Testing of Insulators

[Trade Journal]

Publication: The Journal of Electricity, Power and Gas

San Francisco, CA, United States
vol. 13, no. 2, p. 143-145, col. 1-2

Four Institute "Introductories" on Transmission.


IN these columns for January* there appeared an announcement of the appointment of a committee, known as the Committee on High Tension Transmission, by the American Institute of Electrical Engineers, for the purpose in general of collecting data respecting present practices and successful methods in electric power transmission at high voltage; "in a word," continues the announcement, "the endeavor will be to make this committee the clearing house for experience and ideas bearing on high tension transmission."

The first efforts of this committee are now in evidence in the papers which appear below, and each of which is submitted as an "Introduction to a Discussion" upon the particular topic indicated in its title, and upon which subject Institute members are requested to express their opinions either personally or by letter, before the regular meeting of the Institute to be held in New York City on March 27th, next. In contributing to a discussion, it is requested that the matter under discussion be taken up under the several heads, and in the manner made use of in the "Introduction," and that following the treatment of these heads, there be introduced any other matter which the "Contributor" may deem advisable. When a member takes part by mail in more than one of the discussions taking place at the same meeting, it is requested that he embody his several "Contributions" in separate letters.

The scope of these "Introductions," the prominence of their authors, and the fulness of their experiences, together with the thoroughness which is always characteristic of Institute discussions, give abundant evidence of the growing importance of the Transmission Committee. That it will become most potent in the influence it will exert upon transmission engineering is not to be doubted.

Although not embodied in Mr. Blackwell's paper, the accompanying illustrations of high tension insulators under test at the Oakland substation of the Standard Electric Company of California, are here presented for the first time as a fitting contribution to the discussion. The photographs from which these half tones were made were taken under break-down tests, wherein the potential used at the instant of photographing ranged between 120,000 and 130,000 volts at sixty cycles. The insulators and pins used in the test were identical with those specified in Figure 1 of Mr. Chesney's paper, which follows, and the testing set was of the standard Stanley type, which has been described in these columns heretofore. **—THE EDITOR.







ELECTRIC power transmission cannot be successful unless it is able to deliver uninterrupted power. Continuous operation, so far as the transmission line is concerned, depends largely upon the effectiveness of the insulator which is employed. Insulators must, therefore, be obtained which will not fail in service, and this can only be assured by the thorough testing of each one that goes on the electric lines.

The potential that can be employed safely for the transmission of power is now limited by the pressure the insulators will bear.

Transformers that are reliable and not excessive in cost can be built for twice the voltage that any line yet constructed will withstand.

As the distance over which power can be transmitted with a fixed cost of conductor varies with the potential, the length of transmission lines is to a great extent limited by the insulator.

The design of new and improved types of insulators is, therefore, most important, and these can only be developed by experiment with adequate testing facilities. In order to ascertain the value of such insulators, no method of testing can equal a practical trial under conditions of actual service. Placing new