US2427743A - Combined mountings for expulsion fuses and surge gaps - Google Patents

Description

Sept. 23, 1947. L. A. PHILLIPS [2,427,743

COMBINED MOUNTINGS FOR EXPULSION FUSES AND SURGE GAPS Filed April 10, l9 43 2 Sheets-Sheet 1 BY 6mm ATTORNEY P 1947 L. A. PHILLIPS 2,427,743

COMBINED MOUNTINGS FOR EXPULSION FUSES AND SURGE GAPS Filed April 10, 1943 2 Sheets-Sheet 2' ATTORNEY.

Patented Sept. 23, 1947 COMBINED MOUNTINGS FOR EXPULSION FUSES AND SURGE GAPS Leon A. Phillips, Hazleton, Pa., assignor to Line Material Company, Milwaukee, Wis., a corporation of Delaware Application April 10, 1943, Serial No. 482,569

3 Claims. 1

This invention relates to protective equipment for electric power systems and has to do more especially with the fusing and lightning protection of rural distribution lines.

It usually is the policy of public utility companies concerning distribution lines which are expected to carry relatively large pay loads, particularly where service interruptions must be kept at a minimum, to use the best obtainable materials throughout, including fuses and lightning arresters of the most dependable character. But in constructing rural lines where the anticipated load is small and the probable gross income per mile of line proportionately low, it often is not possible to employ the highest grade protective equipment and still be able to amortize the investment out of earnings and maintain rates which are low enough to induce a major portion of the prospective customers to utilize the service.

On the other hand, rural service is mainly of a domestic character, with respect to which periodic outages are not altogether intolerable; and the average farmer is willing to put up with occasionable blackouts in order to obtain electric service at a price which is comfortably within his reach.

As a part of the effort to provide reasonably satisfactory service notwithstanding inadequate operating income, there has heretofore been widely used an inexpensive, unhoused, nondropout expulsion fuse designed to be suspended directly from a line wire and capable of being quickly and easily installed. Such equipment is operative, but it is not good practice to use line wires as supporting media.

In addition to fusing the lines against overloads .and short circuits, the transformers must be protected against lightning and other heavy surge discharges; and the desirable Way to accomplish that end is to provide lightning arresters of the kind which function dependably to prevent power current flowing to ground following each surge discharge-which flow to ground inherently gives rise to more or less widespread outages through the operation of sub-station circuit breakers or the blowing of feeder line main fuses. Lightning protection, per se, can be achieved through the use of a simple spark-gap connected between line and ground, but such an expedient provides only for diversion of the high voltage surges and usually results in line outages due to power current being short-circuited to ground whenever lightning strikes. In some lo- 2 calities that means lines out of commission almost every time there is a lightning storm.

The present invention has for its object to provide means which, at the least possible cost, will render it feasible to provide better fusing and adequate lightning protection for rural lines; and to that end the invention consist-s, in part, in providing an arrester of the expulsion gap type of inexpensive design, and a mounting for the same which will also accommodate an expulsion type line fuse of the kind previously mentioned which was originally designed to be suspended on a line wire. My new mounting is designed for attachment either directly to a pole or alternatively to .a cross-arm, and in either case includes an open gap in series with the expulsion gap device. A feature of the invention, both as respects the fuse and the expulsion gap is that both those devices can easily be attached and removed, and there are ample clearances to enable servicemen to operate without inconvenience and to assure against short-circuiting, while at the same time the whole installation is not overlarge and the cost is such that its use is economically possible on a large percentage of rural lines.

In order fully to appreciate the significance of the present invention, it must be realized that what .is sought is improved rural service at the least posssible added cost; and it must be taken into consideration that over-all operating cost includes not only depreciation and interest on original investment, but also cost of service maintenance. Outages spell both man-hours, which have to be paid for, and loss of revenue during service interruptions, and when those factors are weighed it is found that the present invention is a contribution to rural line economy-even with out evaluating the good will which is a reflection of improved service.

The devices of the present invention are characterized by simplicity and low cost, yet without sacrifice of essential structural strength and rigidity; and they are further distinguished by ready adaptability for attachment to poles and cross-arms and accessibility for servicing.

