SIST EN IEC 61869-13:2021

SLOVENSKI STANDARD
01-september-2021
Instrumentni transformatorji - 13. del: Samostojni koncentrator (SAMU) (IEC 61869
-13:2021)
Instrument transformers - Part 13: Stand-alone merging unit (SAMU) (IEC 61869-
13:2021)
Messwandler - Teil 13: Unabhängige Merging Unit (IEC 61869-13:2021)
Transformateurs de mesure - Partie 13: Concentrateur autonome (SAMU) (IEC 61869-
13:2021)
Ta slovenski standard je istoveten z: EN IEC 61869-13:2021
ICS:
17.220.20 Merjenje električnih in Measurement of electrical
magnetnih veličin and magnetic quantities
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61869-13

NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2021
ICS 17.220.20
English Version
Instrument transformers - Part 13: Stand-alone merging unit
(SAMU)
(IEC 61869-13:2021)
Transformateurs de mesure - Partie 13: Concentrateur Messwandler - Teil 13: Unabhängige Merging Unit
autonome (SAMU) (IEC 61869-13:2021)
(IEC 61869-13:2021)
This European Standard was approved by CENELEC on 2021-03-10. 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61869-13:2021 E

European foreword
The text of document 38/634/FDIS, future edition 1 of IEC 61869-13, prepared by IEC/TC 38
“Instrument transformers” was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN IEC 61869-13:2021.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2022-01-16
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2024-07-16
document have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a mandate given to CENELEC by the European Commission
and the European Free Trade Association.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 61869-13:2021 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 60255 series NOTE Harmonized as EN 60255 series
IEC 60255-1 NOTE Harmonized as EN 60255-1
IEC 60255-21-1 NOTE Harmonized as EN 60255-21-1
IEC 60255-21-2 NOTE Harmonized as EN 60255-21-2
IEC 60255-21-3 NOTE Harmonized as EN 60255-21-3
IEC 60255-26:2013 NOTE Harmonized as EN 60255-26:2013 (not modified)
IEC 61000-6-5 NOTE Harmonized as EN 61000-6-5
IEC 61850-9-2 NOTE Harmonized as EN 61850-9-2
IEC 61869-3 NOTE Harmonized as EN 61869-3
IEC 61869-4 NOTE Harmonized as EN 61869-4
IEC 61869-5 NOTE Harmonized as EN 61869-5
IEC 62052 series NOTE Harmonized as EN 62052 series
IEC 62053 series NOTE Harmonized as EN 62053 series
IEC 62053-22 NOTE Harmonized as EN IEC 62053-22
IEC 62271 series NOTE Harmonized as EN 62271 series
IEC 62271-1 NOTE Harmonized as EN 62271-1
IEC 62271-3 NOTE Harmonized as EN 62271-3
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the
relevant EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60068-2-1 2007 Environmental testing - Part 2–1: Tests - EN 60068-2-1 2007
Test A: Cold
IEC 60068-2-2 2007 Environmental testing - Part 2–2: Tests - EN 60068-2-2 2007
Test B: Dry heat
IEC 60068-2-14 2009 Environmental testing - Part 2–14: Tests - EN 60068-2-14 2009
Test N: Change of temperature
IEC 60068-2-30 2005 Environmental testing - Part 2–30: Tests - EN 60068-2-30 2005
Test Db: Damp heat, cyclic (12 h + 12 h
cycle)
IEC 60068-2-78 2012 Environmental testing - Part 2–78: Tests - EN 60068-2-78 2013
Test Cab: Damp heat, steady-state
IEC 60255-27 2013 Measuring relays and protection equipment EN 60255-27 2014
- Part 27: Product safety requirements
IEC 60664-1 2020 Insulation coordination for equipment EN IEC 60664-1 2020
within low-voltage supply systems - Part 1:
Principles, requirements and tests
IEC 61000-4-2 2008 Electromagnetic compatibility (EMC) - PartEN 61000-4-2 2009
4–2: Testing and measurement techniques
- Electrostatic discharge immunity test
IEC 61000-4-3 2006 Electromagnetic compatibility (EMC) - PartEN 61000-4-3 2006
4–3: Testing and measurement techniques
- Radiated, radio-frequency,
electromagnetic field immunity test
