The invention discloses a transformer and a regional power grid system. The transformer comprises an acquisition unit, a compensation unit, a transformation unit and a judgment unit, wherein the acquisition unit is used for acquiring power factors of a regional power grid where the transformer is located; the compensation unit is connected with the judgment unit and comprises multiple reactive compensation elements; the transformation unit comprises a high voltage side and a low voltage side, wherein the high voltage side is used for receiving input voltage and outputting the input voltage from the low voltage side after transforming the input voltage; the judgment unit is used for controlling the quantity of the reactive compensation elements, connected into the regional power grid, of the compensation unit according to the power factors; the acquisition unit, the compensation unit and the judgment unit are all connected to the low voltage side of the transformation unit. Through the transformer, the purpose that the ratio of the reactive power of the regional power grid to the apparent power is regulated, and then the power factors in the regional power grid system are automatically regulated can be achieved, and labor intensity of workers is greatly reduced.