IEC TS 62257-4:2005

IEC/TS 62257-4 ®
Edition 1.0 2005-07
TECHNICAL
SPECIFICATION
Recommendations for small renewable energy and hybrid systems for rural
electrification –
Part 4: System selection and design

IEC/TS 62257-4:2005(E)
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IEC/TS 62257-4 ®
Edition 1.0 2005-07
TECHNICAL
SPECIFICATION
Recommendations for small renewable energy and hybrid systems for rural
electrification –
Part 4: System selection and design

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XB
ICS 27.160; 27.180 ISBN 2-8318-8101-3

– 2 – TS 62257-4  IEC:2005(E)
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope.7
2 Normative references .7
3 Terms and definitions .8
4 Functional requirements of production and distribution subsystems.9
4.1 Preliminaries .9
4.2 Overall needs to be satisfied .9
4.3 Introduction to subsystems.13
4.4 Functional description of a production subsystem.13
4.5 Functional description of a distribution subsystem .15
4.6 Functional description of a demand subsystem.17
4.7 Constraints to be complied with by production distribution and demand subsystems 17
5 Energy management rules .18
5.1 General .18
5.2 Functional description for an energy management of an isolated system .19
5.3 Demand side management .20
6 Expected results from the sizing process.20
6.1 Introduction .20
6.2 Participants in the sizing process .21
6.3 Elements for comparing various design proposals .21
6.4 Frameworks for proposal .21
6.5 Proposal for a sizing process .38
6.6 Impact of design assumptions on system sizing and cost .38
6.7 Guarantee of results.40
7 Data acquisition rules for system management.40
7.1 Introduction .40
7.2 General .41
7.3 Levels of data acquisition and data necessity. .41
7.4 Data to be collected .46
7.5 Operating conditions, electrical and engineering requirements for data
acquisition.47

Annex A (informative) Example for detailed performance criteria and levels

for a production subsystem .48
Annex B (informative) Example for detailed performance criteria and levels
for a distribution subsystem .49
Annex C (informative) Example framework for proposal specification.50
Annex D (informative) Equation for costs calculations.57
Annex E (informative) Proposal for a sizing process .61

Figure 1 – Factors involved in the design of a system .10
Figure 2 – Functional diagram of a radial structure for rural micro-grid.17
Figure 3 – Functional impact of energy management and safety .19
Figure E.1 – Sizing process flow chart .61

TS 62257-4  IEC:2005(E) – 3 –

Table 1 – Participants in the sizing process .21
Table 2 – Perspectives to be considered (see symbols in IEC 62257-2, Table 4) .22
Table 3 – Commitments indicators .23
Table 4 – Knowledge of site.24
Table 5 – Knowledge of consumption data .25
Table 6 – Knowledge of resources: data accuracy levels .25
Table 7 – Knowledge of resources: data retained for considered site .27
Table 8 – Knowledge of resources: range of data history .27
Table 9 – Characteristics for photovoltaic modules .28
Table 10 – Characteristics for modules supporting structure .28
Table 11 – Characteristics for the wind turbine .29
Table 12 – Characteristics for wind turbine structure.29
Table 13 – Characteristics for the generator set.30
Table 14 – Characteristics for micro hydro turbines .31
Table 15 – Characteristics for biomass generators.32
Table 16 – Characteristics for power converters .33
Table 17 – Characteristics for load manager/meter .34
Table 18 – Characteristics for system controllers .35
Table 19 – Characteristics for batteries.35
Table 20 – Characteristics for links and wiring .36
Table 21 – Energy output from renewable energies .36
Table 22 – Energy output from fossil energies .36
Table 23 – Energy output from storage .36
Table 24 – Incidence of energy management assumptions on system sizing.39
Table 25 – Incidence of cost management assumptions on system dimensions .40
Table 26 – Information required by the energy manager and data to collect .42
Table 27 – Information required by the operator and data to collect .44
Table 28 – Information required by the user and data to collect .45
Table 29 – Summary of the needed information .45
Table 30 – Minimum set of data to be collected .46
Table 31 – Relationship between required information and system architecture .47
Table E.1 – Description of utilities to be power supplied .62
Table E.2 – Consumption characteristics .63
Table E.3 – Meteorological data used for sizing .64
Table E.4 – Proposals for types of cost to be accounted for.64
Table E.5 – Site constraints inventory.65
Table E.6 – Impact of energy management assumptions on plant sizing .66
Table E.7 – Impact of cost management assumptions on plant sizing .66

