IEC TS 62933-5-1:2017

IEC TS 62933-5-1 ®
Edition 1.0 2017-07
TECHNICAL
SPECIFICATION
colour
inside
Electrical energy storage (EES) systems –
Part 5-1: Safety considerations for grid-integrated EES systems – General
specification
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IEC TS 62933-5-1 ®
Edition 1.0 2017-07
TECHNICAL
SPECIFICATION
colour
inside
Electrical energy storage (EES) systems –

Part 5-1: Safety considerations for grid-integrated EES systems – General

specification
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 13.020.30 ISBN 978-2-8322-4565-1

– 2 – IEC TS 62933-5-1:2017  IEC 2017
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Basic guidelines for safety aspects of EES systems . 17
5 Hazard considerations for EES systems . 17
5.1 Electrical hazards . 17
5.2 Mechanical hazards . 18
5.3 Other hazards . 19
5.3.1 Explosion hazards . 19
5.3.2 Hazards arising from electrical, magnetic, and electromagnetic fields . 19
5.3.3 Fire hazards . 19
5.3.4 Temperature hazards . 21
5.3.5 Chemical hazards . 21
5.3.6 Unsuitable working conditions. 22
6 EES system risk assessment . 22
6.1 EES system structure. 22
6.1.1 General characteristics . 22
6.1.2 Specific characteristics . 22
6.2 Description of storage conditions . 23
6.2.1 Types of grids . 23
6.2.2 Type of applications . 23
6.2.3 Location . 23
6.2.4 Vulnerable elements . 24
6.2.5 Special provisions for EES systems in generally accessible locations . 24
6.2.6 Sources of external aggression . 24
6.2.7 Unattended operation . 24
6.2.8 Unintentional islanding . 24
6.3 Risk analysis. 25
6.3.1 General . 25
6.3.2 Risk considerations . 26
6.3.3 System level risk analysis . 27
7 Requirements necessary to reduce risks . 27
7.1 General measures to reduce risks . 27
7.2 Preventive measures against damage to neighbouring inhabitants . 29
7.3 Preventive measures against damage to workers and residents . 30
7.3.1 Protection from electrical hazards . 30
7.3.2 Protection from mechanical hazards . 31
7.3.3 Protection from other hazards . 31
7.4 Over current protection design . 34
7.5 EES system disconnection and shutdown . 35
7.5.1 General . 35
7.5.2 Grid-disconnected state . 36

7.5.3 Stopped state . 36
7.5.4 EES system shutdown . 36
7.5.5 Cyber security . 37
7.5.6 Partial disconnection . 37
7.5.7 Equipment guidelines for emergency shutdown . 37
7.6 Preventive maintenance . 38
7.7 Staff training . 38
7.8 Safety design . 39
7.8.1 General . 39
7.8.2 Initial safety design and subsequent design revision . 39
7.8.3 Design revision for minor and major system changes . 40
8 System testing . 40
8.1 General . 40
8.2 Auxiliary system malfunction . 42
8.3 EES control subsystem malfunction . 42
8.4 EES system internal communication malfunction. 42
8.5 EES system external communication malfunction . 43
9 Guidelines and manuals . 43
Annex A (informative) Main risks of different storage technologies . 45
A.1 Pumped hydro storage . 45
A.2 Flywheel . 45
A.3 Secondary batteries . 46
A.4 Hydrogen and synthetic natural gas . 47
A.5 Other EES system technologies . 48
Bibliography . 49

Figure 1 – General description of the approach to address hazards in EES systems . 17
Figure 2 – Islanding of the EES system . 25
Figure 3 – Iterative checking sequence in general risk assessment procedures . 28
Figure 4 – General risk reduction measures to minimize hazards . 29
Figure 5 – Damage propagation from an incident to a big accident, and layered
measures to minimize damages . 29
Figure 6 – Examples of different EES system architectures. 36
Figure 7 – Initial safety design and design revision . 39
Figure 8 – EES system architecture in the two main EESS configurations . 41

Table A.1 – Main risk scenarios for pumped hydro storage . 45
Table A.2 – Main risk scenarios for flywheel . 46
Table A.3 – Example of main risk scenarios for lithium-ion batteries . 47
Table A.4 – Main risk scenarios for hydrogen storage . 48

– 4 – IEC TS 62933-5-1:2017  IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL ENERGY STORAGE (EES) SYSTEMS –

Part 5-1: Safety considerations for grid-integrated EES systems –
General specification
FOREWORD
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The main task of IEC technical committees is to prepare International Standards. In
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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 62933-5-1, which is a technical specification, has been prepared by IEC technical
committee TC 120: Electrical Energy Storage (EES) Systems.

