US932112A - Lightning-arrester. - Google Patents

Description

R. A. FESSENDEN.

LIGHTNING ARRESTER. APPLICATION FILED MAY 9 1908.

Patented Aug. 24, 1909.

WITNESSES: INVENTOR,

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REGINALD A. FESSENDEN, OF BRANT ROCK, MASSACHUSETTS.

LIGHTNING-ARRESTER.

Specification of Letters Patent.

Patented Aug. 24, 1909..

Application filed May 9, 1908. Serial No. 431,943.

To all whom it may concern:

Be 'it known that I, REGINALD A. Fas- SENDEN, a citizen of the United States, residing at Brant Rock, in the State of Massachusetts, have invented a certain new and useful Lightning-Arrester, of which the following is a specification.

' My invention relates to safety devices for electrical'circuits and particularly to means for preventing injury by abnormal voltages.

T e primary object is to rovide means for safe-guarding against t e destructive efiects of lightning or other electrical discharges.

The invention is illustrated in one form in the accompanying drawing which is a diagram illustrating 'a suitable type of apparatus for practicing the invention.

Lightning arresters of the usual discharge type now known have the disadvantage that upon discharging they themselves set up oscillations in the circuits in which they are placed and such oscillations are liable to destroy the insulation of suchcircuits. When resistances have been used in connection with these lightning arresters, there is al-- ways the danger of the resistance being too great to' discharge the impulses with sufficient rapidity.

I overcome the above objections, and gain other advantages by making use of a discharge gap so designed that it will break down at an approximately fixed voltage and immediately restore itself with great rapidity, and by shunting such a ga with a circuit which contains capacity, in uctance and resistance so as to form a circuit which would buc be highly oscillatory but for the presence of the resistance, and this resistance is so adjusted as to make the circuit ractically nonoscillatory, and thereby absor ing the energy of the discharge in the resistance. The resistance is so constructed as to be capable of absorbing large amounts of energy without injury.

The principle of the apparatus may be roughly illustrated by the analogy of emptying a tank of water ste by step by means of an automatic tilting ucket. That is, we mayfonsider the capacity as analogous to the ct, the line struck by lightning discharge as" analogous to the tank of water, and the discharge ap as analogous to the tilting mechanism y which the bucket is automatically emptied when it is full and immediately restored to its original position 14, 15 preferably made of sheet iron.

ready to be filled again. In the drawing I show a transmission line 11, connected by a conductor 12 to a discharge gap 19, which is placed in the reservoir 20, filled with compressed air at a pressure of say about eighty pounds or more, which may be indicated by the gage 23. The leading-in wires are supported in the reservoir 20 by orcelain insulating bushings 21, 22, and t e conductor is grounded at 24. Such a compressed air discharge gap breaks down at a very definite potential, as explained in my orior patent 706 ,741 and it has extremely little resistance whenthe discharge is passing; consequently comparatively little heat is produced in the reservoir 20. This gap also restores itself with very great rapidity immediately upon cessation of the discharge or u on the potential falling below a certain va ue.

In shunt to the spark ap 19, I place a large capacity 25, forme in any suitable way as of wires, or, as here shown, by pla i tles e alternate plates 14 are mounted on and connected to conductors 16, 16, and intermediate plates 15 are mounted on and connected to conductor 17, 17'. These conductors may be made out of wrought iron tubin Also connected to the gap and in circuit wit the capacity I place reslstances 13 and 18, having inductance and formed of a number of wires in arallel. The material of the wires prefera ly has a high melting point and the resistance is therefore able to absorb a large amount of energy without being fused. The resistance of 13 and 18 is so adjusted in connection with their inductance and in connection with the large capacity 25 as to make the shunt circuit almost dead-beat or at least greatly-dampened.

In operation, when the line wire 11 is raised to an abnormal potential, as for example by a lightning stroke, the discharge current flows through the conductor 12 and inductive resistance 13 and charges the condenser 25 until its potential reaches such a point as to cause a discharge across the ap 19. The condenser itself being there ore discharged at the same time, the energy stored up in it is absorbedcin-the inductive resistances 13 and 18. As soon as one discharge has passed, the condenser 25 is again charged, and this process is repeated until the abnormal charge of the line 11 is completely dissipated tothe earth. The line potential does not continue to pass across gap lowin g 1. i lightning arrester comprising a discharge gap adapted tohe automatically re stored to original insulating resistance with great rapidity, and a shunt circuit around the gap containing inductance, capacity and resistance, said resistance he' proportioned tomake the shunt circuit a ighly dam d one, and being constructed to safely abso a large amount of energy, substantially as de scrlbed. v

2.. In a lightning arrester, a reservoir of compressed :air, a discharge gap -therein, and a highly damped oscillatory circuit shunted seams around thega the terminals of the gap be ing respectlve ycconnected to ground and to the device to be'protected.

3. A lightning arrester comprising a dis= charge gap and a circuit shunted around the gap and made non-oscillatory and containing a condenser.

a. A lightning arrester comprising the combination of a rapidly self-restoring compressed air discharge gap anda circuit around the gap containing a capacity and inductive resistances on each side of the capacity, adjusted to absorb .ener y of dise the cizrcharge from the capacity, and m cuit non-oscillatory.

In testimony whereof I have hereunto signed my name in the presence of two subscribed witnesses.

' REGINALD A. FESSENDEN Witnesses:

Jassm E. BENT, AGNES M. (karma.

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