Locke No. 329, M-3725, used in Idaho, California and Guanajuato lines and Locke No. 23 glass insulator at Portland

HIGH POTENTIAL INSULATORS.

Important progress has recently been made in the design of high-tension insulators. On account of the severe service exacted when operating at potentials of from 40,000 volts to 60,000 volts, The Locke Insulator Manufacturing Company has brought out an insulator intended to meet the requirements of a mechanical strength, combining at the same time qualities allowing of its satisfactory operation under all conditions at line voltages as high as 60,000 volts.

The No. 329 Locke insulator, which is illustrated in the accompanying cut, has a diameter of fourteen inches, and is composed of three shells of vitrified porcelain cemented together. This type of insulator has been adopted by the Guanajuato Power and Electric Company, as noted in the article heading the second column of page 120 of this issue. The Washington Power Company of Spokane, Wash., has also placed an order for 13,000 insulators of this type for delivery in March of this year for the equipment of the pole line of its Coeur d'Alene transmission. The Bay Counties Power Company and the Valley Counties Power Company, recognizing the value of this insulator, have also placed orders for several carloads.

Locke No. 329 "Victor" Type Porcelain Insulator.

As an evidence that there is still a difference of opinion as regards the relative values of porcelain and glass might be cited the order of the Vancouver Power Company, Limited, for 13,000 Locke No. 23, one-piece, glass insulators. These insulators have a diameter of nine inches and are guaranteed for a line potential of 50,000 volts.

The Portland General Electric Company has also recently ordered 15,000 five-and-one-half-inch glass insulators for use on its extensions in and about Portland. The seven-inch, triple petticoat, glass insulator is still being used extensively, a carload of these insulators now being en route for the Siskiyou Electric Power Company of Yreka, as well as large shipments of the same type for the Truckee River General Electric Company and the Standard Electric Company.