When specifying 33kV/11kV and 11kV/400V transformers for new building project is it acceptable for 33kV/11kV transformer to be specified with delta-delta windings thus relying on cable screen and ground earth paths back to the remote DNO main substation? As opposed to delta-star with earthed neutral star point.
I assume this is UK practice, and the 33kV and 11kV side will be distributed 3 wires, no neutral and have earth fault detection and protection of some kind ? At the EHT side you sometimes find autotransformer but I assume this is double wound ?
you will need some sort of earthing transformer on the secondary side Delta star is the UK usual, with either solid earth or L or R...
from page 25 of https://www.nationalgrid.co.uk/downloads-view-reciteme/361558
Mike
I assume this is UK practice, and the 33kV and 11kV side will be distributed 3 wires, no neutral and have earth fault detection and protection of some kind ? At the EHT side you sometimes find autotransformer but I assume this is double wound ?
you will need some sort of earthing transformer on the secondary side Delta star is the UK usual, with either solid earth or L or R...
from page 25 of https://www.nationalgrid.co.uk/downloads-view-reciteme/361558
Mike