+ A1 2007  + A1 2008
+ A2 2010  + A2 2010
IEC 61000-4-4 2012 Electromagnetic compatibility (EMC) - PartEN 61000-4-4 2012
4–4: Testing and measurement techniques
- Electrical fast transient/burst immunity
test
IEC 61000-4-5 2014 Electromagnetic compatibility (EMC) - PartEN 61000-4-5 2014
4–5: Testing and measurement techniques
- Surge immunity test
IEC 61000-4-6 2013 Electromagnetic compatibility (EMC) - PartEN 61000-4-6 2014
4–6: Testing and measurement techniques
- Immunity to conducted disturbances,
induced by radio-frequency fields
IEC 61000-4-8 2009 Electromagnetic compatibility (EMC) - PartEN 61000-4-8 2010
4–8: Testing and measurement techniques
- Power frequency magnetic field immunity
test
IEC 61000-4-9 2016 Electromagnetic compatibility (EMC) - PartEN 61000-4-9 2016
4–9: Testing and measurement techniques
- Impulse magnetic field immunity test
IEC 61000-4-10 2016 Electromagnetic compatibility (EMC) - PartEN 61000-4-10 2017
4–10: Testing and measurement
techniques - Damped oscillatory magnetic
field immunity test
IEC 61000-4-11 2020 Electromagnetic compatibility (EMC) - PartEN IEC 61000-4-11 2020
4–11: Testing and measurement
techniques - Voltage dips, short
interruptions and voltage variations
immunity tests for equipment with input
current up to 16 A per phase
IEC 61000-4-13 - Electromagnetic compatibility (EMC) - PartEN 61000-4-13 -
4–13: Testing and measurement
techniques - Harmonics and
interharmonics including mains signalling
at a.c. power port, low frequency immunity
tests
IEC 61000-4-16 2015 Electromagnetic compatibility (EMC) - PartEN 61000-4-16 2016
4–16: Testing and measurement
techniques - Test for immunity to
conducted, common mode disturbances in
the frequency range 0 Hz to 150 kHz
IEC 61000-4-17 1999 Electromagnetic compatibility (EMC) - PartEN 61000-4-17 1999
4–17: Testing and measurement
techniques - Ripple on d.c. input power
port immunity test
+ A1 2001  + A1 2004
+ A2 2008  + A2 2009
IEC 61000-4-18 2006 Electromagnetic compatibility (EMC) - PartEN 61000-4-18 2007
4–18: Testing and measurement
techniques - Damped oscillatory wave
immunity test
- -  + corrigendum Sep. 2007
+ A1 2010  + A1 2010
IEC 61000-4-29 2000 Electromagnetic compatibility (EMC) - PartEN 61000-4-29 2000
4–29: Testing and measurement
techniques - Voltage dips, short
interruptions and voltage variations on d.c.
input power port immunity tests
IEC 61850-7-4 - Communication networks and systems for EN 61850-7-4 -
power utility automation - Part 7–4: Basic
communication structure - Compatible
logical node classes and data object
classes
IEC 61869-1 (mod) 2007 Instrument transformers - Part 1: General EN 61869-1 2009
requirements
IEC 61869-2 2012 Instrument transformers - Part 2: Additional EN 61869-2 2012
requirements for current transformers
IEC 61869-6 2016 Instrument transformers - Part 6: Additional EN 61869-6 2016
general requirements for low-power
instrument transformers
IEC 61869-9 2016 Instrument transformers - Part 9: Digital EN IEC 61869-9 2019
interface for instrument transformers
IEC 61869-10 2017 Instrument transformers - Part 10: EN IEC 61869-10 2018
Additional requirements for low-power
passive current transformers
IEC 61869-11 2017 Instrument transformers - Part 11: EN IEC 61869-11 2018
Additional requirements for low-power
passive voltage transformers
CISPR 11 - Industrial, scientific and medical equipment EN 55011 -
- Radio-frequency disturbance
characteristics - Limits and methods of
measurement
CISPR 32 2015 Electromagnetic compatibility of multimedia EN 55032 2015
equipment - Emission requirements
+ A1 2019  + A1 2020
- -  + A11 2020
IEC 61869-13 ®
Edition 1.0 2021-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Instrument transformers –
Part 13: Stand-alone merging unit (SAMU)

