Influence of Transformer Rating on Power Quality Indices in Low Voltage Residential Networks

This paper proposes a methodology to assess the influence of transformer rated power on the power quality indices at low voltage residential networks. Taking into account the stochastic nature of residential loads and the possibility of photovoltaic generation, a Monte-Carlo simulation is performed in order to account for the probabilistic aspects of the problem.In this work, different transformer ratings are simulated and the effect on power quality parameters, such as voltage unbalance and voltage total harmonic distortion (THD), is calculated under probabilistic basis. These power quality indices are compared to the compliance limits proposed in standard EN50160.The work proposed in this paper allows predicting power quality affection caused by changes in the ratio between transformer rated power and network aggregated demand, as well as establishing general conclusions regarding desirable transformer size in order to not to exceed power quality limits.