Real-time modelling and simulation of distribution system protection with and without renewable distribution generation.
Nkhasi, Ntuba Irene.
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The conventional radial power distribution systems were initially not designed to accommodate distribution generation (DG). As DG penetration is being considered by many distribution utilities, there is a rising need to address many incompatibility issues that put a big emphasis on the need to review and implement suitable protection schemes. For a significant greenhouse gas reduction using photovoltaic systems, numerous generators ought to be embedded in the distribution system. For an effective penetration of PV systems on a large-scale into the current distribution network, considerable work to investigate the nature of incompatibility problems has been done and research is being carried out to develop successful integration strategies. The main objectives of the thesis are; to model and simulate a distribution system protection scheme, to study radial networks’ protection system challenges after embedding distributed generation sources, investigation on the impacts of high PV penetrations on protection systems of distribution networks and lastly make modification recommendations and essential review process of existing protection equipment settings. To accomplish the above-mentioned objectives, a radial distribution network is modelled, simulated and protection settings validated. The PV generation system is designed and added to specific distribution feeders and steady steady-state results obtained. The results show that addition of DGs cause the system to lose its radial power flow. There is an increase in fault contribution hence causing maloperation such as protection coordination mismatch. An overall protection scheme is then proposed based on the addition of DG’s and an efficient adaptive protection system for the distribution networks with a considerable penetration of dispersed generations implemented. The impact study is performed which is compared with the existing protection scheme and necessary modifications done. The entire analysis is simulated on a real-time digital simulator (RTDS) and results displayed in a MATLAB environment. For the islanded mode, relaying considerations are provided and implementation of anti-islanding techniques achieved.