EN 62310-3:2008

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Statische Transfersysteme - Teil 3: Verfahren für die Festlegung des Betriebsverhaltens und Prüfanforderungen (IEC 62310-3:2008)Systèmes de transfert statique (STS) - Partie 3: Méthode de spécification des performances et exigences d'essai (CEI 62310-3:2008)Static transfer systems (STS) - Part 3: Method for specifying performance and test requirements (IEC 62310-3:2008)29.240.30Krmilna oprema za elektroenergetske sistemeControl equipment for electric power systems29.200QDSDMDQMHRectifiers. Convertors. Stabilized power supplyICS:Ta slovenski standard je istoveten z:EN 62310-3:2008SIST EN 62310-3:2008en,fr01-november-2008SIST EN 62310-3:2008SLOVENSKI
STANDARD
EUROPEAN STANDARD EN 62310-3 NORME EUROPÉENNE
EUROPÄISCHE NORM September 2008
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
© 2008 CENELEC -
All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62310-3:2008 E
ICS 29.200; 29.240.30
English version
Static transfer systems (STS) -
Part 3: Method for specifying performance and test requirements (IEC 62310-3:2008)
Systèmes de transfert statique (STS) -
Partie 3: Méthode de spécification des performances et exigences d'essai (CEI 62310-3:2008)
Statische Transfersysteme -
Teil 3: Verfahren für die Festlegung des Betriebsverhaltens und Prüfanforderungen(IEC 62310-3:2008)
This European Standard was approved by CENELEC on 2008-07-01. 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, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom.
Foreword The text of document 22H/105/FDIS, future edition 1 of IEC 62310-3, 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 62310-3 on 2008-07-01. 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)
2009-04-01 – latest date by which the national standards conflicting
with the EN have to be withdrawn
(dow)
2011-07-01 Annex ZA has been added by CENELEC. __________ Endorsement notice The text of the International Standard IEC 62310-3:2008 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 60664-3 NOTE
Harmonized as HD 625.3 S1:1997 (not modified). HD 625.3 S1 is superseded by EN 60664-3:2003 which is based on IEC 60664-3:2003. IEC 60947-1 NOTE
Harmonized as EN 60947-1:2007 (not modified). IEC 60990 NOTE
IEC 60990:1990 is superseded by IEC 60990:1999, which is harmonized as EN 60990:1999 (not modified). IEC 61140 NOTE
Harmonized as EN 61140:2002 (not modified). IEC 61400-1 NOTE
Harmonized as EN 61400-1:2005 (not modified). IEC 62040-2 NOTE
Harmonized as EN 62040-2:2006 (not 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). __________ SIST EN 62310-3:2008

- 3 - EN 62310-3:2008 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
When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies.
Publication Year Title EN/HD Year
IEC 60068 Series Environmental testing EN 60068 Series
IEC 60146-1-1 -1) Semiconductor convertors - General requirements and line commutated convertorsPart 1-1: Specification of basic requirements EN 60146-1-1 19932)
IEC 60439-1 -1) Low-voltage switchgear and controlgear assemblies -
Part 1: Type-tested and partially type-tested assemblies EN 60439-1 19992)
IEC 60529 -1) Degrees of protection provided by enclosures (IP Code) EN 60529 + corr. May
19912) 1993
IEC 60947-6-1 -1) Low-voltage switchgear and controlgear -
Part 6-1: Multiple function equipment - Transfer switching equipment EN 60947-6-1 20052)
IEC 60950-1 (mod) -1) Information technology equipment - Safety - Part 1: General requirements EN 60950-1 20062)
IEC 61000-2-2 -1) Electromagnetic compatibility (EMC) -
Part 2-2: Environment - Compatibility levels for low-frequency conducted disturbances and signalling in public low-voltage power supply systems EN 61000-2-2 20022)
IEC 62040-3 (mod) -1) Uninterruptible power systems (UPS) -
Part 3: Method of specifying the performance and test requirements EN 62040-3 20012)
IEC 62310-1 -1) Static transfer systems (STS) -
Part 1: General and safety requirements EN 62310-1 20052)
IEC 62310-2 (mod) -1) Static transfer systems (STS) -
Part 2: Electromagnetic compatibility (EMC) requirements EN 62310-2 20072)
ISO 7779 -1) Acoustics - Measurement of airborne noise emitted by information technology and telecommunications equipment EN ISO 7779 20012)
1) Undated reference. 2) Valid edition at date of issue. SIST EN 62310-3:2008

