US3218517A

US3218517A - Combined lightning arrester and fuse cutout

Info

Publication number: US3218517A
Application number: US223697A
Authority: US
Inventors: Edward L Sankey
Original assignee: McGraw Edison Co
Current assignee: McGraw Edison Co
Priority date: 1962-09-14
Filing date: 1962-09-14
Publication date: 1965-11-16
Anticipated expiration: 1982-11-16

Description

E. L. SANKEY COMBINED LIGHTNING ARRESTER AND FUSE CUTOUT 3 SheetsSheet l INVENTOR.

Edward L 56277 fitter/7y Nov. 16, 1965 Filed Sept. 14, 1962 Nov. 16, 1965 E. L. SANKEY COMBINED LIGHTNING ARRESTER AND FUSE CUTOUT 3 Sheets-Sheet 2 Filed Sept. 14, 1962 INVENTOR. Edward L. San/ 25y BY 1 Nov. 16, 1965 E. L. SANKEY 3,218,517

COMBINED LIGHTNING ARRESTER AND FUSE CUTOUT Filed Sept. 14, 1962 3 Sheets-Sheet 5 INVENTOR. Ida/am L. San/K BY flaw M United States Patent M 3,218,517 COMBINED LIGHTNING ARRESTER AND FUSE CUTOUT Edward L. Sankey, Oak Creek, Wis., assignor to McGraw- Edison Company, Milwaukee, Wis., a corporation of Delaware Filed Sept. 14, 1962, Ser. No. 223,697 14 Claims. (Cl. 317-66) This invention relates to protective devices for electrical apparatus and in particular to a combined lighting arrester and fuse cutout construction.

Distribution transformers are conventionally protected by a fuse for clearing transformer faults and a lightning arrester for by-passing impulse voltages on the line to ground. Usually both a fuse cutout and a lightning arrester are mounted on a pole or a crossarm, or one of the protective devices may be mounted directly on the transformer. In all of these mounting arrangements only limited space is available for supporting the protective devices.

Combination lightning arrester and fuse assemblies are known, but heretofore they either have been impracticable or commercially unsuccessful. For example, one known arrester and fuse assembly utilizes an open link fuse cutout Whose interrupting rating is too low for use on most distribution systems. Further, in this known fuse and arrester combination the arrester is almost twice as long as the fuse. thus necessitating that the ground terminal be at the lower end of the insulating member and that the assembly be mounted at such lower end. The use of an expulsion fuseholder mounted between the upper terminal and an intermediate terminal is impracticable with such arrangement since manual operation of the fuseholder, which normally is closed by a lineman with considerable speed and force, would impose high cantilever stress on the base mounting. Further, the recoil forces resulting from operation of an expulsion fuse tube would be transmitted to the base mounting bracket through the relatively weak tubular portion of the porcelain housing. Still further, the known arrester and fuse combinations are not bird-proof and have no means to isolate the arrester and prevent fiow of follow current through the arrester in the event of damage to the arrester.

It is an object of the invention to provide a combined lightning arrester and fuse tube cutout which saves mounting space on the pole or crossarm in comparison to separate cutout and arrester; which is less expensive to install than sepa-rate cutout and arrester; which has higher interrupting capacity than known arrester and fuse combinations that utilize an open link fuse cutout; which is bird-proof and animal-proof and thus assures continuity of service to customers and eliminates false outages; which transmits recoil forces, incident to operation of the fuse tube cutout, to the mounting bracket through a high strength portion of the porcelain insulator which may be solid in cross section rather than through a weak tubular portion of the porcelain as in prior art devices; which avoids the high cantilever forces which were applied to the base mounting of prior art apparatus when the cutout was manually closed; and which has means to isolate the lightning arrester, and thus prevent flow of follow current therethrough, in the event of damage to the lightning arrester.

A further object of one embodiment of the invention is to provide a combined lightning arrester and fuse tube cutout which positively isolates the lightning arrester in the event of damage to the arrester and also gives a visible indication of arrester damage, thus positively preventing line lockout and customer outages.

These and other objects and advantages of the inven- 3,218,517 patented Nov. 16, 1965 ice tion will be more readily apparent from the following detailed description when taken in conjunction with the accompanying drawing wherein:

FIG. 1 is an elevational view of a preferred embodiment of the invention mounted on a crossarm;

FIG. 2 is a partial vertical section view through the embodiment of FIG. 1 and FIG. 3 is a view similar to FIG. 2 through an alternative embodiment of the invention.

