I'm planning to take a 300w PIR light off my outside house wall and re-positioning it on a tree trunk 25m down the garden. Cable run totals 30m. Two options for cable, buried in ground (favourite), or fixed to garden wall. What kind of cable would I need for these two options? Could a cable be simply buried in a shallow sand filled trench and covered with soil, or would it need more serious protection/conduit/sleeve? I'd be very grateful for any observations.