US2691742A

US2691742A - Lightning arrester

Info

Publication number: US2691742A
Application number: US243497A
Authority: US
Inventors: Val Eugene J De
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1951-08-24
Filing date: 1951-08-24
Publication date: 1954-10-12
Anticipated expiration: 1971-10-12

Description

INVENTOR ATTORI% E. J. DE VAL LIGHTNING ARRESTER Filed Aug. '24, 1951 Eugene J. De Vol m 2 //////////%///////////%w// w&

Oct. 12, 1954 Patented Oct. 12, 1954 LIGHTNING ARRESTER Eugene J. De Val, Pitcairn, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 24, 1951, Serial No. 243,497

6-Claims. 1

The present invention relates to lightning arresters and, more particularly, to a series spark gap construction for lightning arresters of the expulsion type.

Expulsion-type lightning arresters consist essentially of spaced electrodes disposed ina vented arcing chamber which is lined with, or contains, insulating material capable of evolving substantially un-ionized gas when exposed to an electric arc. When a discharge occurs between the electrodes, a large quantity of gas is evolved, which is discharged in a blast through the vent, blowing out the arc gases and deionizing the arc path to extinguish the arc, thus interrupting the power current which tends to flow through the arrester to ground following the discharge of a lightning surge. In the usual construction of arresters of this type, the arcing chamber consists of a tubular structure of hard fiber, or other suitable gas-evolving material, with electrodes disposed at the ends of the tube, at least one of the electrodes extending into the tube, and at least one of the electrodes being vented. A plug or'filler of gas-evolving material is usually placed in the tube between the electrodes to restrict the area of the arc path, and to increase the amount of gasevolving material exposed to the are, so as to improve the current-interrupting ability of the arrester.

A series spark gap device is always used with lightning arresters oi the expulsion type to isolate the arrester from the line under normal conditions, so that the fiber tube is not continuously subjected to the normal line voltage, which might cause harmful leakage currents over the surface of the tube. Open gaps have usually been used .for, this purpose, but open gaps are undesirable since they are subject to the risk of being bridged by birds, or by sleet or ice, and are also likely to have the gap setting accidentally changed in the course of handling and installing the arrester. Another objection to the use of open gaps is that one electrode is at line potential, and the other electrode at some potential intermediate between line and ground, and it is undesirable to have exposed live parts on a pole cross arm orother line structure. It has been proposed to completely enclose the series gap within the arrester housing, but this is also undesirable since such an enclosed gap is not accessible for inspection, or for checking the gap setting, and some provision must be made for venting the gap, which presents a rather diilicult problem.

The principal object of the present invention is to provide an expulsion-type lightning arrester having a series spark gap device which is willciently enclosed to prevent accidental bridging of the gap, or accidental contact with it, but which is accessible for inspection and for checking the gap setting.

Another object of the invention is to provide a semi-enclosed spark gap device for expulsion lightning arresters in which the gap is contained in a rigid, low-cost insulating housing which permits the gap spacing to be accurately set in the manufacture of the gap, and which suiiiciently encloses the gap to prevent accidental bridging or contact with the gap but permits access to the gap for inspection.

A further object of the invention isto provide a simple and low-cost semi-enclosed series gap device for expulsion lightning arresters which can readily be mounted on the main arrester housing to close the housing and eliminate the usual large cemented cap which has been used heretofore, thusreducing the cost and improving the appearance of the arrester.

Other objects and advantages of the invention will be apparent from the following detailed description, taken in connection with the accompanying drawing, in which:

Figure 1 is a vertical sectional View of a lightning arres'ter embodying thespark gap device of the present invention, and

Fig. 2 is a view in elevation of the spark gap device.

The new spark gap device may be used with expulsion-type lightning arresters of any suitable or usual construction. The gap device is shown in the drawing, for the purpose of illustration, embodied in a lightning arrester having a tube or tubular structure l, which forms the arcing chamber of the arrester, and which is made of hard fiber, or other suitable insulating material which is capable of evolving substantially unionized gas when exposed to an electric are. An upper electrode member 2 is disposed in the upper end of the tube l. The electrode 2 is shown as a steel sleeve which fits tightly in the tube l, and which is threaded in the upper end of the tube to hold the electrode securely in position against the strong axial thrust which occurs when the arrester operates. A lower electrode memher 3 provided at the lower end of the tube The lower electrode 3 is shown as a generally cylindrical steel member which fits against the lower end of the tube 1, and which is provided with a, plurality of vent openings 4 for discharge of the gas generated in the arrester during operation.