Transformateurs de mesure –
Partie 13: Concentrateur autonome (SAMU)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20 ISBN 978-2-8322-9284-6

– 2 – IEC 61869-13:2021 © IEC 2021
CONTENTS
FOREWORD . 4
INTRODUCTION . 7
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 11
4 Normal and special service conditions . 14
5 Ratings . 15
6 Design and construction . 23
7 Tests . 32
8 Rules for transport, storage, erection, operation and maintenance . 49
9 Safety . 49
Annex 13A (informative) Measurement chain accuracy class considerations . 50
Annex 13B (informative) Measurement examples of switching and lightning surge
voltage in gas-insulated switchgear . 52
Annex 13C (normative) Low-power instrument transformer inputs . 63
Bibliography . 67

Figure 1301 – Stand-alone merging unit (functional concept example) . 7
Figure 1302 – Stand-alone merging unit application example . 7
Figure 1303 – Illustration of the SAMU position in relation to other devices and
standards in the functional chain . 8
Figure 1304 – Specified input current time constant T . 13
I
Figure 1305 – Dynamic range concept example . 19
Figure 604 (modified) – Examples of subassembly subjected to EMC tests – Usual
structure used in HV AIS applications . 34
Figure 1306 – Gradual shutdown – Startup test . 38
Figure 1307 – C-O-C-O duty cycle . 39
Figure 13A.1 – SAMU application example . 50
Figure 13B.1 – Constructional example of GIS with typical surge voltage sources. 52
Figure 13B.2 – Measured 550 kV GIS construction . 53
Figure 13B.3 – Measurement results showing a switching surge peak voltage
magnitude caused by the DS operation in Figure 13B.2 . 54
Figure 13B.4 – Measured 275 kV GIS construction . 55
Figure 13B.5 – Switching and lightning surge voltage waveforms . 56
Figure 13B.6 – Switching surge voltage measurement setup on a 550 kV GIS
with/without an insulating flange surge absorber . 57
Figure 13B.7 – Switching surge voltage measurement results when the DS was
operated with/without the surge absorber . 58
Figure 13B.8 – CT secondary circuit configuration for the 500 kV GIS . 59
Figure 13B.9 – DS control circuit configuration for the 500 kV GIS test . 59
Figure 13B.10 – Waveforms of switching surge voltage at measured point I (see
Table 13B.3) . 60
Figure 13B.11 – Block diagram of the electronic VT with amplifier tested in the 500 kV
GIS system . 61

IEC 61869-13:2021 © IEC 2021 – 3 –
Figure 13B.12 – Lightning surge voltage as a function of surge absorbing capacitor value . 61
Figure 13B.13 – Lightning surge voltage as a function of coaxial cable length . 62

Table 1301 – Insulation requirements for analogue inputs . 16
Table 1302 – Measuring accuracy class 0,05 . 17
Table 1303 – Limits of current error and phase error for SAMU measuring accuracy
current channels . 18
Table 1304 – Limits of current errors for SAMU TPM class rated protection accuracy
current channels . 20
Table 1305 – Limits of voltage error and phase error for SAMU voltage channels . 21
Table 1306 – SAMU TCTR class settings . 23
Table 1307 – SAMU TVTR class settings . 23
Table 1308 – Immunity requirements and tests . 24
Table 1309 – Acceptance criteria for EMC immunity tests . 25
Table 1310 – Radiated emissions tests . 27
Table 1311 – Conducted emissions tests . 27
Table 1312 – SAMU rating plate markings . 28
Table 1313 – Ratings defined in accordance with IEC 61850-7-4 . 32
Table 10 – List of tests. 33
Table 1314 – Dry-heat test – Operational . 44
Table 1315 – Cold test – Operational . 44
Table 1316 – Dry-heat test at maximum storage temperature . 45
Table 1317 – Cold test at minimum storage temperature . 45
Table 1318 – Change of temperature (Cyclic temperature test) . 46
Table 1319 – Damp heat steady state test . 47
Table 1320 – Cyclic temperature with humidity test . 48
Table 13A.1 – Combined accuracy class table . 50
Table 13B.1 – Measurement results showing switching and lightning surge voltage
recorded for the setup in Figure 13B.4 . 55
Table 13B.2 – Measurement results of switching surge voltage on CT secondary circuit . 59
Table 13B.3 – Measurement results showing the switching surge voltage coupling to
the DS control circuit . 59
Table 13C.1 – ITRat setting units . 65
Table 13C.2 – SAMU rating plate marking modifications . 65

– 4 – IEC 61869-13:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSTRUMENT TRANSFORMERS –
Part 13: Stand-alone merging unit (SAMU)

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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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 61869-13 has been prepared by IEC technical committee 38:
Instrument transformers.
The text of this International Standard is based on the following documents:
FDIS Report on voting
38/634/FDIS 38/640/RVD
Full information on the voting for the approval of this International Standard 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 61869 series, published under the general title Instrument
transformers, can be found on the IEC website.

IEC 61869-13:2021 © IEC 2021 – 5 –
This Part 13 is to be used in conjunction with IEC 61869-9:2016, Digital interface for instrument
transformers, and IEC 61869-6:2016, Additional general requirements for low-power instrument
transformers, which, in turn, are based on IEC 61869-1:2007, General requirements.
This Part 13 follows the structure of IEC 61869-1:2007 and IEC 61869-6:2016 and supplements
or modifies their corresponding clauses.
When a particular clause/subclause of Part 1 or Part 6 is not mentioned in this Part 13, that
subclause applies. When this document states "addition", "modification" or "replacement", the
relevant text in Part 1 or Part 6 is to be adapted accordingly.
For additional clauses, subclauses, figures, tables, annexes or note, the following numbering
system is used:
– clauses, subclauses, tables, figures and notes that are numbered starting from 1301 are
additional to those in Part 1 and Part 6;
– additional annexes are lettered 13A, 13B, etc.
An overview of the planned set of standards at the date of publication of this document is given
below. The updated list of standards issued by IEC TC 38 is available at the website:
www.iec.ch.
– 6 – IEC 61869-13:2021 © IEC 2021
PRODUCT FAMILY STANDARDS PRODUCT PRODUCTS OLD
IEC STANDARD STANDARD
IEC IEC
61869-1 61869-2 ADDITIONAL REQUIREMENTS FOR 60044-1
CURRENT TRANSFORMERS 60044-6
GENERAL
REQUIREMENTS
61869-3 ADDITIONAL REQUIREMENTS FOR 60044-2
FOR
INDUCTIVE VOLTAGE TRANSFORMERS
INSTRUMENT
61869-4 ADDITIONAL REQUIREMENTS FOR 60044-3
TRANSFORMERS
COMBINED TRANSFORMERS
ADDITIONAL REQUIREMENTS FOR
61869-5 60044-5
CAPACITOR VOLTAGE TRANSFORMERS
61869-6 61869-7 ADDITIONAL REQUIREMENTS FOR 60044-7
ELECTRONIC VOLTAGE
ADDITIONAL
TRANSFORMERS
GENERAL
REQUIREMENTS 61869-8 ADDITIONAL REQUIREMENTS FOR 60044-8
FOR LOW-POWER
ELECTRONIC CURRENT
INSTRUMENT
TRANSFORMERS
TRANSFORMERS
61869-9 DIGITAL INTERFACE FOR INSTRUMENT
TRANSFORMERS
61869-10 ADDITIONAL REQUIREMENTS FOR
LOW-POWER PASSIVE CURRENT
TRANSFORMERS
61869-11 ADDITIONAL REQUIREMENTS FOR 60044-7
LOW-POWER PASSIVE VOLTAGE
TRANSFORMERS
61869-12 ADDITIONAL REQUIREMENTS FOR
COMBINED ELECTRONIC INSTRUMENT
TRANSFORMERS AND COMBINED
STAND-ALONE SENSORS
61869-13 STAND-ALONE MERGING UNIT
61869-14 ADDITIONAL REQUIREMENTS FOR
CURRENT TRANSFORMERS FOR DC
APPLICATIONS
61869-15 ADDITIONAL REQUIREMENTS FOR
VOLTAGE TRANSFORMERS FOR DC
APPLICATIONS
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.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