The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
120/89/DTS 120/100/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 document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62933 series, published under the general title Electrical energy
storage (EES) systems, 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.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
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– 6 – IEC TS 62933-5-1:2017  IEC 2017
INTRODUCTION
Many governments' plans for how electricity will be generated and managed in the future have
been determined. Such current plans cannot be implemented without long-term storage with
capacities in the multi-MWh range.
There are a number of types of storage technologies that have emerged. Examples of these
technologies are pumped hydro storage (PHS), electrochemical batteries, flywheel storage
systems and hydrogen and synthetic natural gas (SNG). Pumped hydro storage has been
widely used in terms of the total amount of the stored energy. A flywheel is a model of kinetic
energy storage with a high power density, excellent cycle stability and long life. While some
flywheels are intended for short term operation, others can operate over longer periods of
time of up to a few hours. Batteries require development primarily to decrease cost, and for
some technologies to increase energy density as well. Hydrogen and synthetic natural gas
(SNG) added to natural gas are likely to be essential elements of future electric grids because
of their energy storage duration and capacity. Hydrogen and SNG should be further
researched and developed across a broad front, including physical facilities, interactions with
existing uses of gas for supply and distribution network, optimal chemical processes, safety,
reliability and efficiency. The IEC White Paper “Electrical Energy Storage” (2011-12) may
provide further background information on concerned EES systems.
The IEC expects to keep pace, as in other areas in the past, with the need for international
consensus standards for the safety of new storage technologies. It encourages regulators to
anticipate the requirement to guarantee the safety of these technologies, and to contribute to
shaping suitable international standards upon which harmonized regulations may be based.
For mature EES systems various IEC standards exist covering technical features, testing and
system integration. For other technologies there are only a few standards, covering special
topics.
Up to now no general standard addressing safety for EES system integration into an electrical
grid has been developed.
The rapid growth and the new technologies involved in electrical energy storage in the near
future, as well as their installation by consumers will impose particular requirements for safety.
At the same time, society and governments will need assurance of safety before the much-
needed systems can be deployed.
This document stands as a decisive step towards the gradual alignment with specific
technologies and applications concerning the safety of packaged or site-assembled grid-
integrated EES system.
ELECTRICAL ENERGY STORAGE (EES) SYSTEMS –

Part 5-1: Safety considerations for grid-integrated EES systems –
General specification
1 Scope
This part of IEC 62933, which is a Technical Specification, specifies safety considerations
(e.g. hazards identification, risk assessment, risk mitigation) applicable to EES systems
integrated with the electrical grid.
This document provides criteria to foster the safe application and use of electric energy
storage systems of any type or size intended for grid-integrated applications
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 62933-1 , Electrical energy storage (EES) systems – Part 1: Terminology
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62933-1 and the
following 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
accumulation subsystem
storage subsystem
EESS subsystem, comprising at least one electrical energy storage, where the energy is
stored in some form
Note 1 to entry: Mechanical energy, electrochemical energy, electromagnetic energy are frequent forms of stored
energy.
Note 2 to entry: Generally (see Figure 8), the accumulation subsystem is connected to the power conversion
subsystem that performs the necessary power conversion to electrical energy; however, in some cases, a power
conversion is embedded in the accumulation subsystem (e.g. in electrochemical secondary cells the energy is
directly available in the electrical form).
___________
Under preparation. Stage at the time of publication: IEC CDV 62933-1:2017.

