Impact of voltage waveform quality on distribution network planning

Abstract

The present study investigated the power losses in a specific portion of the MV distribution network in Potchefstroom, South Africa. This was done in an attempt to assess and predict the impact of harmonic distortion on distribution network planning. In addition, the newly developed concept of prevailing harmonic current phase angles was used to determine the impact of distributed generation (DG) on distribution networks. With the current drive towards alternative energy sources DG will play a major role in the planning of future distribution networks. Potchefstroom local authorities gave permission for power quality recorders to be installed on their active network. The area isolated for this study traces the power along one feeder from the distribution substation, Gamma, up to the end-user, North-West University. This feeder supplies a load mix of small businesses, housing and classrooms. Applying mathematical models, derived from literature, to collect data allowed for the calculation of the impact of harmonic distortion on distribution network power losses. For the DG analysis, data was collected at three different sites before and after the installation of a solar PV system. This data was used to calculate the prevailing harmonic current phasors for the fundamental, third, fifth and seventh harmonic. Calcaulations were done for pre-installation, PV only and post-installation scenarios to allow for thorough evaluation and estimation of results. The main study allowed for the development of a quick reference guide for the impact of harmonic distoriton in distribution networks. This guide can be used by city electrical engineers when planning future distribution networks. Using the phase angle study as a basis, future research would allow for a similar tool to be developed in order to estimate the impact of DG on the harmonic distortion in distribution networks.