What is "stray voltage"?

I was watching a video where a man is telling a story of how he became a butcher (cattle) and mentions he had stray voltage in his barn where he milked his cows (he was not a butcher yet). Apparently the electrocuted cows then refused to enter the milking barn (can’t blame them).

So I tried looking it up and…I don’t get it. Is this just electricity lying on the ground? I have no doubt it is a thing but I am missing how this happens. Given how pervasive electricity is in modern society I find it weird I never heard of this before.

The question is the thread title…what is stray voltage? To add: How does it happen? Is it dangerous or just annoying? How do you stop it?

It typically comes from bad wiring or poor connections.

I remember this happening at a Boy Scout summer camp in northern Wisconsin. The showers were push-button, i.e. you push the button and the showerhead delivers water for maybe fifteen seconds. Lather, rinse, repeat. One summer I remember getting a shock every time I pushed the bottom. I guess that was my wet hands/feet making a decent path from the supply pipe/valve down to the wet floor and shower drain?

Wouldn’t that short out whatever it is coming from? Shouldn’t a circuit breaker trip?

Not if it’s a high resistance path. The circuit breaker can’t tell the difference between you intentionally drawing a small current and accidentally drawing a small current.

Theoretically you should never receive a shock from a piece of equipment. That’s because, in most cases, the metal enclosure/chassis is connected to earth ground. This is done by running a ground wire between the enclosure and the neutral/ground busbar inside the circuit breaker box. The neutral/ground busbar, in turn, is connected to earth ground by running a wire between the busbar and a 6 foot copper rod driven into the soil near the breaker box. Since the enclosure is connected to earth ground, and you are sometimes connected to earth ground, there should be no voltage between you and the enclosure, regardless if there’s an internal fault or not. And hence you should never receive a shock when touching the chassis. Assuming there’s no break in the ground wires.

Above I say “in most cases” because there are exceptions:

  1. Some equipment is “double insulated,” which basically means the equipment is designed such that it would require two faults in order for the chassis to become “hot.”

  2. For some equipment, connecting the enclosure to earth ground is riskier than keeping it ungrounded. A toaster is one example. It was found that some of people will stick a metal knife inside the toaster to remove bread that won’t pop out, and they’ll do it while it’s plugged in and voltage is applied to the heating elements, unfortunately. If the enclosure were grounded the risk of shock is high because it’s virtually guaranteed the hand not holding the knife would be touching the (grounded) enclosure. With an ungrounded enclosure, there’s a decent chance the person is not grounded when sticking the knife in, and therefore would not receive a shock.

Ground Fault Circuit Interrupters can. They compare the current running through each leg of the wiring. If it isn’t equal, it means that some is running through CP, standing in salt water near the aquarium, and the current is switched off. I’m sure the cows would have appreciated that.

One problem with farms in particular is that they often have their own grounding electrodes, which also provides a return path for the neutral.

If the ground dries out then the earth electrode connection can degrade, what this means in practice is that you can get concentric zones of electrical potential around the earth electrode - its usually not much at all, perhaps a few volts per yard, it also means any earthed metal structure will also rise in its potential with respect to true earth.

For us humans, having a variation in voltage across the floor isn’t a big deal usually- think of it like a weather map but instead of barometric pressure its actually voltage - you might get a voltage gradient of a few volts per yard, well humans don’t tend to reach far across the floor and usually we have footwear on - so we are almost always unaffected - except if you get a bit near a lightening ground strike.

For livestock it is very different, especially for cattle - the length of their bodies is such that the forelegs are going to be easily 6 feet and probably more - worse still the current path from front to back goes right through their heart, and finally their feet generally dig in far more than ours thus making very good contact with the floor. It all means that cattle especially are very vulnerable to stray ground voltages - it is always good practice to ensure that livestock cannot get anywhere near a ground earth electrode. Its also the reason why lightening ground strikes are so much more likely to kill livestock - even though the beasts can be quite some distance away.

The “electrocuted” cows could not refuse, they’d be dead.

Stray voltage in a barn causes momentary discomfort via electric shock.




past tense: electrocuted ; past participle: electrocuted

  1. injure or kill someone by electric shock.
    “a man was electrocuted when he switched on the Christmas tree lights”

So…injury is enough and the cows were injured. So, they were electrocuted.

Wikipedia says

Electrocution is death or severe injury by electric shock, electric current passing through the body. The word is derived from “electro” and “execution”


Electricians and scientists tend to use it to mean death. The type of “injury” that occurs in barns is mild, I’ve experienced it with watering troughs.

Sorry for the hijack, I’ll drop it.

