Differential magnetometer method applied to measurement of geomagnetically induced currents in Southern African power networks

02 Jun 2017

Geomagnetically induced currents (GICs) in conductors connected to the Earth are drivenby an electric ?eld produced by a time-varying magnetic ?eld linked to magnetospheric-ionosphericcurrent perturbations during geomagnetic storms. The GIC measurements are traditionally done on theneutral-to-ground connections of power transformers. A method of inferring the characteristics of GIC inpower lines using di?erential magnetic ?eld measurements is presented. Measurements of the GIC in thepower lines connected to a particular power transformer are valuable in the veri?cation of the modelingof GIC in the power transmission network. The di?erential magnetometer method (DMM) is an indirectmethod used to estimate the GIC in a power line. With the DMM, low-frequency GIC in the power line isestimated from the di?erence between magnetic ?eld recordings made direc tly underneath the power lineand at some distance away, where the magnetic ?eld of the GIC in the transmission line has negligible e?ect.Results of the ?rst application of the DMM to t wo selected sites of the Southern African power transmissionnetwork are presented. The results show that good quality GIC measurements are achieved through theDMM using Commercially- O?-The-Shelf magnetometers.