Static transfer systems (STS) -- Part 1: General and safety requirements

IEC 62310 consists of three parts and applies to free standing a.c. static  transfer systems (STS) intended to ensure the continuity of power to load  by automatically or manually controlled transfer, with or without  interruption, from two or several a.c. independent sources. This part of IEC  62310 concerns general and safety requirements. See future IEC 62310-2  for electromagnetic compatibility (EMC) and futureIEC 62310-3 for the  method of specifying performance and test requirements. This part of IEC  62310 is intended to reduce the risk of fire, electric shock, or injury to  persons from installed equipment subject to installing, operating, and  maintaining the equipment in the manner prescribed by the manufacturer.  This part of IEC 62310 includes requirements for the switching elements,  their control and protective elements, where applicable. This part of IEC  62310 also includes information for the overall integration of the STS and  its accessories into the a.c. power distribution system. Components or  devices necessary for the operation/control/protection/isolation (e.g.  circuitbreakers, fuses, transformers, etc.) of a STS should comply with  the requirements of the relevant IEC standards and are not covered by this  part of IEC 62310. This standard applies to systems up to 1 000 V (a.c.  value) which are intended to be used in single phase or phase-phase or  three phase applications. This standard does not apply to: - devices for  d.c. source switching; - static transfer system using only  electromechanical switching devices intended to be used in emergency  power systems with interruption of the supply to the load during transfer.  This equipment is covered by IEC 60947-6-1; - the automatic switching  devices integrated into UPS covered by IEC 62040 series.

Statische Transferschalter (STS) -- Teil 1: Allgemeine und Sicherheitsanforderungen

Systèmes de transfert statique (STS) -- Partie 1: Exigences générales et règles de sécurité

aux systèmes de transfert statique (STS) à courant alternatif autonomes destinés à assurer la continuité de l'alimentation d'une charge par un transfert manuel ou automatique, avec ou sans coupure, à partir d'au moins deux sources indépendantes à courant alternatif.contient des exigences concernant les éléments de commutation et leur commande ainsi que les éléments de protection, le cas échéant. La présente partie de la EN 62310 contient également des informations relatives à l'intégration globale d'un STS et de ses accessoires dans un réseau de distribution de courant alternatif

Sistemi s statičnim prenosom (STS) – 1. del: Splošne in varnostne zahteve (IEC 62310-1:2005)

General Information

Status
Published
Publication Date
28-Feb-2006
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Mar-2006
Due Date
01-Mar-2006
Completion Date
01-Mar-2006

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SLOVENSKI SIST EN 62310-1:2006

STANDARD
marec 2006
Sistemi s statičnim prenosom (STS) – 1. del: Splošne in varnostne zahteve
(IEC 62310-1:2005)
Static transfer systems (STS) - Part 1: General and safety requirements (IEC
62310-1:2005)
ICS 29.240.99 Referenčna številka
SIST EN 62310-1:2006(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

---------------------- Page: 1 ----------------------

EUROPEAN STANDARD EN 62310-1
NORME EUROPÉENNE
EUROPÄISCHE NORM April 2005

ICS 29.240.99


English version


Static transfer systems (STS)
Part 1: General and safety requirements
(IEC 62310-1:2005)


Systèmes de transfert statique (STS) Statische Transferschalter (STS)
Partie 1: Exigences générales et règles Teil 1: Allgemeine und
de sécurité Sicherheitsanforderungen
(CEI 62310-1:2005) (IEC 62310-1:2005)






This European Standard was approved by CENELEC on 2005-03-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels


© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 62310-1:2005 E

---------------------- Page: 2 ----------------------

EN 62310-1:2005 - 2 -
Foreword
The text of document 22H/66/FDIS, future edition 1 of IEC 62310-1, prepared by SC 22H,
Uninterruptible power systems (UPS), of IEC TC 22, Power electronic systems and equipment, was
submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 62310-1 on
2005-03-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2005-12-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-03-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 62310-1:2005 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60947-6-1 NOTE Harmonized as EN 60947-6-1:1991 (not modified).
IEC 61032 NOTE Harmonized as EN 61032:1998 (not modified).
IEC 61140 NOTE Harmonized as EN 61140:2002 (not modified).
IEC 62040 NOTE Harmonized in EN 62040 series (modified).
IEC 62040-1-1 NOTE Harmonized as EN 62040-1-1:2003 (not modified).
IEC 62040-1-2 NOTE Harmonized as EN 62040-1-2:2003 (not modified).
IEC 62040-3 NOTE Harmonized as EN 62040-3:2001 (modified).
__________

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- 3 - EN 62310-1:2005
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications
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.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 60060-1 1989 High-voltage test techniques HD 588.1 S1 1991
+ corr. March 1990 Part 1: General definitions and test
requirements

1) 2)
IEC 60073 - Basic and safety principles for man- EN 60073 2002
machine interface, marking and
identification - Coding principles for
indicators and actuators

1)
IEC/TR 60083 - Plugs and socket-outlets for domestic - -
and similar general use standardized in
member countries of IEC

1) 2)
IEC 60085 - Electrical insulation - Thermal EN 60085 2004
classification

1) 2)
IEC 60112 - Method for the determination of the EN 60112 2003
proof and the comparative tracking
indices of solid insulating materials

1)
IEC 60364-5-54 - Electrical installations of buildings - -
Part 5-54: Selection and erection of
electrical equipment - Earthing
arrangements, protective conductors
and protective bonding conductors

1)
IEC 60364-7-707 - Part 7: Requirements for special - -
installations or locations -- Section 707:
Earthing requirements for the
installations of data processing
equipment

database
IEC 60417 Graphical symbols for use on - -
equipment

IEC 60529 1989 Degrees of protection provided by EN 60529 1991
enclosures (IP Code) + corr. May 1993


1)
Undated reference.
2)
Valid edition at date of issue.

---------------------- Page: 4 ----------------------

EN 62310-1:2005 - 4 -
Publication Year Title EN/HD Year
IEC 60664-1 1992 Insulation coordination for equipment
+ A1 2000 within low-voltage systems
+ A2 2002 Part 1: Principles, requirements and EN 60664-1 2003
tests

IEC 60664-3 2003 Part 3: Use of coating, potting or EN 60664-3 2003
moulding for protection against pollution

IEC 60730-1 1999 Automatic electrical controls for EN 60730-1 2000
(mod) household and similar use A11 2002
Part 1: General requirements A12 2003
A1 (mod) 2003 A1 2004
A13 2004
A14 2005

1)
IEC/TR 60755 - General requirements for residual - -
current operated protective devices

IEC 60950-1 2001 Information technology equipment - EN 60950-1 2001
(mod) Safety
Part 1: General requirements

1) 2)
IEC 61008-1 - Residual current operated circuit- EN 61008-1 2004
(mod) breakers without integral overcurrent
protection for household and similar
uses (RCCB's)
Part 1: General rules

1) 2)
IEC 61009-1 - Residual current operated circuit- EN 61009-1 2004
(mod) breakers with integral overcurrent
protection for household and similar
uses (RCBO's)
Part 1: General rules

IEC 62103 2003 Electronic equipment for use in power - -
installations

3)
IEC 62310-2 - Static Transfer Systems (STS) - -
Part 2: Electromagnetic Compatibility
(EMC) requirements

ISO 3864-1 2002 Graphical symbols - Safety colours and - -
safety signs
Part 1: Design principles for safety
signs in workplaces and public areas

ISO 7000 2004 Graphical symbols for use on - -
equipment - Index and synopsis




3)
To be published.

