"Stray Current"-40 amps

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ghostbuster

Senior Member
Here is another site with lots of "stray current".We have told the utility it is 100% their problem to figure out.They will send a trouble truck crew,along with coffee and donuts to figure this out on their end.:)
 

ghostbuster

Senior Member
Larry:

This situation was discovered yesterday and the utility was notified.We do not have access to the utility equipment to determine:
1.How the neutral is grounded
2.Where is the bare wire grounded.

All we can do is let the utility do their own "thing" on their own timetable.


Others:

All the 480 volt loads in this facility(pumps,A/C etc.) are 3 phase there are no single phase loads on this 480 volt board(ie. no neutral load current).
 

hurk27

Senior Member
wonder if the extra ground is feeding a set of 277 volt street lights some where? Parking lot lights?

What are your voltage readings from line to this ground?
What are your voltage readings from this ground to Earth?
What are your voltage readings from the transformer case to Earth?
Could this ground be going to a buried water line, which might be connected to another service with a problem?
 
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kwired

Electron manager
Location
NE Nebraska
Does this service feed any separately derived systems and if so how how are they grounded?

You wouldn't think they would contribute like that but we must know how they are connected before they can be ruled out.

You either have a loop carrying 40 amps or a parallel circuit carrying 80, since there is apparently no current leaving the service grounded(ing) conductors at the facility it is likely the 40 amp loop.

If installed as drawn the 2nd grounded conductor serves no purpose but to create this type of a problem. If they are bonded together on both ends they are parallel conductors and better be same size, type, length, etc., If they are bonded at only one end electrical theory says it should be at transformer and be isolated at the load end. Code says you only need one grounded service conductor.
 

ghostbuster

Senior Member
Answers to Questions:

HWS:
5 separate underground PVC ducts (all filled with water)

3 for parallels ABC
1 for parallel neutral
1 for bare grounded conductor

DR:
It is a dedicated padmount tx. for this facility

Hurk:
no current flow on main water pipe or gas line

KW:

Ground Current was measured and then used summing network to determine current direction flow.It is all 100% flowing into and then out of this facility at this main switchboard as per dwg..

It would appear there are 3 H.V. switches in 1 padmount cubicle outside this facility(approx. 50' from this facility padmont tx)..One of these switches then feeds the stepdown dedicated padmount tx. feeding this facility.The other 2 appear to feed the rest of this subdivision (houses,street lights etc.).
 

kwired

Electron manager
Location
NE Nebraska
may want to be careful not to break the connection at your facilities service - you may possibly be opening the POCO primary neutral that is not connected correctly in the POCO equipment.
 

hardworkingstiff

Senior Member
Location
Wilmington, NC
may want to be careful not to break the connection at your facilities service - you may possibly be opening the POCO primary neutral that is not connected correctly in the POCO equipment.

If he did break that connection, would primary voltage be on that neutral conductor (after it is disconnected from the grounding at the service equipment end)?
 

kwired

Electron manager
Location
NE Nebraska
If he did break that connection, would primary voltage be on that neutral conductor (after it is disconnected from the grounding at the service equipment end)?

If the current being measured is indeed primary current, the amount of voltage that will be present depends on impedance of other potential current paths, if there is no other potential current path the full open circuit voltage will be present.
 

hurk27

Senior Member
If he did break that connection, would primary voltage be on that neutral conductor (after it is disconnected from the grounding at the service equipment end)?

I wouldn't think so since losing the primary neutral should not affect the delta connection that would be left, and with the 40 amps he is seeing on the grounding, I would not believe this to be primary current since the primary current on the ungrounded conductors would be barely over 6 amps at 19.5kv's,
so this looks more like a possible secondary load that is being used for something else that is directly run from the transformer, maybe a fire pump room with an XO bond on a transformer in it?
street lights? if measurements were in daylight, that should rule out street lights, just don't know,
or why this grounding conductor is the only path for this current, seems strange, thats why I thought of it going to a water pipe and maybe a service connected to the same water pipe, with a lost neutral next door or down the road, but who knows?
but I would still not disconnect it.
 
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kwired

Electron manager
Location
NE Nebraska
I wouldn't think so since losing the primary neutral should not affect the delta connection that would be left, and with the 40 amps he is seeing on the grounding, I would not believe this to be primary current since the primary current on the ungrounded conductors would be barely over 6 amps at 19.5kv's,
so this looks more like a possible secondary load that is being used for something else that is directly run from the transformer, maybe a fire pump room with an XO bond on a transformer in it?
street lights? if measurements were in daylight, that should rule out street lights, just don't know,
or why this grounding conductor is the only path for this current, seems strange, thats why I thought of it going to a water pipe and maybe a service connected to the same water pipe, with a lost neutral next door or down the road, but who knows?
but I would still not disconnect it.

This particular transformer may not even use primary neutral as a circuit conductor, but the neutral can still be carrying current from another transformer farther downstream on the system that does use the neutral as a circuit conductor - most utility single phase transformers are connected phase to neutral on the primary, open delta systems also use the neutral as a circuit conductor.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
5 separate underground PVC ducts (all filled with water)

3 for parallels ABC
1 for parallel neutral
1 for bare grounded conductor

So each phase set is run _isolated_ in its own PVC??

If the neutral and the ground are tied together at both ends, then this current may simply be circulating current induced by the actual load current.

-Jon
 

kwired

Electron manager
Location
NE Nebraska
...If the neutral and the ground are tied together at both ends, then this current may simply be circulating current induced by the actual load current.

-Jon

... If installed as drawn the 2nd grounded conductor serves no purpose but to create this type of a problem. If they are bonded together on both ends they are parallel conductors and better be same size, type, length, etc...

that is a result of my observation, neutral and ground tied together at both ends are not a neutral and ground they are improperly installed parallel conductors and are likely to cause problems.

Service conductors do not need separate neutral and ground conductors for this reason there is no way to tell the ground that it is the ground and is not allowed to carry neutral current when it is connected to it on both ends, it just does not understand that, it just feels a voltage difference on each end and can't resist conducting some current.
 

hurk27

Senior Member
that is a result of my observation, neutral and ground tied together at both ends are not a neutral and ground they are improperly installed parallel conductors and are likely to cause problems.

Service conductors do not need separate neutral and ground conductors for this reason there is no way to tell the ground that it is the ground and is not allowed to carry neutral current when it is connected to it on both ends, it just does not understand that, it just feels a voltage difference on each end and can't resist conducting some current.


While I wasn't thinking of the ground being paralleled with the neutral as to be causing the current in the ground, simply because there is no load on the neutral to produce any current, but what about if at the transformer the neutral is connected to the XO, and the grounding conductor is connected to the transformer frame, which would also be connected to primary XO? and on to the MGN?
 

Smart $

Esteemed Member
Location
Ohio
So each phase set is run _isolated_ in its own PVC??

If the neutral and the ground are tied together at both ends, then this current may simply be circulating current induced by the actual load current.

-Jon
Could be... especially if the conduits were run flat across the trench with the grounded ones being the outer runs.

Code doesn't define "in close proximity", but I consider it to be as if bundled.
 
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