AC current sensor for measuring electric AC current in a conductor and an indicator system comprising such a sensor

摘要

The invention concerns a current sensor (22; 24; 26) for substantially in real time measuring electric current in a conductor. It is suitable for application in an indicator system (1) such as a short circuit indicator system for measuring instantaneous i.e. live current value, power, reactive power, phase angle, polarity, short circuits, in single or averaged values. It comprises current responsive means comprising a current transformer (2210), adapted for mounting adjacent to said electric conductor; and sensor circuitry (2220) comprising means for emitting a non-electrical wave signal as an output; said sensor circuitry (2220) comprises current level converter circuitry (2222) comprising a current-to-frequency converter adapted to provide said non-electrical wave signal as a current level indication pulse signal (CS₁) having a pulse frequency (Pf_cs) which is proportional to said real time electric conductor current, when the latter is within a predetermined current interval (I₁-I₂). Thus, a low cost sensor is provided. The invention further relates to an indicator system (1) for an electric conductor comprising at least one of the above mentioned current sensors (22; 24; 26).