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I saw this unusual transmission tower (pylon) while cycling recently:

This is in the UK. Specifically, it's just off the A6, between Preston and Lancaster.

The simple hanging attachments are very common, and the ones with a loop of wire are common too. But I've never seen one that is a mix before. There must be some specific reason it was constructed this way - any idea why?

paj28
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3 Answers3

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It appears from your photo that the lower lines have been raised to clear the roadway below.

  • Note that the lower lines require two insulators per phase whereas the upper ones only require one. There is a cost saving to only applying this style to the lines that require it.
  • The lower lines also require two splices - one at each end of the loop - whereas the upper ones can be clamped by the fixing at the bottom of the insulator. I imagine that for installation all the wires are drawn through pulleys, transferred to clamps and the bottom one clamped by the horizontal insulators before being cut and looped.
  • Each of the horizontal insulators on the bottom lines are approximately the same length as the ones on the upper lines. This is to be expected to maintain breakdown voltage between the lines and the earthed frame of the pylon.

You may be interested to know that Britain has a Pylon Appreciation Society!

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Figure 1. A simple straight-through clamping arrangement. Notice the Stockbridge or tuned-mass dampers each side of the insulator. Source: Wikipedia Commons.

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Figure 2. The horizontal insulator arrangement is more commonly seen on turning pylons. Source: Pylons.org.

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Figure 3. "CHECK IF THE LIGHTS ARE WORKING NOW!" An insulator in tension.

Transistor
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  • Good additional information. In the situation I described in my answer there was no appearent reason like this. I will look if they also have a Pylon Appreciation Society in the Netherlands. – Decapod Sep 26 '16 at 21:31
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Special situation

In the Netherlands we find the same situation. On a specific site concerning highvoltage transmission lines they indicate that it is sloppy work thereby disturbing the image in the landscape. So there seems not to be any specific reason for this other then that someone on the drawing board did not give the system full attention as might be expected.

Not completely satisfied with my own answer I contacted TENNET the resposible party for this in the Netherlands. The answer I received was: If required adjustments are made to the lines, based upon the standard, optimum technology and most safe soluting. In this case it results in the lines being +/- 0,8 m higher.

The contracter is not to blame here because he only executes the work he has been given.

Community
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Decapod
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    Someone placed a downvote on my answer. I do not have any clue why? I have asked TENNET in the Netherlands to give further information on this subject. Expect an answer in about 10 days – Decapod Sep 28 '16 at 08:15
  • I modified my answer due to the response received from TENNET the Dutch responsible party – Decapod Sep 29 '16 at 18:00
  • -0,8 m higher? ;^) Good job getting a response from them though! – Transistor Sep 29 '16 at 18:33
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When greater surface or overhead crosswind forces, deadends, or sharp corners exists, a "Strain Insulator" method is used , which cost more to install and repair. enter image description here

But as far as tower design , these next ones are curious. enter image description here

Below is an artist's rendering

enter image description here

Some of the requirements for Tower design are;

Cost of tower & installation of cables, cost of property from cone angle projection and height, mechanical and electrical properties with environment.

Tolerance to cable resonance:

  • susceptibility to resonance and need for detuning, or inter-phase connections
  • fixed tower connections with loop bypass bushings
  • flexible suspended bushings with a sway arc angle
  • fundamental, 2nd 3rd, swing

Tolerance to cross-winds

  • Tower tilt tolerance 5, 10, 30 deg
  • cable sway relief
  • ground clearance
  • tower clearance
  • tower tilt resistance

Tolerance to ice accumulation and cross-winds

  • ease/cost of single or array stringing power line repairs

These are more traditional enter image description here

Tony Stewart EE75
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