IEC 60034-3:2007

IEC 60034-3
Edition 6.0 2007-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Rotating electrical machines –
Part 3: Specific requirements for synchronous generators driven by steam
turbines or combustion gas turbines

Machines électriques tournantes –
Partie 3: Règles spécifiques pour les alternateurs synchrones entraînés par
turbines à vapeur ou par turbines à gaz à combustion

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IEC 60034-3
Edition 6.0 2007-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Rotating electrical machines –
Part 3: Specific requirements for synchronous generators driven by steam
turbines or combustion gas turbines

Machines électriques tournantes –
Partie 3: Règles spécifiques pour les alternateurs synchrones entraînés par
turbines à vapeur ou par turbines à gaz à combustion

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
U
CODE PRIX
ICS 29.160 ISBN 2-8318-9371-2
– 2 – 60034-3 © IEC:2007
CONTENTS
FOREWORD.4

1 Scope.6
2 Normative references .6
3 Terms and definitions .6
4 General .7
4.1 General rules .7
4.2 Rated conditions .7
4.3 Rated voltage.7
4.4 Power factor.7
4.5 Rated speed.7
4.6 Ranges of voltage and frequency .8
4.7 Direction of rotation.8
4.8 Stator winding .9
4.9 Generator rated field current and voltage .9
4.10 Winding insulation .9
4.10.1 Thermal class .9
4.10.2 Withstand voltage tests .9
4.11 Insulation against shaft current.9
4.12 Over-speed test.9
4.13 Critical speeds .9
4.14 P-Q capability diagram .9
4.15 Overcurrent requirements.11
4.16 Sudden short circuit .11
4.17 Short-circuit ratio.12
4.18 Direct axis transient and subtransient reactances for generators .12
4.19 Tolerances on short-circuit ratio and direct axis transient and subtransient
reactances .12
4.20 Mechanical conditions for rotors .12
4.20.1 Number of starts.12
4.20.2 Turning gear operation .12
4.21 Coolers .13
5 Air-cooled generators .13
5.1 General .13
5.2 Generator cooling.13
5.3 Temperature of primary coolant.13
5.3.1 Temperature detectors .14
6 Hydrogen-cooled or liquid-cooled generators.14
6.1 General .14
6.2 Hydrogen pressure and purity in the casing.14
6.3 Generator housing and cover plates .14
6.4 Stator winding terminals .14
6.5 Temperature of primary coolants, temperatures and temperature rises of the
generator .14
6.6 Temperature detectors .15
6.7 Auxiliary system .15

60034-3 © IEC:2007 – 3 –
7 Generators for combustion gas turbines or combined cycle applications.16
7.1 General .16
7.2 Service conditions .16
7.2.1 General .16
7.2.2 Primary coolant temperature.16
7.2.3 Number of starts.16
7.2.4 Application of load .16
7.3 Rated output .16
7.4 Capabilities .17
7.4.1 General .17
7.4.2 Base capability .17
7.4.3 Temperature rise and temperature at base capability.18
7.4.4 Peak capability .19
7.5 Rating plate.19
7.6 Temperature tests .19

Annex A (normative) Precautions to be taken when using hydrogen cooled turbine-
driven synchronous generators .20

Bibliography.27

Figure 1 – Operation over ranges of voltage and frequency .8
Figure 2 – Typical P-Q capability diagram.10
Figure 3 – Typical generator capability curves .18
Figure A.1 – Example of a large hydrogen supply unit feeding one or more generators
(simplified diagram) .26

– 4 – 60034-3 © IEC:2007
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ROTATING ELECTRICAL MACHINES –

Part 3: Specific requirements for synchronous generators
driven by steam turbines or combustion gas turbines

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,
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60034-3 has been prepared by IEC Technical Committee 2:
Rotating machinery.
This sixth edition cancels and replaces the fifth edition published in 2005. This edition
constitutes a technical revision. The significant technical changes with respect to the previous
edition are as follows:
• the contents is now restricted to synchronous generators driven by steam turbines or
combustion gas turbines, but covers as well cylindrical rotor and salient-pole generators;
• synchronous motors have been taken out of the scope of part 3.

