×
Follow Us
Results 1 to 5 of 5

CL protective device cycles?

 Jump to latest post
    #1
  1. Join Date
    Dec 2016
    Posts
    1
    Reputation

    CL protective device cycles?

    A current limiting protective device will cut off the maximum peak fault current for currents within its current limiting range is less than which of the following?
    I was sure this was 3 cycles....
    This might be too high maybe 0.5?

  2. #2
  3. Join Date
    Jul 2018
    Posts
    5
    Reputation
    Quote Originally Posted by Havik21 View Post
    A current limiting protective device will cut off the maximum peak fault current for currents within its current limiting range is less than which of the following?
    I was sure this was 3 cycles....
    This might be too high maybe 0.5?
    i always thought instantaneous was no intentional delay, i would choose lowest option.

  4. #3
  5. Join Date
    Apr 2018
    Posts
    14
    Reputation
    Quote Originally Posted by Havik21 View Post
    A current limiting protective device will cut off the maximum peak fault current for currents within its current limiting range is less than which of the following?
    I was sure this was 3 cycles....
    This might be too high maybe 0.5?
    Per Chapter 1. page 3 of Protective Relaying Theory and Applications by Walter A Elmore:

    Applied to a relay, high speed indicates that the operating time usually does not exceed 50ms (Three cycles on 60-Hz base). The term instantaneous indicates that no delay is purposely introduced in the operation. In practice, high speed and instantaneous are frequently used interchangeably.
    Remembered this line and thought it may be applicable.

  6. #4
  7. Wanderer20001us's Avatar
    Wanderer20001us is offline Junior Member Pro Subscriber
    Join Date
    Apr 2018
    Location
    Michigan
    Posts
    18
    Reputation
    Quote Originally Posted by rofo42 View Post
    Per Chapter 1. page 3 of Protective Relaying Theory and Applications by Walter A Elmore:



    Remembered this line and thought it may be applicable.
    https://iaeimagazine.org/magazine/20...nt-limitation/

    Good article to explain CL fuse behavior...

  8. #5
  9. rofo42 is offline Junior Member
    Join Date
    Apr 2018
    Posts
    14
    Reputation
    Quote Originally Posted by Wanderer20001us View Post
    https://iaeimagazine.org/magazine/20...nt-limitation/

    Good article to explain CL fuse behavior...
    That is a phenomenal article. He has many other great articles as well. Thank you for posting.

    I've since came across a great piece in the Paul Gill book dealing with current limiting fuses.

    Chapter 8, page 439

    "Current limiting fuses melt and extinguish the arc in a half cycle or less. Non current limiting may melt in less than a half-cycle when subjected to very high values of short circuit current, but is unable to extinguish the arc in a half-cycle. Since the arc is a flexible conductor, the non current limiting fuse will allow short circuit current to reach its maximum peak value. The current limiting type of fuses are constructed with mechanisms to extinguish the arc, thereby preventing the short circuit current from reaching its maximum peak value."

    Click image for larger version. 

Name:	current-limiting-fuses.jpg 
Views:	18 
Size:	74.7 KB 
ID:	304

    This picture, taken from Thomas A. Domitrovich's article, does a great job in explaining the paragraph from the Paul Gill book.
    Last edited by rofo42; November 3, 2018 at 06:00 AM.

Subscribe

Login or register to leave a reply!


Share this thread



Related Topics

  1. Test your ANSI device number knowledge with our all new quiz!
    By testguy in forum News and Announcements
    Replies: 0
    Last Post: July 1, 2014, 06:00 AM


Related Content


Follow us


Explore TestGuy


NETA Certification Training


NICET Electrical Power Testing


Help and Support