Does a transformer 2ndry OCPD protects the transformer against short circuit & faults

[unsaint33]

Does a transformer 2ndry OCPD protects the transformer against short circuit & faults

450.3 is about OCPD protecting the transformers against overcurrent. 450.3 seems to be saying that as long as I follow the tables, I protect the transformer against overcurrent. My newbie question is this… I know OCPDs protect conductors and devices DOWNSTREAM against overload, shorts, and faults. I also know OCPDs provide overload protection for devices and conductors UPSTREAM - a transformer 2ndary OCPD protects that transformer against overload. But, how can the 2ndary OCPD protects the transformer against short circuit or faults?

 

[retirede]

An OCPD protects the entire circuit from faults that occur downstream of said OCPD.

 

[unsaint33]

Then, how can an OCPD sized and installed properly following 450.3 (rules for Secondary Protection of a transformer) provide overcurrent protection for the transformer which is before the OCPD, not downstream?

 

[Craigv]

Then, how can an OCPD sized and installed properly following 450.3 (rules for Secondary Protection of a transformer) provide overcurrent protection for the transformer which is before the OCPD, not downstream?

Theoretically, by opening the circuit at the overcurrent trip point (which depends on current, time, and temperature and may be far above the OCPD rating), upstream is protected. But any wiring between the transformer and the OCPD could introduce an overload or fault condition.