Overhead power line height rules need safety update, say farmers

I cannot quite see the National Grid replacing all the pylons and poles with taller ones.

The new pylons and cables running to Bristol Docks through Somerset actually look lower to me.

The article has the following statement:

Lines that have up to 32 kV of power must have a minimum ground clearance of at least 5.2m,

BS 7671 (Regulation 705.522) requires (and has for some time) BOTH 6.0 m height for suspended for LV cables (i.e. scope of BS 7671) in agricultural premises, and additionally all overhead lines to be insulated. Of course, cables in the scope of BS 7671 are well below the voltages being discussed.

The cables in question are DNO/TSO cables, which are required to comply with Regulation 17 (and where specified Schedule 2) of ESQCR applies.

Given this disparity, and the fact people are dying, perhaps it really is time for a debate on the issue.

As I recall there was a suggestion a few years ago that 11kV and 33kV lines could be insulated - it was dropped due to cost concerns. I suspect that the best that could be done would be to look at those that crossed roads and farm yards with a view to an uplift or insulation - there are just too many miles of the stuff to do anything quickly- the mean time to replacement is probably more than half a century once installed so any  rolling programme will outlive whoever starts it...

I also expect that a lot of in-service lines do not even meet the original height spec - land levels alter as things are ploughed, and ground is graded,  spans droop over time or pole shift a bit, and a multitude of other factors.

It is tragic and impressive when it goes wrong, but it is still very rare. The fastest short term is to publicise what it should look like and get farmers etc to self report if the lines over their land look a bit loopy

Given this disparity, and the fact people are dying, perhaps it really is time for a debate on the issue.

I'd agree with that. As a first step it would seem sensible to treat arable farm land in the same way as a road.

   - Andy.

indeed - but unless folk call in the dodgy sections, any rule change will only affect the new stuff - a very small fraction of the total.  I must say that the idea that 8 inches holds off the difference between 66kV to 33kV and 11kV down  to LV seems a bit silly - on that basis it could all be 'nominal 6 metres' and easier to remember and not make much difference at all.
Equally if the combine  harvester is really is 5m tall - are they really? then unless the uplift is dramatic - pylon sort of dramatic, rather than taller trees,  it  is not going to help a lot. Also I imagine a lot of farmers are pretty hazy on the actual line voltages of things crossing their land.

Mike

any rule change will only affect the new stuff

True, but that's true of most changes - from safety belts to RCDs - but nevertheless tempus does fugit.. While new lines might be relatively rare, wooden poles do seem to be replaced on a fairly regular basis (few decades)- so there could be a significant improvement in a sensible length of time.

I wonder if growing the trees higher to make the poles might be more of an issue (as well as taking longer, at some point they won't fit into the processing plants or transport vehicles).

   - Andy.

I've also heard/read that shrouded OHLs can cause an increased in downed lines due to lighting strikes: With bare conductors, once struck the arc will travel along the lines and spreading thermal effects along the length, but if insulated it can't so the arc effectively rooted, causing pin-point heating

well round here on the LV network, some of the droopier poles now sport an extension that looks to be aluminium or maybe a bright galvanized washing line pole type thing , that bolts onto the holes where the ceramic insulators used to go, and adds a metre or so, and then carries the LV  aerial bundle cables 'ABC' on top of that.
We have a lot of house feeds that cross the road to go to the eaves on bungalows and these pole extensions seem to be to raise the tall end  triangle a bit, and it gets done when the 4 wire singles get replaced for ABC - which is slowly working out from the town centre up the hill. As far as I can see the houses remain 2 wire TT, but the street cable changes, so in principle could be PME in future. (I'm sure it was supposed to be PME ready years ago, but like fused neutrals, let's just not ask..  )

I suppose a similar top hat idea could be engineered to replace the 11kV cross-bars with slightly taller metalwork without pulling out the pole or growing taller trees... We also have some 11kV where the wires are one above the other rather than side by side, I presume it has better wind-sway clearnace as it is only on exposed bits of the new forest.

Mike.

Hmm, without meaning to downplay the issue (as it's rather serious), this is nothing new

HSE guidance for farmers working new OHLs ... from 2012

Easy as it is to put this on the network operators, is this really an issue with the OHLs? Or, given that the hazard is well-documented is it an issue with underinformed/undertrained contractors carrying out insufficient risk assessments? After all in construction we have to consider the same hazard when for example selecting plant for lifting operations and erecting goalposts etc. I dare say isolated incidents occur in both industries, no doubt for similar reasons. I don't think legislation to raise the lines (by how much?!) throughout the land is the right answer, especially if expecting the cost of that to be socialised. For sure it's an item on the table during negotiations for wayleaves for new and refurbished lines.

What might help would be more accurate information to facilitate risk assessments where the clearances under maximum sag are clearly more than the legal minima. I find NGET quite good with swing/sag profiles through CBUD requests but DNOs tend to only have generic information (other than pole heights) particularly for wood pole lines.

Obviously if the lines don't meet the specified clearances thats a whole other story.

On the other hand, this article is more likely to make farmers think about it when planning this season than the perennial generic reminder.