– 4 – TS 62257-4  IEC:2005(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RECOMMENDATIONS FOR SMALL RENEWABLE ENERGY
AND HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –

Part 4: System selection and design

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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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 62257-4, which is a technical specification, has been prepared by IEC technical
committee 82: Solar photovoltaic energy systems.

TS 62257-4  IEC:2005(E) – 5 –
This document is based on IEC/PAS 62111(1999); it cancels and replaces the relevant parts
of IEC/PAS 62111.
This technical specification is to be used in conjunction with IEC 62257 series.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
82/369/DTS 82/389/RVC
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.
IEC 62257 consists of the following parts, under the general title Recommendations for small
renewable energy and hybrid systems for rural electrification:
Part 1: General introduction to rural electrification
Part 2: From requirements to a range of electrification systems

Part 3: Project development and management

Part 4: System selection and design
Part 5: Protection against electrical hazards
Part 6: Acceptance, operation, maintenance and replacement
Part 7: Technical specifications: generators
Part 8: Technical specifications: batteries and converters
Part 9: Technical specifications: integrated systems
Part 10: Technical specifications: energy manager
Part 11: Technical specifications: considerations for grid connection
Part 12: Appliances
Part 13: Other topics
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 edition of this publication may be issued at a later date.
___________
Under consideration.
– 6 – TS 62257-4  IEC:2005(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.
nominal voltage below 500 V d.c. nominal voltage below 750 V and nominal 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 shall 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 mechanisms developments 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 as
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.
The purpose of this part of IEC 62257 is to provide a method to assist project contractors and
project developers to select and design the electrification system for isolated sites while
matching the identified needs, such as those described in IEC 62257-2.

TS 62257-4  IEC:2005(E) – 7 –
RECOMMENDATIONS FOR SMALL RENEWABLE ENERGY
AND HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –

Part 4: System selection and design

1 Scope
This part of IEC 62257 provides a method for describing the results to be achieved by the
electrification system independently of the technical solutions that could be implemented.
IEC 62257-2 assessed the needs of the users and the different power system architectures
which can be used for meeting these needs.
In relation to the needs of the different participants to the project, functional requirements that
shall be achieved by the production and distribution subsystems are listed.
In Clause 5, energy management rules to be considered are described. These are key issues
as they have a great influence on the sizing of the electrification system.
In Clause 6, the information that shall be provided by the system sizing process to allow the
participants to select the equipment or component able to fulfill the functional requirements
are listed.
To allow and facilitate the management of the micro-power plant and the maintenance of the
whole electrification system, some information shall be collected and monitored. Clause 7 is
dedicated to defining the parameters and specifying rules for data acquisition.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For updated references, the last edition of
the referenced document (including any amendment) applies.
IEC 62257-1, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 1: General introduction to rural electrification
IEC 62257-2, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 2: From requirements to a range of electrification systems
IEC 62257-3, Recommendations for small renewable energy and hybrid systems for rural

electrification – Part 3: Project development and management
IEC 62257-4, Recommendations for small renewable energy and hybrid systems for rural

electrification – Part 4: System selection and design
IEC 62257-5, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 5: Protection against electrical hazards
IEC 62257-6, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 6: Acceptance, operation, maintenance and replacement

