098 : 2000 CEB STANDARD MEDIUM VOLTAGE DISTRIBUTION TRANSFORMERS CEYLON ELECTRICITY BOARD SRI LANKA

Transcription

1 098 : 2000 CEB STANDARD MEDIUM VOLTAGE DISTRIBUTION TRANSFORMERS CEYLON ELECTRICITY BOARD SRI LANKA

2 Specification for MEDIUM VOLTAGE DISTRIBUTION TRANSFORMERS CEB Standard 098 : 2000 CEYLON ELECTRICITY BOARD No. 50, Sir Chittampalam A. Gardener Mawatha, Colombo 2. Sri Lanka Telephone: , Facsimile: cebdp@mega.lk

3 CEB STANDARD 098: 2000 CONTENTS Page 1.0 Scope System Parameters Service Conditions Applicable Standards Technical Requirements Basic Features Additional Requirements Quality Assurance Information to be furnished with the Offer Inspection & Testing Annex. 9 1

4 CEB STANDARD 098: 2000 SPECIFICATION FOR MEDIUM VOLTAGE DISTRIBUTION TRANSFORMERS 1.0 SCOPE This Specification covers the general requirements of the design, manufacture, testing, supply and delivery of medium voltage 12kV and 36kV distribution transformers. 2.0 SYSTEM PARAMETERS a) Nominal Voltage - 11kV 33kV b) System highest voltage - 12kV 36kV c) System frequency - 50Hz. 50Hz d) Number of phases e) Type of earthing - Effective Non effective f) System fault level MVA 1000MVA 3.0 SERVICE CONDITIONS a) Annual average ambient temperature - 35 C b) Maximum ambient temperature - 40 C c) Maximum relative humidity - 90% d) Environmental conditions - Humid tropical climate with heavily polluted atmosphere. e) Operational altitude - From MSL to 1900m above MSL f) Isokeraunic (Thunder Day) level - 90 days/year 4.0 APPLICABLE STANDARDS The equipment and the components supplied shall be in accordance with the latest edition of the standards specified below and amendments thereof. However the CEB Specification shall supersede these Standards in the event there is a discrepancy a) IEC (1995) Insulating bushing for alternating voltages above 1 kv b) IEC (1995) Insulating liquids-determination of the breakdown voltage at power frequency test methods c) IEC (1982) Specification for unused minerals insulating oils for transformers and switch-gear d) IEC (1991) Loading guide for oil-immersed transformers e) IEC (1987) Determination of transformer and reactor sound levels f) IEC (1978) Terminal and tapping markings for power Transformers g) IEC (1982) Guide to the lightning impulse and switching impulse testing of power transformers and reactors. 2

5 CEB STANDARD 098: 2000 i) IEC 0076 (1993) Power Transformers j) IEC (1986) Guide for the selection of insulators in respect of polluted conditions k) BS 2562 (1997) Cable boxes for transformers and reactors l) BS 5493 (1997) Protective coating of iron and steel structures against corrosion 5.0 TECHNICAL REQUIREMENTS 5.1 Medium Voltage Characteristics a) Nominal voltage 11kV 33 kv b) Rated voltage 12kV 36 kv d) Rated fault level 1000MVA 1000MVA e) Lightning impulse withstand voltage (peak) 75kV 200kV f) One min power frequency withstand voltage 28kV 70kV g) Off load tapping (Primary side) + 2.5%,0%, -2.5%, -5%, -7.5% h) Insulator creepage distance 290mm 720mm 5.2 Low Voltage a) Nominal system voltage 230/400 V b) Maximum system voltage 254/440 V c) One minute test voltage 3,000 V d) Impulse (1.2/50µ) wave withstand voltage 6,000 V 5.3 Other Performance Characteristics a) Vector group Dyn11 b) System frequency 50Hz c) Cooling type ONAN d) Insulation temperature class (IEC 76). A e) For uninterrupted continuous operation the rated power at 30 0 C ambient, maximum winding temperature rise 60 0 C f) Maximum top oil temperature rise (without conservator) 55 0 C g) Short circuit impedance voltage at 75 0 c between 4.0 p.u. and 5.0 p.u. h) Maximum noise level at 0.3m measured in accordance with IEC 551 [(tolerance 2dB (A))] 65dB(A) i) Short time withstand current duration (Under three phase faults) 2 seconds. j) No load loss and full load loss (corrected at 75 o C) at rated values, shall not exceed the values indicated in Table 1.0 for the respective transformers. 3