– 8 – IEC TS 62933-5-1:2017  IEC 2017
3.2
auxiliary POC
EES system point of connection (POC) with the electric power system used to feed the
auxiliary subsystem, only if the primary POC is not used to feed each subsystem
Note 1 to entry: Generally, an auxiliary POC can be replaced with another source of electrical energy (e.g. a
diesel generator).
Note 2 to entry: The control subsystem is normally fed by the auxiliary subsystem and, therefore, by the auxiliary
POC.
3.3
auxiliary subsystem
EESS subsystem containing equipment intended to perform particular functions additional to
storing/extracting electrical energy which is done in the primary subsystem
Note 1 to entry: Generally (see Figure 8) the auxiliary subsystem is connected to the auxiliary POC through the
auxiliary connection terminal.
Note 2 to entry: The equipment of the auxiliary subsystem (auxiliary equipment) is normally indispensable for
setting up all the EESS operational states and assessing the correct performance (operation) of the primary and
control subsystems during any operating mode.
Note 3 to entry: The auxiliary subsystem can be configured to take the energy from the primary subsystem (see
Figure 8).
3.4
auxiliary subsystem de-energized
condition of service in which an auxiliary subsystem of the EES system does not have any
energy source within the subsystem to feed the auxiliary equipment and is not connected to
an external source of energy
Note 1 to entry: In this state the auxiliary subsystem is not fed by a possible UPS.
Note 2 to entry: “UPS” is defined in IEC 62040-1:2008, 3.1.1.
3.5
communication subsystem
EESS subsystem containing an arrangement of hardware, software, and propagation media to
allow the transfer of messages from one EESS component/subsystem to another, including
the data interface with external links
[SOURCE: IEC TS 62443-1-1:2009, 3.2.25, modified – the original definition has been
particularized for the EES system.]
3.6
control subsystem
EESS subsystem serving for monitoring and controlling the EESS, by including all equipment
and functions for acquisition, processing, transmission, and display of the necessary process
information
Note 1 to entry: Generally (see Figure 8) the control subsystem may be connected to the communication interface
and it comprises at least the management subsystem, the communication subsystem and the protection subsystem.
Note 2 to entry: The control subsystem is normally fed by the auxiliary subsystem.
[SOURCE: IEC TS 62351-2:2008, 2.2.195, modified – the second part of the original definition
has been particularized for the EES system architecture, the first part of the original definition
and notes to entry have been deleted.]
3.7
dead, adj.
DEPRECATED: de-energized, adj.
at an electric potential equal to or not significantly different from that of earth at the worksite

Note 1 to entry: This entry was numbered 651-01-15 in IEC 60050-651:1999.
[SOURCE: IEC 60050-651:2014, 651-21-09]
3.8
duty-cycle of the EES system
combination of controlled phases (charge phase, pause, discharge phase, etc.) starting from
an initial state of charge and ending at a final state of charge, used in the EES system
characterization, specification and testing for a certain operating mode
3.9
EESS module
EESS unit
part of an EES system, which is itself an EES system
Note 1 to entry: The EESS module is a specific EESS subsystem.
Note 2 to entry: In an EESS module the terminals, auxiliary and control subsystems may be absent; they may be
centralized at EES system level.
3.10
EESS subsystem
part of an EES system, which is itself a system
Note 1 to entry: A subsystem is normally at a lower indenture level than the EES system of which it is a part.
[SOURCE: IEC 60050-192:2015, 192-01-04, modified – the original definition has been
particularized for the EES system.]
3.11
electrical energy storage
EES
installation able to absorb electrical energy, to store it for a certain amount of time and to
release electrical energy during which energy conversion processes may be included
EXAMPLE A device that absorbs AC electrical energy to produce hydrogen by electrolysis, stores the hydrogen,
and uses that gas to produce AC electrical energy, is an electrical energy storage.
Note 1 to entry: The term “electrical energy storage” may also be used to indicate the activity of an apparatus
described in the definition of this term during the performance of its own functionality.
Note 2 to entry: The term “electrical energy storage” should not be used to designate a grid-connected
installation; "electrical energy storage system" is the appropriate term.
3.12
electrical energy storage system
EES system
EESS
grid-connected installation with defined electrical boundaries, comprising at least one
electrical energy storage, which extracts electrical energy from an electric power system,
stores this energy internally in some manner and injects electrical energy into an electrical
power system and which includes civil engineering works, energy conversion equipment and
related ancillary equipment
Note 1 to entry: The EES system is controlled and coordinated to provide services to the electric power system
operators or to the electric power system users.
Note 2 to entry: In some cases, an EES system may require an additional energy source (non electrical) during its
discharge, providing more energy to the electric power system than the energy it stored (compressed air energy
storage is a typical example where thermal energy is requested).

