The Impact of Small and Medium Power Loads on Distribution Network Efficiency and Harmonic Propagation

A substantial amount of loads connected to utility distribution network are small and medium power range loads, of which majority are from residential and commercial/shops customer sectors. As these loads are dispersed across the low voltage distribution network (overhead or underground cables), harmonic mitigation devices or power factor correction capacitors are rarely installed at the aggregate load bus (utility low voltage transformer bus) to improve performance of the network. Harmonic measurements of these small and medium power loads indicate that a majority of them are highly nonlinear and/or have low power factor. As a result, there is a reduction in energy efficiency of distribution network, particularly in network components such as low voltage lines/cables and distribution transformers. This paper investigates real power losses caused by small and medium power range loads of residential and commercial/shops sectors due to harmonic currents propagation and reactive power flow. Results of the investigation are based on harmonic measurements at sites and aggregate load modelling at low voltage bus of distribution transformer.