Stray Current on Fence Caused by Reactor

What was the voltage?

What reactor, and what kind? Some of those big 'transformers' at substations are called 'reactors'. Or are you speaking here of the nuclear kind? How do you know this reactor is the cause of what you've described? Unless of the 'substation' kind, reactors are not magnetic devices and do not depend on magnetics for their operation except for incidentals; motors and the like. How did you measure this current? Metallic fencing is usually (and usually unwittingly) grounded, unless an electric fence, such as the kind used for livestock or secure military installations and high-security prisons. Are you confusing 'current' with 'voltage'?

129 amperes of current? That is such a precise, large, unusual value to find in something not designed to handle electric current that I do not believe you. You can make me believe you by explaining how you measured this current.

Yeah and that sort of current flowing in this sort of fence would've probably made it glow like a toaster. Could be used as a communal kitchen.

"Magnetic induction caused by reactor induced a current in the fence."

How induced? How did you determine it is a reactor doing this? Or do you mean to say that a nearby nuclear power station is somehow causing currents to flow in your fence? Possibly because of overhead high-tension wires perhaps? Reactors themselves induce nothing as they neither produce nor require magnetic fields for their operation.

Insofar as your fence being an electrical hazard, short it to ground. If is truly 129 amps you measured and not volts, what's the voltage? You can have thousands of amps flowing, but if the potential is only a few volts there is no shock hazard. Even if not a shock hazard, at 129 amps you still have a potential fire hazard should something short against the fence and heat up enough to start a fire. 129 amps is certainly enough and to spare in that department.

If, on the other hand, it is 129 volts you measured, short the fence to a length of metal rod or pipe driven into the ground. End of problem.

Or simply break the circuit. If, say, it's a simple barbed-wire fence (good luck 129 amps), cut the wire and insert a guy-wire 'egg' insulator at that point. No circuit --> no current flow --> no hazard. Here is a pic of what I mean:

• Aren't electric fences designed to cause shock, as a deterrent to animals? "It's the volts that jolts and the mills _(milliamps) that kills". Properly-designed installations provide small kicks of electricity and clearly, anything that is carrying that level of current continuously is a faulty installation.
• A fence that is not designed to be an electric one that is carrying that amount of current represents a major electrical fault just waiting for a victim; why the circuit protective device(s) haven't operated in such a case would be well worth knowing.
• Otherwise the description is nonsensical.

Isolate the fence immediately from all sources of supply and have the installation checked out by a qualified electrician and certified safe before re-energising.

Yes, they are and, from what I gather this one isn't supposed to be.

As somebody already mentioned, your fence has become a one loop transformer winding from the stray magnetic fields generated by this installation. From your picture I cannot tell where or how the wiring is making this field. (If you were in a cold climate I'd expect your fence would never ice over.) I doubt that your transformer itself is the root of the problem. I suspect the phase wiring to and from the transformer is your problem. If the phases and returns are not bundled into one cable then mindful dressing of the power runs must be done to assure that magnetic fields of cables cancel each other. I suspect that this is your problem.

Something bothers me here. This bus bar for current measurement is not accidentally closing a current path. It deliberately closes the path at one location and provides a convenient amount of room around it for a clamp on ammeter to measure the current through this copper bus bar. I believe it is a diagnostic point of this system. I do not see in this one image the whole fence but I do see that this image is part of a slide show. You're holding back information from us.

The image reminds me of a site specific safety training presentation. If I am right about this being part of safety training, we cannot answer your question because we did not take the training. We also should should not answer the question because understanding what this current reading means is your responsibility. If you do not understand this safety training, then you must repeat until you do understand.

Very intuitive analysis...you're most likely correct.

In construction this fence is earthed side by side in grounding mat. Because of reactor the magnetic field induces current in the fence. What ABB did or solution is they provide ONLY ONE earthing connection from fence to earth that means if magnetic field induced voltage to the fence there is no current path to flow OPEN CIRCUIT. But my worry is if somebody touches the fence then a complete path will occur again causing current to flow.... Do you have any solution?

Yes. Turn it off before someone gets hurt/killed.

So, I take it that ABB has solved the current flow problem by having only 1 ground point. You are worried that a person will ground it in a second place and get electrocuted. Get a voltmeter with probes and check the voltage to a metal rod which is driven into the ground. If the voltage is <50Vrms then it is low risk at that point.