– 10 – IEC TS 62933-5-1:2017  IEC 2017
3.13
electrical installation
assembly of electrical equipment which is used for the generation, transmission, conversion,
distribution and/or use of electric energy
Note 1 to entry: The electrical installation includes energy sources such as batteries, capacitors and all other
sources of stored electric energy.
Note 2 to entry: This entry was numbered 651-01-04 in IEC 60050-651:1999.
[SOURCE: IEC 60050-651:2014, 651-26-01]
3.14
emergency stop
operating procedure intended to stop, as quickly as possible, an operation which has become
dangerous
3.15
end of service life
life cycle stage of the EES system starting when it is removed from its intended use stage
Note 1 to entry: According to ISO Guide 64:2008, the sentence “removed from its intended use stage” does not
mean “dismantled”. In fact, at the end of the service life, the EES system can either be reused/recovered or
disposed of (after treatment, whenever necessary), possibly after dismantling and further processes.
Note 2 to entry: The term ”life-cycle” is defined in ISO Guide 64:2008, 2.5, and in IEC 60050-901:2013, 901-07-12,
as “life cycle”.
[SOURCE: IEC 60050-904:2014, 904-01-17, modified – the original definition has been
particularized for the EES system and notes to entry have been added]
3.16
end of service life values
value of unit parameters of an EES system that designate the end of service life
Note 1 to entry: EES system unit parameters, such as rated energy capacity, step response performances, rated
powers, are generally determined by consensus between the user and the supplier.
3.17
energized, adj.
live, adj.
at an electric potential different from that of earth at the worksite and which presents an
electrical hazard
Note 1 to entry: A part is energized when it is electrically connected to a source of electric energy. It can also be
energized when it is electrically charged and/or under the influence of an electric or magnetic field.
Note 2 to entry: This entry was numbered 651-01-14 in IEC 60050-651:1999. It has been modified as follows: The
word “significant” has been removed as it could not be quantified.
[SOURCE: IEC 60050-651:2014, 651-21-08]
3.18
expected service life
T
SL
design duration for which the EES system unit parameters are greater than end of service life
values at continuous operating conditions
Note 1 to entry: Generally this duration is expressed in years or in duty-cycles.
[SOURCE: IEC 62477-1:2012, 3.14, modified – the original definition has been particularized
for the EES system and the note to entry has been added]

3.19
explosion hazard
condition of an EES system with a potential for an undesirable consequence from explosion
Note 1 to entry: Explosion hazard is a condition where danger exists because hazardous substances that are
present may react (e.g., detonate, deflagrate) in a mishap with potential unacceptable effects (e.g., death, injury,
damage) to people, property, operational capability, or the environment.
3.20
failure mode
DEPRECATED: fault mode
manner in which failure occurs
Note 1 to entry: A failure mode may be defined by the function lost or other state transition that occurred.
[SOURCE: IEC 60050-192:2015, 192-03-17]
3.21
failure modes and effects analysis
FMEA
DEPRECATED: fault mode and effects analysis
qualitative method of analysis that involves the study of possible failure modes and faults in
sub items, and their effects at various indenture levels
Note 1 to entry: The term "fault mode and effects analysis" in IEC 60050-191:1990 (now withdrawn; replaced by
IEC 60050-192:2015) is deprecated, since a fault (192-04-01) is a state and cannot logically have a mode, whereas
a failure mode (192-03-17) is a change of state.
[SOURCE: IEC 60050-192:2015, 192-11-05]
3.22
failure modes, effects and criticality analysis
FMECA
DEPRECATED: fault mode, effects and criticality analysis
quantitative or qualitative method of analysis that involves failure modes and effects analysis
together with a consideration of the probability of the failure mode occurrence and the
severity of the effects
Note 1 to entry: The term "fault mode, effects and criticality analysis" in IEC 60050-191:1990 (now withdrawn;
replaced by IEC 60050-192:2015) is deprecated, since a fault (192-04-01) is a state and cannot logically have a
mode, whereas a failure mode (192-03-17) is a change of state.
[SOURCE: IEC 60050-192:2015, 192-11-06]

3.23
fault tree analysis
FTA
deductive analysis using fault trees
Note 1 to entry: See also fault tree (192-11-07).
[SOURCE: IEC 60050-192:2015, 192-11-08]
3.24
fire hazard
condition of an EES system with a potential for an undesirable consequence from fire
Note 1 to entry: Fire hazard is a condition where danger exists because flammable solids, liquids, gases or their
mixture are present in quantities/concentrations that may result in uncontrolled combustion with potential for death,
injury, or damage to people, property, operational capability, or the environment.

