A wire carrying voltage expects a _" normal" load , but not a direct short to ground which tells the current god to supply all its got. That is current like an arc welder. To avoid smoke and fire a fuse is used to disconnect the wire until a repair can be made. As noted loosen all wiring and look for chafed, split, cracked insulation or even a broken stub of wire flopping around. And sometimes the device hooked up can fail and draw excessive current, opening the fuse. Patience, These are most frustrating problems sometimes.