60034-3 © IEC:2007 – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
2/1461/FDIS 2/1474/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of 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 publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – 60034-3 © IEC:2007
ROTATING ELECTRICAL MACHINES –

Part 3: Specific requirements for synchronous generators
driven by steam turbines or combustion gas turbines

1 Scope
This part of IEC 60034 applies to three-phase synchronous generators, having rated outputs
of 10 MVA and above driven by steam turbines or combustion gas turbines. It supplements
the basic requirements for rotating machines given in IEC 60034-1.
Common requirements are prescribed together with specific requirements for air, for hydrogen
or for liquid cooled synchronous generators.
This part of IEC 60034 also gives the precautions to be taken when using hydrogen cooled
generators including:
– rotating exciters driven by synchronous generators;
– auxiliary equipment needed for operating the generators;
– parts of the building where hydrogen might accumulate.
NOTE 1 These requirements also apply to a synchronous generator driven by both a steam turbine and a
combustion gas turbine as part of a single shaft combined cycle unit.
NOTE 2 These requirements do not apply to synchronous generators driven by water (hydraulic) turbine or wind
turbine.
NOTE 3 The precautions to be taken when using hydrogen are valid for all cases where hydrogen is used as a
coolant.
2 Normative references
The following referenced documents are indispensable for the application 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 60034-4, Rotating electrical machines – Part 4: Methods for determining synchronous
machine quantities from tests
IEC 60045-1, Steam turbines – Part 1: Specifications
IEC 60079 (all parts), Electrical apparatus for explosive gas atmospheres
3 Terms and definitions
For the purposes of this document, the terms and definitions in IEC 60034-1 together with the
following additions apply.
60034-3 © IEC:2007 – 7 –
3.1
mechanical start
change in speed from zero or turning gear speed to rated speed
3.2
turning gear operation
rotation at low speed to maintain thermal equilibrium of the turbine and/or rotor
4 General
4.1 General rules
Turbine driven synchronous generators shall be in accordance with the basic requirements for
rotating machines specified in IEC 60034-1 unless otherwise specified in this standard.
Wherever in this standard there is reference to an agreement, it shall be understood that this
is an agreement between the manufacturer and the purchaser.
4.2 Rated conditions
The rated conditions are given by the rated values of
– the apparent power;
– frequency;
– voltage;
– power factor;
– primary coolant temperature (40°C unless otherwise agreed upon);
and where applicable,
– site altitude;
– hydrogen pressure;
– range of hydrogen purity, see IEC 60034-1.
4.3 Rated voltage
The rated voltage shall be fixed by agreement.
4.4 Power factor
The power factor shall be agreed upon between the purchaser and manufacturer.
Standardised rated power factors at the generator terminals are 0,8, 0,85 and 0,9 overexcited.
NOTE 1 Other values may be agreed upon, the lower the power factor the larger will be the generator.
NOTE 2 It is recommended that the generator should be capable of providing 0,95 underexcited power factor at
rated MW.
4.5 Rated speed
The rated speed shall be
–1
3 000/p min for 50 Hz generators;
–1
3 600/p min for 60 Hz generators;
where p is the number of pole pairs.

– 8 – 60034-3 © IEC:2007
4.6 Ranges of voltage and frequency
Generators shall be capable of 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 1.
The temperature rise limits in Tables 7 and 8, or the temperature limits in Table 12 of
IEC 60034-1 shall apply at the rated voltage and frequency only.
NOTE 1 As the operating point moves away from the rated values of voltage and frequency, the temperature rise
or total temperatures may progressively increase. Continuous operation at rated output at certain parts of the
boundary of the shaded area causes temperature rises to increase by up to 10 K approximately. Generators will
+3
also carry output at rated power factor within the ranges of ±5 % in voltage and % in frequency, as defined by
−5
the outer boundary of Figure 1, but temperature rises will be further increased. Therefore, to minimize the
reduction of the generator's lifetime due to the effects of temperature or temperature differences, operation outside
the shaded area should be limited in extent, duration and frequency of occurrence. The output should be reduced
or other corrective measures taken as soon as practicable.
If an operation over a still wider range of voltage or frequency or deviations from rated
frequency and voltage are required, this should be the subject of an agreement.
NOTE 2 It is considered that overvoltage together with low frequency, or low voltage with over-frequency, are
unlikely operating conditions. The former is the condition most likely to increase the temperature rise of the field
winding. Figure 1 shows operation in these quadrants restricted to conditions that will cause the generator and its
transformer to be over- or under-fluxed by no more than 5 %. Margins of excitation and of stability will be reduced
under some of the operating conditions shown. As the operating frequency moves away from the rated frequency,
effects outside the generator may become important and need to be considered. As examples: the turbine
manufacturer will specify ranges of frequency and corresponding periods during which the turbine can operate; and
the ability of auxiliary equipment to operate over a range of voltage and frequency should be considered.
V %
95 98 100 102 103 f %
IEC  082/05
Figure 1 – Operation over ranges of voltage and frequency

