US2673941A

US2673941A - Lightning arrester

Info

Publication number: US2673941A
Application number: US185083A
Authority: US
Inventors: Val Eugene J De
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1950-09-15
Filing date: 1950-09-15
Publication date: 1954-03-30
Anticipated expiration: 1971-03-30

Description

March 30, 1954 E. J. DE VAL LIGHTNING ARRESTER Filed Sept. 15. 1950 RI.. 0 Y 5% M m mJ n I m m u E I, I I I I I I I l/ II/ l Fig. I.

Patented Mar. 30, 1954 LIGHTNING ARRESTER Eugene J. De Val, Pitca inghouse Electric Co irn, Pa., assignor to Westrporation,

East Pittsburgh,

Pa., a corporation of Pennsylvania Application September 15, 1950, Serial No. 185,083

Claims.

The present invention relate to lightning arresters, and more particularly to the construction of lightning arresters of the expulsion type.

Expulsion lighting arresters consist of an expulsion element, or arrester element proper, mounted in an insulating housing, usually made of porcelain. The expulsion element comprises a tubular structure having an internal surface of insulating material which is capable of evolving substantially un-ionized gas when exposed to an electric arc, with electrodes at opposite ends of the tubular structure, at least one of the electrodes extending into the tube to provide an internal discharge path between the electrodes, and at least one end of the tubular structure being vented. In operation when an arc is established between the electrodes within the tubular structure, a large quantity of gas is evolved which is expelled in a blast through the vent, deionizing' the arc path and blowing out the arc gases to extinguish the arc.

In the conventional construction of lightning arresters of this type, the expulsion element has been mounted in the porcelain housing by means of threaded members which clamp the parts of the assembly tightly together and to the housing. This conventional construction, however, substantially stresses the expulsion element, which is undesirable because the expulsion element must withstand very high impact stresses when the arrester operates. If the expulsion element is pre-stressed by the mounting means, the maximum impact stresses which it can withstand during operation are correspondingly reduced, and the ability of the arrester to handle high surge currents and higher power currents is materially impaired. The conventional mounting means also causes substantial stresse in the porcelain housing, and this is also undesirable since the danger of breakage of the housing is increased. The conventional type of construction has the further disadvantage that it results in a permanent assembly which cannot readily b disassembled for inspection or replacement of the expulsion element.

The principal object of the present invention is to provide an expulsion lightning arrester assembly in which neither the expulsion element nor the insulating housing is substantially stressed, and in which the expulsion element can readily be removed for inspection or replacement, in the field, without disturbing the installation or the housing.

Another object of the invention is to provide an expulsion lightning arrester assembly in which the expulsion element is supported in the housing by resilient means engaging the lower part of the expulsion element, which permits simple and inexpensive parts to be used and which makes assembly and disassembly rapid and easy, so that the cost of the arrester is materially reduced, and the expulsion element can readily be removed for inspection or replacement.

A further object of the invention is to provide an expulsion lightning arrester assembly in which the top of the porcelain housing is closed by a simple, inexpensive cap member which i glazed, or otherwise integrally joined, to the housing, thus eliminating the large cap and cemented joint which have previously been necessary, facilitating the manufacture of the arrester and lowering the cost.

Still another object of the invention is to provide an expulsion lightning arrester assembly in which the series gap which is always used with an arrester of this type is enclosed in the housing, and in which one electrode of the series gap is mounted on an inexpensive cap member which fits into the top of the housing and is glazed or otherwise integrally joined to the housing, thus providing a simple and low cost construction.

The invention will be more fully understood from the following. detailed description, taken in connection with the accompanying drawing,

'in which:

Figure 1 is a vertical sectional view of a lightning arrester embodying the invention, and

Fig. 2 is a bottom plan view of the arrester.

