Glass oil insulators used on line from Oregon City to Portland

NEW INSULATORS.

They Are a Decided Improvement on

the Article in Use.

Specimens of an extraordinary kind of glass insulators for electric wires have been received by the Portland General Electric Company, and have been examined by Electrician W. C. Cheney.

They are of green glass and somewhat the shape of the insulators seen on telegraph lines throughout the country, but they are much larger and more complicated. They are intended to carry the heavy wires from Oregon City to the company's station here, when the new dynamos are put in, and the new style of long distance transmission of electricity for power and light purposes by increasing the voltage or "pressure," is in effect. Of course, when a heavier pressure is brought to bear on the wires, the leakage or waste will be increased, and the object of the new insulators is to prevent, as far as possible, any such waste.

The common insulator is practically a glass cup or tumbler screwed on an iron pin, driven in the cross arm on the poles and to which the wire is fastened. Water is a good conductor of electricity, but the rain falling these inverted tumblers runs off at the bottom, leaving the inside dry in theory, and affording no chance for any electricity to escape down the poles. In practice, however, it is found that the inside of these glasses becomes covered with moisture in rainy weather and allows leakage of the electricity. The new insulators have a projecting ledge, with the ledge turned down all around for about half an inch, and another glass vessel filled with oil is fitted up inside, into which this down-turned edge sits. The oil used is a non-conductor of electricity, and it is impossible for any of the later to get from the insulator to the pole, because it cannot get through the oil. The affair is however, cumbrous, and the inner vessel is liable to get broken. So Mr. Cheney has devised an insulator much like the ordinary one, with two projecting ridges on the inside, turned up to form cups. When these are filled with oil it will be better than the more complicated one.