4.7 Direction of rotation
The direction of rotation shall be shown on the generator or on its rating plate, and the time-
phase sequence of the stator voltage shall then be indicated by marking the terminals in the
sequence in which their voltages reach maximum, for example, U , V , W .
1 1 1
NOTE Terminal markings may not be consistent with IEC 60034-8.

60034-3 © IEC:2007 – 9 –
For generators having one driving end, this shall be the reference end for the direction of
rotation.
For generators having two drive ends, the more powerful drive end shall be the reference end.
If not applicable, the end opposite to the excitation leads shall be the reference end for the
direction of rotation.
The sense of rotation (clockwise or counter-clockwise) shall be defined when facing the
generator rotor coupling from the reference side.
4.8 Stator winding
Unless otherwise agreed upon, rated generator voltage corresponds to star connection. All
winding ends shall be brought out and arranged in an agreed arrangement of the external
connections to the generator.
4.9 Generator rated field current and voltage
The generator rated field current and voltage are those values needed for the generator to
operate at rated conditions.
4.10 Winding insulation
4.10.1 Thermal class
Insulation systems used for the windings shall be of thermal class 130 or higher.
4.10.2 Withstand voltage tests
Withstand voltage tests shall be in accordance with IEC 60034-1, Table 16.
4.11 Insulation against shaft current
Suitable precautions shall be taken to prevent harmful flow of shaft current and to earth the
rotor shaft adequately. Any insulation needed shall preferably be arranged so that it can be
measured while the generator is operating. Shaft voltage spikes caused by static excitation
with controlled rectifiers shall be kept down by suitable means to non-critical values. These
spikes could cause damage, for example the bearing Babbitt by breaking through the bearing
oil film.
4.12 Over-speed test
Rotors shall be tested at 1,2 times rated speed for 2 min.
4.13 Critical speeds
Critical speeds of the combined shaft train shall not cause unsatisfactory operation within the
speed range corresponding to the frequency range agreed upon in accordance with 4.6 (see
also IEC 60045-1).
4.14 P-Q capability diagram
The manufacturer shall supply a P-Q capability diagram indicating the limits of operation. The
P-Q diagram shall be drawn for operation at rated conditions. A typical P-Q diagram is shown
in Figure 2, its boundaries are set by the following limitations:
– curve A represents operation with constant rated field current and therefore with
approximately constant temperature rise of the field winding;

– 10 – 60034-3 © IEC:2007
– curve B represents constant rated stator current and consequently approximately constant
temperature rise of the stator winding;
– curve C indicates the limit set by localized end region heating, or by steady-state stability,
or by a combination of both effects.
NOTE 1 Figure 2 may contain other operational limits such as maximum turbine limits and minimum excitation
limits.
By agreement between the manufacturer and the purchaser, other diagrams may be provided
for operation at agreed upon conditions within the voltage and frequency ranges agreed upon
in accordance with 4.6, and for cooling and temperature conditions and where applicable
hydrogen pressures other than rated.
NOTE 2 The generator should be operated within the boundaries of the diagram appropriate to the chosen
conditions of voltage, frequency and cooling, and hydrogen pressure if applicable. Operation outside these
boundaries will shorten the life of the generator.
NOTE 3 For a generator with a water cooled stator winding at reduced hydrogen pressure, the maximum water
pressure within the winding can become higher than the hydrogen pressure. Hence, in the case of a leak, water
can move from the water circuit towards the hydrogen environment within the casing. This could cause failure.

