A New Method of Grading Suspension Insulators

Attention is drawn to the known disadvantages of the uneven distribution of voltage in long strings of disks. The general theory showing how the distribution is determined by the various capacities of the units is given. It is shown how the distribution can be improved by grading, or varying the internal capacity of the units. The proposed method of grading consists in placing flat metal rings on the insulator, around the cap and stud respectively, the porcelain disk being enlarged for this purpose. A simple method of measuring the voltage distribution is described using a single needle gap. The results of tests with and without grading are given, the graded strings showing a decidedly better distribution of voltage.