Detector of abrupt current variations on power lines

A system to detect abrupt current variations occurring on high-powered conductors ( > 10 A) is proposed. The detection system is composed of an inductive transducer interfaced by a saw-tooth current-controlled oscillator (CCO). The transducer consists of a spiral highpass inductor, the role of which is to catch the magnetic flux induced by the current generated on the power line, the sensor being connected to the source branch of the CCO control current. Each magnetic perturbation is therefore transformed into an induced current added to the CCO source current, thus deforming the output transient saw-tooth voltage of the circuit. The authors have defined an output characteristic based on the measurement of each period of the oscillating voltage; the information is consequently extracted from the comparison of the measured periods with the natural oscillating period of the CCO. The system has been implemented on a printed circuit board, tested for the arc fault detection application and compared with a Hall reference probe. The proposed measuring method allowed discriminating the arcing occurrences from the normal operation of the power conductors in three different regimes: i.e. when the power line is loaded by an open circuit, a resistive load, or an electrical motor.