US958454A - Lightning-arrester. - Google Patents

Description

H. C. WIRT.

LIGHTNING ARRESTER.

APPLIUATION FILED DB0.22,1905.

958,454. Patented May 17, 1910.

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WTNESSES- INVENTD F1- @y HERbERTEM/IRT.

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Hummm. l y p 953,454,` specification ef team nant. pratenfeid May 17, l19,10,

g museum sued neemneras, swarm. $92,927. i To all whomitmdy concern: l the tiret gap, thereby de?) roying its electro- -Be itknownthatl, Hnnm'r C. Wm'r, a citizen of the United. States, 'residin at Schenectady, county of Schenectady, .tate of New York, have mvented oertainnew and useful Improvements in .Lightning-Arresters, of `which the following isa specification.

My invention relates todevices for protecting electrical circuits .and apparatus from static and high voltage strains resulting from lightning or other causas` In the design of a successful lightning arrester two important requirements must be satisfied, first, the device -must present a ready path' to ground for static or lother abnorma charges, and second, it must not permit Athe line current to follow through to ground on the arc established by the high potential discharge. lThe apparatus which I have devised for carrying out these two requirements includes a plurality of conducting -members grouped u on an insulating base lto form a plura ty of -spark gaps, and the conductors and gaps are yso proportioned and are in such number that the arrester unit as .a whole maybe connected directly lbetween the line to beprotected and a second conductor, such as ground, without the interposition ofv any series-resistance or other impedance devices which -might, under certain circumstances, cause a choking of high potentialdischarges, especially 'when these ,discharges are of the exceedingly high frequency sometimes en.- countered in lightning arrester work.

When using` a plurality of spark gaps without resistance in series, as .abovedescribed, I find it desirable to utilize the electrostatic capacity of the conductors which form the conducting poles of the several Vspark gaps. .B this arrangement the spark gaps are bro en down successively, and not simultaneously as would, no doubt, be necessary if the electro-static capacity of the conductors w'as not utilized. Thissuccessive breaki gaps was, II believe, first disclosed in a patent to Elihu Thomson, 444,687 of Jan. 13, 1891. The successive reaking down of the several gaps-is, in my opinion, due to Y the-fact .that thestatic charge readily jumps down of the several spark t static resistance, an jectmg the second gap to substantially the full force of the static charge, whereupon the second gap is likewise broken down and permits the charge to pass-on to alli-the gaps isu succession. When this principle is applied to alternatingcurrent circuits the electro-static capacity of the several conducting elementsv of the arrester gives to the discharge paths. certain selective action whereby discharges of a certain frequency-are' ermitted to pass, although the path is su tantially impervious to vdischarges of a'lower frequency. This selective or resonant action ofthe discharge path is of prime importance in preventing the line current from following through on the static I discharge.

My invention embodies novel vfeatures of construction andarrangement and in order that my invention may be better understood, reference will be had to the following description taken in connection with the drawing forming a part of this specification.

Figure 1 is a perspective view of my improved lightning arrester unit; Fig, 2 shows three of these units arranged one above another to form a zigzag path for the discharge current; .and Fig. 3 is a side elevation showlng details of construction.

` The uni-t shownin Fig. 1 comprises a porcelain or other insulating base l, and .a pluralityofmetal cylinders :2 arranged in the form of a V. These cylinders are mounted on suitable pins cemented or otherwise set into the porcelain base and are locked inpcsition by the nuts 4. VI have found that' the diameter and length of these metal cylinders have an important bearing-on their electrostatic capacity, and consequently on the resistance to break down oiiered by the spark gaps which intervene between one cylinder and another. I find that the size and shape say of 1/32, for when so constructed and arranged the electro-static capacity 1s very satisfactory for commercial operation.

By arranging the cylinders as shown in Fi 1 an arc or discharge entering on one sidi of the cylinder is transmitted across the cylinder and leaves at a diainetrically opposite point, and even before the arc or discharge forms there is more or less of a concentration of electro-static energy on those portions of the conducting cylinders which are nearest to adjacent cylinders, it being understood that the electro-static strain or charge is confined principally to the outer surface of each conducting cylinder.

