Calculation Methods of Voltage Unbalance Factor

This paper describes seven different methods used for determining voltage unbalance factor (VUF) and comparing them. Voltage unbalance (VU) is a critical phenomenon that can’t be fully mitigated from power networks. Previously, it did not have the same attention as nowadays due to the increasing focus on power quality problems. Besides its bad effects, which may lead to a disaster, especially for low voltage customers, this attention is due to the increasing penetration of renewable energy sources (RES) in all distribution networks. As RES in general and roof-top photovoltaic (PV) cells in particular are considered single-phase sources, their existence leads to a VU increment. Each method has a strategy to calculate VUF. Power electrical communities, like (the international electrotechnical commission (IEC), the institute of electrical and electronics engineers (IEEE), the national electrical manufacturers association (NEMA), and the international council on large electric systems (CIGRE)) have addressed a computational methodology for calculations that is limited to applying conditions to get accurate results. These limitations as well as an accurate comparison between those methods are clearly outlined below. The CIGRE method, besides the complex voltage unbalance factor (CVUF) method have been detected as the most accurate techniques among all the techniques used.