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1. KIPM COLLEGE OF
ENGINEERING & TECHNOLOGY
PRESENTED BY SUBMITTED TO
UJJWAL PRATAP RANA Er. ALOK KUMAR
YADAV sir
ROLL NO. 1575120053
rd

2. TO BE DISCUSS
INTRODUCTION
PRINCIPLE
BLOCK DIAGRAM
MATHEMATICAL EXPRESSION
PARTS OF MOCT
DESIGN
MAGNETO OPTICAL SENSOR
APPLICATION
ADVANTAGES
DISADVANTAGES
CONCLUSION
REFERENCES

3. •Magneto optical current transformer
is an instrument transformer ,using
the angle of rotation of linearly
polarized light to measure the current.
•It fulfills the two purposes-metering
and relaying.
fig 1:MOCT

4. MOCT
MOCT Measures the electric current by means of FARADAY
EFFECT.
FARADAY EFFECT:
“Michael Faraday
discovered that the orientation of
linearly polarized light was rotated
under the influence of the magnetic field
when the light propagated in a piece of
glass, and the rotation angle was
proportional to the intensity of the
magnetic field. “

5. fig 2: plane polarizer fig 3: crossed polarizer
fig 4: analyzing of plane polarised light
Polarization is a property of certain types of waves that
describes the orientation of their oscillations.

6. MOCT -PRINCIPLE
Fig 5: vertically polarised light
MOCT is based on the Faradays effect-the orientation
of linearly polarized light was rotated under the
influence of the magnetic field when the light
propagated in a piece of glass, and the rotation angle
was proportional to the intensity of the magnetic field .

7. Fig 6: rotation of polarised light under influence of magnetic field

9. MATHEMATICAL
EXPRESSION
Generally, this phenomenon can be described as
follows:
θ = v ʃ B.dl .Eq. (1)
‘θ’ is the Faraday rotation angle,
‘V’ is the constant of magneto-optical material,
‘B’ is the magnetic flux density along the optical path,
‘l’ is the optical path.

10. Eq. (1),can be rewritten according to Ampere’s law as:
θ = nµVI …… Eq. (2)
‘I ‘is the current to be measured,
‘µ’ is the permeability of the material,
‘n’ is the number of turns of the optical path.

11. Fig 7 : polarised light
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.

13. DESIGN
•The optical sensor consists of two
separate clamp-on parts and linearly
polarized light is arranged to pass
through the optical glass prism
to pickup the Faraday rotation signal.
Fig 9:photo of MOCT
•The MOCT polarization compensation
technique is applied at each corner of
the prisms, so that the light passing
through the prism remains linearly
polarized.

14. Fig 11: arrangement of system

15. Fig 12: (a) Fig 12: (b)
The rotation angles from the two halves of the sensor
[Fig 12.(a)] are added up in the signal processing unit so
that the total rotation angle (θ1+θ2 ) is the same as the
rotation angle θ from the optical path shown in
Fig 12.(b), which is two turns around the conductor.

16. MAGNETO-OPTICAL
SENSOR
Almost all transparent material exhibits the magneto-
optical 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.
the total internal rotation angle is ≈ θ1+ θ2 ≈ 2µVI
.

17. I : current to be measured,
µ = 4π x 10-7 H/m
V=7.7 x 102 degrees/Tm at a
wavelength of 820nm.
Therefore θ = 1.9 degrees/ KA.
Another material used as a glass fig 13:optical sensor
ring sensor is SF6 due to its relatively
high co-efficient and low temperature dependency.
Sometime it calls SCHOTT SF6 , contains.
SiO2-27%, PbO2-71%, K2O-1%, Na2O-0.5% and
As2O3-0.3%.

18. 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.
fig 14:substation using MOCT

19. ADVANTAGES
 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.
 Wide frequency response and larger dynamic
range.
 Low voltage outputs which are compatible with the
inputs of digital to analog converters.

20. DISADVANTAGES
 Temperature and stress induced linear
birefringence in the sensing material causes error
and instability in some cases.
 The accuracy of MOCT is slightly less for use in
power systems in large extent .

21. 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 .

22. REFERENCES
[1].From IEEE journals paper.
[2].Electromagnetic field Theory book.
[3]. Electric machines book.
[4]. Asfaq Hussain book.
[6]. Fibre optics book.