Electrose suspension insulator

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Graded Suspension Insulators

To the Editor of the SCIENTIFIC AMERICAN :

In an article entitled "Some Problems of High Voltage Transmission," which appeared In the proceedings of the American Institute of Electrical Engineers for March, 1912, Dr. Charles P. Steinmetz states:

"With a number of equal insulating disks sharing the voltage between line and ground, the potential difference across the insulators nearest the line is higher, and the potential difference across the insulators nearest the ground is lower, than the average potential difference per insulator, the more so the greater the number of insulator disks." Also, "From this it appears that the use of a large number of small insulator disks is uneconomical at very high voltages, and a few large disks of high disruptive strength are preferable." Also, "To extend the insulating possibilities of the suspension insulator type far beyond the voltages now contemplated, therefore, requires a grading of the insulator disks in their capacity, so that the disk nearest the line has the highest, that nearest the ground the lowest capacity, or the addition of capacity at the surface of the insulator disks, in proportion to their distance from the ground."

Types of Graded Suspension Insulators.

Illustrated herewith are two forms of high-tension insulators which have been patented by the writer. These were filed, respectively, on September 23d, 1907, and December 4th, 1909. They disclose that as early as 1907 the writer understood and appreciated the value of graded suspension insulators for high-tension current. It is now conceded by many of the foremost electrical engineers that insulation of the graded suspension type is the best practice, as it insures reliability and continuity of service, under the most adverse conditions, providing means at the same time for keeping the line in operative condition even though direct lightning strokes should reach it.

Brooklyn, N. Y.   Louis STEINBERGER.