×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

351-7 formula

351-7 formula

351-7 formula

(OP)
I am looking for a formula how to calculate the relay settings reverse power on SEL 377-1. I found some other formulas but I am not sure if they are applicable to this relay. I couldn't find anything in SEL manuals.
I have 25kW system, CT ratio 200:5, PT ration 36:1. I know I need some Generator info also to get the calculations but I would like to know what the formula for calculating out the settings is.

RE: 351-7 formula

perhaps check SEL 300G manual (Generator Relay)

RE: 351-7 formula

Not familiar with a 377-1.  The 351-7 does exist, and does have reverse power elements, and the manual does a pretty decent job, and their application engineers are very helpful.

RE: 351-7 formula

(OP)
Sorry, typo... I got it right in the heading, 351-7 is correct.

RE: 351-7 formula

The manual will explain the process of setting the relay.  The determination of the actual setting is up to you as the engineer.  What do you want the reverse power to accomplish?

RE: 351-7 formula

If used to prevent motoring try this formula:  
Im = secondary current to the relay
Im = (Primary kw at motoring x 1000) / (generator terminal volts x ct ratio x Sqrt(3))
You will need to set a time delay to prevent tripping during synchronizing and stable system swings.

RE: 351-7 formula

Actually that is the formula to set a directional overcurrent relay for use with reverse power.  I'm not sure if it applies to the 351-7.

RE: 351-7 formula

SEL 351S Manual, Page 3.59, talks about the power elements in the relay.  I would start there and see if that helps you setup your logic and wordbits.
 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources