1._Transformer_Bushings_RD_YHV.pptx bushings

Bushing Rd

1. Transformer Bushings: Types, Features, Tests and Developments 15/02/2024 1 Mihir N. Velani Yash High Voltage, Vadodara Under the Aegis of ज्ञान-धारा Transformer Bushings

2. Electrical Power System 15/02/2024 2 Transformer Bushings Typical Electrical Power System: A lay out

3. Transformers: Working Principle 15/02/2024 Transformer Bushings 3 Ref. Electric Power Transformer Engineering by Leo L. Grigsby, CRC Press

4. Transformers: Components 15/02/2024 Transformer Bushings 4 OLTC Control Cabinet Radiators Conservator Tank Active Part Tank Cover Rails HV Bushings LV Bushings Cooling Fan Core Insulation

5. Transformers: What is an electrical bushing? IEEE Std. C57.19.00: An insulating structure, including a through conductor or providing a central passage for such a conductor, with provision for mounting a barrier, conducting or otherwise, for the purpose of insulating the conductor from the barrier and conducting current from one side of the barrier to the other. To transmit electrical power in or out of enclosures, i.e., barriers, of an electrical apparatus such as transformers, circuit breakers, shunt reactors, and power capacitors. 15/02/2024 Transformer Bushings 5

6. Bushings: Types/classification 15/02/2024 Transformer Bushings 6

7. Bushings: Current Carrying Paths 15/02/2024 Transformer Bushings 7

8. Bushings: Applications Air-to-Oil – used in outdoor air insulated substation (AIS) equipment, such as transformers and shunt reactors etc. Air-to-Gas – used in gas insulated substations (GIS) and SF6 circuit breakers. Air-to-Air – used for outdoor to indoor connections e.g. wall bushings. 15/02/2024 Transformer Bushings 8

9. Bushing: Design Requirements Central conductor (material and physical parameters): To carry rated current/fault currents. Internal insulation: Electric fields, partial discharges. External insulation: dry arcing distance, creepage distance (leakage distance). Cantilever strength: To withstand mechanical stresses during the events of seismic and short circuit events. Robustness: To withstand the stresses of transportation and installation. 15/02/2024 Transformer Bushings 9

10. Bushing: Components/ features 15/02/2024 Transformer Bushings 10 Courtesy: SAVREE

11. Bushing: Solid and Capacitance-graded 15/02/2024 Transformer Bushings 11

12. Bushing: Capacitance-graded 15/02/2024 Transformer Bushings 12 Courtesy: SAVREE

13. Bushing: Solid and Capacitance-graded 15/02/2024 Transformer Bushings 13 Modeling the OIP Bushing as a set of Capacitive Layers Courtesy: NETA World Journal

14. Bushing: Solid and Capacitance-graded 15/02/2024 Transformer Bushings 14 Courtesy: Yash High Voltage Ltd.

15. OIP & RIP/RIS/RIF Bushings 15/02/2024 Transformer Bushings 15

16. RIP Bushing 15/02/2024 Transformer Bushings 16

17. Bushings: Cores 15/02/2024 Transformer Bushings 17 SRBP: Synthetic Resin Bonded Paper OIP: Oil-impregnated Paper RIP: Resin-impregnated Paper RIS: Resin-impregnated synthetic

18. Bushings: Comparative Analysis Insulation Oil Impregnated Paper Resin Impregnated Paper Resin Impregnated Synthetics Resin Impregnated Fiberglass Air End Insulator Porcelain is popular & Composite Insulator becoming popular Direct Moulded Silicon Insulator or Hollow Composite Insulator Direct Moulded Silicon Insulator or Hollow Composite Insulator Direct Moulded Silicon Insulator Oil End Insulator Porcelain / Epoxy No Separate Insulator (RIP Core) No Separate Insulator (RIS Core) No Separate Insulator (RIF Core) Temperature 105 °C 120 °C 120 °C 130 °C Storage De-Impregnation Moisture Absorption by Oil End of RIP Core (Use of Oil Filled Storage Tank) No Issues reported till date. No Issues reported till date Tan Delta at 30 °C 0.003 ~ 0.004 0.004 ~ 0.005 0.004 ~ 0.005 < 0.005 15/02/2024 Transformer Bushings 18

19. Bushings: Test Standards IEC 60137: 2017 IEEE c57.19.01 CAN CSA C88.1 15/02/2024 Transformer Bushings 19

20. Bushings: Tests Type Tests Routine Tests To prove the design expectations and consumer’s specifications and confirms design criteria. To confirm the operational performance of the design. performed on a prototype unit manufactured. Performed on every units manufactured. 15/02/2024 Transformer Bushings 20 Special Tests performed depending upon customer’s requirements to gathering the information which is useful during the operation and maintenance of the device.

21. Bushings: Type Tests Type Tests Dry or wet power-frequency voltage withstand test Temperature rise test Long duration power-frequency voltage withstand test Verification of thermal short-time current withstand Dry lightning impulse voltage withstand test Cantilever load withstand test Dry/wet switching impulse voltage withstand test Tightness test on liquid-filled bushings Thermal stability test Verification of dimensions Electromagnetic compatibility test 15/02/2024 Transformer Bushings 21

22. Bushings: Routine Tests Routine Tests Dielectric dissipation factor and capacitance at ambient temperature Tests on tap insulation Dry lighting impulse voltage withstand test Tightness test on liquid-filled bushings Dry power-frequency voltage withstand test Tightness test at the flange or other fixing device Measurement of partial discharge quantity Visual inspection and dimensional check 15/02/2024 Transformer Bushings 22

23. Bushings: Special Tests Special Tests Seismic test Switching impulse test for voltage classes not included as routine or type test Artificial pollution test for porcelain insulators 15/02/2024 Transformer Bushings 23

24. Bushing: Condition Assessment Capacitance Dissipation loss factor (tan δ) Insulation resistance test Partial discharge measurements Thermographic inspections Visual inspections 15/02/2024 Transformer Bushings 24

25. Bushings: New Developments 2019-2020: Synthetic Ester Impregnated Paper Bushing (EIP) launched by Siemens (Trench). Development in Progress Synthetic Ester Impregnated Synthetics (EIS) Mixed Dielectric (Synthetic Film + Non Woven Fabric) Use of Synthetic Film to increase Operating Temperature. Expect exploration & developments towards use of “New BIO Based Alternative Oil from Nynas ” which is neither a Mineral Oil or Ester Oil. 15/02/2024 Transformer Bushings 25

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