High impedance neutral?

[CaliforniaMikeH]

Hey all,
This is a personal one, and I usually post over on Elsmar cove in Med Devices. However, I am stuck between my local power company and my internet provider and would appreciate any help/suggestions.

I bought a new house. About a year in, my internet went out. (Cable) during the repair, it was found that the connection to the cable from the pole was a badly melted. However, they repaired it and suggested that I get the local power company to confirm my connections to the pole. I had them come out and they left a message saying that the connections were fine, but that I did not have a ground rod system and that I probably have a grounding/neutral issue in my house. Sure enough, when I go looking, I only have a old water ground, though there is evidence that there used to be a ground rod.

So, talk to city, put in ground rods, and do a few checks before I tie it in.

Place current clamp around internet cable and meter reads 2.5 A AC

Measure the voltage between the cable shield and the new GES 1.00 VAC

Disconnect internet cable and ground from house...

Voltage between internet shield and new ground rod system is 0.45 VAC

Voltage between house ground and new GES 2.58 VAC.

Voltage between house ground and cable shield is 3.80 VAC.

Set meter to measure AC current and put probes between internet shield to pole and house ground and the meter reports 2.5 A AC

Place probes between house ground and new GES and meter reports 200 mA AC.

My interpretation is that the internet modem on the pole has a better neutral connection than my house, that this is driving the local ground potential up several volts, and that local power company needs to fix my neutral connection to the pole, and that if it gets much worse, things could get exciting. Local power company says internet company needs to fix their modem.

Am I nuts?

 

[infinity]

I had them come out and they left a message saying that the connections were fine, but that I did not have a ground rod system and that I probably have a grounding/neutral issue in my house. Sure enough, when I go looking, I only have a old water ground, though there is evidence that there used to be a ground rod.

A ground rod or lack thereof should not be a problem. The system should operate normally without a ground rod and you already have a water pipe electrode. Did you check the main bonding jumper at the service? Have you checked all of the neutral connections?

 

[ppsh]

Shut off your main breaker and see if the current goes away, if it stays, it's likely coming back from a neighbor on the same transformer.

 

[CaliforniaMikeH]

First, thanks all. Greatly appreciated. Especially in 10 minutes.

Voltage between the neutral coming into the service and the service ground is several mv AC.

I just put my clamp around the line from the pole and it reads a net current of 2 A AC. Current to cold water pipe read 50 mA. Turned off main breaker and net current dropped to 20 mA AC.

I'm thinking neutral connection at pole.

???

 

[hbiss]

I've never seen a "modem" on the pole.

I need to know the current on each of your hots as well as on the neutral where they come into your panel. Then I want to see the current on your cable drop and the current on the GEC going to the water line. I don't care about any voltages or the ground rods.

Do you have a "ground block" that the cable drop connects to outside or inside near where the cable drop enters your house? There should be a ground wire from it connected to the panel with a clamp or maybe to the GEC going to the water line. The ground block grounds the cable shield to your service neutral. The cable company is required to provide all that.

Essentially you have three parallel ground paths throughout your neighborhood that connects all houses together:

The power company neutral from house to house.
The cable company shields from house to house.
The underground water line from house to house.

It's entirely possible that what you are seeing is the division of current among the three paths coming from outside your house. I also suspect that the melted cable on the pole might be from lightning or a power line fault at one time. I would certainly have your neutral and connections checked at the panel, at the meter and at the pole. Other than that, I would just pay attention for any flickering lights or a drastic increase in current on the cable drop.

-Hal