Current Triggered Relay

First it is not a crowbar. It will be if relay when triggered make short circuit and by this blow fuse up but this will be no benefits cuz crowbar make short circuit whole device to make all transient current spike on chest not allow it to spread around device and do this because fuses are slow and crowbar is fast so until fuses not wake up and shut off crowbar proudly show his biceps taking lots of currents on his own so relay is simply too slow. Second - even as norrmal overcurent protection relay shoud be closed at triggering not open. Why?? Because relay if conduce high currents at open produce arcing so intense that it can weld contacts during opening and do this so fast that contacts barely move. More even if not weld but contacts are arced few times they weld themselfs during close up cuz arcing also during closing ignite for moment. More if those are operte non stop closed they heat up and hot contact much better weld themself and promote bigger arcing. And u not want that ur protection not open at all when it is in urgent need cuz overcurent was detected. Oh and closing a relay is faster than opening :-)