50/50 vs 100/0/100 Loading 4

[Mbrooke]

When designing an N-1 substation, is it better to have two transformers loaded 50% each, or a single hot spare?

 

[Mbrooke]

@Bill West: That is typical. I know Con Ed at several substations like Sherman Creek and Bruckner uses 3 winding 93MVA transformers supplying 13.8kv.

UK power network design manuals recommend it for 11kv supplies supplying high density load areas.

https://files.engineering.com/getfi...48ec-ae02-b1b41a2cc920&file=UK-EDS+Design.pdf

 

[prc]

As per my understanding, the limitation is not cost of MV breaker, but simply the technical limitation. For example, at 33 KV about 175 MVA LV load is the limit from the short circuit and current rating capacity. Split LV is a solution for this, used for a long time in station start up units in Thermal Power stations and steel mills. Disadvantage is failure of one LV winding throws out the entire transformer. In Malaysia, 31.5 MA 132/11 kV used for residential load areas and 90 MVA 132/33 kV for industrial load areas.