Managing risks from reverse flows under distribution network outage scenarios

Distribution networks have been traditionally conceived for transporting electricity downstream into low voltage demand nodes. However, the connection of significant amounts of distributed generation may reverse this condition, resulting in distribution nodes exporting power to other parts of the network. The current planning standard of the UK distribution networks (Engineering recommendation P2/6) requires making available sufficient capacity and redundancy for downstream flows under peak demand levels. However, it does not explicitly consider the implications of DG-mediated flow reversals that may cause flow constraints under circuit outage conditions. Relying on a Monte Carlo approach to sample wind and demand with adjustable correlations, this paper provides insights into the risks associated with an increase of variable distributed generation to the point where reverse flows may exceed the connection capacity under circuit outage conditions. Remote tripping schemes that disconnect distributed generators upon occurrence of a fault are explored to mitigate outage related costs. The latter strategy carries benefits but also novel risks in the form of a reliance on real-time communication and control, which may malfunction. It is shown that even unreliable corrective actions convey significant benefits to system reliability.