IEC 62310-3Edition 1.0 2008-06INTERNATIONAL STANDARD NORME INTERNATIONALEStatic transfer systems (STS) –
Part 3: Method for specifying performance and test requirements
Systèmes de transfert statique (STS) –
Partie 3: Méthode de spécification des performances et exigences d’essai
INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE XAICS 29.200; 29.240.30 PRICE CODECODE PRIXISBN 2-8318-9812-9
– 2 – 62310-3 © IEC:2008 CONTENTS FOREWORD.4 1 Scope.6 2 Normative references.6 3 Terms and definitions.7 3.1 General definitions.7 3.2 Specified values.10 3.3 Input values.11 3.4 Output values.11 4 Performance requirements.12 4.1 Declared electrical characteristics.12 4.1.1 Performance classification.12 4.1.2 Main electrical characteristics.13 4.2 Normal service conditions.14 4.3 Transfer characteristics.14 4.3.1 Load voltage.14 4.3.2 Cross-current.15 4.4 Neutral management.15 4.4.1 Common neutral.15 4.4.2 Separately derived neutrals.15 4.4.3 Neutral current.15 4.4.4 Protective earth current.15 4.5 Performance requirements to be identified by the purchaser.16 5 STS tests.16 5.1 General.16 5.1.1 Type tests.16 5.1.2 Routine tests.16 5.1.3 Site tests.16 5.1.4 Testing schedule.16 5.2 Electrical tests.18 5.2.1 Insulation and dielectric.18 5.2.2 Light load and functional test.18 5.2.3 No load.19 5.2.4 Rated load.19 5.2.5 Transfer.19 5.2.6 Source tolerance.21 5.2.7 Overload and fault current.21 5.2.8 Operating losses.23 5.2.9 Backfeed.24 5.2.10 Abnormal operating conditions.25 5.3 Transportation and environment.26 5.3.1 General.26 5.3.2 Impact and shock.26 5.3.3 Free fall.26 5.3.4 Storage.27 5.3.5 Temperature and humidity.28 5.3.6 Acoustic noise.28 SIST EN 62310-3:2008

62310-3 © IEC:2008 – 3 – Annex A (normative)
Reference load.29 Annex B (normative)
STS voltage sensing tolerance.33 Annex C (informative)
Neutral management in static transfer systems.35 Annex D (normative)
Neutral switching in static transfer systems – Additional requirements.37 Annex E (informative)
Purchaser specification guidelines.39 Annex F (informative)
Output short circuit test procedure.43 Annex G (normative)
Backfeed protection test.47 Annex H (normative)
Minimum and maximum cross-sections of copper
conductors suitable for connection.48 Bibliography.49
Figure 1 – Complying load current flow - Common grounding of a.c. input sources - common STS neutral.15 Figure 2 – Objectionable load current flow - Independent grounding of a.c. input sources - common STS neutral.16 Figure 3 – STS cross current test.20 Figure 4 – Typical circuit for measuring conduction losses.24 Figure B.1 – Source tolerance classification 1.33 Figure B.2 – Source tolerance classification 2.34 Figure B.3 – Source tolerance classification 3.34 Figure B.4 – Source tolerance classification 4.34 Figure C.1 – Continuous STS neutral with common grounding of a.c. input sources (complying load current flow).35 Figure C.2 – Continuous STS neutral with independent grounding of a.c. input
sources + isolation transformer (complying load current flow).36 Figure C.3 – Switched STS with independent grounding of a.c. input sources
(complying steady state load current flow).36 Figure D.1 – Load voltage variation upon neutral switch failure.37 Figure D.2 – Overlapping switched STS neutral.38 Figure F.1 – Test circuit for STS output withstand current.45
Table 1 – Transfer interruption classification “T”.13 Table 2 – Tests for STS performance characteristics.17 Table 3 – Short time withstand current.22 Table 4 – Free fall testing.27 Table E.1 – STS technical data sheet.41 Table F.1 – Values of power-factors and time-constants corresponding to test currents and ratio n between peak and r.m.s. values of current.44 Table H.1 – Minimum and maximum cross-sections of copper conductors suitable
for connection (extract from IEC 60439-1).48
– 4 – 62310-3 © IEC:2008 INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________
STATIC TRANSFER SYSTEMS (STS) –
Part 3: Method for specifying performance and test 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 62310-3 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/105/FDIS 22H/107/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. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. A list of all parts of the IEC 62310 series, under the general title: Static transfer systems (STS), can be found on the IEC website. SIST EN 62310-3:2008

