Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

High voltage lines

  1. Nov 6, 2003 #1
    What is commonly the voltage in the high voltage lines used to transport electric energy over large distances? What is their resistance and inductance? What is the magnitude of the current flowing there?

  2. jcsd
  3. Nov 6, 2003 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I believe the range 30 to 750 kilovolts is relatively common. I'm not quite sure of the current in most lines, but I'd expect a 50-100 amps or so for most transmission lines. Don't quote me on this!

    - Warren
  4. Dec 11, 2003 #3
    The Powerstation genarates 11-15kV at 50hz then it is stepped up to 400kV using transformers for the supergrid because more voltage = less current which means u dont need as big wires to carry the current long distences,then it is stepped down to 33k for industry, and then stepped down to 240V for towns and villages.

    I hope that helps mate...
    I even signed up to the forum just to help u out :)
    Last edited: Dec 11, 2003
  5. Dec 28, 2003 #4

    But that's 60Hz in North America
  6. Dec 28, 2003 #5


    User Avatar

    Staff: Mentor

    Re: 60Hz

    And 500kV. Distribution is more complicated. You can have 13.2kV or 4160V, and at the point of use, you can have 120V, 208V, 240V, 277V, 460V, and single or three phase.
  7. Jan 3, 2004 #6


    User Avatar
    Science Advisor
    Gold Member

    For transmission lines, I've seen 115kV, 230kV, and 345kV (phase to phase voltages).
    Last edited: Jan 3, 2004
  8. Jan 11, 2004 #7
    Hello, I`m new to this forum and this is my first post.
    I am an electrician in the making so to speak, and I think I can explain a bit here.

    The most common voltage of a generator (let`s say a dam, 50MW) is about 13kV. Then depending on the distance of the energy beeng transported it is stepped up by a substation from anywhere like 200kV to 700kv or so. Experimental power lines in Siberia run on a relatively very high 1 megavolt (1000Kv).
    The previous post that says that the main purpose of high voltage are thinner lines is not exactly it. Of cource companies want to save metal and money, but low currents result in lower losses. It is not unisual that many hundreds or thousands of kilowatts are lost in the power lines by the capacitive effect of the lines either hanging or as a cable buried in the ground. That is why high-voltage lines usually revolve (like a 4-twisted pair for a computer. A LAN cable in other words) to reduce the capacitive efect.
    Tu usual inner-city distribution the common voltage ratings do not exceed 22kV if I recall, very commonly cables.
    The it can be used directly by a large industry or transformed down to as low as 670 Volts (I`m talking about European systems) because that is the lowest "high voltage", a standard.
    Households today can recieve a 400V 3-pole TN or TN-C-S net that uses the PEN (Protective Earth & Neutral, yellow-green-blue) is split in a TN-C system where they use one plase an the N (zero point of either a Y or D transformer) point to get 2x1/3 of 400 wich is 230! A brilliant system, however the second earth error is extremely high...
    Then again older households use IT systems usually, rarely TT. Those are usual D-transformer 230V systems that can eithe use 2 or 3 phases wich both deliver 230V.
    Usually you can find out what net you have by asking your electrical company.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook