Hot Ground

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I called the Power Co this morning they came out right away. Turns out that the clip that held the ground in the meter Pan had broken and the ground was touching the Hot Leg. This in turn was feeding 120v into my Service Panel as well as the cable. They replaced the clip, reattached the ground and it is good to go now.
Thanks for everyone's help and suggestions.
-a12vman
wrote:

The supplied picture makes things a lot clearer. What was being referred to as "the cable box", is actually the surge arrestor on the cable at the entrance point. Getting a spark and measuring 120V beteween the arrestor and the ground wire means one of two things:
A - The cable ground is actually hot because somewhere else it's contacting 120V, like back out at the street, neighbor's house, etc.
B - The cable is in fact grounded correctly and whatever the ground wire is connected to is not ground but is elevated to 120V. That could be occuring if the ground wire is connected to some other grounds, one of them is supplying the 120V due to some fault, and the ground wire does not have an actual ground to earth.
I would measure between the disconnected incoming cable and a good known earth ground seperate from the ground this ground wire is supposed to go to. A metal water pipe coming into the house would be one choice. Alternatively, you could drive a length of pipe or similar into the ground, apply some water as a temporary ground. Then I'd measure between the ground wire and the new earth ground. One of them is going to have 120V and whichever it is, you'll know who's problem it is.
The cable guy, having been there, should have determined this before leaving. Also, be careful, as you're obviously dealing with an energized circuit.
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a12vman wrote:

But are they going to credit all the false use?
steve
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snipped-for-privacy@optonline.net wrote:

I agree that A and B are the possibilities.
Some comments on possibility B: As I read the posts, the OP has only a ground rod as an earthing electrode. A rod is not a particularly good electrode. If the resistance to earth was a very good 10 ohms and there was a hot-to-"ground" short there would be a 12A current which would not necessarily even trip a 15A breaker. The rod is then at 120V with respect to "absolute" earth potential. The cable which is earthed elsewhere is at "absolute" earth potential (except for possibility A above). The voltage falls off rapidly away from a ground rod - about 70% in the first 3 feet (which means there could be electrocution hazard from the rod to nearby earth).
Ground rods are notoriously poor earthing electrodes, so the resistance to earth may be a lot higher, with much less current causing 120V. It is possible a lazy installer used a very short rod.
Since the problem is reported to be present when the service disconnect is off, the current is presumably not coming from the power service "hot" wires. But I see no reason why the meter would spin with the service disconnect off. That could be caused if the wire from the rod came loose and contacted a service "hot" wire before the disconnect. That is very unlikely. High current to earth could cause heating near the rod which you may have seen.
A problem with the service neutral connection back to the utility transformer could also cause current to earth. It should also disappear with the service disconnect turned off. (A problem with the service neutral would cause significantly different voltages from each of the 2 incoming power legs to the neutral with the disconnect turned on - measurement is hazardous).
There could still be current to earth via the service neutral with the service disconnect off - for instance a problem with the earth connection at the utility transformer and earth currents from other users.

A separate earth connection is a good approach. The OP doesnt have a metal water service pipe. A separate earth connection should be distant from the existing rod (10 feet?).
I would use a clamp on ammeter, but the OP probably doesnt have one. Current on the "ground" wire from the power service to the rod with the service disconnect off would be of interest. If it is relatively high (over 5? A) I would be interested in the service neutral current with the service disconnect off (measurement is hazardous).
=============If you have 120V with the service disconnect off you might just ask the power utility to check. I would guess the problems is on the power side (not cable) and most of the possibilities are utility problems. The utility probably would want to make sure they do not have a problem.

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wrote:

If the utility is using wye distribution there is going to be current on the grounding system. There is no way to avoid it. Current will take ALL paths and the earth will be one of them. I have an amp or so on my ground electrode system with the main breaker off and that is consistent with what I measure on the grounding lead on the poles on my street. (ranging from less than an amp to 2.83) The utility does not consider it a problem. It should be noted that the one with 2.83a is the pole where the cable system distribution amp is mounted so that could be their problem.
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snipped-for-privacy@aol.com wrote:

I was interested in much higher currents that could be produced by failures. But even 1 amp and a "good" ground rod resistance of 25 ohms could lift a house "ground" 25 volts above "absolute" earth potential.
Nice to have an idea what "normal" currents are. I never measured them.
Why do you get higher currents with wye? Because a single phase feeds several blocks and the return is longer? They use wired return, not earth return? If you have 2 distribution hots are transformers connected line-to-line?
================The ground potential at different locations is not the same. Since cable is earthed at each building there should be ground currents on the cable shield. Why doesnt that screw up the signal (particularly analog). Or can it be effectively removed with a high pass filter? (Seems like it could be rather low signal to noise.)
--
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wrote:

They use the "strand" for the neutral and usually a whole street (or in my case 2 streets) all get fed from one phase of the primary. If you do the voltage drop calculation on estimated loads it would not be unreasonable to see 30 or 40 volts dropped on the primary. That drop will be divided across the strand and also the earth between the transformer grounds (and house grounds).
This 50KVA "pig" is typical of what we have on the poles around here
http://gfretwell.com/electrical/transformer.jpg
You can see one of the hubs goes to the primary and the other to the neutral. There is only a single phase primary.
This is where they pick it off the main 3p trunk
http://gfretwell.com/electrical/Feed%20on%20Pinetree%20Lane.jpg
This is the current on the distribution pole where the 3 phases balance the neutral load
http://gfretwell.com/electrical/distribution%20pole%20on%20braodway.jpg
This is the worst one .. my mistake 2.95a not 2.85
http://gfretwell.com/electrical/First%20xfmr.jpg
There are about 20 transformers on this leg. I have them all mapped but I can't find the file right now.
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snipped-for-privacy@aol.com wrote:

Can't actually see much of the primary return wire to the secondary neutral. But nice pic. Looking at "my" utility transformer there is no separate return wire for the primary. I assume it is connected to the case which is bonded to the secondary neutral. Previously I have seen the secondary neutral is continuous between transformers. Transformer case and secondary neutral are earthed at the pole, so the earth is a parallel path, as you said.
I assume the secondary neutral is what you called the "strand" and it connects back to the primary neutral.
--
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Here is a shot of the cable box with the Ground, Time Warner uses this box for every house on my street. I have to cable lines coming in, both are attached to the grounding rod in the attached photo.
http://98.30.111.32/pub/ground.jpg
wrote:

Again, this is about as clear as mud. I've yet to see a cable box with a "ground wire". You probably mean you're measuring between the cable box coax connector and the metal of the the connector on the end of the coax cable, but who knows. Given weird things are going on, you sure wouldn't be the first person who had some crazy wiring scheme going on.

Again, totally unclear what exactly this means and how you are measuring it.
Call the electric company before something bad happens to someone.

While you may have other problems causing the situation, the one thing that does seem certain is that there is a ground problem here. The AC system ground and the cable ground should be tied together near the service entrance. And if they are, then you couldn't be getting 120V between the cable coax ground and the AC ground.
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wrote:

The main "splitter" on my cable is grounded. That grounds the "braid" of all cable in the house.
The splitter and the ground were installed by the cable company.
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