Referring to FIG. 1 of the drawing, the combined lightning arrester and fuse cutout includes an elongated member of insulating material, preferably high strength, wet-process porcelain, having a metallic mounting hanger 11 affixed thereto intermediate its ends. The metallic mounting hanger 11 is adapted to be connected to ground over a ground wire 12 secured to a terminal 14 mounted on hanger 11. The metallic hanger 11 is illustrated as secured to a bracket 15 afiixed to a pole crossarm 16 so as to permit swivelling the hanger 11 and insulating member 19 to any desired angle relative to the cross arm 16 and locking such position, but it will be appreciated that the hanger 11 alternatively permits mounting directly on a pole, on a transformer casing, or a steel structure as desired.

The portion 17 of the porcelain insulating member 11) above the hanger 11 is tubular (see FIG. 2) and houses the lightning arrester assembly 18 including valve material 19 and spark gap means 20. The valve material 19 preferably comprises a plurality of superimposed valve blocks 21 each of which has a suitable negative resistance granular material such as silicon carbide molded with an inorganic binder such as sodium silicate. However, it will be appreciated that the valve material may, if desired, be molded directly within the tubular portion 17 of the porcelain insualting member 10. The spark gap assembly is preferably of the type disclosed in US. Patent 2,891,193 to F. V. Cunningham, having the same assignee as the present application, and includes late-rally spaced support members 23 preferably of ceramic insulating material having slots 24 at vertically spaced apart intervals on opposed sides of each support member 23 which receive conductive baffle plates 25. The battle plates 25 are notched at opposed sides to provide shoulder portions (not shown) engageable with the slots 24 of the support members 23. Each baffle plate 25 has a central aperture in which an electrode member 26 is seated and protrudes from both sides thereof. The upper portion of the spark gap assembly 20 is held together by means of a transverse retainer plate 27 having downwardly formed ears 28 embracing the sides of the opposed support members 23. A depending upper electrode 29 may be formed in the central portion of the retainer plate 27. The bottom valve block 21 may rest upon a cup-shaped metallic disk 30 spot-welded to the retainer plate 27. An annular insulating member 31 of flexible material such as rubber and of larger diameter than the retainer plate 27 and disk 30 may be clamped between these members and hold the upper end of the spark gap assembly 20 centrally of the tubular portion 17 as disclosed and claimed in the copending application of Stanley S. Kershaw, Serial No. 82,517, filed January 13, 1961, now Patent Number 3,184,634, and having the same assignee as this application. The insulating member 31 is in sealing relation with the internal wall of tubular portion 17 to prevent ionized gases formed in the spark gap means 20 from drifting in between the valve blocks 21 and the tubular portion 17 where they could form a conductive path around the valve blocks 21. The member 31 also prevents moisture given off by the valve blocks 21 during arrester operation from entering the 3 area of the spark gap means where it could lower the power frequency sparkover of the spark gap means 20.

The lower end of the opposed support members 23 are urged together by upwardly extending ears 32 on the lower electrode plate 33 which is spot welded to a circular metallic member 34 of inverted cup-shape. A lower gap electrode 35 has a depending tubular portion 36 of reduced diameter extending through clearance apertures in lower electrode plate 33 and cup-shape member 34. The tubular portion 36 is spun over to aflix electrode 35 to lower electrode plate 33 and to also retain an outwardly biased leaf spring 37 which urges the support members 23 outwardly against the upwardly bent ears 32 on the lower electrode plate 33 to provide a frictionally held assembly. The inverted cup-shaped member 34 of the spark gap assembly 20 is supported upon a metallic disk 38 which rests upon an annular bone-fibre cushion 39 at the bottom of the axial bore in insulating member 10.

The hanger strap 11 extends into a transverse slot 40 in insulating member 10 and is fastened therein by suitable cement 41. A knurled metallic member 44 has a drive fit within an aperture in hanger 11 and also has a tapped axial hole 45 in the upper face thereof. A flat head screw 47 extends through a clearance aperture in disk 38 and through an axial bore 48 of reduced diameter in insulating member 10 at the bottom of tubular portion 17 and is threaded within tapped hole 45 to provide electrical connection between the bottom electrode of the spark gap assembly and hanger strap 11. A gasket 49 of flexible material compressed between member 54 and the upper surface of transverse slot 40 hermetically seals the lower end of tubular portion 17.

A metallic sealing cap 50 is spun over a circumferential flange 51 at the upper end of insulating member 10 to close the open end of tubular portion 17. A gasket 52 of flexible material compressed between the open end of insulating member 10 and cap 50 hermetically seals the upper end of tubular portion 17. Insulating means 53 such as a sprayed coating of a suitable epoxy resin or an annular rubber sleeve of generally U-shaped cross section may cover the side and top surfaces of sealing cap 50. A stainless steel coil spring 54 compressed between sealing cap 50 and the upper valve block 21 retains the lightning arrester components in position within tubular portion 17. Copper straps 55 interconnecting the upper and lower turns of spring 54 shunt the inductance of the spring and provide positive electrical connection between the cap 50 and the uppermost valve block 21. The head of a threaded stud 57 passing through an axial aperture in cap 50 is brazed to cap 50. Stud 57 forms the upper terminal for the lightning arrester, and a flexible metallic connecting strap 58 is aflixed to stud 57 by a nut 59.

Insulating member 10 at its lower end carries a bottom contact and terminal assembly 61 (hereinafter referred to as the bottom contact) provided with an eyebolt connector 62 which constitutes the load terminal for the combined fuse and arrester and is adapted to be connected to a lead 63 from the load. Insulating member also carries between the metallic hanger 11 and the upper terminal 57 an intermediate contact and terminal assembly 65 (hereinafter referred to as the intermediate contact). An expulsion fuseholder 66 is pivotally mounted on the bottom contact 61 for swinging movement relative to the intermediate contact 65 and is latched to the intermediate contact 65. Fuseholder 66 includes an expulsion fuse tube 68 surrounding a fuse link 69. The upper end of fuse tube 68 is aflixed within a tubular, metallic, fuseholder upper contact 70 which is open and threaded at its upper end. A button cap 72 (see FIG. 2) on the end of fuse link 69 is disposed against the open end of upper fuse holder contact 70 and is held in place by an expendable cap 73 threaded onto the end of upper fuseholder contact 70 and having a frangible section adapted to rupture as the result of excessive pressure generated within fuse tube 63 when fuse link 69 operates. A hook- Cir stick receiving eye 75 integral with the upper fuseholder contact 70 permits pivoting the fuseholder 66 on the bottom contact 61 and removing the fuseholder 66 from the insulating member 10. A laterally extending metallic contact rod 76 is also integral with the upper fuseholder contact 70.

The intermediate contact 65 includes a stationary contact supporting hood 77 clamped to insulating member 10 by a U-bolt 79 and a spring 80 provided with a shouldered portion 81 behind which the contact rod 76 on the upper fuseholder contact 70 is positioned to detachably lock the upper end of the fuseholder 66 in position. U- bolt 79 is covered by insulating means 83 such as a coating of epoxy resin or a sleeve of insulating material. Spring 80 is constructed from a long rod bent symmetrically about its midpoint to have an approximate U-shape with two legs 84 which are bent to form loops 85, and the free ends of the spring 80 are inserted through apertures (not shown) in hood 77. The legs 84 of the spring 80 are kinked laterally in opposite directions to define a widened mouth (not shown) having converging sides which function to align the upper end of fuseholder 66 as it is swung to closed position by a hookstick engaging the eye 75. Hood 77 carries an eyebolt connector 86 which constitutes the line terminal for the combined fuse and arrester and is adapted to be connected to a power line conductor 87.

A split-sleeve 83 clamped to the lower end of dropout fuse tube 68 has radial extending arms 89 secured by means such as rivets to a U-shaped support member 90 embracing the arms 89 and having a hookstick receiving eye 92 for removing and re-positioning the fuse holder in the usual manner. A fuse link extracting lever, or flipout lever, 93 is pivoted by a pin 94 to the support member 90. The fuse link extracting lever 93 is provided with trunnions 96 and also with a threaded member 97 for clamping the lower end of the flexible fuse link 69 to the extracting lever 93.

The bottom contact 61 includes a metallic member 98 fastened to the lower end of insulating member 10 by a U-bolt 99. Member 98 is provided with a pair of arms 100 having hook-like portions 102 which receive the trunnions 96. The diameter of the trunnions 96 is greater than the spacing between the arms 100 and the end of the hook-like portions 102, and the trunnions 96 are approximately semicircular, i.e., flat on one side, to permit insertion and removal of the trunnions 96 within the hooklike portions 102 from one direction only and to prevent removal thereof until the fuse tube 68 is pivoted approximately 180 degrees from its normally latched position shown in the drawing. Consequently, the recoil forces resulting from operation of fuse link 69 and expulsion of gases from fuse tube 68 will be transmitted directly to hanger 11 through the directly-engaged trunnions 96 and hook-like portions 102.

The fuse link extracting lever 93 is normally held from pivoting by the tensioned fuse link 69. A metallic terminal mounting strap 105 aflixed to lower contact member 98 carries the eyebolt connector 62 which is connected to the wire 63 leading to the load.

Means including a pair of spaced apart electrodes are connected between the intermediate contact 65 and the upper terminal 57 for providing a path to ground through the lightning arrester assembly 18 and hanger 11 for impulse and surge voltages appearing on power line 87 and for preventing continued flow of follow current through the lightning arrester assembly 18 in the event of damage to the lightning arrestor assembly. In the preferred embodiment shown in FIGS. 1 and 2 such means constitute the spaced apart upper and

lower electrodes

113 and 114, respectively, of an isolator 115 of the type disclosed in US. 2,860,210 to Stoelting et a1. having the same assignce as this application. The spaced apart

electrodes

113 and 114 are enclosed in a breakable weatherproof housing 116, and an explosive shell 117 disposed in the bore of the pper electrode 113 is arranged to explode and break the housing 116 in the event of excessive flow of follow current between

electrodes

113 and 114. Isolator 115 is carried between a rigid, laterally extendin arm 118 on the body portion of the eyebolt connector 86 for the power line conductor 87 and the flexible connecting strap 58 of the upper terminal 57. Surge voltages normally break down the air gap between

electrodes

113 and 114, the surge voltage and follow current flow across such air gap without exploding the shell 117, and the follow current is limited by the valve material 19 and interrupted by the spark gap means of the lightning arrester 18. In the event of damage to the lightning arrester 18 from an extreme lightning stroke or other causes, the arrestor acts as a short circuit and follow current continues to flow through the arrester 18 until the heat generated thereby explodes the shell 117 and separates the

electrodes

113 and 114 to electrically disconnect the lightning arrester 18 from the power line wire 87.

Means are provided in the preferred embodiment of FIGS. 1 and 2 to increase the stray capacitance of the baffle plate electrodes of the spark gap means 20 to ground and thus render the voltage distribution across the spark gap means more uniform and stabilize the sparkover potential of the spark gap means. The spark gap means 20 should not be positioned at the upper end of tubular portion 17 since with such arrangement the full line-to-ground potential would be impressed across the tubular porcelain wall and a high level of corona could result. The stray capacitance of the intermediate contact 65, including hood 77 which is at power line potential, to the baffle plate electrodes 25 increases the leakage current between bafiie plate electrodes and accentuates the non-uniformity of the potential distribution across the spark gap means. A U-shaped, silicon bronze grading strap 130 is provided at the lower end of spark gap means 20 to increase the stray capacitance between the baffle plate electrodes 25 and the grounded hanger 11. Such increase in stray capacitance to grounded hanger 11 increases the leakage current between electrodes 25, makes the potential distribution across the spark gap means 20 more uniform, and stabilizes the flashover potential of the spark gap means 20. The cross-piece of the U-shaped strap 130 is positioned between the inverted cup-shaped member 34 and the metal disk 38. The upwardly extending arms 131 of strap 130 are disposed between the spark gap means 20 and the inner surface of tubular portion 17. The ends of the upwardly extending arms 131 are covered with insulation 132 to reduce corona between the intermediate contact 65, which is at the potential of the power line 87, and the arms 131 of the grading strap 130 which are at ground potential.

The

electrodes

113 and 114 of the isolator 115 may be bridged by means such as an annular resistor 133 of negative resistance material for preventing accumulation of charge on the upper electrode 113, thereby eliminating radio interference which might result from such accumulation of charge. The annular resistor 133 is disposed against the upper electrode 113 and is electrically connected to the lower electrode 114 by means of a metallic spring spider 134.

In the embodiment of FIG. 3, the means for providing a path to ground through the lightning arrester 18 and for preventing continued flow of follow current through the arrester in the event of damage to the arrester comprises fixed spark gap means defined by an upwardly extending electrode 120 integral with the eyebolt connector 86 for the power line conductor 87 and an L-shaped strap electrode 58' mounted on stud 57 of the upper terminal so as to be spaced from electrode 120 and define a fixed air gap therebetween. In the event of damage to the lightning arrestor of this embodiment, the spark gap between electrodes 58' and 120 will continue to flash over as a result of lightning striking the power line, and follow current will continue to flow to ground through the damaged 6 lightning arrester until a back-up device such as recloser in the power line 87 interrupts the flow of current in the power line. When power is restored to the line 87, the spark gap between electrodes 58' and will isolate the lightning arrester 18 from the power line and prevent the flow of sixty-cycle current through the damaged arrester.

