Factors affecting the field from an overhead power line

In this section we discuss how the field produced by a power line depends on particular factors.  See the left-hand menu.

These pages deal with the size of the field.  See also information on the direction of the field.

All the calculations in these pages are compared to the base case of a 275 or 400 kV line of a type known as L12 (see the dimensions), transposed phasing, 12m clearance, 500 A in each circuit, calculated at 1 m above ground.

Note: equal currents in both circuits, as we assume here, is not always found in practice.  Our main calculations of the fields from different power lines includes an imbalance between the circuits.  We use equal currents as our base case here because it makes it easier to show the effect of varying other factors.  More on balance between circuits.