Nikola Tesla on Electric Transmission
To the Editor of The New York Evening Post:
Sir: Your issue of the 14th inst. contains a report relative to an experimental demonstration at the Pittsfield plant of the General Electric Company in which a pressure of one million volts was used for transmission of power by alternating currents. This is said to be the result of more than thirty years’ work and to constitute a dramatic advance in electrical development so much, indeed, that it was deemed proper to record the time of its consummation with greater precision than that when Joshua commanded the sun to stand still over Gibeon and the moon in the Valley of Ajalon. But the prosaic fact is that I have long ago perfected and patented the invention instrumental in this achievement and applied it successfully in the production of pressures amounting to many millions of volts. It may not be amiss to state furthermore that a license was offered to the General Electric Company under my basic patent which bears the No. 1,119,732 and was granted December 1, 1914, the original application having been filed January 16, 1902.
The economic transmission of electrical energy at great distances necessitates the employment of very high pressures and at the outset two serious difficulties were encountered in their application. One was the breaking down of the insulation under the excessive stress. Upon careful investigation of the causes, I found that this was due to the presence of air or gas bubbles which were heated by the action of the currents and impaired the resisting quality of the dielectric. The trouble was done away with entirely by a process of manufacture developed by me which has been universally adopted. But the second obstacle was much harder to overcome. It was met in the apparent impossibility of confining the high tension flow to the conductors. In my early experiments I covered them with the best insulating material, several inches thick, but it was of no avail. Finally my efforts were rewarded and I found a simple and perfect remedy.
An idea of the underlying principle of the invention and its practical significance may be conveyed by an analogue. Alternating currents transmitted through a wire can be likened to pulses of some liquid, as water, forced through a woven hose So long as the pressure is moderate the fluid entering one end will be integrally discharged at the other, but if the pressure is increased beyond a certain critical value the hose will leak and a large portion of the fluid may thus be wasted. Similarly in electric transmission, when the voltage becomes excessive the prison walls of the dielectric yield and the charge escapes. The loss of energy occasioned thereby, although emphasized by engineers, is not a fatal drawback; the real harm lies in the limitation thus imposed to the attainment of many results of immense value. Now, what I did was equivalent to making the hose capable of withstanding any desired pressure, however great. This was accomplished by so constructing the transmitting conductor that its outer surface has itself a large radius of curvature or is composed of separate parts which, irrespective of their own curvature, are arranged in proximity to one another and on an ideal enveloping symmetrical surface of large radius. These parts may be in the shape of shells, hoods, discs, cylinders, or strands, according to the requirement in each special case, but it is always essential that the aggregate outer conducting area be considerable.
I believe that many arts and industries will be revolutionized through the application of the enormous electric pressures which are easily producible by this means, but perhaps the purely scientific results will be more important than the commercial.
New York, September 23.