Balanced Earth Fault Relay

[SparkyLarks]

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?

 

[ScottyUK]

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.


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

 

[rbulsara]

Would this link help? There is a reference to external non linear resistor, Metrosil.

http://www.reyrolle-protection.com/individual_product.php?product_id=123#

Rafiq Bulsara

http://www.srengineersct.com

 

[rbulsara]

The catalog refers to 33mA or 100 mA current size.

Rafiq Bulsara

http://www.srengineersct.com

 

[SparkyLarks]

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