Power protection with generator

Back before solar got cheap our main customers were operators of remote telecom sites, many of which are on tops of mountains. So I had to learn about lightning protection and spent someh pretty interesting nights in electrical storms.

The thing about lightning is that essentially only big power circuits will survive a direct strike. Those involve hundreds of kiloamps. You have to have lightning electrodes, heavy conductors, and robust grounding systems to handle that.

Under the cone of protection provided by the lightning electrode system you still have to worry about damage from electrical surges induced in the circuit wiring. These currents are induced by the rapidly changing electromagnetic fields created by the lightning itself, similarly to how an antenna or a generator works. The induced currents are proportional to how much magnetic flux passes through the circuit loop. That’s why sensitive electrical signals are sent via wire pairs that are twisted together to avoid creating a loop. For the same reason we quickly learned not to daisy chain our solar modules together in big loops.

The induced currents in large loops or grid connections can still be in the range of kiloamps or 10s of kiloamps but they are short enough in duration (microseconds) that they can be handled by various types of transient suppressors, the primary ones being metal oxide varistors. Those are rated in kilojoules of energy dissipation capacity which is why you see those specs when shopping for RV surge protectors. Typical ones might be rated at around 4 kilojoules which is about 1 watt hour. Doesn’t sound like much but it’s being dissipated in a few microseconds so the power levels are huge.

Anyway the point is that with a portable generator that is ungrounded and a 25 ft RV cable that doesn’t create a large wire loop, there really isn’t the need for a surge protection device like there is when you’re connecting to an RV park’s big grounded grid connection. It won’t hurt to have it but just a simple surge protector would be better than a fancy smart circuit analyser in this case because that wouldn’t require an additional bonding plug to trick it into turning the juice on.