Sizing OCPD for step up transformers

[stcalle]

Are there any provisions in the NEC for sizing the primary/secondary overcurrent protection devices for step up transformers? In the tables in article 450, I only see provisions for step down transformers; primary over 600V-secondary less than 600V (table 450.3a) and primary/secondary less than 600V (table 450.3b).


For my example, I am using a 208-13.2Y/7.63kV transformer and trying to size the primary and secondary protection needed.

Thanks

 

[raider1]

Remember that 450.3 only applies to the transformer windings. 240.21(C) addresses overcurrent protection of the secondary conductors.

So you can use 450.3(B) Primary protection only and size the primary overcurrent protective device at 125% and not protect the transformer secondary windings. Then you would go to 240.21(C) and use one of the transformer secondary conductor rules to protect the transformer secondary conductors.

Chris