Electrical insulator string with bullet-proof protective rings

A bullet-proof insulator assembly comprising, an insulator string formed from a plurality of suspension insulators coupled to each other, each suspension insulator having a metal cap;

• bullet-proof rings, one of said bullet-proof rings being mounted on each of the suspension insulators, each bullet-proof ring having a shape representing a sidewall of a truncated-cone with a minimum inside diameter greater than an outside diameter of a shed portion of the suspension insulator;
• and holders mounting each of said bullet-proof rings to the suspension insulators such that each bullet-proof ring extends away from a longitudinal axis of the insulator string at an angle of 45-70 degrees relative to the longitudinal axis as the bullet-proof ring extends upwardly and that the minimum distance between adjacent bullet-proof rings (L) is longer than the minimum distance between adjacent suspension insulators (l);
• wherein each of said bullet-proof rings comprises two annular steel plates having substantially identical thicknesses, a thick annular intermediate layer sandwiched between the two annular steel plates, the annular intermediate layer being thicker than either of the annular steel plates and comprising a material selected from the group consisting of chemical fiber cloths and synthetic resin sheets, and a thin annular surface layer disposed on an outermost surface of one of the two annular steel plates, the surface layer being thinner than the intermediate layer and comprising a material selected from the group consisting of chemical fiber cloths and synthetic resin sheets and said surface layer being positioned such that it faces a direction from which a high velocity projectile originates.