[RFI] Crepe Myrtle growing into power pole RFI Why?

[Mike Martin]

Chuck, the ground wire is not energized the hardware that it comes in contact with is energized. All the hardware on the pole is energized by the induced voltage from the primary conductor at the top. The closer to the primary conductor the hardware is, the higher the level of induced voltage. When the ground conductor is close enough to the energized hardware around it the gap between the two breakdown from stress and the spark occurs. The smaller the Gap the more times per half cycle the discharge occurs, the larger the Gap the fewer times it can discharge per half cycle. That's one of the components that creates the specific signature for a noise source.

As for the crepe myrtle, you can eliminate that as a cause of your RFI even if it were touching the primary. You'll get ultrasound and audible noise but you will not get rf. Contrary to what many people say about finding their sources as trees touching the line, I have never had a tree arching to the wire creating RF noise. If the crepe myrtle gets within a couple of feet of the primary turn it into your utility and they'll take care of it.

⁣Be safe,
Mike
www.RFIServices.com

On May 24, 2021, 3:24 PM, at 3:24 PM, Charles Plunk <af4o at twc.com> wrote:
>To answer my own question I am guessing that dirt around the fused 
>disconnects insulator allowing enough flow to arc to ground. And the 
>crepe myrtle with its moist branch this time of year and deep roots 
>provided a better ground than the util ground thus the arc.
>
>
>On 5/24/21 2:13 PM, Charles Plunk wrote:
>> If you have been following my latest saga, I have a 3 phase pole at 
>> the corner of my back yard and another (both wood) in the front yard 
>> topped with 3x 7.2kv lines. Weeks ago I located an arc on the back 
>> pole through the usually methods and finally seeing it with
>binoculars 
>> in the dark. Power co fixed, it was the ground wire stapled to the 
>> pole to close to a bolt which mounts the fused disconnect. They
>simply 
>> moved the wire away and re-stapled. It is gone.
>>
>> I had a 2nd arc on that pole but on the opposite side. It has all but
>
>> disappeared on its own with higher humidity. I suspect it will return
>
>> in the fall but ultrasonic tended to site on another part of the same
>
>> ground wire.
>>
>> Fast forward to 2 days ago, I begin to hear another strong arc. But 
>> this one is on the front yard pole. There is a crepe myrtle (~20-25' 
>> high) that has begun to grow around the pole but nowhere near the top
>
>> 3 phase. Using my ultrasonic I heard it best lower on the pole where 
>> the crepe myrtle is around and probably touching the ground wire.
>>
>> My question is, why is a wire at ground potential arcing to hardware 
>> insulated from the 7.2kv or to a crepe myrtle on either pole? Those 
>> ground wires go all the way to ground stapled to the pole uninsulated
>
>> where anyone can touch them. I am glad to locate these rfi sources
>but 
>> trying to wrap my head around why?
>>
>> 73
>>
>> Chuck
>>
>> W4NBO
>>
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