Seminars for Electrical Engineering - 2014
An accurate current transducer is a key component of any power system instrumentation. To measure currents, power stations and substations conventionally employ inductive type current transformers. With short circuit capabilities of power system getting larger and the voltage level going higher the conventional current transformers becomes more bulky and costly also the saturation of the iron core under fault current and the low frequency response make it difficult to obtain accurate current signals under power system transient conditions. In addition to the concerns, with the computer control techniques and digital protection devices being introduced into power systems, the conventional current transformers have caused further difficulties, as they are likely to introduce electro-magnetic interference through the ground loop into the digital systems.
Magneto-Optical Current Transformer (MOCT) is a completely new generation of the instrument transformer developed since 1980s. It appears that MOCT is a good solution for many of the problems by the conventional current transformers. It is a high tech product which involves optics, optical materials, optical fibre communication, electromagnetism, electronics and computer technology. MOCT measures the rotation angle of the plane polarized lights caused by the magnetic field around the current carrying conductor and convert it into a signal of few volts proportional to the magnetic field. Main advantage of an MOCT is that there is no need to break the conductor to enclose the optical path in the current carrying circuit and there is no electromagnetic interference.