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CATV Shield to GEC voltage #179204
07/01/08 09:07 AM
07/01/08 09:07 AM
Tom  Offline OP
Member
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
After a recent storm, the CATV drop to a customers house was replaced. Customer told me the installer did not hook up the required bonding conductor (shield to GEC) because it arced when he touched it to the grounding electrode conductor.

I stopped by this morning, no arc or spark when I touched the jumper to the GEC. Voltage measurement from shield to GEC varied from .5 volts to 1.1 volts as I had the customer turn on lights in the house. I suspect this reading is the voltage drop in the neutral. House is connect to transformer by about 100 feet of triplex & single conductor and there are four other houses on the same transformer.

I measured my own house & had about .3 volts, but I'm the only load on the transformer and have a very short drop.

Are the readings reasonable or is further investigation needed?


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Re: CATV Shield to GEC voltage [Re: Tom] #179211
07/01/08 11:17 AM
07/01/08 11:17 AM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,287
Estero,Fl,usa
There is no better example of the "all paths" parable than in neutral current. It really becomes complicated when you have wye distribution. The only answer is bonding, lots of bonding. Back in the olden days when the metal water system was a city wide bonding grid this was minimized but these days every house is it's own "earth". Ground ain't "ground" in any practical sense.
I measured the pole ground current on every pole on my street and got from less than an amp to over 8. My GEC is carrying about 3 with the main breaker off, about the same as the pole in front of my house. I may have the best ground electrode on the street tho (in ground pool). I do make sure I bond everything I can, every chance I get.


Greg Fretwell
Re: CATV Shield to GEC voltage [Re: gfretwell] #179295
07/05/08 07:17 AM
07/05/08 07:17 AM
D
drum  Offline
Member
Joined: Sep 2007
Posts: 14
USA
Have seen this voltage on ground problem many times with catv. Most times it has turned out to be a bad underground neutral. Had an entire street all underground fed with the cable drops melting due to this. Power company had to send out " power quality " troublshooters to find the problem and sometimes it takes several visits and can be a real pain because these problems like to be intermittant. Sometimes you will see voltage issues when you do a load test. Good luck

Re: CATV Shield to GEC voltage [Re: drum] #179298
07/05/08 01:00 PM
07/05/08 01:00 PM
S
SolarPowered  Offline
Member
Joined: Jul 2004
Posts: 625
Palo Alto, CA, USA
There are CATV isolation transformers available to mitigate this problem. Jensen sells one ($$$). This is a decent solution if ground differences between your TV and stereo system are causing hum.


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