Practical evaluation of voltage unbalance at a distribution transformer based on 50 Hz negative sequence active power

The paper investigates the measurement and propagation of voltage unbalance at a distribution transformer. The relations between unbalance factors in voltage and current with the direction of negative sequence fundamental frequency active power are investigated. The goal is to evaluate possible applications of the principles derived by a simulation study in the practical assessment of how much variation in voltage asymmetry is contributed at an interconnection due to loading and how much is due to supply conditions. It is shown that a practical assessment of voltage asymmetry is not straightforward.