The best protection (before a meltdown occurs) is the Bourns MF-R050 PTC re-settable fuse combined with replacing the factory control switch what is notorious for sticking in the on position. I'll edit this reply with a link to another thread showing how to install them which also includes more info about this melting issue with Fastrack Uncoupler electromagnets.
I bought a Lion Chief Polar Express set for a young relative and augmented it with some switches and uncoupler tracks. I found out two things after buying the parts: (1) the uncoupler track requires 10 volts AC so it cannot be connected to the Lion Chief power source and (2) the factory control switches both stuck. What was Lionel thinking? For a company that likes to advertise the "plug and play" compatibility of its accessories, the uncouplers are anything but. I understand they are not specifically labeled "plug and play" but still, they don't have to be the direct opposite.