A steel sleeve 5 fits tightly over the outside of the tube I, to provide mechanical reinforcement against the high bursting stresses which occur during operation, and to function as an electrostatic shield to improve the sparkover characteristics of the arrester. The shield is held in position by annular indentations or crimps 6 which engage corresponding annular depressions on the tube I to prevent relative axial movement between the tube and the shield. The lower electrode 3 is provided with an annular recess or groove 1, and the shield 5 extends over the electrode 3, and its lower end is crimped or rolled into the recess 7, as indicated at 8, toretain-the electrode 3 in position and to effect electrical contact to the lower electrode.

A generally cylindrical plug or filler '9 of insulating, gas-evolving material, such as hard fiber,

is preferably inserted in the bore of the tube I between the electrodes 2 and 3 to restrict the arc path. Any suitable type of filler may be used, but it is preferred to utilize the type of filler disclosed and claimed in my copending application Serial No. 182,994, filed September 2, 1950, and assigned to Westinghouse Electric Corporation. As more fully explained in that application, the

filler 9 is generally cylindrical and has a helical groove ID in its surface extending from end to end of the filler. When the arrester operates,

the gas evolved from the tube and filler flows through the groove and forces the are into a helical path, elongating the arc and increasing The washer I2 also engages an internal shoulder in the housing II, a gasket I3 being interposed between the washer and the housing, and the washer I2 is clamped against the housing as described hereinafter. The washer I2 has an extendinglug I4 at one side which carries a terminal device I5, of any suitable type, forconnecting a ground lead to the lower electrode 3. The lug I4 is bent downwardly, as shown, so that the terminal device I5 is substantially enclosed within the lower end of the housing II,

and an opening or recess I3 is provided in the housing to permit access to the terminal device I5.

The series spark gap device, which normally isolates the arrester from the line voltage, is

contained in a gap housing I1 which is adapted to be mounted on top of the housing II to close the upper end of the housing. The gap housing I I has a lower housing member I8, which is generally conical in shape, as shown in the drawing, and which has a central opening I9. The gap housing I! also has an upper housing member 20, which is generally cup-shaped, and which has relatively large openings 2| in its opposite sides extending to the lower edge of the housing member 20, as clearly shown in Figure 2. The upper housing member 20 also has a central opening 22 at the top. The housing members I8 and 20 are preferably made of porcelain although other rigid insulating material might, be'used.

The upperhousing member 20 adaptedto rest trode member and the housing. A nut 21 on the' stud 24 clamps the electrode 25 to the housing member I8 and secures it firmly in position.

The upper electrode of the series spark gap is provided by a stud 28 which extends through the central opening 22 of the upper housing mem- -ber- 20; The stud 28 is accurately positioned, to

determine the gap spacing, by means of a generally U-shaped retaining member 29 which engages in a slot in one side of the stud 28 and seats in a recess'in the housing member. 20." A nut 30 is threaded on the stud 28 to. clamp the stud in place; A terminal clamp 3| of any suitable type may be provided on the stud above the nut 30 to provide for clamping a linelead to the stud 28. It will be seen that the sparkigap between the

electrodes

25 and 28 is enclosed within the housing I1, but that the gap is-accessible for inspection and checking through the openings 2 I.

The gap housing I! is adapted to be mounted on the main arrester housing II and to close the top of the housing, thus replacing the conventional large porcelain cap which hasbeenutilized heretofore. The gap housing I! may be mounted on and secured to the arresterhousing I I in-any suitable or desired manner. In the preferred embodiment shown in the drawing, thegap housing is mounted in place in a very simple manner by threading the lower end of the stud 24 into a tapped hole in the upper end of the electrode 2. A gasket 32 is interposed between the bottom of the gap housing I! and the top of the arrester housing II, to seal the interior of the arrester housing. It will be seen that when the stud 24 is threaded into the electrode -2 and tightened, the gap housing I! will be firmly-seelectrode 25 is directly connected electrically to electrode 2. The stud 24 draws the expulsion tube I upward and thus clamps the washer I2 against the housing II so that the entire assembly is tightly clamped together.

