Recommendations for small renewable energy and hybrid systems for rural electrification - Part 7-3: Generator set - Selection of generator sets for rural electrification systems

IEC/TS 62257-7-3:2008(E) specifies the general requirements for the selection, sizing, erection and operation of generator sets in decentralized rural electrification systems. Applies to all low voltage combustion engine electricity generator sets with a rated power up to 100 kVA, and designed for supplying electrical power to isolated sites used in systems as described in IEC/TS 62257-2.

Priporočila za sisteme malih obnovljivih virov energije in hibridne sisteme za elektrifikacijo podeželja - 7-3. del: Generatorski sklopi - Izbira generatoskih sklopov za sisteme elektrifikacije podeželja

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SLOVENSKI STANDARD
SIST-TS IEC/TS 62257-7-3:2008
01-november-2008
3ULSRURþLOD]DVLVWHPHPDOLKREQRYOMLYLKYLURYHQHUJLMHLQKLEULGQHVLVWHPH]D
HOHNWULILNDFLMRSRGHåHOMDGHO*HQHUDWRUVNLVNORSL,]ELUDJHQHUDWRVNLK
VNORSRY]DVLVWHPHHOHNWULILNDFLMHSRGHåHOMD

Recommendations for small renewable energy and hybrid systems for rural electrification

- Part 7-3: Generator set - Selection of generator sets for rural electrification systems

Ta slovenski standard je istoveten z: IEC/TS 62257-7-3
ICS:
27.190 Biološki viri in drugi Biological sources and
alternativni viri energije alternative sources of energy
29.160.40 (OHNWULþQLDJUHJDWL Generating sets
SIST-TS IEC/TS 62257-7-3:2008 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TS IEC/TS 62257-7-3:2008
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SIST-TS IEC/TS 62257-7-3:2008
IEC/TS 62257-7-3
Edition 1.0 2008-04
TECHNICAL
SPECIFICATION
Recommendations for small renewable energy and hybrid systems for rural
electrification –
Part 7-3: Generator set – Selection of generator sets for rural electrification
systems
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
ICS 27.160; 27.180 ISBN 2-8318-9672-X
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SIST-TS IEC/TS 62257-7-3:2008
– 2 – TS 62257-7-3 © IEC:2008(E)
CONTENTS

FOREWORD...........................................................................................................................4

INTRODUCTION.....................................................................................................................6

1 Scope...............................................................................................................................7

2 Normative references .......................................................................................................8

3 Terms and definitions .......................................................................................................9

4 Introduction to generator sets .........................................................................................11

4.1 Generator set system ............................................................................................11

4.2 Generator set application in rural electrification systems .......................................11

4.3 Resource assessment ...........................................................................................11

5 Selection and erection ....................................................................................................12

5.1 General .................................................................................................................12

5.2 Selection requirements..........................................................................................12

5.2.1 Power quality.............................................................................................12

5.2.2 Generator set sizing ..................................................................................12

5.2.3 Generator set type.....................................................................................14

5.2.4 Derating factors.........................................................................................14

5.2.5 Starting system..........................................................................................15

5.2.6 Control systems.........................................................................................15

5.2.7 Noise issues..............................................................................................15

5.2.8 Environmental issues ................................................................................15

5.3 Erection.................................................................................................................15

5.3.1 Shipping ....................................................................................................15

5.3.2 Design of the erection site .........................................................................16

5.3.3 Installation requirements ...........................................................................17

6 Safety.............................................................................................................................20

6.1 General .................................................................................................................20

6.2 Electrical issues ....................................................................................................20

6.2.1 General requirements ................................................................................20

6.2.2 Connection system to the application.........................................................20

6.2.3 Power cables.............................................................................................21

6.2.4 Neutral system ..........................................................................................21

6.2.5 Earthing.....................................................................................................21

6.2.6 Overcurrent protection...............................................................................21

6.2.7 Residual Current protection Device (RCD).................................................22

6.2.8 Isolating devices........................................................................................22

6.3 Mechanical issues .................................................................................................22

6.3.1 Vibration....................................................................................................22

6.3.2 Protection from mechanical damage ..........................................................22

6.3.3 Protection from moving parts .....................................................................22

6.4 Thermal issues......................................................................................................23

6.5 Fire risk.................................................................................................................23

7 Acceptance ....................................................................................................................23

7.1 General .................................................................................................................23

7.2 Conformity of the generator set to the identification file .........................................23

7.3 Conformity of the generator set system to the GS..................................................23

7.4 Acceptance process ..............................................................................................23

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SIST-TS IEC/TS 62257-7-3:2008
TS 62257-7-3 © IEC:2008(E) – 3 –

