Instrument transformers - Part 14: Additional requirements for current transformers for DC applications

IEC 61869-14:2018 provides all requirements specific to current transformers to be used in DC applications (DCCTs), whatever the technology used. The output signal can be analogue or digital.
It is applicable to newly manufactured current transformers used for measuring, protection and/or control applications in DC power systems with a rated voltage above 1,5 kV.
The general configuration of a single-pole low-power instrument transformer is described in Figure 601 of IEC 61869-6:2016.
The DCCTs intended for current measurement in the transistor branch of the VSC valve (referred to as CT4a and CT4b in Figure 1403 and Table 1402) are not covered by this document, and will be considered in a future revision.
IEC 61869-14:2018 applies to current transformers intended to be used in DC applications with at least one of the following functions:
• measure DC current (with significant harmonics);
• withstand DC voltage.
Depending on the position on the DC system, different kinds of application exist, which are briefly described below, together with the approximate voltage or current wave shape.

Transformateurs de mesure - Partie 14: Exigences supplémentaires concernant les transformateurs de courant pour application en courant continu

IEC 61869-14:2018 couvre toutes les exigences particulières concernant les transformateurs de courant utilisés dans les applications en courant continu (DCCTs), quelle que soit la technologie utilisée. Le signal de sortie peut être analogique ou numérique.
Elle s'applique aux transformateurs de courant fabriqués récemment et utilisés pour des applications de mesure, de protection et/ou de commande sur des systèmes d'alimentation électrique en courant continu dont la tension assignée est supérieure à 1,5 kV.
La configuration générale d'un transformateur de mesure de faible puissance unipolaire est décrite à la Figure 601 de l'IEC 61869-6:2016.
Les transformateurs de courant continu destinés aux mesures de courant dans la branche du transistor de la valve VSC (dénommés CT4a et CT4b à la Figure 1403 et au Tableau 1402) ne sont pas couverts par le présent document et seront traités lors d'une prochaine révision.
IEC 61869-14:2018 s'applique aux transformateurs de courant destinés à être utilisés dans les applications en courant continu avec l'une des fonctions suivantes au moins:
• mesurage du courant continu (avec des harmoniques élevées);
• tension continue de tenue.
Selon la position du système à courant continu, différents types d'applications existent. Ils sont décrits brièvement ci-dessous, ainsi que la tension approximative ou la forme d'onde du courant.

Električne inštalacije zgradb – 7. del: Zahteve za posebne inštalacije in lokacije – 713. oddelek: Pohištvo

General Information

Status
Published
Publication Date
16-Jul-2018
Current Stage
PPUB - Publication issued
Completion Date
17-Jul-2018

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SLOVENSKI STANDARD
SIST IEC 60364-7-713:2000
01-februar-2000

(OHNWULþQHLQãWDODFLMH]JUDGE±GHO=DKWHYH]DSRVHEQHLQãWDODFLMHLQORNDFLMH±

RGGHOHN3RKLãWYR

Electrical installations of buildings - Part 7: Requirements for special installations and

locations - Section 713: Furniture

Installations électriques des bâtiments - Partie 7: Règles pour les installations et

emplacements spéciaux - Section 713: Mobilier
Ta slovenski standard je istoveten z: IEC 60364-7-713
ICS:
91.140.50 Sistemi za oskrbo z elektriko Electricity supply systems
97.140 Pohištvo Furniture
SIST IEC 60364-7-713:2000 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST IEC 60364-7-713:2000
---------------------- Page: 2 ----------------------
SIST IEC 60364-7-713:2000
NORME CEI
IEC
INTERNATIONALE
364-7-713
INTERNATIONAL
Première édition
STAN DARD First edition
1996-02
bâtiments
Installations électriques des —
Partie 7:
Règles pour les installations et emplacements
spéciaux —
Section 713: Mobilier
Electrical installations of buildings —
Part 7:
Requirements for special installations
and locations —
Section 713: Furniture
© CEI 1996 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

utilisée sous quelque forme que ce soit et par aucun pro- any form or by any means, electronic or mechanical,

cédé, électronique ou mécanique, y compris la photocopie et including photocopying and microfilm, without permission

les microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher.
Genève, Suisse

Bureau Central de la Commission Electrotechnique Internationale 3, rue de Varembé

