US1289521A - Lightning-arrester. - Google Patents

Description

H. A. NEWCOMB.

LIGHTNING ARRESTER.

APPLICATION FILED MAY a. 1915.

Patented Dec. 31, 1918.

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INVENTOR Hare/a A. Npwcomh WITNESSES 1 TTORNEY v UNITED STATES PATENT OFFICE.

HAROLD A. NEWCOMB, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA.

LIGHTNING-ARRESTER.

To all whom it may concern:

Be it known that I, HAROLD A. NEWCOMB, a citizen of the United States, and a resident of Wilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Lightning- Arresters, of which the following is a specification.

My invention relates to protective devices for electrical circuits, and it has particular reference to that class of apparatus commonly designated as lightning arresters, although it will be understood that the function of these devices is not confined to the safe dissipation of lightning disturbances only but also includes the safe dissipation of discharges arising from all over-voltage disturbances.

It is important that adevice of the afore mentioned character shall act as a sort of electrical safety valve to-dischargeto ground or to dissipate, in some way, all hlgh-potential disturbances without allowing the line current to flow continuously over the path initially established by the high-potential discharges. In accordance therewith, my lightning arrester precludes the line current from maintaining the are established by the high-potential discharges. Y

My invention comprises a lightning arrester consisting of an evacuated bulb or envelop in which the pressure is considerably below normal atmospheric pressure. The electrodes. one of which is associated with a line conductor in any well-known manner, such as being connected thereto directly or through a spark gap, or through a resistor, and the other of which is adapted for a ground connection, furnish a low-resistance discharge path for over-voltage disturbances, but impose a prohibitively high-resistance path to the continuous flov v of line current of normal voltage.

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 cross-sectional view of a device embodying a. form of my invention, and Fig. 2 is a modified form of the device shown in Fig. 1.

'By referring to Fig. 1, it will be noted that a line conductor 1 which, in this instance, is shown as being directly connected to a protective device 2 embodying a form of my Specification of Letters Patent. Patented Dec, 31, 1918.

Application filed May 3. 1915. Serial No. 25.466.

invention, is connected to ground 3 through a discharge path 4 extending between two electrodes 5 and 6 of the device 2. The device 2 comprises an evactuated glass bulb or envelop 7. The electrode 5, which is of filamentary form, is sealed in the envelop 7 in any well known manner. In a device constructed by me, I used the well-known tungsten seal which I have found very effective in withstanding hard usage. Lava buttons 8 encircle the filament legs at the points where they project through the Wall of the glass envelop 7 in order to prevent any are flowing from the filament 5 from coming into contact with glass projections 9. The electrode 6 is, in all respects, similar to the electrode 5. I have found the most satisfactory filaments for use in my device to consist of tungsten, but it is conceivable that, as will be hereinafter explained, the filaments 5 and 6 may comprise other materials which will operate satisfactorily.

A high-potential disturbance occurring upon the conductor 1 will pass freely through the discharge path 4: between the electrodes 5 and 6 to ground. Inasmuch as the filaments 5 and 6 are of comparatively small cross-sectional area, they will be rapidly heated as the discharge currents HOW to ground 3. When the filaments have approached an incandescent heat, the arcs are suppressed or choked, and the line current is precluded from flowing to ground over the path initially established by the highpotential disturbances. I have found that, when the filaments 5 and 6 have reached incandescence, the arcs extending therebetween are completely disrupted and suppressed.

In Fig. 2, the electrode 6 of Fig. 1 is replaced by an electrode 10 which comprises a pool of mercury. A conductor 11, extending into the pool of mercury and sealed into the glass envelop 7, constitutes a means for connecting the electrode 10 to the ground 3. The action of this device I have found to be similar to that desdlribed in connection with the device of Fig 1, the electrodes 5 and 10 serving. in this instance, to suppress the are when the filament 5 has been heated to incandescence.

' While I am not prepared to state, with certainty, the theorybf operation of my device, the result appears to be due to the emission of an excess of negative ions from the discharge path 4.

electrodes 5 and 6 when said electrodes are heated to incandescence. The first flow of currents through these electrodes is unimpeded, but, after the electrodes have become heated to incandescen'ce, the negative ions or electrons emitted therefrom appear to offer an extremely high impedance to the continuance of the current flow through the When both electrodes are of filamentary form, as shown in Fig. 1, they tend to become negative simultaneously. In the device shown in Fig. 2, the mercury pool 10 always acts as a cathode and, consequently, when the filament 5 is transformed from an anode to a cathode by being heated to incandescence, both of the electrodes 5 and 10 are negative, as explained above.

