Fault Level Analysis in Modern Electrical Distribution System Considering Various Distributed Generations

Reliable power supply had always been the prime concern for the electricity consumers. With the introduction of inverter based generation technologies and smart electrical grids, there has been a huge rise in the integration of Distributed Generations (DGs) like Solar PV, micro wind, diesel, bio-mass, etc with the main grid. Integration of DG has helped in meeting the consumer demand more optimally and in minimizing the transmission losses. Distributed Generation not only has increased the system reliability, but it has also improved the quality of the power supply of the Prosumer. At the same time DG integration also brought in some new challenges- protection being one of them. Designing a good protection system and coordinating the relays would require the understanding of fault current values and bus fault levels. Fault Analysis need to be carried out in the presence of DG's, which will be used for the system protection update or to design new distribution system. Further, the addition of Distributed Generations will vary the existing fault levels (i.e., either increase or decrease). The fault currents will be different for the conventional synchronous machine based distribution sources like Diesel generators, micro hydro, combined heat and power units and for that of inverter connected based sources like Solar and Wind. In this paper, detailed analysis of the fault levels considering different types of DGs will be carried out. Towards this, four different cases are analysed - Case1: Fault level at a bus only with Grid connection, Case2: Fault level at a bus with Conventional DG sources connected, Case3: Fault level at a bus considering inverter based DG connection and Case4: considering a hybrid combination of different types of generations. `MiPower' power system simulation tool has been used for carrying out these studies. Further, results are presented and conclusions are drawn.