There are Surge Protectors and Surge Protectures. TRC (Technical Research Corp) makers of the Surge Guard line make some that are very good. The portable versions have an LCD display that shows voltage, and current (Alternating) and possibly a warning or two as well as a few LED's they take just shy of 3 minutes to pass power to your RV
The Progressive Industries PW-30 C.. Has a much better warranty. otherwise see above.
Both companies also make some that do not have LCD displays.. Avoid.
THey also make a Hard Wired version,, with a Optional Remote Display, at least i think it's optional. I do not have info on the TRC hard wired but on the PI (HW-30C) you have a choice of 15 seconds or close to 3 minutes on the time before power is passed.. Choose the longer time.
What these do
The low cost no LCD.. Spike suppression When a big motor (Air conditioner) starts or stops (And some other loads as well) there is often a voltage SPIKE, I've seen it knock out computers (They did not listen when I hollered NO and blew out my office, now they listen). but not much of anything else.
The more expensive ones with the LCD do that as well but they also monitor Voltage (And often Frequency) and if it goes high or low (Beyond pre-sets) it will cut you off to protect you
High voltage damages electronics,, Converter, TV, Radio, et-al
Low damages air conditioners and other MOTORISED stuff like residential Firdge.
Likewise high/low frequency can mess things up.
The 3 minute timer protects the Air Conditioner if you have what I call a power "Blink" (power goes out for just a couple seconds) by giving them time to bleed down before they restart.