Commission Electrotechnique Internationale CODE PRIX
International Electrotechnical Commission
PRICE CODE
IEC Me*ayHapomiaa 3nefsrpoyexHH4ecnaR HoMuccus
voir catalogue en vigueur
Pour prix,
For price, see current catalogue
---------------------- Page: 3 ----------------------
SIST IEC 60364-7-713:2000
– 3 –
364-7-713 © IEC:1996
CONTENTS
Page
FOREWORD 5
Clause
700.1 Introduction 7
713 Furniture 7
713.1 General 7
713.1.1 Scope 7
713.1.2 Normative references 7
713.1.3 Definitions
11 Selection and erection of electrical equipment
713.5
713.51 Common rules
713.52 Wiring systems
713.55 Other equipment
---------------------- Page: 4 ----------------------
SIST IEC 60364-7-713:2000
364-7-713 © IEC:1996 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
ELECTRICAL INSTALLATIONS OF BUILDINGS -
Part 7: Requirements for special installations and locations -
Section 713: Furniture
FOREWORD

1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization

comprising all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The IEC collaborates closely with the International

Organization for Standardization (ISO) in accordance with conditions determined by agreement between the

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2) The formal decisions or agreements of the 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 National Committees.

3) The documents produced have the form of recommendations for international use and are published in the

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subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 364-7-713 has been prepared by IEC technical committee 64:

Electrical installations of buildings.
The text of this standard is based on the following documents:
FDIS Report on voting
64/811/FDIS 64/835/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.
---------------------- Page: 5 ----------------------
SIST IEC 60364-7-713:2000
364-7-713 © IEC:1996 – 7 -
ELECTRICAL INSTALLATIONS OF BUILDINGS -
Part 7: Requirements for special installations and locations -
Section 713: Furniture
700.1 Introduction

The requirements of part 7 supplement, modify or replace the general requirements of the other

parts of IEC 364. The numbers following the particular number of the section of part 7 are

those of the corresponding parts, chapters, sections or clauses of IEC 364. The absence of a

reference to a chapter, section or clause means that the corresponding general requirements

are applicable.
713 Furniture
713.1 General
713.1.1 Scope

The particular requirements of this section apply to the wiring system of furniture (and similar

fitments) which is connected to the electrical installation.

Examples are beds, cupboards, desks and shop display cases, in which electrical equipment

such as luminaries, socket-outlets, switching devices and wiring systems are installed.

The requirements of this section apply to furniture connected by fixed wiring to the electrical

installation of the building and also to prefabricated furniture and furniture connected by means

of a plug and socket-outlet unless these items are the subject of other IEC publications.

Electrical equipment of furniture shall be connected to a single-phase supply <240 V, and the

total load current shall not exceed 16 A.

The requirements do not apply to electrical appliances and equipment specifically designed for

installation in furniture and which are the subject of other IEC publications, for example radios,

TV receivers, refrigerators and laboratory tables, installe
...

IEC 61869-14
Edition 1.0 2018-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Instrument transformers –
Part 14: Additional requirements for current transformers for DC applications
Transformateurs de mesure –
Partie 14: Exigences supplémentaires concernant les transformateurs de
courant pour application en courant continu
IEC 61869-14:2018-07(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 61869-14
Edition 1.0 2018-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Instrument transformers –
Part 14: Additional requirements for current transformers for DC applications
Transformateurs de mesure –
Partie 14: Exigences supplémentaires concernant les transformateurs de
courant pour application en courant continu
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20 ISBN 978-2-8322-5803-3

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 61869-14:2018 © IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 7

1 Scope ............................................................................................................................ 11

2 Normative references .................................................................................................... 11

3 Terms and definitions .................................................................................................... 11

5 Ratings .......................................................................................................................... 16

6 Design and construction ................................................................................................ 20

7 Tests ............................................................................................................................. 25

Annex 14A (informative) Equivalent thermal current in CTs for DC application ..................... 37

14A.1 General ................................................................................................................. 37

14A.2 Current harmonic content ...................................................................................... 37

14A.3 Losses in primary conductor due to harmonic content ........................................... 38

14A.4 Thermal test with AC current ................................................................................. 40

Annex 14B (informative) Proposed rated insulation level applicable to current

transformers for DC application............................................................................................. 41

Bibliography .......................................................................................................................... 42

Figure 1401 – Example of LCC scheme .................................................................................. 7

Figure 1402 – Typical scheme for VSC – symmetrical monopole ............................................. 8

Figure 1403 – Typical scheme for VSC – asymmetrical monopole or bipole ............................ 9

Figure 1404 – Typical step responses of a system ................................................................ 14

Figure 1405 – Accuracy limits of a DCCT .............................................................................. 19

Figure 1406 – Polarity reversal test profile ............................................................................ 30

Figure 1407 – Measurement of the step response time ......................................................... 32

