IEC TS 62257-1:2015

IEC TS 62257-1 ®
Edition 3.0 2015-10
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for renewable energy and hybrid systems for rural
electrification –
Part 1: General introduction to IEC 62257 series and rural electrification
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IEC TS 62257-1 ®
Edition 3.0 2015-10
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for renewable energy and hybrid systems for rural

electrification –
Part 1: General introduction to IEC 62257 series and rural electrification

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-2914-9

– 2 – IEC TS 62257-1:2015  IEC 2015
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviations . 7
4 Methodology for rural electrification using hybrid renewable energy systems . 8
4.1 Rural electrification: which solution to choose? . 8
4.2 Decentralized electrification requiring a range of systems . 10
5 How to use the IEC 62257 series for a rural electrification project . 12
5.1 Overview. 12
5.2 Review of the IEC 62257 series: links with the phases of a rural
electrification project (see Table 3) . 15
5.2.1 Opportunity study . 15
5.2.2 Specification of a project . 15
5.2.3 Feasibility study of a project . 17
5.2.4 Detailed technical studies . 18
5.2.5 Implementation of a project. 19
5.2.6 Validation of a project . 20
5.2.7 On field operation . 21
Annex A (normative) Terms, definitions and abbreviations in use in the IEC 62257
series. 23

Figure 1 – Example of electrification progress following a master plan methodology . 9
Figure 2 – Example of electrification of a village using both CESs and IESs . 10
Figure 3 – Contractual relationship between project participants – (IEC TS 62257-
3:2015, Figure 1) . 16
Figure 4 – Example of the content of a non-technical preliminary study – (IEC TS
62257-2:2015, Figure 1) . 18
Figure 5 – TN-C-S system – (IEC TS 62257-5:2015, Figure B.2) . 19
Figure 6 – Phase A battery endurance test – (IEC TS 62257-8-1:2007, Figure 2) . 20
Figure 7 – Test 3, operating cycles – (IEC TS 62257-9-6:2008, Figure 3) . 21

Table 1 – Some advantages and disadvantages of the proposed single and multiple
user systems . 11
Table 2 – Contents of the 62257 series . 13
Table 3 – Utilization of the different parts of the IEC 62257 series according to the
main project phases . 14
Table 4 – Combined categorization – (IEC TS 62257-2:2015, Table C.1) . 17
Table 5 – Service specification (example) – (IEC TS 62257-2:2015, Table C.2) . 17
Table 6 – Verification of the adherence to commitments – (IEC TS 62257-6:2015,

Table 8) . 21
Table 7 – AOMR participant involvement – (IEC TS 62257-6:2015, Table 3) . 22

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RECOMMENDATIONS FOR RENEWABLE ENERGY
AND HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –

Part 1: General introduction to IEC 62257 series and rural electrification

FOREWORD
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The main task of IEC technical committees is to prepare International Standards. In
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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 62257-1, which is a technical specification, has been prepared by IEC technical
committee 82: Solar photovoltaic energy systems. It was developed in cooperation with other
IEC technical committees and subcommittees dealing with renewable energies and related
matters, namely IEC technical committee 21 (Secondary cells and batteries), subcommittee

