CA1109106A - Load-break fuse equipment - Google Patents
Load-break fuse equipmentInfo
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- CA1109106A CA1109106A CA330,884A CA330884A CA1109106A CA 1109106 A CA1109106 A CA 1109106A CA 330884 A CA330884 A CA 330884A CA 1109106 A CA1109106 A CA 1109106A
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- load
- break
- receptacle
- fuse
- drawout
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Abstract
LOAD-BREAK FUSE EQUIPMENT
Abstract: This load-break fuse equipment comprises two draw-out fuse assemblies, one of the load-break type and one of the non-load-break type, each removably mounted in its own individual receptacle. The load-break fuse assembly and its receptacle comprise-a load-break switch and a fuse electrically connected in series with each other. The non-load-break fuse assembly comprises a fuse, and this fuse is electric-ally connected in parallel with the fuse of the load-break fuse assembly and in series with said load-break switch.
Abstract: This load-break fuse equipment comprises two draw-out fuse assemblies, one of the load-break type and one of the non-load-break type, each removably mounted in its own individual receptacle. The load-break fuse assembly and its receptacle comprise-a load-break switch and a fuse electrically connected in series with each other. The non-load-break fuse assembly comprises a fuse, and this fuse is electric-ally connected in parallel with the fuse of the load-break fuse assembly and in series with said load-break switch.
Description
11091~6 SDS283 Background This invention relates to load-break ~use equipment comprising a tubular receptacle and, removably mou~ted with-in the receptacle, a load-break drawout assembly that com- ~ ;
l prises a use and the mova~le contact of a load-b~eak switch.
5 ¦ Examples of load-break fuse equipment of this type are disclosed in U.S.-Patent 3,471,816-Giegerich; 3,628,092-Xeto;
and 4,0-59,816-Bonecutter et al. In certain~applications of such load-break fuse equipment, the largest diameter single fuse that is receivable within the receptacle may not have sufficient current-carryin~ or current-interrupting capacity for the power circuit in which the equipment is to-be con-~nected. ~For such high current applications, it is con-¦ventional to provide two identical load-break use-equipments 1f this type and to connect them electrically in parallel.
¦ While this approach can provide increased current-¦caxrying-and current-interrupting capacity while the two ¦load-break drawout assemblies are in place within their ¦receptacles, it is subject to the distinct disadvantage that ¦the desired current-interrupting capacity is not present ¦during certain inter~als while the load-break drawout assem- ¦
¦bl~es are being removed from or being inserted into-their ¦receptacles. More specifically, if one of the load-break ¦drawout assemblies of such prior e~uipment is withdrawn, the ¦fuse of the xemaining assembly must alone provide current ¦interrupting ability until the remaining assembly is with-¦drawn. This same condition is, of course, present if one ¦of the load-break drawout assemblies is inserted before the ¦other one.
- ¦¦ 5D5283 91~6 Summary ¦ An object of this invention is to provide load-break fuse equipment of this general type that comprises fuses connected in parallel, which fuses remain connected in parallel both during removal and insertion of the load-break -5~ drawQ.ut assembly.
AnQther object is to provide load-break fuse equipment comprising~a tu~ular receptacle and a load-break drawout assembly removably moun~ed therein, which equipment is con-strncted in such-a way that a separate fuse can readily be 10~ connected in parallel with the fuse of the .drawout assembly and.in series with the load-break.switch within the recepta-. cle,.all without interfering wi.th the~easy removability ofthe drawout assembly and the ability of the load-break switch : to interrupt load currents coincident with removal of drawout .15 assembly.
. Anothex object is to achieve the immediately-preceding :. obj.ect without interfering with easy insertability of the .dxawout assembly and the ability of the load-break switch to . close against currents coincident with such insertion, e.g., .20 ~ inrush currents.
: In carrying out the invention in one form, we provide . two spaced-apar~ tubular receptacles mounted on a wall. Each recep~acle comprises an outboard contact and an inboard con-¦tact at axially-spaced locations along the bore of the recep-tacle,~first tubular.insulating structure between said con-tacts, and second tubular insulating structure between the outboard contact and.said wall. One of the receptacles further compri.ses a generally stationary load-break contact at its inner end and a third tubular insulating portion - ~91~6 5D5283 between said load-break contact and its inboard contact.
Insertable as a unit into said one receptacle is a load-break drawout assembly comprising a fuse, two sliding contacts at opposite ends of the fuse, a movable load-break contact inboard of the fuse, and an insulating drawou~ rod outboard of the fuse. When this drawout assembly is f~lly inserted, the movable load-break contact engages the station-ary load-break contact and the two sliding contacts respectiv, 3-ly engage the inboard and outboard contacts of said one re-ceptacle. Insertable as a unit into the other receptacle isa non-load-break drawout assembly comprising a fuse, two sliding contacts at opposite ends of the fuse, and an insu-lating drawout rod outboard of the fuse; said two sliding contacts respectively engaging the inboard and outboard con-lS tacts of said other receptacle-when said non-load-break drawout assembly is fully inserted.
Means is provided for electrically connecting said two-fuses in parallel with each other and in series with said load-break contacts comprising a first conductor interconnect ing th~e outboard contacts of the two receptacles and a second conductor interconnecting the inboard contacts of the two receptacles.
Brief DescriPtion of Drawinqs For a better understanding of the invention, reference may be had to the following description taken in conjunction ith the accompanying drawings, wherein:
Fig. 1 is a side elevational view, mostly in section, showing load-break fuse equiDment embodying one form of the invention.
`- ll i~ 9 ~ 6 5D5283 Fig. 2 is a sectional view of an interlock used with ¦the fuse equipment of Fig. 1 for ensuring a predetermined se~uence of operations during withdrawal and insertion of the drawout fuse assemblies. Fig. 2 depicts both *rawout assembli~s in their fully inserted positions.
Fig. 3 is another view of the interlock of Fig. 2 ¦showing the interlock with the drawout fuse assemblies re-mo~ed.
Detailed DescriPtion of Preferred Embodiment Referring now to Fig' 1, the illustrated load-break fuse-equipment comprises a tubular receptacle 10 that is mounted on a wall 12 of electrical apparatus such as a pad-mounted-distribution transformer. The wall 12, which may be f metal, contains an opening through which the tubular re-ceptacle 10 extends r with the bore of the receptacle general-ly aligned with the opening. A flange 14 on the outer end of the receptac~e 10 is attached to the wall 12 by suitable fasteni~ng means ~not shown). A suitable gasket (not shown) is disposed between the flange 14 and wall 12 to pro~ide a ¦seal between the~e parts.
In the usual electrical apparatus in which this load-break fuse equipment is used, wall 12 is a portion of a tank filled with a dielectric fluid, such as oil. The recep~acle 10 constitutes a dry well projecting into this oil and having lits interior sealed from the oil.
The receptacle 10 is primarily formed as a cylindrical ins~lating tub,e 16 of oil-resistant, glass-fiber reinforced epoxy material that is suitably joined at its outboard end to flange 14. At the inboard end of insulating tube 16, there ~ ~91~6 5D5283 ¦is a cup~shaped metal terminal member 18 suitably attached to tube 16. This metal terminal member 18 carries the stationary socket-type contact 19 of a conventional load-break switch 19, 48 soon to be described. Terminal member 18 also has an external stud 21 to which an external con-ductor 23 can be attached for electrically connecting termi-nal member 18 to an external source circuit (not shown).
Receptacle 10 further comprises two conductive metal sleeves 20 and 22 within the insulating tube 16 at axially-s~aced l~cations along the bore of tube. As will soon appearmore clearly, these sleeves 20 and 22 serve as tubular con-tacts for the load-break drawout assembly that is remo~ably m~unted in the receptacle. Sleeve 20 is referred to herein as an outboard contact, and sleeve 22 as an inboard contact.
Electrically con~ected to sleeYes 20 and 22 are terminal studs 24 and 26, each of which pro~ects radially through the insulating tube 16 to its exterior.
Iit will be apparent that receptacle 10 comprises a -first tubular insulating portion 30 between the inboard and outboa~d contacts 20 and 22, a second tubular insulating portion 32 between outboard contact 20 and flange 14, and a third tubular insulating portion 34 between inboard contact 22 and metal terminal member 18 at its inner end that carries stationary load-break contact 19. When the load-break draw-out assembly ~soon to be described) is not in place withinthe receptacle, the first insulating portion 30 insulates contacts 20 and 22 from each other; the second insulating portion 32 insulates contact 20 from the metal wall 12; and the third insulating portion 34 insulates the inboard contact 22 from inner end terminal member 18.
