The invention discloses an overcurrent protection method, device and system for a substation. When a line is broken down, control on the magnitude of short-circuit current is achieved through in-station power electronic equipment. The method comprises the steps of obtaining a current value of a current line; judging whether the current value of the current line reaches a first protection thresholdor not, wherein the first protection threshold is located between a rated current value of the power electronic equipment and a safe current threshold of the power electronic equipment; if the current value of the current line reaches a preset first protection threshold, reducing an output voltage value of the current line and making the current value of the current line not exceed the first protection threshold; and when the protection is matched with conventional protection, controlling the output voltage value of the current line and making the current value of the current line greater than a second protection threshold but not exceed the first protection threshold, thereby driving the protection device to execute a protection action within protection reaction time, wherein the secondprotection threshold is the current value of a reliable action of the protection device and the second protection threshold is smaller than the first protection threshold.