Why can current flow from power line to earth ground?

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SUMMARY

The discussion centers on the flow of current from high voltage power lines to Earth ground, emphasizing that current can indeed flow due to the voltage difference between the wire and the ground. Participants clarify that while Earth acts as a large resistor, its resistance is often low enough to allow significant current flow, especially at voltages around 100 kV. The conversation also addresses the concept of closed circuits, noting that current can flow without a complete circuit if there is a potential difference, as illustrated by the behavior of birds on power lines. The role of capacitance in these scenarios is highlighted, particularly in relation to AC current.

PREREQUISITES
  • Understanding of high voltage systems, specifically 100 kV power lines.
  • Knowledge of electrical resistance and its implications in circuit design.
  • Familiarity with capacitance, particularly in relation to AC current.
  • Basic principles of electrical circuits, including the concept of closed circuits.
NEXT STEPS
  • Research the effects of high voltage on different materials and the implications for electrical safety.
  • Study the principles of electrical grounding and its importance in power systems.
  • Learn about the behavior of capacitors in AC circuits, focusing on capacitive reactance.
  • Investigate the phenomenon of ground faults and their detection in electrical systems.
USEFUL FOR

Electrical engineers, power system operators, safety professionals, and anyone interested in understanding high voltage electrical systems and their interactions with the environment.

  • #31
I think you always had it; just over-thinking.

As an engineer, you will soon learn when to make the simplifications necessary -
ie when to think of the wire as "ideal" with no resistance and when to think of it as a very long, but low value resistor.
 
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  • #32
I probably won't because I'm not a "real" student, and not trying to become an engineer! :) I am an online learner, using some free resources (mainly MIT OCW) to learn physics. I graduated in computer science. It'd be nice to switch field someday though!
 
  • #33
good for you, those MIT courses are excellent.

If you are interested in circuit theory, then try and pick up this book
https://www.amazon.com/dp/0415662869/?tag=pfamazon01-20

Its aimed at HNC/HND Engineering level students (Higher Nationals are vocational programmes which are equivalent to the first and second years of an engineering degree); and is the bible for circuit theory. It really starts at the basics, and goes through more complex problems and covers everything you will ever need to know unless you become a specialist.
 
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  • #34
Ok, I've looked a at it a little and it seems indeed fairly awesome, so I got the e-book right away. :D And there is a chapter about transmission lines! Thanks again.
 

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