Device for measuring AC in a high tension line

A device for measuring alternating current flowing in a high tension line, comprising two fibre optic systems for conveying two light signals representative of the current flowing in the line to a point distant from the line;

• shunt means adjacent the line for providing an electric signal substantially proportional to the current flowing in the line, the direction of the electric signal corresponding to the direction of the said current;
• diode bridge means adjacent the line comprising at least two diodes fed by the said electric signal and so connected that one or other of the diodes is conductive according to the direction of the electric signal, each of the two diodes being electroluminescent and being arranged to supply a light flux when conductive representative of the value of the electric signal;
• the two said fibre optic systems receiving respective light fluxes from the two said electroluminescent diodes and conveying the fluxes to a point distant from the line;
• two light receptors at a distance from the line receiving the fluxes conveyed by the two said fibre optic systems such that each receptor, on receiving light, supplies a half-wave signal representative of the light flux;
• a differential circuit at a distance from the line receiving the two said half-wave signals and supplying an output signal of one polarity or the other according to whether it is receiving the half-wave signal from one or the other of the two said receptors, the amplitude of the output signal being representative of the amplitude of these half-wave signals;
• and
• a measuring unit receiving the said output signal.