There has been much discussion of properly making connections to electric sub panels in places like barns and workshops. I have two very similar electrical situations, one in my workshop and one at our two way radio site. Both installations are from the 1950"s and feature no grounding conductor to the remote loads, only the grounded neutral and a hot. The line to the workshop is about 60 feet direct burial, through a landscaped area, and the one at the radio site is about 150 yards on poles with bare Copperweld wire.
The goal is safety and radio frequency noise suppression. The VFD on my lathe causes all sorts or RF noise since the case is not grounded. At the radio site, the tower and all incoming cables are grounded by several ground rods for noise an lightning protection, thus all cabinets are grounded through the antenna cables, but the neutral is not at this ground potential.
Thinking about the commercial radio sites I have worked at with a generator and service drop on a separate building, there gets to be an interconnection between the lightning/RF ground and safety ground. This is through the antenna cables going to the equipment and through the grounded plugs to the AC outlet or metal conduit to power supplies. This is probably not the best thing, but is shows a common situation where two separate ground systems end up tied together.
Is there anything short of adding a ground wire from the main panel to the remote loads? I am interested in all answers... Practical, theoretical, and code related.