IEC 61869-14:2018

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

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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

– 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

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

– 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
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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.

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
– 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.
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.

– 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

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.

– 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
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.

– 12 – IEC 61869-14:2018 © IEC 2018
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
U
m
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
I
sov
DC overload current occurring for a duration shorter than one minute
3.3.1403
long-time overload current
I
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
I
sc
maximum peak value of current occurring during a fault condition of the DC power system

3.4 Definitions related to accuracy
3.4.1401
Absolute error
ε
A
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;
r
I is the DC value of the actual primary current in steady state;
p
U is the DC value of the output voltage.
s
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.

– 14 – IEC 61869-14:2018 © IEC 2018

a
For periodic behaviour
b
For aperiodic behaviour
u Input variable
U Initial value of the input variable
U Step height of the input variable
s
v Output variable
V , V Steady-state values before and after application of the step
0 ∞
v Overshoot
m
Specified tolerance limit
2 ∆v
s
T Step response time
sr
T Settling time
s
T Dead time
t
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.]

3.5.1402
step response time
T
sr
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
T
s
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
v
m
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 response
or disturbance-variable step response of a control system the maximum transient deviation
from the desired value
[SOURCE: IEC 60050-351:2013, 351-45-38, modified – Note 1 to entry and the figure have
been deleted.]
– 16 – IEC 61869-14:2018 © IEC 2018
3.7 Index of abbreviations and symbols
The table in 3.7 of IEC 61869-6:2016 is replaced by the following one:
DCCT current transformer for DC application
F mechanical load
I maximum supply current
amax
I rated supply current
ar
I rated continuous thermal current
cth
I rated primary current
pr
I long-time overload current
lov
I short-time overload current
sov
I maximum peak fault current
sc
IT instrument transformer
K accuracy limit factor
ALF
K extended primary current factor
pcr
K rated transformation ratio
r
R rated burden
br
t delay time
d
t rated delay time
dr
T settling time
s
T step response time
sr
T dead time
t
U auxiliary power supply voltage
ar
U highest voltage for equipment
m
U rated secondary voltage
sr
v overshoot
m
ε ratio error
absolute error
ε
A
5 Ratings
5.1 General
Subclause 5.1 of IEC 61869-1:2007 is replaced by the following one:
If applicable, the ratings of DC current transformers, including their auxiliary equipment, shall
be selected from the following ones:
• highest voltage for equipment (U );
m
• rated primary current (I );
pr
• rated delay time (t );
dr
• rated continuous thermal current (I );
cth
• long-time overload current (I );
lov
• short time overload current (I );
sov
• maximum peak fault current (I );
sc
• rated secondary voltage (U );
sr
• insulation level;
• rated burden (R );
br
• rated accuracy class;
• accuracy limit factor (K );
ALF
);
• rated extended primary current factor (K
pcr
• rated step response time (T ).
sr
The rating applies at the standardized reference atmosphere (temperature 20 °C,
pressure 101,3 kPa, and humidity 11 g/m ) as specified in IEC 60071-1.
NOTE The ratings are specified by the purchaser depending on the characteristics of the whole DC system
application.
5.2 Highest voltage for equipment
Subclause 5.2 of IEC 61869-1:2007 is replaced by the following one:
There are no standard values for highest voltage for equipment.
However, a tentative list of standard values is given in Annex 14B.
5.3 Rated insulation levels
5.3.1 General
Subclause 5.3.1 of IEC 61869-1:2007 is replaced by the following one:
The standard values of insulation level of IEC 60071-1 are not applicable to DC systems.
Methods of calculation for applied dielectric test voltages are given in the relevant clauses of
this document.
Additionally, indications for impulse withstand voltage values are given in Annex 14B.
5.3.3 Other requirements for primary terminals insulation
5.3.3.1 Partial discharges
Subclause 5.3.3.1 of IEC 61869-1:2007 is replaced by the following one:
The partial discharge level measured during the power-frequency voltage withstand test, shall
not exceed the limits specified in Table 3.
Table 3 – Partial discharge test voltages and permissible levels
Maximum permissible PD level
PD test voltage
pC
(r.m.s.)
Type of insulation
kV
immersed in liquid or gas solid
1,5 U /√2 10 50
m
1,2 U /√2 5 20
m
– 18 – IEC 61869-14:2018 © IEC 2018
5.4 Rated frequency
Subclause 5.4 of IEC 61869-1:2007 is replaced by the following one:
The rated frequency is equal to 0 (which means DC).
5.5 Rated output
5.5.602 Standard values for the rated delay time (t )
dr
Subclause 5.5.602 of IEC 61869-6:2016 is replaced by the following one:
The standard values for rated delay time are:
5 µs – 25 µs – 100 µs
5.5.1401 Standard values of rated secondary voltage
The standard values of rated secondary DC voltage are:
150 mV – 1,66 V – 3 V – 5 V
NOTE Generally, DC current transformers are multipurpose CTs.
5.6 Rated accuracy class
5.6.1401 Accuracy class designation
The accuracy class is designated by the highest permissible percentage of the ratio error at
rated primary current and with the rated burden.
5.6.1402 Standard accuracy classes
The standard accuracy classes are:
0,1 – 0,2 – 0,5 – 1
5.6.1403 Standard accuracy limit factors (K )
ALF
The standard values for K are:
ALF
3 – 6 – 10 – 20
5.6.1404 Limits of ratio error
5.6.1404.1 Ratio error for DC current measurement
This is applicable for DCCT intended to measure DC current at the DC side of the converter.
NOTE They are referred as CT2 in the introduction.
The ratio error for the DC component, measured at the secondary terminals at rated or higher
burden, shall not exceed the values given in Table 1403, expressed as a percentage of the
measured current. A graphical representation of error limits is shown in Figure 1405.
The accuracy shall be guaranteed for the whole range of temperature, both for the outdoor
and the indoor part of the current transformer and for both polarities.

