This is the mythical power-grid attack that people have been talking about since the concept of cyber-warfare was first dreamt up. It’s lucky we caught this now, before there are enough PowerWalls to seriously destabilise the grid if this attack were to occur.
Rate of Change of Frequency protection (ROCOF) in embedded storage and generation systems is what will kill the grid in a massive cascading failure. ROCOF works well to keep things safe when only a small percentage of the grid demand is met by residential solar/powerwalls. As soon as any significant proportion is residential solar (and thats already the case in some countries at some times of day) it acts as a cascad…
That gold code could be received and decoded anywhere on the network. If power islanding occurs, embedded generation will detect the loss of the gold code (since they are no longer connected to the generator injecting the code), and cease supply.
The only disadvantage is it introduces a security vulnerability by design: Anyone could transmit the gold code from their house, effectively disabling islanding protection in their neighbourhood. If power islanding were to occur, and if there was sufficient embedded generation to keep a stable power island, grid hardware could be destroyed through overvoltage, overheating, and circuits closing without frequency synchronisation. I think it's a worthwhile tradeoff though - damage will be localized and minimal, and a very unusual set of circumstances have to happen outside the attackers control for the attack to do damage.