– 12 – IEC TS 62933-5-1:2017  IEC 2017
[SOURCE: ISO 13943:2008, 4.112, modified – the original definition has been particularized
for the EES system and note 1 to entry has been added.]
3.25
grid-connected state
operating state in which the EES system is connected to the primary POC
3.26
grid-disconnected state
operating state in which the EES system is disconnected from the primary POC
3.27
harm
physical injury or damage to persons, property, and livestock
[SOURCE: IEC 60050-903:2013, 903-01-01]
3.28
hazard
potential source of harm
Note 1 to entry: In English, the term “hazard” can be qualified in order to define the origin of the hazard or the
nature of the expected harm (e.g. “electric shock hazard”, “crushing hazard”, “cutting hazard”, “toxic hazard”, “fire
hazard”, “drowning hazard”).
Note 2 to entry: In French, the synonym “risque” is used together with a qualifier or a complement to define the
origin of the hazard or the nature of the expected harm (e.g. “risque de choc électrique”, “risque d'écrasement”,
“risque de coupure”, “risque toxique”, “risque d'incendie”, “risque de noyade”).
Note 3 to entry: In French, the term “risque” also denotes the combination of the probability of occurrence of harm
and the severity of that harm, in English “risk” (see 903-01-07).
[SOURCE: IEC 60050-903:2013, 903-01-02]
3.29
hazard and operability studies
HAZOP studies
structured and systematic technique for examining a defined system with the objective of:
identifying potential hazards in the system (the hazards involved may include both those
essentially relevant only to the immediate area of the system and those with a much wider
sphere of influence, for example some environmental hazards) and identifying potential
operability problems with the system and in particular identifying causes of operational
disturbances and production deviations likely to lead to non conforming products
3.30
hazardous substance
hazardous material
substance which can affect human health or the environment with an immediate or retarded
effect or is capable of posing an unacceptable risk to health, safety, property or to the
environment
Note 1 to entry: It may concern other substances than those officially recognized as such in existing hazardous
material classification systems, for example, Global Harmonized System (GHS), Transport of Dangerous Goods
(TDG).
3.31
intentional islanding
intentional island
island that is intentionally created, usually to restore or maintain power to a section of the
utility grid affected by a fault

Note 1 to entry: The generation and loads may be any combination of customer-owned and utility-owned, but
there is an implicit or explicit agreement between the controlling utility and the operators of customer-owned
generation for this situation.
Note 2 to entry: The term “island” is defined in IEC 60050-617:2009, 617-04-12.
[SOURCE: IEC 62116:2014, 3.6, modified – the note 2 to entry has been added.]
3.32
life cycle
consecutive and interlinked stages of a product system, from raw material acquisition or
generation from natural resources to the final disposal
[SOURCE: IEC 60050-901:2013, 901-07-12]
3.33
long duration application
long term application
energy intensive application
EES system application generally not very demanding in terms of step response
performances but with long charge and discharge phases at variable powers
Note 1 to entry: Reactive power exchange with the electric power system may be present along with the active
power exchange
Note 2 to entry: The term “electric power system” is defined in IEC 60050-601:1985, 601-01-01.
3.34
management subsystem
EESS subsystem providing the functionality needed for the safe, effective and efficient EES
system operation
3.35
mechanical hazard
condition of an EES system with a potential for an undesirable consequence from physical
force
Note 1 to entry: Mechanical hazard is a condition where physical factors may give rise to injury due to the
mechanical properties of products/product parts.
Note 2 to entry: The definition has been formulated along the same lines as that in ISO 13943:2008, 4.112.
3.36
modularity
property of an EES system that specifies the extent to which it has been composed out of
separate parts called EESS modules
[SOURCE: ISO/IEC 14543-2-1:2006, 3.2.9, modified – the original definition has been
particularized for the EES system]
3.37
operating state
particular combination of EESS element states bound to a specific operation of an EES
system during a required time
3.38
personal protective equipment
PPE
any device or appliance designed to be worn or held by an individual for protection against
one or more health and safety hazards whilst performing live working

