Magnetic toroid - coupling to a power line

In summary, the conversation discusses the need for a toroid for inductive coupling to medium voltage power lines, with frequencies between 10 kHz and 900 kHz and currents up to 100 Amps at power frequency. The participants suggest using a magnetic material with a maximum permeability of 1130, and mention the use of a Rogowski coil for currents up to 100 amps. They also caution about safety regulations and FCC limits when dealing with high voltage power lines. Additionally, they mention the possibility of using existing wire communication standards for this purpose.
  • #1
stephen163
17
0
I need to obtain a toroid for inductive coupling to medium voltage power lines. The frequencies to be coupled are between 10 kHz and 900 kHz. Bear in mind that at power frequency (50 Hz), the current will be high (up to 100 Amps).

Anyone have any idea on a magnetic material that can achieve this feat? Are there any commercially available products already available to do this?
 
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  • #2
Sounds like the illusive TPU of Steven Mark(s). Good luck, heard about farmers doing this with large coils, but never seen anything conclusive. I doubt you will get any usable power from a HV line unless it's a huge coil. Again, good luck.
 
  • #3
Suppose you had a toroid of magnetic length L and realitive permeability u. Suppose it had N turns and an rms current of I. Then the peak magnetic field is

Bpeak = sqrt(2) u uo NI/L
For most magnetic materials, you will need to keep Bpeak below 1 Tesla.

So the maximum permeability you can use is
umax=BpeakL/[1.41 u0 NI]

Using L= 0.2 meters, N=1 turn primary, and I = 100 amps for a toroid, we get

umax = 1130 effective relative permeability.
So you will need to gap the toroid to keep the effective permeability below 1130, even with only 1 primary turn.

In the past, I have used a Rogowski coil for currents up to 100 amps from Magnelab:
http://www.magnelab.com/catalog/uct.php [Broken]
But I have no idea what their frequency response might be.
Another source might be Power Electronic Measurements in Nottingham, UK.
http://www.pemuk.com/
 
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  • #4
chayced said:
Sounds like the illusive TPU of Steven Mark(s). Good luck, heard about farmers doing this with large coils, but never seen anything conclusive. I doubt you will get any usable power from a HV line unless it's a huge coil. Again, good luck.

No, it sounds like he is coupling communication signals onto and off of the power line, not trying to steal energy.
 
  • #5
stephen163 said:
I need to obtain a toroid for inductive coupling to medium voltage power lines. The frequencies to be coupled are between 10 kHz and 900 kHz. Bear in mind that at power frequency (50 Hz), the current will be high (up to 100 Amps).

Anyone have any idea on a magnetic material that can achieve this feat? Are there any commercially available products already available to do this?

You need to be careful in at least two ways. The first is obvious -- the shock hazard and safety regulations involved in dealing with high voltages. There are several insulation and spacing rules that must be followed in order to get safety approvals for any device that deals with high voltages. Your liability is huge without getting those safety approvals.

The second problem has to do with FCC regulations (or the equivalent agency if you are not in the US). There are strict limits on what you can couple to power lines -- the limits vary with the frequency of the signals. In addition, some utility companies use communication over their high voltage lines for their own purposes, and would not appreciate you adding an interfering signal in their comm band. See the Utility Applictions section of this page:

http://en.wikipedia.org/wiki/Power_line_communication

.
 
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  • #6
berkeman said:
No, it sounds like he is coupling communication signals onto and off of the power line, not trying to steal energy.
Many years ago I bought a small unit from Sears Roebuck (X-10 unit) that I used to remotely turn on and off appliances and lights. It also worked remotely for lights in my friend's house who lived a block away. I have also seen in Switzerland subscription music being broadcast either on the power line or telephone line in the 50 kHz to 500 kHz band.
 
  • #7
sorry read inductive coupling and power lines and drew the wrong conclusion. X-10 or any of the other wire communication standards might give you a good starting point.
 

1. What is a magnetic toroid?

A magnetic toroid is a donut-shaped device made of a ferromagnetic material, such as iron or ferrite, which is used to concentrate and direct magnetic fields.

2. How does a magnetic toroid couple to a power line?

A magnetic toroid can couple to a power line through its magnetic field. When placed near a power line, the toroid's magnetic field can induce a current in the power line, allowing for energy transfer.

3. What is the purpose of coupling a magnetic toroid to a power line?

The purpose of coupling a magnetic toroid to a power line is to improve the efficiency of energy transfer. The toroid's magnetic field helps to concentrate and direct the energy, reducing loss and increasing the amount of energy that can be transferred.

4. How does the efficiency of energy transfer change when using a magnetic toroid?

The efficiency of energy transfer can significantly improve when using a magnetic toroid. In some cases, it can increase by up to 90%, compared to a direct coupling between the power line and the load.

5. Are there any safety concerns when using a magnetic toroid to couple to a power line?

Yes, there can be safety concerns when using a magnetic toroid to couple to a power line. The toroid's magnetic field can induce currents in nearby conductive materials, which can be hazardous. It is essential to follow proper safety protocols and ensure that the toroid is appropriately shielded to prevent any potential hazards.

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