimensional checks . 147
C.3.2 Test facility instrumentation and data acquisition system . 147
C.4 Tests and calculation of the model values . 147
C.4.1 Test types. 147
C.4.2 Measurement of the main quantities during the test . 147
C.4.3 Uncertainty of the measured quantities . 148
C.4.4 Calculation of the quantities related to the main hydraulic performance . 148
C.4.5 Calculation of the dimensionless factors or coefficients and of the

Thoma number . 148
C.5 Calculation of prototype quantities . 148
C.6 Plotting of model or prototype results . 149
C.7 Comparison with the guarantees . 149

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C.8 Final protocol . 149
C.9 Final test report . 149
Annex D (normative) Computation of the prototype runaway characteristics taking into
account friction and windage losses of the unit . 150
Annex E (informative) Example of determination of the best smooth curve: method of
separate segments . 151
E.1 General . 151
E.2 Principle of the method . 151
E.3 Choice of the minimum width of the intervals . 153
E.4 Determination of the intervals . 153
Annex F (informative) Examples of analysis of sources of error and uncertainty
evaluation . 154
F.1 General . 154
F.2 Example of analysis of sources of error and of uncertainty evaluation in the
measurement of a physical quantity . 154
F.2.1 General . 154
F.2.2 Errors arising during calibration . 155
F.2.3 Errors arising during the tests . 156
F.3 Example of calculation of uncertainty due to systematic errors in the
determination of the specific hydraulic energy, mechanical runner power and
hydraulic efficiency . 157
F.3.1 General . 157
F.3.2 Discharge . 157
F.3.3 Pressure . 157
F.3.4 Specific hydraulic energy . 157
F.3.5 Power . 158
F.3.6 Hydraulic efficiency . 159
Annex G (normative) The scale effect on hydraulic efficiency for Pelton turbines . 160
G.1 General . 160
G.2 Similarity considerations . 160
G.3 Transposition formula . 162
Annex H (normative) Analysis of random errors for a test at constant operating
conditions . 163
H.1 General . 163
H.2 Standard deviation . 163
H.3 Confidence levels . 164
H.4 Student's t distribution . 164
H.5 Maximum permissible value of uncertainty due to random errors. 165
H.6 Example of calculation . 166
Annex I (informative) Flux diagram of specific hydraulic energy and power . 167
Bibliography . 169

Figure 1 – Schematic representation of a Pelton machine . 16
Figure 2 – Reference diameter and bucket width . 17
Figure 3 – Reference level of a Pelton machine . 19
Figure 4 – Flux diagram for power . 21
Figure 5 – Illustration of some definitions related to oscillating quantities . 24
-2
Figure 6 – Acceleration due to gravity g (m ⋅ s ) . 27

IEC 63461:2024 © IEC 2024 – 7 –
−3
Figure 7 – Density of distilled water ρ (kg ⋅ m ) . 30
wd
Figure 8 – Example for homology limits for wetted parts of a vertical Pelton turbine . 34
Figure 9 – Example for homology limit for wetted parts of a horizontal Pelton turbine . 34
Figure 10 – Procedure for dimensional checks, comparison of results "steel to steel"
and application of tolerances for model and prototype . 37
Figure 11 – Pelton turbine: example of dimensions to be checked on the distributor and
the housing of vertical and horizontal shaft machines . 39
Figure 12 – Pelton turbine: example of dimensions to be checked on the buckets and
nozzles . 40
Figure 13 – Definition of waviness and surface roughness . 45
Figure 14 – Time multiplexing data acquisition system . 57
Figure 15 – Bus operated data acquisition system . 57
Figure 16 – Time delay . 59
Figure 17 – Typical low-pass filter attenuation characteristics . 59
Figure 18 – Different measurement chains and their recommended checkpoints . 62
Figure 19 – Typical data acquisition system . 64
Figure 20 – Frequency response of analogue anti-aliasing filter . 65
Figure 21 – Example of calibration curve . 70
Figure 22 – Examples of pressure taps . 82
Figure 23 – Types of pressure manifolds . 83
Figure 24 – Dead weight manometer with compensation by pressure or force
transducer (example of experimental set-up) . 88
Figure 25 – Pressure weighbeam (example of experimental set-up) . 89
Figure 26 – Stilling well . 92
Figure 27 – Point and hook gauges . 93
Figure 28 – Balance arrangement . 96
Figure 29 – Balance arrangement with two separate frames . 97
Figure 30 – Arrangement with machine bearings and seals not in balance . 97
Figure 31 – Arrangement using a torquemeter . 98
Figure 32 – Arrangement using a torquemeter with machine bearings and seals in
balance . 98
Figure 33 – Arrangement using a torquemeter with machine bearings and seals not in
balance . 99
Figure 34 – Example showing main elevations, heights and reference levels of the test
rig and model machine . 105
Figure 35 – Pelton turbines with horizontal axis: determination of specific hydraulic
energy of the machine . 108
Figure 36 – Pelton model turbine: performance hill diagram (example for a six-nozzle
machine) . 114
Figure 37 – Three-dimensional surface of hydraulic efficiency and curves of
performance at E constant . 116
nD
Figure 38 – Runaway curves for a six-nozzle Pelton turbine . 118
Figure 39 – Runaway speed determined by extrapolation . 118
Figure 40 – Measured hydraulic efficiency compared to guarantee point . 123
Figure 41 – Comparison between guarantees and measurements . 124

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Figure 42 – Pelton turbine runaway speed and discharge curves: comparison between
guarantees and measurements . 125
Figure 43 – Pelton needle force factor as a function of relative needle stroke . 130
Figure 44 – Example of pressure tap location for index test . 134
Figure 45 – Example of graphical representation of index test data . 134
Figure D.1 – Determination of the maximum runaway speed of the prototype taking into
account the friction and windage losses of the unit . 150
Figure E.1 – Principle of the method of separate segments . 152
Figure E.2 – Example of determination of intervals . 152
Figure G.1 – Influence of Froude number . 161
Figure G.2 – Influence of Weber number. 162
Figure G.3 – Influence of Reynolds number . 162
Figure I.1 – Turbine . 167

Table 1 – Coefficients of the Herbst and Roegener formula . 29
Table 2 – Permissible maximum deviations . 43
Table 3 – Maximum recommended prototype surface roughness Ra . 46
Table 4 – Summary of errors that determine total measurement uncertainty . 71
Table 5 – Examples of experimental setup of liquid column manometers . 85
Table 6 – Nomenclature for Figure 28 to Figure 33 . 96
Table 7 – Similitude numbers . 110
Table 8 – Similitude requirements for various types of model tests . 111
Table 9 – Minimum values for model size and test parameters . 113
Table 10 – Variables defining the operating point of a machine . 114
Table A.1 – Dimensionless terms . 137
−2
Table B.1 – Acceleration due to gravity g (m·s ) . 138
−3
Table B.2 – Density of distilled water ρ (kg·m ) . 139
wd
2 −1
Table B.3 – Kinematic viscosity of distilled water ν (m ·s ) . 141
Table B.4 – Vapour pressure of distilled water p (Pa) . 142
va
−3
Table B.5 – Density of dry air ρ (kg·m ) . 143
a
Table B.6 – Ambient pressure p (Pa) . 144
amb
−3
Table B.7 – Density of mercury ρ (kg·m ) . 145
Hg
Table G.1 – Numerical data for surface tension σ* . 161
Table H.1 – Confidence levels . 164
Table H.2 – Values of Student's t . 165
Table H.3 – Computation of the estimated standard deviation and the uncertainty for
eight observations . 166

IEC 63461:2024 © IEC 2024 – 9 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PELTON HYDRAULIC TURBINES –
MODEL ACCEPTANCE TESTS
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote inter
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