Table 1403 – Limits of ratio error for
DCCT (classes from 0,1 to 1)
Ratio error
± %
Accuracy class
at % of rated current
5 20 100 K K
pcr ALF
0,1 1 0,25 0,1 0,1 1
0,2 2 0,5 0,2 0,2 2
0,5 3,5 1 0,5 0,5 5
1 5 2 1 1 10
For current lower than 5 % of the rated current, the absolute error ε shall not increase above
A
the value at 5 % of the rated current.
NOTE The purpose of this requirement is to consider a minimum value of error due to offset voltage and noise.

Figure 1405 – Accuracy limits of a DCCT
5.6.1404.2 Accuracy requirements for AC current measurement
These CT’s are exposed to DC voltage, but are intended to measure AC current
NOTE They are referred as CT3 in the introduction.
The error shall be specified in accordance with 5.6.201.3 or 5.6.202.2 of IEC 61869-2:2012,
or both. The reference rated frequency shall be defined.
NOTE Typically, the rated frequency refers to the AC network frequency.
5.6.1405 Accuracy requirements for harmonic measurement
This subclause is applicable for the measurement of the ripple of the DC current.

– 20 – IEC 61869-14:2018 © IEC 2018
Subclause 6A.4.3 of IEC 61869-6:2016 is applicable.
5.1401 Rated step response time
This subclause is not applicable to DCCT intended for AC current measurement.
The standard values for the rated step response time are:
25 µs – 250 µs – 500 µs
6 Design and construction
6.6 Requirements for the external insulation
6.6.1 Pollution
Subclause 6.6.1 of IEC 61869-1:2007 is replaced by the following.
This subclause is applicable to current transformers having U equal to or above 20 kV.
m
The purchaser shall specify the minimum creepage distance or the minimum USCD
(see IEC TS 60815-4:2016) or, alternatively, the DC site pollution severity.
The necessary creepage distance may be determined from the USCD by:
USCD × U
m
where USCD is the minimum nominal unified specific creepage distance (mm/kV), see
IEC 60050-471:2007, 471-01-16.
For indoor current transformers, the minimum USCD value shall be 14 mm/kV.
For outdoor current transformers, if artificial pollution tests are required, they shall be
performed in accordance with 7.4.1401.
NOTE Values for USCD for outdoor current transformers are considered in IEC TS 60815-4:2016. These values
are strongly dependent on the insulator material. Additional factors relating to the insulator profile and insulator
material are also specified.
6.7 Mechanical requirements
Subclause 6.7 of IEC 61869-1:2007 is replaced by the following one:
These requirements apply only to free-standing current transformers.
The required static load that current transformers shall be able to withstand is given
in Table 7. The figures include loads due to wind and ice.
The specified test loads are intended to be applied in any direction at the level of the primary
terminals.
Table 7 – Static withstand test loads
Static withstand test load, F
Highest voltage for
equipment, U
N
m
kV
Current transformers with terminals
Up to 100 2 500
> 100 up to 300 3 000
> 300 up to 500 4 000
> 500 5 000
NOTE 1 The sum of the loads acting in routine operating conditions should not exceed 50 % of the specified
withstand test load.
NOTE 2 Current transformers should withstand rarely occurring extreme dynamic loads (e.g. short circuits) not
exceeding 1,4 times the static withstand test load.
NOTE 3 For some applications, it may be necessary to establish the resistance to rotation of the primary
terminals. The moment to be applied during test is agreed between the manufacturer and the purchaser.

6.8 Multiple chopped impulse on primary terminals
Subclause 6.8 of IEC 61869-1:2007 is replaced by the following one:
If additionally specified, the primary terminals of oil-immersed current transformers having U
m
equal to or above 100 kV shall withstand multiple chopped impulses in accordance with 7.4.2
of IEC 61869-1:2007.
NOTE Requirements and tests relate to the behaviour of the internal shields and connections carrying high-
frequency transient currents. The test can also be applied to ratings below this level.
6.9 Internal arc fault protection requirements
Subclause 6.9 of IEC 61869-1:2007 is replaced by the following one:
These requirements apply to oil-immersed and gas-insulated free-standing current
transformers having U equal to or above 100 kV, for which an internal arc fault protection
m
class is additionally specified.
If additionally specified, the instrument transformer shall be able to withstand an internal arc
of the specified current and duration.
The applied current is a symmetrical sinusoidal current. The r.m.s. current value is
I /√2
SC
The arc fault duration shall be defined in accordance with Table 8.
It shall be considered that compliance with these requirements is achieved if the instrument
transformer passes the test described in 7.4.6 of IEC 61869-1:2007.

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Table 8 – Arc fault duration and performance criteria
Protection Arc fault Internal arc fault protection Internal arc fault protection
stage duration class I class II
s
1 0,2 Fracture of the housing and fire permitted, No external effect other than the operation
but all projected parts to be confined of suitable pressure relief device
within the containment area
2 0,5 No fragmentation (burn-through or fire
acceptable)
6.11 Electromagnetic compatibility (EMC)
6.11.2 Requirement for radio interference voltage (RIV)
Subclause 6.11.2 of IEC 61869-1:2007 is replaced by the following one:
The RIV requirement applies to current transformers having U equal to or above 100 kV to
m
be installed in air-insulated substations.
During test with power-frequency voltage, the radio interference voltage shall not exceed
2 500 µV at 1,1 × U / √2.
m
NOTE This requirement is included to meet certain electromagnetic compatibility regulations.
6.13 Markings
6.13.1401 Terminal markings
The markings shall identify
a) The primary and the secondary terminals;
b) The relative polarity of terminals.
6.13.1402 Method of marking
The primary terminals shall be marked clearly and indelibly, either on their surface or in their
immediate vicinity. If possible, the secondary terminals shall be identified clearly and
indelibly, either on the surface of the DCCT or in the immediate vicinity of the terminals.
6.13.1403 Terminal markings
The markings of DCCT terminals shall be as indicated in Table 1404:

Table 1404 – Markings of terminals

Primary terminals
Secondary terminals
DCCT with one secondary output

Primary terminals
Secondary terminals
DCCT with two secondary outputs

6.13.1404 Rating plate markings
Subclause 6.13 of IEC 61869-1:2007 and IEC 61869-6:2016 is replaced by the following one:
All current transformers shall carry at least the following markings:
a) manufacturer’s name or other mark by which the manufacturer can be readily identified;
b) year of manufacture and a serial number or a type designation, preferably both;
c) highest voltage for equipment (U );
m
d) insulation level;
e) rated primary current (I );
pr
f) rated continuous thermal current (I );
cth
g) long-time overload current (I ) (if specified);
lov
h) short time overload current (I ) (if specified);
sov
i) accuracy limit factor (K ) (if specified);
ALF
j) extended primary current factor (K );
pcr
k) accuracy class.
When the instrument transformer is intended for both DC and AC measurements, the
accuracy for both applications shall be marked separately.
l) temperature category;
m) mass in kg (when ≥ 25 kg);
n) thermal class of insulation if different from Class A;
If several classes of insulating material are used, the one which limits the temperature rise
shall be indicated.
In addition, the following information shall be marked (if applicable):
o) maximum static mechanical load;
p) type of insulating fluid;
q) rated filling pressure;
– 24 – IEC 61869-14:2018 © IEC 2018
r) minimum functional pressure;
s) insulating fluid volume (or mass) contained in the current transformer;
t) on transformers with secondary converters, the use of each one and its corresponding
terminals.
For analogue secondary output, the following information shall be marked:
u) rated secondary output voltage;
v) rated burden (R );
br
);
w) rated delay time (t
dr
x) on current transformers with two or more secondary terminals, the ratings of each one
(e.g. transformation ratio, accuracy class).
The rating plate of all DCCTs, where practicable, shall be readable from ground level and
carry the markings given in Tables 1405 to 1407.
Table 1405 – Rating plate marking for common rating plate
Rating Abbreviation Analogue output Digital output
Type designation x x
Manufacturer’s name or mark x x
Highest voltage for equipment U x x
m
Insulation level x x
Rated primary current I x x
pr
Rated continuous thermal current I x x
cth
Long-time overload current I x x
lov
Short time overload current I x x
sov
Accuracy limit factor K x x
ALF
Extended primary current factor K x x
pcr
Temperature category x x
Mass in kg x x
Thermal class of insulation x x
Maximum static mechanical load x x
Type of insulating fluid x x
Rated filling pressure x x
Minimum functional pressure
Insulating fluid volume (or mass) x x

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