1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA
2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any
3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-22436-3 SANS 780:2009 Edition 4SOUTH AFRICAN NATIONAL STANDARD Distribution transformers WARNING Can only be used in conjunction with SANS
4、 60076-1 Published by SABS Standards Division 1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001 Tel: +27 12 428 7911 Fax: +27 12 344 1568 www.sabs.co.za SABS This standard may only be used and printed by approved subscription and freemailing clients of the SABS.SANS 780:2009 Edition 4 Tabl
5、e of changes Change No. Date Scope Foreword This South African standard was approved by National Committee SABS SC 67E, Electricity distribution systems and components Electricity distribution, in accordance with procedures of the SABS Standards Division, in compliance with annex 3 of the WTO/TBT ag
6、reement. This document was published in April 2009. This document supersedes SANS 780:2004 (edition 3.2). Annex C forms an integral part of this document. Annexes A, B and D are for information only. This standard may only be used and printed by approved subscription and freemailing clients of the S
7、ABS.SANS 780:2009 Edition 4 1 Contents Page Foreword 1 Scope. 3 2 Normative references. 3 3 Definitions and abbreviations. 5 4 Rating. 5 5 Requirements for transformers that have a tapped winding 6 6 Connection and phase displacement symbols for three-phase transformers 8 7 Rating plates 8 8 Miscell
8、aneous requirements 8 9 Tolerances. 19 10 Tests 20 11 Marking 23 Tables 1-9 24-29 Figures 1-6. 29-33 Annex A (informative) Guide to purchasers on preparing an enquiry 34 Annex B (informative) Recommendations with regard to responsibility for testing 40 Annex C (normative) Non-preferred fittings . 41
9、 Annex D (informative) Example of a Routine Test Report. 45 Bibliography . 46 This standard may only be used and printed by approved subscription and freemailing clients of the SABS.SANS 780:2009 Edition 4 2 This page is intentionally left blankThis standard may only be used and printed by approved
10、subscription and freemailing clients of the SABS.SANS 780:2009 Edition 4 3 Distribution transformers 1 Scope 1.1 This standard specifies requirements for single-phase and three-phase distribution transformers of the oil-immersed type, that a) are category-sized in accordance with SANS 60076-1 up to
11、and including 3 150 kVA, b) have rated maximum voltages (U m ) that do not exceed 36 kV, c) have uniformly insulated windings, d) have a high-voltage and a low-voltage winding or, in the case of an auto-transformer, a series and a common winding and, in each case, if necessary, a stabilizing winding
12、 or an auxiliary winding, and e) are suitable for off-circuit tap changing only. NOTE Although distribution transformers are generally designed to receive power at a voltage that exceeds 3,3 kV and to deliver power to systems that have a nominal voltage of 230/400 V or 525 V, this standard covers tr
13、ansformers that have any combination of rated primary and secondary voltages. 1.2 This standard is not applicable to transformers that have more than two windings, other than those referred to in 1.1(d). 1.3 This standard applies to distribution transformers that are designed for use, at full contin
14、uous rating, under the conditions specified in SANS 60076-1, and also under the following conditions: a) at an altitude that does not exceed 1 800 m; b) at a system voltage frequency of 50 Hz; and c) under the conditions to which the electrical installations being served could be exposed. NOTE Requi
15、rements that have to be specified by the purchaser and those that have to be agreed upon by the manufacturer and the purchaser are listed in annex A. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the editi
16、on cited applies. For undated references, the latest edition of the referenced documents (including any amendments) applies. Information on currently valid national and international standards can be obtained from the SABS Standards Division. IEC 60085, Electrical insulation Thermal evaluation and d
17、esignation. This standard may only be used and printed by approved subscription and freemailing clients of the SABS.SANS 780:2009 Edition 4 4 ISO 8501-1, Preparation of steel substrates before application of paints and related products Visual assessment of surface cleanliness Part 1: Rust grades and
18、 preparation grades of uncoated steel substrates and of steel substrates after overall removal of previous coatings. NRS 012, Cable terminations and live conductors within air-insulated enclosures (insulation co- ordination) for rated a.c. voltages of 7,2 kV and up to and including 36 kV. SANS 32/EN