The spark gap 20 means of the embodiment of FIG. 3

has an annular ceramic spacer 122 of resistance material disposed in each spark gap between an upper cup-shaped electrode 123 and a similar lower electrode 124 of inverted cup-shape. The resistance spacers 122 form a voltage divider which maintains uniform voltage distribution across the spark gaps of the arrester. The bottom contact 61, the intermediate contact 65 including hood 77 and spring 80, the fuse tube 68 as well as the electrodes such as 58' and 120 defining the spark gap external to the lightning arrester are disposed on a side of the insulating member 10 diametrically opposed to the side from which the metallic hanger 11 protrudes. Since cap 50 and U-bolt 79 are covered with insulating

material

53 and 83 respectively, no electrically energized metallic parts are exposed on the side of the insulating member 10 from which the grounded hanger 11 protrudes. Consequently, birds or animals sitting on the grounded hanger 11 do not have ready access to metal parts at the potential of the line. Similarly, a bird or animal sitting on the bottom or

intermediate contact

61 or 65 cannot easily contact a grounded metallic part since it would have to reach around to the opposite side of the insulating member 10 in order to do so. Consequently, continuity of customer service is assured and false outages, which could result from animals short circuiting between metallic parts at different electric potentials, are prevented.

It will also be appreciated that the disclosed combined arrester and fuse cutout saves considerable mounting space on the pole, crossarm or transformer casing and also provides considerable saving in the installation expense in comparison to separate arrester and fuse cutout.

The recoil forces resulting from operation of fuse link 69 and expulsion of gases from fuse tube 68 are transmitted to the hanger 11 through a high strength portion of insulating member 10 between hanger 11 and bottom contact 61 which may be solid in cross section and thus considerably stronger than the tubular porcelain members of prior art devices. In the production model a small diameter axial bore is provided in the lower portion of insulating member 10 between hanger 11 and the bottom surface thereof to facilitate molding the porcelain, but this lower diameter portion is of substantially greater strength than the tubular upper portion 17. High cantilever forces, which were applied to the base mounting of prior art combined arrester and cutouts when the fuse cutout was closed, are eliminated with the disclosed construction.

The combined fuse tube cutout and arrester has higher interrupting capacity than prior art devices utilizing open fuse links, for example, its interrupting rating is 10,000 R.M.S. asymmetrical amperes. The combined cutout and arrester provides complete cutout and lightning arrester protection on transformers, capacitor racks and banks, at sectiona lizing points, or at small substations and switchmg stations.

While only a few embodiments of the invention have been illustrated and described, many modifications and variations thereof Will be apparent to those skilled in the art, and consequently, it is intended to cover in the appended claims all such modifications and variations which fall within the true spirit and scope of the invention.

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

1. A combined fuse cutuout and lightning arrester comprising, in combination, elongated insulating means having an upper terminal, a bottom contact, and a contact intermediate said upper terminal and said bottom 4 contact adapted to be connected to a power line, a fuseholder pivotally mounted on said bottom contact and latched in contact with said intermediate contact, a metallic mounting member affixed to said insulating means between said intermediate and bottom contacts and adapted to be connected to ground, the upper portion of said insulating means being hollow, a lightning arrestor assembly within said hollow upper portion of said insulating means including spark gap means and valve material connected in series relation between said upper terminal and said metallic mounting member, and means including a pair of spaced apart electrodes exterior of said insulating means one of which is connected to said upper terminal and the other of which is connected to said intermediate contact for providing a path through said lightning arrester assembly to ground for impulse voltages on said line and for isolating said arrester assembly from said line and from said intermediate contact to prevent the fiow of follow current through said arrester assembly in the event of damage to said arrester assembly.

2. In the combination defined in claim 1 wherein said spaced apart electrodes define a fixed spark gap which isolates said lightning arrester assembly in the event of damage to said arrester assembly after a back-up device opens said power line and interrupts the flow of follow current through said damaged arrester assembly.

3. In the combination defined by claim 1 wherein an explosive charge is arranged to separate said electrodes in the event of excessive flow of current between said electrodes.

