Large and high-voltage power transformers are comparatively complicated and expensive elements of a substation. Hence, purchase of such transformers will need to be based on a comprehensive technical requirement. No matter how detailed the purchase specifications are, there are still some elements that may cause misunderstanding between a purchaser and a supplier. Moreover, there is also the question of whether the technical document 176must contain extremely detailed information. To avoid problems, an increasing number of purchasers have decided to organize a so-called design review. The information provided in the following sections should help with carrying out the design review process.