This standard prescribes insulation levels and dielectric test requirements for power transformers where: (1) The transformer insulation levels and dielectric test requirements are specified to be in accordance with this standard. (2) The highest voltage winding of the transformer is wye connected and rated 345 kV or above. (3) The transformer is intended for operation on an effectively grounded system and is protected by suitable surge arresters.

This standard prescribes insulation levels and dielectric test requirements for power transformers where: (1) The transformer insulation levels and dielectric test requirements are specified to be in accordance with this standard.1 (2) The highest voltage winding of the transformer is wye connected and rated 345 kV or above. (3) The transformer is intended for operation on an effectively grounded system2 and is protected by suitable surge arresters.