prEN IEC 60034-33:2026

• Status: Not Published
• Publication Date: 02-Mar-2028
• ICS: 29.160.01 - Rotating machinery in general
• ICS: 29.160.20 - Generators
• Technical Committee: CLC/TC 2 - Rotating machinery
• Current Stage: 4020 - Enquiry circulated - Enquiry
• Start Date: 07-Aug-2026
• Due Date: 17-Jun-2026
• Completion Date: 07-Aug-2026
• Ref Project: oSIST prEN IEC 60034-33:2026 - Rotating electrical machines - Part 33: Synchronous hydrogenerators including motor-generators - Specific requirements

• Revises: EN IEC 60034-33:2022 - Rotating electrical machines - Part 33: Synchronous hydrogenerators including motor-generators - Specific requirements
• Effective Date: 09-Jun-2026

prEN IEC 60034-33:2026 is the IEC/CENELEC document for synchronous hydrogenerators, including motor-generators, used with hydraulic turbines and pump-turbines. It gives specific requirements for ratings, operating conditions, temperature rise, insulation, mechanical design, cooling, tests, marking and condition monitoring so manufacturers, purchasers and test teams can use the same technical basis. It supplements IEC 60034-1 for three-phase salient-pole machines with rated frequency of 50 Hz or 60 Hz, rated output of 10 MVA and above, pole pair number 3 and above, and rated voltage of 6 kV and above.

What does prEN IEC 60034-33:2026 specify?

prEN IEC 60034-33:2026 specifies the additional requirements for synchronous hydrogenerators and synchronous motor-generators beyond the general rules for rotating electrical machines. The document is organized as clauses on site conditions, ratings, temperature, operating performance, insulation, mechanical structure, vibration, noise, cooling, protection and control instrumentation, condition monitoring, marking, and factory and site tests.

It is written for machines that must operate in power generation and pumped-storage duty, where grid conditions, hydraulic duty and machine thermal limits all matter together. In practice, that means the standard helps project teams define the machine envelope before procurement, then verify it during manufacture, installation and commissioning.

Annex	What it covers
Annex A	Special tools
Annex B	Correction of measured windage losses on the machines
Annex C	Correction of measured bearing losses for different oil bath temperatures
Annex D	Scope of supply
Annex E	Test run and guaranteed period
Annex F	Test items
Annex G	Condition monitoring

What are the key requirements of prEN IEC 60034-33:2026?

prEN IEC 60034-33:2026 is mainly about defining how a hydro machine is rated, how it may be operated, and how its thermal, electrical and mechanical capability is verified. The most important requirements are spread across Clauses 4 to 17, with Annexes B, C, E, F and G adding methods and test programs.

Site conditions and operating envelope

Clause 4 sets the default site conditions for continuous rated operation. The machine is expected to run at rated output, voltage, frequency and power factor within limits for altitude, cooling-air temperature, water temperature, humidity, covered powerhouse installation and seismic design, with any different site condition agreed between purchaser and manufacturer. For direct water-cooled stator windings, the inlet water quality is also defined by temperature, conductivity, pH and hardness, so the cooling system and water treatment can be designed correctly.

Clause 5 then fixes the machine’s operating envelope. It covers output ratings, rated voltage, rated power factor, rated speed, P-Q capability, voltage and frequency variation during operation, efficiency and losses, electrical parameters, reactances, THD and torques. The P-Q capability diagram is especially useful in practice because it shows where stator current, field current, end-region heating, minimum excitation and the reluctance circle limit operation.

Temperature, insulation and electrical connections

Clause 6 ties temperature rise limits to the insulation thermal class and to the way temperatures are measured. The standard uses embedded temperature detectors (ETDs) in the stator winding and stator core, with sensor number and placement depending on core length and ventilation arrangement. That matters because the guarantee value is based on the highest relevant sensor reading, not on an average that could hide a hot spot.

Clause 7 covers the machine’s electrical behavior in service. It addresses stator and rotor excess current, continuous and short-time unbalanced load, mechanical output overload, sudden short circuit, synchronization, load application, starting of motor-generator units, system earthing, neutral point leads, rotating direction and phase sequence, and stator winding arrangement. The document also lists accepted motor-generator starting methods, including static frequency converter (SFC) starting and back to back starting, which helps the purchaser match the machine to the plant starting philosophy.