Y A
0,8
0,6 D
0,4
B
0,2
X
0,2 0,4 0,6 0,8 1,0 1,2
0,2
0,4
0,6
0,8
C
Y'
IEC  083/05
Key
A limited by field winding temperature X  per unit kW
B limited by armature winding temperature Y  per unit kvar overexcited
Y'  per unit kvar underexcited
C limited by the temperatures of the core end parts or by steady state
stability
D rated output
Figure 2 – Typical P-Q capability diagram

60034-3 © IEC:2007 – 11 –
4.15 Overcurrent requirements
Generators with rated outputs up to 1 200 MVA shall be capable of carrying, without damage,
a stator current of 1,5 per unit (p.u.) for 30 s.
For ratings greater than 1 200 MVA, agreement should be reached on a time duration less
than 30 s, decreasing as the rating increases, to a minimum of 15 s, the current remaining at
1,5 per unit for all ratings.
The generator shall be capable of other combinations of overcurrent and time that give the
same degree of additional heat above that caused by 1 p.u. current.
Thus, for generators up to 1 200 MVA,
(I – 1)t = 37,5 s
where
I is the stator current per unit (p.u.);
t is its duration in seconds.
This relationship shall apply for values of t between 10 s and 60 s.
NOTE It is recognized that stator temperatures will exceed rated load values under these conditions, and
therefore the generator construction is based upon the assumption that the number of operations to the limit
conditions specified will not exceed two per year.
4.16 Sudden short circuit
The generator shall be designed to withstand without failure a short circuit of any kind at its
terminals, while operating at rated load and 1,05 p.u. rated voltage, provided the maximum
phase current is limited by external means to a value which does not exceed the maximum
phase current obtained from a three-phase short circuit. 'Without failure' means that the
generator shall not suffer damage that causes it to trip out of service, though some
deformation of the stator winding might occur.
If it is agreed upon between purchaser and manufacturer that a sudden short-circuit test shall
be made on a new generator, it shall be done after the full voltage dielectric acceptance test
as described below.
A generator that is to be connected directly to the system shall have a 3-phase short circuit
applied at its terminals when excited to rated voltage on no-load. For a generator that will be
connected to the system through its own transformer or reactor, usually by an isolated phase
bus, the test at the terminals shall be carried out at reduced voltage, agreed upon between
the purchaser and the manufacturer, in order to produce the same stator current as would
result in service from a three-phase short circuit applied at the high voltage terminals of the
transformer.
This test shall be considered satisfactory if the generator is subsequently judged to be fit for
service without repairs or with only minor repairs to its stator windings, and if it withstands a
high-voltage test of 80 % of the value specified in IEC 60034-1 for a new generator. The term
“minor repairs” implies some attention to end-winding bracing and to applied insulation, but
not replacement of coils.
NOTE Abnormal high currents and torques can occur as a result of a short circuit close to the generator in
service, or of clearance and re-closure of a more distant fault, or of faulty synchronizing. If such conditions do
actually impose severe overcurrents, it would be prudent to examine the generator thoroughly, with particular
attention to the stator windings. Any loosening of supports or packings should be made good before returning the
generator to service, to avoid the possibility of consequential damage being caused by vibration. It may also be
desirable to check for possible shaft balance changes and deformation of the coupling bolts and couplings.

– 12 – 60034-3 © IEC:2007
4.17 Short-circuit ratio
For generators of all sizes and types of cooling covered by this standard, the value of the
short-circuit ratio shall be not less than 0,35. Higher minimum values may be specified and
agreed upon (for example by a grid demand), but, for a given cooling system, these usually
require an increase in generator size and higher losses.
4.18 Direct axis transient and subtransient reactances for generators
When the direct axis transient or subtransient reactances are specified having regard to the
operating conditions, the following values should be agreed upon:
– a minimum value of the direct axis subtransient reactance at the saturation level of rated
voltage;
– a maximum value of the direct axis transient reactance at the unsaturated conditions of
rated current.
Since the two reactances depend to a great extent on common fluxes, care should be taken to
ensure that the values specified and agreed upon are compatible, that is, that the upper limit
of the subtransient reactance is not set too close to the lower limit of the transient reactance.
When the value of the direct axis subtransient reactance is not specified, it shall be not less
than 0,1 p.u. at the saturation level corresponding to rated voltage.
The value of each of these reactances may be specified and agreed upon at another
saturation level in accordance with IEC 60034-4. If it is agreed that values are to be
determined by test, the test shall be in accordance with IEC 60034-4.
4.19 Tolerances on short-circuit ratio and direct axis transient and subtransient
reactances
Where the limit values of this standard, or other limits, have been specified or agreed upon,
there shall be no tolerance in the significant direction, that is, no negative tolerance on
minimum values and no positive tolerance on maximum values. In the other direction, a
tolerance of 30 % shall apply.
If values are specified but not declared to be limits, they shall be regarded as rated values,
and shall be subject to a tolerance of ±15 %.
Where no values have been specified by the purchaser, the manufacturer shall give values,
subject to a tolerance of ±15 %.
4.20 Mechanical conditions for rotors
4.20.1 Number of starts
Unless otherwise agreed upon, the rotor shall have a mechanical design capable of
withstanding during its lifetime:
– normally not less than 3 000 starts;
– for those designed for regular start-stop duties such as daily service not less than 10 000
starts.
4.20.2 Turning gear operation
Before start-up and after shut-down, turning gear operation of the turbine generator set may
be unavoidable primarily due to prime mover needs. However, prolonged turning gear
operation may make the generator rotor susceptible to damage and should be limited.
Susceptibility to turning gear operation damages can be influenced by the design. If a longer

