A solution of the porcelain insulator problem

MANY YEARS ago porcelain insulators on transmission lines began to crack in great numbers. In the earlier cases a few disks in many strings had cracked before the transmission engineers had discovered the condition. Indeed, there was at that time no reason to believe that insulators would deteriorate in any way. As a result of these many unobserved failures which simply reduced the factor of safety in each insulator one accidental failure finally introduced surges which punctured many other insulators just on the point of failure. These failures were tens of miles apart. Thereby the whole system was put out of use.