High-voltage power lines

The field strength at ground level produced by underground high-voltage lines (in this setting they are described as “cables”) differs from that produced by overhead power lines. This would screen out the electric fields almost completely, but not the magnetic fields.
Whether or not the magnetic field strength is reduced by placing these lines underground, and if so by how much, is to some extent dependent on the depth at which they are buried. If the cables are not buried at any great depth, then the magnetic field strength at ground level in a narrow strip directly above them can actually exceed that created by overhead power lines. At a horizontal distance in excess of around 10 metres from this strip, the magnetic field strength will actually be lower.