Problem: My cables are installed (buried) in a concrete backfill. For my magnetic fields study calculation I require an input for relative soil permeability. Concrete has a different relative resistivity compared with the native soil. See images below.

Typical relative permeability values are provided in this article.

The magnetic fields module of Cable HV Software has been developed assuming that the media surrounding the cables are homogeneous, isotropic and linear. When we have a backfill with a different resistivity, the media is no longer homogenous.

The magnetic field intensity is directly proportional to the relative soil permeability. However relative soil permeability does not vary much.

In this case the solution is to use the highest relative permeability of the medium.