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Fiber optic sensors for transformers

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Fibre Optic Sensors for Transformers- Recent technology

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Fiber optic sensors for transformers

  1. 1. Fiber Optic Sensors for Transformers Guided by: Mrs. Amruta Deshpande
  2. 2. Contents:  Introduction  Negligence of FO Sensors  Advantages of FO Sensors  Recent development to measure Hot spot temperature.  Construction.  Operating Principle.  FO Probe Installation.
  3. 3. Introduction:  Transformer loading capacity is limited by winding temperature which is not uniform.  Winding Hotspot temperature.  Conventional methods for measurement.  Assumptions in conventional methods.
  4. 4. Negligence of FO Sensor:  Fragile- High percentage of fiber failures due to breakage in industry.  Cost- high initial cost compared to a conventional product
  5. 5. Advantages of FO Sensors:  Reliable and do not cause delay during emergency overloading.  Require less maintenance.
  6. 6. Recent Development:  Robust fiber optic sensors have been constructed.  FO probe- 200 micron optical fiber with a permeable protective PTFE sheath.  Based on GaAs technology
  7. 7. Operating Principle of FO Sensor  Based on variation in absorption spectrum of GaAs with respect to temperature  White light is incident on the crystal.  Depending on temperature light is more or less absorbed and the less is reflected by a mirror.  Reflected light is analyzed electronically.
  8. 8. Typical specifications/Characteristics:           Temperature range: −40°C to 225°C Resolution: 0.1°C Accuracy : 2°C Available sensor length: 1 to 15 meters Fiber type: 200 μm silica fiber Cable sheathing: Double PTFE sheathing (spiral wrap) Sensor dimensions: 1.5 mm O.D. resilient construction. resistance to chemicals completely immune to EMI and RFI environments
  9. 9. FO Probe Installation  Sensor can be embedded in a spacer or attached directly to a conductor whose temperature is to be measured.  Or it can be inserted in the spacer between successive disks(a slot is cut in the spacer and glued)  The 2nd method avoids breaking and restoring the conductor insulation
  10. 10. Installation continued…  Installation of FO Probe and its handling during manufacturing are challenging to avoid sharp bends.  This may break the fiber.  An improvement is a simplified through-wall connection.
  11. 11. This optical feed has a simple design, provides low loss optical Connection and leak free operation. With this, survival rate of FO sensors is better than 90%.
  12. 12. Practical installation:
  13. 13. Conclusion:  Hot spot measurement with fiber optic sensors is now being accepted by many utilities and there are some drastic improvements in their design and construction.  It is most likely fiber optic sensors will be used for transformer cooling, loading etc., considering less maintenance, fast response and accuracy.
  14. 14. Future Scope:  With more and more development in FO technology, cost of FO temperature monitoring systems can be fraction of 1% of the cost associated with power transformer.  Long term benefits can be achieved.
  15. 15. References:     Nasser a. Al-Qahtany*, Krishnan s. Balasubramanian, “Optic Fiber Sensors for transformer winding hot-spot measurement - Saudi electricity company specification” national grid SA – Saudi electricity company, standards & specifications department. Sheldon p. Kennedy, Thomas Gordner, “Hot spot studies for sheet wound transformer windings” Doble engineering company – 80th international conference of Doble clients. Tpt-32 temperature sensor for oil-filled Transformers-PDF Andersen, O.W. “Finite element solution of skin effect and eddy current problems” IEEE paper A77 616-6, Mexico City, July 1977

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