Transformer bushings, type GOA 250 Installation and maintenance guide
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Safety information Keep this instruction available to those responsible for the installation, maintenance, and operation of the bushing. The installation, operation, and maintenance of a bushing present numerous potential unsafe conditions, including, but not limited to, the following: High pressures Lethal voltages Moving machinery Heavy components Slip, stumble or fall Specialized procedures and instructions are required and must be adhered to when working on such apparatus. Failure to follow the instructions could result in severe personal injury, death, and/or product or property damage. Additionally, all applicable safety procedures such as regional or local safety rules and regulations, safe working practices, and good judgement must be used by the personnel when installing, operating, maintaining and/or disposing such equipment. Safety, as defined in this instruction, involves two conditions: 1. Personal injury or death. 2. Product or property damage (includes damage to the bushing or other property, and reduced bushing life). Safety notations are intended to alert personnel of possible personal injury, death or property damage. They have been inserted in the instructional text prior to the step in which the condition is cited. The safety conditions are headed by one of the three hazard intensity levels which are defined as follows: DANGER Immediate hazard which will result in severe personal injury, death, or property damage. WARNING Hazard or unsafe practice which could result in severe personal injury, death, or property damage. CAUTION: Hazard or unsafe practice which could result in minor personal injury, or property damage.
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Contents 1 Description 6 1.1 Design 6 1.2 Ordering particulars 8 1.3 Electrical and technical data 9 2 Installation 10 2.1 Transport and handling 10 2.2 Lifting from the box 10 2.3 Mounting 10 2.3.1 Inner terminal 10 2.3.2 Outer terminal 10 2.4 Mounting of draw rod 11 2.5 Mounting of outer terminal 11 3 Maintenance 12 4 Disposal after end of service life 13 2750 515-144 en 5
1 Description 1 Description This information is valid for the revised and improved GOA 250 with catalogue number LF 123 260. The new bushing is completely interchangeable with the old one, if the upper part of the draw rod will be changed togethter with the bushing. NOTE: The part above the flange is 45 mm longer than for the old design. The table below shows the old and the new catalogue numbers. The old bushing The new bushing Catalogue No. Insulator Catalogue No. Insulator Brown Grey Brown Grey LF 123 021 -A -C LF 123 260 -A -D LF 123 023 -A -C LF 123 260 -B -E LF 123 087 -A -C LF 123 260 -C -F 1.1 Design The design priciple is shown in Fig. 1. The GOA 250 bushing is built up around a centre conductor tube made of electrolytic copper. The capacitance graded body is wound on a separate thin-walled supporting tube. This tube is only connected to the inner current carrying tube at the bottom end. The space between the two tubes makes and efficient cooling duct for dissipation of the heat, thus improving the current carrying capacity of the bushing. The upper insulator, the lower insulator and the mounting flange are held between the end details by the centre tube. A set of springs in the top housing provides adequate pressure on all gaskets, independent of temperature and load conditions. Sealing is accomplished by oil resistant rubber gaskets in grooves. The bushing is filled with insulating oil. The top housing has expansion space for the oil. Variations in the length of the centre tube and the housing are compensated by a flexible top cover. The mounting flange, the top housing and the top cover are made of corrosion resistant aluminium and are protected by painting with two-component primer and a grey-blue finishing coat paint. The standard colour is Munsell 5.5B 55/1.25, environmental class C3. The bushing is intended for mounting up to 45 to the vertical. Due to the high current rating, only the draw rod connection system is available. The centre tube of the bushing is used as the current conductor. The transformer leads are fitted with cable lugs, which are bolted to the inner terminal plate. This plate is drawn against the lower end of the tube by a thin steel draw rod. The bushing is furnished with a test tap according to Fig. 2. The test voltage for the tap is max. 2 kv. 6 2750 515-144 en
