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Protection riddle no.7 - Transformer Vector Group

As per design the vector group is Yd11 but on site Yd5 has arrived.

The LV side delta is made by Generator Bus Duct connections.


1) Change Bus Duct connection. ( Much delay in commissioning activities)

2) Modifications done in protection circuits of Generator,GT,UAT. to accommodate this change groups.


Is it possible ? I need some more details as to how things were done.

Author : UKB from CANADA
Mon, November 19, 2007 - 16:25
In new numerical differential relays, vector group modifications are done easily. Therefore they hadn't some problem with protection system.
In regard to different vector group step up transformers possibility, if  there are not any interconnection path between two power generators via unit transformers and relevant auxiliary switchgears, it is not problem; because we can have two or more generators with asynchrony voltage system that are connected to common bus by different group transformers.

Author : Hamid
Thu, July 21st, 2016 - 05:23
In protection point of view it is okay, relays can take care of that. But is it okay to parallel diff vector group? What about their phase difference as a result? 
Author : Rian0201 - From: Filipino
Thu, July 21st, 2016 - 10:53
The paralleling of two transformer with two differente vector group is possible, the phase sequence in primary should be arranged correctly. For example: DY1 & DY5 and ...

Author : Hamid - From: Iran
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