So I'm back again, randomly posting on this blog after a few years, about another new topic… This time, the topic is historic electricity infrastructure in Ireland.

As part of the Shannon Scheme almost a century ago, a 38-kV transmission network was built around the then Irish Free State, in four loops. This network was fed into by 110-kV transformer stations at Ardnacrusha (the hydro station), Kilbarry (Cork), and Inchicore (Dublin), and in turn fed into a 10-kV distribution network at sixty-five strategically-placed substations around the country. The map of these stations can be seen in the 1930 ESB Annual Report, available (together with all the others) from the ESB Archives website.

These sixty-five stations were built according to a standard template, involving a "power house" containing 38-kV switchgear on one side and 10-kV on the other (which voltage was left or right varied from site to site), and a small control room at the back. The switchgear was all supplied by Siemens-Schuckert, and has proven itself very robust, as many of these houses were still operating right up to the 2010s, and some even into the 2020s.

However, all equipment must eventually reach the end of its service life, and there are now only a few such houses left in commission. One of the last remaining stations, in Rathkeale (known as "Kyletaun") was fully retired from service just last week. Like many of the other houses, its transformer capacity had been increased to 10 MVA over the years. Most of the outlets had also been upgraded from 10 kV to 20 kV, by installing three step-up interface transformers in the yard and using extra reclosers to switch the higher-voltage feeders.

The 10-MVA transformer capacity appears to have represented an absolute maximum for the 10-kV switchgear in these old power houses, as the only stations that surpassed this (Balbriggan and Bray) have replaced the 10-kV side entirely, while still using the original 38-kV gear. In one way, this 10-MVA switchgear rating represents pretty impressive future-proofing: when the stations were first built, the total transformer capacity across the entire 38-kV network was a mere 53 MVA, i.e. an average of 0.8 MVA per station! However, in more recent years, the area served by Kyletaun frequently scraped this ceiling at peak demand.

Now the region has been moved over to a more streamlined setup, with 20 MVA of 38/20-kV transformer capacity installed in the nearby Rathkeale 110-kV substation, as well as two step-down 20/10-kV interface transformers. The latter transformers serve Rathkeale town, whose supply had never been upgraded to 20 kV.