×
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

CT Burden Question

CT Burden Question

CT Burden Question

(OP)
I have encountered a situation with a resistance grounded system that has a 25 ampere neutral grounding resistor. There is a 25:5 CT in series with the resistor to measure ground fault current. The CT secondary is connected to three CO-11 relays that are connected in series using 300 feet of #12 AWG wire (total length). Each relay is set on the 0.5 ampere tap, and each relay is set at a different time dial setting. On one side, my gut tells me that there is too much burden connected to this CT, but on the other side, I only need to obtain 0.5 amperes for proper relay operation. Can someonse shed some light on this problem for me?
Regards,
Dave

RE: CT Burden Question

The burden for the 0.5 A tap may be pretty high depending on the relay tap range. The burden is a function of the tap settings. In addition, the accuracy class for a 25/5 CT is probably very low if it even has a relaying accuracy. Plus you have three relays to drive. But the max current is going to be 25 A.

To really analyze this, you will need the CT excitation curve, or at least the accuracy class of the CT. The relay burden data should be readily available.

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