A transformer (900) comprising a primary-side auxiliary winding (976, wherein in use the primary-side auxiliary winding (976) is configured such that a first electric potential distribution is induced in the primary-side auxiliary winding (976); and a secondary-side auxiliary winding (982) configured such that a second electric potential distribution is induced in the secondary-side auxiliary winding (982). The primary-side auxiliary winding (976) is physically located between (a) a main pair of windings; and (b) the second-side auxiliary winding (982). A first portion of the secondary-side auxiliary winding (982) is positioned adjacent to a shield-portion of the primary-side auxiliary winding (976) such that the first electric potential distribution matches the second electric potential distribution: (1) along the respective lengths of the first portion of the secondary-side auxiliary winding (982) and the shield-portion of the primary-side auxiliary winding (975); and (2) over a frequency range that is greater than a particular threshold frequency.