Fault current coefficient and time delay assignment for microgrid protection system with central protection unit

With growing numbers of distributed generators (DGs) getting connected to the network, new protection schemes are required. These schemes are aimed at responding to the changing fault current values, bi-directional current flow and distributed generation (DG) at all levels of the grid. For this purpose these schemes utilize comprehensive protection systems with extensive communication and coordination between DGs and protection devices such as relays. This paper details the assignment of two parameters which are critical for proper operation of a microgrid protection system. The first parameter, the fault current coefficient, represents the fault current supplied by any DG to any point inside the network whereas the second parameter is the adjustment of relay hierarchy for selective operation of relays. The automated assignment of these parameters serves the notion of self-operating microgrid protection system. Furthermore, elimination of manual design and calculation facilitates deployment of new DG units and thus makes it possible to design plug-and-play DGs and protection devices.