Tap position VS Impedance

Just a minor point, but the tap changer acts invariably on the HV side winding (and for this voltage transformation, will be off load or off circuit changing).


First question is "Why pick a 11/0.433 kV unit if you don't want one" - you can select the transformer you actually need - so for example a 419V secondary (at no load) and 6% impedance would be pretty typical for a nominal 400V supply characteristic. 433V secondary are a typical power distribution spec for DNO ENATS Transformers (where the first consumer may be some distance from the transformer)


Going back to the change in impedance - it will be generally very, very small - the transformer will be designed to assist with this. You can get the specific changes from the transformer data sheet (once you've selected it). However, as Mike indicated, the change normally falls into the uncertainty bucket of your model - if you need the third decimal place, then get it measured.


Regards


OMS

Just a minor point, but the tap changer acts invariably on the HV side winding (and for this voltage transformation, will be off load or off circuit changing).


First question is "Why pick a 11/0.433 kV unit if you don't want one" - you can select the transformer you actually need - so for example a 419V secondary (at no load) and 6% impedance would be pretty typical for a nominal 400V supply characteristic. 433V secondary are a typical power distribution spec for DNO ENATS Transformers (where the first consumer may be some distance from the transformer)


Going back to the change in impedance - it will be generally very, very small - the transformer will be designed to assist with this. You can get the specific changes from the transformer data sheet (once you've selected it). However, as Mike indicated, the change normally falls into the uncertainty bucket of your model - if you need the third decimal place, then get it measured.


Regards


OMS