IEC 61869-13:2021 © IEC 2021 – 7 –
INTRODUCTION
General
This document is an IEC 61869 series product standard which defines additional requirements
for a stand-alone merging unit (SAMU).
The general block diagram showing a typical SAMU application example is given in Figure 1301.

Figure 1301 – Stand-alone merging unit (functional concept example)
An application example showing a three-phase dead tank circuit breaker equipped with bushing
type current transformers and a stand-alone merging unit mounted inside the breaker control
cabinet is shown in Figure 1302.

Figure 1302 – Stand-alone merging unit application example
The SAMU output may be used by many devices and is therefore of interest to multiple technical
committees in addition to TC 38, for example: TC 57: Power systems management and

– 8 – IEC 61869-13:2021 © IEC 2021
associated information exchange, TC 95: Measuring relays and protection equipment, TC 13:
Electrical energy measurement and control, TC 85: Measuring equipment for electrical and
electromagnetic quantities, and TC 17: High-voltage switchgear and controlgear, as shown in
Figure 1303.
Figure 1303 – Illustration of the SAMU position in relation
to other devices and standards in the functional chain
Position of this document in relation to IEC 61850 (all parts) of TC 57
IEC 61850 (all parts) is a series used to define various aspects of power utility communications.
Its applicability to this document is inherited through IEC 61869-9 which defines applicable
sample rates and a digital interface in accordance with IEC 61850-9-2 and related standards.
Position of this document in relation to IEC 60255 (all parts) of TC 95
IEC 60255 (all parts) standardizes the design and performance aspects applicable to measuring
relays and protection equipment used in the various fields of electrical engineering. Since the
SAMU is an integral part of the digital substation-based protection system, its EMC performance
and environmental aspects are considered for harmonization with IEC 60255-1, IEC 60255-26
and safety aspects defined in IEC 60255-27. SAMU outputs are inputs for protection functions
covered by the IEC 60255-1xx series.
Position of this document in relation to IEC 62052 (all parts) and IEC 62053 (all parts) of
TC 13
IEC 62052 (all parts) and IEC 62053 (all parts) provide standardization in the field of AC and
DC electrical energy measurement and control. Since the SAMU digital output may be used as
input to energy measurement devices, its accuracy and EMC performance aspects should be
considered.
Position of this document in relation to IEC 62271 (all parts) of TC 17
IEC 62271 (all parts) applies to AC switchgear and controlgear designed for indoor and/or
outdoor installation and for operation at service frequencies up to and including 60 Hz on
systems having rated voltages above 1 000 V. Similar to IEC 62271-3 which defines the
switchgear interface based on IEC 61850, this document defines the SAMU which may be
installed inside the same switchgear cabinet and is therefore subject to the same environmental
stress.
IEC 61869-13:2021 © IEC 2021 – 9 –
INSTRUMENT TRANSFORMERS –
Part 13: Stand-alone merging unit (SAMU)

