Method for determining customer contribution to harmonic variations in a large power network
A method for identifying the source of harmonic emission and for determining its contribution to the harmonic distortion at different points on a large power supply grid is presented in this paper. The proposed method is based on vector analysis of the harmonic currents, measured synchronously at multiple points on the electrical grid. This approach allows real time locating of the responsible customer (harmonic cause) for a given harmonic current disturbance and determining its contribution to the harmonic voltage and current variations at all measured points (harmonic effect). A physical model, representing a power network supplying three non-linear loads, has been used to illustrate the performances of this method. The presented method can be used to analyze the harmonic current and voltage variations in a large power network in real time, thus assisting the electrical power utility to rapidly identify the harmonic causes and their effect and to better understand different problems associated with the harmonics.
Systematic evaluation for harmonic distortion limits from IEEE 519
Every day industry growths and with it, non-linear load components growth as well. This causes sever implications on the power quality. Some standards establish rules and limits in order to guarantee adequate conditions for equipment, and to supply appropriate power to final users. Automatic mechanisms should be explored to contribute with this process of power quality improvement, helping with design and necessary corrections related to harmonic distortion.
Women's choice in the gender and ethnicity of her obstetrician and gynaecologist
Objective: To ascertain women's preferences in the gender and ethnicity of her obstetrician or gynaecologist and to determine whether there were differences in preferences among different ethnic and age groups.