Power quality has become an important issue for electric power engineering. These case studies include identification of the key indicators for harmonic performance of a distribution system. Several example systems have been studied to illustrate the harmonic management tools described above. This is achieved by looking at several extreme cases that classify the most common MV distribution system feeder configurations and through the use of correction factors for the allocation constant. An extension to the method has thus been established to cater for the situation where only limited data is available. This approach typically requires an extensive amount of data that may not always be available to distribution network service provider engineers. The method involves the determination of an allocation constant using the agreed loading of all customers and the system harmonic impedances. A generalised method to extend the IEC 6 approach of allocating allowable harmonic emissions to the case where customers are distributed along an MV distribution system feeder having significantly different fault levels is presented. Results from a harmonic monitoring programme carried out on a typical MV distribution system are used to establish parameters for the load models and also to confirm the relative accuracy of the proposed distortion level prediction technique.
A method to estimate the 95(superscript th) percentile cumulative probability level of harmonic voltage distortion in an MV distribution system as required by the present Australian harmonic standard (AS/NZS 61000.3.6) is also developed. Both time and phase diversities are included in the representative load models. In this thesis development of statistical harmonic models of residential, commercial and industrial load types to simulate the global behaviour of distorting loads at distribution substations is presented. This thesis describes the development of harmonics planning and analysis tools that allow effective system modelling and comparison with standards, particularly in the planning phase where details of loads are usually not accessible. Measures will need to be taken at the planning stage to ensure distribution systems are able to meet harmonic limits recommended by standards as distortion due to loads increases. With many distribution customer loads being sensitive to excessive harmonic voltage distortion, electricity distribution network service providers should now be looking towards preventative measures to ensure that voltage distortion levels remain within limits set by the appropriate standards.
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