The portion of energy converted by non-linear loads in the modern power system is increasing due to the energy-efficiency and sophistication possible with power electronics. Higher voltage and energy ratings are continuously forthcoming. These devices draw non-linear currents resulting in voltage waveform distortion at the Point of Common Coupling due to non-zero supply impedances between voltage source and the PCC. With the increase in waveform distortion comes the demand for better Quality of Supply management. The verification and quantification of the origin of waveform distortion in a power system is a continuous field of study and forms a critical part of the mitigation design. Methods utilizing single-point measurements, usually taken at the Point of Common Coupling, for the assessment of the harmonic distortion generated by loads are continuously being published. It’s been proven by means of computer simulations and laboratory experiments that in an interconnected network where multiple sources of distortion exist that loads have the ability to exchange harmonic active power between each other. This project investigates the latter statement by conducting practical experiments to conclude that loads have the ability to exchange harmonic active power and that multiple synchronized measurements should be taken to assess the harmonic distortion due to a load. Laboratory experiments are carried utilizing an acknowledged single point measurement method. The results are compared to the direction of harmonic active power obtained from utilizing multiple synchronized measurements. To further the information obtained from the laboratory experiments, practical experiments were conducted utilizing the same methods. The results obtained coincided with the results of previously conducted experiments of which the results were published. From the results obtained it was concluded that in an interconnected network where multiple sources of distortion exist that loads have the ability to exchange harmonic active power between each other. Furthermore it was proven that the single point measurement method investigated presented inconsistent results. Ultimately it was concluded that the reason for the inconsistency was due to the fact that loads have the ability to exchange harmonic active power and that the single point measurement failed to acknowledge this. / Thesis (M.Ing. (Electrical and Electronic Engineering))--North-West University, Potchefstroom Campus, 2012

The portion of energy converted by non-linear loads in the modern power system is increasing due to the energy-efficiency and sophistication possible with power electronics. Higher voltage and energy ratings are continuously forthcoming. These devices draw non-linear currents resulting in voltage waveform distortion at the Point of Common Coupling due to non-zero supply impedances between voltage source and the PCC. With the increase in waveform distortion comes the demand for better Quality of Supply management. The verification and quantification of the origin of waveform distortion in a power system is a continuous field of study and forms a critical part of the mitigation design. Methods utilizing single-point measurements, usually taken at the Point of Common Coupling, for the assessment of the harmonic distortion generated by loads are continuously being published. It’s been proven by means of computer simulations and laboratory experiments that in an interconnected network where multiple sources of distortion exist that loads have the ability to exchange harmonic active power between each other. This project investigates the latter statement by conducting practical experiments to conclude that loads have the ability to exchange harmonic active power and that multiple synchronized measurements should be taken to assess the harmonic distortion due to a load. Laboratory experiments are carried utilizing an acknowledged single point measurement method. The results are compared to the direction of harmonic active power obtained from utilizing multiple synchronized measurements. To further the information obtained from the laboratory experiments, practical experiments were conducted utilizing the same methods. The results obtained coincided with the results of previously conducted experiments of which the results were published. From the results obtained it was concluded that in an interconnected network where multiple sources of distortion exist that loads have the ability to exchange harmonic active power between each other. Furthermore it was proven that the single point measurement method investigated presented inconsistent results. Ultimately it was concluded that the reason for the inconsistency was due to the fact that loads have the ability to exchange harmonic active power and that the single point measurement failed to acknowledge this. / Thesis (M.Ing. (Electrical and Electronic Engineering))--North-West University, Potchefstroom Campus, 2012

Afin de maintenir une bonne qualité de l’électricité, les gestionnaires de réseaux doivent maintenir les niveaux de tension harmonique en-dessous de certaines limites spécifiées dans les normes. Les niveaux de tension harmonique résultent des équipements non-linéaires présents dans les installations, qui injectent des courants harmoniques sur le réseau.Dans ce but, une solution consiste à appliquer des limites d’émission à ces installations. Les gestionnaires de réseaux ont besoin pour cela d’un indicateur fiable pour évaluer le niveau d’émission harmonique d’une installation.Dans ce cadre, nous nous sommes tout d’abord intéressés aux différentes méthodes existantes, que nous avons appliqué sur des cas de réseaux simplifiés afin de les évaluer sur plusieurs critères. Nous avons ainsi identifié dans un premier temps les définitions qui répondent le mieux à notre besoin ainsi que leurs limites restectives. Dans un deuxième temps, nous avons amélioré une des définitions retenues en proposant une nouvelle solution : la définition “quatre quadrants”.Cette nouvelle définition permet d’évaluer le courant harmonique émis par une installation sur le réseau en se basant sur les mesures de la tension et du courant au point de livraison de l’installation. Son principal intérêt par rapport aux méthodes existantes est de mieux identifier les installations moyennement perturbatrices sur le réseau. Ce point a été validé en simulation sur un réseau dérivé du benchmark CIGRE. / In order to maintain good power quality, Distribution Systems Operators (DSOs) must keep harmonic voltage levels under limits specified in standards. These harmonic voltages result from non-linear equipment connected in installations, which inject harmonic currents into networks.A possible solution to solve this problem consists to implement emission limits per installation. In order to apply these limits, DSOs need to have an accurate and reliable indicator to assess the harmonic emission of an installation.In this context, we studied different methods from the literature. We implemented each of them on several simplified distribution networks in order to evaluate them on several criteria. First, we identified the most interesting definitions from the literature, and emphasized their respective theorical limits. Then, we improved one of these definitions by proposing a new solution: the “four-quadrants” definition.This new definition is able to assess the harmonic current injected by an installation into the network by using current and voltage measurements at the point of common coupling of this installation. Its main advantage in comparison to other methods is a better detection of “medium” disturbing installations over the network. This advantage has been confirmed by implementing the proposed solution in simulation on a distribution network derived from the CIGRE benchmark.

A model of the accurate harmonic allocation methods is developed to improve the current emission limits of IEEE Std.519. IEC 61000-3-6 and IEEE Std. 519 have by now been accepted as two well known standards for interconnecting the MV and HV-EHV customers to utility systems and widely adopted as standards to many power utilities. It is worth noting that the harmonic current emission limits of both standards have not been compared and justified with analytical proofs because there is still no explanation that discusses the origin of the emission limits in IEEE Std. 519, or the complex feature of IEC 61000-3-6. Two new novel methods of allocating the harmonic current emission limits for MV customers and HV-EHV customers have been proposed. Both methods have been developed in accordance with the principles of IEC 61000-3-6. Task II has compared and investgated the emission limits of both IEC 61000-3-6 and IEEE Std. 519. The difference, inconsistency and inaccuracy have been proven with the perspective of practical evaluations based on their own principles. The investigations focus on the specific numerical proofs of the resulting voltage distortions and the current emission limits in the MV and HV-EHV systems rather than on the philosophies. The proposed methods strongly support IEC 61000-3-6 and IEEE Std. 519, and add to their value; these methods could also help utilities allocate fairly and accurately harmonic emission limits to their MV and HV-EHV customers.