This may come as a shock to you (pun intended), but using a clamp-on ammeter in a switchyard may lead to quite erroneous readings unless the device is properly shielded and designed for such service, and anything digital is usually very susceptible.

Assuming your fence surrounds the reactor only, it acts like a single turn transformer winding, not much voltage there. ABB put in that isolating link to break the "winding" and grounded it at one point to ensure that there were no loop currents.

Now think what "ground" means- zero potential- so how much current will flow if there is no potential difference between the fence and ground? For further information it's time for you to Google on "Step Potential" and "MInimizing Electrostatic Potential" in switchyard grounding/design.

1. There should be three phase reactors and the stray magnetic fields should more or less cancel each other resulting in very low currents induced in the fence. The reactor manufacturer / designer will give guidance on the distance to be maintained between the fences (or other metal structures where a 'loop' can be created) and the reactors.

2. If for some reason one of the phase connections has become open circuit, then the magnetic fields will not cancel and higher levels of induction are probable. Check for this possibility.

3. If the square red item is an insulator (check if this is so) then there should be no current measured. The fact that you are measuring a current means the red item is either shorted out or it is not an insulator.

4. In order to determine if the induction is a hazard or not, the voltage across the point where you measured the current needs to be measured with the point open circuited. However to do this safely needs care. Assume there is a hazzardous voltage there, and take the appropriate precautions to prevent electric shock. (treat as live work, and check with voltage detectors, follow your safety rules).

I think I got the correct answer from a txt book. And almost one person hit the correct answer while the other is always talking negative. If you do not know the answer or you can not suggest a solution then stop thinking negative comment. No need to make excuses i undersatand that electrical is very wide.That picture has been snapshot in my ipad because it was posted to facebook by my co engineer seeking for explanation this is taken in their substation. According to the book I read the distance of fence around the reactor should be advised by vendor. The reactor has a magnetic zone therefore distance of fence shall comply to allowable working exposure stated by international compliance. To avoid high circulating current the fence shall be divided shortly without electrcal connection to each other and individually earth. Thanks for the technical comment.

Thank you for sharing the answer so that we all can learn.

Are you going to have to move the fence away from the reactor?

{Unfortunately there are a few know-it-alls that cannot avoid posting degrading comments. When they miss-interpret the problem or don't understand the problem they automatically assume that the one that made the comment or posting is wrong, ignorant, stupid, or some how inferior.}

Could you please tell us which text book gave you this insight. I would also like to know what the reactor manufacturer (a vendor only resells a product) says is the recommended distance to a conductive fence. I cannot tell from your image how far away that high voltage insulated grey box is from this fence but it does seem to be at least a meter away. How far away should it be? I would be very interested to know what the magnetic field strength should be at this distance.

At work we have a requirement to measure and mark the above 10 Gauss magnetic field strength region for those people with medical implants. At work we have a very wide array of electromagnets and transformers that must comply with this testing. Unlike your location these magnets are in locations that people might occupy while these magnets are active.

I say this is a wonderful opportunity to put in an electric car charging station for the employees. Free power as I see it, so let's put it to use. 129amps, even at a low voltage should be quite useful. And outdoor lighting as well. If this fence were not absorbing this electrical energy, would it simply be dispersed and lost? Does harnassing this stray power actually put a load on the main reactor, thus making it have a negative impact on the reactors efficiency? I am intrigued but ignorant. Anyone?

Old Tooly - You bring up some interesting points. My guess is that the fence is too close to the reactor and that the magnetic flux is cutting through the fence so that the fence has become a transformer secondary. Secondary loading is reflected back into the primary.

With the fence too close to the reactor, the OP has:

1. a safety hazard,

2. energy losses, and

3. a reactor that is operating at a different impedance than intended.

Yes I suspected that secondary loading might be an issue thus the power is not free and would certainly not be an efficient way to utilize this energy. Personally I think that huge magnetic flux is the result of a poor design but I am not qualified to make such an assessment. Perhaps better multilayer shielding around the source of the field and recapture of the latent energy would be a solution. I would also be quite inexpensive to do. Look at layers of iron plate with simple foam separators. Each layer reduces the magnetic field a bit until it becomes manageable. On a much smaller scale I achieved this when 4- 26lb magnets (Altec 15" woofers) were in proximity of my 36" crt. I used layers of sheet metal with foam core sheets between. It took 4 layers and the magnetism was reduced to no longer messing up the screen. Metal thickness and air gap will need to be calculated by someone more learned than myself, but it can be done.