×
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

Fault current at 11KV

Fault current at 11KV

Fault current at 11KV

(OP)
I am interested to know the typical line to earth fault level on the primary of an 11KV/400/230v D/S Trfmr, the type generally used on the UK public distribution network.
Where the tank earth and the secondary star-point earth connection are bonded the fault voltage appearing between the installations earthed parts connected via the faulted transformer and true earth would equate to the voltage drop across the tank earth electrode.
I know that the earth fault currents are often attenuated by LERs or similar devices located in sub-stations and I wonder what might be the typical magnitude and duration of these fault voltages.
 

Regards,

Lyledunn

RE: Fault current at 11KV

KVA? %Z?

You need to know these, voltage alone tells us nothing

RE: Fault current at 11KV

High side, transformer impedance won't have much impact.  All you need to know is the source impedance, Z1 and Z0.  Here it could vary over a wide range; across the pond I don't have a clue.

RE: Fault current at 11KV

(OP)
Sorry guys, I guess I wasnt too clear in my question. I  am more interested in the typical magnitude of bolted earth fault currents on the 11KV network due to deliberate attempts to restrict them by LERs or other devices. For example, would it be usual to restrict earth fault currents to a certain manageable value of say 2KA?
The KVA, %Z and electrode resistances are obvious considerations but I am really only looking for typical values.
Many thanks.

Regards,

Lyledunn

RE: Fault current at 11KV

No idea, since here systems at that level are all solidly grounded.

RE: Fault current at 11KV

Normal practice is to limit the earth fault current to the equivalent full load current of the 33/11kV transformer at the primary substation, so typically you are looking at 650-1000A. The thermal rating of the resistor is typically 10 secs, but you would expect the protection to operate and clear the fault much quicker than that.
Regards
Marmite

RE: Fault current at 11KV

UK industrial users with private MV networks typically have E/F levels similar to those Marmite has indicated or perhaps even a little lower, down to about 300A.
  

----------------------------------
  
If we learn from our mistakes I'm getting a great education!
 

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