IEC 61869-10:2017

IEC 61869-10 ®
Edition 1.0 2017-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Instrument transformers –
Part 10: Additional requirements for low-power passive current transformers

Transformateurs de mesure –
Partie 10: Exigences supplémentaires concernant les transformateurs de
courant passifs de faible puissance

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IEC 61869-10 ®
Edition 1.0 2017-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Instrument transformers –
Part 10: Additional requirements for low-power passive current transformers

Transformateurs de mesure –
Partie 10: Exigences supplémentaires concernant les transformateurs de

courant passifs de faible puissance

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20 ISBN 978-2-8322-5129-4

– 2 – IEC 61869-10:2017 © IEC 2017
CONTENTS
FOREWORD . 4
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 10
3.1 General definitions . 10
3.4 Definitions related to accuracy . 10
3.7 Index of abbreviations . 13
5 Ratings . 13
5.3 Rated insulation levels and voltages . 13
5.5 Rated output . 14
5.6 Rated accuracy class . 14
5.1001 Standard values for rated primary current (I ). 16
pr
5.1002 standard values for rated extended primary current factor (K ) . 16
pcr
5.1003 Standard value of rated continuous thermal current (I ) . 16
cth
5.1004 Standard values of rated secondary voltage (U ) . 17
sr
5.1005 Short-time current ratings . 17
5.1006 Rated phase offset (φ ) . 17
or
6 Design and construction . 17
6.11 Electromagnetic compatibility (EMC) . 17
6.13 Markings . 17
6.601 Requirements for optical transmitting system and optical output link . 19
6.602 Requirements for electrical transmitting system and electrical wires for
output link . 19
6.603 Signal-to-noise ratio . 19
6.604 Failure detection and maintenance announcement . 19
6.605 Operability . 19
6.606 Reliability and dependability . 19
6.607 Vibrations . 20
7 Tests . 20
7.1 General . 20
7.2 Type tests . 21
7.4 Special tests . 25
601 Information to be given with enquiries, tenders and orders . 25
601.1 Designation . 25
601.2 Dependability . 26
Annex 10A (informative) Designation of accuracy class when using the corrected
transformation ratio and ratio correction factor . 27
10A.1 General . 27
10A.2 Designation of accuracy class based on rated transformation ratio . 28
10A.3 Designation of accuracy class based on individual ratio correction factor . 28
10A.4 Example of application . 28
Annex 10B (informative) Principle of operation of Rogowski coils . 32
10B.1 General . 32
10B.2 Principle of operation . 32
10B.3 Designs . 33

10B.4 Accuracy . 33
10B.5 Frequency dependence and response . 35
Annex 10C (informative) Principle of operation of low-power iron core current
transformers (proportional LPCT) . 37
10C.1 General . 37
10C.2 Principle . 37
10C.3 Accuracy . 38
Annex 10D (normative) Test for accuracy with respect to the positioning of the primary
conductor . 39
10D.1 General . 39
10D.2 Designation of accuracy class extension . 39
10D.3 Test procedure . 40
Bibliography . 42

Figure 1001 – General block diagram of a single-phase low-power passive current
transformer . 8
Figure 1002 – Marking of terminals . 18
Figure 1003 – Test set up for impact of magnetic field from other phases . 24
Figure 10A.1 – Accuracy class designation improved based on individual ratio
correction factor CF . 28
I
Figure 10A.2 – Accuracy test of passive LPCT . 29
Figure 10A.3 – Accuracy class of 1 % designated based on rated transformation ratio . 30
Figure 10A.4 – Accuracy class of 0,1 % designated based on using the ratio correction
factor and corrected transformation ratio . 31
Figure 10B.1 – Rogowski coil Equivalent Circuits . 35
Figure 10B.2 – Integrated and non-integrated Rogowski coil output signals . 35
Figure 10B.3 – Rogowski coil frequency dependence test . 36
Figure 10C.1 – Principle of iron core current transformer . 37
Figure 10C.2 – Equivalent circuit of the iron core current transformer with voltage
output . 38
Figure 10D.1 – Definition of the angle between the primary conductor and the LPCT . 39
d = d . 40
min max
Figure 10D.2 – Illustration of the primary conductor position according to the position
factor . 40
Figure 10D.3 – Accuracy measurement test set up . 41

