Differential Magnetometer Measurements of Geomagnetically Induced Currents in a Complex High Voltage Network

Space weather poses a hazard to grounded electrical infrastructure such as high voltage (HV) transformers, through the induction of geomagnetically induced currents (GICs). Modeling GICs requires knowledge of the source magnetic field and the Earth's electrical conductivity structure, in order...

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Bibliographic Details
Published in:Space Weather 2020-04, Vol.18 (4), p.n/a
Main Authors: Hübert, J., Beggan, C. D., Richardson, G. S., Martyn, T., Thomson, A. W. P.
Format: Article
Language:English
Subjects:
Amplitudes
Complex HV network
Correlation analysis
Differential Magnetometer Method
Earth
Electric currents
Electric fields
Electrical conductivity
Electrical grounding
Electrical resistivity
Electrical transmission
Electromagnetism
Geoelectric fields
Geoelectricity
Geomagnetic storms
Geomagnetically Induced Currents
Geomagnetism
Hall effect
Hall probes
High voltage
High voltages
Magnetic fields
Magnetic storms
Magnetometers
Measuring instruments
Network topologies
Space weather
Storms
Substations
Tensors
Topology
Transformers
Weather
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Summary:Space weather poses a hazard to grounded electrical infrastructure such as high voltage (HV) transformers, through the induction of geomagnetically induced currents (GICs). Modeling GICs requires knowledge of the source magnetic field and the Earth's electrical conductivity structure, in order to calculate the geoelectric fields generated during magnetic storms, as well as knowledge of the topology of the HV network. Direct measurement of GICs at the ground neutral in substations is possible with a Hall effect probe, but such data are not widely available. To validate our HV network model, we use the differential magnetometer method (DMM) to measure GICs in the 400 kV grid of Great Britain. We present DMM measurements for the 26 August 2018 storm at a site in eastern Scotland with up to 20 A recorded. The line GIC correlates well with Hall probe measurements at a local transformer, though they differ in amplitude by an order of magnitude (a maximum of ∼2 A). We deployed a long‐period magnetotelluric (MT) instrument to derive the local impedance tensor which can be used to predict the geoelectric field from the recorded magnetic field. Using the MT‐derived electric field estimates, we model GICs within the network, accounting for the difference in magnitude between the DMM‐measured line currents and earth currents at the local substation. We find that the measured line and earth GICs match the expected GICs from our network model, confirming that detailed knowledge of the complex network topology and its resistance parameters is essential for accurately computing GICs. Plain Language Summary Large geomagnetic storms create time‐varying magnetic fields, which induce secondary electric fields in the conductive Earth resulting in geomagnetically induced currents (GICs). The high voltage (HV) power transmission network is connected to the Earth at grounding points in substations. These offer a low‐resistance path for GICs to flow into the power network, potentially causing the transformers to malfunction. It is possible to directly measure GICs at substations using Hall effect probes, but due to cost and operational reasons, at present only four substations in the United Kingdom are monitored. Therefore, we have developed a new instrument to measure GICs indirectly using two magnetometers, one placed under the HV line and another a few hundred meters away. By examining the differences between the magnetometers, we work out the additional current flowing in the
ISSN:1542-7390
1539-4964
1542-7390
DOI:10.1029/2019SW002421