IEC TS 62898-1:2017

IEC TS 62898-1 ®
Edition 1.0 2017-05
TECHNICAL
SPECIFICATION
colour
inside
Microgrids –
Part 1: Guidelines for microgrid projects planning and specification
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IEC TS 62898-1 ®
Edition 1.0 2017-05
TECHNICAL
SPECIFICATION
colour
inside
Microgrids –
Part 1: Guidelines for microgrid projects planning and specification

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.240.01 ISBN 978-2-8322-4360-2

– 2 – IEC TS 62898-1:2017 © IEC 2017
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 General principles . 13
4.1 General . 13
4.2 Preliminary study . 14
4.3 Overall microgrid planning and design process . 14
5 Purpose and application of microgrids . 15
5.1 Application classification . 15
5.2 Application of non-isolated microgrids . 15
5.3 Application of isolated microgrids . 15
6 Resource analysis and generation forecast . 16
6.1 Resource analysis. 16
6.1.1 General . 16
6.1.2 Non-dispatchable resource analysis . 16
6.1.3 Dispatchable resource analysis . 17
6.2 Generation forecast . 17
6.2.1 General . 17
6.2.2 Technical requirements . 17
6.2.3 Data processing . 18
7 Load forecast . 18
7.1 General . 18
7.2 Load analysis . 18
7.3 Classification of load forecast . 19
7.4 Technical requirements . 19
8 Distributed energy resource planning . 20
8.1 Ratio of renewable energy . 20
8.2 Renewable generation configuration . 20
8.3 Energy storage . 20
8.4 Electric power and energy balancing . 20
8.5 Dispatchable generation configuration . 20
9 Microgrid power system planning . 21
9.1 Voltage level . 21
9.2 Typical topology of a microgrid . 21
9.2.1 Typical topology for a non-isolated microgrid . 21
9.2.2 Typical topology for an isolated microgrid . 23
9.3 Electrical parameter calculations. 23
10 Technical requirements for DER in microgrids . 23
10.1 General . 23
10.2 Technical requirements for DER in grid-connected mode . 24
10.3 Technical requirements for DER in isolated microgrids and island mode of
non-isolated microgrids . 24
11 Technical requirements for distribution lines in microgrids . 24
12 Technical requirements for microgrid connection to distribution networks . 24

12.1 General . 24
12.2 Interface protection . 24
12.3 Microgrid earthing . 25
12.3.1 General . 25
12.3.2 Technical requirements for microgrid earthing . 25
12.4 Power quality at POC . 25
12.4.1 General . 25
12.4.2 Power quality monitoring . 25
13 Technical requirements for control, protection and communication systems . 26
13.1 Microgrid control . 26
13.1.1 General . 26
13.1.2 Control scheme . 26
13.2 Protection relays and automatic protection devices . 26
13.2.1 General . 26
13.2.2 DER component protection . 27
13.2.3 Component protection for all users in a microgrid . 27
13.2.4 Load shedding in a microgrid . 27
13.3 Microgrid communication . 27
13.3.1 Communication within microgrid subsystem . 27
13.3.2 Microgrid communication with connected distribution system . 27
13.4 Information exchange. 27
14 Evaluation of microgrid projects . 28
14.1 General . 28
14.2 Reliability of power supply . 28
14.3 Economic benefits. 28
14.4 Environmental benefits . 28
14.5 Scalability . 28
14.6 Integration to the wider electric power system . 28
Annex A (informative) Business use case A Guarantee a continuity in load service by
islanding with microgrids . 29
A.1 General . 29
A.2 Purpose . 29
A.3 Objectives . 29
Annex B (informative) Business use case B Optimize local resources to provide
services to customers inside the microgrid . 30
B.1 General . 30
B.2 Purpose . 30
B.3 Objectives . 30
Annex C (informative) Business use case C Electrify remote areas using renewable
energy sources . 31
C.1 General . 31
C.2 Purpose . 31
C.3 Objectives . 31
C.4 Basic functions . 31
C.5 Advanced functions . 31
Annex D (informative) Business use case D Optimize local resources to provide
services to the grid/disaster preparedness . 32
D.1 General . 32
D.2 Scope . 32

– 4 – IEC TS 62898-1:2017 © IEC 2017
D.3 Objectives . 32
D.4 Basic functions . 32
D.5 Advanced functions . 32
Bibliography . 33

Figure 1 – Overall microgrid planning and design process . 14
Figure 2 – Single bus structure microgrid . 21
Figure 3 – Multiple bus structure microgrid . 22
Figure 4 – Multilevel structure microgrid . 22
Figure 5 – Typical topology for an isolated microgrid . 23

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MICROGRIDS –
Part 1: Guidelines for microgrid
projects planning and specification

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
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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
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• 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 TS 62898, which is a Technical Specification, has been prepared by IEC technical
committee 8: Systems aspects for electrical energy supply.

