US2288050A - Lightning arrester - Google Patents

Description

June 30, 1942, VATTER 2,288,050

LIGHTNING ARRESTER Filed May 17. 1939 WITNESSES: INVENTOR fiw 2/424 ATTORN EY Patented June 30, 1942 UNITED STATES PATENT OFFICE LIGHTNING ARRESTEB.

Application May 17, 1939, Serial No. 274,156 In Germany May 19, 1938 18 Claims.

This invention relates to lightning arresters to be employed primarily for protecting relatively low-voltage direct current lines or apparatus, although it may also be employed for protecting alternating current equipment, and has for a particular object the positive interruption of any power-follow current in the lightning arrester after the surge has subsided.

According to my invention, the lightning arrester, briefly, consists of a ceramic housing provided with terminal electrodes co-nnectible, respectively, to a ground circuit and to the equipment which is to be protected. Within the housing is disposed a movable electrode having a ferrous or magnetizable portion. During a discharge of the arrester, the movable electrode is in arcing relation to one or both of the terminal electrodes, and can be moved by a coil about the housing so that the space between the movable electrode and one of the terminal electrodes can be considerably increased to the extent of interrupting the flow of current. The ground circuit is such that when the arrester breaks down upon the occurrence of an over-potential or surge, a voltage drop in the grounding circuit will serve to energize the coil.

In one embodiment of my invention, the arc between the fixed and movable electrode is suddenly and considerably decreased in size in a manner to aid the extinction of the arc. I accomplish this by causing a tip of the movable electrode to enter a cut-out portion or cavity in the form of an opening or bore in an insulating member within the arrester so that the arc, in effect, is cut off.

Other objects and novel features of my invention will be apparent from the following description thereof, which is to be taken in conjunction with the drawing, in which:

Figure l is a longitudinal cross-sectional view (I of one form of lightning arrester embodying the principles of my invention;

Fig. 2 is a schematic diagram of a protective circuit including the lightning arrester; and

Figs. 3 and 4 are longitudinal cross-sectional views of modified forms of an arrester.

Referring more particularly to the embodiment disclosed in Figure l, the housing consists of an open-ended tube l of some ceramic material,

preferably wet-process porcelain. In the ultimate arrester, the ends of the tube are sealed by terminal electrodes comprising a metal cap 2 at one end of the tube and a metal cap 3 at the other end. The caps preferably are formed with cylindrical portions at their centers into which are F secured conductors 4 and 5. The end terminals also have protruding cylindrical electrode members 6 and l conductively connected to the caps, and formed preferably of some non-arcing and arc-extinguishing metal, such as, for example, brass. The complete terminal electrodes are soldered to the tube I so as to form a gas-tight enclosure, and this may be accomplished in any suitable manner as, for example, by coating the ends of the porcelain tube l with a metal layer which will solder to the caps 2 and 3.

As may be observed in Fig. 1, the electrodes 6 and I extend partially into the tube l to abut ceramic insulating inserts or members 8 and 9 fixed in the tube I in axially spaced relation. Each of the members 8 and 9 is provided with an axial bore or opening I0 and II, respectively, in which slide the stub electrode sections l2 and I3, respectively, of an intermediate connecting electrode indicated in its entirety by the reference numeral M. A ferro-magnetic cylinder l5 completes the structure of the connecting electrode In the normal, vertical, operating position of the arrester, the cylinder l5 rests upon the member 9 so that the lower part of the stub electrode [3 is axially disposed somewhat within the cylindrical electrode 1, and a tip of the other stub electrode [2 is similarly disposed within the electrode 6.

A coil I6 is secured externally about tube l and disposed in a manner that, when energized, it will attract the magnetizable cylinder l5 so as to raise the connecting electrode M. The space I! between the members 8 and 9 is sufficiently large so that the upward movement of the cylinder IE will carry the stub electrode is completely into the bore ll of the member 9.

Fig. 2 shows schematically a manner in which the lighting arrester of Fig. 1, as well as those of Figs. 3 and 4, to be subsequently described, may be connected in a protective circuit. The line I9 is indicative of a direct-current transmission wire or other apparatus or equipment which is to be protected against overvoltage. It is connected by a conductor 20 to the conductor 4 of the upper terminal apparatus, and thereby is conductively connected to the inner fixed electrode 6. The other terminal of the arrester is connected to a resistor 2| which, in turn, is connected to ground through a conductor 22. The coil it is connected across the resistor 2|, or a part thereof, so that upon breakdown of the arrester, the current flowing through the resistor will establish a potential suflicient to energize the coil Hi.

The operation of the arrester of Fig. 1 should be obvious to those skilled in the art. Upon the occurrence of an overvoltage, a ground circuit is established including an are between the electrode 6 and the tip of the stub electrode l2, current continuing across the rest of connecting electrode M to the tip of its other stub electrode l3. the breakdown path between the electrode 1 and the tip of stub electrode l3, and a path to'ground through the resistor 2|. Thesurge or overvoltage may be of practically instantaneous appearance, but the power follow. current will be Sill-1 ficiently continuous to energize the coil Hi, thereby raising the connecting electrode M. The raising of the connecting electrode 14, of course, pulls the stub electrode l3 thereof into the bore ll, thereby elongating the arc breakdown path betweenthis stub electrode-and the electrode 1. When the arc gets sufiiciently long so thatit cannot be sustained by the normal voltage of the system,- it will interrupt, thereby deenergizing the coil IB and permitting the center electrode to restoreto normalposition, awaiting a subsequent over-voltage. 1

. In order toaid thev extinguishing of the are between the electrode 1 and the stub electrode l3, the bore ll of the member 9 is made only slightly largerthan the stub electrode [3 so that a cutting offaction occurs when the tip of the stub electrode is immersed in the member 9. To aid in the extinction of the arc, the extreme tip of the stub electrode I3 may be provided with an attachment 23 of asemi-conducting or insulating material. A ceramic substance, similar to that of the tube 1, may be employed.

It-may be observed that in the movement of the connecting electrode 1 5, the arc path between the electrode 6 and the stub electrode I2 is not changedto any appreciable extent, since the stub electrode merely rises axially into the cylinder comprising the electrode 5. Inaddition, the bores or openings l and lleform a .guiding means assuring that the connecting electrode I4 is properly-positioned during its raising and lowering movements insidethe tube I. If desired, the cylinder l may also be formed to slide along the inner surface of the tube I and to fit its bore rather snugly, so that it, too, aids in guiding the movement of the connecting electrode.

Fig. 3 shows a further embodiment of my invention inwhich thelightning arrester, indicated inits entirety by the reference character 30, has only a single dischargespace located inits lower portion. The lower'cap 3 and the cylindrical electrode 1 are similar to t-he elements 3 and l of the lightning arrester of Fig. 1, being integral and secured to the housing in a gas-tight manner for a purpose to be later apparent. The upper part of the lightning arrester 30 has a cap 31 in the. center of. which. is soldered or welded, or otherwise secured, the conductor 32.

The connecting electrode in the embodiment of Fig. 3 comprises a lower stub electrode 33 integral with a magnetizable metallic cylinder 34. The stub electrode 33 and the cylinder 3'4 compose the central connectingelectrode 35 which is normally maintained in a lowermost position by means of a spring 36. spring, the conductor 32 and the cylinder 34 may have small protuberances 3'! encircled by the extremities of the spring. A pigtail 38 shunts The circuit is completed by an arc across In order to position the.

.of the lightning arrester, the connecting electrode 35 is raised against the action of the spring 36 and the arc is extinguished between the electrode l and the stub electrode 33 as was described for the like operation of the arrester of 1. However, an extra space 4| between the top extremity of the electrode i and the bottom of the member 39, can be made as short or as long as found necessary so that the arc is first elongated before it is cutoff upon complete immersion of the stub electrode 33 in the bore 43.

In the lightning arrester of Fig. 4, indicated in its entirety by the numeral 53, the members of ceramic material shown in the prior figures for abruptly diminishing the arc thickness, have been eliminated, the arc extinction depending on the elongation of the space between a lower electrode 5i and a lower stub electrode 52 of "a center connecting electrode 53. In this arrester, an outside tube 54 of some suitable ceramic material, is provided with terminal electrodes including caps 55 and 53 and internal cylindrical electrodes 5| and 57, conductively connected to the respective caps. In this embodiment, the connecting electrode 53 is formed with a somewhat elongated central body portion 58 of ferrous material which is provided with ball bearings 59 and 65 at each end so that this body portion acts as a guide for positioning the entire electrode 53 during its movement within the tube 54.

a The body portions 58 is centrally bored and threaded from each end so that the lower stub electrode 52 may be secured therein and also-an upper stub electrode 6!. The lower fixed cylindrical electrode 51 and the stub electrode 52 are deliberately made relatively short compared to the fixed cylindrical electrodes 5! and stub electrode 3| in the upper part of the arrester, In order to insulate the central electrode 53 from the electrodes 5land 51 in theextreme positions of movement of the center electrode, thebody portion 58 is provided with insulating contact spacers or members 62 and 53'which are annular in shape and extend around the contiguous parts of the stub electrodes 52 and SI. The axial length of the portions of these spacers 62 and 63 which contact the cylindrical electrodes 5| and 51 is greater than the minimumdistance between the stub electrodes and the cylindrical electrodes so "that the arcs formed upon a discharge will flow to the stub electrodes rather than directly from one of the electrodes, say 5i, to the body portion 58. This construction is preferred so that the stub electrodes can be made, as in the other embodiments, of an arc-extinguishing metal.

.Much better results can be had if thearresters of the different. embodiments are filled with a gas at a sub-atmospheric pressure, and I have foundthat if the tube is filled with hydrogen at a pressure of mm., an arc length of 45 mm. is enough to cause an arc voltage drop of==800 volts. Thus, the elongation of the are alone can be. relied upon to clear'the protective circuit of Fig. 2. In order to exhaust the lightning arrester, one of the terminal conductors may be formed hollow, as shown in Fig. 4, and the corresponding cap also formed with a small aperture. After the arrester has been exhausted and filled with the desired gas at a suitable pressure, the conductor 10 may be pinched and welded into a unit mass, sealing the arrester tube. Some times soldering can be employed, in which case the hollow terminal conductor is tinned on the inside and then pinched and heat sealed. The method by which the arrester is assembled and filled with a gas is not part of this invention since many suitable processes or methods may be employed.

In the protective circuit, the resistor 2| of the protective circuit shown in Fig. 2 may be made of any suitable substance, but I have found it preferable to employ a block which limits the discharge current and also prevents the voltage across it from rising to too great a proportion of the voltage between the protected equipment l9 and ground, which would destroy the efficacy of the lightning arrester. Blocks of the character referred to are now well known to the art and usually comprise a mixture of silicon carbide, clay and lamp black, as more particularly disclosed in U. S. Patent No. 2,000,719 granted May '7, 1935, to J, Slepian et al.

While I have described my invention in different embodiments, many other equivalents are obvious to those skilled in the art and the teachings of my invention can be applied to arresters of equivalent designs,

I claim as my invention:

1. An over-voltage protective device comprising a hollow insulating tube, an electricity-conducting means secured gas-tight to one end of said tube, said means comprising a cylindrical electrode inside said tube near said end thereof,

an electricity-conducting (means secured gastight to the other end of said tube, said tube being filled with a gas at sub-atmospheric pressure, means within said tube for forming a discharge path between the first and second said means, the

last said means comprising a movable electrode axially disposed with respect to said cylindrical electrode, and spaced from its sides, means for moving said movable electrode out of said cylindrical electrode, and means for guiding said movable electrode during such movement.

2. An over-voltage protective device comprising a hollow, ceramic tube, an electricity-conducting means secured gas-tight to one end of said tube,

said means comprising a cylindrical electrode inside said tube near one end thereof, an electricity-conducting means secured gas-tight to the other end of said tube, the last said means comprising a cylindrical electrode inside said tube near said other end, said tube being filled with gas at sub-atmospheric pressure, said elechaving a magnetizable section and an electrode section normally in arcing relation to the said fixed electrode, said member being provided with an opening into which said electrode section may move, said opening closely fitting said electrode section, and means for moving said movable electrode upon breakdown of said device whereby said electrode section is moved into said opening.

4. An over-voltage protective device comprising a hollow ceramic tube, an insulating member within said tube intermediate its ends, an electricity-conducting means secured to said tube and comprising a fixed electrode within said tube at one side of said member, a movable electrode having a magnetizable section and an electrode section normally in arcing relation to the said fixed electrode, said member being provided with an opening into which said electrode section may move, said opening closely fitting said electrode section, means for moving said movable electrode upon breakdown of said device whereby said electrode section is moved into said opening, said fixed electrode and said electrode section being so dimensioned that upon movement of the movable electrode the space between its electrode section and the said fixed electrode is increased before the said electrode section moves into said opening.

5. The structure of claim 3 wherein said electrode section has a tip of a substance whose electrical conductivity, compared to the remainder of said electrode section, is relatively considerably less.

6. The structure of claim 4 wherein said electrode section has a tip of a substance whose electrical conductivity, compared to the remainder of the electrode section, is relatively considerably less.

