Device for protecting the electrical network of a vehicle, comprising two parts: • a device for detecting polarity inversion; • an overvoltage detection device; and being provided with four terminals: • a first input terminal; • a second input terminal; • a first output terminal; • a second output terminal, characterized in that the device for detecting polarity inversion is provided with a first polarized nonlinear dipole, either allowing an electric current to flow therethrough when the voltage between the first input terminal and the second input terminal is positive, or blocking the flow of such a current when the voltage between the first input terminal and the second input terminal is negative, such that a first switch control element controls a first switch with as effect actuation of closure of the first switch and hence electrical connection of the first input terminal to the first output terminal, when the current flows through the first polarized nonlinear dipole, and in that the overvoltage detection device is provided with a second polarized nonlinear dipole allowing an electric current to flow only in the case that the value of the voltage between the first input terminal and the second input terminal is higher than a predefined threshold voltage, such that a second switch control element controls a second switch so that it switches from a closed rest position to an open working position such that the first switch control element cannot be subjected to any voltage, thus preventing the first switch from switching when the voltage between the first input terminal and the second input terminal is higher than the predefined voltage threshold. • a device for detecting polarity inversion; • an overvoltage detection device; • a first input terminal; • a second input terminal; • a first output terminal; • a second output terminal, characterized in that the device for detecting polarity inversion is provided with a first polarized nonlinear dipole, either allowing an electric current to flow therethrough when the voltage between the first input terminal and the second input terminal is positive, or blocking the flow of such a current when the voltage between the first input terminal and the second input terminal is negative, such that a first switch control element controls a first switch with as effect actuation of closure of the first switch and hence electrical connection of the first input terminal to the first output terminal, when the current flows through the first polarized nonlinear dipole, and in that the overvoltage detection device is provided with a second polarized nonlinear dipole allowing an electric current to flow only in the case that the value of the voltage between the first input terminal and the second input terminal is higher than a predefined threshold voltage, such that a second switch control element controls a second switch so that it switches from a closed rest position to an open working position such that the first switch control element cannot be subjected to any voltage, thus preventing the first switch from switching when the voltage between the first input terminal and the second input terminal is higher than the predefined voltage threshold.