– 6 – IEC TS 62898-1:2017 © IEC 2017
The text of this Technical Specification is based on the following documents:
Enquiry draft Report on voting
8/1445/DTS 8/1460/RVDTS
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 document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62898 series, published under the general title Microgrids, can be
found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• 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
Microgrids can serve different purposes depending on the primary objectives of their
applications. They are usually seen as means to manage reliability of supply in a grid
contingency and local optimization of energy supply by controlling distributed energy
resources (DER). Microgrids also present a way to provide electricity supply in remote areas
and to use clean and renewable energy as a systemic approach for rural electrification.
This part of IEC 62898 defines the guidelines for the general planning and design of
microgrids, and IEC TS 62898-2 defines the general technical requirements for operation
and control of microgrids.
This document mainly covers the following issues:
• determination of microgrid purpose and application;
• preliminary study used for microgrid planning, including resource analysis, load forecast,
DER planning and microgrid power system planning;
• principles of microgrid technical requirements that should be specified during planning
stage;
• microgrid evaluation to select an optimal planning scheme for a microgrid project.
IEC TS 62898-2 mainly covers the following issues:
• operation requirements and control targets of microgrids under different operation modes;
• basic control strategies and methods under different operation modes;
• requirements of energy storage, monitoring and communication under different operation
modes;
• power quality.
Microgrids can be stand-alone or be a sub-system of the smart grid. The technical
requirements in this document and in IEC TS 62898-2 are intended to be consistent and in
line with:
• system requirements from IEC System Committee Smart Energy,
• technical requirements from IEC 62786 for connection of generators intended to be
operated in parallel with the microgrid,
• basic rules from IEC TC 64 and TC 99 for safety and quality of power distribution
(essentially selectivity, through coordination of protective devices) in installations,
• basic rules from IEC TC 77/SC 77A for electromagnetic compatibility (EMC) issues,
• IEC TS 62257 (all parts) with respect to rural electrification,
• IEC TS 62749 with respect to power quality.
Local laws and regulations can overrule the requirements of this document.

___________
Under preparation. Stage at the time of publication: IEC CD 62898-2:2017.

– 8 – IEC TS 62898-1:2017 © IEC 2017
MICROGRIDS –
Part 1: Guidelines for microgrid
projects planning and specification

1 Scope
The purpose of this part of IEC 62898, which is a Technical Specification, is to provide
guidelines for microgrid projects planning and specification. Microgrids considered in this
document are alternating current (AC) electrical systems with loads and distributed energy
resources (DER) at low or medium voltage level. This document does not cover direct current
(DC) microgrids.
Microgrids are classified into isolated microgrids and non-isolated microgrids. Isolated
microgrids have no electrical connection to a wider electric power system. Non-isolated
microgrids can act as controllable units to the electric power system and can operate in the
following two modes:
• grid-connected mode;
• island mode.
This document will cover the following areas:
• microgrid application, resource analysis, generation forecast, and load forecast;
• DER planning and microgrid power system planning;
• high level technical requirements for DER in microgrids, for microgrid connection to the
distribution system, and for control, protection and communication systems;
• evaluation of microgrid projects.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60038, IEC standard voltages
IEC 60364 (all parts), Low voltage electrical installations
IEC 61936 (all parts), Power installations exceeding 1 kV AC
IEC TS 62749, Assessment of power quality - Characteristics of electricity supplied by public
networks
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
black start
start-up of an electric power system from a blackout through internal energy resources
[SOURCE: IEC 60050-617:2009, 617-04-24]
3.2
busbar
low-impedance conductor to which several electric circuits can be connected at separate
points
Note 1 to entry: In many cases, the busbar consists of a bar.
[SOURCE: IEC 60050-151:2001, 151-12-30]
3.3
converter
device for changing one or more characteristics associated with electric energy
Note 1 to entry: Characteristics associated with energy are for example voltage, number of phases and frequency
including zero frequency.
[SOURCE: IEC 60050-151:2001, 151-13-36, modified – The words "electric energy" have
been removed from the term]
3.4
combined heat and power
CHP
production of heat which is used for non-electrical purposes and also for the generation of
electric energy
Note 1 to entry: Conventional power plants emit the heat produced as a useless byproduct of the generation of
electric energy into the environment. With combined heat and power, the excess heat is captured for domestic or
industrial heating purposes.
[SOURCE: IEC 60050-602:1983, 602-01-24, modified – The abbreviated term "CHP" has been
added, as well as the note to entry. The definition has been rephrased]
3.5
earth
ground
part of the earth which is in electric contact with an earth electrode and whose electric
potential is not necessarily equal to zero
[SOURCE: IEC 60050-195:1998, 195-01-03, modified – The adjective "local" has been
removed from the term]
3.6
earthing arrangement
grounding arrangement
electric connections and devices involved in the earthing of a system, an installation and
equipment
[SOURCE: IEC 60050-195:1998, 195-02-20, modified – The deprecated term has been
removed]
– 10 – IEC TS 62898-1:2017 © IEC 2017
3.7
earthing conductor
grounding conductor
conductor which provides a conductive path, or part of the conductive path, between a given
point in a system or in an installation or in equipment and an earth electrode
[SOURCE: IEC 60050-195:1998, 195-02-03, modified – The deprecated term has been
removed]
3.8
electromagnetic compatibility
EMC
ability of an equipment or system to function satisfactorily in its electromagnetic environment

