IEC 61869-1:2023

IEC 61869-1 ®
Edition 2.0 2023-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Instrument transformers –
Part 1: General requirements
Transformateurs de mesure –
Partie 1: Exigences générales
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IEC 61869-1 ®
Edition 2.0 2023-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Instrument transformers –
Part 1: General requirements
Transformateurs de mesure –
Partie 1: Exigences générales
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20  ISBN 978-2-8322-6940-4

– 2 – IEC 61869-1:2023 © IEC 2023
CONTENTS
FOREWORD . 9
INTRODUCTION . 12
1 Scope . 14
2 Normative references . 15
3 Terms, definitions, symbols and abbreviated terms . 18
3.1 Terms and definitions . 18
3.2 Symbols and abbreviated terms . 18
4 Normal and special environmental conditions . 19
4.1 General . 19
4.2 Normal environmental conditions . 20
4.2.1 Ambient air temperature . 20
4.2.2 Altitude . 20
4.2.3 Vibrations or earth tremors . 20
4.2.4 Exposure to pollution . 20
4.2.5 Other environmental conditions for indoor instrument transformers . 20
4.2.6 Other environmental conditions for outdoor instrument transformers . 21
4.2.7 IT with outdoor parts . 21
4.3 Special environmental conditions . 21
4.3.1 General . 21
4.3.2 Altitude . 21
4.3.3 Ambient temperature . 21
4.3.4 Vibrations or earth tremors . 22
4.3.5 Earthquakes . 22
5 Ratings . 22
5.1 General . 22
5.2 Voltage ratings . 22
5.2.1 Highest voltage for equipment (U ) . 22
m
5.2.2 Power system earthing . 25
5.2.3 Standard values for rated primary voltage (U ) . 25
pr
5.2.4 Standard values for rated secondary voltage (U ) . 25
sr
5.2.5 Rated auxiliary power supply voltage (U ) . 25
ar
5.3 Current ratings . 26
5.3.1 Standard values for rated primary current (I ) . 26
pr
5.3.2 Standard values for rated secondary current (I ) . 26
sr
5.3.3 Standard values for rated continuous thermal current (I ) . 26
cth
5.3.4 Short-time current ratings . 26
5.4 Dielectric ratings . 27
5.4.1 General . 27
5.4.2 Rated primary terminal insulation level . 27
5.4.3 Other requirements for primary terminal insulation . 27
5.4.4 Between-section insulation requirements . 29
5.4.5 Insulation requirements for secondary terminals and low-voltage
components . 29
5.5 Rated frequency (f ) . 30
r
5.6 Output ratings . 30

5.6.1 Rated output for inductive instrument transformers and CVTs . 30
5.6.2 Rated burden for LPITs . 30
5.6.3 Standard values for the rated delay time for EITs (t ) . 30
dr
5.7 Accuracy requirements . 30
5.7.1 General . 30
5.7.2 Rated accuracy classes . 31
5.7.3 Accuracy class extension for harmonics . 31
5.7.4 Accuracy requirements for harmonics . 31
5.7.5 Harmonic requirements for LPIT protection accuracy classes . 34
5.7.6 Anti-aliasing filter for EIT using digital data processing . 34
6 Design and construction . 36
6.1 Requirements for liquids used in equipment . 36
6.1.1 General . 36
6.1.2 Liquid quality . 36
6.1.3 Liquid level indicator . 37
6.1.4 Liquid tightness . 37
6.2 Requirements for gases used in equipment . 37
6.2.1 General . 37
6.2.2 Gas quality . 37
6.2.3 Gas monitoring device . 37
6.2.4 Gas tightness . 37
6.2.5 Pressure-relief device . 38
6.3 Requirements for solid materials used in equipment . 38
6.4 Requirements for temperature rise of parts and components . 38
6.4.1 General . 38
6.4.2 Influence of altitude on temperature rise . 40
6.5 Requirements for earthing of equipment . 41
6.5.1 General . 41
6.5.2 Earthing of the enclosure . 41
6.5.3 Electrical continuity. 41
6.6 Requirements for the external insulation . 41
6.6.1 Pollution . 41
6.6.2 Altitude . 42
6.7 Mechanical requirements . 43
6.8 Multiple chopped impulses on primary terminals . 44
6.9 Internal arc fault protection requirements . 45
6.10 Degrees of protection by enclosures . 45
6.10.1 General . 45
6.10.2 Protection against access to hazardous parts and protection of the