– 4 – IEC TS 62257-1:2015  IEC 2015
21A (Secondary cells and batteries containing alkaline or other non-acid electrolytes), IEC
technical committee 64 (Electrical installations and protection against electric shock), IEC
technical committee 88 (Wind turbines).
This third edition cancels and replaces the second edition issued in 2013. It constitutes a
technical revision.
The main technical changes with regard to the previous edition are as follows:
– Redefine the maximum AC voltage from 500 Va.c. to 1 000 Va.c., the maximum DC
voltage from 750 Vd.c. to 1 500 Vd.c. and removal of the limitation of 100 kVA system
size. Hence the removal of the word “small” in the title and related references in this
technical specification.
This technical specification shall be used in conjunction with the other documents of the
IEC 62257 series.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
82/942/DTS 82/979/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 in the IEC 62257 series, published under the general title Recommendations
for renewable energy and hybrid systems for rural electrification, can be found on the IEC
website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website 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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INTRODUCTION
Rural electrification is one of the predominant policy actions designed to increase the well-
being of rural populations together with access to clean water, improved healthcare,
education, personal advancement and economic development.
Several strategies can be adopted to implement rural electrification. Rural electrification can
be completed through connection to a national or regional electrification grid. The IEC 62257
series applies to cases where the grid is too far away (too costly) or the individual demand
centres are too small to make grid access economic, where autonomous power systems may
be used to supply these services.
This series IEC 62257 provides technical specifications to different players involved in rural
electrification projects (such as project developers, project implementers, installers, etc.) for
the setting up of renewable energy and hybrid systems with AC voltage below 1 000 Vac and
DC voltage below 1 500 Vdc.
These specifications are recommendations:
a) to choose the right system for the right place,
b) to design the system,
c) to operate and maintain the system.
The specifications focus on rural electrification concentrating on, but not specific to,
developing countries. They must not be considered as all inclusive to rural electrification. That
means that they could be used for rural electrification or electrification of remote sites in
developed countries also. They try to promote the use of renewable energies in rural areas,
emission, carbon
but they do not deal with clean mechanisms development at this time (CO
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 as
possible. One of the main objectives is to provide the minimum sufficient requirements,
relevant to the field of application, that is: renewable energy and hybrid off-grid systems.

– 6 – IEC TS 62257-1:2015  IEC 2015
RECOMMENDATIONS FOR RENEWABLE ENERGY
AND HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –

Part 1: General introduction to IEC 62257 series and rural electrification

1 Scope
This part of IEC 62257 first introduces a methodology for implementing rural electrification
using autonomous hybrid renewable energy systems.
Secondly, it provides a guide for facilitating the reading and the use of the IEC 62257 series
for setting up decentralized rural electrification in developing countries or in developed
countries, the only difference being the level of quality of service and the needed quantity of
energy that the customer can afford.
The IEC 62257 series is designed as follows:
• Parts 2 to 6 are methodological supports for the management and implementation of
projects.
• Parts 7 to 12 are technical specifications for individual or collective systems and
associated components.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC TS 62257-2:2015, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 2: From requirements to a range of electrification systems
IEC TS 62257-3:2015, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 3: Project development and management
IEC TS 62257-4:2015, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 4: System selection and design
IEC TS 62257-5:2015, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 5: Protection against electrical hazards
IEC TS 62257-6:2015, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 6: Acceptance, operation, maintenance and replacement
IEC TS 62257-7, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 7: Generators
IEC TS 62257-7-1, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 7-1: Generators – Photovoltaic arrays
IEC TS 62257-7-3, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 7-3: Generator set – Selection of generator sets for rural electrification
systems
IEC TS 62257-8-1:2007, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 8-1: Selection of batteries and battery management systems for stand-
alone electrification systems – Specific case of automotive flooded lead-acid batteries
available in developing countries
IEC TS 62257-9-1, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 9-1: Micropower systems
IEC TS 62257-9-2, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 9-2: Microgrids
IEC TS 62257-9-3, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 9-3: Integrated system – User interface
IEC TS 62257-9-4, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 9-4: Integrated system – User installation
IEC TS 62257-9-5, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 9-5: Integrated system – Selection of stand-alone lighting kits for rural
electrification
IEC TS 62257-9-6:2008, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 9-6: Integrated system – Selection of Photovoltaic Individual
Electrification Systems (PV-IES)
IEC TS 62257-12-1, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 12-1: Selection of self-ballasted lamps (CFL) for rural electrification
systems and recommendations for household lighting equipment
3 Terms, definitions and abbreviations
For the purposes of this document, the following terms, definitions and abbreviations apply.
The main glossary used in the IEC 62257 series is given in Annex A.
3.1
Collective Electrification System
CES
micropower plant and microgrid that supplies electricity to multiple consumption points using
a single or multiple energy resource points
3.2
GS
general specification
3.3
hybrid system
multi-energy sources system
3.4
Individual Electrification System
IES
micropower plant system that supplies electricity to one consumption point usually with a
single energy resource point
– 8 – IEC TS 62257-1:2015  IEC 2015
3.5
micropower plant
power plant that produces less than 50 kVA through the use of a single resource or hybrid
system
3.6
microgrid
grid that transfers a capacity level less than 50 kVA and powered by a micropower plant
3.7
RE
renewable energy
4 Methodology for rural electrification using hybrid renewable energy systems
4.1 Rural electrification: which solution to choose?
When developing a policy of electrification for a given country or region, there is a
requirement to envision the target situation in the medium term (10 years) and long term (20
to 30 years). This means that a “master plan” for electrifying the country or this region should
preferably be constructed in order to define the lowest life cycle cost solution. Essentially, this
master plan shall take into account both grid extension and autonomous systems solutions.
The master plan should allow selection between two modes of electrification (national/regional
grids or decentralized system) and also, to determine the most suitable time frame to execute
the work. Regarding the decentralized part, each village needs to be investigated to obtain a
variety of sociological, economical and geophysical data. With this approach, the demand
needs can be assessed for each village. This assessment should include possible changes in
the power requirements as a function of the future economic development for each village.
The urban development and the demographic characteristics of each village are also
important to determine the best electrification solution and to assess the amount of capital
investment needed.
Electrification can be achieved by installing decentralized systems if at some points the com-
munity can be (economically) interconnected. Provision can also be made for the integration
or relocation of such systems. Obviously, the solution of using both a local (grid) and
dispersed RE sources generation may be appropriate.
Geographical Information Systems (GIS) are readily available off-the-shelf today and allow a
beneficial and useful graphical presentation of the master plan. In such a representation, each
village can be identified on an appropriate map with colour codes depicting the corresponding
type of power supply.
Furthermore, in such a master plan, villages can be prioritized for further scheduling of the
electrification work on a yearly or 5 year basis. In this process, the cost effectiveness of
the electrification per village would be taken as one of the most significant prioritizing criteria.
This criterion is less important in the developed world but is critical in developing countries.
Simulations can also be made by varying all the relevant parameters to allow a
comprehensive financial analysis of the selected system. Figure 1 is an illustration of
electrification progress following such a master plan methodology.

