Electricity distribution networks’ analysis with particular references to distributed generation and protection

Electric power systems have served well the consumers need for continuous, uninterrupted power supply of good quality and at the minimum possible cost. However, nowadays, the worldwide increasing demand on electric power, coupled with governmental policy changes towards “green” energy and emissions reduction have led to significant changes in the electric power generation. These changes have introduced many serious issues and problems to the electric power systems and although they have been efficiently addressed in the past years, now they need to be restudied and reanalysed taking into consideration all new developments. Distributed generation (DG), constitutes one of the most important developments in modern electric power systems and introduced many benefits as well as drawbacks. DG units are connected to the electric power system near load centres, thus, directly to the distribution network. DG units are larger in number than the more massive conventional power stations and are linked to the introduction of bidirectional power flow. As a result, the configuration of the traditional electric power systems and the networks’ operation have been prominently altered over the last years as soon as DG was introduced into the electric network. This progress has offered many challenges that need to be addressed such as those in terms of control and protection of electric power systems and particularly of distribution networks. The current PhD Thesis attempts to offer a contribution to the electricity distribution networks’ studies with particular reference to distributed generation and protection. In particular, the problems and the issues arising from the installation of DG units in distribution networks are studied. Research on the methods for improving voltage profiles and for reducing real and reactive power losses in distribution networks caused by DGs installation is conducted. Moreover, a decision making algorithm is developed and proposed for selecting the optimum size and location of DG in distribution networks. Furthermore, a new technique based on syntactic pattern recognition for the identification of power system signals used by protective relays is developed in an effort to contribute in the deterrence and reduction of faults. Finally, extensive studies in a distribution network have been conducted, with and without DGs, which aimed to identify the influence of several important parameters in the network’s lightning performance and with its main goal the limitation of lightning faults