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Increased penetration of distributed generation (DG) will impact on power network protection systems. Many publications present solutions to protection problems such as blinding, false tripping and loss of grading for networks incorporating DG, but neglect to fully quantify and demonstrate the problems that are being addressed. This study fills a gap in the understanding of the particular problem of protection blinding through presenting a detailed study of the impact of DG on overcurrent protection using a typical UK rural distribution network. This study considers all relevant factors, such as: fault level, DG penetration level, DG location, DG technology, fault type, fault location and fault resistance. The main emphasis and value of this study is in the use of justified and realistic network data, fault (including arc fault) models, utility protection settings policies, real-time simulation and actual protection relays (employed as hardware in the loop), all of which enhance the credibility and validity of the reported findings. The simulations quantify when blinding can occur and demonstrate that, for phase faults, DG is very unlikely to cause blinding, whereas for earth faults (EFs), DG actually increases the sensitivity of EF protection.