– 8 – TS 62257-4  IEC:2005(E)
IEC 62257-7, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 7: Technical specifications: generators
IEC 62257-8, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 8: Technical specifications: batteries and converters
IEC 62257-9, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 9: Technical specifications: integrated systems
IEC 62257-10, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 10: Technical specifications: energy manager
IEC 62257-11, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 11: Technical specifications: considerations for grid connection
IEC 62257-12, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 12: Appliances
IEC 62257-13, Recommendations for small renewable energy and hybrid systems for rural
electrification – Part 13: Other topics
3 Terms and definitions
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.
3.1
REN
renewable energy
3.2
hybrid system
multi-sources system with at least two different kind of technologies
3.3
dispatchable power system
a source, generator, system is dispatchable if delivered power is available at any specified
time
EXAMPLE: a genset is a dispatchable system, REN generator is usually a non dispatchable power system.
3.4
non dispatchable power system
a non dispatchable system is resource dependent; power might not be available at a specified
time
3.5
storage
storage of energy produced by one of the generator of the system and which can be
reconverted through the system to electricity
___________
Under consideration.
TS 62257-4  IEC:2005(E) – 9 –
3.6
rural micro-power plant
power plant that produces less than 50 kVA through the use of a single resource or hybrid
system
3.7
rural micro-grid
grid that transfers a capacity level less than 50 kVA and powered by a micro-power plant
3.8
Individual Electrification System
IES
micro-power plant system that supplies electricity to one consumption point usually with a
single energy resource point
3.9
Collective Electrification System
CES
micro-power plant and micro-grid that supplies electricity to multiple consumption points using
a single or multiple energy resource points
3.10
isolated site
electric characteristic to define a specific location not currently connected to a national/
regional grid
3.11
remote site/area
geographic characteristic to define a specific location far from developed infrastructures,
specifically energy distribution
4 Functional requirements of production and distribution subsystems
4.1 Preliminaries
The purpose of Clause 4 is to provide a method for describing the results to be achieved by
electrification systems for isolated sites as defined in IEC 62257-2. It describes the
characteristics expected from these installations based on production of electricity from
renewable and/or fossil energy sources.
This stage of defining the expected results of production precedes the technical dimensioning
and details engineering stages.
4.2 Overall needs to be satisfied
4.2.1 The main factors to be considered
The Figure 1 illustrates the main factors influencing the design of the micro-power plant.

– 10 – TS 62257-4  IEC:2005(E)
Technical factors involved in Economic factors involved in
the system implementation the system implementation

System design
International/national/local Site characteristics
regulations and technical
standard requirements
IEC  1050/05
Figure 1 – Factors involved in the design of a system
4.2.2 Needs and characteristics to be considered
For each of the factors depicted in Figure 1, detailed needs or characteristics to be
considered shall be identified. These needs and characteristics are defined in the following
four tables.
1) Technical factors: needs or characteristics to be considered

Nature of participant Needs or characteristics
Project developer/owner Compliance with the general specification and relevant standards.
Efficient use of energy (demand side management).
Project Easiest possible implementation: limited constraints in term of transportation means
implementer/subcontractor and lifting apparatus.
Technology compatible with limited skills of local manpower.
Limited installation work duration on field.
Standardized equipment.
Operator Simple operational rules to cope with possible limited skills of local operating agents.
Simple mounting tools.
Reliable equipment.
Simple management rules.
Clear and unambiguous contractual rules not liable to lead to situations of dispute or
litigation.
Relevant technical choices/customer management.
Limited spare parts variety.
Maintenance contractor Reliable and easy-to replace on site equipment.
Limited spare parts variety.
Different users/loads Types of energy services (see IEC 62257-2, Annex B).

