The utility model provides a voltage transformation system, including a plurality of transformer substations, all be provided with sample cock on the oil charge equipment of transformer substation, the sample cock's in the same transformer substation sample connection size and shape homogeneous phase are same. The utility model discloses an among the voltage transformation system, because the sample cock's in the same transformer substation sample connection specification (being size and shape) is the same, so when carrying out the sample of oil to the oil charge equipment of a transformer substation, only need prepare the sample multiplexer utensil with the same kind of specification of sample connection assorted of above -mentioned specification, that is to say, a sample multiplexer utensil only need be prepared by a transformer substation, the kind number of required sample multiplexer utensil when the event has reduced the voltage transformation system sample, be convenient for find the sample multiplexer utensil of required specification, thereby the time of preparation of sample has been reduced, the efficiency of the sample that transformer substation's oil charge equipment recovered the oil appearance is improved, the reduction of the multiplexer of taking a sample simultaneously utensil kind number has still reduced the management degree of difficulty of data and sample multiplexer utensil.