Clause 8 deals with winding insulation performance and test methods. It covers insulation resistance, dielectric dissipation factor, partial discharge, voltage withstand tests for different winding stages, breakdown test, voltage endurance test, thermal cycle test and tests for stator winding terminals. In practice, this is the part that supports insulation qualification, factory acceptance and any agreement on long-life endurance testing.

Mechanical design, vibration, noise and cooling

Clause 9 sets the mechanical design basis for rotating parts and load cases. It covers moment of inertia, maximum speed, structural strength under normal operation and fault cases, critical bending speed, start-stop duty, overspeed and fatigue verification. That matters for hydro units because the machine must survive load rejection, sudden short circuit and other rare but severe events without harmful damage.

Clause 10 separates low-frequency and high-frequency core vibration, while Clause 11 sets how noise is measured and reported for vertical, horizontal and bulb-type machines. Clauses 12 and 13 then cover the basic structural layout, bearings, shaft currents, structure tolerances, and the ventilation and cooling system, including redundancy in coolers and fans. If multiple coolers or fans fail, the machine must still operate at rated output within a limited temperature increase, so the cooling concept cannot rely on a single point of failure.

Protection, monitoring, marking and tests

Clauses 14 and 15 cover instrumentation for protection, control and condition monitoring. The document points to stator and bearing temperature, bearing vibration, shaft displacement, air gap distance, core and frame vibration, end winding vibration, partial discharge and field winding magnetic flux as useful monitored quantities. That helps operators plan maintenance before a fault develops.

Clause 16 defines the marking that must appear on the nameplate, including identity, ratings, speed, inertia, winding connection, thermal class and commissioning year, with an extra plate for refurbished machines whose rated parameters change. Clause 17 covers factory and site tests, and Annex E adds the test run and guaranteed period, including the 72 h test run and the 15-day examination test run for motor-generators.

What terms does prEN IEC 60034-33:2026 define?

• Hydrogenerator - A synchronous machine operated as a generator and driven by a hydraulic turbine.
• Motor-generator - A synchronous machine that can run in both motor mode and generator mode, typically in pumped-storage plants.
• Embedded temperature detector (ETD) - A temperature sensor installed in or on the machine to measure winding, core or bearing temperature at defined points.
• Total harmonic distortion (THD) - The harmonic distortion of the line-to-line voltage, used here to judge generator voltage quality under open-circuit conditions.
• Static frequency converter (SFC) starting - A starting method that brings a synchronous machine to speed in motor mode using a variable-frequency supply from an SFC.
• Back to back starting - A synchronous starting method where one machine starts another connected machine.

Who uses prEN IEC 60034-33:2026?

prEN IEC 60034-33:2026 is used by hydrogenerator and motor-generator manufacturers, turbine-generator package suppliers, project engineers, purchasers, quality managers, commissioning teams and test laboratories. They use it to agree the machine’s ratings, specify cooling and insulation systems, define test programs, set acceptance limits for temperature, vibration and noise, and prepare nameplate and documentation data.

It is also relevant to operators and asset managers in hydropower and pumped-storage plants. For them, the condition-monitoring clauses and the guidance on operational limits help with maintenance planning, fault detection and life management.

What changed in prEN IEC 60034-33:2026 from the previous edition?

prEN IEC 60034-33:2026 states that it is the second edition and that it cancels and replaces IEC 60034-33:2022. It is identified as a technical revision.

Which standards are used with prEN IEC 60034-33:2026?

Referenced standard(s)	What they contribute
IEC 60034-1	General rating and performance rules for rotating electrical machines
IEC 60034-2-1, IEC 60034-2-2	Methods for determining losses and efficiency
IEC 60034-4-1	Methods for determining electrically excited synchronous machine quantities from tests
IEC 60034-15, IEC 60034-18-1, IEC 60034-18-32, IEC 60034-27-1, IEC 60034-27-3, IEC 60034-27-4	Insulation system evaluation, impulse withstand, partial discharge, dissipation factor and insulation resistance
IEC 60050-411, IEC 60417, IEC 60445, IEC 60085	Vocabulary, graphical symbols, terminal identification and thermal evaluation
IEC 63132-1, IEC 63132-2	Installation procedures and tolerances for hydroelectric machines
ISO 20816-1, ISO 20816-5, ISO 7919-5, ISO 10816-5	Vibration measurement and evaluation for hydraulic generating and pumping plants
IEC 60060-1, IEC 60287-3-1, EN 50522, IEEE Std 1043, IEEE Std 1310, IEEE Std 1553	High-voltage test definitions, earthing, and voltage-endurance or thermal-cycle test practice

What does the prEN IEC 60034-33:2026 document contain?

prEN IEC 60034-33:2026 contains preferred-speed tables, temperature-rise limits, grounding-connector material data, vibration limits, sensor-location tables and a nameplate marking list. It also includes figures for the P-Q capability diagram, the voltage and frequency operating zones, and the noise measuring positions.

The annexes add practical detail for project work. Annex B and Annex C give correction methods for windage losses and bearing losses, Annex E defines the test run and guaranteed period, Annex F lists factory, site, startup and performance test items, and Annex G describes condition-monitoring options such as air gap, vibration, partial discharge and air-gap magnetic flux.

SLOVENSKI STANDARD
01-oktober-2026
Električni rotacijski stroji - 33. del: Sinhronski hidrogeneratorji, vključno z motor-
generatorji - Posebne zahteve
Rotating electrical machines - Part 33: Synchronous hydrogenerators including motor-
generators - Specific requirements
Drehende elektrische Maschinen - Teil 33: Besondere Anforderungen an
Synchrongeneratoren, angetrieben durch hydraulische Turbinen, einschließlich Motor-
Generatoren
Machines électriques tournantes - Partie 33: Hydro-génératrices synchrones y compris
les groupes moteur-générateurs - Exigences spécifiques
Ta slovenski standard je istoveten z: prEN IEC 60034-33:2026
ICS:
29.160.20 Generatorji Generators
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

2/2319/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 60034-33 ED2
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2026-08-07 2026-10-30
SUPERSEDES DOCUMENTS:
2/2317/RR
IEC TC 2 : ROTATING MACHINERY
SECRETARIAT: SECRETARY:
United Kingdom Mr Charles Whitlock
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:
Rotating electrical machines - Part 33: Synchronous hydrogenerators including motor-
generators - Specific requirements

PROPOSED STABILITY DATE: 2028
NOTE FROM TC/SC OFFICERS:
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
permission in writing from IEC.

IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

Link to Committee Draft for Vote (CDV) online document:
Click here
How to access
This link leads you to the Online Standards Development (OSD) platform for National Mirror
Committee’s (NMC) comments. The project draft may be found further down this document.

Resource materials
We recommend NCs to review the available materials to better understand the member commenting
on the OSD platform. This includes the:
• OSD NC roles overview
• How to add and submit comments to the IEC

Contact
Should you require any assistance, please contact the IEC IT Helpdesk.

IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

CONTENTS
CONTENTS . 1
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Site operation conditions . 11
5 Ratings and parameters . 11
5.1 Output . 11
5.1.1 Output rating of a hydrogenerator . 11
5.1.2 Output ratings of a motor-generator . 11
5.1.3 Increase in active power . 11
5.1.4 Under-excited operation . 12
5.2 Rated voltage . 12
5.3 Rated power factor . 12
5.4 Rated speed . 12
5.5 P-Q capability diagram . 12
5.6 Voltage and frequency variations during operation . 13
5.7 Efficiency and losses . 15
5.7.1 Weighted average efficiency . 15
5.7.2 Losses . 15
5.7.3 Determination of winding losses . 16
5.7.4 Windage Losses . 16
5.7.5 Determination of thrust bearing losses for vertical machines . 16
5.7.6 Tolerance of the total losses . 17
5.8 Electrical parameters and time constants . 17
5.8.1 Short-circuit ratio . 17
5.8.2 Direct axis transient and subtransient reactances . 17
5.8.3 General case . 18
5.9 Tolerances on reactance . 18
5.10 Total harmonic distortion (THD) . 18
5.11 Torques . 19
6 Temperature . 19
6.1 Temperature rise . 19
6.2 Measurements for the stator winding . 20
6.3 Measurements for the stator core . 20
6.4 Correction due to deviation from reference operation . 21
6.5 Bearing temperature . 21
7 Operating performances and electrical connections . 21
7.1 Special operational requirements . 21
7.1.1 Stator excess current . 21
7.1.2 Rotor excess current . 22
7.1.3 Continuous unbalanced load . 22
7.1.4 Short time unbalanced load . 22
7.1.5 Mechanical output overload . 23
IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

