Control.com - Nerds in Control

We have an installation in Tunisia where a CHP plant is connected to a site bus via a 7MVA YNd11 transformer. In the protection relay settings the vector group Yd11 has been chosen but we appear to be having differntial trips. Is there a difference in phase shift between a Yd11 and a YNd11?

Anybody got any ideas. Email me on tfoster@centrax.eu.com

Responding to T. Foster's query... please answer the following:

1) Does the transformer trip upon energization?

2) Does the transformer trip at no-load or at a specific load?

3) Is the transformer provided with a tertiary winding?

Regards, Phil Corso (cepsicon@aol.com)

Further to my 08-Oct (08:33) response:

4) Are transformer's wye-side CTs delta connected?

5) Are transformer's delta-side CTs wye-connected?

6) What is CT Amp-rating for wye-side current?

7) What is CT Amp-rating for delta-side current?

Regards, Phil Corso (cepsicon@aol.com)