US1212746A - Lightning-arrester. - Google Patents

Description

D. C. DAVIS.

LIGHTNING ARRESTER.

APPLICATION mm APR.29. 1915.

1,212,746. Patented Jan. 16, 1917.

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UNITED STATES PATENT OFFICE.

DAVID C. DAVIS, 01 SWISSVALE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VAN IA.

IiIGI-ITNING-ARRESTER.

Specification of Letters Patent.

Patented Jan. 16, 1917.

Application filed April 29, 1915. Serial No. 24,722.

' horn-gap lightning arresters for the protection of electrical circuits. It will be understood, however, that devices constructed in accordance with my invention may be used in connection with high-voltage air-brake switches and are blowout rectifiers. Again, a device constructed in accordance with my invention may be utilized in conjunction with a horn-gap terminal member of the usual type to form a lightning arrester that will adequately protect electrical circuits sub jected to certain disturbances which are not of a serious character. In the various applications of my lightning arrester, the func tions performed by it are practically identical, it being desired, in all cases, to quickly and effectively extinguish the arc inssuch manner as to create no serious oscillations or surges upon the associated electrical circuit.

When discharges from electrical circuits occur over horn-gap arresters of the ordinary type, the arcs which are formed be tween the terminals are frequently of sufficient duration to create sefious disturbances or surges in the circuit. As a result, the insulation of the circuit is subjected to abnormally high strains. It is, therefore, desirable to insert a high resistance into the circuit as the are lengthens when it ascends upon the horn-gap members, thus cutting down the current value ofthe are before it is finally broken. This is an important con sideration in the practical operation of lightning arresters and high-voltage airbrake switches, since the discharge current, at the instant of the final break, is greatly reduced because of the high-resistance. path of the arc. Consequently, the finalextinguishing of the arc does not set up line oscillations and surges. Moreover, it is desirable to extinguish the are as soon as possible, in order to preclude a continuous flowof line currents of normal voltage across the arc to ground. Under certain operating conditions it is necessary to maintain the horngap members cool and especially the arcing surfaces thereof.

By means of my invention, discharges may bequickly and effectively extinguished, and the value of the current flowing across the are just before its final break may be reduced sufficiently low to preclude the crea- I tion of any oscillations or surges upon the circuit. In addition thereto, I provide means whereby the arcing surfaces of the discharge terminals may be maintained cool when such conditions arise as to warrant such cooling effects.

For a better understanding of the nature and scope of my invention, reference may be had to the following description and the accompanying drawing in which- Figure 1 is a view, somewhat diagrammatic and partially in section,'of a horngap lightning arrester constructed in accordance with my invention, and Figs. 2 and 3 are cross-sectional views of the horn-gap members shown in Fig. 1.

An electrical circuit which it is desired to protect from the destructive effects of static discharges comprises a line conductor 1 that is supplied with electrical energy from any suitable source, and a protective circuit 2 which comprises a lightning arrester 3 that is connected between the conductor 1 and the ground 4. The lightning arrester 3 comprises a pair of horn-shaped terminal members 5 and 6 which are so ar ranged that corresponding ends 7' and 8 minal members, is a strip 12 of refractory material of high specific resistance such, for example, as carborundum. The cross-sectional area of the high-resistance conductors 12, which constitute the discharge terminals for the arcs, may be so varied as to be as small or as large as desired, and to conform to the conditions of service to which the device is to be applied. Of course, it will be understood that the line conductor 1 and a grounded conductor 13 are electrically connected to the high-resistance conductors 12 at the lower portions 7 and 8 of the horn members. Each of the tubular members 5 and 8 is provided with inlet and outlet openings 14; and 15 for the circulation therethrough of any suitable cooling fluid, such as water, oil, etc.

From the foregoing description, it will be apparent that any are extending between the terminals 5 and 6 is influenced by the magnetic action of the current flowing along the conductors 12 and in proximity to the magnetizable material 10. In addition thereto, the are is further attenuated by the heat of the ascending gases. Moreover, as the arc lengthens, a high resistance is introduced into the circuit by reason of the increased length in the circuit of the conductors 12, which, as before mentioned, are of high specific resistance. Moreover, the arcing surfaces are maintained cool by reason of the circulation of the cooling fluid through the tubular members 10.