6 Table 1.0 CEB STANDARD 098: 2000 Transformer (kva) No Load loss (W) Full load loss (W) 100 kva, 11kV / 415V kva, 11kV / 415V kva, 11kV / 415V kva, 11kV / 415V kva, 33kV / 415V kva, 33kV / 415V kva, 33kV / 415V kva, 33kV / 415V BASIC FEATURES The transformers shall be of hermetically sealed type and suitable for outdoor application. They shall be fully rated at ambient temperature of 35 0 C. and the typical operating characteristics specified in clause 5.0 technical requirements shall apply to all transformers. 6.1 Transformer Construction The transformers shall be double-wound, oil immersed naturally cooled and hermetically sealed fully filled type The transformers for rating upto 250kVA shall be of pole mounted type and the 400 kva shall be of plinth mounted type The core shall be of high grade cold rolled grain oriented silicon sheet steel and securely clamped. The transformer core shall be of three limbs stacked core type The primary and secondary windings shall be constructed from high conductivity E.C. grade copper. All turns of windings shall be adequately supported to prevent movement. The high voltage winding shall be of layered winding and the low voltage winding shall be of foil winding using Copper sheets The core and coil assembly shall have the core and coils rigidly connected. The core/coil assembly shall be mounted on the cover plate so that the assembly could be removed from the tank using the suitably placed lugs provided on the cover plate No material which can be deleteriously affected by the action of oil under the operating conditions of the transformers shall be used in the transformers or leads or bushings To ensure that the core and coils of transformers are seated on the floor of the tank, supporting frames shall be designed to accommodate variations in tank height. The core and coil assembly shall be rigidly connected to the tank and suitably closed lugs shall be provided for removing the core and coil assembly from the tank Construction features shall permit local repairs to be easily carried out in the event of equipment failure. 4

7 CEB STANDARD 098: Transformer Tank The transformer tank shall be fabricated from steel and shall be of robust construction. Care should be taken at the manufacturing stage so as not to have leaks during transportation or when the transformer is continuously operated at rated power With the exception of radiator elements, all external joints shall be seam welded. There shall be only one vertical seam weld for the fin radiator and the other three vertical corner edges of the transformer shall be formed by bending. Corner ribs shall be avoided for the fin radiator. The bearing surface of the tank to which bushings are clamped shall be substantially flat All matching faces of joints shall be made oil tight and finished with a smooth surface to ensure that the gasketing materials make a satisfactory joint Flanges and covers of tanks shall be of sufficient thickness to prevent any depression occurring, which would retain water around the bolts. The horizontal edges of the cover plate shall be bent over the tank flange to facilitate water dripping out of the tank. The bent collar width shall be about 10mm to 15mm All the nut and bolts used shall be hot dip galvanised and spaced at sufficiently close intervals to avoid buckling of either flange or covers and shall provide reasonably uniform compression of the gasket Each transformer shall be provided with a minimum of two closed lifting lugs. The minimum diameter of the hole or width of the slot shall be 25 mm. The two lifting lugs shall be located such that there would be a minimum of 50 mm between the lifting chain and the nearest part of the bushings All transformers shall be suitable for outdoor mounting on pole or plinth platforms and shall have four mounting lugs with 12 mm diameter holes suitable for bolting the transformer to the platform. Bolt hole spacing shall be as specified by the purchaser to suit mounting requirements. 6.3 Transformer Sealing / Gasket The transformers shall be of the hermetically sealed type and provided with a satisfactory lid sealing gaskets The gasket shall of the good quality to maintain the sealing effect through its life span and shall prevent seeping of oil due to ageing and extreme operating temperature Gaskets provided with the transformers shall be suitable for making oil tight joints, and there would be no deleterious effects on either gaskets or oil when the gaskets are continuously in contact with hot oil. No gaskets shall be used in which the material of the gasket is mounted on a textile backing Exterior gaskets shall be of rubberized cork material, weatherproof and shall not be affected by strong sunlight. 5

