Resistivity Measurement and Inversion of the Current Path into the Ground for HVDC Transmission

HVDC transmission in the earth-return current has a large penetration depth which is difficult to measure the resistivity. A method for hybrid measurement and inversion of a wide range of resistivity of this path is proposed. A combined application of the four-point method and the magnetotelluric method is investigated which can measure the earth resistivity more effectively that covers the surface to the depth of hundreds of kilometers below the ground. In the inversion processing of measurement data, the paper puts forward an artificial bee colony global optimization inversion method embedded with local conjugate gradient search for the global optimization method. It is a more efficient hybrid inversion scheme.