• State Verified Answer
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 83 subscribers
  • Views 2532 views
  • Users 0 members are here
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Instant load rejection - rotational speed of turbine

Martha
Offline

I am investigating the waterhammer in a penstock of a turbine. Simulating an instant load rejection (total simulated time 300 s)  in the transient analysis detailed report the table Time - Gate - Flow - Speed - Head of the turbine stops at 47 s. Is there a possible to see the rest of the data?

Thanks, Martha

  • 0 Online

    Hello Martha,

    There is a note in the turbine Technote, found here, about this. While the four-quadrant curves for turbines have information for different gate openings, a result of 20% gate opening is as low as the report will go. That means it is not possible to compute or interpolate the turbine operating point when the wicket gates are less than 20% open, so what HAMMER does is linearly interpolate from the flow at 20% open down to zero flow (at the time when the operating rule says the wicket gates are 0% open). Without any four-quadrant turbine characteristic curves available for these gate openings, there is no way to compute the turbine behavior.

    More than likely, your turbine gate opening is at or below 20% after 47 seconds, which is why the data stops.

    Please let me know if you have any questions.

    Regards,

    Scott Kampa

    Bentley Technical Support

  • 0 Offline
    Hello Scott,
     
    thanks for your clear answer. But I am still wondering about the speed. I attach the diagram of the speed in the case of instant load rejection. Shouldn´t go down the speed faster? At 50 s the speed is still close to the maximum.
     
    Thanks for your answer! Martha
     
    Overspeed.xlsx
  • 0 Online in reply to Martha

    Hello Martha,

    This maybe related to the gate closure pattern. To look into this, I may need to see the model. There are two options for sharing your model files on BE Communities. If you would like the files to be visible to other members, compress the files into a zip file and upload them as an attachment using the ‘Advanced Reply editor’ before posting. If your data is confidential, you can follow the instructions in the link below to send it to us via Bentley Sharefile. Files uploaded to Sharefile can only be viewed by Bentley.

    communities.bentley.com/.../bentleysecurefilesupload.aspx

    If you upload the model to Sharefile, please post here so that we know the model is available.

    Regards,

    Scott

    Answer Verified By: Martha 

  • 0 Offline in reply to Scott Kampa

    I haven't really investigated your results, and I am not a hydro power expert, but if you have a big heavy turbine that suddenly has no load applied to it, it's going to speed up and keep spinning for quite a while.

    Even when the wicket gates are 20% open, you probably still have a decent amount of water going through them to keep the turbine spinning. And without a load on the generator to 'put the brakes on', there isn't much reason for the turbine to slow down, is there?  

    regards,

    Mal

        

    Answer Verified By: Martha 

Communities
Support and Services
Training and Learning
Social Media