MAGNETO OPTICAL CURRENT TRANSFORMER Presented By: Shivankit Bansal Final Year Electrical Deptt.

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

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

A TYPICAL MOCT

MOCT SYSTEM CONFIGURATION

What is it? Passive optical current transducer which uses light to accurately measure current on high voltage systems. Passive optical current transducer which uses light to accurately measure current on high voltage systems. Measures current by means of Faraday’s Effect. Measures current by means of Faraday’s Effect. Determines the rotation angle & converts into a signal of few volts proportional to the current. Determines the rotation angle & converts into a signal of few volts proportional to the current.

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

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

MOCT PRINCIPLE:

Contd.

A polarizer is used to convert the randomly polarized incident light into linearly polarized light. 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. 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. Analyzer converts the orientation variation of polarized light into intensity variation with two outputs. The outputs are send to photo detectors. The outputs are send to photo detectors.

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

Electronic Circuit for MOCT

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

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

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

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 Faraday’s 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.

THANK YOU