Reivindicaciones

1. - System of currents for compensating the magnetic field produced by electrically driven trains, characterised in that the return current for the power supply catenary is rerouted away from the tracks using alternative return conductors. 2. -System of currents for compensating the magnetic field produced by electrically driven trains, according to the previous claim, characterised in that one of the main power catenary current return cables is parallel and close to the catenary itself but carries current in the opposite direction to said catenary. 3. - System of currents for compensating the magnetic field produced by electrically driven trains, according to previous claim, by which the return conductors which reroute the current on the tracks to the return conductor of claim 1 are in a plane perpendicular to the plane of the tracks and parallel to the section of the tunnel. 4. - System of currents for compensating the magnetic field produced by electrically driven trains, as claimed in claim 3, in which the vertical return current comprises two circular arc-shaped conductors. 5. -System of currents for compensating the magnetic field produced by electrically driven trains, according to previous claims, characterised in that the sum of the currents in the return conductors of claim 2 is equal to that of the catenary. 6. - System of currents for compensating the magnetic field produced by electrically driven trains, according to previous claims, in which the track is provided with several cuts in order to electrically insulate each segment of a given length. 7. - System of currents for compensating the magnetic field produced by electrically driven trains, as claimed in claim 6, characterised in that the sections made in the track allow to install as many vertical return conductors as required to minimise the cross section of the substation-catenary-track-engine circuit. 8. - System of currents for compensating the magnetic field produced by electrically driven trains, as claimed in claim 6, by which the sections provided in the track allow to 8 install as many vertical return conductors as required to obtain return currents parallel to the catenary with the required approximation. 9. - System of currents for compensating the magnetic field according to previous claims, in which in a manner symmetrical and fully equivalent to that described above, the catenary is cut into segments and current is taken to each segment by vertical conductors connected to a power line placed at track level. 10. - System of currents for compensating the magnetic field produced by electrically driven trains, according to previous claims, by which the fluctuations of the magnetic field caused by fluctuations in the catenary current are compensated at origin.