Voltage unbalance emission assessment

Aim of this paper is to draw the attention on the principle origin for unbalance, taking into account the part caused by negative sequence currents as well as the part arising from non ideal grid impedance with non negligible coupling impedance between the positive and negative sequence system. This system inherent part originates from non transposed lines or parallel three phase lines operating over long distances. In 61000-3-13 this is taken into account by a factor k
_uE
, which is explained in this paper.