We know that Table 450.3(B) indicates that primary OCPDs alone, are adequate to protect the transformer. However, you always have secondary conductors.
We also know that 240.21(C) also permits primary OCPDs alone, to protect secondary conductors under certain conditions.
The question is, are we talking about 2 different issues (xfmr secondary protection vs. secondary conductor protection)?
I believe that Table 450.3(B) values for primary only protection are actually used only if & when you are taking advantage of the 4 exceptions in 240.21(C).
Otherwise, secondary protection is always required.
[This message has been edited by Redsy (edited 10-04-2005).]