62310-3 © IEC:2008 – 5 – 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. SIST EN 62310-3:2008

– 6 – 62310-3 © IEC:2008 STATIC TRANSFER SYSTEMS (STS) –
Part 3: Method for specifying performance and test requirements
1 Scope The IEC 62310 series of three standards applies to stand-alone operating
a.c. static transfer systems (STS) intended to ensure the continuity of load supply through controlled transfer, with or without interruption of power, from two or
more independent a.c. sources. This series of standards includes information for the overall integration of the STS and its accessories into the a.c. power network and includes requirements for the switching elements, their control and protective elements, where applicable.
Part 1 of the series concerns general and safety requirements. Part 2 of the series concerns electromagnetic compatibility (EMC) requirements. This Part 3 of the series concerns methods for specifying performance and test requirements including applicable safety tests referenced in standard IEC 62310-1 for general and safety requirements.
This standard applies for single-phase, phase-phase and three-phase static transfers in a. c. systems up to 1 000 V. It takes precedence over all aspects of generic performance standards, and no additional performance testing is necessary.
The requirements have been selected so as to be consistent with compatibility levels for low-frequency conducted disturbances and signalling in public low-voltage power supply systems (see IEC 61000-2-2) as well as to ensure an adequate level of performance when the STS is applied in diverse critical load situations. The requirements take into account the differing test conditions necessary to encompass the range of physical sizes and power ratings of STS. This standard applies to STS as a stand-alone product, whether presented as a unit or an assembly of units. This standard does not apply to: – devices for d.c. source switching; – single source systems; – transfer systems using only electromechanical switching devices with interruption of the supply to the load during transfer and intended to be used in emergency power systems or covered by IEC 60947-6-1; – automatic switching devices integrated into UPS covered by the IEC 62040 series of UPS product standards. NOTE Additional or different requirements may apply to STS intended for use on board of vehicles including ships and aircrafts, in emergency power systems subject to a particular regulation e.g. health care facilities, fire fighting or emergency rescue, in tropical countries or where elevations are greater than 1 000 m. 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 60068 (all parts), Environmental testing SIST EN 62310-3:2008

62310-3 © IEC:2008 – 7 – IEC 60146-1-1, Semiconductor convertors – General requirements and line commutated convertors – Part 1-1: Specifications of basic requirements
IEC 60439-1, Low-voltage switchgear and controlgear assemblies – Part 1: Type-tested and partially type-tested assemblies
IEC 60529, Degrees of protection provided by enclosures (IP Code) IEC 60947-6-1, Low-voltage switchgear and controlgear – Part 6-1: Multiple function equipment – Transfer switching equipment IEC 60950-1, Information technology equipment – Safety – Part 1: General requirements IEC 61000-2-2, Electromagnetic compatibility (EMC) – Part 2-2: Environment –
Compatibility levels for low-frequency conducted disturbances and signalling in public low-voltage power supply systems IEC 62040-3, Uninterruptible power systems (UPS) – Part 3: Method of specifying the performance and test requirements IEC 62310-1, Static Transfer Systems (STS) – Part 1: General and safety requirements IEC 62310-2, Static Transfer Systems (STS) – Part 2: Electromagnetic Compatibility (EMC) requirements ISO 7779, Measurement of airbone noise emitted by information technology and telecommunications equipment 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 General definitions 3.1.1
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. 3.1.2
power pole or electronic power switch in the context of this standard, an operative unit for electronic power switching comprising at least one controlled electronic valve device [IEV 551-13-01, modified] 3.1.3
primary circuit internal circuit which is directly connected to the external supply source which supplies the electric power to the load. It includes the primary windings of transformers, motors, other loading devices and the means of connection to the supply source. SIST EN 62310-3:2008