4. A combined fuse cutout and lightning arrester comprising, in combination, elongated insulating means having an upper terminal, a bottom contact adapted to be connected to the load, and a contact intermediate said upper terminal and said bottom contact adapted to be connected to a line; an expulsion fuseholder pivotally mounted on said bottom contact and latched in contact with said intermediate contact, a metallic mounting member affixed to said insulating means between said intermediate and bottom contacts and adapted to be connected to ground, the upper portion of said insulating means being hollow and the portion of said insulating means between said mounting member and said bottom contact being of greater section modulus than said hollow upper portion, whereby the portion of said insulating means transmitting the recoil forces incident to operation of said expulsion fuseholder to said mounting mem ber is of high strength, a lightning arrester assembly including valve material in electrical series relation with spark gap means disposed within said hollow upper portion of said insulating means and electrically connected between said upper terminal and said metallic mounting member, and means including a pair of spaced apart electrodes exterior of said insulating means one of which is connected to said upper terminal and the other of which is connected to said intermediate contact for providing a path to ground through said arrester assembly for impulse voltages on said line and for isolating said arrester assembly from said intermediate contact and said line in the event said arrester assembly is damaged.

5. A combined lightning arrester and fuse cutout comprising, in combination, an elongated insulating member having a tubular upper portion, an upper terminal, a bottom contact adapted to be connected to a load, and a contact intermediate said upper terminal and said bottom contact adapted to be connected to a power line; a fuseholder pivotally mounted on said bottom contact and latched in contact with said intermediate contact, a metallic hanger member affixed to said insulating member between said intermediate and bottom contacts and communicating with the interior of said tubular upper portion, a lightning arrester assembly within said tubular upper portion including valve elements adjacent said upper terminal and spark gap means adjacent the portion of said metallic hanger member within said tubular portion and being connected in series with said valve elements between said upper terminal and said hanger member, said spark gap means including a plurality of spaced apart metallic electrodes defining a plurality of spark gaps in series, metallic means between said electrodes and said hanger member for increasing the stray capacitance of said electrodes to said hanger member, whereby the potential distribution in said spark gap means is made more uniform and the sparkover potential of said spark gap means is stabilized, and means including a pair of spaced apart electrodes exterior of said insulating member one of which is connected to said upper terminal and the other of which is connected to said intermediate contact for providing a path to ground through said arrester assembly for impulse voltages on said line and for isolating said arrester assembly from said intermediate contact and said power line in the event of damage to said arrester assembly.

6. A combined fuse cutout and lightning arrester comprising, in combination, elongated insulating means having an upper terminal, a bottom contact adapted to be connected to a load and a contact intermediate said upper terminal and said bottom contact adapted to be connected to a line; means for affixing said intermediate and bottom contacts on one side of said insulating means, a fuseholder pivotally mounted on said bottom contact and disposed on said one side of said insulating means and being latched in contact with said intermediate contact, a metallic mounting member affixed to said insulating means between said intermediate and bottom contacts on a side of said insulating means diametrically opposed to said one side and being adapted to be connected to ground, the upper portion of said insulating means being hollow, a lightning arrester assembly within said hollow upper portion including spark gap means and valve material connected in series relation between said upper terminal and said metallic mounting member, and means including a pair of spaced apart electrodes exterior of said insulating means disposed on said one side of said insulating means one of which is connected to said upper terminal and the other of which is connected to said intermediate contact for providing a path to ground through said arrester assembly for impulse voltages on said line and for isolating said arrester assembly from said line and said intermediate contact in the event of damage to said arrester assembly, said grounded mounting member being the only metallic part protruding from said diametrically opposed side of said insulating means, whereby birds and animals resting on said mounting member and said bottom and intermediate contacts do not have ready access to a metallic part at a different electric potential and cannot easily cause a short circuit.

7. A combined fuse cutout and lightning arrester comprising, in combination, elongated insulating means having an upper terminal, a bottom contact adapted to be connected to a load, and a contact intermediate said upper terminal and said bottom contact adapted to be connected to a power line; an expulsion fuseholder, a lightning arrester assembly comprising valve elements and spark gap means in electrical series relation, said fuseholder and said arrester assembly being of approximately the same length and being substantially shorter than said insulating means, said fuseholder being pivotally mounted on said bottom contact and latched in contact with said intermediate contact, a metallic terminal afiixed to said insulating means between said intermediate and bottom contacts and adapted to be connected to ground, the upper portion of said insulating means being tubular, said lightning arrester assembly being positioned within said tubular upper portion and connected electrically between said metallic terminal and said upper terminal, and means including a pair of spaced apart electrodes exterior of said insulating means one of which is connected to said upper terminal and the other of which is connected to 9 said intermediate contact for providing a path through said arrester assembly to ground for surge voltages on said line and for isolating said arrester assembly from said line and from said intermediate contact to prevent flow of follow current through said arrester assembly in the event of damage to said arrester assembly.