It should now be apparent that a semienclosed spark gap device has beenprovided for expulsion lightning arresters which avoids the difficulties and objectionable features of the gap devices which have been used heretofore. Thus, the gap housing I! completely encloses the series spark gap except for the openings 2I, so that the gap is sufficiently enclosed to prevent accidental bridging and to prevent any accidental contact with the gap electrodes. The gap is accessible, however, through the openings 2I for visual inspection, and for checking the accuracy of the gap setting, thus avoiding the disadvantages of a completely enclosed gap. The gap electrodes are directly supported on rigid insulating material so that their position, and therefore the gap spacing, can accurately, be predetermined and the desired setting easily attained in the manufacture of the gap, and thereafter rigidly maintained. The conical shapeof the lower gap housing member I8 permits .rain

water which may enter the housing to immediately drain out through the openings 2|, which extend to the lower edge of the housing member 20, so that there is no danger of the gap being bridged in this manner. The gap housing itself is relatively simple and inexpensive to manufacture since it consists merely of two pieces of porcelain which can readily be molded to the desired size and shape and glazed together. The use of this gap housing mounted directly on the top of the main arrester housing eliminates the need for the large porcelain cap cemented to the arrester housing which has usually been necessary heretofore, and thus materially reduces the cost of the arrester as well as improving its appearance.

A particular embodiment of the invention has been shown and described for the purpose of illustration, but it will be apparent that various other embodiments and modifications are possible within the scope of the invention, and it is to be understood, therefore, that the invention is not limited to the specific details of construction shown and described, but in its broadest aspects, it includes all equivalent embodiments and modifications which come within the scope of the appended claims.

I claim as my invention:

1. A lightning arrester comprising an insulating housing, a tubular structure within the housing having an internal surface of insulating material capable of evolving gas when exposed to an electric arc, electrode means disposed at the ends of said tubular structure, at least one of said electrode means extending into the tubular structure and at least one end of the tubular structure being vented, a gap housing of insulating material mounted on the first-mentioned housing, said gap housing having at least one opening therein and being otherwise completely closed, a pair of spaced electrodes supported in the gap housing and disposed to form a spark gap between them adjacent said opening, and means for electrically connecting one of said pair of electrodes to one of the first-mentioned electrode means.

2. A lightning arrester comprising an insulating housing, a tubular structure within the housing having an internal surface of insulating material capable of evolving gas when exposed to an electric arc, electrode means disposed at the ends of said tubular structure, at least one of said electrode means extending into the tubular structure and at least one end of the tubular structure being vented, a gap housing of insulating material mounted on and closing the first-mentioned housing, said gap housing having large openings in the sides thereof and being otherwise completely closed, a pair of spaced electrodes supported in the gap housing and forming a spark gap theerin adjacent said openings, and means for electrically connecting one of said pair of electrodes to one of the first-mentioned electrode means.

3. A lightning arrester comprising an insulating housing, a tubular structure within the housing having an internal surface of insulating material capable of evolving gas when exposed to an electric arc, electrode means disposed at the ends of said tubular structure, at least one of said electrode means extending into the tubular structure and at least one end of the tubular structure being vented, a gap housing having a lower part adapted to fit on and close the top of the first-mentioned housing, said gap housing having large openings in the sides thereof and being otherwise completely closed, a pair of spaced electrodes supported in the gap housing and forming a spark gap adjacent said openings, and means extending through the lower part of the gap housing for securing the gap housing in place on the first-mentioned housing and for electrically connecting one of said pair of electrodes to one of the first-mentioned electrode means.

4. A semi-enclosed spark gap device comprising a gap housing of insulating material, said gap housing having at least one relatively large opening in the side thereof, a lower electrode member supported in the lower part of the gap housing, and an upper electrode member supported in the upper part of the gap housing, said electrode members extending into the gap housing and being spaced apart to form a spark gap therebetween adjacent said opening.

5. A semi-enclosed spark gap device comprising a lower housing member of insulating material, an upper housing member of insulating material, said housing members being permanently joined together to form a closed housing, the upper housing member having relatively large openings on opposite sides thereof, a lower electrode member supported in the lower housing member, and an upper electrode member supported in the upper housing member, said electrode members extending into the housing and. being spaced apart to form a spark gap therebetween adjacent said openings.

6. A semi-enclosed spark gap device comprising a generally conical lower housing member of insulating material, a generally cup-shaped upper housing member of insulating material, said upper housing member having relatively large openings on opposite sides thereof extending to the lower edge of the housing member, the upper housing member resting on the lower housing member and being permanently joined thereto to form a closed housing, a lower electrode member supported in the lower housing member, and an upper electrode member supported in the upper housing member, said electrode members extending into the housing and being spaced apart to form a spark gap therebetween adjacent said openings.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,338,479 Ackermann Jan. 4, 1944 2,372,035 Wade Mar. 20, 1945 2,391,758 Wade et a1. Dec. 25, 1945 2,414,308 Kalb Jan. 14, 1947 2,440,484 Pittman Apr. 27, 1948