– 8 – 62310-3 © IEC:2008 3.1.4
input power power derived either from the preferred or from the alternate source or from both and supplied to the STS (and maintenance bypass if any) 3.1.5
SELV circuit secondary circuit which is so designed and protected that under normal operating conditions and single fault conditions, its voltages do not exceed a safe value NOTE 1 The limit values of voltages under normal operating conditions and single fault conditions are specified in 2.2 of IEC 60950-1, see also Table 1A of IEC 60950-1. NOTE 2 This definition of an SELV CIRCUIT differs from the term “SELV system” as used in IEC 61140. 3.1.6
preferred source source used as normal power supply to the load, usually set by the operator 3.1.7
alternate source source used as alternate power supply to the load when the preferred source fails or is out of tolerance or is switched off for maintenance 3.1.8
normal mode of STS operation condition where the load is supplied via the electronic (power) switches by either the preferred source or by the alternate source
3.1.9
maintenance bypass
power path designed to allow isolation of an appropriate section or sections of an STS for safety during maintenance and/or to maintain continuity of load power 3.1.10
transfer act of altering the supply path to the load from one source to another
3.1.11
automatic transfer transfer without human intervention as a result of the supplying source being outside specified conditions
3.1.12
automatic retransfer transfer without human intervention from an alternate to the preferred source once the preferred source has returned to specified conditions
3.1.13
manual transfer transfer that occurs as a result of local or remote operator intervention 3.1.14
normal transfer transfer of load power between two sources while
their voltage phase angle difference is within a tolerance band as declared by the manufacturer
3.1.15
synchronous (or synchronised) transfer transfer within a limited voltage phase angle difference specified by the user SIST EN 62310-3:2008

62310-3 © IEC:2008 – 9 – 3.1.16
asynchronous (or non-synchronised) transfer transfer of load power between two sources while their voltage phase angle difference, when transfer occurs, is out of a tolerance band as declared by the manufacturer 3.1.17
transfer time time interval between initiation of transfer and the instant when the output quantities have been transferred 3.1.18
cross-current
current due to conduction from a phase of one source through electronic power switches to the corresponding phase of another source
3.1.19
objectionable current load current that, during normal operation and/or transfers, flows in paths other than those intended and that contributes to any of the following: – interference with the proper sensing and operation of ground-fault residual current devices (RCDs) – arcing of sufficient energy to ignite flammable materials – electromagnetic emission in excess of levels prescribed in IEC 62310-2 for STSs 3.1.20
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 a constant impedance
3.1.21
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
3.1.22
active power
under periodic conditions, mean value, taken over one period T, of the instantaneous power p: ∫⋅⋅=TdtpTP01 [IEV 131-11-42] NOTE 1 Under sinusoidal conditions, the active power is the real part of the complex power.
NOTE 2 The SI unit for active power is the watt. NOTE 3 DC, fundamental and harmonic voltages contribute directly to the magnitude of the active power. Where applicable, instruments used to measure active power should therefore present sufficient bandwidth and be capable of measuring any significant non-symmetrical and harmonic power components. SIST EN 62310-3:2008

– 10 – 62310-3 © IEC:2008 3.1.23
power factor, (λ) ratio of the active power to the apparent power
SP=λ [IEV 131-11-46, modified]
NOTE For the purpose of this standard, the load power factor is determined assuming an ideal sinusoidal supply voltage, where the load is non-linear; the load power factor includes harmonic power components.
3.1.24
apparent power, (S) product of the r.m.s. values of voltage and current at a port
[IEV 133-11-41, modified] UxIS= 3.1.25
ambient temperature temperature of the air or other medium where the equipment is to be used
[IEV 826-01-04] 3.2 Specified values 3.2.1
rated value quantity value assigned, generally by a manufacturer, for a specified operating condition of a component, device or equipment
[IEV 151-16-08, modified]
3.2.2
rating
set of rated values and operating conditions of a machine or a device or equipment
[IEV 151-16-11] 3.2.3
tolerance (band) range of values of a quantity within specified limits 3.2.4
deviation difference between the desired value and the actual value of a variable at a given instant
[IEV 351-12-15, modified] 3.2.5
transient behaviour of a variable during transition between two steady states
[IEV 351-14-04] 3.2.6
rated voltage input or output voltage (for three-phase supply, the phase-to-phase and phase-to-neutral voltage when the
STS supports neutral connection) as declared by the manufacturer SIST EN 62310-3:2008