Table 1001 – Limits of ratio error and phase error for measuring passive LPCT . 15
Table 1002 – Limits of errors . 16
Table 1003 – Pin assignment for RJ45 connectors used in passive LPCT . 19
Table 10 – List of tests. 20
Table 1004 – Designation of a passive LPCT . 26
Table 10A.1 – Ratio, ratio error based on mean value, and corresponding primary
current . 29
Table 10A.2 – Measured ratio error, correction factor and ratio error based on ratio
correction factor for five passive LPCT . 30
Table 10D.1 – Limits for the position of the primary conductor with respect to the
passive LPCT . 39

– 4 – IEC 61869-10:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSTRUMENT TRANSFORMERS –
Part 10: Additional requirements
for low-power passive current transformers

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
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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 61869-10 has been prepared IEC technical committee 38:
Instrument transformers.
This first edition of IEC 61869-10, together with IEC 61869-1, IEC 61869-6, IEC 61869-8 and
IEC 61869-9, cancels and replaces the first edition of IEC 60044-8, published in 2002 . This
edition constitutes a technical revision.
The technical changes concern IEC TC 38's decision to restructure the whole set of stand-
alone standards in the IEC 60044 series and transform it into a new set of standards
composed of general requirements documents and specific requirements documents.
_____________
IEC 60044-8 will eventually be replaced by the IEC 61869 series, but until all the relevant parts of the
IEC 61869 series will be published, this standard is still in force.

The text of this International Standard is based on the following documents:
FDIS Report on voting
38/550/FDIS 38/551/RVD
Full information on the voting for the approval of this part of IEC 61869 can be found in the
report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
This standard is Part 10 of IEC 61869, published under the general title Instrument
transformers.
This Part 10 is to be read 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 edition of
these documents.
This Part 10 follows the structure of IEC 61869-1:2007 and IEC 61869-6:2016 and
supplements or modifies the corresponding clauses.
When a particular subclause of Part 1or part 6 is not mentioned in this Part 10, that subclause
applies. When this part of IEC 61869 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 1001 are
additional to those in Part 1 and Part 6;
– additional annexes are lettered 10A, 10B, 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 on the IEC
website.
– 6 – IEC 61869-10:2017 © IEC 2017
PRODUCT FAMILY STANDARDS PRODUCT PRODUCTS OLD
STANDARD STANDARD
IEC 61869-2 ADDITIONAL REQUIREMENTS FOR IEC 60044-1
CURRENT TRANSFORMERS
IEC 60044-6
IEC 61869-3 ADDITIONAL REQUIREMENTS FOR IEC 60044-2
INDUCTIVE VOLTAGE
TRANSFORMERS
IEC 61869-4 ADDITIONAL REQUIREMENTS FOR IEC 60044-3
COMBINED TRANSFORMERS
IEC 61869-5 ADDITIONAL REQUIREMENTS FOR IEC 60044-5
IEC 61869-1
CAPACITIVE VOLTAGE
GENERAL
TRANSFORMERS
REQUIREMENTS
IEC 61869-6 IEC 61869-7 ADDITIONAL REQUIREMENTS FOR IEC 60044-7
ELECTRONIC VOLTAGE
ADDITIONAL
TRANSFORMERS
GENERAL
REQUIREMENTS IEC 61869-8 SPECIFIC REQUIREMENTS FOR IEC 60044-8
FOR LOW-POWER
ELECTRONIC CURRENT
INSTRUMENT
TRANSFORMERS
TRANSFORMERS
IEC 61869-9 DIGITAL INTERFACE FOR
INSTRUMENT TRANSFORMERS
IEC 61869-10 ADDITIONAL REQUIREMENTS FOR
LOW-POWER PASSIVE CURRENT
TRANSFORMERS
IEC 61869-11 ADDITIONAL REQUIREMENTS FOR IEC 60044-7
LOW-POWER PASSIVE VOLTAGE
TRANSFORMERS
IEC 61869-12 ADDITIONAL REQUIREMENTS FOR
COMBINED ELECTRONIC
INSTRUMENT TRANSFORMER OR
COMBINED LOW-POWER PASSIVE
INSTRUMENT TRANSFORMERS
IEC 61869-13 STAND-ALONE MERGING UNIT
IEC 61869-14 ADDITIONAL REQUIREMENTS FOR
CURRENT TRANSFORMERS FOR DC
APPLICATIONS
IEC 61869-15 ADDITIONAL REQUIREMENTS FOR
VOLTAGE TRANSFORMERS FOR DC
APPLICATIONS
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
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.
– 8 – IEC 61869-10:2017 © IEC 2017
INTRODUCTION
Low-power passive current transformers (LPCT) are based on passive technologies without
any active electronic components. They can have an output signal proportional to the primary
current, for example iron core coils with integrated shunt as a current to voltage converter
(primary converter) or they can have an output signal proportional to the derivative of the
primary current, for example air-core coils (Rogowski coils). This part of IEC 61869 does not
cover the air-core coils with active integrator.
According to a general block diagram given in Figure 601 of IEC 61869-6:2016, the low-power
passive current transformers do not use an active primary converter (i.e. without any active
electronic component); therefore, there is no need for primary power supply. Additionally,
neither the secondary converter nor the secondary power supply is used.
The general block diagram of a low-power passive current transformer is given in
Figure 1001.
The applied technology decides which part is necessary for the realization of a low-power
passive current transformer, i.e. it is not absolutely necessary that the transmitting cable or
primary converter described in Figure 1001 be included in the low-power passive current
transformer. The derivative LPCT solution considers only the air-core coil as the primary
sensor and the transmission cable as the transmitting system. In this technology, the primary
converter is not considered. In case of a proportional LPCT solution, the ferromagnetic-core
coil is considered as the primary sensor, a burden resistance connected directly to the coil
outputs works as a primary converter and the transmission cable is a transmitting system.

