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Is measuring tower footing resistance still considered an effective strategy for preventing back-flashovers during lightning strikes in modern transmission systems?

Srujan

Lightning is one of the primary sources that cause failure on overhead transmission system. It is one of the most natural and serious cause of over voltage. These over voltages will result in flashover across an insulator and the resultant fault surge will tends to ‘damage’ and reduce the life span propagate along the line until it is extinguished, or the breaker operates. This movement of the surge currents of associated equipment such as circuit breakers and transformers and impacts network performance adversely.

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    Not really my area, but to get the discussion going...

    I suspect it depends on where in the world you are - local practice often develops in response to local factors and historical conventions as much as the laws of physics. In the UK for instance steel lattice towers (pylons) are joined by an Earth wire running above and parallel to the main cables - so every tower is connected to Earth in parallel to every other tower on the route (and likely earthing systems of the network fore and aft as well), giving a very low overall impedance to Earth and the resistance on any one tower is almost irrelevant.  Less high voltage lines, typically carried on wooden poles, don't have an Earth wire at all, nor 'horns' across the insulators, but you will see spark gap arrangements on a few poles, presumably to a local electrode.I've a feeling that the network operators also take precautionary action when thunderstorms are forecast - e.g. by closing as many isolating points as possible, so to introduce many parallel paths in the network, thus helping to dissipate any surges. The UK does have a relatively low level of lightning activity though, so other parts of the world might find different approaches more practical.

       - Andy.

  • 0 in reply to AJJewsbury

    Hello Andy:

    My local area is supposed to be the Lightening capital of the US.

    All the local TV stations have weather news segments that include "live" radar scans that can show and count lightening strikes, as they move, usually from west to east across Florida..

    The rocket launch pads at "The Cape" all have lightening protection Towers .

    If "The Cape" live radar shows lightening within a certain defined distance from the launch pad, then the rocket launch is aborted.   

    Peter Brooks

    Palm Bay 

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  • 0 in reply to AJJewsbury

    Hello Andy:

    My local area is supposed to be the Lightening capital of the US.

    All the local TV stations have weather news segments that include "live" radar scans that can show and count lightening strikes, as they move, usually from west to east across Florida..

    The rocket launch pads at "The Cape" all have lightening protection Towers .

    If "The Cape" live radar shows lightening within a certain defined distance from the launch pad, then the rocket launch is aborted.   

    Peter Brooks

    Palm Bay 

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