Optical fibre interferometric electric current measuring device

A device for measuring at least one current circulating in a high voltage power distribution line using at least one interferometric measuring means, comprising:

• an optical fibre in which circulate two waves in opposite directions, the current to be measured inducing a first phase shift between the two waves emerging at the ends of the optical fibre by the Faraday effect;
• optoelectronic circuits connected to said optical fibre supplying an electric control signal proportional to this phase shift;
• and
• a reference current generator receiving said electric control signal and supplying a reference conductor circuit inducing by the Faraday effect a second phase shift between the two waves emerging at the ends of the optical fibre in the opposite direction to the first phase shift and, of amplitude such that the resulting phase shift is zero, the reference current value being directly proportional to the current to be measured;
• wherein the improvement comprises an apparatus for each current to be measured, where each apparatus comprises:
• a measuring head made from an insulating material and placed on a conductor through which the current to be measured flows;
• an element made from an insulating material and perforated by a connecting channel, one of the ends of said channel issuing into the measuring head;
• and
• an electrically grounded base incorporating said reference circuit and linked with the second end of the channel made in the insulating element:
• wherein the optical fibre of each interferometric measuring means is disposed in such a way as to form at least one closed loop describing a path starting in the base, traversing the channel in a first direction, forming a turn around the conductor within the measuring head, passing through the channel again in the opposite direction and returning to the base in order to form at least one turn around the reference conductor circuit.