8 6.4 Internal and External Finish CEB STANDARD 098: Both internal and external surfaces of the transformer shall be hot dip galvanized in compliance with ISO/BS/EN 1461: The surfaces shall be free of any zinc burrs both inside and outside After galvanizing, the external surface shall be prepared for powder painting by applying a suitable etch primer. The effect of etch primer shall be to avoid powder coating being peeled off from the galvanized surface. The powder shall then be applied and the powder used shall be an epoxy polyester cured with hydroxil alkyl. The powder coating thickness shall not be less than 50μm 6.5 Rating Plate A brass /stainless steel rating plate shall be fitted to each transformer. The information shall be deeply etched including the diagram of the connections of the windings, the vector diagram showing the general phase relations of the transformer, and a diagrammatic plan of the transformer cover showing the terminal positions and marking and other essential particulars The plate shall be mounted in an accessible position and following information shall be clearly and indelibly marked in English language. a) Transformer type b) Manufacturer's name c) Manufacturer's serial number d) Year of manufacture e) Number of phases f) Rated power at 30 O C g) Rated frequency h) Rated voltages i) Rated currents j) Connection symbol k) Mass of insulating oil l) Insulation levels m) Details regarding tapping n) Gross weight o) Impedance voltage at rated current Type of cooling total mass 6.6 Bushings All bushings shall be of porcelain clad, of the highest quality and comply with IEC 137. Creepage distance of the bushing insulator shall be 290mm for 12kV transformer and 720 mm for 36kV transformers. They shall be sealed in a manner to prevent ingress of moisture and to facilitate removal. The neutral bushings and stems shall be identical to those provided for phase terminations. Bushing palms shall be made of brass and be suitable for the bolting of conductor compression lugs The palms shall be suitably dimensioned, to suit the bushing rod and the holes spaced sufficiently apart to enable tightening of bolts using standard spanners and to prevent overlap of lugs. The LV bushing palms shall be as indicated in the drawing No. DS&S/2000/98A. 6.7 Terminal Leads Outgoing leads shall be brought out through bushings, the leads shall be such that the core and coils could be removed with the least possible interference with these leads, and they shall be specially supported inside the transformer to withstand the effects of vibration and short circuits. 6

9 CEB STANDARD 098: The leads shall be so fixed that they do not break at the connection and would not twist and touch each other in case the bushing is turned accidentally. 6.8 Earthing Connections Earthing connections shall be provided with connection facilities for 50mm 2 copper stranded conductor Three bolts of M12 size shall be located on either side of the tank base (two) and on the cover plate (one). 6.9 Off Load Tap Changer Voltage tappings shall be provided on the primary side of each transformer. Tapping step shall be ±2.5%. Number of tappings shall be as stipulated in the Clause 6.0 Technical Requirements The tappings shall be selected by an 'off load' tapping switch with an external hand wheel with provision for locking on to a selected tapping. The shaft shall be adequately sealed so that no seepage of oil occurs under all conditions of service The voltage operating positions, together with tap change positions shall be ` clearly and indelibly marked Surge Arrester Mounting Bracket The surge arrester mounting bracket made of steel shall be provided on the transformer cover plate The bracket shall be hot dip galvanised and suitable to accommodate three Nos. of surge arresters as indicated in the drawing No. DS&S/2000/98B 6.11 Oil All transformers shall be filled to the required level with a new, unused, clean, standard mineral oil in compliance with IEC Pressure Relief Valve The transformer tank shall be fitted with a suitable pressure relief valve to operate when the pressure exceeds 0.3 bars to prevent explosion of the transformer due to internal fault. 7.0 ADDITIONAL REQUIREMENTS 7.1 Terminal Marking All transformers shall have the primary and secondary terminal markings plainly and indelibly marked on the transformer adjacent to the relevant terminal. These markings shall be 25mm in height. 7

10 7.2 Radio Interference CEB STANDARD 098: 2000 When operated at voltage even up to 10% in excess of the normal system rating, transformers shall be substantially free from partial discharges (i.e. corona discharges in either internal or external insulation) which are likely to cause interference with radio or telephone communication. 7.3 Routine Tests The following routine tests as per IEC : 1993 shall be carried out on all the distribution transformers ordered and the routine test reports shall be made available for the observation of the CEB Inspector at the time of inspection. a) Measurement of winding resistance b) Measurement of voltage ratio and check of voltage vector relationship c) Measurement of impedance voltage, short-circuit impedance and load loss d) Measurement of no-load loss and current e) Dielectric routine tests f) Oil breakdown test g) Pressure test at 0.25 bar above atmospheric 7.4 Spare Parts and Tools The supplier shall specify the spare parts required for proper and continuos functioning of the transformers. The supplier shall also specify if any special tools are required for the maintenance of transformers other than those conventional for transformers. A schedule of prices and quantities of spare parts and special tools shall be given by the supplier. 7.5 Outline Drawings, Maintenance Manual and Packing Outline drawings and other necessary drawings baring an effect on customers' installation shall be provided with each transformer and a comprehensive maintenance manual shall also provided. 8.0 QUALITY ASSURANCE The manufacturer shall posses ISO 9001 Quality Assurance Certification for the manufacture of distribution transformers for the plant where the manufacture of distribution transformers is done. Bidders shall furnish a copy of the ISO certificate certified as true copy of the original by the manufacturer, along with the offer. 9.0 INFORMATIONS TO BE FURNISHED WITH THE OFFER 9.1 The following Information shall be furnished the offer a) Particulars requested in annex - A. b) Constructional features and materials used for components c) Separate explanatory drawings and dimensions of tap changer. d) Overall dimensional drawings e) Drawing of Rating plate to scale incorporating the particulars called for. f) Certified copy of the quality assurance conforming to ISO

11 CEB STANDARD 098: Type Tests Certificates The following Certificates of Type tests as per IEC by an internationally recognised independent testing authority shall be furnished with the offer a) Lightning Impulse withstand voltage test b) One minute wet power frequency withstand voltage test c) Temperature-rise test d) Acoustic sound level measurements e) Short-circuit tests The Type Test Certificates for short circuit tests shall be from one of the following testing authorities who are the members of the European Organization for Testing and Certification for Short Time Current Test and Short Circuit Breaking / Making Tests i) ASTA Certification Services - (ASTA) UK ii) Centro Electtrotecnico Sperimentale Italiano S. P. A. - ( CESI) Italy iii) Ensemble Des Stations D Essais a Grande Puissance Francaises (ESEF) - France iv) B.V. KEMA - (KEMA) - Netherlands v) Gesellschaft for Elektrische Hochleistungsprufungen - PEHLA- Germany vi) Scandinavian Association for Testing of Electrical Power Equipment - (SATS) - Scandinavia vii) Short Circuit Testing Liasion North America - (STLNA) - North America viii) Central Short-Circuit Testing Committee - (JSTC) - Japan Offers of Bidders who failed to provide above particulars in full shall be rejected INSPECTION AND TESTING 10.1 Inspection The selected Bidder shall make necessary arrangements for inspection of the equipment by an Engineer appointed by the Purchaser and also to carry out in his presence necessary Acceptance / sample tests of the materials and equipment, offered Acceptance /Sample Tests The following Acceptance/Sample tests conforming to IEC (1993) shall be witnessed by the Engineer. Extra copies of these Test Certificates shall also be supplied with the equipment. a) Measurement of winding resistance b) Measurement of voltage ratio and check of voltage vector relationship c) Measurement of impedance voltage, short-circuit impedance and load loss d) Measurement of no-load loss and current e) Dielectric routine tests f) Oil breakdown test g) Pressure test at 0.25 bar above atmospheric 11.0 ANNEX A - B - C - Details of Flag for 250A / 630A Bushings Surge Arrester Mounting Bracket Schedule of guaranteed technical particulars - To be filled by the Bidder 9

12 CEB STANDARD 098: 2000 ANNEX - C SCHEDULE OF GUARANTEED TECHNICAL PARTICULARS To be filled by the Bidder for each rating (kv & kva) offered 1. Name of manufacturer & country of origin - 2. Applicable Standard - 3. Voltage rating kv/v - 4. Capacity kva - 5. Vector group - 6. Frequency Hz - 7. Cooling type - 8. Insulation temperature class - 9 Maximum winding temperature rise at Uninterrupted continuous operation, at rated power and at ambient temperature of 30 0 C 10. Maximum top oil temperature rise 0 C - 0 C Short circuit impedance voltage at 75 0 C pu Maximum noise level at 0.3m as per IEC 551 db No load Loss at 75 0 C W Full load Loss at 75 0 C W Lightning impulse withstand voltage (peak) kv Wet power frequency withstand voltage kv LV (1min) power frequency withstand voltage V LV impulse withstand voltage V Total creepage distance of the bushings mm Tap changer steps (number of steps) % Total weight kg - 10

