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Abstract

A fault detector for an electrical transmission system and a remote current sensor for use therein. The remote current sensor includes a Hall effect transducer for measuring the magnetic field surrounding a conductor of the transmission system to thereby monitor the current flowing through the conductor. The transducer is positioned between a pair of tapered pole pieces for concentrating low density magnetic flux in the air into a high density magnetic flux focused onto the transducer. The pole pieces enable the sensor to be positioned a distance from the conductor which is greater than the electrical arcing distance so as to allow use of the air gap between the conductor and sensor as insulation. For a triangular configuration of conductors, two remote current sensors having orthogonal sensitive axes are positioned at a location equidistant from all three conductors. A first sensor measures only the magnetic field surrounding a first conductor whereas the second sensor measures the vector sum of the magnetic fields surrounding the second and third conductors. For a coplanar configuration of conductors, three remote current sensors are utilized. Each sensor is positioned radially outward from its associated conductor, the sensitive axis of each sensor being tangent to the magnetic field surrounding its conductor. The fault detector compares the highest positive sensor output and the least positive sensor output to respective set points enabling the detection of a fault within one quarter of a fault current cycle. If either set point is exceeded, a relay is actuated to provide a fault indication signal.

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First Claim