Two embodiments of the invention are depicted in the accompanying drawings, wherein:

Fig. 1 is a front elevational View of .a rural line fuse and gap mounting in conformity with this invention;

Fig. 2 is an endwise elevational view of the structure of Fig. 1;

Fig. 3 is an enlarged view of the upper end of a fuse or expulsion gap Fig. 4 is an endwise elevational view of an alternative form of the invention; and

Fig. 5 is a front elevational view of the structure of Fig. 4.

In Figs. 1 and 2 reference numeral I identifies a fragment of a power line pole to which the fuse and expulsion gap mounting is shown attached. The mounting, as a whole, is identified by reference numeral 2, While the fuse is designated by numeral 3 and the expulsion gap by numeral 4. The device is ordinarily used in conjunction with a distribution transformer and is supported on the same pole. The function of the fuse is, of course, to protect the line and transformer against the injurious effects of overloads and short circuitswhich it does by interrupting the line circuit; and the primary function of the expulsion gap is to provide an easy path to ground for lightning and other high voltage surges, thus diverting the high potential currents away from the transformer windings.

Fuse 3 is of a type which was designed originally to be hung directly on a feeder line wire at a junction point where a branch line is connected to the feederthere being a distribution transformer at said junction, to the primary side of which the fuse is connected in series. The fuse comprises an expulsion tube 5 which may be of horn fiber or of some other insulating material, such as Bakelite, lined with fiber or other gasevolving material. To the upper end of the expulsion tube (see Fig. 3) is secured a metal ferrule 6 from which projects laterally a downwardly extending hook 'I, to the lower end of which is riveted an upwardly extending leaf spring 8. From the opposite side of the ferrule there projects a loop 9 which is designed for engagement with a hot stick; and to the upper end of the ferrule is detachably secured a cap IE), which is threaded to the ferrule and removable to permit a fuse-link to be inserted in the cartridge. Ferrule 6 and cap IO, conjointly, constitute terminal means for grippingly engaging the upper end of the fuse-link and establishing electrical contact therewith. The bore of tube 5 is open at its lower end and is closed at its upper end by cap I0.

Attached to the lower end of tube 5 is a metal collar I I designed to receive a conventional splitbolt connector I2, and having an integral laterally projecting arm I3 which terminates in a flip-out mechanism I4 designed to operate, when the fuse blows, to withdraw from the open lower end of the tube a flexible conductive leader I5 which forms the lower terminal of the fuse-link. The flip-out mechanism is described in Reissue Patent No. 22,149 to William O. Schultz. The fuselink is of conventional design and includes a fusible section situated within the upper portion of the bore of tube 5 and normally kept under tension by the action of the flip-out mechanism on leader I5. The split-bolt connector I2 is electrically connected through collar II, arm I3 and mechanism I4 to the leader I5, and is designed for attachment to one primary terminal of a branch line transformer.

Expulsion gap 4 is identical externally at its upper end with the upper end of the fusesee Fig. 3. Here the parts corresponding to fuse parts B-I I) inclusive are numbered Iii-26 inclusive. Tube 2| may be of horn fiber or of other insulating materials, such as Bakelite, lined with horn fiber or other gas-evolving material. The bore is open at its lower end. Inside tube 2] and extending downwardly from ferrule I6 and cap 20, to

Which it is connected, is a rod (not shown) Which functions as a spark electrode. This rod extends only part way down the bore of tube 2I, and the remainder of the bore constitutes an enclosed constricted passageway which forms at least the major portion of the spark-gapall of which is in keeping with well known practice. To the lower end of tube 2| is secured a metal ferrule 22 which serves as the lower spark electrode; and integral with said ferrule is a laterally projecting arm 23 which is adapted to receive a split-bolt connector 24. The latter is intended for connection to a ground wire 25.

