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Comment by londons_explore | Hacker News Reader

> geomagnetically induced currents (GICs) could flow through electrical grids, potentially overheating transformers and causing them to fail.

yes, but such currents are typically measured in milliamps or, during the biggest storms, amps. Most utility scale transformers would be needing DC currents of the order of thousands or tens of thousands of amperes before failure.

Even then, overheat sensors would detect such a condition, and operationally the circuit could be de-energised and connected to earth to protect it.

Also, where there are perhaps thousands of transformers connected to a particular distribution grid, the load from the GIC's is shared amongst them, further reducing impact.

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I dunno. The American Geophysical Union seemed to think it was a BFD in one of their conferences back in the 2000s. Had a whole presentation about how certain parts of the US grid would lose large transformers that would likely take months to years to replace as there are few spares and they have to be wound with miles and miles of copper by hand. Said that large swaths of the US would be without grid power for very long periods.

Said that third world countries would fare pretty well though.

It sounds like they need some type of automatic or robotic winding system... Even without some catastrophe, they surely have to make new transformers from time to time, and winding miles of copper by hand sounds ridiculously inefficient for a manufacturing process.

Hand winding allows for a high degree of precision and quality control that may be difficult to achieve with automated machinery, particularly for specialized or custom designs. Skilled technicians can closely monitor the process and make adjustments on the fly to ensure that the winding is as precise as possible. This is crucial for large transformers, where even minor imperfections can lead to inefficiencies, increased heat, or failure.

Transformers for electrical grids can vary greatly in their specifications depending on a variety of factors, such as location, usage, and existing grid architecture. Customization is often necessary, and hand winding allows for this level of customization to meet specific criteria, including the number of windings, the type of core used, and other design elements.

Copper wire is both flexible and delicate. It needs to be handled carefully to avoid nicks, kinks, or other imperfections that can compromise the transformer’s performance. Human technicians can adapt to the nuances of the material more effectively than machinery in some cases, ensuring that the wire is handled with care throughout the winding process.

Geomagnetically Induced Currents (GICs) are often measured in amps rather than milliamps, and their values can vary significantly depending on the specifics of the geomagnetic storm and the electrical grid. During the 1989 geomagnetic storm that led to the collapse of the Hydro-Québec power system, GICs of hundreds of amperes were measured. While transformers are designed to handle thousands of amperes of alternating current, they are generally not designed to handle direct current like GICs, which can lead to transformer saturation and increased reactive power demand.

Now, let’s talk about resonances. The electric grid can have resonant frequencies due to the combination of inductive, capacitive, and resistive elements. Resonances can cause the system to magnify the effects of incoming disturbances, much like how a tuning fork resonates at its natural frequency. When a geomagnetic storm induces currents in the Earth, those currents generate a magnetic field that interacts with the magnetic fields of transformers and transmission lines. If the frequency of these geomagnetic disturbances happens to match or come close to a resonant frequency of the electrical grid, the amplitude of the induced currents can be significantly magnified.

To be specific, resonances can occur in multiple parts of the system:

1. Transformer windings have their own resonant frequencies, at which the impedance becomes high, leading to larger voltage across the windings for the same amount of GICs.

2. Long transmission lines can have characteristic impedances that interact with the impedances of transformers and other elements to create resonant circuits, thus amplifying the GICs in localized regions.

3. Harmonic resonances can occur when nonlinear elements like transformers generate harmonics that coincide with resonant frequencies in the grid, thereby magnifying the effective GICs.

So, even though individual transformers may be able to handle small DC currents without immediate failure, the presence of resonances and the cumulative effects across a large, interconnected grid make GICs a non-trivial concern.

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