US730601A - Lightning-arrester. - Google Patents

Description

To Ground.

No. 730.601. PATENTED JUNE 9, 1903.

' L. BELL.

LIGHTNING ARRESTER.

APPLICATION FILED APR. 5, 1900- N0 MODEL,

. Witnesses. Inventor.

%W Qm Louis Bell.

UNITED STATES LOUIS BELL, OF NEWTON CENTER,

Patented June 9, 1903.

PATENT OFFICE.

MASSACHUSETTS, ASSIGNOR TO THE LlGHTNlNG-ARRE ST E R.

SPECIFICATION forming part of Letters Patent No. 730,601, dated. June 9, 1903.

Application filed April 6, 1900.

To all whom, it nttty concern:

Be it known that I, LOUIS BELL, a citizen of the United States, residing at Newton Center, county of Middlesex, State of Massachusetts, have invented certain new and useful Improvements in Lightning-Arresters, (Case No. 1,343,) of which the following is a specification.

The object of this invention is to provide a lightning-arrester which may act in the dual capacity of protecting the line against excessive charge due to a severe lightning-stroke and at the same time act as a discharger for such static or other minor disturbances as may be due to abnormal working conditions, distant lightning, &c.

In .lightning-arresters as commonly constructedifthe air-gapbeadjustedtopermitdischarges due to resonance conditions of the line in case of alternating-current systems or to abnormal voltages arising from other 'causes.-

as, for example, by induction from-a distant stroke oflightning-unlessinductance or very high resistance is interposed in series with the air-gaps there is a more or less continuous discharge from the line, that keeps the apparatus in almost continuous action and is a great nuisance, and the introduction of inductance to prevent this constant annoyance chokes the discharge-path for a lightning stroke and endangers the safety of electrical apparatus in circuit. The frequency of oscillation due to a lightning-discharge is so high and the volume so considerable that a free path is necessary in order to render the lightningarrester of real service.

I provide an instrument which affords a path of ready discharge to the line under abnormal working conditions and which also effectually relievesit of a charge due to lightning. In effecting this result I provide two paths to earth, in one of which is included a spark-gap or aggregate striking distance of considerable length, greater than can be jumped by a charge due to abnormal fluctuation of'working potential, but which will afford a comparatively easy path for a lightning-discharge, and in shunt relation to this gap or part of it I provide a circuit of limited conductivity, preferably composed partly of inductance and partly of resistance, which serial no. 11,638. (No model.)

permits a discharge of currents of moderate freq'uency,.but effectually excludes from that path the high-frequency oscillations due to lightning. My organization becomes, in fact, a sort'of elcctrodynamic sieve, keeping the line pretty well discharged all the time, but through so high a resistance as to produce no disturbance of its working condition, and at the same time giving an easy path to earth for heavy discharges, such as those due to a "lightning-stroke.

The novel featuresofmy invention will be more particularly described hereinafter and will be definitely indicated in the claims appended hereto.

The accompanying drawing is an illustration ofa construction embodying my improvemen ts, in'which 1 1 1 1 1 represent a group 7 of conductive dischargers, formed by brass cylinders mounted on an insulating-base and with 'a short air-space between their adjacent faces, the sum of the spaces being such that abnormal fluctuations of the line-potential minor abnormal voltage will be insufficient to jump. In series with this group ofdischargers is placed an ohmic resistance 2. In shunt relation to a part of the dischargers is placed an inductance 3 and an'ohmic resistanceornon-inductive"impedance 4: of high value. The ground connection is led off from the lower part of the resistance 2. As a convenient formof resistance I prefer to employ rods formed of a mixture of graphite and clay uniformlyv commingled and subjected to a high. pressure and then baked, producing a resistancestick or rod which is cheap and effective. These are mounted in frames, so as to be connected in series,-'the alternate ends of adjacent sticks being crossconneoted by brass plates 5 5 &:c. The inductance is preferably formed in sections, as indicated in the figure, and Wound over an iron core, the sectional arrangement'providing for a small difference of potential between adjacent convolutions of the winding, and therefore permitting the coil to be cheaply made and at the same time reducing-liability of puncture with inexpensive insulation. The striking distance of the gaps, which include the inductance in their path to earth,

- due to the generators of the system or other should be a little more than that required for the voltage of the line to jump, and the striking distance of the whole range of gaps may be, say, five-eighths of an inch or a little more for a system of ten thousand volts. 'lhus abnormal line conditions due to minor resonance effects in an alternating system or other causes of extraordinary potential will find a comparatively easy discharge over the spark-gaps provided by a few of the dischargers and including the inductance and high resistance, whereas the impedance offered by these latter will be sufficient to prevent any considerable waste of energy; but although this path is comparatively free for currents of commercial frequencies it forms an almost perfect barrier against the enormous frequencies of lightning. For the latter, however, there is open the path through the whole group of dischargers in series or cascade and through the smaller resistance 2. This is made of larger cross-section than the resistance 4 in order to accommodate a discharge of considerable volume. It is well known that a lightning-discharge will leap a long air-gap in preference to traversing a coil of a few turns. The value of the resistance may be varied within considerable limits. In a transmission system employing ten thousand volts the section 4 might be composed of ten five-hundred-ohm-resistance pencils and the resistance 2 of two-hundredand-fifty-ohm pencils, and the aggregate gap of the Whole range of dischargers might be, as before intimated, five-eighths of an inch or a little more.

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

1. A protecting device for electric circuits, comprising a plurality of conducting-pieces separated by gaps, a resistance in series with saidconduoting-pieces, and a circuit of limited conductivity in shunt about some of said conducting-pieces, said circuit including one or more resistance bodies of refractory material.

2. A protecting device for electric circuits comprising a plurality of conducting-pieces separated by gaps, one or more infusible or refractory resistance bodies in series with said conducting-pieces, and a circuit including one or more infusible or refractory resistance bodies in shunt to a portion of said conducting-pieces.

3. A protecting device for electric circuits comprising a plurality of conducting-pieces separated by gaps, current-limiting means in series with said conducting-pieces, and a circuit containing an inductance device and a resistance device in shunt to a portion of said conducting-pieces.

4. In a protecting device for electric circuits, the combination of gaps, and a circuit in parallel relation to a portion of the gaps and including an inductance device and a resistance.

5. In a protecting device for electric circuits, the combination of one or more series gaps, a plurality of parallel paths in circuit with said gaps, one of said paths including one or more resistance bodies, each in the form of a pencil or rod, and an infusible current-limiting body also in circuit with said gaps.

6. A protecting device for electric circuits comprising two non-identical paths to earth, both of which paths include in common a spark gap or gaps and a resistance, and one of said paths a sectionally-wound inductancedevice not included in the other path.

In witness whereof I have hereunto set my hand this 3d day of April, 1900.

LOUIS BELL. Witnesses:

GUY CUNNINGHAM, AGNES GODBOLD.

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