Requirement to enlarge interface protections frequency ranges for generators connected to distribution networks: Study of alternatives and solution proposal

New requirements on the stability of the European interconnected power system may lead to a lesser use or even the complete removal of interface protections based on narrow frequency ranges (e.g. [49,5 – 50,5 Hz] in France) for distributed generators connected to the distribution network. As this type of protection allows detecting rapidly most islanding situations, its disappearance would reduce the efficiency of both fast reclosing schemes and islanding detection. A palliative solution must be found that combines technical feasibility, efficiency, low cost and ability to be applied to both MV and LV connected generators. This paper first proposes a method to evaluate the risk of islanding on a MV feeder and then considers the cons and pros of various alternatives to a narrow frequency range interface protection before focusing on a solution currently investigated for the French Distribution network.