1 Description Fig. 1. Design principle. 1. Outer terminal stud 2. Top end nut 3. Flexible cover 4. Oil filling plug, 2522 731-A (Gasket 16 x 8 x 3 nitrile rubber) 5. Prism glass, 2744 322-A 6. Set of springs 7. Top housing 8. Oil 9. Porcelain insulator, air side 10. Test tap 11. Mounting flange 12. Condenser body 13. Flange extension 14. Porcelain insulator, oil side 15. Bottom end nut 16. Inner terminal plate 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 goa_0001 Fig. 2. Test tap 2769 531-A (not self-earthing) 2 1. Bushing for test tap 2. Disc spring 3. Press nut 4. Cover 5. Contact pin, 4 mm 6. O-ring 7. O-ring 8. Cable gob_0015 2750 515-144 en 7
1 Description 220 D 140 H 775 270 480 goa_0001 Outer terminal assembly 60 18 L1±2 L2 60 D 290 126 Earthed layer 10 20 90 16 goa_0004 Draw rod (included) H H1 18 D 45 40 250 Inner terminal plate goa_0006 goa_0003 Bushing 1.2 Ordering particulars When ordering, please state: Type and catalogue number for the bushings. Catalogue number for the outer terminal assembly. Catalogue number for the inner terminal plate. Additional accessories or modifications. Test required in addition to the normal routine tests. 8 2750 515-144 en
1 Description 1.3 Electrical and technical data Rated voltage U R Phase-to-earth voltage U Y Dry lightning impulse Wet power frequency Routine test 1 min. dry 50 Hz Design dry switching impulse Rated current IEC Rated current IEEE Creepage distance total Creepage distance protected Max. permitted cantilever load perpendicular to the terminal Corresponding 1 min. test 52 kv, RMS 52 kv, RMS 250 kv, peak 105 kv, RMS 105 kv, RMS 230 kv, peak 2500 A 2200 A 1500 ±50 mm 580 mm 1000 N 2000 N Dimensions and nominal capacitance Catalogue No. Porcelain L1 L2 D Mass C 1 C 2 Brown Grey mm mm mm kg pf pf LF 123 260 -A -D 220 0 126 59 180 200 LF 123 260 -B -E 485 265 150 70 350 450 LF 123 260 -C -F 685 485 150 76 415 600 Outer terminal assembly Catalogue No. D, mm H, mm Material/Surface Mass, kg LF 170 017-CA 40 125 Cu 3.0 LF 170 017-CB 60 145 Al 2.0 LF 170 017-CC 2"-12 UN 125 Cu/Sn 3.7 Inner terminal plate Catalogue No. H, mm H1, mm D, mm Mass, kg LF 170 018-A 75 35 18 1.7 LF 170 018-K 90 50 13 2.0 LF 170 018-L 85 45 14 1.8 2750 515-144 en 9
2 Installation 2 Installation 2.1 Transport and handling CAUTION: The bushing may be transported and stored horizontally up to 6 months. For storing over 6 months it is recommended to raise the bushing to vertical position with the top end upwards. Keep the bushings dry and clean and protected against mechanical damage. Keep the bushings protected from penetrating water when stored outdoors. This means that the case must not be stored in areas where it can be foreseen that the ground will be wet and muddy during heavy rains. Shelter the case from rain and snow with a tarpaulin or roofing. Carefully inspect the bushing on receiving with regard to shipping damage. Please note that the bushing has been routine tested in oil and some oil may be left, especially in the narrow openings between porcelain and metal. Vaseline is used for lubrications of threads, and at some temperatures the vaseline may appear as oil The bushings are normally delivered from ABB Components in boxes with the bushing supported by blocks and fibre boards. The boxes are marked with "Top End". 2.2 Lifting from the box WARNING For lifting the bushing from the box, apply lifting slings or ropes around the the air side insulator under the top housing. 2.3 Mounting The oil end of the bushing and the inside of the centre tube shall be carefully cleaned and inspected. 2.3.1 Inner terminal The connection of the bushing to the transformer or reactor is made by means of a draw rod. The draw rod bottom plate is made of copper. 2.3.2 Outer terminal The outer terminal is made of copper or aluminium. 10 2750 515-144 en
