Abstract: An electrical power supply system firstly includes a power cable electrically connected to a power source. The power cable has a power line and a first conductor; the first conductor is isolated from the power line and acts as a sensing line. The power cable also has a second conductor and the second conductor is isolated from the sensing line and acts as a neutral line; the power line, the sensing line and the neutral line are electrically connected to the power source. The system further includes an arc fault circuit interrupter including a sensing circuit in electrical connection with the sensing line for detecting an arc fault and a voltage source being in electrical connection with the sensing line. The voltage of the voltage source is designed to be below the hazardous voltage according to the electrical safety rules.