13 22. Whether the offered transformers fully conform with CEB STANDARD 098: 2000 a) Clause Transformer Construction Yes/No. - b) Clause Transformer Tank Yes/No. - c) Clause Transformer Sealing Yes/No. - d) Clause 6.4 Internal & External Finish Yes/No. - e) Clause 6.5 Rating Plate Yes/No. - f) Clause 6.6 Bushings Yes/No. - g) Clause 6.7 Terminal Leads Yes/No. - h) Clause Earthing Connections Yes/No. - i) Clause 6.9 On Load Tap hanger Yes/No. - j) Clause Arrester Mounting Bracket Yes/No. - k) Clause 6.11 Oil Yes/No. - l) Clause 6.12 Pressure Relief Valve Yes/No. - m) Clause 7.1 Terminal Marking Yes/No. - n) Clause 7.2 Radio Interference Yes/No. - o) Clause 7.3 Routine Tests Yes/No Indicate the particulars of Spares to be supplied with each transformers Whether the Type Test Certficates as per Clause 9.2 are furnished Yes/no Whether the Acceptance /Sample Tests as per Clause 10.2 will be carried out Yes/No Whether the certificate of ISO 9001 quality Assurance furnished. Yes/No. - I/We certify that the above data are true and correct SEAL AND SIGNATURE OF THE MANUFACTUER / DATE Distribution transformers 11

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16 Amendment Slip No. 01 Effective from 02 nd December 2004 To CEB Standard 098 : 2000 Specification for Medium Voltage Distribution Transformers REVISED TEXT December 2004 THE PROPOSED AMENDMENT TO CEB STANDARD 098 : 2000 SPECIFICATION FOR MEDIUM VOLTAGE DISTRIBUTION TRANSFORMERS Clause 9.2 of the CEB Standard is amended to read as follows. 9.2) Type Test Certificates The following Certificates to Type Tests as per IEC by an internationally recognized independent testing authority shall be furnished with the offer. a) Lighting Impulse withstand voltage test b) Short-Circuit Tests The Type Test Certificates for short circuit tests shall be from one of the following testing authorities who are the members of the European Organization for Testing and Certification for Short Time Current Test and Short Circuit Breaking/Making Tests. i) ASTA Certification Servgices (ASTA) UK ii) Centro Electtrotecnico Sperimentale Italiano S.P.A. (CESI) Italy iii) Ensemble Des Stations D Essais a Grande Puissance Francaises (ESEF)-France iv) B.V.KEMA (KEMA) Netherlands v) Gessellschaft for Elektrische Hochleistungsprufungen PEHLA- Germany vi) Scandinavian Association for Testing of Electrical Power Equipment SATS)-Scandinavia vii) Short Circuit Testing Liasion North America (STLNA)-North America viii) Central Short-Circuit testing Committee (JSTC)-Japan The following Type Test Certificates shall also be provided from independent Testing Authorities. a) One minute wet power frequency withstand voltage test b) Temperature rise test c) Acoustic sound level measurements All type test certificates under clause 9.2 shall be furnished for 33kV/LV, 100kVA or 33kV/LV 160kVA or 33kV/LV 250 kva Transformers Offers of Bidders who failed to comply with the above in full shall be rejected. Amd. Slip 98

17 Amendment Slip No. 02 Effective from 07 th July 2005 To CEB Standard 098 : 2000 Specification for Medium Voltage Distribution Transformers REVISED TEXT July 2005 THE PROPOSED AMENDMENT TO CEB STANDARD 098 : 2000 SPECIFICATION FOR MEDIUM VOLTAGE DISTRIBUTION TRANSFORMERS Following Clause shall be added as Clause ) Manufacturing Experience The bidder should have a minimum experience of ten years of design, manufacture and supply of Transformers similar to the requirements of the bidding documents. Amd. Slip 98

18 Amendment Slip General Amendments to CEB Specification Effective from REVISED TEXT 1. Tender form, Schedule of Prices, Letter of Authorization, Power of Attorney documents shall be signed in Blue Ink. Name of the persons signing shall be clearly indicated and their official stamp has to be put in. 2. Bidders shall include with their offer the Type Tests Report/Certificates in accordance with the Standard specified, obtained from an accredited independent test laboratory acceptable to the CEB. Proof of accreditation by a national/international authority shall also be forwarded with the offer. Test Reports shall be complete including all the pages as issued by the Testing Authority. Parts of the Test Report shall not be acceptable. R\slip.LF