Overload factors for grounding trafo - IEEE Std 32 & IEEE C62.92

[RRaghunath]

The grounding transformers are short-time rated and to obtain equivalent continuous rating for specification / transformer design purposes, the overload factors are applied. Permissible Overload factors are listed in Table 1 / IEEE C62.92.2 and continuous rating as a % of thermal rating is listed under Cl. 2.2 of the IEEE Std 32.

I find there is discrepancy in the data presented in the two codes. For example, for a 10sec rated transformer,

IEEE C62.92 - 10.5 times the continuos rating or about 10% of the thermal current rating
IEEE Std 32 - 3% of the thermal current rating

Any insight please.

The information is relevant to me in connection with a Zigzag Earthing transformer for 33kV system.

Thanks.