This paper mainly studied and discussed on several aspects such as power loss of transformer

the natural power allocation and optimal power allocation when two transformers operating in parallel

the ratio of the two sets’ resistance

the relationship between power allocation and transformer’s resistance and the relationship between load S and their resistance RB of two sets.It was also analyzed that transformer’s optimal operation area

critical load

and the optimal operation of two transformers in paralleled.Moreover

comparisons of total cost of apiece type two sets assembled were done

and then the lowest cost was obtained.When assembled with SFL1-10000/35×2

the total investment was 2 2080 000 yuan

the transformer operated in optimal area.