Comparison of static and dynamic calculations of short circuit currents in distributed generation networks

Distributed Generation (DG) units connected to the distribution network, contribute to the increase of the system fault level. Hence the knowledge of the exact contribution to the fault level by each DG unit is very important. In this paper the calculation of the short circuit current in distribution networks with DG units is carried out following two different approaches. The first approach is the IEC 60909 standard, which although adopts several simplifications and assumptions, in most cases provides results on the safe side. On the other hand dynamic simulations using dynamic tools such as the NEPLAN software are used for the accurate simulation of short circuit currents. Several parameters that influence the short circuit current, such as the length of the distribution feeders and the number of the integrated generators connected to the grid are investigated. From the comparison of the results by both approaches a better understanding of the influence of all parameters and assumptions used in short-circuit calculations is concluded.