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

How Governor HVG (High Value Gate) block function

  1. Jun 3, 2014 #1

    I am a student at University of Lao, Faculty of Engineering, Electrical Engineering Department
    I am researching about Speed Governor control system of a Hydro Power plant in my country
    and unfortunately, the company who owner of hydro power plant they have lost some of them
    papers of the system so, for the research I have found a problem with how HVG (High Value Gate) block functional or duty, I don't understand about two signal that is input of the block, input one come form PID controller and other just form a block that it is signed -0.1%
    but some paper is 110% (Sorry that I can not attachment the document on this even I try because I am a new user then I will post the schematic diagram of the system later) So, pleased give me some explanation what is it ? and how it
    functional as well as LVG (Low Value gate), if possible you
    I am looking forward to seeing your help

  2. jcsd
  3. Jun 3, 2014 #2

    jim hardy

    User Avatar
    Science Advisor
    Gold Member

    No answers yet ? Here's a pure guess.

    Would it make sense if they were limits on a signal ?

    Integral controllers sometimes halt the integration process when it reaches a high or low value beyond which it doesn't make any sense to progress. If it is a digital controller, integration can proceed to near infinity.
    An analog controller can only integrate to whatever is its supply voltage (or pressure if it's pneumatic) . The integration beyond common sense is called "integral windup" . Both analog and digital types should employ anti-windup .
    See if your manuals contain either phrase.

    110% would be a reasonable high limit on integration.

    -0.1% could also be a limit on an incoming process signal to handle power fail. A 1 to 5 volt signal that loses power will go to zero volts which is -25% . Somebody might have placed a low limit to protect a software program or to keep a contoller from following a dead signal.

    But i'm Just guessing.

    Lao, you said ? May I guess English is not your first language? Yours is good, though. Technical manuals are tough enough in one's own language. I respect your tenacity.

    Good luck -

    old jim
  4. Jun 3, 2014 #3
    Thank you very much for your sharing an idea then I will try to find more but I still need and looking for your help again, Please send me more if you have some else to advise
  5. Jun 4, 2014 #4

    Dear, Sir

    For the discussion about HVG (High Value Gate), even it doesn't have answer yet, I think it's better if you could give me some website or some document that concern to the system
  6. Jun 4, 2014 #5

    jim hardy

    User Avatar
    Science Advisor
    Gold Member


    "High Value Gate" appears to be a name often used to describe a control system element ; i'm finding it in a lot of patents and descriptions of voltage regulators when i search with Google..

    It selects from among several inputs the highest valued one and passes it along to the next element in the system. I should've guessed that from its name. Where i worked we'd call it an auctioneer.

    See if this is any help, page 6 of the pdf:
    http://www.ee.siue.edu/~smuren/ECE 545 Notes/Ch 9 - Supplemental Controls.pdf

    Now - every manufacturer, and in fact every textbook author, will have his own vocabulary but the concepts are pretty universal.

    An integrating controller that doesn't have anti-windup as i said above can integrate beyond any reasonable value.
    This will happen if it is unable to restore the balance at its inputs.
    So it would be reasonable to send its output to a high value selector before passing it along. That way if the controller integrates below zero , the next element in the control scheme will see a small negative value (-0.1%) instead of a large one. That'd keep a valve controller from trying to find a position like 200% closed, for example.
    That is one way to achieve "anti=windup", though not the best way.
    Same could be done to prevent against integration above full scale by using a low value selector. It would not pass a signal larger than some value, and 110% isn't unreasonable.

    Those are guesses - but they convey the concept. Again you'll find various sources call it by different names .

    You may find this ISA document helpful for studying older US made control systems:
    Your gates are i believe #13 and 14 in table 23, which starts at page 23 of the pdf.
    ISA were pioneers in standardizing control symbols and terminology. ANSI does most of that now.

    Now - can you post a make and model number for this governor? A lot of old manuals are online.
    Is it a Woodward ? http://www.rockfordreminisce.com/Woodward_Governor_Company.html
    Last edited: Jun 4, 2014
  7. Jun 4, 2014 #6

    jim hardy

    User Avatar
    Science Advisor
    Gold Member

    ps you might want to join this organization. They have lots of training and publications available. Their annual field engineers' meeting is worthwhile.

  8. Jun 4, 2014 #7

    Thank you very much for your patent to finding the information for me and it is really helpful
    - For the system the former is " HITACHI" but now it is modified by "Moog" and other that I'm not sure
    what else
    - I try to post the document but it is error while upload
    if possible you, can I have your Email for sending it or other way that suitable
  9. Jun 4, 2014 #8

    jim hardy

    User Avatar
    Science Advisor
    Gold Member

  10. Jun 4, 2014 #9
    Thank you very much for your patient to finding the information and it is very highly for me (So sorry with a mistake spelling)
  11. Jun 5, 2014 #10

    http://https://www.mediafire.com/?nle6pinjdked8wo [Broken]
    Last edited by a moderator: May 6, 2017
  12. Jun 5, 2014 #11

    Good morning sir, I just have sent a document to you it's governor scheme (page4)
  13. Jun 11, 2014 #12

    jim hardy

    User Avatar
    Science Advisor
    Gold Member

    Latsany - is this old thread of any help?


    There are some people here with hydro plant knowledge who might help with your control drawing investigation if you'd post a link to it.

    old jim
  14. Jun 15, 2014 #13
    Thank you very much, Sir
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook