Nonlinear Loads Effect on Harmonic Distortion and Losses of Distribution Networks

This paper investigates the harmonic distortion and losses in distribution networks due to large number of nonlinear loads. These days the number of nonlinear loads in power systems is increasing dramatically. These nonlinear loads inject harmonic currents and voltages. Due to widespread usage of nonlinear loads in distribution systems, the harmonic distortion of the current and voltage increase. Power quality of distribution networks is severely affected due to the flow of harmonics. These harmonics can cause serious problems in power systems, excessive heat of appliances, components aging and capacity decrease, fault of protection and measurement devices, lower power factor and consequently reducing power system efficiency due to increasing losses are some main effects of harmonics in power distribution systems. This paper investigates the amount of the harmonics caused by the nonlinear loads in residential, commercial and office loads and also estimates the loss of energy due to nonlinear loads harmonics. In order to analyze effects of nonlinear loads, electrical characteristics of more than 32 common nonlinear appliances are measured using a power quality analyzer set. In order to estimate harmonic distortions and losses in distribution networks a sample distribution network is modeled. The model follows a bottom-up approach, starting from calculating end users appliances Norton equivalent model and then modeling residential, commercial and office loads by synthesis process. The presented harmonic Norton equivalent model of end users appliances is a simple and accurate model which is obtained based on the data from laboratory measurement results. Residential, commercial and office load types model is obtained by synthesis of their corresponding appliances and finally a sample distribution feeder in modeled by aggregating different types of loads. To study the harmonic distortions level and losses in distribution systems, a sample 20 kv/400 v feeder with nonlinear loads is simulated and increase in loss due to nonlinear loads is also estimated.

Keywords:

component , Harmonic Distortion , Loss estimation , Non-linear loads , Norton equivalent model , Power quality