The invention is shown in the drawing embodied in an expulsion-type lightning arrester which includes an expulsion element I mounted in-a housing 2 of porcelain or other suitable weather-resistant insulating material. The expulsion element l includes a tube or tubular structure 3 of hard fiber, or other suitable insulating material which is capable of evolving substantially non-ionized gas when exposed to the heat of an electric are. An upper electrode 4 extends into the upper end of the tube 3 and is shown as a steel sleeve which fits snugly in the tube and is threaded in the upper end of the tube, to securely join the electrode to the tube to hold, it against the axial thrust which occurs when the arrester operates. A stud 5 having a head 6 is threaded into the top of the electrode member s and extends above the upper end of the tube 3 to form one electrode of an enclosed series gap, as described hereinafter, An insu lating bushing T is placed over the stud 5 and a plurality of insulating washers 8 is placed between the top of th electrode i and the sleeve 1 to adjust the position of the head 6 of the stud in order to obtain the desired A lower electrode member 9 is disposed at the lower end of the tube 2. The electrode 9 is a gen erally cylindrical steel member with a large central bore 01' vent opening l8 and is threaded on the outside of the tube 3, or otherwise securely fastened to it. A plug or filler H of hard fiber, or other suitable insulating gas-evolving mate 10 rial, is disposed in the bore of the tube 3 between the electrodes 4 and 9 in order to restrict the arc path between the electrodes and to increase the area of gas-evolving material exposed to the arc. Any suitable type of filler may 1 be used, the particular filler shown being of the helically grooved type disclosed and claimed in my copending application, Serial No. 132.99 filed.

,September 2, 1950, and assigned to Westinghouse Electric Corporation. As more fully described in that application, the iiller i I has a helical groove l2 cut in it, extending from end to end of the filler, to cause a circumferential movement of the gas, in order to make wear of the filler and. tube more uniform and to elongate the arc to facilitate its interruption. The filler may be fixed in position but is preferably loose in the bore of the tube and rests on a steel support 3 which is clamped between the lower electrode 53 and the bottom of the tube 3 and which a plurality of peripheral vent holes is for the escape or gas from the interior of the tube.

A terminal member i5 is attached to the lower electrode 9. The terminal member be of any suitable type, and is shown as being a flat steel member having an extending and a vent opening H. The terminal i5 is attached to the bottom of the lower electrode 9 by welding. or in any other sui her, with the vent opening ll coina. the vent if! or the lower electrode. device of any suitable type is step e extending arm it for connecting a g l to the terminal member to, a slot or being formed in the housing oppos. minal device 58 to facilitate insertion of a 5! lead.

The housing 2 is a generally cylindrical. h llow porcelain housing adapted to receive protect the expulsion element l. The hr. has an internal shoulder 26 near its lower and a circumferential groove 2! at the bottom of the housing, providing another oppositely iacing internal shoulder at the bottom. A steel washer 2'2 is carried on the lower electrode a of the expulsion element 5, preferably resting on a shoulder on the electrode, and the washer 22 is adapted to engage the internal shoulder 2?! of the housing 2. a gasket 23 being interposed between the washer and the housing. The ex- 69 pulsion element I is supported in the housing by a resilient or spring member 24 which engages the lower electrode 53. The member as best seen in Fig. 2, is an elon ated spring member having a central opening 25, which is adapted to pass over a reduced lower part of the elec trode 9, so that the spring member en a es a shoulder on the electrode. The spring me er 24 may be punched from sheet steel, or other suitable spring material.

In assembling the arrester, the spring mernber 24 is passed over the terminal member iii, and the lower part of the electrode 9, so that its central part engages the shoulder on the electrode 9. The expulsion element l is inserted 7s of the porcelain housing 2.

of the arrester.

axially in the housing 2 with the washer 22 bearing against the shoulder 20 of the housing, and the ends of the spring member 24 are snapped into the groove 2|. The ends of the resilient member 24 thus engage the internal shoulder formed by the groove 2!, and the central part engages the lower electrode 9. Since the electrode carries the washer 22 which bears against the housing, the axial force applied to the electrode Q by the spring member 24 holds the washer tightly against the shoulder 20, and the expulsion element i is thus firmly and solidly held in position in the housing. It will be noted, however, that no substantial stresses are caused either in the expulsion element or in the housing by this mounting means for the expulsion element.

