Adaptive protection scheme for smart grids

The amount of distributed generation (DG) connected to distribution networks is increasing. This can cause challenges for traditional protection of distribution networks due to bidirectional power flows, fault current contribution of DG units and grid code fault-ride-through (FRT) requirements. During the normal, parallel with utility grid, operation, the protection coordination may be compromised and nuisance or delayed tripping may be experienced. After possible transition to intended island operation the situation becomes even more demanding from protection point of view due to low short-circuit currents fed by DG units and sensitive dynamics. Therefore, protection adaptation to different topology changes will be more and more often required in the future distribution networks. This paper evaluates the performance of different protection methods in grid connected and in controlled island operation modes of a part of medium voltage network. The evaluation is done with PSCAD simulation software for an example network. Finally, an adaptive protection scheme for smart grids is proposed.