P1 S1
Primary
Passive Transmitting
current sensor
primary converter cable
P2 S2
IEC
Figure 1001 – General block diagram of a single-phase low-power
passive current transformer
INSTRUMENT TRANSFORMERS –
Part 10: Additional requirements
for low-power passive current transformers

1 Scope
This part of IEC 61869 is a product standard and covers only additional requirements for low-
power passive current transformers. The product standard for low-power passive current
transformers comprises IEC 61869-1, together with IEC 61869-6 and this document with
specific requirements.
This document is applicable to newly manufactured low-power passive current transformers
with analogue output for use with electrical measuring instruments or electrical protective
devices having a rated frequency from 15 Hz to 100 Hz.
This document covers low-power passive current transformers used for measurement or
protection and multi-purpose low-power passive current transformers used for both
measurement and protection.
Subclause 5.6.1001 covers the accuracy requirements that are necessary for low-power
passive current transformers for use with electrical measuring instruments.
Subclause 5.6.1002 covers the accuracy requirements that are necessary for low-power
passive current transformers for use with electrical protective relays, and particularly for forms
of protection in which the prime requirement is to maintain the accuracy up to several times
the rated current. If required, the transient accuracy of low-power passive current
transformers during fault is also given in 5.6.1002.
Low-power passive current transformers have analogue voltage output only (for digital output
or for technology using any kind of active electronic components refer to IEC 61869-8 ). Such
low-power passive current transformers can include the secondary signal cable (transmitting
cable). The principle of operation of derivative low-power passive current transformers using
air-core coils (Rogowski coils) is given in Annex 10B and the principle of operation of
proportional low-power passive current transformers using iron-core coils with integrated
shunt is given in Annex 10C.
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:
IEC 60059, IEC standard current ratings
IEC 61869-6:2016, Instrument transformers – Part 6: Additional general requirements for low-
power instrument transformers
_____________
Under preparation.
– 10 – IEC 61869-10:2017 © IEC 2017
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61869-1 and
IEC 61869-6 apply with the following additions and modifications.
3.1 General definitions
3.1.613
transmitting system
Definition 3.1.613 of IEC 61869-6:2016 is applicable with the following addition:
Note 1001 to entry: For low-power passive current transformers the transmitting system is just a transmitting
cable.
3.1.621
output signal
Definition of 3.1.621 of IEC 61869-6:2016 is applicable with the following modification:
Note 1 to entry: In an electrical steady-state condition, the output signal is defined by the following formula:
u (t)= U 2 sin(2πft+ϕ )+ u (t)
s s s sres
where
u (t) is the output signal;
S
U is theRMS value of the secondary voltage, when u (t) = 0;
s Sres
f is the fundamental frequency;
φ is the secondary phase angle;
s
u (t) is the secondary residual voltage including harmonic, interharmonic and sub-harmonic components;
sres
t is the instantaneous value of the time;
f, U , φ being constant for steady-state condition.
s s
3.1.1001
derivative LPCT
low-power passive current transformer providing an output signal proportional to the derivate
of the input signal
Note 1 to entry: LPCT based on non-magnetic-core coil technology without a built-in integrator (e.g. Rogowski
coils) are derivate LPCT.
3.1.1002
proportional LPCT
low-power passive current transformer providing an output signal proportional to the input
signal
Note 1 to entry: LPCT based on iron-core technology with a built-in primary converter providing output voltage are
proportional LPTC.
3.4 Definitions related to accuracy
3.4.3
ratio error
ε
Definition 3.4.3 of IEC 61869-1:2007 and IEC 61869-6:2016 is applicable with the following
addition:
Note 1001 to entry: The ratio error, expressed in percent, is given by the formula:
K ⋅U − I
r s p
ε(%)= ×100
I
p
where
K is the rated transformation ratio;
r
I is the RMS value of the primary current;
p
U is the RMS value of the secondary voltage.
s
3.4.602
rated delay time
t
dr
not applicable
3.4.607
composite error
ε
c
Definition 3.4.607 of IEC 61869-6:2016 is applicable with the following addition:
Note 1001 to entry: The composite error ε , expressed in per cent, is given by the formula:
c
T
1 1
ε (%)= [K ⋅ u (t)− i (t)] dt×100

