US1157344A - Means for preventing corona loss. - Google Patents

Description

E. THOMSON.

MEANS FOR PREVENTING CORONA LOSS. APPLICATION FILED DEC. 28, 1912.

1,157,344. Patented 001. 19, 1915.

; --/LW His fitter-11% 'illrl'rrnn raranr oirmo ELIHU THOMSON, OE S'WAM'BSOOTT, IVIASSACHUSETTS, ASSIGNOR TO GENERAL ELEC'EBEC COMPANY, A GORI'EORATION OF NEJV YORK.

MEANS FOR PREVENTING CORONA LOSS.

To all whom it may concern:

Be it known that l, ELIHU THOMSON, a citizen of the United States, residing at Swampscott, in the county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Means for Preventing Gorona Loss, of which the following is a specification.

My invention relates to electric conductors, and more particularly to conductors thereby enlarging the luminous zone of corona until these zones have spread to such an extent they merge into each other, whereupon a conducting path between the wires is established and the lac may be short-circuited. T his phenomenon may also be considered with reference to the electrostatic field which surrounds two conductors carryin current. Each conductor is sur rounded by a magnetic field which may be represented by lines oi"- force -forming circles around each conductor, while at the time the voltage between the wiresproduces a condition electrostatic stress which may be represented by lines of electrostatic force issuing from the conductor perpendicular to the surface of the wire and intersecting the circles which represent the lines of magnetic force around the conductor. The density of lines of electrostatic force will be pro portional to the voltage per centimeter length of the electrostatic circuit-. and, if the number of lines or" electrostatic force per inch in air rises beyond a certain critical value, the air breaks down For any given size oi wire and distance apartoi wires, there is a certain critical volt age at which the critical density or" the electrostatic lines of force or the critical voltage gradient is reached, whereupon the air breaks down and luminosity begins. This is the critical voltage at which corona appears. At higher voltages the corona extends to Elpecification of Letters Eatent.

Patented @ct. 18 1915.

Application filed December 28, 1912. Serial 1T0. 739,006.

corona formation begins is to raise the voltage between the wires gradually and in darkness until the luminosity begins. It is found that the point between where the wire is dark and where it is luminescent can be measured within the fraction of one per cent. a

At high voltages a small current is suficient to convey a large amount of energy and therefore at high voltages a Small conductor is ordinarily large enough to carry as much energy as is usually transmitted over a conductor. As the critical voltage of a small wire is lower than that of a large wire, the corona losses will be prohibitive on high voltage conductors, such as the wires of'a transmission line unless the conductors are much larger than is necessary to make them strong enough to resist mechanical strains or to have sufiicient current carrying capacity.

The object of my invention is to provide a conductor containing only the minimum amount of metal necessary to carry the current and with a greater virtual diameter than actual diameter. To such a conductor much higher potentials can be applied without causing the appearance of corona than can be applied to conductors of the type heretofore used, and therefore the commercial use of potentials much higher thanthose heretofore commonly used commercially becomes teasible.

My invention will best be understood in connection with the accompanying drawing which merely for purposes of illustration shows one of the forms which-at the present time 1 consider to be the best embodiment of the principle of my invention and in which is shown one form of a conductor constructed in accordance with my invention.

in the particular embodiment of my invention shown in the drawing, a conducting element or wire 1 of the proper size to convey the current with proper economy is covered with a conducting sheath 2, which enlarges the virtual diameter or the wire to such an extent t at a voltage much above I suitable conducting material, such, for exthe outside by drawing through dies or any other suitable way, after which it may be slightly impregnated with some compound to preserve it from the weather. Any suitable fibrous material may be used instead of the cotton fiber and may be coated with any ample, as linseed oil, in which fine graphite, lampblack or charcoal has been mixed to form a conductive body. Since the material of the conducting sheath 2 has only to convey at high voltage a very small current from the wire to the outside of the sheath and back again during the alternations in current on the conducting element 1, the sheath need be of only sufficient conductivity to conduct without appreciable resistance losses the exceedingly small amount of current which passes from the Wire 1 to charge the external surface of the conducting sheath 2. The whole covering or conductive sheath of the wire is in effect made up of innumerable radial paths connected in parallel and of a length from the surface of the wire 1 to the outside of the sheath or coating 2. Since all of these paths arein. parallel the resistance to radial c ur-- rentfiow is very slight and at the high voltages for which the conductor is adapted a suificient amount of current will flow with- V out appreciable resistance loss to virtually enlarge the diameter of the Wire 1 to such an extent that corona does'not appear at voltages above the critical voltage of the wire 1 without'the'sheath. The resistance.

losses due to radial current flow are practically nothing. The losses which would'be caused if the conducting coating" were absent and corona were permitted to form around the conducting element '1 are avoided.

My invention may be carried out in many other forms than that shown and described and I, therefore, do not desire to limit myself to the preclse arrangementf' herein set 'forth, but intend to cover all mouincations within the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. A high potential conductor comprising a conducting core, and a non-metallic sheath having suflicient radial conductivity to transmit without resistance loss suflicient current to charge the external surface of said sheath to the potential of said core.

2. A high potential conductor comprising a metal core and a non-metallic sheath having radial conductors distributed through it and in contact with said core to provide a radial conducting path of great totalcross-' section and extending from said core'to the surface of said sheath and having a total cross-section sufiicient to eliminate resistance losses in radial flow of current.

3. A high potential conductor comprising a conducting element and a sheath having sufficient conducting particles distributed through the body thereof along said'conducting element to permit current to flow from said conducting element to the surface of said sheath with no appreciable resistance loss.

4. A high potential conductor comprising a conducting element and a fibrous sheath for said element having conductive particles so distributed'through the body'thereof that radial conducting paths in parallel are formed of such aggregate cross-section that current may flow radially through said sheath with substantially no resistance losses. v

5. In a high potential conductor for transmission lines, the combination with a conducting element, of a fibrous covering for said element having a smooth outer surface and conducting material uniformly distributed through said covering to form radial conducting paths in parallel andenable current to flow radially through said covering with slight loss 'at the normal operating voltage of the. transmission line. In witnesswhereof, I have hereunto set my hand this 24th day of December, 1912. ELIHU THOMSON. Witnesses:

JOHN A. McMANUs, Jr., FRAn H'A'rrna

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