US2498575A - High-voltage fuse construction - Google Patents

Description

Feb. 21, 1950 R. R. PITTMAN 2,498,575

HIGH-VOLTAGE FUSE CONSTRUCTION Filed Aug. 4, 1947 INVENTOR Patented F eb. 21, 1950 UN IT ED STATES PATENT. O FFICE HIGH-VOLTAGE" FUSE CONSTRUCTION Ralph ll.. Pittman, North Little Rock, Ark,

Application August 4, 1947, Serial No. 765,927"

5 Claims-- (Cl.- 200-113-)- This invention relatesi generall to fusesior electric circuits; and more specifically to a fuse construction suitable forause'on circuits operating onvoltages commonly classified as transmission line voltages; e. g; 66 kv; and greater. 7,

The objects- 0f the inventioninclude the provision of a relatively inexpensive fuse'construction adapted for highlvolta ge circuits which is at a the: same time 1 effective for the interruption of' currentoverva wide range extending-from a few amperes tov severalirthousanduamperes; the provisionof o a. fuse 1 construction: 1 of: the above mentioned abilityv which .is particularly adapted to applicationii'to /circuits"provided witha grounded source; the provision of a fuse construction iembodyin'g'itwoexpulsion fusebarrels in series.- arrangement zfiiniz which a predetermined sequence-of :meltinglo'f the fusible elements ofthe fuse: linkwithin;thesrespective barrels is caused to occur in: responsetopassageoi a'predet'ermined current: throughthe fuse-slink and" the provision ofa construction' utili'zing the conducting dis charge: gas attending: operation to efiectcertain definite and favorable-alteration of the fault cur rent to'be interrupted by the fuse. Other objects will be'ob'vious from the description tofollow; or pointed outth'ereinllr In the?accompanying drawing, FigL 1 is-a side elevati'onal viewiof a fuse construction constructed in accordance: with the presentinvention Fig: 2 is an: end elevational view; Fig. 3 is a diagrammatic 1 sketch illustrating' :the' application of the invention toia single phase circuit; Fig; 4 is afrag mentary view or" a portion of one of the :fuse ba'r relszofi the device with' a portion broken-awayto show the contained.-fusible element; and Fig. 5 is a 'similar 'view oi a portion of 'the'other fuse barrel.

It is Well known that a fixed -b'ore expulsion fusecmayi be readily! constructed as arr effective circuit interrupting devi'ce forany circuit voltage if 'the' currerit to be interrupted is not too great tciburstath'e: expulsion barrel :from internal pressure;ior.* is not too small-to'cause" sufficient gas generation tolextinguish th'e' are playing within the barrel that "is, within well defined limits of current to beinterrupted; the expulsion fuse is an "efficient'. device. However, as a protective device for the highivoltage sidev of transformers operating 'at'transmission line voltages the expul. sion fuse has not been" satisfactory: becausev the current to be interruptedfmay vary; from'ia few amperes. due-to a fault on the" low voltage side, to a high current value equal to thevlin'e-toground faultv current, often severalthousand -.am'-

peres." Sincethe line-to-groundfault current is relatively constant at any .pointon a transmission system} an arrangement assuring that this current would pass through an expulsion barrel re gardless of the current causingthe fusingof a fusibleelement'of the fuse link solves the variable current problem and results' insanl eflicientland inexpensive interrupting device; The manner in whichathe' pre'sent invention solves the problem above described, which 'has existed from the first time:expulsion fuseswere: used on high voltage circuits; will. be clear- -from: the' following description.

Referring to Fig: 1 of the drawing, a metal base H], which in common'pra'ctice is grounded as-indicated symbolically at 39, lhas-rigidly secured thereto', as by welding, anoutwardly extending. conducting member H. Mounted-at the respective ends of the base [0- are the insulator stacks l2 and [3, by means'of the bolts 25. At the top of stack 12 is mounted, by'means' of the bolts I 8, the source terminal 14 and the upwardly extending source fuse barrel mount IS; the latter beingformed ofconductingmaterial and disposedin conductive relation with the source terminal [4: Similarly, atthetop of the stack [3 is mounted; by'meansofthe bolts 19, the 1 load terminal [5 and the-upwardly extending load fuse barrel mount I 1; the latterbeing also formed of conducting material and: mounted in conductive relation with the loadterminal [5.