8. In a protective device, the combination of an insulating member having an axial bore, a lightning arrester including valve material and spark gap means in serial relation within said bore, said spark gap means within said bore including a plurality of spaced apart electrodes defining a plurality of serially connected spark gaps, a metallic contact on the exterior of said insulating member adapted to be connected to a power line, a metallic terminal on the exterior of said insulating member adapted to be connected to ground, the potential distribution across said spaced apart electrodes being non-uniform and the leakage currents through the stray capacitance between said metallic contact and said spark gap means intensifying said non-uniformity and decreasing the sparkover potential of said spark gap means, and metallic means disposed between said metallic terminal and said spark gap means for increasing the stray capacitance between said metallic terminal and said spark gap electrodes, whereby said lastnamed means stabilizes the sparkover potential of said spark gap means.

9. A combined fuse cutout and lightning arrester comprising, in combination, elongated upright insulating means including upper and lower cylindrical insulator portions joined in axial alignment, raised circumferential petticoats on each of said insulator portions, a metallic terminal affixed to said insulating means adjacent the junction of said upper and lower insulator portions and adapted to be connected to ground, a bottom contact on the lower end of said lower insulator portion adapted to be connetced to a load, said upper insulator portion being hollow, an upper terminal adjacent the upper end of said upper insulator portion, a lightning arrester assembly within said hollow upper insulator portion including spark gap means and valve material connected in series relation between said upper terminal and said metallic terminal, an intermediate contact on said upper insulator portion between said metallic terminal and said upper terminal and adapted to be connected to a power line, an explusion fuseholder pivotally mounted on said bottom contact and latched in contact with said intermediate contact, and a pair of spaced apart electrodes one of which is connected to said upper terminal and the other of which is connected to said intermediate contact.

10. A combined fuse cutout and lightning arrester comprising, in combination, elongated upright insulating means having upper and lower cylindrical insulator portions joined in axial alignment, a metallic terminal aflixed to said insulating means adjacent the junction of said upper and lower insulator portions and adapted to be connected to ground, a first contact on said lower insulator portion spaced below said metallic terminal and adapted to be connected to an electrical load, a second contact on said upper insulator portion spaced above said metallic terminal and adapted to be connected to a power line, an expulsion fuseholder pivotally mounted on said first contact and releasably latched in contact with said second contact, said upper insulator portion being hollow, and a lightning arrester including spark gap means and valve material disposed in said hollow upper insulator portion and connected in electrical series relation between said second contact and said metallic terminal.

11. A combined fuse cutout and lightning arrester comprising, =in combination, elongated upright insulating means having an axial compartment in the upper end thereof, a metallic terminal affixed to said elongated insulating means intermediate its ends and extending from one side of said insulating means and adapted to be connected to ground, a first metallic contact affixed to said 10 insulating means adjacent the lower end thereof in spaced relation below said terminal and extending from the side of said insulating means opposite to said terminal and adapted to be connected to a load, a second metallic contact affixed to said insulating means in spaced relation above said terminal and extending from the same side of said insulating means as said first contact and adapted to be connected to a power line, -an expulsion fuseholder pivotally mounted on said first contact and releasably latched in engagement with said second contact, whereby birds and animals touching metallic parts do not have ready access to metallic parts at a different electric potential and connot easily cause a short circuit, and a lightning arrester including negative resistance valve material within said axial compartment and a plurality of spaced apart electrodes defining a plurality of spark gaps within said axial compartment connected in series with said valve material between said second contact and said terminal.

12. A combined fuse cutout and lightning arrester comprising, in combination, elongated upright insulating means having upper and lower cylindrical insulator portions joined in axial alignment, a metallic mounting member affixed to said insulating means adjacent the junction of said upper and lower insulator portions, a bottom contact on said lower insulator portion spaced below said mounting member and adapted to be connected to an electrical load, said upper insulator portion having an axial compartment therein and being open at its upper end, a lightning arrester including spark gap means and valve material disposed within said axial compartment, means for closing said open end of said upper insulator portion and for sealing said axial compartment having said valve material and spark gap means therein from the atmosphere, an intermediate contact on said upper insulator portion above said mounting member adapted to be connected to a power line, an expulsion fuseholder pivotally mounted on said bottom contact and releasably latched in engagement with said intermediate contact, said lower insulator portion being of greater section modulus than said upper insulator portion, whereby recoil forces incident to operation of said expulsion fuseholder are transmitted to said mounting member through the higher strength portion of said elongated insulating means, and an upper terminal on said closing means connected in a series circuit with said valve material and said spark gap means between said intermediate contact and said mounting member.

