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Can power line communication work over both live LV (+-230V) and MV (11kV) conductors? Is there hardware available that makes this possible? Up to what voltage is power line communication possible?

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MV Coupling Units come in inductive and capacitive versions. Very well know technology. You connect the PLC Unit to the coupler via a coaxial cable.

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I'm just going to give a simple reason why it might be tricky to get commercial PLC working at 11 kV.

Power line comms interfaces use a transformer and a decoupling capacitor to connect the transformer across the AC supply. For 250 volt, the transformer is largely protected by the series capacitor from taking excessive 50 or 60 Hz current: -

enter image description here

Note the capacitor on the live side connected to the NEWPORT transformer - it says 470nF x 2 and this usually means a total capacitance of ~1uF. Note that it is rated at 250V AC. Try finding a capacitor like this suitable for 11kV and you are going to struggle.

The highest SMD or leaded part in Farnell is rated at 1kV - a long way short of the mark and this is a dc rating BUT there is another problem....

The current taken from the AC thru the Newport transformer with 1uF on a 250V 50Hz supply is 78mA. Imagine what this current would be like on an 11kV line - ~3.5 amps. This would cause a problem and probably a fire so, what if the 1uF were lowered in value to 22nF - well the data may not be transmitted correctly because it will act as a low pass filter and tend to differentiate the data.

Also, please don't expect PLC data on 250V (or lower) to pass thru the sub-station transformer onto 11kV without the data getting mangled.

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  • \$\begingroup\$ If I understand you correctly, you are referring to passing the PLC signal through the actual transformer. All that I want to know if it is possible over the 11kV powerline itself without passing through a transformer. Thank you very much for the post though, really informative. \$\endgroup\$ – Cornel Verster Sep 1 '15 at 6:51
  • \$\begingroup\$ Only my last paragraph refers to passing the data thru the transformer. \$\endgroup\$ – Andy aka Sep 1 '15 at 7:12

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