Arrangement at a conductor on high voltage potential

An arrangement comprising a conductor operable at a relatively high potential;

• a first member of electrically insulating material having a corresponding thickness and a selected length extending from a first end to a second end having a remote edge portion;
• and a ground part disposed on a support surface of the first member remote from the conductor and having a selected length including a first end connectable to ground adjacent to the first end of the first member and a second end spaced therefrom, and being separated from the conductor by a voltage receiving air gap;
• an insulating envelope having a corresponding thickness surrounding the conductor;
• the first member for screening off the ground part from the conductor, the air gap being dimensioned to withstand high electrical field strength caused by sudden strong voltage rises of the conductor such that air molecules in the air gap become ionized, and said insulating envelope having an outer surface and said first member having an opposite surface remote from the ground part, said surfaces arranged to receive electrical charges generated by said ionization for creating a voltage over their respective thicknesses and thereby decreasing the voltage drop in the air gap between the conductor and the ground part, the ground part extending along said first member so that the second end thereof is spaced from the conductor such that air is not ionized thereat, and the edge portion of the first member extending beyond the second end of the ground part for preventing electrical charges generated by the ionization and received on the surface of the first member remote from the ground part from migrating around the edge portion to reach said ground part on the support surface of said first member.