A fault isolation apparatus, wherein the apparatus comprises a controller and a circuit breaker, wherein the controller comprises a first control terminal, a first voltage collection terminal, and a current collection terminal, the circuit breaker is located on a bus connected to a direct current/direct current DC/DC conversion unit in a power supply system, and the circuit breaker is configured to: when the circuit breaker is turned on, the bus on which the circuit breaker is located is connected to the DC/DC conversion unit, or when the circuit breaker is turned off, the bus on which the circuit breaker is located is disconnected to the DC/DC conversion unit; the first voltage collection terminal of the controller is configured to collect a voltage on the bus on which the circuit breaker is located, and the current collection terminal of the controller is configured to collect a current on the bus on which the circuit breaker is located; and the first control terminal of the controller is configured to: when the voltage collected by the first voltage collection terminal is a negative value, or when the voltage collected by the first voltage collection terminal is lower than a voltage threshold and the current collected by the current collection terminal is higher than a current threshold, turn the circuit breaker into an off state, characterized in that the apparatus further comprises a self-lock apparatus of the circuit breaker, the self-lock apparatus comprises an input terminal and an output terminal, the input terminal of the self-lock apparatus is connected to the first control terminal of the controller, and the output terminal of the self-lock apparatus is connected to the circuit breaker; and the first control terminal of the controller is configured to: when the circuit breaker is in the off state, and it is detected that the voltage collected by the first voltage collection terminal is a negative value, deliver a first instruction to the input terminal of the self-lock apparatus, to instruct the self-lock apparatus to control the off state of the circuit breaker to be locked. the controller comprises a first control terminal, a first voltage collection terminal, and a current collection terminal, the circuit breaker is located on a bus connected to a direct current/direct current DC/DC conversion unit in a power supply system, and the circuit breaker is configured to: when the circuit breaker is turned on, the bus on which the circuit breaker is located is connected to the DC/DC conversion unit, or when the circuit breaker is turned off, the bus on which the circuit breaker is located is disconnected to the DC/DC conversion unit; the first voltage collection terminal of the controller is configured to collect a voltage on the bus on which the circuit breaker is located, and the current collection terminal of the controller is configured to collect a current on the bus on which the circuit breaker is located; and the first control terminal of the controller is configured to: when the voltage collected by the first voltage collection terminal is a negative value, or when the voltage collected by the first voltage collection terminal is lower than a voltage threshold and the current collected by the current collection terminal is higher than a current threshold, turn the circuit breaker into an off state, characterized in that the apparatus further comprises a self-lock apparatus of the circuit breaker, the self-lock apparatus comprises an input terminal and an output terminal, the input terminal of the self-lock apparatus is connected to the first control terminal of the controller, and the output terminal of the self-lock apparatus is connected to the circuit breaker; and the first control terminal of the controller is configured to: when the circuit breaker is in the off state, and it is detected that the voltage collected by the first voltage collection terminal is a negative value, deliver a first instruction to the input terminal of the self-lock apparatus, to instruct the self-lock apparatus to control the off state of the circuit breaker to be locked.