equipment against ingress of solid foreign objects and water . 45
6.10.3 Protection of enclosure against mechanical impact under normal
operating conditions . 46
6.11 Electromagnetic compatibility (EMC) . 46
6.11.1 General . 46
6.11.2 Requirements for immunity . 46
6.11.3 Requirements for emission . 50
6.11.4 Requirements for transmitted overvoltage (TOV) . 50
6.11.5 Requirements for radio interference voltage (RIV) . 50
6.12 Corrosion . 50

– 4 – IEC 61869-1:2023 © IEC 2023
6.13 Markings . 50
6.13.1 General . 50
6.13.2 Terminal markings . 51
6.13.3 Rating plate markings . 51
6.14 Requirements for LPIT secondary terminal connection . 52
6.14.1 Requirements for digital output connection . 52
6.14.2 Requirements for analogue output connections . 53
6.15 EIT secondary signal noise . 54
6.16 Fire hazard . 55
6.17 Pressure withstand of gas-filled enclosures . 55
6.18 Failure detection of EIT . 55
6.19 Operability . 55
6.20 Reliability and dependability of electronic part of EIT . 55
6.21 Vibration requirements . 56
6.22 Storage climatic conditions withstand capability . 56
7 Tests . 56
7.1 General . 56
7.1.1 Classification of tests . 56
7.1.2 List of tests . 57
7.1.3 Sequence of tests . 58
7.1.4 Testing conditions . 60
7.2 Type tests . 60
7.2.1 General . 60
7.2.2 Temperature rise test . 61
7.2.3 Impulse voltage withstand test on primary terminals . 62
7.2.4 Wet test for outdoor type instrument transformers. 65
7.2.5 Electromagnetic compatibility (EMC) tests . 66
7.2.6 Tests for accuracy . 71
7.2.7 Verification of the degree of protection by enclosures . 74
7.2.8 Enclosure tightness test at ambient temperature . 74
7.2.9 Proof test for the gas-filled enclosure . 74
7.2.10 Mechanical tests . 75
7.2.11 Voltage withstand test of low-voltage components and secondary

terminals . 76
7.2.12 Storage climatic environmental tests . 77
7.2.13 Vibration test . 79
7.2.14 Durability of markings . 80
7.2.15 Tests for accuracy for harmonics . 80
7.2.16 Test for anti-aliasing . 81
7.3 Routine tests. 81
7.3.1 Power-frequency voltage withstand test on primary terminals . 81
7.3.2 Partial discharge measurement . 82
7.3.3 Power-frequency voltage withstand tests between sections . 84
7.3.4 Power-frequency voltage withstand tests on secondary terminals . 85
7.3.5 Power-frequency voltage withstand test for low-voltage components . 85
7.3.6 Test for accuracy . 85
7.3.7 Verification of markings . 86
7.3.8 Enclosure tightness test at ambient temperature . 86
7.3.9 Pressure test for the gas-filled enclosure . 86