Figure 14A.1 – Typical waveform of current flowing in the primary conductor for LCC

applications .......................................................................................................................... 37

Figure 14A.2 – The two terms that make up the total losses in the primary conductor ........... 39

Figure 14A.3 – Additional losses in conductors due to typical current harmonics .................. 40

Figure 14A.4 – Power-frequency losses in conductors compared to DC losses ..................... 40

Table 1401 – Current and voltage in current transformers for LCC application ........................ 8

Table 1402 – Current and voltage in current transformers for VSC application ...................... 10

Table 3 – Partial discharge test voltages and permissible levels ........................................... 17

Table 1403 – Limits of ratio error for DCCT (classes from 0,1 to 1) ...................................... 19

Table 7 – Static withstand test loads ..................................................................................... 21

Table 8 – Arc fault duration and performance criteria ............................................................ 22

Table 1404 – Markings of terminals ...................................................................................... 23

Table 1405 – Rating plate marking for common rating plate .................................................. 24

Table 1406 – Rating plate marking for each secondary converter ......................................... 24

Table 1407 – Rating plate marking for auxiliary power supply ............................................... 25

---------------------- Page: 4 ----------------------
IEC 61869-14:2018 © IEC 2018 – 3 –

Table 10 – List of tests.......................................................................................................... 26

Table 14A.1 – Typical harmonic current values (800 kV LCC) ............................................... 38

Table 14B.1 – Proposed rated primary terminal insulation levels for current

transformers for DC application............................................................................................. 41

---------------------- Page: 5 ----------------------
– 4 – IEC 61869-14:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSTRUMENT TRANSFORMERS –
Part 14: Additional requirements for current
transformers for DC applications
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.

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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

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services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

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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 61869-14 has been prepared by IEC technical committee 38:

Instrument transformers.
The text of this standard is based on the following documents:
FDIS Report on voting
38/560/FDIS 38/565/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.

---------------------- Page: 6 ----------------------
IEC 61869-14:2018 © IEC 2018 – 5 –

A list of all parts in the IEC 61869 series, published under the general title Instrument

transformers, can be found on the IEC website.

This Part 14 is to be used in conjunction with, and is based on, IEC 61869-1:2007, General

requirements, and IEC 61869-6:2016, Additional general requirements for low-power

instrument transformers – however the reader is encouraged to use the most recent editions.

This Part 14 follows the structure of IEC 61869-1:2007 and IEC 61869-6:2016 and
supplements or modifies their corresponding clauses.

When a subclause of Part 1 or Part 6 is not mentioned in this Part 14, that subclause applies.

When this standard 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 notes, the following numbering

system is used:

• clauses, subclauses, tables, figures and notes that are numbered starting from 1401 are

additional to those in Part 1 and Part 6;
• additional annexes are lettered 14A, 14B, 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
PRODUCT FAMILY STANDARDS PRODUCT PRODUCTS OLD
STANDARD STANDARD
61869-1 61869-2 ADDITIONAL REQUIREMENTS FOR 60044-1
CURRENT TRANSFORMERS 60044-6
GENERAL
REQUIREMENTS
61869-3 ADDITIONAL REQUIREMENTS FOR 60044-2
INDUCTIVE VOLTAGE TRANSFORMERS
61869-4 ADDITIONAL REQUIREMENTS FOR 60044-3
COMBINED TRANSFORMERS
61869-5 ADDITIONAL REQUIREMENTS FOR 60044-5
CAPACITIVE VOLTAGE TRANSFORMERS
ADDITIONAL REQUIREMENTS FOR
61869-6 61869-7 60044-7
ELECTRONIC VOLTAGE TRANSFORMERS
ADDITIONAL
GENERAL 61869-8 ADDITIONAL REQUIREMENTS FOR 60044-8
REQUIREMENTS
ELECTRONIC CURRENT
FOR LOW-POWER
TRANSFORMERS
INSTRUMENT
DIGITAL INTERFACE FOR INSTRUMENT
61869-9
TRANSFORMERS
TRANSFORMERS
61869-10 ADDITIONAL REQUIREMENTS FOR LOW-
POWER PASSIVE CURRENT
TRANSFORMERS
61869-11 ADDITIONAL REQUIREMENTS FOR LOW- 60044-7
POWER PASSIVE VOLTAGE
TRANSFORMERS
61869-12 ADDITIONAL REQUIREMENTS FOR
COMBINED ELECTRONIC INSTRUMENT
TRANSFORMER OR COMBINED LOW-
POWER PASSIVE TRANSFORMERS
61869-13 STAND ALONE MERGING UNIT
ADDITIONAL REQUIREMENTS FOR
61869-14
CURRENT TRANSFORMERS FOR DC
APPLICATIONS
61869-15 ADDITIONAL REQUIREMENTS FOR
VOLTAGE TRANSFORMERS FOR DC
APPLICATIONS
---------------------- Page: 7 ----------------------
– 6 – IEC 61869-14:2018 © IEC 2018

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 publication 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.
---------------------- Page: 8 ----------------------
IEC 61869-14:2018 © IEC 2018 – 7 –
INTRODUCTION
General

This document applies to current transformers intended to be used in DC applications with at

least one of the following functions:
• measure DC current (with significant harmonics);
• withstand DC voltage.

Depending on the position of the current transformer on the DC system, different kinds of

application exist, which are briefly described below, together with the approximate voltage or

current wave shape.
Line-commutated converters (LCC)

Line-commutated converters (LCC) are based on thyristor converters (see Figure 1401). They

are characterized by a single direction of current flow, and a voltage polarity reversal

possibility. Significant voltage and current harmonics exist up to frequencies of about 3 kHz to

4 kHz.
Figure 1401 – Example of LCC scheme
We distinguish three different current-measurement functions:
• CT1: measurement of the current at the AC side of the converter;
• CT2: measurement of the current at the DC side of the converter;
• CT3: measurement of the current in the DC filter.

Table 1401 gives an overview of the current and voltage waveshapes as well as the main

characteristics of the different applications of the CT.
---------------------- Page: 9 ----------------------
– 8 – IEC 61869-14:2018 © IEC 2018
Table 1401 – Current and voltage in current transformers for LCC application
Current Voltage Characteristics
CT1 AC current
AC + DC voltage
Large amount of current harmonics
Mainly for protection purposes
CT2 Pure DC application
High-accuracy measurement
Harmonics measurement
Metering, control and protection
purposes
CT3 DC voltage stress with harmonics
DC current = 0
Harmonics measurement
Mainly for protection purposes
Voltage-source converters (VSC)

Voltage-source converters (VSC) are based on transistor converters. They are characterized

by a bi-directional current flow and a single voltage polarity. Voltage and current harmonics

exist up to frequencies of about 20 kHz.

Two variants of VSC schemes exist: symmetrical monopoles (using one single converter) and

asymmetrical monopole or bipole (with one converter for each polarity).
Both schemes are shown in Figure 1402 and Figure 1403.
Figure 1402 – Typical scheme for VSC – symmetrical monopole
---------------------- Page: 10 ----------------------
IEC 61869-14:2018 © IEC 2018 – 9 –
Figure 1403 – Typical scheme for VSC – asymmetrical monopole or bipole
We distinguish three different current-measurement functions:
• CT4: measurement of the current in the transistor branches of the converter.
The CT can be placed before (CT4a) or after the transistor branch (CT4b);
• CT2: measurement of the current at the DC side of the converter;

• CT3: measurement of the current in the DC filter (not always present in this scheme).

Table 1402 gives an overview of the current and voltage waveshapes as well as the main

characteristics of the different applications of the CT.
---------------------- Page: 11 ----------------------
– 10 – IEC 61869-14:2018 © IEC 2018
Table 1402 – Current and voltage in current transformers for VSC application
Current Voltage Characteristics
CT2 Pure DC application
High accuracy
measurement
Harmonics measurement
Metering, control and
protection purposes
Short step response time
CT3 DC voltage stress
DC current = 0
Harmonics measurement
Mainly for protection
purposes
CT4a Symmetrical monopole: Pure AC voltage or DC +
AC voltage
DC + AC current
High-accuracy
measurement
Short step response time
Asymmetrical monopoles /
bipoles:
CT4b DC voltage stress
DC + AC current
High-accuracy
measurement
Short step response time
---------------------- Page: 12 ----------------------
IEC 61869-14:2018 © IEC 2018 – 11 –
INSTRUMENT TRANSFORMERS –
Part 14: Additional requirements for current
transformers for DC applications
1 Scope

This part of IEC 61869 provides all requirements specific to current transformers to be used in

DC applications (DCCTs), whatever the technology used. The output signal can be analogue

or digital.

It is applicable to newly manufactured current transformers used for measuring, protection

and/or control applications in DC power systems with a rated voltage above 1,5 kV.

The general configuration of a single-pole low-power instrument transformer is described in

Figure 601 of IEC 61869-6:2016.

