We know that for transposed sheath and cross bonded cable, loss factor due to circulating current is neglected and loss factor due to eddy current is considered. Suppose, I have cable and it has an Aluminium sheath and beneath the sheath there is a concentric layers of copper wire and above the sheath is the cable jacket. Now, to find out the loss factor due to eddy current, I need to know the mean diameter of the sheath. I tried several things, but could not find out this mean diameter. If someone come and share his experience with this calculation that would be a great help. I can provide the data sheet of the cable.