7.1.6 Sudden short circuit . 23
7.2 Connection to grid . 23
7.2.1 Synchronization . 23
7.2.2 Application of load . 24
7.3 Starting of motor-generator . 24
7.4 System earthing . 24
7.5 Neutral point leads . 25
7.6 Rotating direction and phase sequence. 25
7.7 Stator winding . 26
8 Winding insulation . 26
8.1 Winding insulation performance . 26
8.1.1 General . 26
8.1.2 Winding insulation resistance . 26
8.1.3 Dielectric dissipation factor measurements on new stator bars or coils . 27
8.1.4 Partial discharge measurements for stator winding . 27
8.1.5 Voltage withstand test for turn insulation of multi-turn coil for stator . 27
8.1.6 Quality inspection for Roebel bars . 27
8.2 Voltage withstand tests . 27
8.2.1 Stator bars/coils . 27
8.2.2 Inserted stator bars/coils . 28
8.2.3 Stator winding completed before rotor inserted . 28
8.2.4 Field winding before delivery . 28
8.2.5 Field winding completed . 28
8.2.6 Stator winding for completed machine . 29
8.2.7 Field winding for completed machine . 29
8.2.8 DC alternative tests . 29
8.2.9 Global VPI stators . 29
8.3 Breakdown test for insulation . 29
8.4 Voltage endurance test for insulation . 29
8.5 Thermal cycle test . 30
8.6 Stator winding terminals . 30
9 Mechanical structural performances and design . 30
9.1 Rotating part mass moment of inertia . 30
9.2 Maximum speed . 31
9.3 Structural strength . 31
9.4 Critical bending speed . 32
9.5 Start and stop of motor-generators. 32
9.6 Start and stop of hydrogenerators . 32
9.7 Over speed . 32
9.8 Fatigue verification . 32
10 Core vibration . 32
11 Noise . 33
12 Basic structural requirements . 34
12.1 General layout . 34
12.1.1 Structure and general layout of the machines . 34
12.1.2 Machine components . 34
12.1.3 Hydraulic or pneumatic braking system . 34
12.1.4 Hydraulic jacking system . 34
IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

12.1.5 Dynamical (electrical) braking . 34
12.2 Stator . 35
12.2.1 Frame and core structure. 35
12.2.2 Stator frame connecting structure . 35
12.2.3 Stator end winding . 35
12.3 Rotor . 35
12.3.1 Damper winding . 35
12.3.2 Structure with one shaft or segmented shafts . 35
12.4 Structure tolerance . 35
12.5 Bearings . 36
12.5.1 Bearing alloy . 36
12.5.2 Bearing lubricant . 36
12.5.3 Shaft currents . 36
12.5.4 Bearing insulation resistance . 36
13 Ventilation and cooling system . 36
13.1 Cooling scheme . 36
13.1.1 General . 36
13.1.2 Air cooling system . 36
13.1.3 Evaporative cooling system . 37
13.1.4 Water cooling system . 37
13.2 Redundancy on the design of coolers and motor fans . 37
13.3 Cooling structure . 37
13.3.1 Materials . 37
13.3.2 Water supply and drainage . 37
13.3.3 Cooling water pressure . 37
14 Instrumentation required for protection and control . 37
14.1 General . 37
14.2 Stator and bearing temperature . 38
14.3 Bearing vibration and shaft displacement . 38
15 Instrumentation for condition monitoring of machines . 39
15.1 General . 39
15.2 Instrumentation required for condition monitoring . 39
16 Marking . 39
16.1 Information to be marked on machine nameplate: . 39
16.2 Repaired or refurbished machines . 40
17 Factory and site tests . 40
Annex A (informative) Special tools . 41
Annex B (informative) Correction of measured windage losses on the machines . 42
Annex C (informative) Correction of measured bearing losses for different oil bath
temperatures . 44
Annex D (informative) Scope of supply . 46
Annex E (normative) Test run and guaranteed period . 47
E.1 72 h test run . 47
E.2 15-day examination test run for motor-generators . 47
E.3 Handover and guarantee period . 47
Annex F (informative) Test items . 48
F.1 Inspection test for hydrogenerator and motor-generator in factory . 48
IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

