The invention provides an outdoor signal source device. The outdoor signal source device is mounted on an outdoor transformer substation or a distribution line, wherein the signal source device comprises an electrical element and a mechanical structure; the electrical element comprises a controller, a vacuum contactor, a high-voltage resistor, a voltage sensor and a current sensor; the controlleris used for judging a line fault area of a system and controlling the vacuum contactor to inject a characteristic coding current signal into the line fault area through the high-voltage resistor; themechanical structure comprises a box body, and the electrical element is mounted on the box body. When a single-phase grounding fault occurs in the system, the signal source device can judge and identify a fault phase and a fault section; by controlling the action of the vacuum contactor, the characteristic coding current signal is automatically injected into the fault section of the fault phase line; and when a special zero sequence CT mounted on the line detects the characteristic coding current signal, the controller drives a fault indicator to display the fault and drives an electronic switch to act at the same time.