Construction system relating to a capacitive sensor of electrical voltage; in which said system extends axially along a longitudinal axis ( Y_S.100 / Y_S.200) including a first axial end portion (Ya_S.100 / Ya_S.200) defined proximal and a second axial end portion (Yb_S.100 / Yb_S.200) defined distal; in which said system comprises: a first electrode (110 / 210), positioned near said first axial end portion (Ya_S.100 / Ya_S.200), in which the first electrode (110 / 210) has an elongated shape, in which said first electrode (110 / 210) extends coaxially with respect to the longitudinal axis (Y_S,100 / Y_S.200), in which said first electrode (110 / 210) includes a first axial portion (110.v / 210.v) defined proximal and a second axial portion (110.d / 210.d) defined distal which is opposite with respect to the first axial portion (110.v / 210.v); a second electrode (120 / 220), in which said second electrode (120 / 220) has a tubular shape, in which said second electrode extends coaxially with respect to the longitudinal axis (Y_S,100 / Y_S.200), in which said second electrode (120 / 220) is positioned around said first electrode (110 / 210), in which said second electrode (120 / 220) includes a first axial portion (120.v / 220.v) defined proximal and a second axial portion (120.d / 220.d) defined distal which is opposite with respect to said first axial portion (120.v / 220.v); a mass of dielectric insulating material (130 / 230), in which said mass at least partially encloses said first electrode and said second electrode; characterized by the fact that said second electrode (120 / 220) comprises a plurality of first elements (121a, 121b, 121c, etc. / 221a / 221b, 221c, etc.); by the fact that said first elements (121a, 121b, 121c, etc. / 221a / 221b, 221c, etc.) have an elongated shape defining for each of them a proximal axial end (121a.v / 221a.v) and a distal axial end (121a.d / 221a.d); by the fact that said first elements (121a, 121b, etc. / 221a / 221b, etc.) are disposed circumferentially side by side to each other in order to configure a tubular body (120 / 220); and by the fact that said first elements (121a, 121b, etc. / 221a / 221b, etc.) are supported in a cantilevered manner with their distal ends (121a.d / 221a.d) joined each other and with their proximal ends (121a.v / 221b.v) free. a first electrode (110 / 210), positioned near said first axial end portion (Ya_S.100 / Ya_S.200), in which the first electrode (110 / 210) has an elongated shape, in which said first electrode (110 / 210) extends coaxially with respect to the longitudinal axis (Y_S,100 / Y_S.200), in which said first electrode (110 / 210) includes a first axial portion (110.v / 210.v) defined proximal and a second axial portion (110.d / 210.d) defined distal which is opposite with respect to the first axial portion (110.v / 210.v); a second electrode (120 / 220), in which said second electrode (120 / 220) has a tubular shape, in which said second electrode extends coaxially with respect to the longitudinal axis (Y_S,100 / Y_S.200), in which said second electrode (120 / 220) is positioned around said first electrode (110 / 210), in which said second electrode (120 / 220) includes a first axial portion (120.v / 220.v) defined proximal and a second axial portion (120.d / 220.d) defined distal which is opposite with respect to said first axial portion (120.v / 220.v); a mass of dielectric insulating material (130 / 230), in which said mass at least partially encloses said first electrode and said second electrode; characterized by the fact that said second electrode (120 / 220) comprises a plurality of first elements (121a, 121b, 121c, etc. / 221a / 221b, 221c, etc.); by the fact that said first elements (121a, 121b, 121c, etc. / 221a / 221b, 221c, etc.) have an elongated shape defining for each of them a proximal axial end (121a.v / 221a.v) and a distal axial end (121a.d / 221a.d); by the fact that said first elements (121a, 121b, etc. / 221a / 221b, etc.) are disposed circumferentially side by side to each other in order to configure a tubular body (120 / 220); and by the fact that said first elements (121a, 121b, etc. / 221a / 221b, etc.) are supported in a cantilevered manner with their distal ends (121a.d / 221a.d) joined each other and with their proximal ends (121a.v / 221b.v) free.