Risk assessment analysis to find optimum ROCOF protection settings

The rate of change of frequency during transmission system disturbances in UK will increase in incoming years. This is due the decreasing system inertia and increasing maximum generation loss in the system. Therefore, ROCOF protection will require higher setting to prevent unwanted operation while still ensuring correct detection of LOM condition. This paper proposes risk assessment analysis as a technique to find optimum setting which aims to minimise the risk of protection malfunction. The analysis use predicted Great Britain power system generation mix for year 2020 with gone green scenario. The study has successfully found the optimum setting of the ROCOF protection which provides minimum overall risk under specific assumptions. The recommended setting is 0.5 Hz/s with operating time-delay 500ms.