×
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

Balanced Earth Fault Relay

Balanced Earth Fault Relay

Balanced Earth Fault Relay

(OP)
I'm installing a new 3.3kV Board downs sream of an existing Board fed from a 10MVA 11/3.3kV Delta Wye Transformer, with a 1500A NER on the WYE.

I'm working on the protection settings for the new Board and the breaker feeding it, and trying to discriminate with the feeeder to the existing Board.

For overcurrent, I've no problem, but the Earth Fault Protection on the incommer to the existing board is an Old relay Balanced Earth Fault Relay, Reyrolle Type B3 and the setting is given as 33M/A 50~. The REF protection is from what I can determine protectin the windinfs of the incoming transformerg

The Earth fault protection on the feeder to the new board and the new board is based ont he residual current.

My 2 questoins are
1) Do I need to co-ordinate my earth fault current on the down stream breakers with the restricted Earth Fault Protection on the incomer breaker.

2) What does a setting of 33M/A 50~ mean?

RE: Balanced Earth Fault Relay

Q1) No, restricted E/F is a unit protection scheme which doesn't care a hoot about a fault outside the protected zone.

Q2) Good question! Possibly relay setting current in mA? Any chance of a photo? I'm struggling to find a manual for this relay.
  

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

RE: Balanced Earth Fault Relay

(OP)
I was looking at that catalogue briefly last night, but the relay is infact a much older version of that.

I'll have a good read of that manual tonight though it might have some pointers. I'll get a photograph when I'm back on site if i remember.

If it is a 33mA setting that means a diference of 33ma flowing in the secondary of the CT's either side of the winding will cause a trip, So for a 2000/5A CT that would be a differnce of 13 A between the current entering one winding and Leaving the other

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