7.4.1 Preparation of the generator set for commissioning ...................................23

7.4.2 Commissioning inspection of the generator set system ..............................24

7.4.3 Commissioning tests of the generator set system ......................................24

7.4.4 Test file .....................................................................................................25

8 Operation and maintenance............................................................................................25

8.1 Access to the generator set...................................................................................25

8.2 Operation process .................................................................................................25

8.3 Monitoring .............................................................................................................26

8.4 Maintenance schedule...........................................................................................26

9 Replacement ..................................................................................................................26

10 Marking ..........................................................................................................................27

10.1 Generator set ........................................................................................................27

10.2 Engine...................................................................................................................27

10.3 Alternator ..............................................................................................................27

10.4 Shutdown apparatus..............................................................................................28

11 Documentation ...............................................................................................................28

11.1 General .................................................................................................................28

11.2 Installation ............................................................................................................28

11.3 Operation ..............................................................................................................29

11.4 Inspection and maintenance ..................................................................................29

Annex A (informative) Generator set classification criteria ...................................................30

Annex B (informative) Identification file................................................................................34

Annex C (informative) Maintenance schedule ......................................................................35

Annex D (informative) Example of commissioning records sheet..........................................36

Bibliography..........................................................................................................................38

Figure 1 – General functional configuration of a generator set powered system ......................7

Table 1 – Examples of derating factors for generator sets.....................................................14

Table 2 – Generator set permitted noise levels .....................................................................15

Table 3 – Cross-section of power cables...............................................................................21

Table A.1 – Classification of generator set services ..............................................................30

Table A.2 – Common lifespan values ....................................................................................31

Table C.1 – Example of maintenance schedule.....................................................................35

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SIST-TS IEC/TS 62257-7-3:2008
– 4 – TS 62257-7-3 © IEC:2008(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RECOMMENDATIONS FOR SMALL RENEWABLE ENERGY
AND HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –
Part 7-3: Generator set –
Selection of generator sets for rural electrification systems
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 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.

The main task of IEC technical committees is to prepare International Standards. In

exceptional circumstances, a technical committee may propose the publication of a technical

specification when

• the required support cannot be obtained for the publication of an International Standard,

despite repeated efforts, or

• the subject is still under technical development or where, for any other reason, there is the

future but no immediate possibility of an agreement on an International Standard.

Technical specifications are subject to review within three years of publication to decide

whether they can be transformed into International Standards.

IEC 62257-7-3, which is a technical specification, has been prepared by IEC technical

committee 82: Solar photovoltaic energy systems.
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SIST-TS IEC/TS 62257-7-3:2008
TS 62257-7-3 © IEC:2008(E) – 5 –

This document is based on IEC/PAS 62111; it cancels and replaces the relevant parts of

IEC/PAS 62111.

This technical specification is to be used in conjunction with the future parts of this series as

and when they are published.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
82/493/DTS 82/508/RVC

Full information on the voting for the approval of this technical specification 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 62257 series, under the general title: Recommendations for small

renewable energy and hybrid systems for rural electrification, 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

• transformed into an International standard;
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
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SIST-TS IEC/TS 62257-7-3:2008
– 6 – TS 62257-7-3 © IEC:2008(E)
INTRODUCTION

The IEC 62257 series of documents intends to provide to different players involved in rural

electrification projects (such as project implementers, project contractors, project supervisors,

installers, etc.) documents for the setting-up of renewable energy and hybrid systems with

a.c. voltage below 500 V, d.c. voltage below 750 V and power below 100 kVA.
These documents are recommendations
– to choose the right system for the right place;
– to design the system;
– to operate and maintain the system.

These documents are focused only on rural electrification concentrating on, but not specific

to, developing countries. They must not be considered as all-inclusive to rural electrification.

The documents try to promote the use of renewable energies in rural electrification; they do

not deal with clean development mechanisms at this time (CO emission, carbon credit, etc.).

Further developments in this field could be introduced in future steps.

This consistent set of documents is best considered as a whole with different parts

corresponding to items for safety, sustainability of systems and at the lowest life-cycle cost

possible. One of the main objectives is to provide the minimum sufficient requirements,

relevant to the field of application, that is, small renewable energy and hybrid off-grid

systems.
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SIST-TS IEC/TS 62257-7-3:2008
TS 62257-7-3 © IEC:2008(E) – 7 –
RECOMMENDATIONS FOR SMALL RENEWABLE ENERGY
AND HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –
Part 7-3: Generator set –
Selection of generator sets for rural electrification systems
1 Scope

The purpose of this part of IEC 62257 is to specify the general requirements for the selection,

sizing, erection and operation of generator sets in decentralized rural electrification systems.