The mode of operation and purpose of expulsion gap devices are familiar to those who are employed in the construction and maintenance of power distribution systems. But for the information of those who may not be versed in this art, it seems worthwhile to state that the function of the device is to provide a medium through which lightning discharges and other high voltage surges can find an easy path from the line conductor to ground, but which will not provide a path over which power current can flow to ground. An ordinary spark-gap, without any arc-extinguishing means will function to permit discharge of lightning to ground, and such a gap would meet all requirements were it not for the fact that ionization thereof b the high voltage discharge transforms the gap into a conductive space path for power current, which will continue to flow after the initial surge has subsided and until a fuse or circuit breaker, operating as a consequence of such flow, opens the line circuit, as well as the ground circuit, and thus causes a line outagewhich spells interruption of service until the fault is cleared. In order to forestall such outages it is necessary to extinguish quickly or prevent the formation of a power circuit are in the spark-gap; and that is the function which is achieved in an expulsion gap device over and above and in addition to the function of a simple gap. Extinction of the are which forms between the spaced electrodes of device 4 is brought about b the fact that the fiber bore surface of tube 2I has the property, when subjected to the high temperature of an arc, of evolving arc-extinguishing vapor or gas which de-ionizes the arc path. If the power current is of substantial magnitude, gas is evolved in such volume and expanded so rapidly within the bore of the tube that the discharge thereof from the open lower end of the tube takes place with explosive violence. The explosion sweeps out of the tube bore all or most of the ionized particles which would serve to maintain a conductive path, and when, thereafter, the alternating power current has reached and passed the succeeding zero point of its cycle and is again increasing in magnitude, there no longer obtains the space ionization which is a condition precedent to ability of the applied power voltage to re-establish the arc.

Mounting 2 includes a Z-shape strap 26, the upper vertical 16g of which is shown secured to pole I by means of lag-screws or bolts 21. The lower vertical leg of strap 26 is attached, by means of machine screws 28, to one end of a porcelain or glass insulator 29 which serves to insulate all live parts from the pole. Insulator 29 has a metal insert 3!! at one end, having tapped holes to accommodate screws 28, and has a second metal insert 3I at the opposite end which is tapped to accommodate an additional pair of machine screws 32, 32. The two metal inserts 30, 3I are not electrically connected.

An angle iron 33 is attached at its mid-portion,

by means of screws 32., to insert 3| and depending from one end thereof is a metal stirrup 34 which is secured to the angle iron by means of two bolts 35 35. Interposed between angle iron 33 and stirrup 34 is the upstanding leg 36a of a guideplate 36 having a hornizontal leg 36b. Stirrup 34. is formed with an integral horizontal bar 340. which is proportioned for engagement with the bight of hook 1, as clearly shown in Fig. ,2. As will be apparent, fuse 3 is hooked onto stirrup 34 and firmly secured thereto by the pressure exerted by spring 8. The horizontal leg 36b of guide-plate 36 overlies the upper end of the fuse and serves as a guide when inserting the fuse in the stirrup. The utility of such a guide will be more evident when it is considered that the fuse usually is mounted by means of a long hot-stick engaging loop 9.

Stirrup 34 has an integral lug 34b which is apertured to receive a split-bolt connector 31 by means of which connection is made to the feeder line. The upper terminal of the fuse-link is thus connected to line through the medium of ferrule 6 and stirrup 34. The other terminal of the fuselink is connected to the branch line-usually a transformer primary terminal-through the me dium of split-bolt connector I2.

Also connecteed to angle iron 33 and depending therefrom is a second insuiator 38, having a metal insert 39 at its upper end which is tapped to receive a pair of machine screws 40, 40 by means of which the insulator is secured to the angle iron. The lower end of insulator 38 has a metal insert 4!, to which is attached by machine screws 42 a depending metal stirrup 43, which is similar to stirrup 34 except that it is not provided with a split-bolt connector and is provided with a rightangular base portion at its upper end having apertures for screws 42. Also attached to insert 4 I, by means of screws 42, is a plate 44 and a metal strip 45 which functions both as a spark-gap electrode and as a guide for aiding the lineman when at-- taching the expulsion gap device by means of a hot-stick. The purpose of plate 44 is to prevent expulsion gap 4 being attached to stirrup 43 at the wrong side thereof. Since the lower terminal of the expulsion gap is grounded it is necessary to maintain adequate spacing between it and the lower terminal of the fuse, and if the gap device were turned around that spacing would be decreased.

The upper end of spark electrode 45 is spaced to form a gap at 46 with one end of angle iron 33, the latter being tapered, as shown, to form a sparking point. It will be observed that gap 46 is in series with expulsion gap 4 and forms a part of the path to ground. Gap 46 serves normally to isolate the expulsion gap from the line and thereby precludes the possibility of power current leaking to ground through tube 2| of the expulsion gap device.

It will be seen that the above-described mounting comprises only simple insulators-which are not costlytogether with other parts which are easy to make and assemble, and entails the use of a minimum of material. The new mounting permits of the use of a type of expulsion fuse which is standard equipment and comparatively inexpensive, while at the same time being adapted to receive an expulsion gap which is similarly inexpensive.

