Publication: The Electrical Engineer
New York, NY, United States
MAKING CHANGES ON A 10,000 VOLT LIVE CIRCUIT.
WE illustrate herewith the method employed by Mr. W. B. Jackson, of the Peninsular Light and Power Co., Michigan, in replacing insulators on high voltage circuits, with current on the line. Mr. Jackson's circuits carry 10,000 volts alternating. He says in a recent letter to the J. G. White Company on this subject:
"The method I use in changing the insulators upon the 10,000 volt circuit is extremely simple, but at the same time quite safe, if due precautions are taken to have the apparatus dry. We use a thirty-foot ladder in two parts so it can be made of the proper length to catch the cross-arm. At the upper end a small board is put on, having a hole in it of the right size to fit on the end of the cross-arm. For the ladder to stand upon we have a platform 30x30 inches square, having a lower part which has a pin with insulator at each corner, and an upper part which fits upon the insulators in the lower part. This upper part has two recesses for the feet of the ladder to fit in. When the ladder is in place some one goes up and screws a small hand-vise upon the cross-arm. The hand-vise is of iron and has a piece of copper wire soldered to it. This wire is touched to the line wire upon which the broken insulator is located, and if everything shows all right, is wrapped around same. A three-foot stick boiled in paraffine is used in first touching the wires together. When the grounding wire is properly on the man goes to work with bare hands and changes the insulators; then the grounding wire is taken off and the clamp removed.
"With a plant such as we have it is an absolute necessity to be able to change the insulators at any time. The only time we can shut down without causing our customers trouble is between 3 and 4 p. m. on Sundays, and a bad insulator cannot be left from Monday till Sunday; at least should not. We have not found it necessary to take the voltage off any portion of the system for two months and fourteen days."