– 14 – IEC TS 62933-5-1:2017  IEC 2017
Note 1 to entry: This entry was numbered 651-07-01 in IEC 60050-651:1999. It has been modified for greater
clarity on the role of PPE.
[SOURCE: IEC 60050-651:2014, 651-23-01]
3.39
point of connection
POC
reference point on the electric power system where an EES system is connected
Note 1 to entry: An EES system may have several POCs arranged in two different classes: primary POC and
auxiliary POC. From an auxiliary POC it is not possible to charge electrical energy in order to store it internally and,
finally, to discharge it to the electric power system, but a primary POC can be used to feed the auxiliary subsystem
and the control subsystem. In the absence of an auxiliary POC, the primary POC can be named simply as POC.
Note 2 to entry: The term ”electric power system” is defined in IEC 60050-601: 1985, 601-01-01.
[SOURCE: IEC 60050-617:2009, 617-04-01, modified – the original definition has been
particularized for the EES system and notes to entry have been added.]
3.40
power conversion subsystem
EESS subsystem where energy is converted from the available form at the output of the
accumulation subsystem of the EES system to electrical energy with the same characteristics
(voltage, frequency etc.) present at the primary POC
Note 1 to entry: Generally (see Figure 8) the power conversion subsystem is connected to the accumulation
subsystem and to the primary POC through the primary connection terminal.
3.41
primary POC
point of connection where the EES system charges electrical energy from the electric power
system, in order to store it internally and, finally, discharge it to the electric power system
Note 1 to entry: Generally, the primary POC is connected with the EES system's primary subsystem through the
primary connection terminal.
Note 2 to entry: The term ”electric power system” is defined in IEC 60050-601:1985, 601-01-01.
3.42
primary subsystem
EESS subsystem consisting of the components/subsystems that are directly responsible for
storing electrical energy and extracting electrical energy
Note 1 to entry: Generally the primary subsystem is connected to the primary POC and comprises at least the
accumulation subsystem and the power conversion subsystem (see Figure 8).
3.43
protection subsystem
EESS subsystem containing an arrangement of one or more protection equipment, and other
devices intended to perform one or more specified protection functions
Note 1 to entry: The protection subsystem includes one or more protection equipment, instrument transformer(s),
transducers, wiring, tripping circuit(s), auxiliary supply(ies). Depending upon the principle(s) of the protection
subsystem, it may include one end or all ends of the protected section and, possibly, automatic reclosing
equipment.
Note 2 to entry: The switches and fuses are excluded.
[SOURCE: IEC 60050-448:1995, 448-11-04,modified – the original definition has been
particularized for the EES system, and note 2 to entry has been generalized to exclude all the
switches and fuses and not only the circuit breakers.]

3.44
protective measure
measure intended to achieve adequate risk reduction, implemented by the designer (inherent
design, safeguarding and complementary protective measures, information for use) and by
the user (organization: safe working procedures, supervision, training; permit-to-work systems;
provision and use of additional safeguards; use of personal protective equipment)
[SOURCE: IEC 60050-903:2013, 903-01-17]
3.45
reasonably foreseeable misuse
use of a product, process or service in a way not intended by the supplier, but which may
result from readily predictable human behaviour
[SOURCE: IEC 60050-903:2013, 903-01-14]
3.46
risk
combination of the probability of occurrence of harm and the severity of that harm
Note 1 to entry: In French, the term “risque” also denotes the potential source of harm, in English “hazard” (see
903-01-02).
[SOURCE: IEC 60050-903:2013, 903-01-07]
3.47
risk analysis
systematic use of available information to identify hazards and to estimate the risk
[SOURCE: IEC 60050-903:2013, 903-01-08]
3.48
risk assessment
overall process comprising a risk analysis and a risk evaluation
[SOURCE: IEC 60050-903:2013, 903-01-10]
3.49
risk evaluation
procedure based on the risk analysis to determine whether the tolerable risk has been
achieved
[SOURCE: IEC 60050-903:2013, 903-01-09]
3.50
safety
EES system freedom from unacceptable risk
Note 1 to entry: In standardization the safety of products, processes and services is generally considered with a
view to achieve the optimum balance of a number of factors, including non-technical factors such as human
behaviour, that wi
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