the invention relates to a method of determining the characteristics of the voltage of an electrical installation which is powered by a generator . the inventive method comprises the following steps consisting in : generating at least one electrical disturbance between at least two points of an electric circuit , which are separated by a dielectric layer ; observing a first electric current at the terminals of a first impedance ; bringing an electrode into contact with a point of the electrical installation ; observing a second electric current at the terminals of a second impedance ; observing the change in the first electric current at the terminals of the first impedance ; and determining the characteristics of the voltage of the installation from the change in the first electric current and the characteristics of the second electric current . the invention also relates to a device which is used to implement said method .