IEC/IEEE 63253-5713-8:2024

IEC/IEEE 63253-5713-8 ®
Edition 1.0 2024-11
INTERNATIONAL
STANDARD
Station Service Voltage Transformers (SSVT)

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IEC/IEEE 63253-5713-8 ®
Edition 1.0 2024-11
INTERNATIONAL
STANDARD
Station Service Voltage Transformers (SSVT)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.220.20 ISBN 978-2-8322-8810-8

– 2 – IEC/IEEE 63253-5713-8:2024
© IEC/IEEE 2024
CONTENTS
FOREWORD . 7
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 11
3.1 General definitions . 11
3.2 Definitions related to voltage and dielectric aspects . 12
3.3 Definitions related to windings . 14
3.4 Definitions related to ratings . 15
3.5 Definitions related to losses . 16
3.6 Definitions related to gas insulation . 17
3.7 Index of abbreviated terms . 18
4 Profiles and use of normative references . 19
5 Environmental conditions . 19
5.1 Normal (usual) environmental conditions . 19
5.1.1 General . 19
5.1.2 Temperature . 19
5.1.3 Altitude . 19
5.1.4 Other environmental conditions . 19
5.1.5 Primary voltage . 20
5.1.6 Load current . 20
5.1.7 Step-down operation . 20
5.1.8 Operation above rated voltage or below rated frequency . 20
5.2 Special (unusual) environmental conditions . 21
5.2.1 General . 21
5.2.2 Special (unusual) temperature . 21
5.2.3 Altitude correction factor for altitudes greater than 1 000 m . 21
5.2.4 Loading beyond rated power . 22
5.2.5 Other special (unusual) environmental conditions . 22
6 Ratings . 23
6.1 Secondary voltage . 23
6.2 Cooling classes of SSVTs . 23
6.3 Frequency . 23
6.4 Rated power . 23
6.5 Voltage ratings and taps . 23
6.5.1 General . 23
6.5.2 Voltage ratings . 23
6.5.3 Ratings of SSVT taps . 24
6.5.4 Voltage drop or rise (voltage regulation) for a specified load condition . 24
6.6 Connections . 24
6.7 Markings . 24
6.7.1 Polarity of single-phase SSVTs . 24
6.7.2 Terminal markings . 24
6.7.3 Nameplates . 25
6.8 Turns ratio . 26
6.8.1 General . 26
6.8.2 Taps . 26

© IEC/IEEE 2024
6.9 Accuracy ratings of measurement windings . 26
6.9.1 General . 26
6.9.2 Assignment of accuracy class . 27
6.9.3 Accuracy classification for SSVT with two secondary measuring
windings or tapped secondary windings . 27
6.10 Short-circuit impedance . 27
6.11 Total losses . 27
6.12 Rated insulation levels of primary terminals . 27
6.12.1 Line terminal . 27
6.12.2 Creepage distance requirements . 29
6.12.3 Basic lightning impulse insulation level (BIL) . 29
6.12.4 Switching impulse insulation level (BSL) . 29
6.12.5 Neutral terminals . 29
6.13 Rated insulation levels of secondary terminals . 29
6.13.1 Secondary power windings terminals . 29
6.13.2 Secondary measuring windings terminals . 29
6.14 Insulation resistance requirements . 29
6.15 Earth shield requirements . 30
6.16 Dissolved gas and water content requirements for new mineral oil-immersed
SSVTs . 30
6.17 Internal arc requirements . 30
6.17.1 General . 30
6.17.2 Internal arc protection class I . 31
6.17.3 Internal arc protection class II . 31
6.18 Temperature rise and loading conditions for SSVT . 31
6.19 Partial discharge requirements . 32
6.20 RIV requirements . 32
7 Construction . 32
7.1 Tank pressure requirements for liquid-filled SSVTs . 32
7.2 Mechanical performance requirements . 32
7.2.1 Overview . 32
7.2.2 Sealing requirements tests . 33
7.2.3 Mechanical strength of the SSVT . 34
7.3 Liquid insulation system . 35
7.3.1 Insulating liquids . 35
7.3.2 Insulating liquid preservation . 35
7.4 Gas insulation system . 35
7.4.1 Requirements for gases in SSVTs . 35
7.4.2 Pressure monitoring devices . 36
7.4.3 Tank construction and maximum gas leakage rates . 36
7.5 Earthing . 36
7.5.1 SSVT tank earthing. 36
7.5.2 Earthing of core . 37
7.6 Degrees of protection by enclosures . 37
7.6.1 General . 37
7.6.2 Protection of persons against access to hazardous parts and protection
of the equipment against ingress of solid foreign objects . 37
7.6.3 Protection against ingress of water . 37
7.6.4 Protection of equipment against mechanical impact under normal
environmental conditions . 37

– 4 – IEC/IEEE 63253-5713-8:2024
© IEC/IEEE 2024
7.6.5 Tank or enclosure finish. 38
8 Short-circuit characteristics . 38
8.1 Short-circuit withsta
...