Differential magnetometer method applied to measurement of geomagnetically induced currents in Southern African power networks
Cilliers, Pierre J.
Van Zyl, Robert R.
Oyedokun, David T.
de Villiers, Jean
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Geomagnetically induced currents (GICs) in conductors connected to the Earth are driven by an electric field produced by a time-varying magnetic field linked to magnetospheric-ionospheric current perturbations during geomagnetic storms. The GIC measurements are traditionally done on the neutral-to-ground connections of power transformers. A method of inferring the characteristics of GIC in power lines using differential magnetic field measurements is presented. Measurements of the GIC in the power lines connected to a particular power transformer are valuable in the verification of the modeling of GIC in the power transmission network. The differential magnetometer method (DMM) is an indirect method used to estimate the GIC in a power line. With the DMM, low-frequency GIC in the power line is estimated from the difference between magnetic field recordings made directly underneath the power line and at some distance away, where the magnetic field of the GIC in the transmission line has negligible effect. Results of the first application of the DMM to two selected sites of the Southern African power transmission network are presented. The results show that good quality GIC measurements are achieved through the DMM using Commercially-Off-The-Shelf magnetometers.
Additional Citation InformationMatandirotya, E., P. J. Cilliers, R.R. Van Zyl, D.T. Oyedokun, and J.deVilliers (2016), Differential magnetome-ter method applied to measurement of geomagnetically induced currents in Southern African power networks, Space Weather, 14, 221–232,doi:10.1002/2015SW001289
SponsorThe Hermanus Kindex data used for Figure 1 are available at South African National Space Agency (SANSA) upon request. The measured magnetic field data used for Figures 5 and 9 will be provided to interested persons by the authors upon email request.The GIC data were obtained from the South African power utility, ESKOM. Interested persons could contact the authors for details of the current contact person at ESKOM. Some results presented in Figures 5and 9 rely on the data collected at the TSU and HER observatories. We thank SANSA for supporting their operation and INTERMAGNET for promoting high standards of magnetic observatory practice (www.intermagnet.org). This research is supported by a grant from SANSA. The authors wish to thank NamPower management for allowing data collection at the Namibian Network facilities and ESKOM for providing the GIC data from Bacchus substation. The technical support offered by the SANSA, Engineering and Data Acquisition (EDA) unit for the instrument installation and data acquisition at the measurement sites is greatly appreciated. We also appreciate the contribution of Magneum Simon and C. T. Gaunt to the discussions on this paper
Geomagnetically induced currents (GICs)
differential magnetometer method (DMM)
time-varying magnetic field