without introducing intolerable electromagnetic disturbances to anything in that environment
[SOURCE: IEC 60050-161:1990, 161-01-07]
3.9
distributed energy resources
DER
generators, including loads having a generating mode (such as electrical energy storage
systems), connected to the low or medium voltage network, with their auxiliaries, protection
and connection equipment, if any
3.10
distributed generation
generation of electric energy by multiple sources which are connected to the power
distribution system
[SOURCE: IEC 60050-617:2009, 617-04-09, modified – The other preferred terms "embedded
generation" and "dispersed generation" have been deleted]
3.11
distribution network
electrical facility and its components including poles, transformers, disconnects, relays,
isolators, and wires that are owned or operated by an electrical utility for the purpose of
distributing electrical energy from substations to customers
Note 1 to entry: Usually, the distribution network operates up to a nominal voltage of 35 kV.
3.12
in-plant point of coupling
IPC
point on a network inside a system or an installation, electrically nearest to a particular load,
at which other loads are, or could be, connected
Note 1 to entry: The IPC is usually the point for which electromagnetic compatibility is to be considered.
[SOURCE: IEC 61000-2-4:2002, 3.1.7]
3.13
interface switch
switch (circuit breaker, switch or contactor) installed in the microgrid, for separating the part(s)
of the microgrid containing at least one generation unit from the distribution network
3.14
interruptible load
load of particular consumers which, according to contract, can be disconnected by the supply
undertaking for a limited period of time

[SOURCE: IEC 60050-603:1986, 603-04-41]
3.15
island
part of an electric power system, that is disconnected from the remainder of the
interconnected system, but remains energized
Note 1 to entry: An island can be either the result of the action of automatic protections or the result of a
deliberate action.
Note 2 to entry: The generation and loads can be any combination of customer-owned and utility-owned.
[SOURCE: IEC 60050-617:2009, 617-04-12, modified – “in an electric power system” has
been deleted. The second note to entry has been added]
3.16
isolated microgrid
group of interconnected loads and distributed energy resources forming a local electric power
system at distribution voltage levels not currently capable of being connected to a wider
electric power system
Note 1 to entry: Isolated microgrids are usually designed for geographical islands or for rural electrification.
Note 2 to entry: Microgrid capable of being connected to a wider electric power system is also called non-isolated
microgrid.
3.17
low voltage
LV
a set of voltage levels used for the distribution of electricity and whose upper limit is generally
accepted to be 1 000 V for alternating current
[SOURCE: IEC 60050-601:1985, 601-01-26]
3.18
load forecast
estimate of the expected load of a network at a given future date
[SOURCE: IEC 60050-603:1986, 603-01-04]
3.19
load profile
curve representing supplied electric power against time of occurrence to illustrate the
variance in a load during a given time interval
[SOURCE: IEC 60050-617:2009, 617-04-05]
3.20
main switch
switch installed as close as possible to the point of connection, for protection against internal
faults and disconnection of the microgrid from the distribution network
3.21
medium voltage
MV
set of voltage levels lying between low and high voltage
Note 1 to entry: The boundaries between medium- and high-voltage levels overlap and depend on local
circumstances and history or common usage. Nevertheless the band 30 kV to 100 kV frequently contains the
accepted boundary.
– 12 – IEC TS 62898-1:2017 © IEC 2017
[SOURCE: IEC 60050-601:1985, 601-01-28 – The information about the use of this term has
been deleted]
3.22
microgrid
group of interconnected loads and distributed energy resources with
defined electrical boundaries that acts as a single controllable entity and is able to operate in
both grid-connected and island mode
Note 1 to entry: This definition is intended to cover both (utility) distribution microgrids and (customer owned)
facility microgrids.
3.23
microgrid energy management system
system operating and controlling energy resources and loads of the microgrid
3.24
point of connection
POC
reference point on the electric power system where the user’s electrical facility is connected
Note 1 to entry: In this document, point of connection indicates the point where microgrid is connected to the
distribution network.
[SOURCE: IEC 60050-617:2009, 617-04-01, modified – The note to entry has been added]
3.25
generation forecast
forecast of the expected production of the DER in the microgrid
3.26
power quality
characteristics of the electric current, voltage and frequencies at a given point in an electric
power system, evaluate against a set of reference technical parameters
Note 1 to entry: These parameters might, in some cases, relate to the compatibility between electricity supplied in
an electric power system and the loads connected to that electric power system.
[SOURCE: IEC 60050-617:2009, 617-01-05]
3.27
reliability
probability that an electric power system can perform a required function under given
conditions for a given time interval
Note 1 to entry: Reliability quantifies the ability of an electric power system to supply adequate electric service on
a nearly continuous basis with few interruptions over an extended period of time.
Note 2 to entry: Reliability is the overall objective in electric power system design and operation.
[SOURCE: IEC 60050-617:2009, 617-01-01]
3.28
renewable energy
primary energy the source of which is constantly replenished and will not become depleted
Note 1 to entry: Examples of renewable energy are: wind, solar, geothermal, hydropower.
Note 2 to entry: Fossil fuels are non-renewable.
[SOURCE: IEC 60050-617:2009, 617-04-11]

