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#213374 - 04/17/14 12:30 PM Zapped on cable line  
sparkync  Offline
Member
Joined: Oct 2002
Posts: 817
NC
Just wanted your input on the theory behind this. My son works for a cable company and troubleshoots and installs cable lines. He was up a pole the other day, and was making his cable connections, and got zapped big time when putting the 2 ends together. He said the customer had issues of tv frying, microwave gone bad, etc. etc... I told him to check the line coming into the house and check for a broke neutral. After getting himself together after the shock, he followed the power line, and sure enough the power line neutral had been snapped into. Obviously the house had lost it's ground and the voltage had spiked and fried the normally 120 volt appliances etc. The cable line was probably tied to the ground at the meter. I told him to call the local power company. I've seen this happen several times on different jobs. On one job the power company replaced the customer's appliances.
In theory, what is actually happening here. The unbalanced load being carried over on the other phase??

Just thankful he didn't get hurt any worse. It was wet and rainy that day.
Thanks

Last edited by sparkync; 04/17/14 12:34 PM.

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#213376 - 04/17/14 01:17 PM Re: Zapped on cable line [Re: sparkync]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,069
Estero,Fl,usa
It sounds like that when the neutral opened the current went looking for other paths to the XO. The cable seemed to be an attractive one since it is usually grounded at the Dmark which should be connected to the service ground electrode and again on the strand on the pole.
I also bet the ground electrode is not that great.


Greg Fretwell

#213379 - 04/17/14 05:32 PM Re: Zapped on cable line [Re: sparkync]  
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
If he's on a pole -- then assume it's an older system -- and that at some point plastic has been inserted into the plumbing.

This is as common as dust.

No plumber is going to think twice about breaking your GEC system in half, crippling it.

Bam!

The residence is an ungrounded Service. Every manner of trouble soon follows. This may include feeding back onto the Service neutral/ return with harmonics.

(Never anticipated by EEs back in the day, either.)

So now the Poco neutral (aluminum) starts to cycle (really) hot and cold until it fails.

[FYI, because of transient harmonics, it's actually possible for the neutral to carry MORE than the original (unbalanced) current.

Why?

Because, for a micro-second, nothing's balanced at all. High order harmonics can create peak amplitudes entirely out of the range of normal conception.]

It was for this reason that EUSERC banned ungrounded Services -- in 1945!

What was happening -- even back then -- was that highly inductive loads (machine shops supplying the war effort) with failing transformers (autoformers) and capacitors could and would kickback astounding instantaneous voltages. These micro-second peaks were enough to breakdown the insulation (corona discharge) into a cascade of trouble.

This vile trait was unique to ungrounded Services. A Ufer would bleed off these peaks -- straight into the earth.

&&&

In sum: expect to find fouled up neutral paths all over pre-Ufer America. Any Service that was established when bonding to the water service was considered good-to-go for a GEC is going to be 'sabotaged' by the plumber/ DIY at some point. Then "katie-bar-the-door" -- you've got trouble.

&&&

So, as a heads up, ANYONE working Co-ax data-com in older neighborhoods has to be aware that it's only a matter of time before he gets zapped by corrupted GEC systems -- and their bonding to the data-com ground.

(These used to be kept un-bonded -- until it was discovered that a single lightning strike can burn down the entire structure -- regardless of size -- in seconds. Tales of this (Florida multi-family) fiasco are in the back literature.)

Last edited by Tesla; 04/17/14 05:32 PM.

Tesla

#213381 - 04/17/14 06:49 PM Re: Zapped on cable line [Re: sparkync]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,069
Estero,Fl,usa
The cable and power are still on the pole here in most of Florida unless there was a recent utility upgrade. Newer gated communities got underground services but the distribution up to their gate is still likely to be overhead.
The only thing buried in my neighborhood is the phone.

People are starting to understand bonding and grounding are very important for lightning mitigation. Ufers are now in the code but older homes are still sitting on pretty lousy ground electrodes most of the time. My house was floating when I got here and the first day I tried to use the cook top I got zapped. I was at the supply house buying a couple ground rods the next morning.
Every significant chunk of concrete I have poured since was incorporated into my GES.


Greg Fretwell

#213391 - 04/21/14 09:49 AM Re: Zapped on cable line [Re: sparkync]  
harold endean  Offline
Member
Joined: Feb 2002
Posts: 2,233
Boonton, NJ
I was inspecting an older home in one of my towns last year and the homeowner was doing everything himself. When he got to his water line, he cut it in several spots (hot and cold) and installed anywhere from 8 to 12 pieces of plastic water pipe because he had to remove the copper in order to install beams, lights, duct work, etc. So as I was looking around I mentioned to him that he broke his ground of the water pipes. He asked how to fix it and told him he would have to install jumper wires from hot to cold on every piece of plastic that he installed in order to make sure that his copper water lines on the second floor were properly grounded.



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