160 volts on coax cable.

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Crash117

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C-2 electrical contractor/owner operator
Hello all. I’ve been called to a home where they have been disconnected from their internet coax provider because the house coax has 160 volts between the connection to utility demarc and connection into the house. This house has no solar or wind turbine also no battery back up ups system being used anywhere within the house that I can find. When main power to the house is shut off at the main panel, which is on a pole 75 feet from the house, the coax still has 160 volts between the 2 cables and still has 38 volts to ground. I’m out of options for things to check as to how the house coax could still have that kind of voltage on it even with main power off. Any ideas are welcome. Thanks in advance!
 
What is voltage measured between POCO grounded conductor (neutral) and a probe stuck in the dirt?

What is voltage between coax and the POCO grounded conductor?

Measure each with main on and with main off.

Make sure a cable box or television isn't what is putting voltage on the house side coax cables.

Is there current coming from some other service through your water pipe GEC?
 
There are 2 panels in this house feed from a pole mounted 400 amp service 75’ away from the house. The coax service is on an aerial drop that attaches directly to the house. With both 200 amp mains shut off 75 feet away from the house the voltage is still present I can’t directly access poco neutral to test between the coax as the coax is at the house and the poco neutral is 75’ away. I could test one of the 2 house panel feed neutrals to check if there’s voltage there
 
Is there current flowing on the coax? Or are you just testing for voltage with a digital multimeter?
 
I have disconnected every point in the house where the coax is connected. All power from the house is off.
 
There is voltage on the coax between ground and also between neutral with main power turned off at the pole. Voltage between coax and both is 160 with main power off
 
There are two conductors to coaxial cable - the inner conductor and the shield, which should be grounded. Which conductor in the coax cable is showing 160V, referenced to what conductor in the house? Is the issue that there is 160V between the inner conductor and the shield when it it connected to the house?
 
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Is there an old-fashioned telephone connection? If so, did you try disconnecting it?
 
Is the service overhead? Or underground? Could be a failing underground feed if underground. A circuit tracer such as Amprobe or Greenlee, Ideal or others that trace live circuits could lead you to the source of the voltage.
 
Have you disconnected the coax at the demarcation point and performed your voltage and current measurements on both sides, on the center conductor as well as the shield?
 
This is an overhead service which has about 160’ of drop from the utility pole connection. The utility side is also disconnected. I can trace it through the air drop to the pole where it is coiled and disconnected. The house side is also disconnected. I can see it from its connection point at the house to the utility supplied connection box. While both sides are disconnected, this air drop still generates 160 volts. This drop from the utility pole runs perpendicular to the trunk line on the pole. There is a high voltage line on this same pole which runs parallel to low voltage lines with about 10’ of separation between them. I’m at the point where the coax voltage being generated has to be an induced current since the voltage exists with both ends of cable disconnected while the cable is free floating it’s entire drop to the house.
 
All of the above testing was performed with the main power shut off to both house sub panels which originate at a main panel at a different pole from the one that drops the coax line.
 
Do you measure and voltage with the house coax connected to all of the internal devices, but not connected to the coiled portion?

Have you connected the coiled portion to a grounding block? Do you measure a voltage?

Does the cable utility measure any voltage on their side of the coax?
 
The coil is 2-3 coils just looped around a climbing peg on the pole. It doesn’t appear to be connected to anything. Yes the utility measures the same voltage on this cable at their connection point as I measure at the house. None of the cable appears to currently grounded
 
Crash117 said:
The coil is 2-3 coils just looped around a climbing peg on the pole. It doesn’t appear to be connected to anything. Yes the utility measures the same voltage on this cable at their connection point as I measure at the house. None of the cable appears to currently grounded
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If the utility measures the voltage on their coax which are not connected to your cable, it is their problem to solve.

Does the voltage on your coax go away when use a properly connected grounding block? If you do not have a grounding block install one.
 
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