13. A combined fuse cutout and lightning arrester comprising, in combination, elongated upright insulating means including upper and lower cylindrical insulator portions joined in axial alignment, a metallic mounting member afiixed to said insulating means adjacent the junction of said upper and lower insulator portions and adapted to be connected to ground, a bottom contact on said lower insulator portion beneath said mounting member and adapted to be connected to an electrical load, said upper insulator portion being hollow, an upper terminal adjacent the upper end of said upper insulator portion, an intermediate contact on said upper insulator portion between said metallic mounting member and said upper terminal and adapted to be connected to a power line, an expulsion fuseholder pivotally mounted on said bottom contact and adapted to be releasably latched in engagement with said intermediate contact, and a lightning arrester including spark gap means and valve material with in said hollow upper insulator portion and said spark gap means and said valve material being connected in a series circuit with said upper terminal between said intermediate contact and said mounting member.

14. A combined fuse cutout and lightning arrester comprising, in combination, elongated upright insulating means having an axial compartment in the upper end thereof and being open at its upper end, a metallic mounting member affixed to said elongated insulating means 11 intermediate its ends and adapted to be connected to ground, a first contact afliXed to said insulating means below said mounting member and adapted to be connected to ground and having bearing portions and being adapted to be connected to an electrical load, an expulsion fuseholder pivotally mounted in said bearing portions, a second contact affixed to said insulating means above said mounting member and having means to releasably latch said fuseholder and being adapted to be connected to a power line, lightning arrester means including valve material and a plurality of spaced electrodes defining a plurality of spark gaps positioned within said axial compartment, means for closing the open upper end of said elongated insulating means and for sealing said axial compartment having said valve material and said electrodes therein from the atmosphere, said lastnamed means having terminal means extending therethrough connected in series with said valve material and said spark gaps between said second contact and said mounting member.

References Cited by the Examiner SAMUEL BERNSTEIN, Primary Examiner.

Claims

1. A COMBINED FUSE CUTOUT AND LIGHTING ARRESTER COMPRISING, IN COMBINATION, ELONGATED INSULATING MEANS HAVING AN UPPER TERMINAL, A BOTTOM CONTACT, AND A CONTACT INTERMEDIATE SAID UPPER TERMINAL AND SAID BOTTOM CONTACT ADAPTED TO BE CONNECTED TO A POWER LINE, A FUSEHOLDER PIVOTALLY MOUNTED ON SAID BOTTOM CONTACT AND LATCHED IN CONTACT WITH SAID INTERMEDIATE CONTACT, A METALLIC MOUNTING MEMBER AFFIXED TO SAID INSULATING MEANS BETWEEN SAID INTERMEDIATE AND BOTTOM CONTACTS AND ADAPTED TO BE CONNECTED TO GROUND, THE UPPER PORTION OF SAID INSULATING MEANS BEING HOLLOW, A LIGHTNING ARRESTOR ASSEMBLY WITHIN SAID HOLLOW UPPER PORTION OF SAID INSULATING MEANS INCLUDING SPARK GAP MEANS AND VALVE MATERIAL CONNECTED IN SERIES RELATION BETWEEN SAID UPPER TERMINAL AND SAID METALLIC MOUNTING MEMBER, AND MEANS INCLUDING A PAIR OF SPACED APART ELECTRODES EXTERIOR OF SAID INSULATING MEANS ONE OF WHICH IS CONNECTED TO SAID UPPER TERMINAL AND THE OTHER OF WHICH IS CONNECTED TO SAID INTERMEDIATE CONTACT FOR PROVIDING A PATH THROUGH SAID LIGHTNING ARRESTER ASSEMBLY TO GROUND FOR IMPULSE VOLTAGES ON SAID LINE AND FOR ISOLATING SAID ARRESTER ASSEMBLY FROM SAID LINE AND FROM SAID INTERMEDIATE CONTACT TO PREVENT THE FLOW OF FOLLOW CURRENT THROUGH SAID ARRESTER ASSEMBLY IN THE EVENT OF THE DAMAGE TO SAID ARRESTER ASSEMBLY.