a website collaboration between Science Service and the Smithsonian Institution


a selection of the images exhibited at the International Center of Photography and the National Museum of American History 

From the late 1920's, Science Service news syndicate sent out thousands of photographs showing the activities of scientists. This virtual exhibit highlights some of these photographs.

Insulators being tested under high voltage at the manufacturing plant of the Westinghouse Electric & Manufacturing Company, Derry, PA


1997.3001.004  exibition identification number

no date

Insulators being tested under high voltage at the manufacturing plant of the Westinghouse Electric & Manufacturing Company, Derry, PA.

Original Caption by Science Service

End of high resolution views.

Comments on March 30, 2000

My thought on the porcelain is that they are conducting puncture testing on the pieces. This is commonly referred to as a flashover test, in other words, trying the porcelain to be sure the over stress (voltage) flows over the piece instead of puncturing it.

My guess is that those columns are lightning arrestor housings, note the sanded ends of the units, that is typical preparation for a cemented on fitting, (cap, etc).

The arrester assembly would stack inside of the porcelain column, gaps, resistors, etc. The caps would be cemented in place along with a rubber gasket to form a water-tight seal.

The most common failure mode of these units (hopefully years later) was the degradation of the seal or cement thus allowing water to enter the column, moisture at that high a voltage, with ground at one end and H.V. at the other can be, and usually is disastrous! Application voltage of completed units, probably 69K.V.

                                                    Chris Hedges, Insulator Collector - ICON Member

Comments on March 30, 2000

It is a very interesting photograph of bushing insulators being subjected to an electrical test. This was common practice at all insulator factories.

Each and every insulator was tested. It appears from your collection of photographs that this particular photograph was also from the Westinghouse factory in Derry, PA. The large bushings in the photograph were probably used on large transformers (such as those at power plants and substations). Bushings were mounted at angles in the top of the transformer to lead in one conductor cable and to lead out the other cable. The bushings appear to be upside-down on the test platform since the skirts would normally be pointing downward.

Note that there is a chain wrapped around each insulator at approximately the mid point of the insulator. The chain carries the current which travels to each end of the bushings. I'm not sure why the current travels both up to the top of the bushing and down to the test rack.

Note, too, that both ends of the bushings are "sanded". The "sand" is composed of porcelain grit fused to the insulator with glaze to improve the strength of the cement joint between the insulator and a metal part. One end of the insulator was probably cemented in the transformer and the other end had a metal cap cemented on it to support and guide the large conductor cable through the center of the bushing. I believe there is a photo of a huge transformer in your collection which shows these bushings mounted in the top of a transformer. ...the bushings are made of porcelain and glazed with a dark brown glaze.

                                                    Elton Gish, NIA Ethics Chairman, Insulator Historian

We hope to gather valid information to cross reference our material. However, we cannot change the existing Science Service caption, though we can include corrections, comments and sources for expanding the information on our image presentation.

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National Museum of American History


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