The alternative structure of Figs. 4 and differs in form but not in function or mode of operation from the structure of Figs. 1 and 2. Either Structure can be attached to a cross-arm or directly to a pole. As illustrated, the structure of Figs. 1 and 2 is attached directly to a pole whereas the structure of Figs. 4 and 5 is adapted more particularly for attachment to a cross-arm.

But these are not distinctions which substantially differentiate the two embodiments.

In Figs. 4 and 5 the fuse and expulsion gap devices are identical with those of Figs. 1 and 2 and they are identified by reference numerals 3 and 4, respectively. All component parts of the fuse and expulsion gap devices of Figs. 4 and 5 bear primed reference numerals in conformity with their counterparts in Figs. 1 and 2.

The mounting includes a vertical channel iron 47 apertured to accommodate a pair of bolts 48, 48' which are spaced apart sufficiently to embrace between them a cross-arm, not shown. A piece of strap iron 49 drilled to match the bolt holes in channel 4! is designed to bear against the cross-arm oppositely to said channel and provide an anchorage for the bolts. Piece 49 operates conjointly with channel 41 and bolts 48 to secure the mounting to the cross-arm. An advantage intrinsic in this type of mounting is that no bolt holes need be bored in the cross-arm and the structure can be moved along the cross-arm, after loosening nuts 55, for the purpose of adjusting or changing its position.

Secured to the lower end of channel 47, by means of machine screws 5!, is an insulator 52 having a metal insert 53 which is drilled and tapped to receive screws 5!. Clamped between the web of channel 41 and the base of insert 53 is a bent metal strip 54 which constitutes one of a pair of gap electrodes defining a spark gap 55 in shunt to insulator 52. The companion gap electrode is a metal strip identified by reference numeral 56.

The other end of insulator 52 has a metal insert 5'! to which is secured by machine screws 58, 59 a second Vertical channel iron 60, bent offset, as shown, to conserve space and carrying at its upper end a second insulator 6|, attached thereto by a pair of machine screws 62, 62, which also serve to secure to the channel iron the metal strip 56.

The outer end of insulator 6! has a metal insert 63 which is drilled and tapped to receive a pair of machine screws 64, 64 by which are secured to insert 63 a brass double-stirrup casting 65 and a, sheet metal hood or guide-plate 66, having the same function as guide-plate 36 of Figs. 1 and 2. Casting 65 is skeletonized as shown and includes two horizontal bar portions 65a and 655 on which are hung, respectively, expulsion gap device 2| and expulsion fuse 5. It will be observed that casting 65 performs the same functions as the two stirrups 34 and 43 of Figs. 1 and 2, and it is for that reason that I herein refer to casting 65 as a double stirrup casting. Said casting has oppositely projecting ears 65c and 65d, each of which is pierced as shown at 65d to form two segmental openings divided by a narrow bridge of metal 65c, which is proportioned to fit the slot of a split-bolt connector 66. The latter can be secured to either of the two ears 550 or Wei-whichever happens to be the more convenient. Connector 66 is connected to a line wire by means of conductor 61.

t will be seen that the upper terminals of both the fuse and the expulsion gap device are normally at line potential. In the embodiment of Figs. 1. and 2. only the fuse has its upper terminal normally at line potential, the expulsion gap being isolated from the line by reason of gap 46.

The lower connector I2 of fuse 5' is usually connected to a transformer primary terminal by means of a conductor 68, and the lower terminal connector 24' of expulsion gap device 2| is connected via conductor 69 to a split-bolt connector 10 which is carried by an angle clip I l--the latter being attached to channel iron 60 by means of screw 58.

It will be observed that the lower electrode 22' of expulsion gap device 2| is connected to ground via conductor 69, connector 10, clip H, channel iron 60, gap electrode 56, gap 55, gap electrode 54, channel iron 41, split-bolt connector 12 and ground wire 13; and it will be seen that gap 55 is on the ground side of the expulsion gap device whereas in the structure of Figs. 1 and 2 gap 45 is on the line side of expulsion gap device 4.

