SWP Power Grid & Ground-Based Infrastructure Impacts 1 — Questions and Answers
Question 1: Geomagnetically induced currents (GICs) in power grids are caused by:
- Lightning discharges from auroral precipitation
- Rapid changes in Earth's magnetic field inducing electric fields that drive currents in long conductors (Correct answer)
- Solar radio burst interference in grid monitoring electronics
- Direct solar wind particle impacts on transmission lines
Correct answer: Rapid changes in Earth's magnetic field inducing electric fields that drive currents in long conductors
According to Faraday's law, time-varying geomagnetic fields induce geo-electric fields at Earth's surface that drive quasi-DC GICs through grounded transmission networks.
Question 2: The March 1989 geomagnetic storm famously caused:
- Destruction of GOES-7 satellite
- Collapse of the Hydro-Québec power grid in approximately 92 seconds (Correct answer)
- Failure of all North American HF radio for 12 hours
- Disruption of the Apollo program lunar communications
Correct answer: Collapse of the Hydro-Québec power grid in approximately 92 seconds
GICs triggered protective relay operations in a cascading sequence that blacked out the entire Hydro-Québec network in under two minutes, leaving 6 million people without power for up to 9 hours.
Question 3: High-voltage power transformers are particularly vulnerable to GICs because:
- Their insulation is weakened by magnetic fields
- Even small quasi-DC GICs can half-cycle saturate transformer cores, causing overheating and reactive power loss (Correct answer)
- GICs reverse the transformer winding polarity
- GICs increase AC resistance, tripping current overload protections
Correct answer: Even small quasi-DC GICs can half-cycle saturate transformer cores, causing overheating and reactive power loss
GIC as low as a few amperes can saturate the ferromagnetic transformer core during one half-cycle of AC, generating harmonics, excessive VAR consumption, and potentially damaging the equipment.
Question 4: Which geographic characteristic makes a region's power grid most susceptible to GIC damage?
- Tropical location with high humidity
- High latitude with resistive igneous bedrock and long transmission lines (Correct answer)
- Proximity to ocean coastlines
- Dense urban load concentration
Correct answer: High latitude with resistive igneous bedrock and long transmission lines
High latitudes experience stronger geo-electric fields during storms, and resistive bedrock forces induced currents into metallic conductors; long transmission lines accumulate larger total GIC.
Question 5: The geoelectric field magnitude that drives GICs in surface conductors is most directly controlled by:
- Solar wind proton density
- The rate of change of the horizontal geomagnetic field (dB/dt) and ground conductivity structure (Correct answer)
- Dst index minimum value
- 10.7-cm solar flux
Correct answer: The rate of change of the horizontal geomagnetic field (dB/dt) and ground conductivity structure
The surface geoelectric field is proportional to dB/dt convolved with the local Earth conductivity structure; faster magnetic variations over resistive crust produce the largest fields.
Question 6: Pipeline operators monitor for GICs primarily because induced currents can:
- Reverse pipeline flow direction
- Accelerate electrochemical corrosion of metal pipelines by disrupting cathodic protection systems (Correct answer)
- Cause pipeline pressure increases
- Trigger gas ignition from static discharge
Correct answer: Accelerate electrochemical corrosion of metal pipelines by disrupting cathodic protection systems
GICs alter the cathodic protection potentials on buried pipelines, allowing electrochemical corrosion to proceed in regions where the protection current is overwhelmed or reversed.
SWP Power Grid & Ground-Based Infrastructure Impacts 1
Geomagnetically induced currents (GICs) in power grids are caused by: