Geomagnetically Induced Currents and Space Weather Prediction in Austria Space Weather Prediction GIC Simulation and Measurement GIC Simulation Electric field calculation

Abstract

Unusually high transformer sound levels triggered the GIC research in Austria. The measurements revealed DC currents highly correlated with geomagnetic field variations. There are currently 9 self developed measurement systems running in different transformer neutral points in Austria. In order to investigate the transformer behaviour under GIC bias, transformer laboratory tests and simulation models were set up. The developed GIC-grid-simulation tool calculates the currents in the power grid from the measured magnetic field data. The calculation is based on an earth subsurface conductivity model combined with a model of the electrical transmission grid. The comparison between continuous measurements and simulations results in constantly improved calculation methods. We wish to provide forecasts of future GICs using the incoming solar wind measured at the Earth-Sun Lagrange point 1 (L1) as a basis. We aim to predict the two horizontal geoelectric field components, Ex and Ey, with the ground truth being the geoelectric field modelled from geomagnetic variations. The forecasting is carried out using a recurrent neural network (LSTM), which takes solar wind speed, density and magnetic field, as well as recent geomagnetic variations, as input and then outputs the maximum expected geoelectric field in the next 30-40 minutes, assumed to be homogenous across Austria. The fit of simulation to measurement will be shown with recent solar events of 2021.

Full text

Philipp Schachinger1, Dennis Albert1, Rachel L. Bailey2,
1Institute of Electrical Power Systems, Graz University of Technology; 2Zentralanstalt für Meterologie und Geodynamik Austria
rachel.bailey@zamg.ac.at philipp.schachinger@tugraz.at
dennis.albert@tugraz.at
380 kV
220 kV
Substation
Grid Node
GIC Measurement
DCC Measurement #5
#3
#8
#7
#1,4
#2
Status: 2021-12-07
#6
#9
Geomagnetically Induced Currents and
Space Weather Prediction in Austria
Space Weather Prediction GIC Simulation and Measurement
GIC Simulation
Freeware tool LFC-Simulator (see QR code)
Electric field calculation
The electric field for the GIC calculation is either preset or calculated with the
plane wave
method and
1-D earth conductivity models
.
Power grid calculation
For the calculation of the GICs, we use the
nodal analysis
. In combination
with transformer models, reactive power consumption and power quality are
calculated and analyzed.
Current Work
Developing a forecasting model using machine learning (recurrent neural
networks)
Data:
26 years of data from 1995 till 2021
OMNI solar wind (back-propagated to the Lagrange-1 point)
Regional geoelectric field modelled from local geomagnetic variations
using the plane wave approach and a subsurface resistivity layer
model (validated against measured GICs in transformers after putting
the geoelectric field through a model of the power network).
Input: Solar wind data from the Lagrange-1 point with 2-hour history
(orange in plot)
Output: maximum expected geoelectric field in the next 30-min following
a minimum of ~20-min solar wind expansion time to Earth (red in plot).
The field is for the region of Austria, assumed to be homogenous due to
the small size of the country.
Forecasting model:
LSTM (Long Short-Term Memory recurrent neural network)
One model for Ex, one for Eycombine to forecast GICs at
individual stations!
Case Study: GMD May 12th 2021
•simulated and measured GIC for client #01 with peak current of -8 A
•max. measured current in client #05 was -13.8 A
Mitigation during GMD May 12th 2021
DC flux compensation system installed in multiple transformers
client #07 measured GIC and compensating current of system
each phase/wounded limb has its own compensation winding
Calculating per phase GIC and total GIC in transformer neutral
𝐼DC,phase =𝑛CW
𝑛HV
⋅ 𝐼comp
𝑛CW number of turns of compensation winding
𝐼comp primary current of compensation system
𝑛HV number of turns of high-voltage winding
Austria - Some Statistics
Population: 8.9 million
Size: 84 000 km2(600 km wide)
Neighbouring countries: Switzerland,
Germany, Czechia, Slovakia, Hungary,
Slovenia, Italy, Liechtenstein (8)
Geomagnetic latitude: 46°
Power Grid Operator: Austrian Power
Grid (APG)
No. of HV substations: 65
No. of GIC measurement devices: 9
An Austrian national space weather portal showing current space weather conditions
and detailing national research into space weather is currently under development!
Check back here in the next weeks to see the launch: https://cobs.zamg.ac.at
Bailey, R. L., Leonhardt, R.,
Möstl, C., Beggan, C., Reiss, M.
A., Bhaskar, A., & Weiss, A. J.
(2022). Forecasting GICs and
geoelectric fields from solar wind
data using LSTMs: Application in
Austria. Space Weather, 20,
e2021SW002907.
https://doi.org/10.1029/2021SW00
2907