A feature which has been incorporated in the structure of Figs. 4 and 5 is a cross-bar 14. This is secured at its middle to channel iron 60 by means of screw 58 and is bent at Ma and Mb to embrace the two flanges of channel iron 60 in such manner as to prevent rotation of the crossbar around screw 58. The cross-bar has two oppositely projecting arms which are notched respectively at 14c and 14d, which portions are designed to engage the hooks, respectively, of the expulsion gap device and the fuse, when these are removed by a lineman from their normal positions on castin 65 and hung on the crossbar. By virtue of cross-bar 14 it is unnecessary for the lineman to leave the expulsion gap device and fuse dangling on conductors B9 and 98 while he is working on the pole.

What is claimed is:

1. Electrical protective equipment comprising an expulsion fuse and an expulsion gap device, said fuse and said device each being mountable and demountable independently of the other and provided at its upper end with a terminal having an attachment hook whereby it is adapted to be suspended from a support and to make electrical connection to said support, said hooks being characterized in that they render said fuse and said device quickly attachable and detachable to and from their said support, and unitary mounting means for said fuse and said device, said mounting means including a member adapted for attachment to a pole, an insulator secured at one end to said member and projecting therefrom, a second member secured to the other end of said insulator and carried thereby, a second insulator secured at one end to said second memher and carried by said second member, a pair of stirrup-like supporting means for said fuse and said device, at least one of said supporting means being carried by said second insulator, said fuse and said device being held in spaced relation by said supporting means, said mounting means also including an open gap connected in series with said expulsion gap device.

2. Electrical protective equipment comprising an expulsion fuse and an expulsion gap device, said fuse and said device each being mountable and demountable independently of the other and provided at its upper end with a terminal having an attachment hook, and unitary mounting structure for said fuse and said device, said mounting structure including a bracket member adapted for attachment to a pole, an insulator secured at one end to said bracket member and projecting therefrom, an elongated conductive member secured at its mid-portion to the other end of said insulator and extending horizontally in opposite directions therefrom, a conductive stirrup secured to and depending from one end portion of said conductive member, said stirrup having a horizontal bar portion at its lower end which is adapted to receive the hook of said fusc terminal, said stirrup serving as a support for said fuse, a second insulator secured to and depending from the other end portion of said conductive member remotely from said stirrup, a second stirrup secured to and depending from the lower end of said second insulator and having a horizontal bar portion at its lower end for receiving the hook of said expulsion gap device terminal, said second stirrup serving as a support for said expulsion gap device, and a spark-electrode secured at one end to the lower end of said second insulator and forming a spark gap with said conductive member.

3. Electrical protective equipment comprising an expulsion fuse and an expulsion gap device, said fuse and said device each being provided at its upper end with a terminal having an attachment hook, and unitary mounting structure for said fuse and said device, said mounting structure including a Z-shape bracket member having one vertical leg adapted for attachment to a pole, an insulator secured at one end to a second vertical leg of said bracket member and supported thereby in a horizontally projecting posture, an angle iron secured at its mid-portion to the other end of said insulator and extending horizontally in opposite directions therefrom, a metal stirrup secured to and dependin from one end of said angle iron and having a horizontal bar at its lower end for detachably receiving the hook of said fuse for dependingly supporting said fuse, a terminal connector secured to said stirrup for effecting electrical connection with the upper terminal of said fuse, a second insulator secured to said angle iron and depending therefrom at a point remote from said stirrup, a metal strip secured to the lower end of said second insulator and extending upwardly to form a spark-gap with one end of said angle iron, a second metal stirrup secured to and depending from the lower end of said second insulator and having a horizontal bar portion at its lower end for receiving the hook of said expulsion gap device for dependingly supporting said device, and a plate secured to the lower end of said second insulator and extending downwardly therefrom adjacent said second stirrup, said plate serving to prevent said expulsion gap device being positioned on the wrong side of said second stirrup.

LEON A. PHILLIPS.

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

UNITED STATES PATENTS Number Name Date 2,137,270 Crump Nov. 22, 1938 2,169,104 Lincks Aug. 8, 1939 2,170,337 Pittman et a1. Aug. 22, 1939 2,171,179 Johnson Aug, 29, 1939 2,272,370 Fox Feb. 10, 1942 2,294,833 Cooley Sept 1, 1942 1,409,927 Christensen Mar. 21, 1922 1,759,253 Gerhardt May 20, 1930 2,049,552 Walsh Aug. 4, 1936

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