This article presents an application example of online DSA technology in performing near-real-time security assessment of the power system that covers Ireland and Northern Ireland. It is a single synchronous system that has limited HVDC interconnection to Scotland. The combined maximum and minimum demand of these two systems is approximately 6,800 and 2,500 MW, respectively. Tripping of the largest generator (440 MW) can result in a frequency fall of more than 0.6 Hz even with a primary fast-acting operating reserve of 75% of the maximum in-feed. The relatively small size of the system also dictates frequency variations wider than those in continental Europe under normal conditions. Generation plant (installed capacity) is mostly thermal, with some 6% of hydro and hydro pumped storage and a 16% wind share that is increasing rapidly. An additional 500-MW HVDC link to the U.K. grid based on voltage source converter (VSC) technology (due for commissioning in 2012) is expected to improve the power system's ability to accommodate wind generation. Increased wind penetration changes the operational characteristics of the power system, primarily due to the unique nature of the wind generation technology described earlier. Increased levels of wind generation introduce new risks and challenges for the transmission system operator.