AS 1675-1986

1 - AS 1675-1986 CURRENT TRANSFORMERS - MEASUREMENT AND PROTECTION
4 - PREFACE
5 - CONTENTS
7 - SECTION 1. SCOPE AND GENERAL REQUIREMENTS
7 - 1.1 SCOPE.
7 - 1.2 APPLICATION.
7 - 1.3 REFERENCED DOCUMENTS.
7 - 1.4 DEFINITIONS.
7 - 1.4.1 General.
7 - 1.4.2 Definitions relating to construction.
9 - 1.4.3 Definitions relating to performance.
10 - 1.4.4 Definitions relating to service conditions of a three-phase system.
10 - 1.5 SERVICE CONDITIONS
10 - 1.6 RATED FREQUENCY.
11 - 1.7 RATED INSULATION LEVEL (RIL)
11 - 1.7.1 Selection.
11 - 1.7.2 Method of expression.
11 - 1.8 RATED CURRENTS.
11 - 1.8.1 Rated primary current.
11 - 1.8.2 Rated secondary current.
11 - 1.8.3 Thermal limit current.
11 - 1.8.4 Rated short-time current.
11 - 1.9 RATED SHORT-TIME
12 - 1.10 TEMPERATURE RISE
12 - 1.10.1 General.
12 - 1.10.2 Temperature rise of windings.
12 - 1.10.3 Temperature rise of oil.
12 - 1.10.4 Temperature rise of core or other metallic parts
12 - 1.11 SHORT-TIME CURRENT WITHSTAND
12 - 1.12 TERMINAL MARKINGS.
12 - 1.12.1 General.
12 - 1.12.2 Marking principles.
13 - 1.12.3 Series-parallel connections.
13 - 1.12.4 Test-Tap terminals
14 - 1.13 ROUTINE TESTS.
14 - 1.13.1 General.
14 - 1.13.2 Verification of terminal markings.
14 - 1.13.3 Arrangement of the CT for voltage withstand tests
14 - 1.13.4 High voltage testing techniques.
14 - 1.13.5 Voltage withstand: secondary winding(s) to earth
14 - 1.13.6 Voltage withstand: between primary windings or between sections of a primary windings
14 - 1.13.7 Voltage withstand: primary winding(s) to earth
14 - 1.13. 8 Voltage withstand: between turns of the secondary winding.
15 - 1.13.9 Subsequent dielectric tests.
15 - 1.13.10 Partial discharge test.
15 - 1.13.11 Measurement of dielectric dissipation factor (tangent delta) of a CT having capacitively-graded insulation
15 - 1.14 TYPE TESTS.
15 - 1.14.1 General.
15 - 1.14.2 High-voltage power-frequency wet withstand test on outdoor CTs
16 - 1.14.3 Impulse-voltage withstand test on primary insulation
16 - 1.14.4 Temperature rise test.
16 - 1.14.5 Short-time current withstand test.
17 - 1.15 SPECIAL TYPE TESTS.
17 - 1.15.1 Radio influence voltage (RIV) test.
17 - 1.15.2 Thermal stability test.
17 - 1.16 COMMISSIONING TESTS.
17 - 1.17 RATING PLATE MARKINGS.
18 - SECTION 2. SPECIFIC REQUIREMENTS FOR MEASUREMENT CURRENT TRANSFORMERS
18 - 2.1 SCOPE OF SECTION.
18 - 2.2 APPLICATION.
18 - 2.3 CLASSIFICATION OF MEASUREMENT CTs
18 - 2.4 CLASS M CTs.
18 - 2.4.1 Designation.
18 - 2.4.2 Accuracy classification.
18 - 2.4.3 Current errors and phase errors.
18 - 2.5 CLASS ME CTs.
18 - 2.5.1 Designation.
18 - 2.5.2 Accuracy classification.
18 - 2.5.3 Rated accuracy limit factor.
18 - 2.5.4 Current errors and phase errors.
18 - 2.6 EFFECTIVE DEMAGNETIZATION.
20 - 2.7 RATED BURDENS AND RATED OUTPUTS.
20 - 2.8 DETERMINATION OF ERRORS.
20 - 2.8.1 Type tests.
20 - 2.8.2 Routine tests.
20 - 2.9 RATING PLATE MARKINGS.
20 - 2.9.1 Location.
20 - 2.9.2 Information to be marked.
21 - SECTION 3. SPECIFIC REQUIREMENTS FOR PROTECTION CURRENT TRANSFORMERS
21 - 3.1 SCOPE OF SECTION.
21 - 3.2 APPLICATION.
21 - 3.3 CLASSIFICATION OF PROTECTION CTs.
21 - 3.4 CLASS P CTs.
21 - 3.4.1 Designation.
21 - 3.4.2 Rated composite error.
21 - 3.4.3 Rated secondary reference voltage.
21 - 3.4.4 Rated accuracy limit factor.
21 - 3.4.5 Composite error (see Appendix J).
21 - 3.4.6 Current error.
22 - 3.5 CLASS PL CTs.
22 - 3.5.1 Designation.
22 - 3.5.2 Alternative method of specification.
22 - 3.5.3 Turns ratio
22 - 3.5.4 Ratio of the composite error measured indirectly to the composite error measured directly
22 - 3.5.5 Knee-point voltage
22 - 3.5.6 Secondary exciting current.
