Tag Archives: transmission

A problem in trigonometry

I mentioned the other day that extensive searches of tinterweb had failed to find any data on the heights of overhead power lines above the Shannon and that I had been forced to resort to the telephone.

I am pleased to report that the ESB expert duly rang me back today, and further pleased to report that he had himself measured the height of every cable over the Shannon. Oh joy, oh happiness, I thought. But not for long.

The ESB, it seems, does not reveal the actual height of power lines above the water. This, if I understood the reasoning correctly, is because the water level varies and a boat-owner might not understand that, hit a line with a mast and then sue the ESB [where “ESB” means “electricity transmission or distribution operation”]. I have been told that a boat-owner in coastal water did just that (presumably between the mainland and an island) and that the lawyers have advised ESB to take no further risk; I would welcome information about the incident.

So, if you want to find the height of a power line, you’ll need to polish up your trigonometry (and then relate the height to Ordinary Summer Level). But the ESB does supply the information to one organisation that makes charts: the United Kingdom Hydrographic Office. That’s OK for coastal charts, but the UKHO (to the best of my knowledge) has not surveyed the inland Shannon since 1839, and I don’t think its inland charts have been updated since then. It is possible, of course, that the UKHO supplies the data to other (electronic or paper) chart-makers; I have emailed them to ask.

The quest continues again. More info when I get it.

Power to the people

So you’re out in your sailing-boat, heading for Portumna, and you see that there’s an electricity cable crossing the waterway ahead of you, just downstream of the bridge. You think you’ll fit under it but it would be nice to know the clearance ….

Electricity is ESB, isn’t it? Well, perhaps not: it could be ESB Networks, which seems to mean distribution, or EirGrid, which means transmission. It could also be one of the other companies that sells volts, but I don’t think they run big wires.

Half an hour of searching the websites of the three bodies failed to produce anything about the heights of pylons or cables or overhead powerlines. Safety advice said not to go near them, but that’s what you are trying to do: it would help to know how near is near. Another half an hour of general googling; still no result.

So, as it’s a smallish line on wooden poles, rather than a large one on very tall steel pylons, you guess that it might be distribution rather than transmission, and thus ESB Networks rather than EirGrid.

I rang; someone will ring back within 48 working hours. The quest continues ….

What is the magic combination of search terms that will find the heights above water of all power lines over Irish waterways?