PNO Condenser Bushings from 52 kv to 420 kv Oil-to-air - Oil-Impregnated Paper

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1 GE Grid Solutions PNO Condenser Bushings from 52 kv to 420 kv Oil-to-air - Oil-Impregnated Paper PNO bushings are capacitance graded bushings with an oil impregnated paper core. PNO bushings are conform to IEC / ISIS 2099 standards. Bushings are designed for use in power transformers and can be installed up to a maximum of 45 inclination from vertical. Key Benefits Bushings with longer lifetime and higher reliability Utilisation under extreme weather condition (lower pour-point value) No performance reduction with age Voltage and Current Ratings Rated voltage range for PNO bushings, normal cantilever load, is 52 to 170 kv. Heavy cantilever load is for bushings rated > 245 kv. PNO bushings, for a rated voltage, are designed in order to have the same overall dimensions for all the normal service currents. There are three connection alternatives for the conductor: Draw lead connection Draw rod connection Bottom/Solid Stem connection Bushing Design Design, components and manufacturing technology promote an average lifetime in excess of 30 years under normal operating conditions. Imagination at work

2 Main Features Range 52 to 420 kv Current up to 3,150 A Oil-impregnated paper Air side: porcelain insulator Oil side: epoxy resin insulator Partial discharge: max. 5 pc at 1.5 Un/ 3 High grade insulating oil Provided with power factor tap Head made of special UHV filter prismatic glass with oil level indication visible at any angle of sight for bushings rated up to 245 kv and metallic head with magnetic oil gauge for 420 kv bushings Flange made of cast aluminum alloy Standard angle of installation max. of 45 from vertical Components Fig. 2: Bushings 245 kv 1. HV Terminal 2. UHV filter glass 3. Porcelain 4. OIP Condenser 5. Winding tube 6. Power factor tap 7. Flange 8. Epoxy resin insulator 9. Oil side shield Fig. 1: Bushings 52 kv to 170 kv Fig. 2: Bushings 245 kv Fig. 3: Bushings 420 kv Fig. 3: Bushings 420 kv 1. HV Terminal 2. Oil level guage 3. Metal oil reservoir 4. Porcelain 5. OIP Condenser 6. Winding tube 7. Power factor tap 8. Flange 9. Epoxy resin insulator 10. Oil side shield 2

3 Manufacturing The active part of the bushing is the condenser body, manufactured using a continuous sheet of pure Kraft paper, wound around a central conductor tube or rod. During the winding process, the paper is dried by heated cylinders in order to reduce its water content to 1% maximum. A series of aluminum foils are coaxially inserted between the layers of the paper, to achieve the best possible distribution of the radial and longitudinal electrical gradients between the central tube and the flange, which is grounded. The winding is made by computer-controlled machines, with subsequent machining to achieve the final shape. After winding, each bushing is individually assembled and placed into an oven and then processed under vacuum for the appropriate period of time. Each bushing is then impregnated with Insulating Oil, which has been degassed and processed so that it has a maximum water content of 5 ppm. Each bushing is placed under pressure to ensure thorough impregnation and to test that it is properly sealed. After impregnation, the bushing head is filled with nitrogen gas cushion. This process is automatic and computer controlled. Top Terminal The standard bushing top terminal is made of tin plated copper. Upon request, it can be silver plated. The terminal is connected to the copper inner terminal lug or the draw rod by means of multiblade contacts and is secured to the bushing head by screws. Air Side The air side insulator is made of brown porcelain. The typical creepage distance is suitable for heavily polluted (25 mm/kv) atmospheres. The shed configuration is an alternating type: shortlong shed. The shed profile complies with IEC recommendations. A one-piece porcelain or multiple pieces porcelain, in order to meet Standards or special requirements, are used for bushings. Multiple pieces are glued using epoxy resin, without the use of gaskets, and the final porcelain is considered as a single piece. Flange The flange is made of aluminum castings, and is equipped with the following accessories: Eye Bolt for lifting purpose Power factor tap, tested at 2 kv for 60 s (fig. 4) Buchholz relay connection: 1/2 BSP outlet plug Oil sampling plug (for 245 kv bushings). Head and Oil Inducation Bushings are provided with glass or metallic head. Glass Head Bushings with oil head reservoir are prismatic in shape, made of borosilicate glass, and containing a UHV filter, which allows for an easy check of the oil level even from a distance and at any angle of sight. Metallic Head The metal component of the head is made of a cast aluminum alloy and is provided with oil level guage. Fig. 4: Power Factor Tap 1. Closing and grounding cap 2. Measurement electrode 3. Insulation tap 4. Gasket 5. Tap flange 6. Bushing flange 7. Last layer 3