3.29
security
ability of an electric power system to operate in such a way that credible events do not give
rise to loss of load, stresses of system components beyond their ratings, bus voltages or
system frequency outside tolerances, instability, voltage collapse, or cascading
Note 1 to entry: This ability may be measured by one or several appropriate indices.
Note 2 to entry: This concept is normally applied to bulk power systems.
Note 3 to entry: In North America, this concept is usually defined with reference to instability, voltage collapse
and cascading only.
[SOURCE: IEC 60050-617:2009, 617-01-02]
3.30
switch
device for changing the electric connections among its terminals
[SOURCE: IEC 60050-151:2001, 151-12-22]
3.31
under-frequency load shedding
UFLS
process of deliberately disconnecting preselected loads from a power system in response to
under-frequency condition in order to maintain the active power balance of the remainder of
the system
3.32
under-voltage load shedding
UVLS
process of deliberately disconnecting preselected loads from a power system in response to
under-voltage condition in order to maintain the active power balance of the remainder of the
system
4 General principles
4.1 General
The objective of non-isolated microgrids is to improve the supply reliability and optimize the
use of local generation, while the primary objective of isolated microgrids is to supply users in
remote areas where a wider electric power system is not available. Accordingly, identification
of the objective and customer requirements is an essential part of the microgrid planning and
design process.
The main task of the microgrid planning and design is to evaluate the local energy resources,
and to determine the configuration and connecting requirements of distributed energy
resources (DER). As many microgrids may not be built from scratch, when planning, grid
planners should take into consideration the local load profile, energy demand and existing
power supply units. The result of the microgrid planning should be flexible enough to satisfy
the immediate need along with the future demand growth.
It is necessary to first determine the application that the system is intended for. The use case
methodology may provide guidance to determine the optimal design of the microgrid system.
This document provides a procedure for planning and design of a microgrid, specifying the
requirements for the microgrid internal design and external connection.

– 14 – IEC TS 62898-1:2017 © IEC 2017
4.2 Preliminary study
Before a microgrid is planned, it is recommended to carry out a preliminary study to
understand the local needs and perform a technical assessment, which includes the following:
a) energy resource analysis, including local renewable energy resources, energy storage,
fuel sources, existing energy supply and its dispatchability;
b) load profile, load characteristics including dispatchability, and projected future demand
growth;
c) a site survey, including location, size, and configuration of reactive power compensation,
voltage regulation equipment, reactors, transformers, protective and sectionalizing
equipment;
d) local distribution system parameters;
e) provisions for network expansion and future development.
4.3 Overall microgrid planning and design process
Figure 1 is the illustration of the main topics that should be investigated in the microgrid
planning and design process.
IEC
Figure 1 – Overall microgrid planning and design process

