The utility model provides a pair of direct current system exchanges and scurries into and insulating detection device, utilize the transformer to change the voltage of power, then concatenate variable resistance in the secondary side of transformer, first resistance, second resistance, concatenate between variable resistance and output line behind the 3rd series resistance, another termination detection position of output line, utilize this scheme can conveniently detect the direct current system of transformer substation, AC voltmeters connects in parallel in the once side and the output line of transformer simultaneously, this AC voltmeters has the display, the vehicle charging control system further comprises a second resistor, the technical staff is when the test direct current systemof transformer substation, be connected output line and direct current system's test position, first resistance or second resistance or third resistance are established ties with variable resistancecan obtain different resistances, whether thereby can conveniently detect direct current system meets the requirements, for prior art, ten fens convenience of the direct current system detect operation of transformer substation, the labor intensity of the technical staff is reduced.