TS 62257-4  IEC:2005(E) – 11 –
2) Economic factors: needs and characteristics to be considered
Nature of participant Needs or characteristics
Project developer/owner Balance between initial capital costs and operational costs to make the project
profitable and sustainable.
Project implementer Balance between equipment cost (purchase and installation) and specified level of
reliability.
Subcontractor To make a correct living while fulfilling the project implementer’s requirements.
Operator Operational costs as low as possible.
Maintenance contractor To have an economically viable activity while fulfilling the operator’s requirements.
The different users/loads Available services promised (lighting, TV, etc.) at the contractual level of quality, for
the agreed price.
3) Site characteristics
General
characteristics Detailed characteristics Comments
of site
Geographical Weather statistics (T°, humidity, General information about the standard conditions at the site.
environment wind, precipitation,…)
Climate and severe weather or The characteristics of the climate at the site will affect the
other local hazards design of the system and the nature of its constituent
equipment.
One may mention:
temperature differences;
hygrometry differences;
rainfall and snowfall;
superimposed loads on structures (caused by wind,
cyclones, frost, etc.);
pollution (sand, salt, dust, other pollutant wastes).
Energy resources Definition of local energy resources. See Table 4 for further
details.
Means of access to and around General access to the site, bridges road conditions and ease
the site of access around the site (streets, rivers, etc.) will affect the
difficulty in crossing obstacles and anticipating changes in the
micro distribution network, etc.
Nature of soil (geological This affects the type of structure (overhead or buried power
environment) lines) to be set up and the execution of certain installations
(for example grounding system depending on the resistively
characteristics of the ground and system foundations).
Geographical distribution of the This is a major factor in the cost of the distribution
user points infrastructures. The scatter or concentration of the user
points, their probable evolution (near or remote) time-wise
and space-wise, will affect choices concerning the topology of
the distribution network.
Human Distance to/between homes
environment /loads – production system
Type of homes /loads
Acceptable noise level
Acceptable waste disposal level
Type of building to house the
rural micro-power plant
Biological Fauna
environment
Flora
Type of tree cover
– 12 – TS 62257-4  IEC:2005(E)

General
characteristics Detailed characteristics Comments
of site
Technical Type of grid in place, if any
environment (overhead, buried)
Civil engineering
Quality of existing building This may be either an ally or an enemy as regards to certain
solutions for providing supports for conductors (the physical
quality of the building, its height, etc.)
Possible local maintenance at
site
Available telecommunication
facilities
Equipment restrictions
Local technical skills level
Soil resistivity
Sociological Energy needs of customers How much energy will consumers need and be willing to pay for.
environment
Energy consumption habits Load profiles for the community.
Type of clientele Distribution by a grid will take place on the basis of:
Sociological criteria (rules of society, living habits.
Economic criteria (combining the grid and the rural micro-
power plant shall cost less than the sum of isolated individual
production/distribution facilities whilst providing the same
service.
Technical criteria (a guaranteed level of service, security,
etc.).
Economic Cost of fuel delivered to site
environment
Cost of technical services
Economic environments in
place
Solvability of customers
Tariff basis for service
4) Regulations and requirements to be considered
Regulatory area References
Procurement quality
Electrical safety
Distribution conditions
Buildings Generation/distribution (to be filled for each project)
Fuel storage
Fuel transport
Local environmental impact
Classified site
Miscellaneous decrees
Possibility of recycling equipment
Production/distribution specification
Import duties
Regulatory authorities
Local labor requirements
TS 62257-4  IEC:2005(E) – 13 –
4.3 Introduction to subsystems
An electrification system shall be considered as a system
Ensuring a power supply service (production subsystem)
and
Providing an electric power distribution service (distribution subsystem)
and
Providing a service to the user (demand subsystem)
whilst at the same time
Complying with constraints (acting on all subsystems)
Individual Electrification Systems (IES) for single users/loads incorporate two subsystems:
– an electrical power production subsystem,
– a demand subsystem for utilizing this electrical power.
Collective Electrification Systems (CES) for multiple users incorporate three subsystems:
– an electrical power production subsystem (rural micro-power plant);
– a distribution grid for sharing this power to individual users (rural micro-grid);
– a demand subsystem including home wiring and user’s electrical appliances for all
individual users.
These subsystems may correspond to systems operated and maintained by different persons
or bodies. In certain cases, the entire system may be owned, operated and used by the same
person.
4.4 Functional description of a production subsystem
4.4.1 General
The function of a production subsystem is to supply electric power and energy to an individual
customer or a combination of permanent customers. This generating subsystem shall be
capable of fulfilling its mission, despite contingencies of availability of the renewable and/or
fossil energy sources supplying it and by managing the consumption patterns of the
customers.
The technical objectives assigned to such an installation can be summarised in the following
essential points:
– to produce and store the energy in a cost effective manner,
– if “REN” sources are used:
• to give precedence to use of REN where they are locally available,
• to store energy from the REN sources whenever they are available,
• to use the back-up energy sources (generator sets) to meet the specified level of
service when REN are not available or sufficient.

