Underground cross talk

[Bwhitedog2]

I have a situation never experienced before. Pulled underground control wiring to control contactors from remote switches at 277v from multiple sources. When I power one set of wires i am getting 100 to 150v to ground on the other wires even though they are not connected on either end. I have re-pulled the wires in case of damage but the problem persists. I can ground the other wires without arc or tripping the breaker which tells me this is not true current backed voltage but do get whack if touching the wire. I have many other underground PVC conduits with multiple conductors and feeds but act normal. This is the only one showing this condition and i am looking for answers.

 

[texie]

I have a situation never experienced before. Pulled underground control wiring to control contactors from remote switches at 277v from multiple sources. When I power one set of wires i am getting 100 to 150v to ground on the other wires even though they are not connected on either end. I have re-pulled the wires in case of damage but the problem persists. I can ground the other wires without arc or tripping the breaker which tells me this is not true current backed voltage but do get whack if touching the wire. I have many other underground PVC conduits with multiple conductors and feeds but act normal. This is the only one showing this condition and i am looking for answers.

Not sure what kind of distance you are talking here, but in general running AC control circuits over long distances can have issues with capacitive coupling. It can be bad enough to prevent a contactor from releasing for example. I seem to recall,Square D has a good white paper on this subject. Not in a position to locate it at the moment.

 

[mbrooke]

I have a situation never experienced before. Pulled underground control wiring to control contactors from remote switches at 277v from multiple sources. When I power one set of wires i am getting 100 to 150v to ground on the other wires even though they are not connected on either end. I have re-pulled the wires in case of damage but the problem persists. I can ground the other wires without arc or tripping the breaker which tells me this is not true current backed voltage but do get whack if touching the wire. I have many other underground PVC conduits with multiple conductors and feeds but act normal. This is the only one showing this condition and i am looking for answers.

Experienced all day every day. The cause is capacitive coupling with the energized circuits. Move on as you would, nothing is amiss.

 

[GoldDigger]

Experienced all day every day. The cause is capacitive coupling with the energized circuits. Move on as you would, nothing is amiss.

Nothing is amiss as long as the signals are either differential or feeding into a low impedance load such as a large relay. If the receiver is single ended (unbalanced) and is an electronic network with high input impedance, those voltages are indeed expected, but can certainly cause problems.

Sent from my XT1585 using Tapatalk

 

[mbrooke]

Nothing is amiss as long as the signals are either differential or feeding into a low impedance load such as a large relay. If the receiver is single ended (unbalanced) and is an electronic network with high input impedance, those voltages are indeed expected, but can certainly cause problems.

Sent from my XT1585 using Tapatalk

Good point, in some cases it can cause nuisance signaling. But as you say if feeding a lighting contactor or low impedance load it does not present an issue.

 

[ptonsparky]

IIRC, when farmers first started trying to control their electric wells 1/4 mile away, things would start up just fine, but not respond to the stop. You will know soon enough if it will cause you grief with controls.