~91~6 5D5283 Removably mounted within receptacle 10 is a load-break drawout assembly 40. This drawout assembly comprises a current-limiting fuse 42, two sliding contacts 44 and 46 at opposite ends of the fuse, a load-break movable contact rod 48, 49 in a location inboard of the fuse, and a drawout rod 50 of insulating material in a location outboard of the fuse. As will soon appear more clearly, these components 42-50 are all mechanically connected toge~her so that the drawout assembly 40 is removable from receptacle 10 as a unit and is insertab~e into receptacle 10 as a unit. When load-break drawout assembly 40 is fully inserted into its receptacle, as shown in Fig. I, an electric circuit extends jthrQugh the load-break fuse equipment~from its outboard Iterminal 24 to the terminal member 18 at its inner end via a path that extends in series through the contacts 20 and 44,1 fuse 42, and load-break switch 48, 19. The outboard terminal 24 is connected to a load circuit, e.g., the high voltage ¦winding (not shown) of the transformer, through a suitable conductor 51. The various components of the drawout assembly 40 will now be described in more detail.
Current--limiting fuse 42 is of a conventional design, and, as such,lcomprises a casing 54 of insulating material, end caps at opposite.ends of the casing having rod-type terminals 56 and 58, and fusible elements (not shown) dis-posed within casing 54 and electrically interconnectingterminals 56 and 58. Casing 54 contains an arc-extinguishing filler material, such as quartz sand, in which the fusible elements are embedded.
The drawout rod 50 has a cup-shaped metal end fitting 30 62 at its inboard end that snugly rec~ives the fuse terminal .
~ 91~ 6 5DS283 56. A plurality of set screws 63 extend radially through . end fitting 62 and clamp the end fitting and fuse terminal SÇ
together. The sliding contact 44 is attached to the end fitting 62 by suitable means providing a good electrical connection therebetween. In the illustrated embodiment, this sliding contact 42 is a disc of highly conductive~metal having at its outer periphery circumferentially-spaced fingers of U-shaped cross section that press radially outward against the sleeve contact 20. Other suitable forms of slid-ing contact may, of course, be used in this location. Whenthe terminal stud 24 is connected to an external circuit, current can flow from terminal.stud 24 to the fuse terminal 56 via a path that extends in series'throug,h sleeve contact 20, sliding contact 44, and end fitting 62.
The contact rod 48, 49 at the inboard end of fuse ~2 has an end fitting 70 that receives fuse terminal 58 and is cl,amped thereto by set screws in the same way as parts 62 and 56 are clamped together at the outboard end of the fuse.
The sliding contact 46 at the inboard end of the fuse is of essentially the same construction as previously-described sliding contact 44 and is suitably attached to end fitting 70. When terminal stud 26 is connected to an external circuit, current can flow between stud 26 and contact rod 48, 49 via a path extending through the following parts in series: 26, 22, 46, 70, and 48, 49.
Contact rod 48, 49 is slidably received within the bor~
of tulip-type stationary contact structure 19, which com-prises circumferentially-spaced fingers biased radially in-ward by suitable means (not shown) to provide increased contact pressure between contact 19 and 48. Contacts 19 and ~9~6 5D5283 48 may be thought of as load-break contacts since they are usually separated while load current is flowing through them when the drawout assembly 40 is withdrawn.
ll Current interruption at the load-break contacts is 5 ¦e~ected in a conventional manner. More specifically, an ¦-arc is drawn between contacts 19 and 48 when rod 48 is with-¦drawn from contact 19, and this arc reacts with gas-evolving material in this region to produce an arc-extinguishing gas that acts to quickly extinguish the arc. Such gas-evolving material is present in the form of a stationary snuffer tube 76 surrounding rod 46 and a follower 76 attached to contact rod 48.
The drawout assembly 40 further;includes a flange 80 at its outboard end that seats against the flange 14 of re-}5 ceptacle 10 when the drawout a8semb1y is fully inserted, as shown in Fig.-l. Flange 80 can be moved to the left by applying orce to an eye bolt 82 secured to the flange.
Such force is applied through a conventional hot-stick attached by an operator to eye bolt 80.
t~hen eye bolt 80 is thus pulled to the left, the entire load-break drawout assembly 40 is moved to the le~t and is eventually withdrawn from receptacle 10. Such withdrawal results, first of all, in the circuit through the device being interrupted at the load-break contacts 19 and 48, as above described. The sliding contacts 44 and 46 are then still in engagement with their associated contact sleeves 20 and 22 so that there is no arcing at these contacts. When ;
the drawout assembly 40 has been withdrawn sufficiently to complete the load-break operation and disconnect ~he circuit, the sliding contacts 44 and 46 separate from their associated ~91~6 5D5283 contacts 20 and 22, and the drawout assembly is then completely withdrawn.