19、 10240, Internal and/or external protective coatings for steel tubes Specification for hot dip galvanized coatings applied in automatic plants. SANS 121/ISO 1461, Hot dip galvanized coatings on fabricated iron and steel articles Specifications and test methods. SANS 555, Unused and reclaimed mineral
20、 insulating oils for transformers and switchgear. SANS 1029, Miniature substations. SANS 1037, Standard transformer bushings. SANS 1091, National colour standard. SANS 1507-1, Electric cables with extruded solid dielectric insulation for fixed installations (300/500 V to 1 900/3 300 V) Part 1: Gener
21、al. SANS 1507-2, Electric cables with extruded solid dielectric insulation for fixed installations (300/500 V to 1 900/3 300 V) Part 2: Wiring cables. SANS 1507-3, Electric cables with extruded solid dielectric insulation for fixed installations (300/500 V to 1 900/3 300 V) Part 3: PVC distribution
22、cables. SANS 1507-4, Electric cables with extruded solid dielectric insulation for fixed installations (300/500 V to 1 900/3 300 V) Part 4: XLPE distribution cables. SANS 1507-5, Electric cables with extruded solid dielectric insulation for fixed installations (300/500 V to 1 900/3 300 V) Part 5: Ha
23、logen-free distribution cables. SANS 1507-6, Electric cables with extruded solid dielectric insulation for fixed installations (300/500 V to 1 900/3 300 V) Part 6: Service cables. SANS 2063/ISO 2063, Thermal spraying Metallic and other inorganic coatings Zinc, aluminium and their alloys. SANS 2808/I
24、SO 2808, Paints and varnishes Determination of film thickness. SANS 10064, The preparation of steel surfaces for coating. SANS 60076-1:2008/IEC 60076-1:2000, Power transformers Part 1: General. SANS 60076-2/IEC 60076-2, Power transformers Part 2: Temperature rise. SANS 60076-3/IEC 60076-3, Power tra
25、nsformers Part 3: Insulation levels, dielectric tests and external clearances in air. SANS 60076-5:2006/IEC 60076-5:2006, Power transformers Part 5: Ability to withstand short circuit. This standard may only be used and printed by approved subscription and freemailing clients of the SABS.SANS 780:20
26、09 Edition 4 5 SANS 60076-7/IEC 60076-7, Power transformers Part 7: Loading guide for oil-immersed power transformers. SANS 60076-10/IEC 60076-10, Power transformers Part 10: Determination of sound levels. SANS 60076-13/IEC 60076-13, Power transformers Part 13: Self-protected liquid-filled transform
27、ers. SANS 60137/IEC 60137, Insulated bushings for alternating voltages above 1 000 V. SANS 60815-1/IEC/TS 60815-1, Selection and dimensioning of high-voltage insulators intended for use in polluted conditions Part 1: Definitions, information and general principles. SANS 60815-2/IEC/TS 60815-2, Selec
28、tion and dimensioning of high-voltage insulators intended for use in polluted conditions Part 2: Ceramic and glass insulators for a.c. systems. SANS 60815-3/IEC/TS 60815-3, Selection and dimensioning of high-voltage insulators intended for use in polluted conditions Part 3: Polymer insulators for a.
29、c. systems. 3 Definitions and abbreviations 3.1 Definitions For the purposes of this document, the definitions given in SANS 60076-1 apply. 3.2 Abbreviations BIL: basic insulation level CSP: complete self-protecting HV: high voltage LV : low voltage SWER: single wire earth return 4 Rating 4.1 Rated
30、power The requirements of SANS 60076-1 apply. 4.2 Loading cycle Transformers shall be capable of performing a loading cycle as specified in SANS 60076-7. 4.3 Preferred values of rated power The rated power of a transformer shall be as required (see annex A) and shall preferably be one of the standar
31、d values given in column 2 of table 1. This standard may only be used and printed by approved subscription and freemailing clients of the SABS.SANS 780:2009 Edition 4 6 4.4 Operation at higher than rated voltage and/or at disturbed frequency The requirements of SANS 60076-1 apply. 4.5 Rating of the
32、low-voltage neutral terminal Unless otherwise required (see annex A), the rating of the low-voltage neutral terminal shall be at least 50 % of the rated current of the line terminals in the case of transformers with a power rating exceeding 630 kVA. In the case of a transformer that has a rating of
33、630 kVA or lower, the rating of the neutral bushing shall be the same as that of the line terminals. In the case of a miniature substation transformer, the rating of the neutral terminal shall be the same as that of the line terminals. 4.6 Basic insulation level Transformer windings and connected pa
34、rts shall be designed to the insulation level assigned by the user in accordance with table 2. 5 Requirements for transformers that have a tapped winding 5.1 General Notation of tapping range The requirements of SANS 60076-1 apply. 5.2 Tapping voltage Tapping current. Standard categories of tapping
