Methods, device and installation for locating a defect in an electric link

1. A method for locating a defect in an electric link, comprising:

measuring a magnitude of at least one scalar component of a vectorial electromagnetic field in a vicinity of an estimated location of the defect at plural places along the link;

deducing, via a processor, from the measuring, an estimation of variation of the magnitude of the at least one scalar component of the vectorial electromagnetic field along the electric link in the vicinity of the estimated location of the defect; and

estimating, via the processor, a new estimated location of the defect as a function of the estimated variation of the magnitude of the at least one scalar component of the vectorial electromagnetic field, wherein:

the measuring includes measuring, by a system with three mutually orthogonal coils, a complete module of the vectorial electromagnetic field in the vicinity of the estimated location of the defect at the plural places along the link;

the deducing includes deducing, via the processor, from the measuring, the estimation of the variation of the complete module of the vectorial electromagnetic field along the electric link in the vicinity of the estimated location of the defect; and

the estimating includes estimating, via the processor, the new estimated location of the defect as a function of detection of an inflexion point in the estimated variation of the complete module of the vectorial electromagnetic field along the link.

2. The method for locating a defect in an electric link as claimed in claim 1 , wherein the measurements, at the plural places along the link, of the magnitude of the at least one scalar component of the vectorial electromagnetic field, are carried out along a path including successive transversal passages directly above the link.

3. The method for locating a defect in an electric link as claimed in claim 2 , wherein the path that includes successive transversal passages directly above the link follows a boustrophedon course.

4. The method for locating a defect in an electric link as claimed in claim 2 , wherein the vectorial electromagnetic field is generated by a flow in the electric link of a current of predetermined frequency, and wherein the measured magnitude of the at least one scalar component of the vectorial electromagnetic field is filtered by a band-pass filtering system regulated around the predetermined frequency of the current.

5. The method for locating a defect in an electric link as claimed in claim 1 , further comprising, prior to the measuring, the deducing and the estimating:

transmitting, at a first moment, an electric signal having a predetermined propagation speed at a start from an end of the electric link;

detecting, at a second moment, reception of an echo of the electric signal;

establishing a model of variation of the electric signal and its echo propagation speed in the electric link as a function of a length of electric link through which the transmitted electric signal and its echo have flowed; and

defining the estimated location of the defect as a function of the difference between the first and second moments, of the predetermined propagation speed at the start, and of the speed variation model in the link,

wherein the model includes a plurality of propagation speeds of the transmitted electric signal and its echo, the plurality of propagation speeds corresponding to a plurality of lengths of the electric link through which the transmitted electric signal and its echo have flowed, and the plurality of lengths of the electric link including lengths of the electric link shorter than a total length of the electric link.

6. A device for locating a defect in an electric link, comprising:

a measuring device for measuring a magnitude of at least one scalar component of a vectorial electromagnetic field in a vicinity of an estimated location of the defect at plural places along the link; and

a processor which deduces from the measuring output from the measuring device an estimation of variation of the magnitude of the at least one scalar component of the vectorial electromagnetic field along the electric link in the vicinity of the estimated location of the defect; and which estimates a new estimated location of the defect as a function of the estimated variation of the magnitude of the at least one scalar component of the vectorial electromagnetic field,

wherein the measuring device includes three mutually orthogonal coils for measuring three orthogonal components of the vectorial electromagnetic field, and wherein the processor is programmed for estimating the variation of at least one part of the three orthogonal components of the vectorial electromagnetic field along the link and estimating the new estimated location of the defect as a function of the estimated variation of at least one part of the three orthogonal components of the vectorial electromagnetic field.