When the drawout assembly 40 is in its fully inserted position of Fig. l, the current-limiting fuse 42 functions in a conventional manner to protect the transformer against short-circuit and other abnormal currents flowlng through the load-break fuse equipment. More specifically, if current through the fuse exceeds a predetermined value, portions of the fusible elements therein rapidly vaporize, creating arcs -lO~ that are rapidly extinguished and prevented from reigniting by the interaction of the arc and the filler material within the fuse. S,uch operation of the fuse acts in a conventional manner to limit the current therethro~gh toSa value far below , the maximum,a~ailable current of the circuit.
'15 In certain applications,-any single fuse (42) which will properly fit within the receptacle 10 may not have sufficient current-carrying capacity and/or sufficient current-interrupting capacity to ade~uately protect the transformer. To provide adequate protection for such appli-cations,,-we connect a separate fuse 142 in parallel with the above-described $use 42 and in series-with the contacts 48, lS
of the load-break switch.
This separate fuse 142 is part of a non-load-break drawout assembly 140 mounted in a receptacle llO located adjacent receptacle 10. Receptacle llO is in many respects similar in construction to receptacle 10, and most of its parts have therefore been assigned the same reference numerals as corresponding parts of receptacle 10 except for the addition of the prefix "l". Similarly, drawout assembly 140 is similar in many respects to drawout assembly 40, and most .
~ 91~6 ¦of its parts have been assigned the same reference numerals ¦as corresponding parts of drawout assembly 40 except for the ¦addition of the prefix "1". To avoid repetition, only the Idif~erences in the two side-by-side assemblies will be described.
:The non-load-break drawout assembly 140 differs from the load-break drawout assembly 40 in that it terminates at the end fitting (170) that receives the inboard fuse terminal (158). Thus, there is no load-break switch at the inboard end of the drawout assembly L40.
The receptacle 110 differs from receptacle 10 in that it terminates at its inboard end just past the inboard fuse terminal 158. An end cap 118 is suit;~bly attached to in-sulating tube 116 to provide a leak-proof end construction for the receptacle. -For electrically connecting the two fuses 42 and 142in parallel with each other:and in series with the load-breakl switch 19, 48, a pair of flexible conductors 200 and 202 are ¦
provided. Conductor 200 is connected between terminals 24 ,20 and 124 af the two receptacles, and conductor 202 is elec-tri¢ally connected between terminals 26 and 126 of the two receptacles. This parallel connection of the fuses enables the fuses to share the continuous current-carrying duty and also:the current-interrupting duty, thus enabling the pro-25 tective equipment to handle higher continuous and available ;
short-circuit currents.
When it is desired to disconnect the transformer wind-ing from the incoming conductor 23, the load-break drawout assembly 40 is withdrawn from its receptacle 10, thus break-ing the load current at the load-break switch 19, 48 and i~'~91~6 5D 5 2 8 3 isolating the load side lead 51 from incoming (or source) lead 23. Because the load-break switch 19, 48 is in series with both fuses 42 and 142, it is to be noted that the fuses remain in parallel during the load-breaking operation, and thus both are available during this interval to share in interrupting possible short-circuit or other abnormal currents. Similarly, if the load-break drawout assembly 40 is inserted while the fuse assem~ly 140 is in place within its receptacle, the parallel combination of fuses is avail-able to share the interrupting duty from the instant thatthe load-break switch 19, 48 reestablishes the power circuit.
The above operation is in distinct contrast to that present when two load-break fuse assémblies are provided and are connected completely in parallel, as in the prior art.
- 15 ~hen the drawout assembly of one of these fuse assemblies is removed, the remaining one carries all the current and its fuse may be called upon to interrupt possible short-currents alone and without assistance from the first fuse should a fault occur during this interval. Similarly, should one of these drawout assemblies be inserted prior to insertion of the other one, the first-inserted one may be called upon to handle possible short-circuit, or other abnormal, currents unassisted until the other one is inserted.
The load-break fuse assembly 10, 40 is structurally quite similar to a prior load-break fuse assembly manu-factured by the assignee of the present invention and can therefore be manufactured using most of the same parts as ith the prior load-break fuse assembly and without drastic-ally changing the manufacturing process. But, there is at least one important structural difference between the load-~ 91~`6 5D5283 I break fuse assembly 10, 40 and the prior load-break fuse assembly, and that resides in the presence of the inboard sliding contact 46 and the inboard sleeve con~act 22 and ¦terminal 26 at the inboard end of the fuse, which components are not present in the prior load-break fuse assembly.
Although the fuse 142 is connected in parallel with fuse 42 and in series with load-break switch 19, 48, it is to be noted that the load-break drawout assembly can be remo~ed and reinserted without interference from the extra lQ fuse 142 and in generally the same straightforward manner as previously.
