A professional cannabis plantation consumes lots of energy. On top of the total amount of electricity required, one additional difficulty arises - if power is switched on for multiple lighting sets, e.g. several HPS or MH lamps with ballasts, and accompanying fans, it could overload the existing electrical grid.
One way to avoid such nasty situation is to separate the whole production into several separate factions, each with a slight time interval to each other (each set of, say, 6 lamps, might be switched on 3 minutes after one another). Still, a danger of overload will always exist - for that purpose, reliable fuses are an absolute must.
Fuse is an element of the electrical setup, that breaks the circuit if it detects too high a current. This little things could actually save your life if something gets bad - and with water and electricity close to each other, chances of that happening are not negligible.