Transient stability of distributed generation in MV-ring networks

Due to the increase of distributed generation (DG) in the future it can become important to keep DG connected to the grid in order to maintain balance between consumed and generated electrical power. Keeping DG-units connected to the grid during a disturbance, the dynamic behavior of the DG-units becomes important. To guarantee after fault clearing stable operation of the DG-units, the protection scheme and settings have to be changed. In this paper conventional protection schemes of MV- ring networks are discussed as well as the additional measures that have to be taken to protect a MV-ring network including DG properly. It is found that it is not possible to find a proper relay setting to protect the MV-ring network in such a way that the fault clearing process is fast enough to maintain stability of the DG-units. In the paper it is demonstrated that the fault clearing process can be sped up by adding communication to the protection scheme