1 Scope
Clause 1 of IEC 61869-1:2007 is replaced by the following:
This part of IEC 61869 is a product standard and covers only additional requirements for stand-
alone merging units (SAMUs) used for AC applications having rated frequencies from 15 Hz to
100 Hz. The digital output format specification is not covered by this document; it is
standardized in IEC 61869-9 as an application of IEC 61850, which specifies the power utility
communication architecture.
This document covers SAMUs having standardized analogue inputs (for example: 1 A, 5 A,
3,25 V / √3 or 100 V / √3) provided by instrument transformers compliant with relevant product
standards (e.g. IEC 61869-2 to IEC 61869-5, IEC 61869-7, IEC 61869-8, IEC 61869-10,
IEC 61869-11, IEC 60044-1 to IEC 60044-6, IEC 60185, IEC 60186, IEEE C57.13), and aims
to convert them to the digital output compliant with IEC 61869-9. Other input and output types
are outside the scope of this document. Appropriate SAMU functionality can be combined with
switchgear controller functionality defined in IEC 62271-3 or other IED functionality defined in
IEC 60255 (all parts).
Cyber security requirements are outside the scope of this document and are covered by the
IEC 62351 series.
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.
Clause 2 of IEC 61869-1:2007 is applicable with the following additions:
IEC 60068-2-1:2007, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2:2007, Environmental testing – Part 2-2: Tests – Test B: Dry heat
IEC 60068-2-14:2009, Environmental testing – Part 2-14: Tests – Test N: Change of
temperature
IEC 60068-2-30:2005, Environmental testing – Part 2-30: Tests – Test Db: Damp heat, cyclic
(12 + 12 h cycle)
IEC 60068-2-78:2012, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat, steady
state
IEC 60255-27:2013, Measuring relays and protection equipment – Part 27: Product safety
requirements
IEC 60664-1:2020, Insulation coordination for equipment within low-voltage supply systems –
Part 1: Principles, requirements and tests

– 10 – IEC 61869-13:2021 © IEC 2021
IEC 61000-4-2:2008, Electromagnetic compatibility (EMC) – Part 4-2: Testing and
measurement techniques – Electrostatic discharge immunity test
IEC 61000-4-3:2006, Electromagnetic compatibility (EMC) – Part 4-3: Testing and
measurement techniques – Radiated, radio-frequency, electromagnetic field immunity test
IEC 61000-4-3:2006/AMD1:2007
IEC 61000-4-3:2006/AMD2:2010
IEC 61000-4-4:2012, Electromagnetic compatibility (EMC) – Part 4-4: Testing and
measurement techniques – Electrical fast transient/burst immunity test
IEC 61000-4-5:2014, Electromagnetic compatibility (EMC) – Part 4-5: Testing and
measurement techniques – Surge immunity test
IEC 61000-4-6:2013, Electromagnetic compatibility (EMC) – Part 4-6: Testing and
measurement techniques – Immunity to conducted disturbances, induced by radio-frequency
fields
IEC 61000-4-8:2009, Electromagnetic compatibility (EMC) – Part 4-8 Testing and measurement
techniques – Power frequency magnetic field immunity test
IEC 61000-4-9:2016, Electromagnetic compatibility (EMC) – Part 4-9 Testing and measurement
techniques – Impulse magnetic field immunity test
IEC 61000-4-10:2016, Electromagnetic compatibility (EMC) – Part 4-10 Testing and
measurement techniques – Damped oscillatory magnetic field immunity test
IEC 61000-4-11:2020, Electromagnetic compatibility (EMC) – Part 4-11 Testing and
measurement techniques – Voltage dips, short interruptions and voltage variations immunity
tests for equipment with input current up to 16 A per phase
IEC 61000-4-13, Electromagnetic compatibility (EMC) – Part 4-13: Testing and measurement
techniques – Harmonics and interharmonics including mains signalling at a.c. power port, low
frequency immunity tests
IEC 61000-4-16:2015, Electromagnetic compatibility (EMC) – Part 4-16 Testing and
measurement techniques – Test for immunity to conducted, common mode disturbances in the
frequency range 0 Hz to 150 kHz
IEC 61000-4-17:1999, Electromagnetic compatibility (EMC) – Part 4-17: Testing and
measurement techniques – Ripple on d.c. input power port immunity test
IEC 61000-4-17:1999/AMD1:2001
IEC 61000-4-17:1999/AMD1:2008
IEC 61000-4-18:2006, Electromagnetic compatibility (EMC) – Part 4-18 Testing and
measurement techniques – Damped oscillatory wave immunity test,
IEC 61000-4-18:2006/AMD1:2010
IEC 61000-4-29:2000, Electromagnetic compatibility (EMC) – Part 4-29 Testing and
measurement techniques – Voltage dips, short interruptions and voltage variations on d.c. input
power port immunity tests
IEC 61850-7-4, Communication networks and systems for power utility automation – Part 7-4:
Basic communication structure – Compatible logical node classes and data object classes
IEC 61869-1:2007, Instrument transformers – Part 1: General requirements

