Magneto optic current transformer


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magneto optic current transformer

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Magneto optic current transformer

  1. 1. The Seminar Topic is based On MAGNETO OPTICAL CURRENT TRANSFORMER Presented ByAishwarya Verma(0902011)
  2. 2. CONTENTS  Introduction  CT purpose and Demerits  MOCT- principle, design, working.  MOCT block diagram  Applications  Pros and Cons  Conclusion
  3. 3. INTRODUCTION  An accurate electric current transformer is a key component of any power system instrumentation.  The MOCT measures the electric current by means of Faraday Effect.  Conventional current transformers becomes more and more bulky and costly. MOCT View
  4. 4. CT Purpose and Demerits PURPOSE OF CT: It feeds the current coils of indicating, metering instruments and protective relays Watch over the current’s in the circuit DEMERITS OF CT: The insulation structure has to be designed carefully to avoid electrical field stress, which could eventually cause insulation breakdown. Less reliability
  5. 5. MOCT MOCT measures the electric current by means of FARADAYS EFFECT. Michael faraday discovered that the orientation of linearly polarized light was rotated under the influence of the magnetic field.
  6. 6. PRINCIPLE “ The light propagated in a piece of glass and the rotation angle was proportional to the intensity of the magnetic field”.
  7. 7. MOCT-Principle θ =nµVI ‘I ‘is the current to be measured, ‘µ’ is the permeability of the material, ‘n’ is the number of turns of the optical path.  The Faraday effect outlined in eqn is a better format to apply to an MOCT, because the rotation angle in this case is directly related to the enclosed electric current.  It rejects the magnetic field signals due to external currents which are normally quite strong in power system. 
  8. 8. P1 = (1 + Sin 2θ )P0/2 P2 = (1 - Sin 2θ )P0/2 P0 : optical power from the light source, θ : the Faraday rotation angle, P1 and P2 : optical power delivered by the detectors.
  9. 9. DESIGN 1. The optical sensor consists of two separate clamp-on parts. 2. Linearly polarized light is arranged to pass through the optical glass prism to pickup the Faraday rotation signal. 3. The polarization compensation technique is applied at each corner of the prisms
  10. 10. WORKING
  11. 11. MAGNETO-OPTICAL SENSOR Almost all transparent material exhibits the magnetooptical effect or Faraday Effect, but the effect of some of the material is very temperature dependent, and they are not suitable for the sensing material. MOCT made out of SF-57 materials can achieve higher sensitivity.
  13. 13. APPLICATION The MOCT is designed to operate in a transparent manner with modern electronic meters and digital relays, which have been adopted for a low energy analog signal interface. The design approach is to redefine the interface point as to input the analog to digital conversion function used by each of these measurement systems.
  14. 14. Pros and Cons PROS: No risk of fires and explosions. No need to use metallic wires to transfer the signal and so simpler insulation structure than conventional current transformer. High immunity to electromagnetic interference. CONS: Temperature and stress induced linear birefringence in the sensing material causes error and instability.
  15. 15. CONCLUSION This magneto optical current transformer eliminates many of the drawbacks of the conventional current transformers. In an conventional current transformers, there is a chance of saturation of magnetic field under high current, complicated insulation and cooling structure, a chance of electro magnetic interference .