New Duncan suspension insulator manufactured by Locke

[Trade Journal]

Publication: Western Electrician

Chicago, IL, United States
vol. 41, no. 13, p. 257-258, col. 3,1

Suspension Insulator for High-voltage


A suspension type of insulator, as shown in the accompanying illustration, has been designed and placed on the market by the Locke Insulator Manufacturing Company of Victor, N. Y. It was developed by J. V. E. Duncan, electrical engineer for Sanderson & Porter, New York, and W. T. Goddard, electrical engineer of the Locke company, and is believed to possess many advantages over the regulation pin-supported type of insulator for very high potentials, as used in modern power transmission.


New Suspension-Type Insulator for High-Voltage Transmission.


The insulator is said to have an ultimate mechanical strength ranging from 10,000 to 12,000 pounds. The insulator element is made up of two pieces of porcelain a short inner shell and an outer flaring shell. These shells are tested individually at a potential of approximately 60,000 volts before assembling, and the assembled element is tested at a potential in excess of 90,000 volts for a period of five minutes.

Great mechanical strength and low cost are claimed for the insulator. Being made up of a series of individual elements, it is extremely unlikely that the breakdown of one element will throw the line entirely out of service. The transmission line may be run with one unit, and the insulating element increased, at nominal erection expense, to at least 100,000 volts, as the increase in the transmission voltage may determine. In difficult localities one or more of the units can be carried about, thus taking advantage of the element of portability. The liability to puncture from damage is reduced, because of the wider separation between the earth and the conductors.

The Locke Insulator Manufacturing Company is just completing the engine and generator room of its 600-horsepower power house, brick and concrete; has just completed an addition to its testing facilities for cemented insulators, doubling the capacity, making it 1,800 terminals in all, and is building a brick fireproof transformer house in which will be installed, at the present time, five high-tension transformers, all of 200,000 volts and over.


Keywords:Porcelain : Suspension : Duncan : Locke Insulator Manufacturing Company
Researcher notes: 
Supplemental information: Patent: 880,203
Researcher:Bob Stahr
Date completed:October 5, 2009 by: Bob Stahr;