It applies to all low voltage combustion engine electricity generator sets with a rated power up

to 100 kVA, and designed for supplying electrical power to isolated sites used in systems as

described in IEC/TS 62257-2.

This technical specification is not an exhaustive resource for the design, installation,

operation or maintenance of generator sets but is more focused on recommendations to

provide strategies on selection and criteria which may affect the use of such generation

systems in a rural electrification project.

Two cases will be considered as illustrated by Figure 1 to power a collective electrification

system (microgrid) or an individual electrification system.
• the micropowersystem is composed of one generator set

• the micropowersystem is a hybrid one and the generator set is only part of it. This case is

addressed in the document dedicated to micropower system (IEC/TS 62257-9-1).
Generating set alone
• Individual electrification
system (IES)
Generating
set
• Collective electrification
system (CES)
Main switch
Generating set in an hybrid system
• Individual electrification
Secondary
system (IES)
switch
Generating
set
• Collective electrification
system (CES)
Main switch
Other power
sources
IEC 444/08
Figure 1 – General functional configuration of a generator set powered system
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SIST-TS IEC/TS 62257-7-3:2008
– 8 – TS 62257-7-3 © IEC:2008(E)

The aim of this technical specification is to provide users with the appropriate levels of

reliability and safety of the equipment during its estimated service lifespan.

It describes the minimum safety requirements and does not claim to be an exhaustive

instruction manual or design specification.

Compliance with this technical specification does not exempt any person, organization or

corporation from the responsibility to comply with all other relevant regulations.

This technical specification gives recommendations for the following types of generator sets:

a) single phase;
b) three phase;
c) LV range up to 500 V - 50/60 Hz (see IEC/TS 62257-9-2).
2 Normative references

The following referenced documents are essential 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 60034-9, Rotating electrical machines – Part 9: Noise limits

IEC 60034-22, Rotating electrical machines – Part 22: AC generators for reciprocating internal

combustion (RIC) engine driven generating sets
IEC 60529, Degrees of protection provided by enclosures (IP code)

IEC 61009-1, Residual current operated circuit-breakers with integral overcurrent protection

for household and similar uses (RCBOs) – Part 1: General rules

IEC/TS 62257-2:2004, Recommendations for small renewable energy and hybrid systems for

rural electrification – Part 2: From requirements to a range of electrification systems

IEC/TS 62257-5, Recommendations for small renewable energy and hybrid systems for rural

electrification – Part 5: Protection against electric hazards

IEC/TS 62257-6, Recommendations for small renewable energy and hybrid systems for rural

electrification – Part 6: Acceptance, operation, maintenance and replacement
, Recommendations for small renewable energy and hybrid systems for
IEC/TS 62257-9-1
rural electrification – Part 9-1: Micropower systems

IEC/TS 62257-9-2, Recommendations for small renewable energy and hybrid systems for

rural electrification – Part 9-2: Microgrid

ISO 8528-1:2005, Reciprocating internal combustion engine driven alternating current

generating sets – Part 1: Application, ratings and performance

ISO 8528-3:2005, Reciprocating internal combustion engine driven alternating current

generating sets – Part 3: Alternating current generators for generating sets
___________
To be published.
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SIST-TS IEC/TS 62257-7-3:2008
TS 62257-7-3 © IEC:2008(E) – 9 –

ISO 8528-5, Reciprocating internal combustion engine driven alternating current generating

sets – Part 5: Generating sets

ISO 8528-7:1994, Reciprocating internal combustion engine driven alternating current

generating sets – Part 7: Technical declarations for specification and design
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
environmental conditions

environment characteristics (altitude, temperature, humidity, etc.) which may affect the

performance
3.2
generator set

equipment producing electricity from a fossil fuel; it consists basically of an internal

combustion engine producing mechanical energy and a generator which converts the

mechanical energy into electrical energy and mechanical transmission, support and assembly

components
3.3
identification file

document provided by the manufacturer which guarantees the conformity of the equipment

supplied with that which has undergone the type tests
3.4
lifespan

effective period of functioning taking into account the probability of a catastrophic failure

3.5
non-routine maintenance
maintenance necessary in addition to that pre-planned
3.6
rated frequency
frequency at which the generator set is designed to operate
3.7
routine maintenance
preventive maintenance carried out to an established plan
3.8
rated electrical power (nominal power or rated capacity)

maximum continuous power supplied by a generator set in compliance with its specifications,

and under standard operating conditions. This is expressed in VA (volt-ampere) or more

usually in kVA
3.9
rated rotation speed

alternator rotation speed necessary to produce the voltage at the rated frequency

