It is essential that all the generator transformers shall have a Ynd11 vector group? I am more concerned about the l.v to h.v. phase difference of -30 degree. Why it has to be so?
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"All my technical advices in this forum must be consulted with and approved by a local registered professional engineer before implementation" - Mohammed Samad (Linkedin Profile: http://www.linkedin.com/in/msamad)