62310-3 © IEC:2008 – 11 – 3.2.7
voltage variation difference between the r.m.s. voltage and the corresponding previously undisturbed r.m.s. voltage NOTE For the purposes of this standard, the term "variation" has the following meaning: the difference of the value of a quantity before and after a change of an influence quantity. 3.2.8
rated current r.m.s. input or output phase current of the equipment as declared by the manufacturer 3.2.9
rated frequency operating frequency as declared by the manufacturer 3.2.10
total harmonic distortion (THD)
ratio in percent of the r.m.s. value of the harmonic content to the r.m.s. value of the fundamental component of the alternating quantity 3.2.11
harmonic components components of the harmonic content as expressed in terms of the order and r.m.s. values of the Fourier series terms describing the periodic function
3.2.12
harmonic content
quantity obtained by subtracting from an alternating quantity its fundamental component NOTE The harmonic content may be given as a time-function or as an r.m.s. value. 3.2.13
crest or peak factor ratio of
peak value to the r.m.s. value of a periodic quantity NOTE The terms «crest factor» and «peak factor» have the same meaning. 3.3 Input values 3.3.1
input voltage tolerance maximum variation of steady-state input voltage acceptable by the STS to function 3.3.2
input frequency tolerance maximum variation of steady-state input frequency acceptable by the STS to function 3.4 Output values 3.4.1
critical load voltage protection limits maximum variation of steady-state and of transient output voltage of the STS
3.4.2
conditional short-circuit current
prospective current that a STS can withstand
when protected by a specified protective device SIST EN 62310-3:2008

– 12 – 62310-3 © IEC:2008 3.4.3
output voltage tolerance maximum variation of steady-state output voltage of
the STS, generally adjusted to ensure compliance with the critical load protection limits
3.4.4
overload capability output current capability of the STS in excess of its stated continuous current over a given time, with the output voltage remaining within its rated range 3.4.5
short time withstand current
current that a circuit or a switching device in a closed position can carry during a specified short time and under prescribed conditions of use and behaviour 3.4.6
step load instantaneous addition or removal of electrical loads to a power source 4 Performance requirements 4.1 Declared electrical characteristics 4.1.1 Performance classification The manufacturer shall classify STSs complying with this standard in accordance with the following coding.
XX YY B ST where
XX characterises the management of fault current: CB: STS capable of making and of breaking specified short-circuit currents and containing integral overcurrent protection. PC: STS capable of making and of withstanding specified short-circuit currents but not intended for breaking short-circuit currents. YY characterises the management of input neutrals: 00 – Neutral not supported NC – Neutral common NS – Neutral separation by switching NI – Neutral separation by galvanic isolation NOTE Galvanic neutral isolation can be achieved through the use of an isolation transformer. B characterises the nature of the transfer: B -
Break before make (open transition) – no transient cross-conduction during transfer M - Make before break (closed transition) – possible transient cross-conduction during transfer ST characterises the sensing and transfer features:
”S” - sensing tolerance prior to automatic transfer being initiated
Voltage in the conducting source, when beyond the specified sensing tolerance, shall cause the STS to initiate an automatic transfer. Figures B.1, B.2, B.3 and B.4 of Annex B define the over and undervoltage limits corresponding to sensing tolerances 1, 2, 3 and 4 respectively. The sensing tolerance (S) shall be agreed on between the manufacturer and the purchaser in accordance with voltage limits deemed acceptable for the critical load - see Annex E – Purchaser specification guidelines SIST EN 62310-3:2008