F.2 Site routine test of hydrogenerator and motor-generator . 48
F.3 Startup test run of hydrogenerator and motor-generator . 49
F.4 Performance test of hydrogenerator . 49
Annex G (informative) Condition monitoring . 50
G.1 Air gap distance . 50
G.2 Core and frame vibration. 50
G.3 Stator end winding vibration . 50
G.4 Partial discharge . 50
G.5 Air gap magnetic flux . 51
G.6 Others . 51
Bibliography . 52

Figure 1 – P-Q capability in p. u. . 13
Figure 2 – Voltage and frequency limits for hydro machines . 14
Figure 3 – Location of measuring points in the horizontal plane . 33

Table 1 – Preferred speed for 50 Hz machines - Unit: 1/min . 12
Table 2 – Preferred speed for 60 Hz machines - Unit: 1/min . 12
Table 3 – Reference temperature . 16
Table 4 – Temperature rise limits for machine’s main part . 19
Table 5 – Temperature rise limits for collector ring . 19
Table 6 – Permitted excess current multiple vs. time duration . 22
Table 7 – Permitted negative phase sequence current for the machines . 22
Table 8 – Permitted negative phase sequence current for the machines . 23
Table 9 – Material properties for grounding connectors . 25
Table 10 – Test voltage for insulating resistance measurement . 27
Table 11 – Dielectric dissipation factor . 27
Table 12 – Testing values for voltage withstand test of field winding . 29
Table 13 – Limits for vibration in the core . 33
Table 14 – Temperature sensor locations . 38
Table A.1 – Special tools . 41

IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Rotating electrical machines -
Part 33: Synchronous hydrogenerators including motor-generators -
Specific requirements
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 international co-operation on all questions concerning
standardization in the electrical and electronic fields. To this end and in addition to other
activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC
Publication(s)"). Their preparation is entrusted to technical committees; any IEC National
Committee interested in the subject dealt with may participate in this preparatory work.
International, governmental and non-governmental organizations liaising with the IEC also
participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as
possible, an international consensus of opinion on the relevant subjects since each technical
committee has representation from all interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted
by IEC National Committees in that sense. While all reasonable efforts are made to ensure that
the technical content of IEC Publications is accurate, IEC cannot be held responsible for the
way in which they are used or for any misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC
Publications transparently to the maximum extent possible in their national and regional
publications. Any divergence between any IEC Publication and the corresponding national or
regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies
provide conformity assessment services and, in some areas, access to IEC marks of conformity.
IEC is not responsible for any services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including
individual experts and members of its technical committees and IEC National Committees for
any personal injury, property damage or other damage of any nature whatsoever, whether direct
or indirect, or for costs (including legal fees) and expenses arising out of the publication, use
of, or reliance upon, this IEC Publication or any other IEC Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced
publications is indispensable for the correct application of this publication.
9) IEC draws attention to the possibility that the implementation of this document may involve
the use of (a) patent(s). IEC takes no position concerning the evidence, validity or applicability
of any claimed patent rights in respect thereof. As of the date of publication of this document,
IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

IEC [had/had not] received notice of (a) patent(s), which may be required to implement this
document. However, implementers are cautioned that this may not represent the latest
information, which may be obtained from the patent database available at https://patents.iec.ch.
IEC shall not be held responsible for identifying any or all such patent rights.
IEC 60034-33 has been prepared by IEC technical committee 2: Rotating machinery. It is an
International Standard.
This second edition cancels and replaces the first edition published in 2022. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) .;
The text of this International Standard is based on the following documents:
Draft Report on voting
2/XX/FDIS 2/XX/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 60034 series, published under the general title Rotating electrical
machines, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
– reconfirmed,
– withdrawn, or
– revised.
IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

