I it the CFE or the park? That depends on where you are and when the park was wired. Newer parks are required to pay for their own Transformer. I think it drops 440 ( maybe 3 phase) to 220 and 440. If you look at a decent US park the incoming power goes to a massive disconnect. From their it remains at 220 and goes to the various large panels. And then to the pedestals. Hard to find something like that in Mexico. In small pueblos the local electrician carries a pair of pliers and rolls of electrical tape. Maybe a multimeter. Some Mexican parks have a simple house type panel. Then they wire 30 sites! Low voltage is then a problem when the park gets full. The old Oaxaca park would drop to 90 when a Caravan came in! Surges are usually the fault of the CFE. If the power has been off when it comes back sometimes there is a big surge. Some parks are built in the country where the lines are far from the power station. Lots of resistance. When we first moved to Kino the power would go out at least once a week. Sometimes for 6 hours. Today it rarely goes off. Maybe once a month for less than an hour. But in the summer when all the Mexicans head to the beach it is horrible. Too many people for the amount of available electricity. Then there is the problem on the coast with the salt air. It gets inside the panels and corrodes the connections.
Moisheh