the invention relates to the field of the detection , even of the determination , of the characteristics of an electric voltage present at the level of an electrical installation 1 powered by a generator 2 , including several terminals 3 , 4 , one 3 of which is , as the case may be , connected to the earth ( attached figure ) or floating . the present invention will find a very particular application within the framework of fixed electrical installations , in particular of high - voltage , even very high - voltage electrical installations , namely electrified lines , however without the present invention being in any way limited thereto . the invention also relates , on the one hand , to a method for determining the characteristics of the electric voltage of such an electrical installation 1 and , on the other hand , to a device 5 for determining the characteristics of the electric voltage of such an electrical installation 1 , such a device 5 being , in particular , designed capable of implementing said method . as can be seen in the attached figure , this device 5 includes an electric circuit 6 at the level of which are defined at least two points 7 , 8 separated by a dielectric layer 9 that has , on the one hand , a capacitance ct and , on the other hand , a resistor rt . in this respect , it should be noted that this dielectric layer 9 can , for example and preferably , be formed by a layer of air . this device 5 also includes means 10 for generating at least one electrical disturbance between at least two of the above - mentioned points 7 , 8 of the electrical circuit 6 and separated by such a dielectric layer 9 . to this end , these means 10 are connected , as the case may be , directly or indirectly to at least these two points 7 , 8 . in this respect , it should be noted that the means 10 for generating at least one such electrical disturbance are formed by means capable of generating a particular state of the material , namely a plasma , between at least two points 7 , 8 of the electric circuit 6 , thus at the level of said dielectric layer 9 . according to a particular embodiment of the invention , these means 10 for generating at least one electrical disturbance are formed by means capable of generating at least one electric are between at least two points 7 , 8 of the electric circuit 6 . as can be seen on the attached figure , the means 10 for generating at least one electrical disturbance between at least two points 7 , 8 of the circuit 6 are preferably connected , on the one hand and directly , to one 7 of these points 7 , 8 and , on the other hand and indirectly , to another one 8 of these points 7 , 8 . an additional feature consists in that the means 10 for generating at least one electrical disturbance between at least two of these points 7 , 8 are connected , directly or indirectly , to one or several terminals defined at the level of a first point 7 of the circuit 6 , namely formed by a first leg this circuit 6 includes , and / or to one or several terminals defined at the level of a second point 8 of this circuit 6 , namely formed by a second leg of this circuit 6 . a particular embodiment consists in connecting these means 10 , at the level of this first point 7 and / or at the level of this second point 8 , to a plurality of terminals . the presence of a plurality of these terminals allows generating at least one electric disturbance between , one the one hand , one or several terminals defined at the level of the first point 7 of the circuit 6 and , on the other hand , one or several terminals defined at the level of the second point 8 of this circuit 6 . in this respect , it should be noted that the plurality of terminals defined at the level of the first point 7 and / or the second point 8 allow generating a plurality of disturbances ( namely one disturbance per terminal ), which result into creating a plurality of induced currents in the first impedance 12 . a particular embodiment of the invention then consists in generating a positive disturbance and / or a negative disturbance ( in particular a positive electric arc and / or a negative electric arc ) between , on the one hand , one or several terminals ( preferably a plurality of terminals ) defined at the level of the first point 7 and , on the other hand , a second point 8 , namely one or several terminals of this second point 8 . such an embodiment will find a very particular interest in the case of a direct - current installation for which it is then possible to determine the polarity of the controlled point of such an installation . this embodiment will also find an interest in the case of an alternating - current installation , in particular within the framework of very high voltages or in a disturbed environment , in which conditions it is particularly difficult to determine the characteristics of an electric voltage through the devices of the state of art . according to an additional feature , the means 10 for generating at least one electrical disturbance are formed by a voltage generator 11 associated with the electric circuit 6 ( or the latter 6 includes ) and connected ( in particular , directly ) to one 7 of the points 7 , 8 between which such an electrical disturbance is generated . another feature consists in that the electric circuit 6 also includes a first impedance 12 having , on the one hand , a first terminal connected to the means 10 for generating at least one electrical disturbance between at least two points 7 , 8 of the circuit 6 . this first impedance 12 has , on the other hand , a second terminal connected to one 8 of the points 7 , 8 of the circuit 6 , on the one hand , between which 7 , 8 at least one electrical disturbance is generated and , on the other hand , other than the one 7 connected to the means 10 for generating at least one such disturbance . this being said , said means 10 are then indirectly connected to this point 8 and through said impedance 12 . the device 5 then includes means 13 for measuring , at the terminals of this first impedance 12 , on the one hand , a first electric current the creation of which is caused by the electrical disturbances generated by the means 10 and , on the other hand , the evolution of this first electric current . in this respect , it should be noted that this first electric current created depends on the impedances ( capacitance ct and resistor rt of the above - mentioned dielectric layer 9 ). another feature of the invention consists in that the device 5 includes an electrode 14 , associated with the electric circuit 6 , and aimed at being brought into contact with a point 15 of the electrical installation 1 at the level of which the characteristics of the electric voltage are determined . as can be seen on the attached figure , the electric circuit 6 of this device 5 also includes a second impedance 16 having , on the one hand , a first terminal connected to said electrode 14 and , on the other hand , a second terminal connected to one 8 of the points 7 , 8 of the circuit 6 , on the one hand , between which 7 , 8 at least one electrical disturbance is generated and , on the other hand , other than the one 7 connected to the means 10 for