The source expulsion fuse barrel ZZ hasrigidly fastened thereto at'its upper end the metal'ferrule 34, and'is rigidly securedto the inclined portion 2il 'of the source'fuse mount lfi'by'th'e U bolts 24 in such a position that the barrel extends downwardly and'outwardly from the upper end of the fuse mount l6 and ispointed toward an outwardly extend'ed portion: of the: conducting member ll. Similarly, the load expulsion fuse barrel 23 is provided withitheferrule33 at the upper end'thereof, and the latter clampedto the inclined portion 21 of the load fus'e'mount Why the U bolts24in-su'ch a position that the load fuse barrel extends downwardly and outwardly from the upper end of the fuse mount l'l 'i'nthe direction toward and spaced from both the outwardly extending conducting member ll andthe lower end of the source fuse barrel fl." Preferabl the fuse barrelsare arranged, as shown, so that the longitudina1= axis of each if" produced intersects the conducting member ll at'a common point. The fuse barrels are open at each end, and formed from material -commonl used :in the construction of expulsion iuses, suches hardfiber;orother material capable of producing a gas blast when an arc occurs within the barrel.

The fuse link 26 has one end thereof connected to the source fuse mount [6 at the terminal 30, extending first downwardly through the source fuse barrel 22, thence across the space separating the respective lower ends of the fuse barrels to the lower end of the load fuse barrel 23, thence upwardly therethrough to the terminal 29 at the upper end of the fuse mount H, and thereby electrically connecting the terminal 14 to the terminal l through the fuse link 26. Two longitudinally spaced fusible elements 2'! and 28 are pro vided in the fuse link 26, as shown in detail in Figs. 4 and 5, the higher current element 21 being contained by the source fuse barrel 22, and the lower current element by the load fuse barrel 23, Under certain conditions it maybe desirable that the bore 43 of the load fuse barrel be smaller than the bore 44 of the source fuse barrel, although this is not essential to correct operation of the device under other conditions. Also, under certain conditions, more particularly those in which load current is of substantial magnitude, the fusible elements may approach each other as to fusing current, or even equal in this respect.

In situations where load currents are too small to provide the desired expulsion of the fuse link 26 from the load fuse barrel 23, a fuse link extractor 3! is mounted on the lower ferrule 32 and arranged to continuousl urge the fuse link in endwise direction out of the bore of the barrel. The fuse extractor 3! is formed of a strip of a resilient material one end of which is rigidly secured to the ferrule 32 by the screws 35, and the other end hooked over the fuse link 26 when the strip is deformed, to urge the fuse link in endwise direction away from the fuse barrel.

Fig. 5 illustrates diagrammatically an application of the invention to a single phase circuit, although it is clear that it may be similarly employed in a three phase circuit. The high voltage winding of the source transformer 36 is grounded at 38, and the other end of the high voltage winding connected through the source conductor 3! to the source end of the fuse construction. In like manner, the high voltage winding of the load transformer 41 is connected to ground at 12, and the load conductor 40 extended to the load side of the fuse construction.

Assuming that a fault occur-s on the low voltage winding of the transformer it 'while the fuse link 26 is in the position illustrated in Fig. l, the relatively small excess current as limited by the impedance of the transformer fuses the low amperage element 28 within the load fuse barrel 23. The fuse extractor 3! urges the fuse link 26 out of the load fuse barrel 23, and in falling, the fuse link 26 contacts the grounded fuse link interceptor l i having moved to the position shown by the dashed line of Fig. 1. Since the source transformer is also connected to ground, full line-to-ground shirt circuit current now passes through the fusible element 21 of the source fuse tube 22, fusing the fusible element and causing efiective expulsion action within the latter for interrupting the circuit. An are, if any exists within the load fuse barrel 23 prior to contact of the fuse 2G with the grounded interceptor II, is of course instantly extinguished by such contact, since ground voltage is then impressed across both terminals of such arc. A portion of the fuse link 26 may take the position shown in Fig. 3, or may fall to the ground, this matter being of no importance in the operation of the device.