60034-3 © IEC:2007 – 13 –
turning gear operation is considered additional design efforts for minimizing the harmful
effects should be the subject of an agreement.
4.21 Coolers
Unless otherwise agreed upon, coolers shall be suitable for cold water intake temperatures up
to 32 °C and a working pressure of not less than:
– 2,7 bar absolute (270 kPa) for air cooled generators;
– 4,5 bar absolute (450 kPa) for hydrogen and liquid cooled generators;
The test pressure shall be 1,5 times the maximum working pressure, and shall be applied for
15 min.
If the water pressure in the cooler is controlled by a valve or pressure-reducing device
connected to a water supply where the pressure is higher than the working pressure of the
cooler, the cooler shall be designed for the higher pressure, and tested at 1,5 times the higher
pressure value, unless otherwise agreed upon. This pressure shall be specified by the
purchaser.
Coolers shall be designed so that, if one section is intended to be taken out of service for
cleaning, the unit can carry at least two-thirds (or, by agreement, another fraction) of rated
load continuously, without the permissible temperatures of the active parts of the generator
being exceeded. Under these conditions, the primary coolant temperature may be higher than
the design value. For hydrogen and liquid cooled generators, attention should be paid to the
fact that under some conditions of operation, for example during maintenance or while purging
the casing of gas, a cooler might be subjected to gas pressure without water pressure. It shall
therefore be designed for a differential pressure of 8 bar (800 kPa) on the gas side.
NOTE Increasing concentrations of chemicals in the water, for example salts or glycol can affect the cooling
performance.
5 Air-cooled generators
5.1 General
This clause applies to generators, the active parts of which are cooled by air, either directly or
indirectly or by a combination of the two methods.
5.2 Generator cooling
The system of ventilation should preferably be a closed air circuit system. If an open air
system is specified or agreed upon, care shall be taken to avoid contaminating the ventilation
passages with dirt, to avoid overheating and pollution of insulated surfaces.
When slip rings for excitation are provided, they should be ventilated separately to avoid
contaminating the generator and exciter with carbon dust.
5.3 Temperature of primary coolant
Generators other than those driven by gas turbines shall be in accordance with IEC 60034-1.
If the maximum temperature of the ambient air, or of the primary cooling air where an air-to-
water cooler is used, is other than 40 °C, the relevant clauses of IEC 60034-1 apply.
Particular requirements for generators driven by gas turbines are given in 7.2 and 7.3.

