  This paper discusses the stability assessment of low-inertia power systems
through a real-world large-scale low-inertia system, namely, the All-Island
power system (AIPS) of Ireland and Northern Ireland. This system currently
accommodates world-record levels of system non-synchronous penetration namely
75% (planning to increase to 80% next year). The paper discusses one-month
results obtained with the state-of-the-art stability tool called look-ahead
security assessment (LSAT). This tool carries out rotor-angle, frequency and
voltage stability analyses and is implemented in the control centres of the
transmission system operators (TSOs). The paper shows that, at the time of
writing, the main binding stability constraint of the AIPS is related to the
limits on the rate of change of frequency (RoCoF).
