Voltage unbalance emission assessment: Sources of contribution and their ranking

Determining sources of voltage unbalance (VU) and quantifying their individual contributions in an interconnected network is a complex task due to multiple interactions that take place between them. Post-connection VU emission assessment techniques in relation to customer installations are important not only in compliance assessment according to IEC/TR 61000-3-13:2008 Limits - Assessment of emission limits for the connection of unbalanced installations to MV, HV and EHV power systems, but also in determining the various emission contributors in the power system being considered. This paper presents a case study on the application of a recently developed post-connection VU emission assessment methodology to a 66 kV interconnected sub-transmission network owned and operated by an Australian network service provider. The study incorporates the evaluation of constituent components of the resultant VU factors at busbar levels, identification of the dominant emission contributors and a methodology for ranking of the emission contributions made by the asymmetrical transmission lines in the network. Outcomes obtained through the VU emission assessment methodology are validated using three-phase, unbalanced load flow analysis.