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How do energy plants safely measure power

Discussion in 'General Electronics Discussion' started by Agriias, Oct 29, 2014.

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  1. Agriias


    Oct 16, 2014

    How does a given power plants measure the power being generated? Is it simply a mathematical estimate based upon materials, windings, speed, magnet strength ect? Or do they have a gigantic multimeter? haha
  2. Arouse1973

    Arouse1973 Adam

    Dec 18, 2013
    Gigantic multi-meter, Yes sort of. I think most of them these days would be using computers and advanced software to maintain the plant at it's optimum efficiency. Here is a picture of a Nuclear power plant control room. But I prefer the second picture :)


    hevans1944 and KrisBlueNZ like this.
  3. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Modern power plants do need to measure how much power is being delivered to their transmission lines to determine how many turbine-driven alternators to bring on line at any given moment. The measurements are made remotely using a data acquisition system that monitors line voltage and line current from each alternator. The phase of each alternator with respect to grid phase is also monitored and adjusted remotely so that, as each unit is added or dropped, the grid experiences minimal disturbance.

    I guess you can think of all this as a gigantic multi-meter, but it is much more complicated than that. A power plant needs to keep track of how much energy it generates and delivers to the grid because that is its sole source of income: billable kilowatt hours. It also needs to know how much energy is consumed versus how much electrical energy is produced to determine the efficiency of the plant and when to re-order nuclear fuel rods or carloads of coal, or millions of cubic feet of natural gas. Of course natural gas is delivered in pipes without much delay, but I am sure the natural gas supplier would like to know how much they are expected to supply because there are other customers sipping from the same pipes.
    Arouse1973 and KrisBlueNZ like this.
  4. Bluejets


    Oct 5, 2014
    Measurement of voltage through voltage transformers, current through current transformers.
    As you said, rather flash multimeters.
    Merlin3189 likes this.
  5. Merlin3189


    Aug 4, 2011
    Well said Bluejets - an increment in information.

    Without wishing to offend Hevans, changing, "how do you measure power" into "... using a data acquisition system that monitors line voltage and line current " does not add much for most people, who probably understand P=VI.
    The question from Agriias seems to me to be asking how you acquire data about voltage and current when they are so enormous. The fact that he mentions a multimeter, which commonly measures voltage and current, suggests he knows about P=VI.
    What I (and I guess Agriias) don't know, is how you build an ac voltmeter for n x10^5 V or how you connect an ammeter to a line at these high potentials. Or if you prefer, how you remotely acquire data about voltage and current at these high potentials.
    One could remotely acquire V, I and phase data (and hence power data) from simple low voltage lines using a Fuke and run it through a PC to do all sorts of things, but at over 100kV I doubt it. Perhaps we should ask Photonicinduction to try it!

    I wonder if Agriias hit on the right solution by suggesting you calculate the power from the turbine settings? After all, that would be just the same sort of "mathematical estimate" that the computer makes based on data acquired from remote sensors

    Regards to all. Don
    Last edited: Oct 30, 2014
  6. Bluejets


    Oct 5, 2014
    OP didn't seem that serious about it given the "ha..ha"
    Other than that, you've read all that from such a small , you must be phychic.
    Also my answer is correct.
    Maybe short and to the point but correct never-the-less.
  7. Merlin3189


    Aug 4, 2011
    Well, not being psychic I may well be wrong. Yes OP was possibly not serious, but did ask a question. As I said, your answer did seem to answer it up to a point, Hevans answer was interesting and informative about why someone might want to measure the output, and how they would process that data when they had it. My point was that he seemed to skip the bit about HOW you measure these things. Just changing the words used to describe the process dodges the issue. Measuring something and acquiring data about something are just different names for the same process. All I psyched about the original question (or in my words "guessed") was that he would have wanted to know how it was done. Otherwise, why ask the question?

    Your answer I accept is correct, as I have no knowledge of this subject. I said "ïncrement" or up to a point, as I understood the idea of a voltage transformer (though I'm not so clear about a current transformer), but wondered what this would be like? Would they have a special transformer between the output lines, which I guess (again being psychic here) would need some serious insulation, or could they just add another secondary winding to one of the big step up (or down?) transformers that I guess (there I go again) might exist between the generator and the transmission line?

    I guess (ditto) that if I really wanted to know, the answer is to go to good old WikiP and start researching power generation and distribution. In fact until I saw this question, I'd never given it a thought. What made me interested was the answer. It seemed to me that although Hevans had given a detailed and interesting description of why people measure generated power and lots of interesting other info, he had done what we all tend to do at times and completely skipped the question. It contrasted markedly with your very brief answer which actually told me something that would help me understand how to measure the voltage.
    When you go to the doctor and say, "I have a sore throat?" only to be told, "ÿou have laryngitis" or say, "my knee is sore" and get told, "you have arthritis", etc, which is standard protocol with my doctor at least, you really are not being told anything, other than perhaps that the doctor does not know what is wrong, so is just trying to comfort you.
    Many experts use this technique: the standard response from plumbers, builders and garage mechanics when you tell them about a fault is, "<sucks teeth> , you've got a problem!"
    Edward DeBono quite seriously categorised this as first level explanation, one up on "I don't know" and a big up at that. But though it suffices for many places in everyday life, I think we need to recognise its limitations and try for more detail - as you did.

    Psychic regards. Donchick.
  8. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Folks, I think we are picking nits here. The OP @Agriias has a rudimentary understanding of electricity but neither he nor I work in the field of electrical power transmission. I cannot give specifics about which particular voltage transformers or current transformers are used, but these and other devices are involved in utility power measurements, as @Bluejets stated succinctly. What is important is this is not "simply a mathematical estimate." These are real measurements made with calibrated equipment that are used for billing and other accounting purposes. I like the first response given by @Arouse1973 implying it was all very complicated. It is complicated. And no offense is taken by me if anyone tries to explain it in simple terms. If I really wanted to know how utilities do the things they do, I would call one and arrange for a tour.
    KrisBlueNZ and Arouse1973 like this.
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