Bury It. Local codes may vary, but, typically, conductors in conduit need to be buried 18 inches deep, and direct-burial runs need 30 inches of cover.
Protect It. Running wire without conduit on top of the ground may be tempting, but it is a bad idea for the safety of critters (two-leggeds included) and the cable. Any depth of burial is preferable to none, with or without conduit. In addition, breakers should be installed to protect the wiring in the event of a short circuit. Always size the breakers based on the wire’s rated amperage. Because the conductor size is specified with voltage drop over a long transmission run in mind, the ampacity rating of the conductors usually ends up being significantly higher than the actual amperage generated by the turbine. Because of this, you can often use a breaker that’s two times the turbine amperage, which will eliminate nuisance breaker tripping, and minimize the possibility of the breaker tripping and allowing the turbine to overspeed.
Ground It. Hydro turbines can produce lethal voltages and should be grounded to minimize risk. Drive a ground rod at the hydro plant and connect it to the ground terminal provided on the turbine. A dedicated equipment-ground conductor should be run along with the power transmission wiring so your entire system is bonded and has the same voltage potential to ground. In lightning-prone areas, it’s a good idea to include surge protectors at each end of the transmission run.
Don’t Bond It. Do not connect the negative power conductor to the equipment ground at the hydro turbine. The NEC requires that only one negative-to-ground bond exists on the DC side of the system. This should only be done at the DC breaker panel located near the inverters and battery bank. Some low-cost hydro plants use modified automotive generators that are already grounded to negative, which puts the generator at risk if there’s a close lightning strike and can also result in a ground differential throughout the power system that may damage components.