Distribution voltage imbalance mitigation through transmission line ideal phasing

Abstract

Transmission line ideal phasing was used to mitigate a distribution voltage imbalance problem. Customers in the common service area of an electrical substation had been reporting power quality problems related to voltage imbalance. Through investigation, an unexpected pattern of seasonal voltage imbalance variation was found to be consistent with transmission network power flow patterns. Linear regression techniques were used to determine relative contributions of each transmission network element to the voltage imbalance problem. A double-circuit transmission tower line with no transpositions and non-ideal phasing was identified as the source of the voltage imbalance problem. This finding was verified through three-phase power flow simulation. Transmission line ideal phasing was identified as the preferred mitigation alternative. This solution was constructed as a minor scope modification of an unrelated project in the same geographic area. As proven by post-construction monitoring data, this solution has yielded significant power quality benefit for existing distribution customers.