Assuming the transformers are grounded, and the concentric is bonded to the ground, lay a grounding mat down and bond it to the ground. Everything then is at the same potential. If you are working on the actual conductor, ground the conductor with grounding bushings at the open points on either side of your work location. At that point everything should be at the same potential as the mat you are on while working. If you remove the ground from the concentric at your location make sure the concentric is bonded across before you remove the grounds.