Stockport - study of YO8 terminal pylon

[pendragon]

Earlier this year I thought I would go and have a look at a local terminal pylon.

The route is at the end of a short run between the sub-station at Bredbury and Stockport town centre, where it runs underground for a while.
I was curious to trace the route of the cable and had noticed a couple of Gas pipeline markers nearby and was wondering if they were being used to mark the cable route.

This is the back of the pylon taken from the bridge over the M60. The motorway was built alongside an old railway line which ran where the
hedge is next to the carriageway.
www.flickr.com/photos/37217530@N04/3424947472/

There are a few remains left of what was Tiviot Dale Railway Station:
www.flickr.com/photos/37217530@N04/3426795249/
www.flickr.com/photos/37217530@N04/3427604072/
www.flickr.com/photos/37217530@N04/3427603854/

Here is YO8 in all it's glory
www.flickr.com/photos/37217530@N04/3425042036/

We're very close to the approach glidepath to Manchester Airport here
www.flickr.com/photos/37217530@N04/3427592608/

Various views of the terminal gear
www.flickr.com/photos/37217530@N04/3426719679/
www.flickr.com/photos/37217530@N04/3426719789/
www.flickr.com/photos/37217530@N04/3427528852/
www.flickr.com/photos/37217530@N04/3426764919/
www.flickr.com/photos/37217530@N04/3426719931/
There appear to be two cables emerging from the terminals, one fat one presumably carries the current, but
what's the other one for?
www.flickr.com/photos/37217530@N04/3427573846/
One's chipped too
www.flickr.com/photos/37217530@N04/3426783345/

A gas main runs past the pylon
www.flickr.com/photos/37217530@N04/3426783571/
with appropriate markers....
www.flickr.com/photos/37217530@N04/3458135279/
www.flickr.com/photos/37217530@N04/3427574566/
Curioisly there seems to be no indication of an underground cable, despite plenty of gas pipe markers

In the scrub alongside the pylon is a pile of empty paint canisters and a roll of thick copper cable
www.flickr.com/photos/37217530@N04/3426766155/
www.flickr.com/photos/37217530@N04/3426765083/

Presumably the gas pipe and cable run alongside each other up a steep hill...
www.flickr.com/photos/37217530@N04/3458135753/
www.flickr.com/photos/37217530@N04/3458950858/
and under a pub carpark
www.flickr.com/photos/37217530@N04/3458135919/
beside the pub (behind the tree) is this cabinet
www.flickr.com/photos/37217530@N04/3458136153/
www.flickr.com/photos/37217530@N04/3458136283/
www.flickr.com/photos/37217530@N04/3458136453/

I can only assume that the pipe and cable run up this hill
www.flickr.com/photos/37217530@N04/3458136081/
there are more gas markers, but no sign of any warning of several thousand volts beneath the road.


These pics were taken a few months ago; today I went to have a look at YO7, which you can see here..
www.flickr.com/photos/37217530@N04/3426762521/
which in itself is a very interesting beast, more of which very soon.

[naughtyhorse]

Hi Pendragon,

A few quick answers (like i have ever given a quick answer to anything!)

in img_1851
judging buy the colour of the corrosion that is a steel cable (copper oxides are black or bright green and ali has a white powdery oxide), and not used on OHL's the resistance of steel is too great, it is used inside some - usually older - conductors to provide strength. but the steel is always inside the conductor.

in img_1848
the thinner wire is the high frequency earthwire. where a transmission line changes from overhead (closer to where the lightning is at) to underground (where the lighting wants to be) we need to take special precautions to ensure that any voltage spikes from a lightning strike get efficiently conducted away to earth and not into sensitive substation equipment, or valuable cables. A lightning strike is a high voltage which rises very quickly. This is an older design which relies on arcing horns - you can just see the bottom terminal in the photo the vertical bar with a ball on the end - the idea is that the lightning strike induces such a high voltage that the air between the electrodes of the horns breaks down forms a plasma which conducts a current down into the thin HF earth wire, which provides a low impedance path to earth. Because of the physics of high frequency electronics you have to be careful about providing a straight path, too many bends or any corners and it wont work at all well so HF earthing is usually carried out as a separate exercise on term towers (but the HF and power frequency earthing are usually joined up below ground level)

Modern designs use surge arresters instead of arcing horns which sit next to the sealing ends on the sealing end platform with the wires coming down from the overhead lines onto them first. The other end of the SA is connected to earth via the HF earthing. surge arresters are a semiconductor which has a high resistance to low voltage (132kV is low in this example) but a low resistance to high voltages so the high voltage spikes get conducted to earth through the surge arresters and HF earthwire to ground.

[blueshift]

The cable route can be seen here
www.nationalgrid.com/uk/LandandDevelopment/DDC/GasElectricNW/undergroundcables/

albeit in fairly low res - the map you want to select is SJNE

Nice pictures - this has been on my list of pylons to visit, just havn't managed to find the time yet

Nick

[yv47r]

Looking at the routing of the cable from YO 8 to ZO 9 at the western end of the route, I believe that that the cable feeds into the Stockport-Manchester railway like overhead 25kV electrification somewhere near Heaton Norris Junc to the north of Stockport. I was told this many years ago and there is a neutral section between the Stockport feed and the Manchester feed. In fact I have a good way of detecting the buried cables!! Yes my handy hearing aids if set to the T or induction coil setting will happily pick up the 275kV buzz of the buried cables.