– 14 – TS 62257-4 © IEC:2005(E)
4.4.2 Detailed functions to be achieved by a production subsystem
From a functional view point, a production subsystem is a system capable of:
Ensuring a power supply service
Consisting of:
1) Generating electric power
The different sources and architectures are described in IEC 62257-2.
This function embodies everything needed to produce electric power corresponding to the
necessary characteristics of voltage, frequency, harmonics, power and consumption of the
customers, according to the needed quality of service (IEC 62257-2).
This function covers:
• energy conversion from primary energies;
• energy storage (when applicable);
• electric conversion from d.c. to a.c. (if necessary);
• energy measurement.
Given proper supply and maintenance of the system, it can be designed to meet all of the
loads and electrical needs required by the community in an affordable manner.
2) Providing electric power to the distribution subsystem
Following the production of energy, this function ensures that the energy is provided to the
interface with the collective or individual distribution system with respect to the contractual
requirements.
3) Managing energy
In principle, the quantity of energy that can be consumed by the users is not unlimited
owing to the very existence and contingencies of availability of primary energy (solar
radiation, fuel, etc.) and the storage capacities of this energy.
Accordingly, it is important to manage the use of resources provided in order:
– to optimise the use of the available energy,
– to preserve the energy stored in the best way (minimum losses),
– to control energy flows available to the best interest of the customers (immediate
energy needs) and equipment (long service life of the installation),
– to minimise the use of fossil resources, when applicable.
This requires:
• management of the energy production/storage;
• management of the energy storage/distribution;
• management of the energy production/distribution;
• management of the genset operation “on/off” (when applicable).
4) Providing information on the operating condition of the installation
The installation is required to provide the users and operators with the information they
need to control energy production and consumption in their own interests, and where
applicable, that of the community.