3.10
rated voltage

voltage between phases on the alternator terminals at the rated frequency and rated power

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SIST-TS IEC/TS 62257-7-3:2008
– 10 – TS 62257-7-3 © IEC:2008(E)
3.11
extra low voltage
ELV

voltage not exceeding a limit which is generally accepted to be 50 V a.c. and 120 V d.c. ripple

free
3.12
live conductive part

conductor or conductive part intended to be energized in normal operation, including a neutral

conductor, but by convention not a PE or a PEN conductor
3.13
protected extra-low voltage
PELV

extra-low voltage system which is not electrically separated from earth, but which otherwise

satisfies all the requirements for SELV
3.14
power factor
ratio of real power to apparent power in an a.c. circuit
3.15
real power

for a.c. circuits, the product of voltage, current and power factor, also equal to the rate of flow

of electrical energy. Real power is measured in watt (W)
3.16
apparent power

for a.c. circuits, the product of voltage by current, measured in volt-ampere (VA)

3.17
nominal power of the generator set

maximum apparent power that can be provided by the generator set according to the

manufacturer’s specification
3.18
safety extra-low voltage
SELV

extra-low voltage system which is electrically separated from earth and from other systems in

such a way that a single fault cannot give rise to the risk of electric shock
3.19
minor fuel storage
fuel storage located in the generator set room
3.20
main fuel storage

fuel storage located outside the generator set room and able to provide fuel filling the minor

fuel storage
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SIST-TS IEC/TS 62257-7-3:2008
TS 62257-7-3 © IEC:2008(E) – 11 –
3.21
voltage

differences of potential normally existing between conductors and between conductors and

earth as follows:
a) Extra-low voltage: not exceeding 50 V a.c. or 120 V ripple-free d.c.

b) Low voltage: exceeding upper limits of extra-low voltage, but not exceeding 1 000 V

a.c. or 1 500 V d.c.
c) High voltage: exceeding upper limits of low voltage
3.22
protective conductor (identification: PE)

conductor provided for purposes of safety, for example protection against electric shock

[IEV 195-02-09]
3.23
PEN conductor

conductor combining the functions of both a protective earthing conductor and a neutral

conductor
[IEV 195-02-12]
4 Introduction to generator sets
4.1 Generator set system

In the present document a generator set system includes the installed generator set itself, the

related civil works or prefabricated enclosure if any and all relative ancillaries such as fuel

tank, pipes, earthing systems, etc. necessary for the operation of the generator set.

4.2 Generator set application in rural electrification systems

The usage of generator sets in rural electrification systems application, are described in

IEC/TS 62257-2 for T3, T4, T5 and T6 categories of systems.

In these system categories the generator sets are used to recharge batteries and/or provide a

backup power supply to all or part of the a.c. distribution system, or to supply a.c. dedicated

equipment.

The type of use of the generator set shall be clearly identified by the project developer and

notified to the supplier.
4.3 Resource assessment

Before choosing a generator set as the generator in an electrification system, it is important to

check the availability of the fuel supply on the installation site. It is important to check if the

supply is possible all throughout the year. For example in some countries it could be

impossible to deliver fuel to the site during the rainy season.

The project implementer also shall take into account that the cost of fuel may vary with the

price of the oil market and also with changes in local subsidies.
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SIST-TS IEC/TS 62257-7-3:2008
– 12 – TS 62257-7-3 © IEC:2008(E)
5 Selection and erection
5.1 General

A lot of technologies are available on the market for engines, from the most simple to the

most sophisticated.

For small size (~below 5 kVA) the most commonly used technology is gasoline engines.

For larger size, the most commonly used technology is diesel engines.
Other fuels can be used such as oil, or ethanol.

The engines are designed either for 3 000 rpm (generally for small machines) or 1 500 rpm

(generally for larger machines) at 50 Hz case.
Other technologies like small fuel turbines may be also available.

The project implementer shall select the appropriate technology corresponding to the required

level of quality of the service, the skill of the maintenance staff, the level of equipment

available at the maintenance centre, the spare parts than can be easily sourced, and all

specific constraints of the project. Annex A provides some information about the classification

of different types of generator sets as they are available on the market.
5.2 Selection requirements
5.2.1 Power quality

Type and configuration of generator set shall be selected in relation with the requirements of

the power supply to the end user as given in the General Specification (GS) of the project.

These requirements shall refer to the different figures expressed in IEC/TS 62257-2, Annex C.

The control system of the generator set shall be able to provide information necessary to

assess that t
...

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