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Why does high wind cause power cuts?

Andy Millar
May sound like a stupid question but then "there's no such thing as...". Is it typically because the phases in a three phase line touch? Or because branches blow into the lines and arc across? Or sometimes one thing, sometimes another?


Google let me down, so posting this - in one of those brief intervals when we do have power today :) It's the fact that what ever is causing them is obviously easily resettable - by the rate ours has been going on and off today - that made me start thinking about it. (It's on the HV lines affecting my village and half the adjacent small town. But not, you'll all be relieved to hear, the Ginsters' pasty factory which is on the other side of town :D ) 


Thanks,


Andy
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    Andy Millar:


    . . . I must admit I was thinking more about root causes - and for example I hadn't thought about wet insulators. As you say, vegetation seems pretty likely. Sometimes it's just been off for a few seconds, sometimes for an hour or two . . . 




    There are many causes that are possible. The usual is trees or wind-borne debris. As Mike said, in the UK it is normal practice to fit reclosers to rural overhead lines. Many faults are transient, and are burnt off after the first or second trip, allowing the line to be re-energised successfully. Water on an insulator is not usually a problem. However after a period of dry weather or windy weather, the surface of an insulator can become contaminated by dirt or salt. The rain may then cause them to conduct. Past lightning damage can also produce a crack which will allow conduction in rain. 


    I need to correct Mike about Sensitive Earth Fault. This is typically set for a few amps, delayed for 20 seconds or so. The idea is that this stands a good chance of detecting a downed HV conductor. A recloser will be set so it does not reclose after an SEF trip, as you don’t want to re-energise lines on the ground. 


    Regards,


    Alan. 

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  • 0

    Andy Millar:


    . . . I must admit I was thinking more about root causes - and for example I hadn't thought about wet insulators. As you say, vegetation seems pretty likely. Sometimes it's just been off for a few seconds, sometimes for an hour or two . . . 




    There are many causes that are possible. The usual is trees or wind-borne debris. As Mike said, in the UK it is normal practice to fit reclosers to rural overhead lines. Many faults are transient, and are burnt off after the first or second trip, allowing the line to be re-energised successfully. Water on an insulator is not usually a problem. However after a period of dry weather or windy weather, the surface of an insulator can become contaminated by dirt or salt. The rain may then cause them to conduct. Past lightning damage can also produce a crack which will allow conduction in rain. 


    I need to correct Mike about Sensitive Earth Fault. This is typically set for a few amps, delayed for 20 seconds or so. The idea is that this stands a good chance of detecting a downed HV conductor. A recloser will be set so it does not reclose after an SEF trip, as you don’t want to re-energise lines on the ground. 


    Regards,


    Alan. 

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