Secondary Injection for Transformer Differential Protection

[odlanor]

ABB introduce a new standardized testing methodology for transformer differential protection relay , only using Secondary Injection current.
The standard three-phase power transformers introduce a fixed phase angle shift Θ of n*30º (n=0, 1, 2, …, 11)

My case is first connection type (i.e. both main CTs stared inside) and my stepup transformer is YNd1d1.
Is this connection type aplicable for 3 winding transformer?

reference:
SA2008-000355 rev. -Universal Testing Method for Power Transformer Differential Protection -
Secondary Injection for Transformer Differential Protection

 

[Bramb]

Hi Odlanor,
the answer is in the last page of the document (as I googled it):

By using this method it is possible to test the differential protection for an n-winding
transformer by testing in between two windings at a time. However, note that the SrMax
value shall ALWAYS be used for the base current calculations on all sides of the
protected power transformer. It is sufficient to test winding 1 side against all other
windings (one at the time) in order to verify proper operation of the relay for all operating
conditions.

Ciao
Erminio

The difference between overload and short circuit lies in the nature of the fault, not in the value of the current.

 

[odlanor]

Thank you ErmBra