ABSTRACT
A good estimation of the electric field is obtained in a certain region of a transformer by idealizing the geometry to such an extent that the field can be calculated analytically. This chapter considers a layered insulation structure having a planar geometry. It represents the major insulation structure between two cylindrical windings having large radii compared with the gap separation. A somewhat better estimate can be made of the electric field in the major insulation structure between two coils if we consider approximating the geometry as an ideal cylindrical geometry. This geometry is also useful for approximating the field around a long cable of circular cross section. Another geometry of some interest is the spherical geometry. Cylinder–plane geometry is a reasonable approximation to a commonly occurring configuration in transformers in which a cable or lead runs parallel to the tank wall. Finite element methods permit the calculation of electric potentials and fields for complicated geometries.
