Neutral CTs in HV/LV transformer

I have a question regarding the use of REF protection HV/LV in 1500kVA transformer. Is it necessary to provide REF protection when already SEF (Standbby Earthfault) protection is applied. Shell DEP 33641017 table 5, doesn't say to use the REF protection while it specify to use in HV/HV transformer.

Please guide.


asked 5/28/2016

1 Answer

It depends.  There is the cost of REF protection and the cost of fixing any damage caused by earth faults.  For large transformers REF is worth the price for the protection it gives.  For small transformers, it is not. 

At 1500 kVA, it is debatable.  I know engineers (probably including myself) who would consider the use of REF.  I also know a lot of engineers who would not use it on that size of transformer. 

I'm not familiar with the Shell standards, but if they are your client I would tend to follow what they say and not apply it.  You could always run it past the clients engineer. 

answered 5/29/2016 Steven McFadyen 242
Steven McFadyen

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