c r s p
∫
I T
p
where
K is the rated transformation ratio;
r
I is the RMS value of the primary current;
p
i (t) is the instantaneous primary current;
p
u (t) is the instantaneous secondary voltage;
s
T is the duration of one cycle;
t is the instantaneous value of the time.
3.4.1001
ratio correction factor
CF
I
factor by which the rated transformation ratio evaluated at rated burden and rated frequency
of an individual passive LPCT is to be multiplied to achieve the specified accuracy class
Note 1 to entry: Derivative LPCT is a frequency dependent device because its output linearly changes with
frequency. It can be used under different system frequencies without any change in its design and without loss of
accuracy. However, when the system frequency is different from the rated frequency, the correction factor is given
by using the following formula:
f
r
CF = CF ⋅
I I
f f
r
f
where
CF is the ratio correction factor at frequency f;
If
CF is the ratio correction factor at rated frequency f
Ifr r;
f is the rated system frequency of the passive LPCT;
r
f is the actual system frequency.
3.4.1002
corrected transformation ratio
K
cor
individual transformation ratio of a passive LPCT
Note 1 to entry: The relationship between the corrected transformation ratio and rated transformation ratio is:

K = CF⋅ K
cor I r
– 12 – IEC 61869-10:2017 © IEC 2017
3.4.1003
phase offset correction
ϕ
o cor
value added to the rated phase offset evaluated at the rated burden and rated frequency of an
individual passive LPCT to achieve the specified accuracy class
3.4.1004
corrected phase offset
φ
cor φo
individual phase offset of a passive LPCT
Note 1 to entry: The relationship between the corrected phase offset and phase offset correction is:
ϕ =ϕ +ϕ
corϕo ocor or
3.4.1005
corrected ratio error
ε
cor I
ratio error of an individual passive LPCT corrected by the factor defined in 3.4.1001
Note 1 to entry: The corrected ratio error is given by the formula:
CF⋅ K ⋅U − I
I r s p
ε (%)= ×100
corI
I
p
where
CF is the ratio correction factor of the individual passive LPCT.
I
3.4.1006
corrected composite error
ε
c cor I
composite error of an individual passive LPCT corrected by the factor defined in 3.4.1001
Note 1 to entry: The corrected composite error is given by the formula:
T
1 1
ε (%)= [CF⋅ K ⋅ u (t+dt)− i (t)] dt×100

