plc communication over high voltage cables using inductive coupling

[markito]

I am testing plc equipment over 25kV power lines using inductive clamp couplers. I find that data transfer speeds are higher in the direction of the load. I intuitively understand why but I don't have a technical explanation. Also I would like to know if it is possible to transmit data using inductive coupling when a voltage is present but the cicuit is open at one end and therefore has no load or current flow. I suspect it's not possible but can't get my brain around explaining why.

 

[Skogsgurra]

Are you using the 9-95 kHz frequency band?

Gunnar Englund

http://www.gke.org

 

[logbook]

A power system is not matched in the sense of the source impedance equalling the load impedance. This would be grossly inefficient. The source impedance is low and the load impedance is relatively high. If you try to impress a voltage across the source this will be difficult because the low source impedance will tend to short out the signal. If you try to impress a voltage across the load this will be easier because you are not short circuiting it!

If you wanted this system to work effectively you would deliberately increase the HF impedance of the lines by adding a choke (perhaps just a ferrite core). Then your signal wouldn't get shorted. Better yet might be to inject the signal onto both lines and use common-mode chokes at both ends of the line. Then the core won't get saturated by the power.

 

[keepsimple]

Is this topic still of interest to you? May I ask where I can get this type of coupler?