INTRODUCTION
IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

1 Scope
This part of IEC 60034 applies to three-phase salient-pole synchronous generators and
synchronous motor-generators for hydraulic turbine and pump-turbine applications, that have
rated frequency of 50 Hz or 60 Hz, rated output of 10 MVA and above, pole pair number 3 and
above, and rated voltage of 6 kV and above.
This document supplements basic requirements for rotating machines given in IEC 60034-1.
2 Normative references
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.
IEC 60034-1, Rotating electrical machines - Part 1: Rating and performance
IEC 60034-2-1, Rotating electrical machines - Part 2-1: Standard methods for determining
losses and efficiency from tests (excluding machines for traction vehicles)
IEC 60034-2-2, Rotating electrical machines - Part 2-2: Specific methods for determining
separate losses of large machines from tests - Supplement to IEC 60034-2-1
IEC 60034-4-1, Rotating electrical machines - Part 4-1: Methods for determining electrically
excited synchronous machine quantities from tests
IEC 60034-15, Rotating electrical machines - Part 15: Impulse voltage withstand levels of form-
wound stator coils for rotating a.c. machines
IEC 60034-18-1, Rotating electrical machines - Part 18-1: Functional evaluation of insulation
systems - General guidelines
IEC 60034-18-32, Rotating electrical machines - Part 18-32: Functional evaluation of insulation
systems - Electrical endurance qualification procedures for form-wound windings
IEC 60034-27-1, Rotating electrical machines - Part 27-1: Off-line partial discharge
measurements on the stator winding insulation of rotating electrical machines
IEC 60034-27-3, Rotating electrical machines - Part 27-3: Dielectric dissipation factor
measurement on stator winding insulation of rotating electrical machines
IEC 60034-27-4, Rotating electrical machines - Part 27-4: Measurement of insulation resistance
and polarization index of winding insulation of rotating electrical machines
IEC 60034-33:2022, Rotating electrical machines - Part 33: Synchronous hydrogenerators
including motor-generators - Specific requirements
IEC 60050-411, International Electrotechnical Vocabulary - Chapter 411: Rotating Machines
IEC 60060-1, High-voltage test techniques - Part 1: General definitions and test requirements
IEC 60085, Electrical insulation - Thermal evaluation and designation
IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

IEC 60287-3-1:2017, Electric cables - Calculation of the current rating - Part 3-1: Operating
conditions - Site reference conditions
IEC 60417, Graphical symbols for use on equipment - 12-month subscription to regularly
updated online database comprising all graphical symbols published in IEC 60417
IEC 60445, Basic and safety principles for man-machine interface, marking and identification -
Identification of equipment terminals, conductor terminations and conductors
IEC 63132-1, Guide for installation procedures and tolerances of hydroelectric machines - Part
1: Common
IEC 63132-2, Guide for installation procedures and tolerances of hydroelectric machines - Part
2: Vertical generator
ISO 7919-5:2005, Mechanical vibration — Evaluation of machine vibration by measurements
on rotating shafts — Part 5: Machine sets in hydraulic power generating and pumping plants
ISO 10816-5:2000, Mechanical vibration — Evaluation of machine vibration by measurements
on non-rotating parts — Part 5: Machine sets in hydraulic power generating and pumping plants
ISO 20816-1, Mechanical vibration - Measurement and evaluation of machine vibration - Part
1: General Guidelines
ISO 20816-5, Mechanical vibration - Measurement and evaluation of machine vibration - Part
5: Machine sets in hydraulic power generating and pump-storage plants
IEEE Std 1043: 1996, IEEE Recommended practice for voltage-endurance testing of form-
wound bars and coils
IEEE Std 1310: 2012, IEEE Recommended practice for thermal cycle for voltage-endurance
testing of form-wound bars and coils for large rotating machines
IEEE Std 1553: 2002, IEEE Trial-use standard for voltage-endurance testing of form-wound
coils and bars for hydrogenerators
EN 50522: 2010, Earthing of power installations exceeding 1 kV a.c.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60034-1, IEC 60034-
2-1, IEC 60034-2-2, IEC 60050-411 and IEC 63132-1, as well as the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– IEC Electropedia: available at https://www.electropedia.org/
– ISO Online browsing platform: available at https://www.iso.org/obp
3.1
hydrogenerator
synchronous machine operated as generator and driven by a hydraulic turbine
IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