It is important, however, that the two drawout fuse assemblies be withdrawn in the proper sequence and also re-inserted in the proper sequence. More specifically, it is important that the load-break drawout assembly 40 be with-drawn before the non-load-break drawout assembly 140 and be reinserted after the non-load-break assembly 140. Unless this sequence is followed, there will be an interval during each of these operations when only one fuse will be connected in the~circuit and will be available to interru~t possible short-c,rcuit curre~ts. To assure that the correct sequence is followed in t~ese operations, an interlock arrangement .-such as shown in Figs. 2 and 3 is provided.
This interlock arrangement comprises a barrier 210 that is mounted on the outside of wall 12 and is guided for move-ent in a vertical path only by suita~le pin and slot con- I
Inections, one of which is shown at 215, 216. When the draw- ¦
fUt assemblies are both in their fully-inserted position of ?ig. 1, the barrier 210 is in a position to block drawout notion of the lower, or non-load-break, drawout assembly 140.
- L-~9~6 5D5283 If an attempt is made to lift the barrier 210 to unblock the lower drawout assemb~y, such lifting of the barrier is block-ed by the flange 80 of the upper drawout assembly 40, which is in the path of a projection 220 on the barrier. Thus, the lower drawout asse~bly is prevented from being withdrawn -before the upper dxawout~assembly is withdrawn.
l~hen the upper drawout assembly is withdrawn, upward movement of the barrier 210 is no longer blocked by flange 80, and the barrier 210 can therefore be lifted to unblock the lower drawout assembly, thus permitting its withdrawal.
When barrier 210 is thus lifted into an unblocking position with respect to the lower drawout assembly 140, it is latched in its elevated position b~ a latch 225 cooperat-ing with a projection 227 on the barrier 210. This latch 225 is pivotally mounted on a ~tationary pivot 230 and is biased counterclockwise by a spring 232 against a generally stationary, but ~lightly yieldahle, stop 235. When the barrier 210 is lifted, the latch is temporarily brushed aside by proiection 227 but is pivoted counterclockwise into place underneath the projection 227 when the projection moves above the latch.
When the lower drawout assembly is withdrawn, the flange 180 will pivot latch 225 clockwise a short distance against yieldable stop 235 but-not enough to release latch 225 from projection 227. Thus, the barrier 210 remains in its ele-vated position of Fig. 3 when both drawout assemblies are withdrawn. When barrier 210 is in this position, it blocks insertion of the upper drawout assembly. It is necessary to first insert the lower dra~tout assembly. During such in-sertion, the outer periphery of flange 180 of the lower 9 1~ 6 SDS283 drawout assembly trips latch 225, allowing barrier ZlO tofall into place behind flange 180 on the lower drawout assembly. When flange 180 nears its fully-seated position, l the latch 225 is free to reset by pivoting counterclockwise into its position of Fig. 2.
It is to be understood that our invention in its boarder aspects is not limited to any particular form of interlock. But it is highly desirable that some means be provided for providing reasonable assurance that the desired sequence of operations will be followed both during withdraw-al-and during reinsertion of the drawout fuse assemblies.
Whi}e I have shown only a single phase form of the inuention, it is to be understood that the invention is readily usable for polyphase apparatùs. In such apparatus, an assembly corresponding to tpat shown in Fig. l is provided for each phase; and, preferably, a suitable interlock is provided which assures that all of the load-break drawout assemblies will be withdrawn before any of the non-load-break assemblies are withdrawn and also assures that all of the .;
non-ldad-break assemblies will be inserted before any of the load break assemblies -are inserted.
While we have shown and described particular embodimentc ;
of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made with-out departing from our invention in its broader aspects; andwe, therefore, intend herein to cover all such changes and modifications as fall within the true spirit and scope of our invention.
WF:d;
l prises a use and the mova~le contact of a load-b~eak switch.
5 ¦ Examples of load-break fuse equipment of this type are disclosed in U.S.-Patent 3,471,816-Giegerich; 3,628,092-Xeto;
and 4,0-59,816-Bonecutter et al. In certain~applications of such load-break fuse equipment, the largest diameter single fuse that is receivable within the receptacle may not have sufficient current-carryin~ or current-interrupting capacity for the power circuit in which the equipment is to-be con-~nected. ~For such high current applications, it is con-¦ventional to provide two identical load-break use-equipments 1f this type and to connect them electrically in parallel.
