×
Follow Us
Results 1 to 4 of 4

NETA 2 Exam Questions - Circuit Breakers and Fault Currents

 Jump to latest post
    #1
  1. Join Date
    May 2017
    Posts
    6
    Reputation

    NETA 2 Exam Questions - Circuit Breakers and Fault Currents

    I came across a few questions today that I haven't seen in the past and honestly had me completely stumped. Any input would be great.

    A power factor test was performed on a medium-voltage oil circuit breaker. The watt loss sum of the two open-breaker tests for the A-phase was 20 milliwatts. The closed-breaker test watts loss was 22 milliwatts. What is the tank loss index (TLI) for this phase?

    What is the expected contact-resistance measurement for a 4000A 480V air circuit breaker in good condition?
    - This one kind of threw me, in my experience every breaker is different. I can honestly say no-one has taught me that there is a designated value.

    A three-phase bolted fault would primarily produce which type of current?
    - Not even sure what the question is asking

  2. #2
  3. SecondGen's Avatar
    SecondGen is offline
    I push buttons.
    NETA Level III Pro Subscriber
    Join Date
    Jan 2014
    Location
    United States
    Posts
    508
    Reputation
    Quote Originally Posted by adamstraub View Post
    What is the expected contact-resistance measurement for a 4000A 480V air circuit breaker in good condition?
    - This one kind of threw me, in my experience every breaker is different. I can honestly say no-one has taught me that there is a designated value.
    You can usually find recommended values in circuit breaker instruction books, and if you compare them, you will find that they are all pretty similar. Check out this thread for more info: https://testguy.net/threads/1369-Exp...ker-frame-size

  4. #3
  5. SecondGen's Avatar
    SecondGen is offline
    I push buttons.
    NETA Level III Pro Subscriber
    Join Date
    Jan 2014
    Location
    United States
    Posts
    508
    Reputation
    Quote Originally Posted by adamstraub View Post
    A power factor test was performed on a medium-voltage oil circuit breaker. The watt loss sum of the two open-breaker tests for the A-phase was 20 milliwatts. The closed-breaker test watts loss was 22 milliwatts. What is the tank loss index (TLI) for this phase?
    TLI = (closed breaker test in Watts) - (sum of open breaker losses in Watts)

    See this document for more info on circuit breaker power factor:

    Click image for larger version. 

Name:	2018-07-16 10.52.39.png 
Views:	8 
Size:	109.3 KB 
ID:	261

    https://www.omicronenergy.com/downlo...E-0A78861B762F

  6. #4
  7. SecondGen's Avatar
    SecondGen is offline
    I push buttons.
    NETA Level III Pro Subscriber
    Join Date
    Jan 2014
    Location
    United States
    Posts
    508
    Reputation
    Quote Originally Posted by adamstraub View Post
    A three-phase bolted fault would primarily produce which type of current?
    - Not even sure what the question is asking
    Read up on symmetrical components:

    https://en.m.wikipedia.org/wiki/Symmetrical_components

    https://www.gegridsolutions.com/smar...ymmetrical.pdf

    https://selinc.com/api/download/100688/

Subscribe

Share this thread

Related Topics

  1. NETA 4 Exam Questions 1/2017
    By ddd675 in forum NETA Level 4 Exam
    Replies: 31
    Last Post: December 8, 2020, 08:42 AM
  2. Questions and Topics I Remember From The NETA 2 Exam
    By rofo42 in forum NETA Level 2 Exam
    Replies: 8
    Last Post: November 22, 2019, 10:40 AM
  3. Which Circuit Breakers Should Have Test according to NETA
    By changeabilities in forum Electrical Testing Talk
    Replies: 4
    Last Post: January 1, 2019, 05:57 PM
  4. Neta 3 Exam pointers and questions
    By Zepold72 in forum NETA Level 3 Exam
    Replies: 13
    Last Post: April 29, 2016, 05:25 PM
  5. Official NETA Level 2 Exam Most Missed Questions, Spring 2000
    By SecondGen in forum NETA Level 2 Exam
    Replies: 6
    Last Post: March 16, 2016, 08:18 PM

Tags for this Thread

Follow us


Explore TestGuy


NETA Certification Training


NICET Electrical Power Testing


Help and Support




You are viewing the archives. Enjoy new features and join the conversation at wiki.testguy.net