Stray Voltage on Utility Gas pipe

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mayanees

Senior Member
Location
Westminster, MD
Occupation
Electrical Engineer and Master Electrician
A friend of ine who works at a municipal electric Utility provider described a dangerous situation to me, and asked for suggestions as to how to safely handle the problem.
The situation is that when the municipal employee goes to remove a gas meter from the line that serves a house, there is voltage on the meter such that someone recently got shocked while disconnecting it.
I assume it's stray voltage on the metal pipe.
My first thoughts are to clamp around the meter while doing the disconnect, but if there's a real voltage impressed on the pipe, that could still be dangerous.
Anyone experience this?
Suggestions are appreciated.
John M
 

kwired

Electron manager
Location
NE Nebraska
Gas meters usually have dielectric fittings on the inlet and outlet to prevent the underground gas piping from becoming a grounding electrode for the electrical and other systems.

If so you should be able to measure voltage from the inlet and outlet piping if there is potential there.

You could also drive a temporary electrode which could be a screwdriver or a shovel unless soil is unusually dry and measure to see if there is any voltage between the temp electrode and the piping.

The voltage measured in either case likely will not be a full 120 volts. If it is there is probably a hot conductor energizing the gas piping in the building ;and the piping is not grounded so it does not open overcurrent device.

A temporary bonding jumper across the inlet and outlet piping will work as long as the voltage is just coming from neutral currents.
 

AdrianWint

Senior Member
Location
Midlands, UK
Here in the UK, due to several unfortunate incidents with diverted network neutral currents flowing in gas & water meter pipework, it is standard practice to bridge across the meter before disconnecting it. This procedure should also be followed when cutting underground pipework.

Adrian
 
Stray voltage may be an incorrect assumption.

Is the "shock' being conducted from the street side of the meter connection or from the house side of the meter connection?
If it is measureable, what is the actual reading?
More detail in regards as to what is actually occuring will help to determine what kind of event is actually creating this situation.
 
Here in the UK, due to several unfortunate incidents with diverted network neutral currents flowing in gas & water meter pipework, it is standard practice to bridge across the meter before disconnecting it. This procedure should also be followed when cutting underground pipework.

Adrian
If one is to install a jumper during work, that is great for the safety of the worker, but in no way will they be aware of an actual danger, or what may be creating it, or how to resolve it. We call that a 'bandaid'.
 

kwired

Electron manager
Location
NE Nebraska
If one is to install a jumper during work, that is great for the safety of the worker, but in no way will they be aware of an actual danger, or what may be creating it, or how to resolve it. We call that a 'bandaid'.

A gas company employee removing a meter puts the jumper in to protect himself.

It is not his responsibility to find the electrical problem. If he discovers there is voltage it is simply a courtesy to tell customer they may want to have it checked out. Many probably will not. Same with water meters although they normally should already have a jumper installed, but installation/repair people need to be aware of the possibility if they are going to cut an underground pipe.
 
A gas company employee removing a meter puts the jumper in to protect himself.

It is not his responsibility to find the electrical problem. If he discovers there is voltage it is simply a courtesy to tell customer they may want to have it checked out. Many probably will not. Same with water meters although they normally should already have a jumper installed, but installation/repair people need to be aware of the possibility if they are going to cut an underground pipe.

I guess this (highlighted portion) is really determined by whether or not the issue is utility or customer related.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
I don't know about making it standard proceedure to jumper around the place you are working. If in fact you are working on a meter that has dielectric unions then you would be completing a circuit possibly when making the jump. It could create a spark. This might not be so good.
 

kwired

Electron manager
Location
NE Nebraska
I guess this (highlighted portion) is really determined by whether or not the issue is utility or customer related.

Why would the gas company be the cause of the voltage present? Outside of pressure pumping stations all other electric bonds to their piping is not from their equipment. The source is from customer equipment or at least entering through customer equipment.

They often have dielectric unions on their gas meters to prevent problems from stray currents but that will not eliminate voltage across the meter just the flow of current.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Why would the gas company be the cause of the voltage present? Outside of pressure pumping stations all other electric bonds to their piping is not from their equipment. The source is from customer equipment or at least entering through customer equipment. ...
There are a number of cases where the metal underground gas pipe lines have been energized by high voltage transmission lines running above and parallel to the pipe line. This would not normally be the case with gas distribution to a building, but could be possible if the gas distribution is directly connected to a gas tranmission line that is running under power transmission lines.
 

kwired

Electron manager
Location
NE Nebraska
There are a number of cases where the metal underground gas pipe lines have been energized by high voltage transmission lines running above and parallel to the pipe line. This would not normally be the case with gas distribution to a building, but could be possible if the gas distribution is directly connected to a gas tranmission line that is running under power transmission lines.


Can they get enough power to do anything useful - free power:cool:
 
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