ccorI I r s p
∫
I T
p
where
CF is the ratio correction factor of the individual passive LPCT;
I
is the time adjustment due to the corrected phase error.
dt=ϕ ⋅T 2π
ecor
3.4.1007
corrected phase error
φ
e cor
phase error of an individual passive LPCT corrected by the value defined in 3.4.1004
Note 1 to entry: The corrected phase error is given by the formula:
ϕ =ϕ −ϕ −ϕ
ecor s p corϕo
3.7 Index of abbreviations
Subclause 3.7 of IEC 61869-1:2007 is replaced by the following:
CF ratio correction factor
I
f rated frequency
r
I rated continuous thermal current
cth
I rated dynamic current
dyn
I rated extended primary current
epr
i primary current in transient condition
p(t)
I rated primary current
pr
I rated primary short-circuit current
psc
I rated short-time thermal current
th
K corrected transformation ratio
cor
K rated extended primary current factor
pcr
K rated transformation ratio
r
K rated symmetrical short-circuit factor
ssc
LPCT low- power current transformer
LPIT low-power instrument transformer
R rated burden
br
T specified primary time constant for transient performance
p
U highest voltage for equipment
m
U rated secondary voltage
sr
ε ratio error
ε composite error
c
ε corrected composite error
c cor I
ε corrected ratio error
cor I
ϕ corrected phase offset
cor φo
ϕ phase offset
o
ϕ phase offset correction
o cor
ϕ rated phase offset
or
ϕ corrected phase error
e cor
5 Ratings
5.3 Rated insulation levels and voltages
5.3.5 Insulation requirements for secondary terminals
Subclause 5.3.5 of IEC 61869-6:2016 is applicable.
5.3.601 Rated auxiliary power supply voltage (U )
ar
Not applicable.
– 14 – IEC 61869-10:2017 © IEC 2017
5.5 Rated output
5.5.601 Rated burden (R )
br
Subclause 5.5.601 of IEC 61869-6:2016 is applicable with the following addition:
The cable included in the LPCT shall not be changed/modified in order to preserve the
specified characteristics of the device.
5.5.602 Standard values for the rated delay time (t )
dr
Not applicable.
5.6 Rated accuracy class
5.6.1001 Accuracy based on rated transformation ratio and rated phase error
Ratio error ε or composite error ε is calculated by the formula in Note 1001 of definitions
c
3.4.3 and 3.4.607. No correction for individual deviations of the passive LPCT is done.
The phase error is calculated by the formula in Note 601 of definition 3.4.605 in IEC 61869-
6:2016. For passive LPCT only the rated phase offset φ is considered. Because rated delay
or
time for passive LPCT is not applicable, φ is zero.
tdr
5.6.1002 Accuracy based on individual corrected transformation ratio and corrected
phase offset
As an alternative to the accuracy based on rated transformation ratio and rated phase offset,
for passive LPCT the accuracy can be calculated based on the individual corrected
transformation ratio or individual ratio correction factor and the individual corrected phase
offset or individual phase offset correction factor. More information about the individual
correction is shown in Annex 10A.
Corrected ratio error ε or corrected composite error ε is calculated by the formula in
cor I c cor I
Note 1 of definitions 3.4.1005 and 3.4.1006. The correction factor CF shall be in the range
I
0,900 to 1,100 and specified with the suitable accuracy and number of decimals according to
the relevant accuracy class (with a minimal resolution of 0,001).
The corrected phase error is calculated by the formula in Note 1 of definition 3.4.1007. For
passive LPCT the individual corrected phase offset φ replaces the rated phase offset φ .
cor φo or
Because rated delay time for passive LPCT is not applicable, φ is zero. The phase offset
tdr
correction shall be in the range of ±300 min and specified with the suitable accuracy and
number of decimals according to the relevant accuracy class (with a minimal resolution of 1
min).
If the accuracy is based on the individual correction, the correction factors or the corrected
transformation ratio and the corrected phase offset shall be indicated on the rating plate.
5.6.1003 Measuring low-power passive current transformers
5.6.1003.1 Accuracy class designation for low-power passive current transformers
For measuring passive LPCT, the accuracy class is designated by the highest permissible
percentage of the ratio error (ε) at rated primary current and rated output.
5.6.1003.2 Standard accuracy classes
The standard accuracy classes for measuring passive LPCT are:
0,1 – 0,2 – 0,2S – 0,5 – 0,5S – 1 – 3