– 14 – 60034-3 © IEC:2007
5.3.1 Temperature detectors
In order to monitor the temperature of the stator winding, at least six embedded temperature
detectors (ETD) shall be supplied in accordance with IEC 60034-1.
The number of temperature detectors in the air intakes to the generator shall be agreed upon.
6 Hydrogen-cooled or liquid-cooled generators
6.1 General
This clause applies to generators the active parts of which are cooled directly or indirectly by
hydrogen, gas or liquid, or by a combination of both. Some generators may use a gas other
than hydrogen, if so, the same rules apply where appropriate.
6.2 Hydrogen pressure and purity in the casing
The manufacturer shall indicate the absolute hydrogen pressure and purity in the casing, at
which the generator produces its rated output.
The following absolute values of hydrogen pressure are preferred:
bar 2 3 4 5 6 7
kPa 200 300 400 500 600 700
NOTE It is recognized that a conversion from absolute pressure to local gauge pressure is required. The reduced
ambient air pressure at altitudes exceeding 1 000 m above sea level must be taken into account when designing
the auxiliaries.
6.3 Generator housing and cover plates
The complete generator housing, and any pressure-containing cover plates (for example over
coolers) for use with hydrogen as a coolant, shall be designed to withstand an internal
explosion, with the explosive mixture initially at atmospheric pressure, without danger to
personnel. A hydrostatic pressure test shall be made to check the strength of the housing and
cover plates. A suitable test would be the application of 9 bar absolute (900 kPa) for 15 min.
NOTE In some countries, established codes or standards may impose different test requirements.
6.4 Stator winding terminals
The terminals for hydrogen-cooled generators shall be designed to withstand a gas pressure
of at least 9 bar absolute (900 kPa).
Terminal insulators shall be electrically tested independently of the generator windings, and
they shall withstand for 60 s a power-frequency dry dielectric test in air of not less than
1,5 times the 1 min test voltage of the generator winding.
NOTE When the terminals are liquid-cooled, the coolant connections need not be made for the high voltage test.
6.5 Temperature of primary coolants, temperatures and temperature rises of the
generator
Generators other than those driven by gas turbines shall be in accordance with IEC 60034-1.

60034-3 © IEC:2007 – 15 –
The maximum temperatures of the primary coolants, hydrogen or liquid, may be other than
40 °C (for example to obtain an economical design of cooler with the specified maximum
temperature of the secondary coolant). If so:
a) for indirectly cooled generators, the appropriate clauses of IEC 60034-1, concerning
adjustment of temperature rises for air-cooled generators, shall apply;
b) for directly cooled generators, the temperature specified in the appropriate table of
IEC 60034-1 shall apply unchanged.
NOTE In order to avoid excessive temperature rises, or excessive ranges of temperature, the maximum
temperature of the coolant usually should not deviate from 40 °C by more than ±10 K.
Particular requirements for generators driven by gas turbines are given in 7.2 and 7.3.
6.6 Temperature detectors
At least six embedded temperature detectors (ETD) shall be supplied in accordance with
IEC 60034-1. For directly cooled generators, it is important to note that the temperature
measured by ETD is no indication of the hot-spot temperature of the stator winding.
Observance of maximum coolant temperatures given in item 1 in Table 11 of IEC 60034-1 will
ensure that the temperature of the winding is not excessive. The limit of permissible
temperature measured by ETD between the coil sides is intended to be a safeguard against
excessive heating of the insulation from the core. The ETD temperature readings may be
used to monitor the operation of the cooling system of the stator winding.
The number of temperature detectors measuring the coolant temperature where it enters the
generator shall be agreed upon.
For generators with direct cooling of the stator winding, the temperature of the cooling
medium at the outlet of this winding shall be measured with at least three temperature
detectors. These detectors should be in intimate contact with the coolant. Therefore, if the
winding is gas-cooled, they should be installed as close to the exit duct from the coil as is
consistent with electrical requirements. If the winding is water cooled, they should be installed
on the piping inside the generator frame or as near as practicable to where the coolant leaves
the frame, care being taken that there is no significant temperature difference between the
point of measurement and the point where the coolant leaves the winding.
6.7 Auxiliary system
Some or all of the following equipment will be required for satisfactory operation of generators
covered by Clause 6, depending on the design of the coolant and auxiliary systems. The list is
not intended to be complete in all details, and other items may be provided.
a) A complete coolant gas system (hydrogen or other gas), with suitable regulators to control
the gas pressure in the generator, suitable for connecting to the gas supply, a gas dryer
and a means of checking or monitoring the daily gas consumption.
b) A complete system for the purging gas (usually carbon dioxide) suitable for connecting to
the gas supply, to permit the casing to be safely filled with and scavenged of hydrogen.
If the pressurized air system of the power station is used to drive the scavenging gas from
the casing, the connection to the air system shall be arranged to ensure that air cannot be
released into the generator except to remove the scavenging gas, for example by having a
removable pipe connection.
c) Necessary indicators
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