What does this nameplate information mean on a BUCK AUTO transformer? 1

[bdn2004]

"This transformer is self protecting when used on a 275 MVA system." Is this just simply multiplying the Amps x Volts x 1.732 ?

 

[davidbeach]

Internal fuses that can interrupt currents up to 25 times rated current; beyond that external impedance (system or specifically added) must provide that current limitation. At that level, through faults will not cause damage.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[bacon4life]

Once you include the final zero in 2750 MVA, it is just Amps x Volts x 1.732 x 25.

A rating of 4292 amps seems really big for internal fuses. Although there is a type of pole mounted transformer called Completely Self Protected (CSP), the CPS transformers max out around 167 kVA.

I had assumed self protecting was simply a redundant way of indicating no external impedance was needed at low fault levels. IEEE C57.12.00 list various withstand requirements for various categories of transformers. Note that there is also a maximum duration of fault the transformer is designed to withstand.