This standard specifies the usage conditions, product classification, product models, basic parameters, technical requirements, test methods, inspection rules, marking, lifting, packaging, transportation and storage of combined transformers. This standard is applicable to combined transformers with voltage levels of 6 and 10KV, rated capacity of 30 to 160KVA, and an additional fixed frequency of 50HZ. For combined transformers with a rated capacity of 6 and 10KV greater than 1600KVA and a voltage level of 20KVA, this standard can be used with reference to this standard.