2 Installation 2.4 Mounting of draw rod At the upper end, the rod passes through a spring device. The rod is fixed by a nut on the cover of the spring device. At mounting the spring device shall be tightened until the cover is at the same level as the upper end of the conductor tube. See Fig. 3. 2.5 Mounting of outer terminal CAUTION: Before connection of conductor clamps, the outer terminals of aluminium must be carefully wire brushed and greased with a contact compound or vaseline. The inner contact surface on aluminium outer terminals are tin-zink plated, and wire brushing must thus not be carried out. In order to obtain the correct pressure and a low contact resistance, the following must be carried out: 1. Clean the contact and gasket surfaces carefully. 2. Lubricate the O-ring with Mobilgrease 28. 3. Assemble the retainer ring, the O-ring, and the outer terminal stud and push them over the inner terminal. An extra O-ring intended for final installation is delivered with the bushing. 4. Grease all bolts on thread and underneath the head with Molykote 1000, or other suitable compound. 5. Insert and tighten the screws M10, with plane washer, which press the stud against the top end of the bushing. Tighten stepwise to a final torque of 40±4 Nm. 6. Insert the M8 screws, with conical spring washer and plane washer, which hold the tightening ring. Tighten the screws alternately to a final torque of 20 ±2 Nm to obtain the necessary gasket pressure. CAUTION: It is extremely important in both cases to tighten evenly. The bolts shall thus be tightened in steps, alternately on both sides. 2750 515-144 en 11
3 Maintenance Hole for fastening of the pull-through cord The nut shall be tightened until the plate is at the same level as the upper end of the tube. Tightening torque approx. 40 Nm. 6 7 1 2 3 4 5 Tightening torque approx. 20 Nm. Fig. 3. Connection of bushing. 1. Hexagon screw M8 x 30 2. Conical spring washer 8.4 x 18 x 1 3. Gasket (O-ring) 49.2 x 5.7 4. Tightening ring for gasket 5. Top end of bushing 6. Hexagon screw M10 x 60 7. Washer 10.5 x 20 x 2 8. Inner terminal plate 8 goa_0002 3 Maintenance The GOA bushings are maintenance-free. It is, however, recommended that the oil level is checked at normal routine inspection. Correct oil level for a vertical bushing is at the middle of the prism glass for 20 C. The change of the oil level is approx. 1.5 mm for 10 C change of the temperature. Adjustment of the oil level is carried out by opening the filling plug. Then drain or fill up with pure new dry transformer oil. For remounting of the sealing plug a new gasket may be used. Adjustment of the oil level is allowed only when the temperature of the bushing is between +5 C and +35 C. 12 2750 515-144 en
4 Disposal after end of service life 4 Disposal after end of service life The bushing consists of the following material: - Centre tube of copper. - Terminals of copper, brass or low-alloy aluminium may be plated with for instance silver, tin, gold or nickel in layer thickness up to 20 µm. - Transformer oil as per IEC 296, class 2. - Transformer oil impregnated condenser body consists of paper and 1 % Al foils. - Supporting tube, on which the condenser body is wound, consists of brass. - Top cover, top housing, flange, top nut and flange extension consist of Al alloys. - Press ring for oil level glass consist of plated brass. Test tap consists of stainless steel. - Prism glass consists of glass. - Insulators consist of quartz or alumino silicated based porcelain. 2750 515-144 en 13
ABB Power Technology Products AB Components Visiting address: Lyviksvägen 10 Postal address: SE-771 80 Ludvika, SWEDEN Tel.+46 240 78 20 00 Fax +46 240 121 57 E-mail: sales@se.abb.com www.abb.com 2750 515-144 en, 2001-01-30