Half-cycle saturation in a transformer, the classic geomagnetic failure mode, burns energy as heat and injects harmonics. It also soaks up reactive power, which is the unglamorous product that keeps voltage standing up. A system can look like it has enough real power and still collapse because voltage support vanished.

Real power is the part you can picture: it turns motors and lights lamps. Reactive power is the part that holds voltage up so the real power can do its work. When saturated transformers drink it, the system can be rich in generation and poor in voltage at the same time. Operators watch that gap. It is not a technicality.

That is why the symptom can be widespread and weird rather than one exploded building: alarms, trips, voltage excursions, then a cascade. It is also why “we have plenty of generation” is not a complete answer to a solar-storm question.

A cascade in this mode does not require a single dramatic failure on camera. Voltage sags, a line trips, the remaining network takes more stress, another protection scheme decides it has seen enough. From the outside it can look like the grid quit for no reason. From the control room it looked like a support problem that got ahead of them.

Harmonics are the other half of the same saturation. They heat equipment and they can confuse relays that were tuned for cleaner waveforms. The event can present as heat, as a trip, and as a voltage problem in the same hour. None of those requires the utility to be out of fuel.

You do not need to run the power-flow study. You need to believe the operator who says the problem is voltage, not fuel.

Belief, here, is practical. If the instruction is to reduce load, or to expect outages while they put voltage back together, the instruction is not a confession that someone forgot to buy fuel. It is the public edge of a problem you will not see from the meter. Arguing from a headline about spare generation misses the product that actually ran out.