TS 62257-4 © IEC:2005(E) – 15 –
4.4.3 Detailed performances criteria to be achieved by a production subsystem
Each criteria shall be developed in order to express the quantitative objectives to be obtained
for the sites studied.
The information should be presented in accordance with the general model given in Annex A.
4.5 Functional description of a distribution subsystem
4.5.1 Detailed functions to be achieved by a distribution subsystem (or rural micro-
grid)
Providing an electric power distribution service
consisting of:
1) Connecting the rural micro-power plant to the application points
This function groups together everything needed to ensure that the terminal application
points are supplied from the rural micro-power plant energy supply point, whilst adapting
to the energy requirements of the different types of customer (individuals, economic
activities, local collective authorities, public lighting, etc.).
Methods should be put in place to account for and monitor rural micro-grid distribution
losses.
2) Not degrading the level of quality
The availability and supply quality objectives shall be taken in to consideration when
designing the rural micro-grid.
3) Including protection to the micro-power plant as needed to ensure safe operation
Protection should be added to:
• Protect the micro-power plant from a harmful short circuit or other electrical impacts to
the extent possible.
• Localize the impact of short circuits or system overloads so that the whole micro-power
plant and all other clients are not interrupted.
4) Executing the decisions of the rural micro-grid manager (load-shedding)
This function describes what the rural micro-grid shall do to comply with the management
rules adopted when the rural micro-grid management system also includes an automatic
function, in order to guarantee that energy is provided to the users. This shall be
completed while insuring the long service of the production subsystem equipment.
The design of the rural micro-grid shall permit modification of its configuration according to
decisions based on information given by the energy management system.
That means:
• allow any agreed changes;
• switch on/off circuits connected to the genset (when applicable);
• switch off circuits according to priority rules;
• provide information to the operator.
5) Managing compliance with the user’s contract
It shall be possible to apply commercial rules in conjunction with the technical service of
making electricity available (connect/disconnect the users under contractual rules).
The use of advanced monitoring and accounting devices can greatly assist in forcing the
compliance of contract.
– 16 – TS 62257-4  IEC:2005(E)
4.5.2 Detailed performances criteria to be achieved by a distribution subsystem
It is impossible here to recommend any general quantitative objectives (performance levels).
The essential task will hence be to define qualitative objectives (performance criteria) in a
functional specification before determining the technical dimensions of the system.
Each criteria shall be developed to express the results to be obtained for the system type
studied.
A typical tool for describing functional characteristics of a rural micro-grid is indicated in
Annex B in the form of functions/performance sheet concerning how to connect the rural
micro-power plant to the application points.
Each rural micro-grid entails aspects specific to the site concerned.
Depending on the characteristics of the needs to be satisfied, the architecture of a rural
micro-grid will be constructed on the basis of the following criteria:
• The number of energy delivery points;
The number of principal and secondary trunk feeders determined in the light of the
distribution of the users at the site, the maximum dimensions of the lines, and system
losses.
• The possibility of having a certain number of opening points available, enabling all or part
of the rural micro-power plant rural micro-grid to be isolated.
As for dimensioning, this will be determined on the basis of such characteristics as:
• The quality level (IEC 62257-2) of energy to be distributed;
• The apparent predictable maximum power of the receivers to be supplied at each delivery
point (peak power);
• The service quality agreed with the users, in particular the maximum voltage drop, which
should not exceed a certain value between the interface with the rural micro-power plant
and the customers;
• The mechanical constraints in the environment concerned.
Figure 2 as an illustration, is a functional diagram of a radial structure for a rural micro-grid.

TS 62257-4 © IEC:2005(E) – 17 –

Micro-power plant
Interface
micro-power plant/micro-grid
(single or three phases)
Individual
Secondary lines
connections
User
User
Main line
IEC  1051/05
Figure 2 – Functional diagram of a radial structure for rural micro-grid
4.6 Functional description of a demand subsystem
Detailed functions to be achieved by a demand subsystem (or rural micro-grid):
Providing an electric power to applications
Consisting of:
1) Interfacing with the distribution system
This function groups everything needed to ensure that the user installation is supplied
from the distribution system, including functions relevant with the contractual commitment
such as payment or metering system.
2) Distributing energy to the appliances
Here are included all the electric functions able to provide, switch on/off electricity from
the distribution system interface to the final user’s application.
NOTE In some projects, this function could include the supply of the appliances (such as lamps for example).
4.7 Constraints to be complied with by production distribution and demand
subsystems
1) Matching the characteristics of the site
This function signifies all constraints, such as geographical, technical, economic or
sociological, as well as human factors specific to the site that the design and performance
of the facilities to be set up will have to satisfy.

– 18 – TS 62257-4  IEC:2005(E)
2) Ensuring protection of persons and assets
The equipment shall be designed to control risks to individuals, operators or third parties.
In addition, they shall be protected from the faults that may occur on the different parts of
the installation.
3) Minimizing special maintenance to make energy available
That means:
• making easy installation;
• facilitating operating conditions;
• facilitating maintenance;
• facilitating dismantling;
• facilitating expansion.
For reasons of cost, it is imperative that the installation can continue to operate without
requiring frequent intervention by specialists.
4) Complying with regulations
This function groups together all the technical and legal constraints t
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