INTERNATIONAL STANDARD
NORMEINTERNATIONALE
PowertransformersPart 3:Insulation levels dielectric tests and external clearances in air
Transformateursdepuissance-Partie3:Niveauxd’isolement essaisdielectriques et distances d'isolementdansI'air
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INTERNATIONAL STANDARD
NORMEINTERNATIONALE
PowertransformersPart 3:Insulation levels dielectric tests and external clearances in air
Transformateurs depuissance-Partie 3:Niveaux d'isolement essais dielectriques etdistances d'isolementdans l'air
ELECTROTECHNICAL INTERNATIONALCOMMISSION
COMMISSIONELECTROTECHNIQUEINTERNATIONALE
CONTENTS
FOREWORD. 4INTRODUCTION. 62 1 Scope Normative references. .73 Terms and definitions .74 General. 8"5 Highest voltage for equipment and rated insulation level. .106 Transformers with re-connectable windings. Dielectric tests. .11 .127 7.1 Overview ..127.2 Test requirements. .137.2.1 7.2.2 Test voltage levels. General ...4. .137.2.3 Test sequence. 177.3 Test requirements for specific transformers 177.3.2 7.3.1 Tests on transformers with 72 5 kV 170 kV. .197.4 Assigning Um and test voltages to the neutral terminal of a winding .207.4.1 Transformers with Um > 72 5 kV. Transformers with Um ≤ 72 5 kV . .208 Dielectric tests on transformers that have been in service ... 7.4.2 ...0 209 Insulation of auxiliary wiring (AuxW). .2110 Applied voltage test (AV)... ..2111 Induced voltage tests (IVW and IVPD) .2211.1 General. 11.2 Induced voltage withstand test (IVW) .22 2211.3 Induced voltage test with partial discharge measurement (IVPD)) 2311.3.1 General 11.3.2 Test duration and frequency. .23 .2311.3.3 Test sequence. 2311.3.4 Partial discharge (PD) measurement. 2412 Line terminal AC withstand test (LTAC).. 11.3.5 Test acceptance criteria .25 .2513 Lightning impulse tests (LI LIC LIN LIMT).. ..2613.1 Requirements for all lightning impulse tests 2613.1.2 Tap positions.. 13.1.1 General .26 .2613.1.3 Records of tests. ...2613.1.4 Test connections. .28 2713.2 Full wave lightning impulse test (Ll) 13.2.1 Wave shape determination of test voltage value and tolerances . .2813.2.2 Tests on transformers without non-linear elements. 2913.3 Chopped wave lightning impulse test (LIC). 13.2.3 Tests on transformers with non-linear elements. .30 31
13.3.1 Wave shape.. 31 3113.3.2 Tests on transformers without non-linear elements. 13.3.3 Tests on transformers with non-linear elements... ..3213.4 Lightning impulse test on a neutral terminal (LIN)..13.4.1 General. 13.4.2 Waveshape...13.4.3 Test sequence.... .3413.4.4 Test criteria ..3414 Switching impulse test (Sl).. 14.1 General .34 .3414.2 Test connections ..414.3 Waveshape 14.4 Test sequence... ..35 .3514.5 Test criteria 3515 Action following test failure .3616 External clearances in air.. .3616.1 General 16.2 Clearance requirements. ...36 ..37Annex A (informative) Application guide for partial discharge measurements onAnnex B (informative) Overvoltage transferred from the high-voltage winding to a low- transformers.... ..40voltage winding.... ...45Annex C (informative) Information on transformer insulation and dielectric tests to be supplied with an enquiry and with an order .... .47Annex D (informative) Neutral insulation voltage level calculation .. ...50Annex E (informative) Basis for dielectric tests insulation levels and clearances 53Bibliography.. ..56
Table 1 - Requirements and tests for different categories of windings. ..14Table 2 - Test voltage levels (1 of 2) . ..15Table 3 - Test voltage levels used in special cases 16Table 4 Minimum clearances in air (1 of 2)