The top of the housing 2 may be closed in any suitable manner, but in the preferred embodiment shown in the drawing, the top is closed by a simple disc-shaped cap member 25 of porcelain. The top of the housing 2 is counterbored to provide an internal shoulder and the cap 25 fits into the annular recess thus formed and is glazed, or otherwise integrally joined, to the housing 2 as indicated at it. This provides a simple and low-cost construction, since the porcelain cap itself is inexpensive and can readily be put place in the housing before firing the housing. The glazed bond is then formed during the firing operation, which is necessary in the production Thus, a substantial simplification of manufacture, and a material re duction in cost are obtained, as compared to the conventional arrangement using a large cap member cemented to the housing after assembly The glazed loint also provi es a moistureproof joint which does not re uire the use of gaskets and which can readily be checked by visual inspection.

A spark is alwa s used with light- .esters of the expulsion t pe to isolate ter from the line under normal voltage so that the, fiber tube will not be ouslv subiectcd to the normal line voltage. orefered embodiment of the present in.-

as shown in the drawing, the series gap e -closed in the upper part of the housing 2.

previously indicated, the head 6 of the stud. forms one electrode of this gap. The other electrode is formed by the head 23 of a bolt 29 which extends through a central opening 30 in the porcelain cap 25, a gasket 3| being placed under the head of the bolt to seal the opening. Steel washers .2 may be placed on the bolt 29 on top of the cap 26 and the bolt is held in place by a nut A nut 34 and a clamping memberof any suitable type, are placed on the bolt 29 to clamp a line lead 36 to the bolt and an insulating cover member 3? is threaded o-n the upper end of the bolt to cover and protect the line lead and the end of the bolt, so that no live parts are exposed. It will be apparent that the head 28 of the bolt "29 and the head 6 of the stud 5 form a spark gap 38 between them which is in series with the expulsion gap between the electrodes i and B. The spacing of the gap 38 i accurately determined by utilizing the proper number of washers of proper thickness to locate the position of the head 6 of the stud 5 I .W' to the tube 3, so that the correct gap is easily obtained. A metal' nicer may be clamped under thehead ii of the stud to protect the top of the tube 3 and the inside surface of the housing. 2 from spa shield deposits of metal which may be emitted from the ap 38.

Inuse, the line lead 36 is connected to a line, or to a terminal of a protected device, such as a transformer, and the ground terminal I8 is connected to ground. When an overvoltage, such as a lightning surge, occurs, the gap 38 and the expulsion gap'b'etween 'the electrodes 4 and 9 are over in series to discharge the surge to ground. The are in the restricted internal path between the wall of the tube 3 and the filler ll causes the evolution of large quantities of substantially un-ionized gas, which deionizes the arc path and is expelled in a blast through the vent III to extinguish the arc, and thus interrupt the power current which tends to follow the surge. The helical grooved filler causes the gas to flow circumferentially within the tube, which has the effect of minimizing and making uniform wear or erosion of the tube and filler, and also elongates the arc by forcing it into the heli cal groove, thus facilitating interruption of the are, as more fully explained in my copending application mentioned above.

It will be seen that the construction disclosed provides resilient supporting means for holding the expulsion element tightly in position within the housing 2, but that the expulsion element is not substantially stressed, which was unavoidable with the types of clamping means previously used for mounting the expulsion element, although such stressing of the expulsion element is very undesirable, as it reduces the ability of the arrester to withstand the severe stresses which occur during a discharge. It will also be noted that no substantial stresses are imposed on the porcelain housing. The new construction also makes possible a material reduction in the cost of expulsion lightning arresters, since the mounting means for the expulsion element requires only simple, inexpensive parts. and the arrester can easily be assembled in the housing without the use of tools in a small fraction of the time required for previous constructions. This obviously results in a substantial reduction in cost. The new construction also has the important advantage that the expulsion element I can readily be removed from the housing in the field for inspection or for replacement, and this can be done very simply without the use of tools and without damaging either the expulsion element or the housing, or disturbing the mounting of the housing on its support. Thus, the new construction has numerous important advantages as compared to the conventional arrester constructions which have previously been used.

The glazed cap 26 also is an advantageous feature of the new arrester since it simplifies the manufacture of the housing and reduces its cost, as previously pointed out. The new cap also makes the arrester more compact by eliminating the large overhanging cap member previously used and the large cemented joint. The new cap member itself is also obviously cheaper than the large caps of relatively more com plicated shape previously used.

It should now be apparent that an expulsion lightning arrester construction has been provided which has many advantages. It will also be obvious that various changes and modifications may be made within the scope of the invention. Thus, the glazed cap is not essential to the use of the resilient mounting for the expulsion element, and any other suitable closure may be used for the top of the housing. Similarly, an external series gap may be used if desired instead of the internal gap shown. It is to be understood, therefore, that the inventionis not limited to the particular details of con-- l. A lightning arrester comprising a generally cylindrical insulating housing, an expulsion arrester element including a tubular structure having an internal surface of insulating material capable of evolving gas when exposed to an electric arc, and spaced electrode means at opposite ends of said tubular structure, at least one -of said electrode means extending into the tubular structure and the lower end of the tubular structure being vented, and resilient means in the housing at the lower end of said arrester element for supporting the arrester element in a vertical position in the housing, accessible through the lower end of the housing and readily removable therefrom.

2. A lightning arrester comprising a generally cylindrical insulating housing, an expulsion arrester element including a tubular structure having an internal surface of insulating material capable of evolving gas when exposed to an electric arc, and spaced electrode means at opposite ends of said tubular structure, at least one of said electrode means extending into the tubular structure and the lower end of ture being vented, and spring means engaging the housing and the lower end of said arrester element for supporting the arrester element in a vertical position in the housing, said spring means being accessible through the lower end of the housing and readily removable therefrom.

3. A lightning arrester comprising a generally cylindrical insulating housing, an expulsion arrester element including a tubular structure havthe tubular strucing an internal surface of insulating material capable of evolving gas when exposed to an electric arc, and spaced electrode means at opposite ends of said tubular structure, at least one of said electrode means extending into the tubular structure and the lower end of the tubular structure being vented, and a spring member supported in the lower end of the housing, said spring member engaging the lower end of said arrester element to support the arrester element in the housing, said spring member being accessible through the lower end of the housing and readily removable therefrom.

4. A lightning arrester comprising a generally cylindrical insulating housing, an expulsion arrester element including a tubular structure having an internal surface of insulating material capable of evolving gas when exposed to an electric arc, and spaced electrode means at opposite ends of said tubular structure, at least one of said electrode means extending into the tubular structure and the lower end of the tubular structure being vented, means on said arrester element bearing against a part of the housing near the lower end thereof, and spring means in the lower part of the housing engaging the arrester element for holding said bearing means against the housing to support the arrester element in the housing.

said resilient means being 5. A lightning arrester comprising a generally cylindrical insulating housing, an expulsion arrester element including a tubular structure having an internal surface of insulating material capable of evolving gas when exposed to an electric arc, and spaced electrode means at opposite ends of said tubular structure, at least one of said electrode means extending into the tubular structure and the lower end of the tubular structure being vented, means on said arrester element bearing against a part of the housing, and aresilient support member extending transversely of the lower part of the housing, the ends of said support member engaging in a groove in the housing and the center portion of the support member engaging the lower end of the arrester element for holding said bearing means against the housing to support the arrester element in the housing.

-' EUGENE J. DE VAL.

; References, Cited in the file of this patent UNITED STATES PATENTS I Number Number Name Date Jancke May. 2, 1939 Schoonenberg Aug. 29, 1939 Johnson Nov. '7, 1939 Kalb Jan. 14, 194'! DeLange a June 22,1948 Eldridge Nov. 25, 1952 FOREIGN PATENTS Country Date France Nov. 9, 1939 France Mar. 1, 1950