Among the consequences arising from the displacement of large synchronous generators with renewable non-synchronous forms of generation like wind, is a reduction in system inertia. This in turn, means that for a given disturbance on the power system, the frequency will vary more and at a faster rate than previously.
This has a particular relevance for distribution connected generation since ESB Networks, like most utilities, has traditionally used Rate of Change of Frequency (ROCOF) as a means to detect the occurrence of local islanding, for which the generator needs to disconnect. To cater for these variations in frequency, in a renewables dominated grid, a new threshold of 1 Hz/s for ROCOF has been mandated. The issue now is for a system wide event of up to 1 Hz/s, most distribution connected generators, set to disconnect at 0.4-0.6 Hz/s, would also disconnect and exacerbate the issue, which could ultimately lead to a black out.
This project entails the implementation of settings changes to generator protection on generators across the distribution network to 1Hz/s, so that generators will stay connected to support the grid during system wide frequency events and are still able to detect local islanding events. These changes are a matter of compliance with the Distribution Code and must be complied with by the generator owners. This programme will ensure that we increase system frequency stability, maximise the benefits from renewable generation and deliver on Ireland’s targets for Renewable Energy Supply – Electricity (RES-E) for 2020.