IEC IEC
Year n electrification work progress Year n + 1 electrification work progress
Key
Collective isolated electrification system

Individual isolated electrification system

Grid line
Figure 1 – Example of electrification progress following a master plan methodology
In the same way, the best strategy shall be determined for electrifying a village or a small
town, according to its topography. Figure 2 shows a village with a densely populated core and
a sparsely populated peripheral zone.
The economic calculation shows that the most economical solution is to electrify the centre of
the village with Collective Electrification Systems (micropower stations and microgrids) and to
electrify the peripheral zone with IES (Individual Electrification Systems) as the cost per
consumer of the microgrid would be higher than the cost of the IESs in this zone.
This methodology provides the lowest electrification cost per customer.

– 10 – IEC TS 62257-1:2015  IEC 2015

Peripheral zone
electrified by
IESs
Dense zone
electrified by CESs
(microgrid and
micropower station)
CES
(Micropower
station and
microgrid)
CES
(Micropower
station and
microgrid)
IEC
Figure 2 – Example of electrification of a village using both CESs and IESs
4.2 Decentralized electrification requiring a range of systems
Rural electrification using decentralized systems is designed to supply power to demand
points located in rural areas that cannot be easily (economically) connected to national grids.
In most cases, these consumption points would consist of the following types of demand:
– specific processes (for example public pumping, battery charging center),
– isolated homes,
– collective facilities (for example public lighting, schools, health and care center, places of
worship, administrative buildings, etc.),
– business activities (for example workshop, micro industry, trade, etc.).
The decentralized system solution can have two basic topologies: Collective Electrification
Systems (CES) which supply electricity to multiple consumption points using a single (or
multiple energy resource points) and Individual Electrification Systems (IES) which supply
electricity to one consumption point (usually with a single energy resource point).
CES systems may be appropriate for rural, relatively highly populated areas, for example,
large villages whereas the IES may be appropriate for more sparsely populated regions and
(or) isolated households.
Individual Electrification Systems (IES) for single users would incorporate two subsystems:
– one electrical power production subsystem,
– one subsystem for utilizing this electrical power.
Collective Electrification Systems (CES) for multiple users on the other hand would
incorporate three subsystems:
– an electrical power production subsystem,
by convention, this part is designated as “micropower plant” where ‘micro’ refers to a
modest production power level (from a few kVA to a few tens kVA),

– a secondary grid for sharing/distributing this power,
by convention, this part is designated as “microgrid” where the prefix ‘micro’ refers to a
modest transit capacity level,
– a demand subsystem including the in-house wiring and user’s electrical appliances.
The decision whether to utilize a CES or IES can be made by looking at the two technological
solutions and calculating the discounted costs. Such an analysis, however, shall take into
account the pertinent sociological and cultural aspects.
The final decision may also be influenced by other considerations, for example, the daily
operating time. Simply designed systems making use of small gensets and a microgrid are
required for sharing and distributing power among the users. Typically, gensets often are run
for limited periods of time during the day, for example between 7 p.m. and 10 p.m.
The use of hybrid micropower plants can allow for a better reliability of the supply. Power is
produced by renewable energy sources when available and stored in batteries. Power can be
made available to the microgrid during a greater part of the day or even all day. Additional
power may be supplied from the gensets when renewable energies are insufficient.
In many developing countries, there is often a very low demand of electricity in rural
households and a concurrent limited capacity for payment. The individual users requirements
typically range between a few tens and a few thousands Wh/day. In developed countries,
energy requirements may be larger as is the expected quality of service.
With very scattered houses, the IES solution may be the obvious choice. If the individual
electricity demand is low, the cost of such systems can also be relatively low – provided the
systems can be produced in large quantities. Table 1 shows some of the advantages and
disadvantages of collective and individual systems.
Table 1 – Some advantages and disadvantages
of the proposed single and multiple user systems
Advantages Disadvantages
• Power consumption is user managed. • In case of inadequate management of the
Consumption will be user determined power, the user will be self-impaired.
from one day to another.
• Failures.
Individual • Systems failures imply only one user.
• Monitoring individual systems can be
Electrification
• Systems can be exchanged and returned expensive and difficult.
Systems (IES)
to manufacturer.
• Maintenance and repair service are not
commonly organized in rural areas
especially in developing countries.
• Power saving can be practiced (possibly) • No possibility exists of exceeding the
using improved management tools subscribed credit of power (assuming an
without impairing the reliability of power automatic cut off).
Collective
supply.
• If the central system fails, everybody is
Electrification
• Telemetry can be economic for cut off.
Systems (CES)
monitoring system status.
• Systems generally need to be serviced on
site.
In both cases the electrical appliances used should be of the low power/energy efficient type,
for example high efficiency fluorescent lighting. Using such appliances can be a drawback
because this type of equipment can cost more than standard electrical appliances. For
example, low consumption lighting is still considerably more expensive than tungsten
incandescent lamps.
The use of low consumption or efficient loads should be compulsory in these projects. This
means that supply of the demand items, as far as possible, may be best included as part of

– 12 – IEC TS 62257-1:2015  IEC 2015
the energy supply package. This should include as a minimum low consumption lamps but
also mechanisms to purchase high efficiency appliances.
5 How to use the IEC 62257 series for a rural electrification project
5.1 Overview
The summary of the series is given in Table 2. The different parts have been designed
following the main topics about rural decentralized electrification. The documents are
classified accordingly.
Through the following information the reader is guided and assisted for finding the right
information needed for each phase of the project.
This guide is organized following the phasing of the setting up of a rural electrification project.
Table 3 gives a presentation of the documents and establishes links between the phases of
the projects and the content of the documents.

Table 2 – Contents of the 62257 series
Introduction to IEC 62257 series and decentralized rural electrification
IEC TS 62257-1 (2015) Ed. 3.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 1: General
introduction to IEC 62257 series and rural electrification
Management of project – rules for designing, managing and operating rural electrification systems
IEC TS 62257-2 (2015) Ed. 2.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 2: From requirements
to a range of electrification systems
IEC TS 62257-3 (2015) Ed. 2.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 3: Project
development and management
IEC TS 62257-4 (2015) Ed. 2.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 4: System selection
and design
IEC TS 62257-5 (2015) Ed. 2.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 5: Protection against
electrical hazards
IEC TS 62257-6 (2015) Ed. 2.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 6: Acceptance,
operation, maintenance and replacement
Technical specifications
IEC TS 62257-7 (2008-04) Ed. 1.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 7: Generators
IEC TS 62257-7-1 (2010-09) Ed. 1.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 7-1: Generators –
Photovoltaic arrays
IEC TS 62257-7-3 (2008-04) Ed. 1.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 7-3: Generator set –
Selection of generator sets for rural electrification systems
IEC/TS 62257-8-1 (2007-06) Ed. 1.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 8-1: Selection of
batteries and battery management systems for stand-alone electrification systems – Specific case of automotive
flooded lead-acid batteries available in developing countries
IEC TS 62257-9-1 (2008-09) Ed. 1.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 9-1: Micropower
systems
IEC TS 62257-9-2 (2006-10) Ed. 1.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 9-2: Microgrids
IEC TS 62257-9-3 (2006-10) Ed. 1.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 9-3: Integrated
system – User interface
IEC TS 62257-9-4 (2006-10) Ed. 1.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 9-4: Integrated
system – User installation
IEC TS 62257-9-5 (2015) Ed. 3.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 9-5: Integrated
system – Selection of stand-alone lighting kits for rural electrification projects
IEC TS 62257-9-6 (2008-09) Ed. 1.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 9-6: Integrated
system – Selection of Photovoltaic Individual Electrification Systems (PV-IES)
IEC TS 62257-12-1 (2007-06) Ed. 1.0
Recommendations for renewable energy and hybrid systems for rural electrification – Part 12-1: Selection of
self-ballasted lamps (CFL) for rural electrification systems and recommendations for household lighting
equipment
– 14 – IEC TS 62257-1:2015  IEC 2015
Table 3 – Utilization of the different parts of the IEC 62257 series
according to the main project phases
Reference Phases of a Phases of a rural Player Deliverable IEC 62257
No. project electrification involved pertinent
project part
5.2.1 Opportunity - Master plan of - Owner/ - Master plan Part 1
study electrification Project
- Time table of
developer
(Where to develop the electrification
national grid - Engineering (taking into
consultant account
Where to develop off
economic or
grid electrification)
political
priorities)
- Amount of
investment (total
and per year)
5.2.2 Specification - Target definition - Project - List and maps of Part 2
(location, size of developer small towns and
Part 3
the project) villages to be
- Engineering
electrified
consultant
5.2.3 Feasibility - Feasibility - Project - Renewable Part 2
developer energies
(Technical and socio
resource
economical) - Engineering economic
assessment
consultant study
(socio - Socio
economical, economical
financial) study
- Business plan
5.2.4 Detailed Writing of the General - Project - General Part 2
technical Specification developer specification
Part 3
studies
- Engineering
Part 4
consultant
Part 5
Parts 7 to 12
5.2.5 Implementation Erection, - Project - Electrical Part 5
commissioning implementer installations
Part 6
- Suppliers - Commissioning
sheets
- Sub-
contractors
- Training
providers
5.2.6 Validation Assessment: does the - Project - Quality of Part 6
service provided developer service
comply with the assessment
- Engineering
General Specification report
consultant
- Project
implementer
5.2.7 On field - Operation - Owner/ - Quality of Part 5
operation Project service
- Maintenance Part 6
developer
- Quality of
- Replacement and relevant
- Operator management
technical
- Management
- Customer specification
relationship
- Recycling
5.2 Review of the IEC 62257 series: links with the phases of a rural electrification
project (see Table 3)
5.2.1 Opportunity study
A master plan for the electrification of a region of a developing country or the electrification of
remote sites in developed countries shall take into account both the development of the
national or the regional grid and the use of decentralized collective or individual systems.
Part 1 entitled:
rural electrification – Part 1: General introduction to IEC 62257 series and rural
electrification
provides the basics on the rural electrification methodology using both the development of the
grid and standalone systems and explains the different options to carry it out.
It especially introduces the advantages or disadvantages of collective and individual
electrification solutions. Part 1 also introduces the different parts of the series which will be
useful for the players involved for each part of the project.
Figure 1 of this Part 1 illustrates the implementation of a master plan year after year using
both the development of the grid and the use of decentralized autonomous collective or
individual systems.
5.2.2 Specification of a project
In this phase, the solvable needs of the future customers shall be assessed in order to define
the technical solutions which are suitable to satisfy them.
Part 2 entitled
IEC TS 62257-2:2015, Recommendations for renewable energy and hybrid systems for
rural electrification – Part 2: From requirements to a range of electrification systems
presents the methodological approach to carry out this phase of the project.
It also presents a range of systems and provides assistance for choosing the right system
according to the characteristics of the needs it can satisfy (range of services, power, quantity
of energy, level of quality of service, etc.).
Examples of standardized range of services along with standardized systems architectures
are also provided.
Part 3 entitled
IEC TS 62257-3:2015, Recommendations for renewable energy and hybrid systems for
rural electrification – Part 3: Project development and management
emphasizes the necessity of defining the different players involved in the project, their needed
competencies, their respective responsibilities and the contracts that shall link them, prior to
starting any work on the project.
This preliminary action is one of the key elements for the successful implementation of the
project.
Part 3 proposes the implementation of a quality assurance approach, allowing the owner and
the project implementer to check at specified intervals that:

– 16 – IEC TS 62257-1:2015  IEC 2015
– the project is suitably designed to satisfy the needs of the future customers,
– the technical installations are implemented according to the General Specification,
– operation, maintenance, feedback and validation of the quality of service are correctly
organized.
Figure 3 below is reproduced from Figure 1 of IEC TS 62257-3:2015. It illustrates the
contractual links that shall be established between the stakeholders of the project.
Table 4 below is reproduced from Table C.1 of IEC TS 62257-2:2015; it gives examples of
indicators which can be used to adapt the quality of service to the solvable and affordable
needs of the future customers and specify them in the General Specification.
C
Owner
C
C
C
Training Engineering
Project developer
provider consultant
Transfer of Transfer of
C
responsibility responsibility
C
Project
Subcontractor
implementer
Provision for
training
C
Operator User
C
Provision for
training
Provision for
training
Maintenance
contractor
IEC
NOTE “C” represents a potential contractual arrangement between two connecting parties.
Figure 3 – Contractual relationship
between project participants – (IEC TS 62257-3:2015, Figure 1)

Table 4 – Combined categorization – (IEC TS 62257-2:2015, Table C.1)
Power quality indicators
Require Specified Specified supply Required power quality
ment duration of availability
a
class service (%/year)
(h/day) 1 2 3 1 2 3
A = 24 h
B
16 ≤ h < 24
C 8 ≤ h < 16
±∆U ≤ 10 % U ±∆U ≤ 15 % U ±∆U ≤ 20 % U
N N N
≥ 99 ≥ 98 ≥ 95
±∆f ≤ 1 Hz ±∆f ≤ 2 Hz ±∆f ≤ 3 Hz
THD ≤ 3 % THD ≤ 5 % THD ≤ 10 %
D
4 ≤ h < 8
E
h < 4
F Systems requiring power quality indicators either above or below these values may be specified
according to special requirements.
U The r.m.s. voltage at a given time at the supply terminals, measured over a given interval.
N
f The nominal frequency of the supply voltage U should be f. Under normal operating conditions the mean
N
value of the fundamental frequency measured over 10 s should be within the range of f ± ∆f.

a
Start time and end time of the period for the duration of service should be implemented in the contract.

Table 5 illustrates a specific example of the use of Table 4.
Table 5 – Service specification (example) – (IEC TS 62257-2:2015, Table C.2)
Cat 1 D 1 3
Maximum available Weekly average Service provided for
P ≤ 100 W
±∆U ≤ 20 % U ,
N
power demand: service providing more than 99 % of the
energy 4 h per day, as year
±∆f ≤ 3 Hz,
a maximum.
THD ≤ 10 %
Average energy E ≤ 0,5 kWh
provided over 24 h
5.2.3 Feasibility study of a project
In this phase, the socio-economic characteristics of the future clients, the geographic and
topographic characteristics and the renewable energies resources of the site are assessed in
order to establish a business plan and verify the viability of the project.
These studies are essential for the next step which is to choose the technical solutions and
write the General Specification.
The results of the socio-economic study, the methodology of which is explained in Part 2 are
used to establish the profile of the future clients in terms of solvable needs for electrical
services.
Part 4, entitled
IEC TS 62257-4:2005, Recommendations for renewable energy and hybrid systems for
rural electrification – Part 4: System selection and design
classifies
...