A power transmission apparatus includes a power delivery unit generating a power, a load unit receiving the power, a cable, at least a connector, at least a power switch, and a communication interface. The power delivery unit and the load unit is coupled by the connector and the cable, and the power is delivered through the cable and the connector. A voltage threshold is determined according to a delivery current of the power or a load current of the load unit. When a voltage difference between a delivery voltage of the power and a load voltage of the load unit is larger than the voltage threshold, the power switch is turned OFF, wherein information of one of the delivery voltage, the load voltage, the delivery current, and/or the load current is provided through the communication interface.