The DCCTs intended for current measurement in the transistor branch of the VSC valve

(referred to as CT4a and CT4b in Figure 1403 and Table 1402) are not covered by this

document, and will be considered in a future revision.
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 61869-6:2016 is applicable, with the following additions and modifications:

IEC TS 60815-4:2016, Selection and dimensioning of high-voltage insulators intended for use

in polluted conditions – Part 4: Insulators for DC systems

IEC TS 61245:2015, Artificial pollution tests on high-voltage ceramic and glass insulators to

be used on DC systems

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
3 Terms and definitions

Clause 3 of IEC 61869-1:2007, of IEC 61869-6:2016 and of IEC 61869-9:2016 are applicable

with the following additions and modifications.
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3.1 General definitions
3.1.1401
instrument transformer for DC application

instrument transformer intended to be used in DC applications with at least one of the

following functions:
• measure DC current or DC voltage (with significant harmonics);
• withstand DC voltage.
3.1.1402
current transformer for DC application
DCCT

instrument transformer for DC application in which the secondary signal, under normal

conditions of use, is substantially proportional to the primary current
Note 1 to entry: The different applications are described in the introduction.
3.2 Definitions related to dielectric ratings
3.2.2
highest voltage for equipment
Definition 3.2.2 of IEC 61869-1:2007 is replaced by the following one:

highest value of DC voltage for which the equipment is designed to operate continuously, in

respect of its insulation as well as other characteristics that relate to this voltage

3.3 Definitions related to current ratings
3.3.1401
DC overload current

overcurrent occurring in an electric circuit, which is not caused by a short-circuit or an earth

fault

Note 1 to entry: The DC overload current is specified by the customer in terms of value and duration.

[SOURCE: IEC 60050-826:2004, 826-11-15, modified – “DC” added in the term and Note 1 to

entry added.]
3.3.1402
short-time overload current
sov
DC overload current occurring for a duration shorter than one minute
3.3.1403
long-time overload current
lov
DC overload current occurring for a duration of minutes or hours

Note 1 to entry: Different values of long-time overload can be specified for different durations.

3.3.1404
maximum peak fault current

maximum peak value of current occurring during a fault condition of the DC power system

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IEC 61869-14:2018 © IEC 2018 – 13 –
3.4 Definitions related to accuracy
3.4.1401
Absolute error

error (expressed in A) that a current transformer introduces into the measurement and which

arises from the fact that the actual transformation ratio is not equal to the rated transformation

ratio
Note 1 to entry: The absolute error is defined by the following formula:
ε = K ⋅ U – I
A r s p
where
K is the rated transformation ratio;
I is the DC value of the actual primary current in steady state;
U is the DC value of the output voltage.
3.5 Definitions related to other ratings
3.5.1401
step response

duration between the instant when the measurand (or quantity supplied) is subjected to a

specified abrupt change and the instant when the indication (or quantity supplied) reaches,

and remains within specified limits of, its final steady-state value
Note 1 to entry: See graphical explanation in Figure 1404.
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For periodic behaviour
For aperiodic behaviour
u Input variable
U Initial value of the input variable
U Step height of the input variable
v Output variable
V , V Steady-state values before and after application of the step
0 ∞
v Overshoot
Specified tolerance limit
2 ∆v
T Step response time
T Settling time
T Dead time
Figure 1404 – Typical step responses of a system
Note 2 to entry: The dead time includes the delay time.

[SOURCE: IEC 60050-311:2001, 311-06-04 and IEC 60050-351:2013, 351-45-27 modified –

Note 1 to entry has been added; the notes of the sources have been deleted.]
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3.5.1402
step response time

for a step response, the duration of the time interval between the instant of the step change of

an input variable and the instant when the output variable reaches for the first time a specified

percentage of the difference between the final and the initial steady-state values

Note 1 to entry: The step response time includes the delay time of the current transformer.

[SOURCE: IEC 60050-351:2013, 351-45-36, modified – Note 1 to entry has been modified

and the figure has been deleted.]
3.5.1403
settling time

for a step response, the duration of the time interval between the instant of the step change of

an input variable and the instant when the difference between the step response and their

steady-state value remains smaller than the transient value tolerance

Note 1 to entry: The settling time includes the delay time of the current transformer.

[SOURCE: IEC 60050-351:2013, 351-45-37, modified – Note 1 to entry has been modified

and the figure has been deleted.]
3.5.1404
overshoot

for a step response of a transfer element, the maximum transient deviation from the final

steady-state value of the output variable, usually expressed in percent of the difference

between the final and the initial steady-state values and for reference-variable step respon

...

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