generating at least one such disturbance . the device 5 according to the invention then includes means 17 for measuring , at the terminals of this second impedance 16 ( the electric circuit 6 includes and which is associated with said electrode 14 ), a second electric current created in the electric circuit 6 due to bringing this electrode 14 into contact with the point 15 of the electrical installation 1 . according to another feature of the invention , the device 5 includes means ( not shown ) for determining the characteristics of the electric voltage of the installation 1 based , on the one hand , on the evolution of the first electric current measured through the means 13 and , on the other hand , on the characteristics of the second electric current measured through the means 17 . as evoked above , the first 12 and / or second 16 impedances are connected to one 8 of the points 7 , 8 of the circuit 6 , on the one hand , between which 7 , 8 at least one electrical disturbance is generated and , on the other hand , other than the one 7 connected to the means 10 for generating at least one such disturbance . such a connection can be ensured either directly or , preferably , through an electronic casing 18 , on the one hand , the device 5 includes and , on the other hand , which is associated with the electric circuit 6 or the latter 6 includes and , still on the other hand , connected to the first 12 and / or second 16 impedance . as evoked above , the present invention will find a particular application in the field of the electrical installations comprised of electric , namely high - voltage lines . such electric lines are usually of the overhead type , so that , in order to bring the electrode 14 into contact with a point 15 of such an installation 1 , the device 5 should be brought close to this point 15 . to this end and according to an additional feature of the invention , the device 5 is implanted at the end of an insulating pole aimed at being handled by an operator . the invention also relates to a method for determining the characteristics of the electric voltage of an electrical installation 1 powered by a generator 2 . generating at least one electrical disturbance between at least two points 7 , 8 of an electric circuit 6 separated by a dielectric layer 9 , this through means 10 for generating at least one disturbance between at least two of these points 7 , 8 ; measuring , at the terminals of a first impedance 12 this electric circuit 6 includes , a first electric current the creation of which is caused by the electrical disturbance or disturbances generated ; then bringing an electrode 14 associated with this electric circuit 6 ( or the latter 6 includes ) into contact with a point 15 of the electrical installation 1 ; measuring , at the terminals of a second impedance 16 this electric circuit 6 includes and associated with this electrode 14 , a second electric current created due to this bringing into contact ; measuring the evolution of the electric current at the terminals of the first impedance 12 due to this bringing into contact ; determining the characteristics of the electric voltage of the installation 1 based , on the one hand , on the evolution of the first electric current measured and , on the other hand , on the characteristics of the second electric current measured . in this respect , it should be noted that the means 10 for generating at least one disturbance between at least two of these points 7 , 8 are formed by a voltage generator 11 associated with the electric circuit 6 or the latter 6 includes . according to another feature of this method , when at least one electrical disturbance is generated by the generator 11 , through the latter 11 is generated a particular state of the material , namely a plasma , between at least two points 7 , 8 of the electric circuit 6 , in particular at the level of the dielectric layer 9 . in fact , when at least one electrical disturbance is generated by this generator 11 , through the latter 1 are generated one or several electric arcs created between at least two points 7 , 8 of the electric circuit 6 . in this respect , it should be noted that such a disturbance is generated between , on the one hand , a first point 7 of the circuit 6 connected to the generator 11 and , on the other hand , a second point 8 of the circuit 6 connected at least to the first impedance 12 , even to the second impedance 16 . according to a particular embodiment and as evoked above , when at least one electrical disturbance is generated between at least two points 7 , 8 of the circuit 6 , this or these disturbances are generated between , on the one hand , one or several terminals ( preferably a plurality of terminals ) defined at the level of a first point 7 of the circuit 6 and , on the other hand , a second point 8 , namely one or several terminals defined at the level of this second point 8 . a preferred embodiment consists in that at least one such disturbance ( in particular at least one electric arc ) is generated between , on the one hand , a plurality of terminals defined at the level of the first point 7 of the circuit 6 and , on the other hand , a second point 8 of this circuit 6 , namely one or several terminals defined at the level of this second point 8 . in this respect , it should be noted that the plurality of terminals defined at the level of the first point 7 and / or the second point 8 allow generating a plurality of disturbances ( namely one disturbance per terminal ), which result into creating a plurality of induced currents in the first impedance 12 . as evoked above , a particular embodiment of the invention then consists in generating a positive disturbance and / or a negative disturbance ( in particular a positive electric arc and / or a negative electric arc ) between , on the one hand , one or several terminals defined at the level of the first point 7 and , on the other hand , one or several terminals defined at the level of the second point 8 . in particular , the invention can consist in generating , on the one hand , a positive disturbance between a first terminal defined at the level of the first point 7 and a second point 8 and , on the other hand , a negative disturbance between a second terminal defined at the level of the first point 7 and the second point 8 . such an embodiment advantageously allows determining the polarity of the electric voltage of an installation 1 at a direct current , this based on the electric currents induced in the first 12 and second 16 impedances . as evoked above , the device 5 includes , at the level of the second point 8 of this circuit 6 , an electronic casing 18 , on the one hand , associated with this circuit 6 or the latter includes and , on the other hand , connected to at least the first impedance 12 , even the second impedance 16 this circuit 6 includes . this being said , the invention then consists in that , when at least one electrical disturbance is generated between two points 7 , 8 of the circuit 6 , such a disturbance is generated between , on the one hand , a first point 7 of this circuit 6 and , on the other hand , said above - mentioned electronic casing 18 .