7.3.10 Measurement of capacitance and dielectric dissipation factor . 87
7.4 Special tests . 87
7.4.1 Multiple chopped impulse test on primary terminals . 87
7.4.2 Transmitted overvoltage test . 88
7.4.3 Internal arc fault test . 92
7.4.4 Enclosure tightness test at low and high temperatures . 93
7.4.5 Insulation resistance measurement on secondary terminals . 94
7.4.6 Corrosion test . 94
7.4.7 Fire hazard test . 94
7.4.8 Thermo-mechanical endurance test . 95
7.4.9 Vibration and shock tests . 95
7.4.10 Tests for accuracy versus harmonics . 98
7.4.11 Seismic qualification . 98
7.5 Commissioning tests . 98
7.5.1 General . 98
7.5.2 Final installation inspection and tests . 98
7.5.3 Gas dew point test . 99
7.6 Sample tests . 99
8 Rules for transport, storage, erection, operation and maintenance . 99
8.1 General . 99
8.2 Conditions during transport, storage and installation . 99
8.3 Installation . 99
8.3.1 General . 99
8.3.2 Unpacking and lifting . 99
8.3.3 Assembly . 100
8.3.4 Mounting . 100
8.3.5 Connections . 100
8.3.6 Final installation inspection and tests . 100
8.4 Operation . 101
8.5 Maintenance . 101
8.5.1 General . 101
8.5.2 Responsibilities for the manufacturer . 101
8.5.3 Responsibilities for the user. 101
8.6 Failure report . 102
9 Safety . 102
10 Influence of products on the natural environment . 102
Annex A (normative) Identification of test specimen . 103
A.1 General . 103
A.2 Data . 103
A.3 Drawings. 103
Annex B (informative) Recommendation for contents of failure reports . 104
B.1 General . 104
B.2 Content . 104
Annex C (informative) Fire hazard . 106
C.1 Fire hazard . 106
C.2 Fire hazard test . 106
Annex D (informative) Sample test . 107
D.1 Sample test definition . 107

– 6 – IEC 61869-1:2023 © IEC 2023
D.2 Sample tests . 107
Annex E (informative) Technique used in temperature rise test of transformers to
determine the thermal time constant by an experimental estimation . 108
Annex F (informative) Guidance for the extension of validity of type tests or special
tests of instrument transformers . 111
F.1 General . 111
F.2 Information needed for extension of type test validity . 111
F.3 Application of extension criteria . 112
F.3.1 Dielectric tests . 112
F.3.2 Temperature rise tests . 112
F.3.3 Short-time and dynamic withstand current tests (current transformers) . 113
F.3.4 Internal arc fault tests . 114
F.3.5 Multiple chopped impulse test . 114
Annex G (informative) Guidance for the calculation of equivalent diameter in case of
irregular shape of insulating part . 116
G.1 General . 116
G.2 Current transformers and earthed voltage transformers . 116
G.3 Unearthed voltage transformers . 117
Annex H (informative) Test circuits . 119
H.1 Test circuits for accuracy measurements in steady state for current
transformers with analogue secondary signal . 119
H.2 Test circuits for accuracy measurements in steady state for voltage
transformers with analogue secondary signal . 123
Annex I (normative) Seismic qualification of instrument transformers . 127
I.1 Scope . 127
I.2 Seismic conditions . 127
I.2.1 Time-history . 127
I.2.2 Seismic severity of application . 127
I.2.3 Superelevation factor (k ) . 129
se
I.3 Seismic qualification information . 129
I.3.1 Qualification options . 129
I.3.2 General information provided by purchaser . 129
I.4 Qualification procedure . 129
I.4.1 General . 129
I.4.2 Qualification by static calculation or dynamic analysis . 130
I.4.3 Qualification by test . 137
I.5 Validity of qualification . 139
Bibliography . 140

Figure 1 – General block diagram of single-phase LPITs . 14
Figure 2 – Example of digital data acquisition system . 34
Figure 3 – Example of frequency response mask for EIT with digital output . 36
Figure 4 – Altitude correction factor for the temperature rise . 40
Figure 5 – Factor m for the switching impulse voltage (U ) withstand test . 43
SIL
Figure 6 – Example structure used in HV AIS applications subjected to EMC tests . 48
Figure 7 – Example of structure used in HV GIS applications subjected to EMC tests . 49
Figure 8 – Duplex LC connector . 53
Figure 9 – RIV measuring circuit . 66

Figure 10 – Temperature cycle accuracy test . 73
Figure 11 – Test circuit for partial discharge measurement . 82
Figure 12 – Alternative circuit for partial discharge measurement . 83
Figure 13 – Example of balanced test circuit for partial discharge measurement . 83
Figure 14 – Voltage profile for partial discharge measurement . 84
Figure 15 – Transmitted overvoltage measurement: test impulse waveforms . 89
Figure 16 – Transmitted overvoltage measurement: primary test configuration for AIS
equipment . 90
Figure 17 – Transmitted overvoltage measurement: primary test configuration for GISs