¦ While this approach can provide increased current-¦caxrying-and current-interrupting capacity while the two ¦load-break drawout assemblies are in place within their ¦receptacles, it is subject to the distinct disadvantage that ¦the desired current-interrupting capacity is not present ¦during certain inter~als while the load-break drawout assem- ¦
¦bl~es are being removed from or being inserted into-their ¦receptacles. More specifically, if one of the load-break ¦drawout assemblies of such prior e~uipment is withdrawn, the ¦fuse of the xemaining assembly must alone provide current ¦interrupting ability until the remaining assembly is with-¦drawn. This same condition is, of course, present if one ¦of the load-break drawout assemblies is inserted before the ¦other one.
- ¦¦ 5D5283 91~6 Summary ¦ An object of this invention is to provide load-break fuse equipment of this general type that comprises fuses connected in parallel, which fuses remain connected in parallel both during removal and insertion of the load-break -5~ drawQ.ut assembly.
AnQther object is to provide load-break fuse equipment comprising~a tu~ular receptacle and a load-break drawout assembly removably moun~ed therein, which equipment is con-strncted in such-a way that a separate fuse can readily be 10~ connected in parallel with the fuse of the .drawout assembly and.in series with the load-break.switch within the recepta-. cle,.all without interfering wi.th the~easy removability ofthe drawout assembly and the ability of the load-break switch : to interrupt load currents coincident with removal of drawout .15 assembly.
. Anothex object is to achieve the immediately-preceding :. obj.ect without interfering with easy insertability of the .dxawout assembly and the ability of the load-break switch to . close against currents coincident with such insertion, e.g., .20 ~ inrush currents.
: In carrying out the invention in one form, we provide . two spaced-apar~ tubular receptacles mounted on a wall. Each recep~acle comprises an outboard contact and an inboard con-¦tact at axially-spaced locations along the bore of the recep-tacle,~first tubular.insulating structure between said con-tacts, and second tubular insulating structure between the outboard contact and.said wall. One of the receptacles further compri.ses a generally stationary load-break contact at its inner end and a third tubular insulating portion - ~91~6 5D5283 between said load-break contact and its inboard contact.
Insertable as a unit into said one receptacle is a load-break drawout assembly comprising a fuse, two sliding contacts at opposite ends of the fuse, a movable load-break contact inboard of the fuse, and an insulating drawou~ rod outboard of the fuse. When this drawout assembly is f~lly inserted, the movable load-break contact engages the station-ary load-break contact and the two sliding contacts respectiv, 3-ly engage the inboard and outboard contacts of said one re-ceptacle. Insertable as a unit into the other receptacle isa non-load-break drawout assembly comprising a fuse, two sliding contacts at opposite ends of the fuse, and an insu-lating drawout rod outboard of the fuse; said two sliding contacts respectively engaging the inboard and outboard con-lS tacts of said other receptacle-when said non-load-break drawout assembly is fully inserted.
Means is provided for electrically connecting said two-fuses in parallel with each other and in series with said load-break contacts comprising a first conductor interconnect ing th~e outboard contacts of the two receptacles and a second conductor interconnecting the inboard contacts of the two receptacles.
Brief DescriPtion of Drawinqs For a better understanding of the invention, reference may be had to the following description taken in conjunction ith the accompanying drawings, wherein:
Fig. 1 is a side elevational view, mostly in section, showing load-break fuse equiDment embodying one form of the invention.
`- ll i~ 9 ~ 6 5D5283 Fig. 2 is a sectional view of an interlock used with ¦the fuse equipment of Fig. 1 for ensuring a predetermined se~uence of operations during withdrawal and insertion of the drawout fuse assemblies. Fig. 2 depicts both *rawout assembli~s in their fully inserted positions.
Fig. 3 is another view of the interlock of Fig. 2 ¦showing the interlock with the drawout fuse assemblies re-mo~ed.
Detailed DescriPtion of Preferred Embodiment Referring now to Fig' 1, the illustrated load-break fuse-equipment comprises a tubular receptacle 10 that is mounted on a wall 12 of electrical apparatus such as a pad-mounted-distribution transformer. The wall 12, which may be f metal, contains an opening through which the tubular re-ceptacle 10 extends r with the bore of the receptacle general-ly aligned with the opening. A flange 14 on the outer end of the receptac~e 10 is attached to the wall 12 by suitable fasteni~ng means ~not shown). A suitable gasket (not shown) is disposed between the flange 14 and wall 12 to pro~ide a ¦seal between the~e parts.