IEC 61869-13:2021 © IEC 2021 – 11 –
IEC 61869-2:2012, Instrument transformers – Part 2: Additional requirements for current
transformers
IEC 61869-6:2016, Instrument transformers – Part 6: Additional general requirements for low-
power instrument transformers
IEC 61869-9:2016, Instrument transformers – Part 9: Digital interface for instrument
transformers
IEC 61869-10:2017, Instrument transformers – Part 10: Additional requirements for low-power
passive current transformers
IEC 61869-11:2017, Instrument transformers – Part 11: Additional requirements for low-power
passive voltage transformers
CISPR 11, Industrial, scientific and medical equipment – Radio-frequency disturbance
characteristics – Limits and methods of measurement
CISPR 32:2015, Electromagnetic compatibility of multimedia equipment – Emission
requirements
CISPR 32:2015/AMD1:2019
3 Terms and definitions
Clause 3 of IEC 61869-1:2007, Clause 3 of IEC 61869-6:2016 and Clause 3 of
IEC 61869-9:2016 apply, with the following additions:
3.1 General terms and definitions
3.1.1301
port
access to a device or network where electromagnetic energy or signals may be supplied or
received or where the device or network variables may be observed or measured
EXAMPLE Auxiliary power supply terminals.
[SOURCE: IEC 60050-131:2002, 131-12-60, modified – Added example, deleted note.]
3.1.1302
digital channel
channel
digital representation describing a single measurement quantity
EXAMPLE Phase current, phase voltage.
Note 1 to entry: Channels are individually rated and may contain a mathematical combination of multiple inputs
(e.g. calculated neutral current).
Note 2 to entry: Multiple channels are grouped into a single stream and presented at the device digital output.
3.1.1303
digital stream
stream
group of channels brought together into a single digital message
Note 1 to entry: All channels in the stream share a common time stamp and a common sample rate in accordance
with IEC 61869-9.
– 12 – IEC 61869-13:2021 © IEC 2021
3.1.1304
channel group
set of channels with a common specification
Note 1 to entry: For example, set of three phase voltages or currents. All channels in the group share the same set
of rating plate specifications. If the neutral voltage or current channel shares the same specification as the individual
phases, then it is included in the same group.
3.1.1305
analogue input
device input intended to be fed by the secondary circuit of an instrument transformer with
analogue secondary signal
3.2 Terms and definitions related to dielectric ratings and voltages
3.2.1301
rated input voltage
U
ir
RMS value of the voltage on which the performance of a device voltage input is based
Note 1 to entry: This value may be defined as a range.
3.2.1302
rated voltage factor
F
V
multiplying factor to be applied to the rated primary voltage to determine the maximum voltage
at which a transformer must comply with the relevant thermal requirements for a specified time
and with the relevant accuracy requirements
Note 1 to entry: For SAMUs, the term primary voltage is understood as the input voltage.
[SOURCE: IEC 60050-321:1986, 321-03-12, modified – The symbol and the note have been
added.]
3.2.1303
rated insulation voltage
RMS withstand voltage value assigned by the manufacturer to the equipment or to a part of it,
characterizing the specified (long-term) withstand capability of its insulation
Note 1 to entry: The rated insulation voltage is not necessarily equal to the rated voltage of equipment which is
primarily related to functional performance.
[SOURCE: IEC 60050-312:2014, 312-06-02, modified – Deleted "rated value of the" and the
word "value" added.]
3.3 Terms and definitions related to current ratings
3.3.1301
rated primary current
I
pr
RMS value of the primary current on which the performance of the instrument transformer is
based
Note 1 to entry: A SAMU is not connected to the power system primary. For SAMUs, the term rated primary current
is interpreted as rated input current.
3.3.1302
rated short-circuit current
I
psc
RMS value of the AC component of a transient current on which the accuracy performance of
the device is based
IEC 61869-13:2021 © IEC 2021 – 13 –
Note 1 to entry: While I is related to the thermal limit, I is related to the accuracy limit. Usually, I is smaller
th psc psc
than I .
th
Note 2 to entry: For current transformers rated short-circuit current is applicable to the primary winding. In the case
of SAMUs, the rated short-circuit current is applicable to the current input.
3.3.1303
rated symmetrical short-circuit current factor
K
ssc
ratio of the rated short-circuit current to the rated primary current
Note 1 to entry: SAMU inputs are not connected to the power system primary. Rated primary current in the case of
SAMUs is interpreted as the rated input current.
I
psc
K =
ssc
I
pr
3.4 Terms and definitions related to accuracy
3.4.1301
specified input current time constant
T
I
specified value of the time constant of the DC component of the rated short-circuit current I
PSC
on which the transient performance of the device is based
Note 1 to entry: T is typically a result of the power system primary time constant T combined with the CT secondary
I P
loop time constant T (both are defined in IEC 61869-2). An example is shown in Figure 1304. T is used to specify
s I
the dynamic response performance.