5.6.1003.3 Limits of current error and phase error for measuring passive LPCT
The current error and phase error at rated frequency and at rated or higher burden shall not
exceed the values given in Table 1001.
Table 1001 – Limits of ratio error and phase error
for measuring passive LPCT
Ratio error ε, ε ± phase error at primary current shown below
cor I
± %
Minutes Centiradians
Accuracy
class
at current at current at current
0,01 0,05 0,2I I K x 0,01 0,05 0,2I I K x 0,01 0,05 0,2I I K x
pr pr pcr pr pr pcr pr pr pcr
I I I I I I I I I
pr pr pr pr pr pr pr pr pr
0,1 - 0,4 0,2 0,1 0,1 - 15 8 5 5 - 0,45 0,24 0,15 0,15
0,2 - 0,75 0,35 0,2 0,2 - 30 15 10 10 - 0,9 0,45 0,3 0,3
0,2 S 0,75 0,35 0,2 0,2 0,2 30 15 10 10 10 0,9 0,45 0,3 0,3 0,3
0,5 - 1,5 0,75 0,5 0,5 - 90 45 30 30 - 2,7 1,35 0,9 0,9
0,5 S 1,5 0,75 0,5 0,5 0,5 90 45 30 30 30 2,7 1,35 0,9 0,9 0,9
1,0 - 3,0 1,5 1,0 1,0 - 180 90 60 60 - 5,4 2,7 1,8 1,8
3 - - 4,5 3 3 - - - - - - - - - -

More information and an explanatory diagram on the limits of accuracy and protection classes
are available in IEC 61869-6:2016, Annex 6E.
For passive LPCT without integrated primary conductor Annex 10D defines accuracy
designations regarding the position of the primary conductor.
5.6.1003.4 Accuracy requirements on harmonics
If there are requirements for harmonics, the accuracy requirements on harmonics, given in
IEC 61869-6:2016, Annex 6A, are applicable even though the improvement of the relevant
test procedures given there is under consideration by IEC TC 38.
5.6.1004 Protective low-power passive current transformers
5.6.1004.1 Rated accuracy limit primary current
The standard values for the rated accuracy limit primary currents shall be according to
IEC 60059. The preferred values are:
5 000 A – 10 000 A – 12 500 A – 25 000 A – 31 500 A – 40 000 A – 50 000 A – 63 000 A –
80 000 A
5.6.1004.2 Accuracy class designation
For protective passive LPCT, the accuracy class is designated by the highest permissible
percentage of the composite error, followed by the letter “P” (meaning protection) or by the
letters “TPE” (meaning transient protection electronic classes) and the rated accuracy limit
primary current.
NOTE See IEC 61869-6:2016, Annex 6B, for more explanations on TPE classes.
5.6.1004.3 Standard accuracy classes
The standard accuracy classes for protective passive LPCT are:
5P – 10P – 5TPE
– 16 – IEC 61869-10:2017 © IEC 2017
5.6.1004.4 Limits of current error and phase error for protective passive LPCT
At rated frequency and at a burden equal to or higher than the rated burden, the current ratio
error, phase error and composite error shall not exceed the values given in Table 1002.
For class TPE the maximum peak instantaneous error shall not exceed the values given in
Table 1002 during application of specified duty cycle. More information is given in IEC 61869-
6:2016, Annex 6B.
Table 1002 – Limits of errors
± Phase error at rated Maximum peak
± Ratio error at Composite error at
primary current instantaneous error at
rated primary rated accuracy limit
Accuracy
rated primary short
current primary current
class
circuit current I
psc
Minutes Centiradians
ε, ε in % ε , ε in %
cor I c cor I
%
5TPE 1 60 1,8 5 10
5P 1 60 1,8 5 -
10P 3 - - 10 -
NOTE Information on transient performance related to class TPE and other classes defined in IEC 61869-2 (PR, PX,
PXR, TPX, TPY and TPZ) are given in IEC 61869-6:2016, Annex 6B.

For passive LPCT without integrated primary conductor Annex 10D defines accuracy
designations regarding the position of the primary conductor.
5.6.1004.5 Accuracy requirements on harmonics
If there are requirements for harmonics, the accuracy requirements on harmonics, given in
IEC 61869-6:2016, Annex 6A, are applicable even though the improvement of the relevant
test procedures given there is under consideration by IEC TC 38.
5.1001 Standard values for rated primary current (I )
pr
The standard values of rated primary currents are:
25 A – 50 A – 80 A – 100 A
and their decimal multiples or fractions.
5.1002 standard values for rated extended primary current factor (K )
pcr
Because of the linear characteristics, the same passive LPCT can be used within a wide
range of primary current values. The standard values for the rated extended primary current
factor are:
5 – 10 – 20 – 50 – 100
NOTE Selection of proper primary and secondary rated values is done in line with input limits of the mea
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