In the usual electrical apparatus in which this load-break fuse equipment is used, wall 12 is a portion of a tank filled with a dielectric fluid, such as oil. The recep~acle 10 constitutes a dry well projecting into this oil and having lits interior sealed from the oil.
The receptacle 10 is primarily formed as a cylindrical ins~lating tub,e 16 of oil-resistant, glass-fiber reinforced epoxy material that is suitably joined at its outboard end to flange 14. At the inboard end of insulating tube 16, there ~ ~91~6 5D5283 ¦is a cup~shaped metal terminal member 18 suitably attached to tube 16. This metal terminal member 18 carries the stationary socket-type contact 19 of a conventional load-break switch 19, 48 soon to be described. Terminal member 18 also has an external stud 21 to which an external con-ductor 23 can be attached for electrically connecting termi-nal member 18 to an external source circuit (not shown).
Receptacle 10 further comprises two conductive metal sleeves 20 and 22 within the insulating tube 16 at axially-s~aced l~cations along the bore of tube. As will soon appearmore clearly, these sleeves 20 and 22 serve as tubular con-tacts for the load-break drawout assembly that is remo~ably m~unted in the receptacle. Sleeve 20 is referred to herein as an outboard contact, and sleeve 22 as an inboard contact.
Electrically con~ected to sleeYes 20 and 22 are terminal studs 24 and 26, each of which pro~ects radially through the insulating tube 16 to its exterior.
Iit will be apparent that receptacle 10 comprises a -first tubular insulating portion 30 between the inboard and outboa~d contacts 20 and 22, a second tubular insulating portion 32 between outboard contact 20 and flange 14, and a third tubular insulating portion 34 between inboard contact 22 and metal terminal member 18 at its inner end that carries stationary load-break contact 19. When the load-break draw-out assembly ~soon to be described) is not in place withinthe receptacle, the first insulating portion 30 insulates contacts 20 and 22 from each other; the second insulating portion 32 insulates contact 20 from the metal wall 12; and the third insulating portion 34 insulates the inboard contact 22 from inner end terminal member 18.
~91~6 5D5283 Removably mounted within receptacle 10 is a load-break drawout assembly 40. This drawout assembly comprises a current-limiting fuse 42, two sliding contacts 44 and 46 at opposite ends of the fuse, a load-break movable contact rod 48, 49 in a location inboard of the fuse, and a drawout rod 50 of insulating material in a location outboard of the fuse. As will soon appear more clearly, these components 42-50 are all mechanically connected toge~her so that the drawout assembly 40 is removable from receptacle 10 as a unit and is insertab~e into receptacle 10 as a unit. When load-break drawout assembly 40 is fully inserted into its receptacle, as shown in Fig. I, an electric circuit extends jthrQugh the load-break fuse equipment~from its outboard Iterminal 24 to the terminal member 18 at its inner end via a path that extends in series through the contacts 20 and 44,1 fuse 42, and load-break switch 48, 19. The outboard terminal 24 is connected to a load circuit, e.g., the high voltage ¦winding (not shown) of the transformer, through a suitable conductor 51. The various components of the drawout assembly 40 will now be described in more detail.
Current--limiting fuse 42 is of a conventional design, and, as such,lcomprises a casing 54 of insulating material, end caps at opposite.ends of the casing having rod-type terminals 56 and 58, and fusible elements (not shown) dis-posed within casing 54 and electrically interconnectingterminals 56 and 58. Casing 54 contains an arc-extinguishing filler material, such as quartz sand, in which the fusible elements are embedded.
The drawout rod 50 has a cup-shaped metal end fitting 30 62 at its inboard end that snugly rec~ives the fuse terminal .
~ 91~ 6 5DS283 56. A plurality of set screws 63 extend radially through . end fitting 62 and clamp the end fitting and fuse terminal SÇ
together. The sliding contact 44 is attached to the end fitting 62 by suitable means providing a good electrical connection therebetween. In the illustrated embodiment, this sliding contact 42 is a disc of highly conductive~metal having at its outer periphery circumferentially-spaced fingers of U-shaped cross section that press radially outward against the sleeve contact 20. Other suitable forms of slid-ing contact may, of course, be used in this location. Whenthe terminal stud 24 is connected to an external circuit, current can flow from terminal.stud 24 to the fuse terminal 56 via a path that extends in series'throug,h sleeve contact 20, sliding contact 44, and end fitting 62.
The contact rod 48, 49 at the inboard end of fuse ~2 has an end fitting 70 that receives fuse terminal 58 and is cl,amped thereto by set screws in the same way as parts 62 and 56 are clamped together at the outboard end of the fuse.
