In particular, if you were going to try to steal power from HDVC transmission lines you'd need one cable attached to current going in 1 direction and the other attached to current flowing in the opposite direction. So this would create a branch current and if there are meters measuring the current flow, the utility companies could detect an unexpected drop in current and locate where it is coming from.
Electronic – Does using HVDC for distance transmission make theft of electricity easier to detect
hvdcpower-engineeringtransmission line
Related Solutions
They can't. They monitor the line and notice that a very small fraction of the produced power doesn't arrive at the transformer at the end of the line. Conclusion: over those several kilometers there's a leakage. There's no way to know where. BTW, the amount of power they lose this way is probably far less than cable and transformer losses.
I suspect it's a typo on Oli's part. When I put the parameters into the web-based calculator, my values match Oli's, except for the \$Z_0\$. You can see how 177 is a plausible typo for 117.
Your R is considerably lower because you 1) used a more accurate value for the resistivity and 2) analyzed at 100 MHz. You'll find that the characteristic impedance is not so sensitive to some of these other parameters (i.e. ones other than the dimensions and dielectric constant). The other parameters are more for calculating losses. Of course you still need to be careful because e.g. Er is generally not constant with frequency and this calculator assumes you take that into account "by hand".
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Best Answer
No, using DC rather than AC doesn't make power loss any easier to detect.
But it does make theft much harder to begin with. With an AC transmission line, most forms of theft rely on the AC magnetic and or electric fields radiated by the lines — i.e., there is no direct connection to the line at all.
With a DC line, there is no radiation of that type, other than any noise generated by the power converters at each end, and the random current variations caused by customers switching loads on and off.