Power grid overvoltage protection circuit and method

The invention discloses a power grid overvoltage protection circuit and method, which protect electric equipment from being damaged under the condition of a power grid overvoltage. The circuit comprises a semiconductor switch, an overcurrent protection device and an overvoltage monitoring device, wherein the overvoltage monitoring device judges whether a power grid overvoltage occurs or not by monitoring the voltage of a primary side or a secondary side of an isolation transformer, and when the power grid overvoltage is detected, the semiconductor switch is controlled to be closed; the isolation transformer is used for reducing the voltage of a power grid and then feeding the voltage into electric equipment; the semiconductor switch is connected to the secondary side of the isolation transformer in parallel, and the short circuit of the secondary side of the isolation transformer is caused by the switching-on of the semiconductor switch; and the overcurrent protection device is arranged at the primary side of