With the Feast of All Hallows rapidly approaching I thought it would be apt to explain how the grid is haunted by a concept that doesn’t really exist. A pre-occupation with a made-up concept risks the security of our power grids. In this blog I will explain how “vars” aren’t real, and treating them as if they are is creating existential risks on our power grids.

Not being able to properly explain reactive power is common in the energy industry – ask a dozen people to explain it and you’ll get twelve different answers. Most will reach for the beer-glass analogy where real power as the liquid and reactive power is the froth, or mutter something about “energy sloshing back and forth” on the grid. More sophisticated responses will mention capacitors “injecting vars” and inductors absorbing them. These phrases are repeated so often that they’ve become folklore. Unfortunately none of them describes what actually happens in power grids.

“Vars” in particular is an accounting fictions that obscure the underlying physics. And because we’ve replaced understanding of the physics with shorthand, we now incorrectly believe that anything producing current including batteries, solar inverters, or a clever algorithm, can perform the same stabilising role as the electromagnetic machines that built our power system.This misunderstanding could one day cost us the grid.

Go read it.