3.2
motor-generator
synchronous machine which can operate in motor mode and generator mode, generally used in
pumped-storage power plant
3.3
stator concentricity
radial distance from the reference centre to the best centre of stator bore
3.4
rotor concentricity
radial distance from the reference centre to the best centre of rotor outer circle
3.5
stator circularity
difference between the maximum and minimum radii, measured from the best centre of stator
bore
3.6
rotor circularity
difference between the maximum and minimum radii, measured from the best centre of rotor
outer circle
3.7
Air gap
3.7.1
nominal air gap
design air gap value between stator inner surface and rotor at the centre of poleshoe at rated
conditions
3.7.2
static air gap
air gap at standstill and in cold condition after full load rejection
Note 1 to entry: This value is used for the purposes of IEC 63132-1 and IEC 63132-2.
3.8
stress control coating
paint or tape on the surface of the main insulation that extends beyond the conductive slot
portion coating in high-voltage stator bars and coils
3.9
condenser
heat exchanger device by which cooling medium is changed to liquid phase from vapour in
evaporative cooling circulation system
3.10
grid
public electrical network or a local (e.g. industrial) network which is connected to the machine
either directly or through a transformer
3.11
SFC starting
operating mode in which synchronous machine is started in motor mode by the method of
regulating power frequency, using static frequency converter (SFC) as variable-frequency
power supply
IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

3.12
back to back starting
synchronous starting method in which one machine is started in motor mode, driven by the
other electric connected machine that is started in generator mode
4 Site operation conditions
The machines shall be able to operate continuously at rated conditions (MVA, MW, voltage,
frequency and power factor) at the following site operation conditions:
a) The altitude does not exceed 1 000 m above sea level (based on coupling elevation for
vertical machine, centre line of shaft for horizontal machine);
b) The cooling air temperature (primary coolant) does not exceed 40 °C;
c) The inlet water temperature (secondary coolant) of air coolers, oil coolers and heat
exchangers (e.g. of direct water cooled stator windings) is not higher than 25 °C and not
less than 5 °C;
d) The inlet water temperature (primary coolant) of direct water cooled stator windings shall
be 30 °C to 40 °C, the water conductivity is in the range of 0,4 μS/cm to 2,0 μS/cm, the pH
value is 6,5 to 9,0, and the hardness is less than 2 μmol/l, at 25 °C of water temperature;
e) Relative humidity in powerhouse (generator floor) does not exceed 85 %;
f) Installed in covered powerhouse on proper foundation;
g) Structural strength of machine shall meet the requirement of seismic accelerations at the
location. Appropriate design measures shall be taken to prevent harmful damage to the
machine. The acceleration value may be different for different regions due to the local
geographical condition. The acceleration values in horizontal direction and vertical direction
shall be defined as a technical condition according to the seismic grade at the location by
the purchaser.
Site conditions different from the above shall be agreed between purchaser and manufacturer.
5 Ratings and parameters
5.1 Output
5.1.1 Output rating of a hydrogenerator
The output rating of a hydrogenerator preferable is the apparent power (in MVA) or the active
power (in MW), available continuously at the stator terminals (main leads) at rated frequency,
voltage and power factor.
5.1.2 Output ratings of a motor-generator
The output ratings of a motor-generator include two parts:
a) The apparent power (in MVA) or the active power (in MW), available continuously at the
stator terminals (main leads) at rated frequency, voltage and power factor during generator
mode;
b) Mechanical output power (in MW) available continuously at the shaft during motor mode.
5.1.3 Increase in active power
By agreement between purchaser and manufacturer, it is allowed to increase active power of
hydrogenerators to rated output (apparent power) by increasing power factor up to 1,0.
IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