62310-3 © IEC:2008 – 13 –
“T” - duration of any power interruption to the load once an automatic transfer is initiated (see Table 1) Table 1 – Transfer interruption classification “T” T Interruption
ms 1 ≤ 0,1 2 ≤ 1 3 ≤ 10 4 ≤ 20 5 (reserved)
NOTE Transfer classification
T = 5 is reserved for particular transfer characteristics if required and agreed upon between the manufacturer/supplier and the purchaser. Compliance with the STS sensing and transfer features is required when at least one input source is within tolerance under conditions agreed between the purchaser and the manufacturer. For guidance, refer to “Maximum voltage phase difference between sources to enable synchronous transfer” in Table E.1. In the event of all preferred and alternate source(s) being out of tolerance, the manufacturer shall specify the performance. NOTE Phase to neutral voltage sensing is required in STS where a neutral connection is available to the load. Example of STS performance classification: “PC NC B 23” characterises a STS that – can make and withstand specified short-circuit currents but that is not intended for breaking of short-circuit currents,
– presents a common input neutral terminal for all sources – is break before make (open transition), causing no transient cross-conduction during a transfer – initiates a transfer automatically when the voltage of the conducting source is beyond the limits for source tolerance classification 2 (see Annex B)
– may interrupt supply to the load for up to 10 ms during the transfer 4.1.2 Main electrical characteristics The STS manufacturer shall specify the following characteristics in the application documentation pertaining to a STS that complies with this standard. 4.1.2.1 Current – Rated (phase r.m.s. value) 4.1.2.2 Voltage – rated (phase-phase / phase–neutral as applicable, r.m.s. value) – input tolerance (refer to 4.2a) – input unbalance tolerance (for 3-phase STS, refer to 4.2.c)
4.1.2.3 Frequency – rated – tolerance (refer to 4.2.b) 4.1.2.4 Input / output wiring – number of phases (1, 2 or 3) + N (if applicable) SIST EN 62310-3:2008

– 14 – 62310-3 © IEC:2008 – pluggable or fixed wiring 4.1.2.5 Input sources – number of input sources (2 or more)
– reference compatibility (common or separately derived, common or separately grounded) – distribution compatibility (TNC, TNS, TT or IT, refer to annex V IEC 60950-1) 4.1.2.6 Power poles – number of poles switched (1, 2, 3 or 4) – switching sequence (open or closed transition – refer to 4.1.1)
– rated neutral current (percentage of rated phase current) – state if the neutral is switched (refer to 4.1.1) 4.1.2.7 Overload – declared (% of rated current and duration) – load fault clearing capability (% of rated phase current and duration, refer to 5.2.7.2) 4.1.2.8 Fault (short-circuit) current – management (PC or CB – refer 4.1.1) – withstand capability, rated (kA and duration – refer to 5.2.7.3 ) – breaking capability, rated - CB management only (kA – refer to 5.2.7.3) 4.1.2.9 Operating losses at rated load (refer to 5.2.8) 4.2 Normal service conditions Except where otherwise specified in this paragraph , the STS shall be compatible with
– levels for low-frequency conducted disturbances and signalling in public low-voltage power supply systems as described in IEC 61000-2-2; – linear loads; – non-linear loads as specified in Clause
A.5. The STS shall be capable of operation when at least one source meets the following limits:
a) voltage variation ±10 % of nominal rated voltage, minimum; b) frequency variation ±5 % of nominal rated frequency; c) voltage unbalance of 5% for three-phase systems (see 2.5 of IEC 60146-1-1). NOTE The conditions above represent compatibility requirements for proper operation of the STS and its control circuits (as opposed to representing the actual operating limits required by the load − see Annex B). 4.3 Transfer characteristics 4.3.1 Load voltage Transfers and retransfers in STS conforming to this standard, whether manual or automatic, shall not contribute to an output voltage deviation in excess of the critical load voltage protection limits as declared by the manufacturer in 4.1.1. Refer to 5.2.5.1 and 5.2.1.2 for test guidance. The manufacturer shall declare the maximum voltage phase difference permitted between sources to comply with the STS transfer classification declared (see 4.1.1). SIST EN 62310-3:2008