4 Oil Side The oil side envelope is made of a molded epoxy resin. This resin is a two-part compound consisting of a resin base and a hardener; the filler material is quartz sand. The epoxy resin envelope permits shapes, thickness and dimensional tolerances not possible with porcelain. Under flange sleeve length for CT accommodation, different from standard, is available upon request. In this case, the grounded part is obtained by means of a metallic tube or directly by the last metallic layer inside the condenser body. Oil Side Shield The bottom end of the bushing is shielded by a proper deflector, made of aluminum alloy. It is designed to reduce the electric field stress in oil and to screen the connection between the lead coming from the transformer winding and the bushing itself. Bushings up to and including 170 kv have an integrated deflector. Bushings rated 245 kv and above have detachable deflector. Assembling The mechanical coupling among all the parts of the bushing is made by means of springs placed into the head of the bushings. 245 kv bushing are always assembled using (air side) porcelain cemented to flange (fig.5) as well as the ones for heavy cantilever ( H ) loads. All cemented surfaces, potentially in contact with the external environment, are silicone sealed (fig. 5). Fig. 5: Cemented porcelain 1. Porcelain 2. Cement 3. Metal cemented ring 4. Flange 5. Silicone sealing 4

5 Gaskets Made of Viton, a fluorocarbon rubber elastomer (FPM), o-ring type. They are compatible with all the fluids they are in contact with. Air side gaskets are carefully protected, by means of a sealing, against influence of polluting weather elements. For special requirements, such as low ambient temperatures (down to -55 C), special o-rings are used. Arcing Horns Adjustable arcing horns are available upon request. The upper arcing horn is fixed by means of one screw used to secure the top terminal, while the lower arcing horn is fixed on the flange (fig. 6). Tests All bushings are tested in accordance with IEC 60137/IS 2099 Standards: insulated bushing for alternating voltages above 1000 V. Fig. 6: Discharge distance for a bushing equipped with arcing horns 5

6 PNO Range 52 to 420 kv 4

7 Fig. 7: Draw lead conductor sections Fig. 8: H1 head type (Draw lead or draw rod up to 245 kv) Fig. 9: H2 head type (Bottom connection up to 245 kv - 2,000 A) Fig. 10: H3 head type (Draw lead or draw rod 362 to 420 kv) 1. Air draining plug 2. Lifting holes 3. Power factor tap 1. Air draining plug 2. Power factor tap 3. Lifting holes 4. Oil sampling valve 5. Magnetic oil sight glass Fig. 13: Flange fixing holes Fig. 11: PNO Bushings 52 through 170 kv Fig. 12: PNO Bushings 245 kv Fig. 14: PNO Bushings 420 kv 5

8 Packing - Transportation After tests and before packing, the bushing is cleaned of any oil or dust. Thanks to a special device to prevent the diffusion of the nitrogen cushion out of the head and into the lower end of the bushings, each bushing can be packed and shipped secured in horizontal position. Proper protection is used for oil side shields. Nameplate Each bushing is provided with a nameplate, containing complete electrical data and its serial number, in accordance with the requirements of IEC Standards. The stainless steel name plate is secured to the flange. Detail A Fig. 15: PNO Bushings 52 kv to 170 kv (draw rod connection) Fig. 16: PNO Bushings 245 kv (draw rod connection) Fig. 19: Bottom terminal connector for 800 A - 1,250 A Fig. 20: Bottom terminal connector for above 1,250 A - 3,150 A Fig. 18: PNO Bushings 52 kv to 170 kv (solid stem connection) Fig. 17: PNO Bushings 145 kv to 245 kv (solid stem connection) For more information please contact GE Grid Solutions Worldwide Contact Center Web: Phone: +44 (0) IEC is a registered trademark of Commission Electrotechnique Internationale. IEEE is a registered trademark of the Institute of Electrical Electronics Engineers, Inc. Modbus is a registered trademark of Schneider Automation. NERC is a registered trademark of North American Electric Reliability Council. NIST is a registered trademark of the National Institute of Standards and Technology. GE and the GE monogram are trademarks of General Electric Company. GE reserves the right to make changes to specifications of products described at any time without notice and without obligation to notify any person of such changes. PNO-Brochure-EN Grid-PTR Copyright 2018, General Electric Company. All rights reserved. Imagination at work