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SEM Chart of the Week


Inertial dampeners – power system frequency management

Joe Camish Analyst

A challenge for a system with 70% renewable electricity, as posited in the Climate Action Plan (CAP), will be managing frequency. This is important as if frequency veers outside certain limits it increases the potential for generators to trip or parts on the network to start to black out. Recent experience of our neighbouring market, Great Britain (GB), suggests those challenges may have to be faced in the near term. GB experienced two frequency events during 11 July, which saw system frequency fall below the operational limits the system operator works between. In this week’s SEM Chart of the Week we look at this event in more detail and highlight some considerations relevant for the Irish system. The Prime Directive National Grid ESO has a statutory obligation to economically balance supply and demand second by second – achieved through frequency management. This sees the ESO aim to maintain system frequency 0.5Hz above or below 50Hz, acting as a buffer the system also has operational limits of ±0.2Hz that it works to. For comparison, frequency of the all-island transmission system is 50 Hz, with EirGrid and SONI operating frequency within the range 49.9 Hz to 50.1 Hz. This is a ±0.1Hz tighter range compared to GB. The system operator has as target to operate between these frequency bands for 94% of the time. According to Transmission System Performance Report 2018, the system frequency was within the agreed limits 99.7% of the time. While in Northern Ireland, SONI is required to report on system faults where ...

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