62310-3 © IEC:2008 – 15 – 4.3.2 Cross-current Static transfer equipment shall not permit cross-current flow between input sources under any normal operating condition except for inherent transient currents that may arise during synchronised transfers through STS declared “closed transfer” or “make before break”. Design of STS shall guard against current flow between sources arising as a result of a single fault condition. Static transfer equipment declared by the manufacturer to be “closed transfer” or “make before break” shall tolerate any inherent transient currents that may arise during synchronised transfers without malfunctioning.
Refer to 5.2.5.3 for test guidance. 4.4 Neutral management 4.4.1 Common neutral No neutral switching or particular management of the neutral reference is required where a.c. input sources share a common neutral grounding point. Refer to Annex C for guidance. 4.4.2 Separately derived neutrals A neutral management technique is required when separately derived a.c. input sources are independently grounded and connected to a STS. Refer to Annex C for guidance.
4.4.3 Neutral current The current carrying capacity of STS shall support the neutral current arising from any rated combination of balanced and unbalanced linear load and of non-linear load as described in Clause A.5. 4.4.4 Protective earth current The STS shall not contribute to objectionable load current flow in the protective earth conductor.
NOTE
Current may flow in the protective earth conductor during transfers. This is permissible as long as the current does not become objectionable (objectionable current is defined in 3.1). Figure 1 is an example of a complying STS application wherein objectionable load current cannot flow in the protective earth conductor because one a.c. source is referred to the grounding potential of the other. The installer should verify the continuous effectiveness of the neutral grounding path as applicable. In TN systems, this may impose additional conditions on the upstream use of manual or automatic circuit-breakers that open the neutral.
AC sourcesSTSLoad IEC
788/08 Figure 1 – Complying load current flow – Common grounding of a.c. input sources – Common STS neutral SIST EN 62310-3:2008

– 16 – 62310-3 © IEC:2008 Figure 2 is an example of a non-complying STS application wherein objectionable load current can flow in the protective earth because both a.c. sources are independently grounded.
AC sourcesSTSLoadObjectionable current flow IEC
789/08 Figure 2 – Objectionable load current flow – Independent grounding of a.c. input sources – Common STS neutral Compliance is checked by circuit analysis of the STS in the context of a.c. input power distribution system classification (TN, TT, IT), the number of phases and of wires as presented in Annex V of 60950-1. 4.5 Performance requirements to be identified by the purchaser When applicable, and subject to an agreement between the manufacturer and the purchaser, the purchaser shall identify alternative application related performance requirements and deviation limits not specified in this Clause. Refer to Annex E for guidance. 5 STS tests
5.1 General 5.1.1 Type tests Type tests are performed on a STS that represents a series of substantially identical products. Type tests are intended to ensure that such identical products become compliant with their full specification when produced under relevant quality standards and after having passed the routine tests detailed in this Clause. 5.1.2 Routine tests Routine and any optional tests are generally performed in the factory.
5.1.3 Site tests Site tests are subject to an agreement between the purchaser and the manufacturer. If routine tests are conducted on site, such tests shall use the available site load that shall not exceed the rated continuous load of the complete STS site configuration. 5.1.4 Testing schedule Tests shall be performed in accordance with Table 2. SIST EN 62310-3:2008

62310-3 © IEC:2008 – 17 – Table 2 – Tests for STS performance characteristics Test
description Routine test Type test Subclause Insulation (to ground) x x 5.2.1a Insulation (input to input and input to output) a)
x 5.2.1.b, c
Light load
x x 5.2.2 Functional and Interconnection cable check x x 5.2.2 Control device(s)
x x 5.2.2.a Protective device(s) x x 5.2.2.b Auxiliary device(s) x x 5.2.2.c Supervisory, measuring, signalling device(s) x x 5.2.2.d Automatic transfer x x 5.2.2e Manual transfer x x 5.2.2.f No load x x 5.2.3 Rated load x x 5.2.4 Automatic transfer
x 5.2.5.1 Manual transfer
x 5.2.5.2 Cross-current
x 5.2.5.3 Source tolerance (voltage and frequency)
x 5.2.6 Overload
x 5.2.7.1 Overcurrent clearing capability
x 5.2.7.2 Short-circuit withstand current
x 5.2.7.3 Operating losses
x 5.2.8 Backfeed
x 5.2.9 Abnormal operating conditions
x 5.2.10 Transportation and environment
x 5.3.1 Impact and shock
x 5.3.2 Free fall
x 5.3.3 Storage
x 5.3.4 Temperature and humidity
x 5.3.5 Acoustic noise
x 5.3.6 Safety
x See IEC 62310-1 Electromagnetic compatibility
x See IEC 62310-2
a) The routine test exemption for input to input and input to output insulation applies only when: – manufacturing is subjected to a quality control
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