In the event of a direct load conductor-to ground fault, both fusible elements will be fused at substantially the same time, and in certain situations the conducting gas expelled from the fuse barrels will effect the desired source conductor-to-ground fault current through the source fuse barrel 22 to assure circuit interruption therein. It will also be clear that it is not essential that the conducting member H be physically contacted by the fuse link 26; it is sufiicient that conducting gas attending expulsion action bridge the space between the lower end of the source fuse tube 22 and the grounded member II, and further, this gas may originate in either of the fuse barrels.

It may be observed that the construction herein not only assures sufficient fault current to effect efiicient circuit interruption, but also assures that both of the fusible elements will be fused and thereby provides a definite open circuit in air between the lower ends of the fuse barrels after operation. The latter feature becomes an important consideration when the fuse construction is applied to polyphase circuits, because of the possible feed-back through a high voltage winding of a load transformer connected to an unaffected phase conductor.

I claim as my invention:

1. A high voltage fuse construction for use between a grounded source and a load; comprising a metal base, a grounded conducting member rigidly mounted thereon and extending laterally therefrom, spaced insulators carried by said base and extending upwardly therefrom, source and load terminals mounted respectively on said spaced insulators, upwardlyextending fuse barrel mounts fastened at their respective lower ends to each of said spaced insulators in conductive relationship with the source and load terminals respectively, expulsion fuse barrels mounted on the respective upper ends of said fuse barrel mounts and extending outwardly and downwardly therefrom in spaced relationship and each in the direction toward and spaced from said grounded member, the respective lower ends of said fuse barrels being open, and the grounded member positioned in the path of gas expelled from the respective open ends of said expulsion fuse barrels, and a fuse link extending serially through said expulsion fuse barrels and electrically connecting' said fuse barrel mounts, said fuse link being provided with two longitudinally spaced fusible elements, one of said fusible elements being positioned within one fuse barrel and the other of said fusible elements being positioned within the other fuse barrel.

2. Th construction recited in claim 1, characterized by said fusible elements having unlike fusing characteristics.

.3. A high voltage fuse construction for use between a grounded source and a load; comprising a metal base, a grounded conducting member rigidly mounted thereon and extending outwardly therefrom, spaced insulators carried by said base and extending upwardly therefrom, source and load terminals mounted respectively on said spaced insulators, upwardly extending fuse barrel mounts fastened at their respective lower ends to each of said spaced insulators in conductive relationship with the source and load terminals respectively, expulsion type source and load fuse barrels mounted on the respective upper ends of said fuse barrel mounts and extending downwardly and outwardly therefrom in spaced relationship, each of saidfuse barrels being open at their respective lower ends and pointed toward said load fuse barrel and a source fusible element i located within said source fuse barrel, said load fusible element being adapted to fuse upon passage of a predetermined load current therethrough, and said source fusible element being adapted to remain unfused upon passage of said predetermined load current therethrough and to fuse upon passage of a source-to-ground current therethrough which is greater than said predetermined load current, said grounded member being positioned in the path of gas expelled from the respective lower ends of said expulsion fuse barrels.

4. In a high voltage fuse construction, a con ducting base, insulating means thereon supporting spaced terminals, spaced downwardly extending open-ended expulsion fuse barrels mounted on said insulating means and so positioned that the direction of gas discharge from each barrel converges at a common point, a fuse link embodying one fusible element within one barrel and another fusible element within the other barrel, said fuse link extending serially through said expulsion fuse barrels and electrically connecting said spaced terminals, a grounded conducting member rigidly secured to said base and extending to said common point, and a fuse link extractor associated with said fuse link and arranged to eject a portion of said fuse link from one of said barrels when the fusible element therein fuses, said grounded member being positioned in the path of the ejected portion of said fuse link.

5. In a high voltage fuse construction, a conducting base, insulating means thereon supporting spaced terminals, spaced downwardly extending open-ended expulsion fuse barrels mounted on said insulating means and so positioned that gas discharge from each barrel converges at a common point, a fuse link embodying one fusible element within one barrel and another fusible element within the other barrel, said one fusible element fusing at a predetermined current less than the fusing current of said another fusible element, said fuse link extending serially through said expulsion fuse barrels and electrically connecting said spaced terminals, and a grounded conducting member rigidly secured to said base and extending to said common point.

RALPH R. PITTMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,928,625 Kyle Oct. 3, 1933 2,390,670 steinmayer Dec. 11, 1945

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