---------------------- Page: 5 ----------------------

NORME CEI

INTERNATIONALE IEC



62310-1
INTERNATIONAL


Première édition
STANDARD

First edition

2005-03


Systèmes de transfert statique (STS) –
Partie 1:
Exigences générales et règles de sécurité

Static transfer systems (STS) –
Part 1:
General and safety requirements
 IEC 2005 Droits de reproduction réservés  Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
CODE PRIX
Commission Electrotechnique Internationale PRICE CODE XA
International Electrotechnical Commission
Международная Электротехническая Комиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue

---------------------- Page: 6 ----------------------

62310-1  IEC:2005 – 3 –
CONTENTS

FOREWORD.7

1 Scope .11
2 Normative references .13
3 Terms and definitions .15
3.1 General definitions .15
3.2 Specified values .25
3.3 Input values.31
4 Safety requirements .33
4.1 Marking and instructions .33
4.2 Fundamental design requirements .45
4.3 Physical requirements .99
4.4 Thermal requirements, fire protection and fire risks .105
5 Electrical requirements and simulated abnormal conditions .109
5.1 General .109
5.2 Electric strength .111
5.3 Abnormal operating and fault conditions.111

Annex A (normative) Method of calculating the cross-sectional area of protective
conductors with regard to thermal stresses due to currents of short duration (more
detailed information is to be found in IEC 60364-5-54).115
Annex B (normative) Minimum and maximum cross-sections of copper conductors
suitable for connection.117

Bibliography .119

Figure 1 – Test finger (see IEC 60529).47
Figure 2 – Test pin.49
Figure 3 – Test probe.49
Figure 4 – Determination of insulation within a circuit .69
Figure 5 – Determination of insulation between live parts and accessible – surfaces .71
Figure 6 – Determination of insulation a) between circuits and the environment, and b)
between circuits .73
Figure 7 – Determination of functional insulation .75
Figure 8 – Determination of basic insulation .77
Figure 9 – Determination of double or reinforced insulation.79

Table 1 – Distance through insulation of internal wiring .51
Table 2 – Cross-sectional area of protective conductors (PE, PEN).61
Table 3 – Definitions of pollution degrees .81
Table 4 – Clearances between primary circuits and their environment (impulse
withstand voltages according to overvoltage category III).85

---------------------- Page: 7 ----------------------

62310-1  IEC:2005 – 5 –
b)

Table 5 – Clearances between secondary circuits and their environment (impulse
withstand voltages according to overvoltage category II).87
Table 6 –Clearances within a circuit (impulse withstand voltage according to
overvoltage category I) .89
Table 7 – Minimum creepage distances.93
Table 8 – Limits for inherently limited power sources .95
Table 9 – Limits for power sources not inherently limited (overcurrent protective device
required) .97
Table 10 – Temperature rise limits: Part 1 .107
Table 11 – Temperature rise limits: Part 2 .109
Table A.1 – Values of k for insulated protective conductors not incorporated in cables,
or bare protective conductors in contact with cable covering .115
Table B.1 − Minimum and maximum cross-sections of copper conductors suitable for
connection.117

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62310-1  IEC:2005 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

STATIC TRANSFER SYSTEMS (STS) –

Part 1: General and safety requirements


FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62310-1 has been prepared by subcommittee 22H: Uninterruptible
Power Systems (UPS), of IEC technical committee 22: Power electronic systems and
equipment.
The text of this standard is based on the following documents:
FDIS Report on voting
22H/66/FDIS 22H/67/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
The French version of this standard has not been voted upon.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

---------------------- Page: 9 ----------------------

62310-1  IEC:2005 – 9 –
IEC 62310 consists of the following parts, under the general title Static transfer systems
(STS):
Part 1: General and safety requirements
1
Part 2: Electromagnetic Compatibility (EMC) requirements

2
Part 3: Method of specifying the performance and test requirements
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
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

___________
1
 To be published.
2
  Under consideration.

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62310-1  IEC:2005 – 11 –
STATIC TRANSFER SYSTEMS (STS) –

Part 1: General and safety requirements



1 Scope
IEC 62310 consists of three parts and applies to free standing a.c. static transfer systems
(STS) intended to ensure the continuity of power to load by automatically or manually
controlled transfer, with or without interruption, from two or several a.c. independent sources.
This part of IEC 62310 concerns general and safety requirements. See future IEC 62310-2 for
electromagnetic compatibility (EMC) and futureIEC 62310-3 for the method of specifying
performance and test requirements.
This part of IEC 62310 is intended to reduce the risk of fire, electric shock, or injury to
persons from installed equipment subject to installing, operating, and maintaining the
equipment in the manner prescribed by the manufacturer.
This part of IEC 62310 includes requirements for the switching elements, their control and
protective elements, where applicable. This part of IEC 62310 also includes information for
the overall integration of the STS and its accessories into the a.c. power distribution system.
Components or devices necessary for the operation/control/protection/isolation (e.g. circuit-
breakers, fuses, transformers, etc.) of a STS should comply with the requirements of the
relevant IEC standards and are not covered by this part of IEC 62310.
This standard applies to systems up to 1 000 V (a.c. value) which are intended to be used in
single phase or phase-phase or three phase applications.
This standard does not apply to:
− devices for d.c. source switching;
− static transfer system using only electromechanical switching devices intended to be used
in emergency power systems with interruption of the supply to the load during transfer.
This equipment is covered by IEC 60947-6-1;
− the automatic switching devices integrated into UPS covered by IEC 62040 series.
NOTE For STS intended to be used in vehicles, onboard ships or aircraft, in tropical countries, for emergency
power systems (such as those used for health care facilities, fire fighting, emergency rescue, etc.), or on elevations
greater than 1 000 m, different requirements may be necessary.

---------------------- Page: 11 ----------------------

62310-1  IEC:2005 – 13 –
2 Normative references
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.
IEC 60060-1:1989, High-voltage test techniques – Part 1: General definitions and test
requirements
IEC 60073, Basic and safety principles for man-machine interface, marking and identification
– Coding principles for indicators and actuators
IEC 60083, Plugs and socket-outlets for domestic and similar general use, standardised in
member countries of IEC
IEC 60085, Electrical insulation – Thermal classification
IEC 60112, Method for the determination of the proof and the comparative tracking indices of
solid insulating materials
IEC 60364-5-54, Electrical installations of buildings – Part 5-54: Selection and erection of
electrical equipment – Earthing arrangements, protective conductors and protective bonding
conductors
IEC 60364-7-707, Electrical installations of building – Part 7: Requirements for special
installations or locations – Section 707: Earthing requirements for the installation of data
processing equipment
3
IEC 60417-DB:2002 , Graphical symbols for use on equipment
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60664-1:1992, Insulation co-ordination for equipment within low-voltage systems – Part 1:
4
Principles, requirements and tests
Amendment 1 (2000)
Amendment 2 (2002)
IEC 60664-3:2003, Insulation coordination for equipment within low-voltage systems – Part 3:
Use of coating, potting or moulding for protection against pollution
IEC 60730-1:1999, Automatic electrical controls for household and similar use – Part 1:
5
General requirements
Amendment 1 (2003)
IEC 60755, General requirements for residual current operated protective devices

___________
3
“DB” refers to the IEC on-line database.
4
 A consolidated edition 1.2 exists including IEC 60664-1:1992 and its Amendments 1 (2000) and 2 (2002).
5
 A consolidated edition 3.1 exists including IEC 60730-1:1999 and its Amendment 1 (2003).

---------------------- Page: 12 ----------------------

62310-1  IEC:2005 – 15 –
IEC 60950-1:2001, Information technology equipment – Safety – Part 1: General requirements
IEC 61008-1, Residual current operated circuit-breakers without integral overcurrent
protection for household and similar uses (RCCBs) – Part 1: General rules
IEC 61009-1, Residual current operated circuit-breakers without integral overcurrent
protection for household and similar uses (RCBOs) – Part 1: General rules
IEC 62103:2003, Electronic equipment for use in power installations
IEC 62310-2, ___ Static transfer systems (STS) – Part 2: Electromagnetic Compatibility
6
(EMC) requirements
ISO 3864-1:2002, Graphical symbols – Safety colours and safety signs – Part 1: Design
principles for safety signs in workplaces and public areas
ISO 7000:2004, Graphical symbols for use on equipment – Index and synopsis
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 General definitions
3.1.1
transfer switch
switching equipment consisting of one or more switches used to transfer power from one
source to another
3.1.2
static transfer system
STS
system that transfers a load, by static means, between a preferred source and an alternate
source
NOTE 1 The transfer may be automatic and/or manual.
NOTE 2 The transfer may be with or without interruption.
3.1.3
electronic (power) switch
operative unit for electronic power switching comprising at least one controllable valve device
[IEV 551-13-01]
3.1.4
line commutated electronic switch
electronic switch where the commutating voltage is supplied by the line
___________
6
To be published.

---------------------- Page: 13 ----------------------

62310-1  IEC:2005 – 17 –
3.1.5
maintenance by-pass
power path designed to allow isolation of an appropriate section or sections of a STS for
safety during maintenance and/or to maintain continuity of load power
3.1.6
redundant system
addition of functional units or groups of functional units in a system to enhance the continuity
of power to the load
3.1.7
STS input power
power supplied to STS and bypass, if any, which can be either the preferred source or the
alternate source
3.1.8
alternate source
source used as alternate power supply of the load when the preferred source fails or is out of
tolerance or is switched off for maintenance
3.1.9
preferred source
source used as normal power supply to the load, usually set by the operator
3.1.10
linear load
load where the current drawn from the supply is defined by the relationship:
I = U/Z
where
I is the load current;
U is the supply voltage;
Z is the constant load impedance.
3.1.11
non linear load
load where the parameter Z (load impedance) is no longer a constant but is a variable
dependent on other parameters, such as voltage or time
3.1.12
power failure
any variation in power source deemed to cause unacceptable performance of the load
equipment
3.1.13
normal mode of STS operation
when the load is supplied by the preferred source or the alternate source via the electronic
(power) switches
3.1.14
by-pass mode
when the load is supplied via the maintenance by-pass isolation switch

---------------------- Page: 14 ----------------------

62310-1  IEC:2005 – 19 –
3.1.15
manual control
control of an operation by human intervention
[IEV 441-16-04]
3.1.16
manual transfer
transfer operation initiated by human intervention
3.1.17
automatic control
control of an operation without human intervention, in response to the occurrence of
predetermined conditions
[IEV 441-16-05]
3.1.18
automatic transfer
transfer initiated without human intervention, in response to the occurrence of predetermined
conditions
3.1.19
STS synchronous transfer
transfer of load power between two sources which are synchronised within specified limits of
frequency, voltage phase and magnitude
3.1.20
STS asynchronous transfer
transfer of load power between two sources which are not synchronised within specified limits
3.1.21
operator access area
area to which, under normal operating conditions, one of the following applies:
– access can be gained without the use of a tool, or
– the means of access is deliberately provided to the operator, or
– the OPERATOR is instructed to enter regardless of whether or not a tool is needed to gain
access
NOTE The terms "access" and "accessible", unless qualified, relate to operator access area as defined above.
3.1.22
service access area
area, other than an operator access area, where it is necessary for service personnel to have
access even with the equipment switched on
3.1.23
restricted access location
location for equipment where both of the following paragraphs apply:
– access can only be gained by service personnel or by users who have been instructed
about the reasons for the restrictions applied to the location and about any precautions
that shall be taken; and

---------------------- Page: 15 ----------------------

62310-1  IEC:2005 – 21 –
– access is through the use of a tool or lock and key, or other means of security, and is
controlled by the authority responsible for the location
NOTE The requirements for equipment intended for installation in restricted access locations are the same as for
operator access areas, except as given in 1.7.17, 2.1.3 and 4.5.1 of IEC 60950-1.
3.1.24
STS primary circuit
internal circuit which is directly connected to the external supply source which supplies the
electric power to the load, including the primary windings of transformers, motors, other
loading devices and the means of connection to the supply source
3.1.25
STS secondary circuit
circuit which has no direct connection to STS primary circuit
3.1.26
decisive voltage
voltage, taking into account non-sinusoidal waveforms (see 5.2.13 of IEC 621
...

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