Transient overvoltage protection system

Transient overvoltage protection system (1) intended to be positioned in parallel to an equipment item to be protected, the protection system comprising at least three lines (L, N, M) consisting of a first line (L), a second line (N) and a ground (M);

• the protection system (1) comprising:
• a first, a second and a third conductive branches which are intended to be connected respectively to the three lines (L, N, M) and of which each comprises a first end (14, 15, 16) intended to be connected to one of the three lines (L, N, M) and a second end (7, 8, 9) that can be connected to the second end (7, 8, 9) of the other two conductive branches;
• the first and the second conductive branches being equipped with a first (2) and a second (2, 4) voltage-sensitive protection elements;
• each of the first and second voltage-sensitive protection elements having two terminals (5, 10;
• 11, 12) and being arranged to allow a flow of current between the first and the second ends (7, 14) of the respective conductive branch when the voltage between said two terminals is higher than a voltage threshold and to inhibit a flow of current between the first and the second ends (7, 14) of the respective conductive branch when the voltage between said two terminals is lower than the voltage threshold;
• each voltage-sensitive protection element (2, 4) also being able to rise in temperature when the voltage between its terminals (5, 10) is higher than said voltage threshold;
• and
• a thermally sensitive disconnection device comprising at least one thermofusible element (3) which is in thermal contact with at least one of the first and second voltage-sensitive protection elements (2, 4);
• the thermofusible element (3) being electrically conductive at ambient temperature and being capable of melting above a temperature threshold;
• the thermofusible element (3) being arranged so as to keep the second ends (7, 8, 9) of the three branches in a connected position in which an electrical connection is assured between the second ends (7, 8, 9) of the first, second and third conductive branches;
• the thermally sensitive disconnection device comprising an elastic return device exerting a force tending to bring the first, second and third conductive branches to a disconnected position in which the second ends (7, 8, 9) of the first, second and third conductive branches are placed at a distance from one another so as to simultaneously disconnect the first, second and third branches from one another upon the melting of the thermofusible element (3).