(CTs and VTs) . 90
Figure 18 – Transmitted overvoltage measurement: example of correct secondary test
connection for CT and VT . 91
Figure 19 – Typical configuration for internal arc fault test . 92
Figure E.1 – Graphical extrapolation to ultimate temperature rise . 110
Figure G.1 – Shed dimensions . 116
Figure G.2 – Examples of MV CTs and earthed VTs . 117
Figure G.3 – Example of a CT with multiple insulator areas . 117
Figure G.4 – Examples of unearthed VTs . 118
Figure G.5 – Example of a VT with multiple insulator areas . 118
Figure H.1 – Test circuit for accuracy measurements of inductive CTs . 119
Figure H.2 – Test circuit for analogue accuracy measurements of LPCTs . 120
Figure H.3 – Test circuit for analogue accuracy measurements of LPCTs (alternative
solution) . 121
Figure H.4 – Test circuit for digital accuracy measurements of LPCTs . 122
Figure H.5 – Test circuit for accuracy measurements of inductive VTs or CVTs . 123
Figure H.6 – Test circuit for analogue accuracy measurements of LPVTs . 124
Figure H.7 – Test circuit for analogue accuracy measurements of LPVTs (alternative

solution) . 125
Figure H.8 – Test circuit for digital accuracy measurements of LPVTs . 126
Figure I.1 – Record of time-history in real (3 dimensional) . 127
Figure I.2 – Required response spectrum . 128
Figure I.3 – Flowchart of qualification procedure . 130
Figure I.4 – Measured deflection in free oscillation . 132
Figure I.5 – Sketch of the parameters in static calculation . 134

Table 1 – Operating ambient temperature categories . 20
Table 2 – Rated primary terminal insulation levels for instrument transformers for AC
applications . 24
Table 3 – Insulation requirements for power supply terminals . 26
Table 4 – Partial discharge test voltages and permissible levels for AC applications . 28
Table 5 – Maximum values of tanδ . 29
Table 6 – LPIT secondary terminal and low-voltage component terminal withstand
capability . 29
Table 7 – WB0 extension for harmonics . 32
Table 8 – Accuracy class extensions for wide bandwidth applications . 33

– 8 – IEC 61869-1:2023 © IEC 2023
Table 9 – Harmonic requirements for protection accuracy classes . 34
Table 10 – Anti-aliasing filter requirements . 35
Table 11 – Permissible temporary leakage rates for gas systems . 38
Table 12 – Limits of temperature and temperature rise for various parts, materials and
dielectrics of instrument transformers . 39
Table 13 – Specific creepage distances by site pollution severity class, as defined in
the former publication . 42
Table 14 – Maximum static withstand loads . 44
Table 15 – Maximum gas-in-oil level in instrument transformers . 44
Table 16 – Arc fault duration and performance criteria . 45
Table 17 – Immunity requirements and test levels . 47
Table 18 – Acceptance criteria for EMC immunity tests . 49
Table 19 – Connectors . 54
Table 20 – List of tests. 57
Table 21 – Gas type and pressure during tests . 58
Table 22 – Required routine tests . 59
Table 23 – Modalities of application of the test loads to be applied to the primary
terminals . 76
Table 24 – Dry heat test, storage temperature . 78
Table 25 – Cold test, storage temperature . 78
Table 26 – Damp heat steady state test . 79
Table 27 – Transmitted overvoltage limits . 89
Table 28 – Shock severity levels . 97
Table A.1 – Example of drawing to be submitted . 103
Table C.1 – Fire hazard of electrotechnical products . 106
Table F.1 – Extension criteria for dielectric withstand performance . 112
Table F.2 – Extension criteria for temperature rise performance . 113
Table F.3 – Extension criteria for short-time and dynamic withstand current
performance . 113
Table F.4 – Extension criteria for internal arc fault tests . 114
Table F.5 – Extension criteria for multiple chopped impulse test . 115
Table I.1 – Seismic severity levels . 128
Table I.2 – External mass to simulate external forces . 137
Table I.3 – Comparable seismic levels . 139

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSTRUMENT TRANSFORMERS –
Part 1: General requirements
FOREWORD
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