2, according to the above standard 240MVA and the following transformer, general low voltage can be 10.5 or 11kV. 360-420MVA low voltage can be 15.75kV. in my experience, 240MVA and the following capacity transformer, low voltage for 10kV should not be very difficult.
3, although now can manufacture 220kV transformer manufacturers can count more than 15, although technically there is no problem, but they may not be able to manufacture 240 or 360MVA capacity, the key to see their lifting equipment, insulation drying equipment and test equipment to meet the requirements.
4, in general, the transportation cost of large transformers is very high, it is best to purchase nearby. Of course, it also depends on the views of the A party, you can choose among several old state-owned factories in Baoding, Shenyang, Xi'an, Shandong Dachi, Hengyang, Changzhou, Yunnan, etc., and you can also refer to look at Hefei ABB, Jinan Siemens and several other factories.