The number of gaps to be used, in each particular installation depends on the voli tage of the circuit, but for a 33,000 volt circult operating at a usual frequency, I find that 624 gaps between lines will break down under abnormal static strain and will satisfactoril break the dynamic arc established by the ine current.

In commercial installations the most destructive effects are produced by high frequency discharges, and the multi-gap arrangement above described, Without series resistance of any kind, is especially suited to readily transmit these discharges. At the same time the arrester forms an adequate rotection against high voltages having a equency of five hundred to one thousand cycles, which might be generated in the line by resonance or other disturbing phenomena more 'or less independent of atmospheric disturbances.

The V shaped arrangement shown in Fig. 1, affords several important advanta es; first, it properly separates the rst and ast cylinders 5 and 6 of each unit so that there is no danger of the discharge jumping across between these conductors in preference to passing across the series of gaps, and second, it places each gap in such a position that the discharge or are which forms is substantially horizontal, and hence is acted upon by a draft of hot air tending to bow it up in the center, thereby increasing its length and forcing it upward over the curved surfaces of adjacent cylinders. As the increase in are length produced by the draft occurs at each spark gap the total increases in arcing distance is very great, and consequently is very effective in producing the' extinction of the are. The V-shaped arrangement also makes it possible to conveniently group the unitsy one above another without the intervention of complicated Wiring or other parts Which would be hard to insulate at the high potentials commonly present in lightning arresters.

I contemplate connecting a group of units as shown in Fig. 2, direct y across between line conductorsy 7 and 8, though it is to be understood that the total number of units thus connected is calculated for each particular installation, and is dependent on the workingvolta el of the line and on other factors of a li ce' nature. For high voltage systems -I may use as many as twenty-ve units arranged in the same manner as the three units of Fig. 2. Instead of connecting the spark ga s between line conductors I may if desire connect a group between each line conductor and ground, thus securing separate paths to ground for each line conductor and atl the same time securing a ath between any two conductors by way o the two corresponding groups, in series.

. As previously stated the electro-static capacity of the cylinders is believed to produce the break down at each gap, these break downs occurring one after another and thereby transmitting to successive gaps substantially lall the electro-static strain to which the first gap was subjected. The total spark gap distance traversed by the high potential discharge is thus made very much greater than the distance which it would jump between two fixed needle points, or in other Words this series of gaps has a very low equivalent spark gap. Not only does my improved arrester provide for a rapid removal of high potential, high frequency charges, but it 1s also'exceedingly effective in suppressing the following line current, and furthermore, suppresses this current almostl at the instant it is formed, thereby preventing sudden current rushes on the system, which if allowed to form might produce oscillations, resonance and other phenomena highly detrimental to rotary converters or other sensitive apparatus operating on the system. l

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

1. In a lightning arrester, the combination of an insulating base, and a plurality of conducting cylinders supported on said base and grouped in two converging rows.

2. In a lightning arrester, the combination of a plurality of units each comprising an insulating base and a lurality of conductin members mounted t ereon, said units being isposed in proximity to each other to form a discharge path for high potential charges, and the end members of adjacent units being separated by-air gaps.

3. The combination with the conductors of an electrical distribution circuit, of a plurality of conducting members spaced apart to form air gaps and grouped to form a zigzag path for high potential discharges from I one of said conductors.

4. In a lightning arrester, the combination of an insulating base and a plurality of conducting cylinders supported thereon, said converging but approximately horizontal l0 cylinders being arranged in two approxi lines und with their axes substantially horimutely horizontal converging lines to permit. i zontal. u rapid circulation of air between said eyl- In Witness whereof I have hereunto set my iuders when an arc forms therebetween. hand this 20th day of December, 1905.

5. In a lightning arrester, the combination HERBERT C. WIRT. of an insulating base, and a plurality of conducting cylinders supported thereon, said cylinders being arranged in a plurality of Witnesses:

BENJAMIN B. HULL, HELEN ORFoRD.

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