7. The structure of claim 3 characterized by said tube being gas-tight and filled with gas at a sub-atmospheric pressure.

8. The structure of claim 4 characterized by said tube being gas-tight and filled with gas at a sub-atmospheric pressure.

9. The structure of claim 3 wherein said electrode section has a tip of a substance whose electrical conductivity, compared to the remainder of said electrode section, is considerably less, relatively, and said tube is gas-tight and filled with gas at a sub-atmospheric pressure.

10., An over-voltage protective device comprising a hollow insulating tube, an electricity-conducting means secured to one end of said tube, said means comprising a fixed electrode inside said tube near said end thereof, a second electricity-conducting means secured to the other end of said tube, the said second means comprising a fixed electrode inside said tube near said other end thereof, said electrodes being aligned and spaced from each other with an intermediate section of said tube between said electrodes, a movable connecting electrode within said tube, guiding means in said intermediate section, said connecting electrode being provided with tips extending away from each end of said guiding means and in arcing relation with said fixed electrodes.

11. The structure of claim 10 wherein one of said fixed electrodes and one of the co-operating tips of said connecting electrode are concentric but spaced, and of relatively extended length, and the other of said fixed electrodes and the other cooperating tip of said connecting electrode are concentric but spaced, and of relatively short length, and means for moving said connecting electrode wherebythe arcing relation between the first said one fixed electrode and one tip isnot substantially changed while that between the said second fixed electrode and second tipis' considerably changed.

12. An overevoltage protective. device comprising a hollow insulating tube, an electricity-conducting means secured to one end of. said tube, said means comprisingfla. fiXd electrode inside said tube, a second electricity-conducting means secured to the other end or said tube, the said second means comprising a fixed electrode inside said tube at said other end thereof, said fixed electrodes being aligned and spaced from each other with an intermediate section of said tube between aid electrodes, a movable connecting electrode. within said tube, guiding means in said intermediate section, said connecting electrode being provided with tips extending away from each end of said guidii: and in arcing relation with said fixed electrodes, said guiding means being aferrous c lindrlcal member fitting the hollow of said tube, and having bearing means at each. end for sliding in the hollow of said intermediate section.

13. An over-voltage protective device comprising a hollow'insulating tube provided with electricity-conducting means secured gas-tight at each end, said means at eachend including a hcllow cylindrical electrode fitting the inside of said tube, said electrodes being spaced, a movable connecting electrode within said tube Comprising a guiding portion, sliding inside said tube intermediate the ends of said electrodes, insulating spacers to insulate said guiding portion from said cylindrical electrodes, electrode stubs at each end of said guiding portion'and concentric with cylindrical electrodes but spaced therefrom, said connecting electrode in normal position having one stub substantially completely inserted in one l cylindrical electrode and the other stub almost withdrawn from the second cylindrical electrode, and means to move said connecting electrode, whereby the one stub is withdrawn from said one cylindrical electrode to increase the spacing between the two while the other is inserted in said second electrode.

14. The structure of claim 13 in which said spacers are fixed adjacent said electrodes and the said one stub is provided with an insulatingtip.

15. The structure of claim 13 in which said spacers are annular and fixed to the ends of said guiding portion, and said stubs are conductively secured to said guiding portion.

16. An electrical protective device comprising a container filled with a gas under sub-atmospheric pressure, a pair of separable electrodes in' said container, an insulatingrnember having an opening into which one of said electrodes may be rawn, means to separate said electrodes, said electrodes and member being so arranged that when the electrodes are first separated the common discharge path between them is large and after separation the common discharge 'path is confined within said opening.

17. In an electrical protective system, a protective device including a pair of separable electrodes, means for separating said electrodes to interrupt any are between them, a protective circuit including a resistanceto ground from said device, said electrodes being in series with said resistance, said resistance being of the type that can pass necessary amounts of current without ppreciable increase of voltage drop across it, said separating means being energized by a voltage drop across said resistance.

18. An over-voltage protective device comprising a hollow insulating tube, a fixed electrode in said tube, electrode means comprising a movable electrode in said tube, having an end normally in spaced arcing relation to said fixed electrode, an insulating member in said tube having an opening into which said end of said movable electrode can move, means for moving said movable electrode so that said end of said movable electrode moves away from said fixed eiectrode and into said opening for abruptly narrowing the arc path between the said end of said movable electrode and said fixed electrode to encourage extinction of the arc, said electrode means restoring said end of said movable electrode to its normal spaced arcing relation with respect to said fixed electrode upon extinction of the arc.

HANS VATIER.

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