MAGNETO OPTICAL CURRENT TRANSFORMER

1
MAGNETO OPTICAL CURRENT TRANSFORMER

• Presented By
• Shivankit Bansal
• 1207749
• Final Year
• Electrical Deptt.

2
Drawbacks of Current T/f

• The insulation structure has to be designed
  carefully to avoid breakdown.
• Electric current path of primary bus has to be
  designed properly to minimize the mechanical
  forces.
• Violent destructive failures.

3
ABSTRACT

• MOCT technology provides solution to many of the
  problems of conventional current transformer.
• Quite new technology-in research stage.
• Provides no Electromagnetic Interference.
• No need to break the conductor to enclose the
  optical path in the current carrying circuit.

4
A TYPICAL MOCT
5
MOCT SYSTEM CONFIGURATION
6
What is it?

• Passive optical current transducer which uses
  light to accurately measure current on high
  voltage systems.
• Measures current by means of Faradays Effect.
• Determines the rotation angle converts into a
  signal of few volts proportional to the current.

7
COMPONENTS

• Sensor head located near the current carrying
  conductor.
• An Electronic Signal Processing Unit.
• Fiber Optical Cables linking these two parts.

8

• The sensor head consists of optical components.
• The signal is brought down to signal processing
  unit by means optical fiber cables.
• Signal Processing Unit basically converts the
  optical signal into suitable electrical form.
• As no metallic wires are needed therefore it
  provides better insulation.

9
MOCT PRINCIPLE
10
Contd.
11

• A polarizer is used to convert the randomly
  polarized incident light into linearly polarized
  light.
• Orientation rotates an angle ? after the light
  has passed through the magneto-optical material
  because of Faraday Effect.
• Analyzer converts the orientation variation of
  polarized light into intensity variation with two
  outputs.
• The outputs are send to photo detectors.

12

• Proper wrapping of optical path around current
  carrying conductor is required.
• Can be achieved by folding the optical path by
  means of reflections.
• Total Internal Reflections Metal Reflections
  are good ways.
• Prisms should be designed to keep the light
  linearly polarized.
• Phase shift should be avoided.
• A program in FORTRAN is used for the performing
  the entire operation.

13
Electronic Circuit for MOCT
14
APPLICATIONS

• Most suited for outdoor type applications.
• It meets the protection class accuracy as
  specified by IEC 60004-8.
• The optical design enables accurate measurement
  of fault currents.
• Makes the output signal insensitive to shock
  vibration.

15
ADVANTAGES

• No risks of fires explosions.
• Simpler insulation structure.
• High immunity to Electromagnetic interferences.
• Wide frequency response.
• Larger Dynamic Range.
• Low voltage outputs-compatible with the inputs of
  digital to analog converters.

16
DISADVANTAGES

• Temperature and stress induced linear
  birefringence in the sensing material causes
  error and instability.
• The accuracy of MOCT is so far insufficient for
  the use in power systems.

17
CONCLUSION

• This magneto optical current transducer
  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 etc.
• By applying Faradays principle this transducer
  provides an easier and more accurate way of
  current measurement. This MOCT is widely used in
  power systems and substations nowadays. And a new
  trend is being introduced, which known as OCP
  based on adaptive theory, which make use of
  accuracy in the steady state of the conventional
  current transformer and the MOCT with no
  saturation under fault current transients.

18
THANK YOU