5 Purpose and application of microgrids
5.1 Application classification
Different purposes or a combination may be expected for a microgrid, including improved
reliability, economy, and disaster preparedness. The following are use case scenarios for
microgrids (coordinated with IEC TS 62913-2-1 developed by SyC Smart energy; see also
Annexes A to D for details).
a) Microgrids that aim at improving reliability, and securing the energy supply for all or part
of their loads by islanding:
1) Distribution microgrid, for example part of utility grid, campus, activity zone;
2) Facility microgrid, for example microgrids in a customer installation, a military base, a
hospital.
b) Microgrids that aim at providing power to remote areas with lower cost, for example
isolated microgrids in rural electrification, oceanic islands;
c) Microgrids that aim at reducing energy costs for microgrid users in the grid-connected
mode by optimizing the assets such as energy storage, dispatchable loads and generators,
providing ancillary services to the grid;
d) Microgrids that aim at providing disaster-preparedness by optimizing the assets such as
energy storage, dispatchable loads and generators. This kind of microgrids may be built in
natural disaster prone areas, designed for the zone where enhanced power supply is
required for some critical loads, etc.
At the planning stage, the microgrids shall be classified into "non-isolated microgrids" or
"isolated microgrids", considering the availability of a wider electric power system, the
characteristics of the local DER and load pattern. The determining factors also include
requirements of customers for environmental benefit, power quality, reliability and economy in
the microgrid.
The classification should be recognized as an essential step because different purposes, and
requirements envisioned by microgrid planners will lead to different planning schemes.
However, both types of microgrids should abide by the technical requirements in this
document.
5.2 Application of non-isolated microgrids
The non-isolated microgrid is connected to the distribution system through the point of
connection (POC), and can operate in grid-connected mode or island mode. Such a microgrid
should be equipped with necessary energy storage facilities and/or dispatchable generating
units. The non-isolated microgrid emphasizes the use of local resources, including renewable
energy resources, with enough energy storage capacity that can sustain the critical load for a
predetermined period of time in island mode.
In the non-isolated microgrid, the microgrid energy management system (EMS) should be able
to keep track of the operation cost by local generation and prices of energy imported from the
utility grid, in order to reach the optimal operation objectives.
Urban electrification should provide the critical load with energy of a specific power quality
and reliability level. To do so, the non-isolated microgrid shall be able to transfer from one
while having the ability to supply the critical
operation mode to another seamlessly and safely,
load in island mode. Certain equipment to improve power quality and reliability, harmonics
filters and reactive power compensators should be installed in the microgrid.
5.3 Application of isolated microgrids
The isolated microgrid is not connected to the distribution system and thus is permanently
operating in island mode. Such a microgrid is mainly used in areas remote from a wider

– 16 – IEC TS 62898-1:2017 © IEC 2017
electric power system. The isolated microgrid aims at continuous and reliable energy supply
with or without sufficient renewable energy. Therefore, such a microgrid should contain
sufficient energy storage capacity and dispatchable DER.
The isolated microgrid shall keep the power balance by managing generators, energy storage
system as well as demand response.
The microgrid planners should make the economic decision between installing large electric
energy storage versus paying for periodic delivery of fuel.
Scalability of isolated microgrids should be envisaged from the beginning, through
enlargement of the microgrid and/or connectivity of microgrids.
6 Resource analysis and generation forecast
6.1 Resource analysis
6.1.1 General
The proper understanding of the generation potential and other characteristic of the local
energy resources is the first step in microgrid planning. The resource analysis should be
carried out by first considering the non-dispatchable resources and then dispatchable
resources. The non-dispatchable resources are mostly renewable energy, including solar
energy and wind energy; dispatchable resources include biomass, combined heat and power
(CHP), combustion unit, storage, etc. During the preliminary study stage, historical
meteorological data, geographical features, and availability of construction site should be
collected. Modern site assessment techniques should also be utilized to predict the possible
energy generation potential.
6.1.2 Non-dispatchable resource analysis
6.1.2.1 Solar energy resource analysis
Solar energy resources should be assessed based on monthly and yearly solar radiation and
sunshine intensity data, combined with the regional climate conditions, annual change
patterns of solar radiation and sunshine intensity. Indices used in the solar evaluation should
indicate richness and consistency of solar energy.
For photovoltaic generation, the total solar radiation should be taken as an index to assess
the richness of solar energy resources. For solar-thermal power generation, direct radiation
perpendicular to the incident light of the sun should be taken as an index to assess the
richness of solar energy resources.
The analysis and design of solar energy resources and p
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