In Figs. 2 and 3, I have shown, in cross section, various forms which the members 5 and 6 may assume in a practical structure. In Fig. 2, a wall 16 of the tubular member 10 is relatively thin, as compared with a wall 17, in order that the cooling effects upon the conductor 12 may be ample. The wall 17 is relatively thick in order to provide a satisfactory magnetic action upon the are. In Fig. 3, the conductor 12 is centrally disposed in a recessed portion 18 formed in the arcing face of the terminal member. The conductors 12 may be self-supporting or so associated with the insulating material 11 as to be supported thereby.

When dependent upon extraneous means for mechanical support, the conductors 12 may be of small cross-sectional area and, under these circumstances, may be composed of a material having a lower specific resistance than would otherwise be possible. F urthermore, by providing a discharge member of small cross-sectional area and consequently, of a small heat capacity, and by constructing the insulating layer 18 of a material that is a rather poor conductor of heat, the discharge members 12 will be heated by any are which persists for an appreciable length of time. When the members 12 are composed of material which is a conductor of the first class, the heat generated therein will cause a rapid increase in their resistance, with a resultant increased choking effect on the arc. After rupture of the are, the heat absorbed by the conductors 12 will be dissipated by the cooling means hereinbefore mentioned. It will be noted that, in this manner, a selective action may be exercised, in that discharges of small energy will be suppressed without appreciably heating the discharge terminals, whereas, discharges of considerable energy will heat the conductors 12 and, therefore, encounter the enhanced suppressing effect resulting from such heated discharge terminals.

lVhile I have shown and described, in detail, one embodiment of my invention, it will be apparent that many modifications may be made without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. A horn-gap discharge terminal comprising an elongated member of magnetizable material, and a high-resistance and refractory conductor disposed thereupon but insulated therefrom, said refractory conductor constituting the discharge terminal.

2. A horn-gap discharge terminal comprising an elongated tubular member of magnetizable material, said tubular member having inlet and outlet openings for the circulation therethrough of cooling fluid, and a high-resistance refractory conductor disposed longitudinally thereon but insulated therefrom, said high-resistance conductor constituting a portion of the discharge terminal.

3. A lightning arrester comprising diverging terminal members of magnetizable material, and a refractory conductor of high specific resistance disposed on the arcing surface of each of said terminal members but insulated therefrom, said high resistance conductors constituting the discharge terminals for the are.

4. A lightning arrester comprising diverging terminal members of magnetizable material and tubular form, said tubular members being provided with inlets and outlets for the circulation therethrough of cooling fluid, and refractory conductors of high specific resistance disposed on the arcing surfaces of said terminal members, said highresistance conductors constituting the discharge terminals for the are.

5. The combination with electric circuit conductors, of a lightning arrester which affords circuit connections between the same and ground, said lightning arrester comprising diverging terminal members of magnetizable material, and a refractory conductor of high specific resistance disposed on the arcing surface of each of said terminal members but insulated therefrom, said highresistance conductors constituting the discharge terminals for the arc, whereby the resistance of the ground circuit is caused to increase after the occurrence of a disruptive discharge.

6. A lightning arrester comprising diverging terminal members of tubular form composed of a Inagnetizable material, said terminal members being provided with inlets and outlets for the circulation therethrough of cooling fluid, the arcing surfaces of the terminal members being composed of a refractory material of relatively high specific resistance.

7. Alightning arrester comprising diverging terminal members of magnetizable material and discharge portions thereof which comprise conductors mounted upon, but insulated from, the said terminal members, said conductors being of the first class of small heat capacity whereby the heat generated therein will rapidly increase with the persistence of the discharge.

In testimony whereof, I have hereunto subscribed my name this 20th day of April DAVID C. DAVIS.

Copies of this patent may be obtained for flve cents each, by addressing the Commissioner oi Patents, Washington, D. 0.

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