Apparently, during the maintenance of the high voltage, the forces acting upon the electrons within the device are sufiicient to carry the said electrons from one electrode to the other, thus producing the double action of maintaining the respective electrodes at electron-emitting temperatures by the electronic bombardment thereof and further producing currentflow by said bombardment. As soon as normal voltage is restored, the forces acting upon the electrons within the discharge device are insuilicient to move the electrons from one electrode to the other against the repellant action of the large number of electrons in the neighborhood of the second electrode. Furthermore, at the lower voltage, the electronic bombardment is much less powerful, thus failing to maintain the electron-emitting temperatures of the respective electrodes. The joint effect of these factors is to produce an extremely rapid collapse of the vapor conductivity and the prompt suppression of l ne current flow after the cessation of the llghtning discharge.

it will be understood that the electrodes 5,; or those which are directly associated with the line conductor 1, should be made of such a form that they readily become heated when high-potential disturbances flow through them. I have found that electrodes made in the form of filaments, such as are embodiedin incandescent-lamp structures, are particularly adapted for use in my llghtnlng arrester. It will be understood, however, that the cross-sectional areas of the filaments 5 and 6 are dependent upon FhG SQI'VlCG in which my lightning arrester 1s to be used.

Tungsten is a preferred material for the filamentary electrodes embodied in my invention because it may be obtained readily in commerclal quantities and is eflective in service, since it may be continuously operated wlthout deteroriation, irrespective of the number and character of the disturbances to which it may lee-subjected. I desire mas er it to be understood, however, that other materials which emit an excess of negative ions, when heated to incandescence, such as cerium oxid and thorium oxid, may be employed, though probably less suitable than tungsten for use in commercial apparatus.

If either cerium oxid, thorium oxid or other material of similar character is employed, it will preferably be applied as a surface coating to a metal conductor because such 'materials are not conductors of electricity under normal conditions. H such coated conductors are employed as filamentary electrodes of my lightning arrester, the operation will be substantially the same as has already been described.

While the envelop 'Y'may be evacuated, under certain conditions, it may be advisable to provide means for regulating the pressure therein in order to eitectively extinguish the discharge arc. For this purpose, ll may provide an extension 12 for the envelop 7 of Fig. 1. and in the extension, I may place a body of salt 13, such as zinc chlorate or calcium chlorate, or any other salt having a vapor pressure of substantially one millimeter of mercury through moderate ranges of temperature. In this manner, the pressure within the envelop 7 may be reguate While ll have explained. Somewhat in detail. the assumed theory of operation of my device. ll do not desire to have my invention limited in any manner or degree be ause of such theory. Inasmuch as a device constructed in accordance with the above mentioned description is efi'ective in suppressing arcs, it is not of material consequence whether or not the theory, as stated in my description, is. in all respects. correct.

It will be understood that many modifications may he made without departing fromthe spirit and scope of the -appended claims.

I claim as my invention:

1. The method of operating a vacuumtvpe lightning arrester which comprises producing an excess of ions therein during the di charge of exce s voltage. whereby the suhsenuent flow of line current is retarded.

2. The method of operating a lightning arrester having a discharge path in the form of a vapor conductor which comprises building up a space charge therein during the excess v'olta ge discharge period, whereby the subserment flow of line current is retarded.

3. The combination with an electrical system subject to normal voltage and to transient surges of abnormally high voltage. of means for discharging said surges without diverting enera'vat normal voltage comprising two electrodes. spaced apart sufficiently to prevent the formation of a di charge therebetween at normal voltage but to pera ase eat pacity so that they are raised to an electron emittingtemperature during the discharge of abnormal voltageand by the subsequent free emission of electrons retard the passage of line current.

4:. The combination with an electrical system subject to normal voltage and to transient surges of abnormally high voltage, of means for discharging said surges without diverting energy at normal voltage comprising two electrodes, spaced apart sufficiently to prevent the formation of a discharge therebetween at normal voltage but to permit a discharge at abnormal voltage, said electrodes having such heat capacity and radiation that the electronic bombardment'at said abnormal voltage suffices to maintain them at an electron-emitting temperature but the electronic bombardment at line voltage fails to maintain them at an electron-emltting temperature, whereby the line voltage prising two spaced electrodes of such heat capacity and heat radiation that, during periods of high voltage, the initial electronic bombardment between. said electrodes is suflicient to maintain them at electron-emitting temperatures but during periods of low voltage the initial electronic bombardment is insufficient to maintain said electrodes at electron-emitting temperatures.

In testimony whereof, I have hereunto subscribed my name this 27th day of April,

' HAROLD A. NEWCOMB.

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