I believe the Stockport feed is near to Edgeley - its on the right hand side as you leave Stockport heading south towards Cheadle Hulme by train before the first overbridge having passed Stockport County's ground.

YO 7 is special in that it splits the single circuit into two circuits then takes these via the cables across to YO 9 (I think thats its ID can't remember right now!)

Cheers Paul

[blueshift]

The 25KV feed to the railway is actually from United Utilities Edgeley 132K Substation.

Edgeley Substation is, itself fed by underground 132KV cable from National Grid's Bredbury Substation

Nick

[yv47r]

Ah you learn something new each day!! It does seem coincidental that the 275kV cable passes over or under the lines near to Heaton Norris Junction and Penny Lane overbridge. I will ask the chap who used to work for the BR signalling dept to see if he can confirm or not. Plus there are some red brick buildings just to the north west of the overbridge as you are heading north from Stockport, not sure if they have anything to do with it.

I've downloaded each of the plans for reference plus the national grid square maps on the same site ;D

There is also another minor variation in that the YO route between towers YO 2 and YO 5 were at some point realigned with new replacement L2 towers. I'd have to dig my notes out but from memory YO 2 was originally a D30 then became YO 2R D60, YO 3 was a D now a YO 3R D30, YO 4 was a D60 now YO 4R D and YO 5 was a D now YO 5R D90, then it rejoined the original course at YO 6 D30 then to YO 7 D60 and ending with the afore pictured YO 8 DT. I first noticed the change between two editions of the OS 1:50,000 maps one dating from the 80s the newer one from the 90s. Not sure why they were altered, only thing I can think of was the old M63 now M60 motorway, whether that forced them to change the route?

Eee pylons don't you just love em' ;D

[pendragon]

Here is the second installment.....

YO7 is a bit different from your typical deviation tower, as signalled by the additional notice:
www.flickr.com/photos/37217530@N04/3744496252/

www.flickr.com/photos/37217530@N04/3744493978/
www.flickr.com/photos/37217530@N04/3743697439/

The tower sits on a patch of waste ground alongside the River Tame; I think it's the site of a landfill.
www.flickr.com/photos/37217530@N04/3743696263/
www.flickr.com/photos/37217530@N04/3743695883/
www.flickr.com/photos/37217530@N04/3743695231/


As mentioned above, only one of the circuits between here and Bredbury is live, the cables of the circuit on the nothern side are bonded directly to the pylon. On the western side of the tower, the three cables are linked by a conductor running between them.
Here's several shots...
www.flickr.com/photos/37217530@N04/3744488066/
www.flickr.com/photos/37217530@N04/3744486896/
www.flickr.com/photos/37217530@N04/3744485254/
www.flickr.com/photos/37217530@N04/3744485588/
www.flickr.com/photos/37217530@N04/3738497129/
www.flickr.com/photos/37217530@N04/3738495495/
www.flickr.com/photos/37217530@N04/3744493546/

Interestingly there are both porcelain and glass insulators on the tower
www.flickr.com/photos/37217530@N04/3743694813/

There are a load more piccies of this beastie on Flickr for anyone who's interested. Enjoy!

[blueshift]

Excellent pictures of the connections on YO7. I have puzzled before over Nat Grids system diagram which seemed to show a single circuit that doubled up as it crossed Stockport. Your pics have solved that mystery.

Pylon goodness indeed !

Nick

[jpskertchly]

Wonderful picture of the terminal pylon . This is what I really love to see . I love underground cables and terminal towers / sealing end compounds are my favourite. This is what I used to work on . Terminating cables like this was my " speciality " and what I love. Itd be nice to see a pic of someone standing near this to get a better idea of its height / size. I wish we had some nice terminal towers / sealing end compounds around here near us.
These underground cables are fluid ( oil ) filled paper insulated lead sheathed type and the small cable you describe coming out of the bottom of the termination is an oil line not a cable. Have a close look and see if it has a wiping gland ( like a miniature version of the cable gland ) on the bottom of the termination. Inside the termination the cable conductor is clamped and sweated into a long copper collar with radial slots in it that allow the oil space in the centre of the conductor to communicate with the inside of the termination. The whole lot is filled with oil. Somewhere not too far away there will be a cabinet or cubicle with a set of oil pressure gauges in it , which is where those oil lines go.
The idea is that these are kept an eye on for drops in pressure , in reality theyre probably rarely checked and the box and gauges are probably in a poor old state.

Thanks again for super pics JPS.

[jpskertchly]

Oh dear , I must sound stupid! . Ive found the picture of the oil gauge cabinet ( I knew there was one not far away !). Sorry about that . I posted that last comment before Id looked at all the pictures . ( I havent looked at them all yet ! ).
Ive not long got up and running on the site and Ive been spending far too long on it ( no works been getting done here ) . Im especially enjoying all these pylon pics- cant get enough of them - but there are so many . I have to stop at some point and break off now and again.

Thanks again , JPS.