5.1.4 Under-excited operation
Hydrogenerators and motor-generators when operating in generator mode shall be able to
operate continuously in under-excited mode at power factor 0,9 with rated active power at rated
voltage.
5.2 Rated voltage
The rated voltage (line to line voltage U at stator terminals) of the machine shall be defined by
N
purchaser and manufacturer according to rated output, rated speed of machine, as well as other
conditions in the system.
5.3 Rated power factor
The power factor shall be agreed upon between purchaser and manufacturer. Preferred rated
power factors at generator terminals are 0,85; 0,875; 0,9; 0,925 or 0,95 overexcited.
Rated power factor of motor-generators in motor mode shall be defined as a design condition
by purchaser.
5.4 Rated speed
The rated speed (1/min) shall be:
3000/ p for 50 Hz machines;
3000/ p for 60 Hz machines.
where p is the number of pole pairs.
NOTE The preferred speeds in Table 1 and Table 2 are convenient to design electrical symmetric and balanced
windings for the machines.
Table 1 – Preferred speed for 50 Hz machines - Unit: 1/min
1 000 750 600 500 428,6 375 333,3 300 250
214,3 200 187,5 166,7 150 142,9 136,4 125 115,4
107,1 100 93,8 88,2 83,3 75 71,4 68,2 62,5
Table 2 – Preferred speed for 60 Hz machines - Unit: 1/min
1 200 900 720 600 514,3 450 400 360 300
257,1 240 225 200 180 171,5 163,7 150 138,5
128,5 120 112,6 105,8 100 90 85,7 81,8 75
5.5 P-Q capability diagram
The manufacturer shall supply a P-Q capability diagram indicating the limits of operation as
shown in Figure 1, where:
Curve A represents operation limits with rated stator current and constant apparent power
output, which is restricted by temperature rise of the stator winding;
IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

Curve B represents operation limits with rated field current, which is restricted by temperature
rise of the field winding;
Curve C1 and C2 indicates the theoretical and practical limits set by the effects of end region
heating, steady-state stability, etc.
Curve D indicates the limits of minimum excitation current to prevent instability issues (usually
defined by a minimum excitation current of 10 % of the no-load excitation current).
Curve E indicates the reluctance circle. Although possible, the operation within the reluctance
circle needs special care and a special design of the excitation and control systems.

Figure 1 – P-Q capability in p. u.
NOTE Figure 1 shows the limitation of the electrical machine only and does not consider operational limitation of
the hydraulic machine.
5.6 Voltage and frequency variations during operation
For generators and motor-generators, combinations of steady state voltage variation and
frequency variation are classified as being either zone A or zone B (maximum case outside of
zone A), in accordance with Figure 2.
Synchronous hydrogenerators and synchronous motor-generators shall be capable of deliver
continuous rated output at the rated power factor, over the ranges of ±5 % in voltage and ±2 %
in frequency, as defined by the shaded area of Figure 2 (zone A), but need not fully comply with
its performance at rated voltage and frequency (see rated point in Figure 2), and may exhibit
some deviations. Temperature rises may be higher than the condition for rated voltage and
frequency.
The temperature rise or temperature limits in accordance with this document, such as Table 4
and Table 5, apply at the rated point only and may progressively be exceeded as the operating
point moves away from the rated point. For conditions at the extreme boundaries of zone A, the
temperature rises, and temperature typically exceed the limits specified in this document.
IEC 60034-33 ED2 © IEC 2026 2/2319/CDV

A machine shall be capable of operation within zone B, and reaching the rated output, but will
exhibit greater deviations from its performance at rated voltage and frequency than in zone A.
Temperature rises will be higher than at rated voltage and frequency and most likely will be
higher than those in zone A. Temperature limits for insulation systems may be exceeded.
Extended operation at the perimeter of zone B is not recommended at all.
Excursions into zone B shall be limited in value, duration no longer than 10 minutes, recurrence
not below 6 hours and frequency of occurrence no higher than 2 times per month. Requiring
permanent operation in zone B without negative impact on lifetime will inevitably lead to a non-
economical design and can require a volume increase of the machine in the range of 10% or
more.
For other conditions of duration, recurrence and frequency of occurrence, corrective measures
should be taken where practical, within a reasonable time if possible, for example, a reduction
in output (reactive or active po
...