Figure 1304 – Specified input current time constant T
I
3.4.1302
input filter time constant
T
sec
value of the device AC coupled input circuit high-pass filter cut-off frequency f reported in the
c
form of a time constant
– 14 – IEC 61869-13:2021 © IEC 2021
T =
sec
2πf
c
Note 1 to entry: For device inputs built using auxiliary current transformers, T is equal to the auxiliary transformer
sec
secondary loop time constant.
3.4.1303
measuring class dynamic range upper limit factor

K
I
max
ratio of the maximum input current to the rated input current defining the range over which the
stated accuracy applies
Note 1 to entry: This factor is expressed in per cent of rated current.
3.4.1304
measuring class dynamic range lower limit factor

K
I
min
ratio of the minimum input current to the rated input current defining the range over which the
stated accuracy applies
Note 1 to entry: This factor is expressed in per cent of rated current.
3.4.1305
clipping
form of limiting in which all the instantaneous values of a signal exceeding a predetermined
threshold value are reduced to values close to that of the threshold, all other instantaneous
values of the signal being preserved
[SOURCE: IEC 60050-702:1992, 702-04-33]
3.7 Index of abbreviations and symbols
Subclause 3.7 of IEC 61869-6:2016 is applicable with the following additions:
I rated primary current
pr
U rated input voltage
ir
F rated voltage factor
V
K
measuring class dynamic range upper limit factor
I
max
K
measuring class dynamic range lower limit factor
I
min
K rated symmetrical short-circuit-current factor
SSC
T specified input current time constant
I
T input filter time constant
sec
DR dynamic range
PEB protection by equipotential bonding

4 Normal and special service conditions
4.3 Special service conditions
4.3.3 Ambient temperature
Subclause 4.3.3 of IEC 61869-1:2007 is applicable with the following addition:

IEC 61869-13:2021 © IEC 2021 – 1
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