A DC electrical generation system for an aircraft propelled by a turbine engine, such as a turbojet, includes at least one electrical energy storage capacity, at least one generator driven mechanically by a rotation shaft of the turbine engine and electrical connections between the electrical energy storage capacity, the generator and the aircraft equipment for powering the above-mentioned equipment with DC current, also including at least one alternative for supplying DC current to the equipment, which are autonomous in relation to any mechanical driving by a rotation shaft of the turbine engine, and a device that can cut-off power to the generator(s) and simultaneously activate the alternative current supply. The power cut-off device for triggering power cut-off and activating the alternative current supply is controlled by a control or operating parameter of the turbine engine. The alternative current supply is preferably formed by one or more supercapacitors.