A municipal pool I hung out at as a kid had a little area with some video games. If you touched anything metal (coin mech, screws on the control panel) on one particular game, you’d get a mild shock. Not really painful but an uncomfortable 60Hz buzzing. It was probably about 60 volts.

Later, some high school friends were in a band. During a show, one guy kept getting shocked from his guitar strings. Solution: stand on a piece of wood during the set. His shoes weren’t enough to insulate from ground but the wood was.

Stray voltage can be a big problem in aquarium setups. You get a pump or something that has a tiny bit of wear in the wiring, it’s wet enough to communicate with the standing water, the fish become distressed.

That can also happen when an electric water heater element’s insulation gets corroded enough, exposing the water to voltage. It happened at my house a few times when I was young- dad wasn’t really good at keeping up with maintenance on such things.

I’m not sure if I completely understand what you’re talking about here. But… if a device is powered from hot and neutral via a circuit breaker box, it is not O.K. to simply connect the device’s metal chassis to the earth and be done with it. There must be a low-impedance path between the chassis and the neutral/ground busbar inside the circuit breaker box. And the only way to ensure there is a low-impedance path is to connect a copper wire between the chassis of the device and the neutral/ground busbar inside the circuit breaker box. This will also ensure the circuit breaker trips if there’s a ground fault inside the equipment.

In addition it is not O.K. to connect the neutral to the chassis; there must be a separate copper wire run between the chassis of the device and the neutral/ground busbar inside the circuit breaker box.

At least the above is true for the U.S. and those with similar systems. YMMV.

It might not be OK to rely on the earth for a return path, but it’s still done a fair bit. And of course, even if (almost) all equipment chassis are supposed to be grounded, the ground connection can go bad in various ways.

The worst I ever saw was back when I was working as an electrician’s assistant. A family’s kitchen had the refrigerator door such that when the door opened, it came close to the door to the oven. And whenever the two handles came close, there was a visible arc between the two. Thankfully, the family had enough sense to realize that this was a serious problem, and that they needed a pro to fix it. I can’t remember all of the (many) problems in the wiring in that place that led up to that, but it included missing ground wires, poorly-connected hot wires, and a poorly-mounted outlet that sagged to the side and put one of its contacts in touch with the metal electrical box it was in.

How do they ground skyscrapers? (or any really big building)

Is the whole building grounded into the earth? (and not just electrical consumption in the building but likely lightning strikes which are not at all uncommon)

One of the problems I’ve seen is that, when people talking about “grounding,” they seem to focus on the connection to the dirt. They either downplay or are unaware of the fact that there must also be a low-impedance path between the enclosure/chassis of a device and the neutral/ground busbar inside the circuit breaker box.

The second point - that there must be a low-impedance path between the enclosure/chassis of a device and the neutral/ground busbar inside the circuit breaker box - is important for two reasons: 1) if there’s a dead short between a hot wire inside the device and the chassis, it will ensure the circuit breaker will trip, and 2) if there’s some “leakage current” to the chassis due to a breakdown in insulation or whatever, you won’t get shocked if you touch the chassis (assuming you’re grounded).

The importance of the first point - the connection to earth ground - is not understood by a lot of people, including many electricians.

In an electrical system, the neutral/ground busbar inside the circuit box is where all the grounds and neutrals from all the branch circuits terminate. There is also a copper wire that connects between this neutral/ground busbar and the dirt (via a 6 foot copper rod pounded into the ground). Now why is the neutral/ground busbar connected to the dirt? To understand why, you have to understand that the neutral/ground busbar is also connected to the center tap of the transformer’s secondary winding. (The other two ends of the winding are each 120 VAC relative to the center tap.) If the center tap of the transformer’s secondary winding were not connected to the dirt, the entire secondary winding could “float up” to thousands of volts relative to the dirt, which is obviously dangerous. So we connect the center tap of the transformer’s secondary winding to the dirt, thereby “nailing it down” and keeping it from floating up to a dangerous voltage. After that’s done, you’re only main concern when it comes to “grounding” is to ensure there’s a low-impedance path between the metal enclosure/chassis of each device and the neutral/ground busbar inside the circuit breaker box. This is done with “ground wires” in each branch circuit.

Reading the next paragraph you wrote I would agree. It made no sense to me (but I am not an electrician).

I don’t know anything about skyscrapers. But I’m guessing the metal in/on them must be connected to ground for lightning protection. I’m also guessing the electrical system is pretty much the same as any other building… there are main circuit breaker panels, sub panels, and all neutrals and grounds terminate into the neutral/ground busbars in the main panels.