Rebuilding a grid while it is being hit
The electricity system stayed up through repeated damage. That was not luck; it was a small number of engineering decisions and a very large number of repair crews.
A national electricity grid is not one thing that can be switched off. It is generation, high-voltage transmission, substations and distribution, and each layer fails differently. Understanding which layer was under pressure explains what was done about it.
The vulnerable component
High-voltage autotransformers at substations. They are enormous, they are made by a small number of manufacturers worldwide, they take many months to produce and they cannot be improvised.
Damage to a substation therefore matters far more than the same damage to a length of line, because a line can be restrung in days and a transformer cannot be replaced at all without one existing somewhere.
What was done
Physical protection of the most critical substations — gabions, concrete, blast walls — which does not stop everything but converts a destroyed unit into a repairable one.
An international supply effort to obtain spare autotransformers, which is one of the least visible and most consequential forms of support the sector received.
Redundancy in routing, so that load can be re-fed from a different direction when a node is lost.
The crews
The system stayed up mainly because repair teams worked continuously, frequently within hours of damage and frequently in conditions where a second strike was possible. That is not an engineering fact; it is a labour one, and it belongs in any honest account.
The design conclusion
Resilience came from dispersion, spares and speed of repair rather than from hardening alone. A system built to be repaired quickly outperforms one built to be invulnerable, because nothing is invulnerable.
If you know the crews who work in the field you read the end of this piece differently. What commissioning work taught me is that the resilience of a system depends less on its design than on how many people know it well. A small number of engineering decisions made it possible for the grid to survive; what actually kept it up was the large number of people applying those decisions at two in the morning.
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