22 - 3.5.7 Secondary winding resistance.
23 - 3.6 CLASS PS CTs.
23 - 3.6.1 Designation.
23 - 3.6.2 Specification.
23 - 3.7 DETERMINATION OF COMPLIANCE WITH THIS SECTION
23 - 3.8 RATING PLATE MARKINGS.
23 - 3.8.1 Location.
23 - 3.8.2 Information to be marked.
24 - APPENDIX A - INFORMATION TO BE SUPPLIED WITH ENQUIRY AND ORDER
25 - APPENDIX B - GUIDANCE IN THE APPLICATION OF CURRENT TRANSFORMERS
25 - B1 MEASUREMENT CURRENT TRANSFORMERS.
25 - B1.1 Rated burden.
25 - B1.2 Accuracy class.
25 - B2 PROTECTION CURRENT TRANSFORMERS.
25 - B2.1 General.
25 - B2.2 Rated transformation ratio.
26 - B2.3 Transient performance, transient factor and maximum operating level.
27 - B2.4 Classification of current transformers.
27 - B2.5 Correlation of transformer class, maximum operating level, and categories of protection.
29 - B3 DUAL-PURPOSE CURRENT TRANSFORMERS
29 - B4 ELECTROSTATICALLY-SCREENED CURRENT TRANSFORMERS.
29 - B4.1 General.
29 - B4.2 Electrostatic effects.
30 - B5 ELECTROMAGNETICALLY- SHIELDED CURRENT TRANSFORMERS
30 - B5.1 General.
30 - B5.2 Electromagnetic effects.
31 - B6 MULTIPLE-RATIO CURRENT TRANSFORMERS.
31 - B7 OPEN-CIRCUIT SECONDARY.
33 - APPENDIX C - SERVICE CONDITIONS
33 - C1 AMBIENT TEMPERATURE.
33 - C2 LOCAL ATMOSPHERIC AND CLIMATIC CONDITIONS.
34 - APPENDIX D - SHORT-TIME CURRENT RATING OF CURRENT TRANSFORMERS
37 - APPENDIX E - TEMPERATURE MEASUREMENTS
37 - E1 INTRODUCTION.
37 - E2 RECOGNIZED METHODS OF MEASURING TEMPERATURE.
37 - E3 THERMOMETER METHOD.
37 - E4 THERMOCOUPLE METHOD.
37 - E5 SELF-RESISTANCE METHOD.
38 - E6 MEASUREMENT OF TEST CONNECTIONS.
39 - APPENDIX F - CURRENT TRANSFORMER TEST TAPS
40 - APPENDIX G - METHOD OF TEST FOR RADIO INFLUENCE VOLTAGE (RIV)
40 - G1 ARRANGEMENT.
40 - G2 TEST EQUIPMENT.
40 - G3 TEST PROCEDURE.
42 - APPENDIX H - EQUIVALENCE OF IEC CLASS P CTs AND AUSTRALIAN CLASS P CTs
44 - APPENDIX J - COMPOSITE ERROR
44 - J1 GENERAL.
44 - J2 EFFECT OF NON-LINEAR IMPEDANCE
45 - J3 ELECTROMAGNETIC COUPLING AND FLUX LEAKAGE.
45 - J4 INSULATION LEAKAGE CURRENTS.
45 - J5 INDIRECT MEASUREMENT OF COMPOSITE ERROR.
45 - J5.1 General.
45 - J5.2 Measurement at accuracy limit current.
46 - J6 DIRECT MEASUREMENT OF COMPOSITE ERROR.
46 - J6.1 General.
46 - J6.2 Alternative method of test.
48 - J7 TEST PRECAUTIONS.
49 - APPENDIX K - DETERMINATION OF TURNS RATIO
49 - K1 GENERAL.
49 - K2 FACTORS 1 AND 2.
50 - K3 FACTOR 3.
50 - K4 FACTOR 4.
50 - K5 NOTATION.
51 - APPENDIX L - NOTATION
52 - ANNEX - LIST OF REFERENCED DOCUMENTS
53 - INDEX

Specifies requirements for the designation, rating, performance, marking, and testing of current transformers (CTs). Covers aspects common to all CTs (Section 1) and specific requirements for Class M and Class ME measurement CTs (Section 2) and for Class P, Class PL, and Class PS protection CTs (Section 3). Provides extensive explanatory material in appendices.

This standard specifies requirements for current transformers (herein referred to as CTs) for use with electrical measuring instruments and electrical protection devices.NOTE: Such instruments and devices are covered by the following standards: AS 1024, AS 1042, AS 1284, AS 1384 and AS 2481.The standard also applies to CTs suitable for operating measuring relays and circuit-breaker trip coils, and to standard CTs used in the testing of CTs.NOTES:1. In order to facilitate the specification and purchase of CTs, the standard also lists information which should be supplied with enquiry and order (see Appendix A).2. Particular attention is drawn to the Foreword to AS 1384 concerning possible peculiarities in the burdens imposed on CTs by certain transducers.3. Guidance in the application of CTs is given in Appendix B.