35、voltage variation. Maximum voltage tapping The requirements of SANS 60076-1 apply. (See annex A.) 5.3 Tapping power. Full-power tappings Reduced-power tappings The requirements of SANS 60076-1 apply. 5.4 Specification of tappings in enquiry and order The requirements of SANS 60076-1 apply. 5.5 Speci
36、fication of short-circuit impedance The requirements of SANS 60076-1 apply. 5.6 Load loss and temperature rise 5.6.1 The requirements of SANS 60076-1 apply with the following additions: Component loss tolerances shall be in accordance with table 1 of SANS 60076-1:2008; and a) the losses as agreed up
37、on between the manufacturer and the purchaser (see annex A); or b) the appropriate component loss values given in column 3 or 4 or 5 (as relevant) and column 6 of table 1, except that, This standard may only be used and printed by approved subscription and freemailing clients of the SABS.SANS 780:20
38、09 Edition 4 7 1) if the rated no-load secondary voltage differs from one of the appropriate values given in column 1 of table 1 by more than 5 % of that value, the appropriate component loss value given in column 6 of table 1 shall be increased by 10 %; and 2) in the case of a tapped dual-ratio tra
39、nsformer (i.e. a transformer that has a high-voltage winding that can be connected for either one of two rated voltages without affecting phase displacement), the appropriate component loss values given in column 3 or 4 or 5 (as relevant), and column 6 of table 1 shall each be increased by 10 %. NOT
40、E The losses in table 1 will be subject to periodic review to ensure that the capitalized transformer losses are not excessive. 5.6.2 The pressure build-up during the temperature-rise test shall not exceed 20 kPa. 5.7 Off-circuit tapping switch The requirements of SANS 60076-1 apply with the followi
41、ng additions: When an off-circuit tapping switch is fitted, a) it shall be a ganged switch that is operated by means of an external handle; b) the switch shall be positively located in each operating position; c) facilities shall be provided for the use of a padlock to prevent unauthorized operation
42、 of the switch; d) each position of the switch shall be indicated by means of a number displayed in legible and indelible marking; and e) the numbers referred to in (d) shall be given on the diagram plate. 5.8 External tapping connections 5.8.1 When external tapping connections are provided (see tab
43、le 3), they shall be brought out by means of bushings on the low-voltage side. 5.8.2 The following tapping connections shall be provided: a) MV to single-phase, LV: 240 V secondary, 3 LV taps, 0 %, +2,5 %, +5 % (only boost taps); b) MV to dual phase, LV: 480/240 V secondary, 5 MV taps, -5 %, -2,5 %,
44、 0 %, +2,5 %, +5 %; c) MV to three-phase LV: 420 V secondary, 5 MV taps, -5 %, -2,5 %, 0 %, +2,5 %, +5 %; d) MV to 19 kV SWER: 19 kV secondary, 5 MV taps, -5 %, -2,5 %, 0 %, +2,5 %, +5 %. NOTE MV includes 3,3 kV, 6,6 kV, 11 kV, 22 kV and 33 kV. 5.8.3 Tapped dual-ratio transformers (i.e. transformers
45、 that have a high-voltage winding that can be connected for either one of two rated voltages) shall, when connected for the higher rated voltage, comply with the requirements of 5.6. 5.8.4 The tapping range, when the transformer is connected for the lower rated voltage, using the same tapping connec
46、tions on the same phase windings as for the higher ratio, shall be in accordance with the design. The tapping range at the lower rated voltage shall be as stated by the manufacturer. This standard may only be used and printed by approved subscription and freemailing clients of the SABS.SANS 780:2009
47、 Edition 4 8 6 Connection and phase displacement symbols for three-phase transformers 6.1.1 Subject to the provisions of 6.1.2, current-carrying connections to bushings shall be sufficiently flexible to prevent strain on the bushings and fracture of the connections during transportation. 6.1.2 The d
48、esign and construction of current-carrying connections shall be such that contact between phase conductors, and between any phase conductor and a neutral conductor or any earthed metal, is not possible under short-circuit conditions. 6.1.3 Unless otherwise required (see annex A), the transformer sha
49、ll be marked by the Vector symbol, Dyn11 or Yzn11. 7 Rating plates 7.1 Information to be given in all cases The requirements of SANS 60076-1 apply with the following addition: Month of manufacture. 7.2 Additional information to be given when applicable The requirements of SANS 60076-1 apply. 8 Miscellaneous requirements 8.1 Dimensioning of neutral connection The requirements of SANS 60076-1 apply including the requirements in 8.14. 8.2 Oil preservation system The requirements of SANS 60076-1 apply including of the requirements i