The sliding contact 46 at the inboard end of the fuse is of essentially the same construction as previously-described sliding contact 44 and is suitably attached to end fitting 70. When terminal stud 26 is connected to an external circuit, current can flow between stud 26 and contact rod 48, 49 via a path extending through the following parts in series: 26, 22, 46, 70, and 48, 49.
Contact rod 48, 49 is slidably received within the bor~
of tulip-type stationary contact structure 19, which com-prises circumferentially-spaced fingers biased radially in-ward by suitable means (not shown) to provide increased contact pressure between contact 19 and 48. Contacts 19 and ~9~6 5D5283 48 may be thought of as load-break contacts since they are usually separated while load current is flowing through them when the drawout assembly 40 is withdrawn.
ll Current interruption at the load-break contacts is 5 ¦e~ected in a conventional manner. More specifically, an ¦-arc is drawn between contacts 19 and 48 when rod 48 is with-¦drawn from contact 19, and this arc reacts with gas-evolving material in this region to produce an arc-extinguishing gas that acts to quickly extinguish the arc. Such gas-evolving material is present in the form of a stationary snuffer tube 76 surrounding rod 46 and a follower 76 attached to contact rod 48.
The drawout assembly 40 further;includes a flange 80 at its outboard end that seats against the flange 14 of re-}5 ceptacle 10 when the drawout a8semb1y is fully inserted, as shown in Fig.-l. Flange 80 can be moved to the left by applying orce to an eye bolt 82 secured to the flange.
Such force is applied through a conventional hot-stick attached by an operator to eye bolt 80.
t~hen eye bolt 80 is thus pulled to the left, the entire load-break drawout assembly 40 is moved to the le~t and is eventually withdrawn from receptacle 10. Such withdrawal results, first of all, in the circuit through the device being interrupted at the load-break contacts 19 and 48, as above described. The sliding contacts 44 and 46 are then still in engagement with their associated contact sleeves 20 and 22 so that there is no arcing at these contacts. When ;
the drawout assembly 40 has been withdrawn sufficiently to complete the load-break operation and disconnect ~he circuit, the sliding contacts 44 and 46 separate from their associated ~91~6 5D5283 contacts 20 and 22, and the drawout assembly is then completely withdrawn.
When the drawout assembly 40 is in its fully inserted position of Fig. l, the current-limiting fuse 42 functions in a conventional manner to protect the transformer against short-circuit and other abnormal currents flowlng through the load-break fuse equipment. More specifically, if current through the fuse exceeds a predetermined value, portions of the fusible elements therein rapidly vaporize, creating arcs -lO~ that are rapidly extinguished and prevented from reigniting by the interaction of the arc and the filler material within the fuse. S,uch operation of the fuse acts in a conventional manner to limit the current therethro~gh toSa value far below , the maximum,a~ailable current of the circuit.
'15 In certain applications,-any single fuse (42) which will properly fit within the receptacle 10 may not have sufficient current-carrying capacity and/or sufficient current-interrupting capacity to ade~uately protect the transformer. To provide adequate protection for such appli-cations,,-we connect a separate fuse 142 in parallel with the above-described $use 42 and in series-with the contacts 48, lS
of the load-break switch.
This separate fuse 142 is part of a non-load-break drawout assembly 140 mounted in a receptacle llO located adjacent receptacle 10. Receptacle llO is in many respects similar in construction to receptacle 10, and most of its parts have therefore been assigned the same reference numerals as corresponding parts of receptacle 10 except for the addition of the prefix "l". Similarly, drawout assembly 140 is similar in many respects to drawout assembly 40, and most .
~ 91~6 ¦of its parts have been assigned the same reference numerals ¦as corresponding parts of drawout assembly 40 except for the ¦addition of the prefix "1". To avoid repetition, only the Idif~erences in the two side-by-side assemblies will be described.
:The non-load-break drawout assembly 140 differs from the load-break drawout assembly 40 in that it terminates at the end fitting (170) that receives the inboard fuse terminal (158). Thus, there is no load-break switch at the inboard end of the drawout assembly L40.
The receptacle 110 differs from receptacle 10 in that it terminates at its inboard end just past the inboard fuse terminal 158. An end cap 118 is suit;~bly attached to in-sulating tube 116 to provide a leak-proof end construction for the receptacle. -For electrically connecting the two fuses 42 and 142in parallel with each other:and in series with the load-breakl switch 19, 48, a pair of flexible conductors 200 and 202 are ¦
provided. Conductor 200 is connected between terminals 24 ,20 and 124 af the two receptacles, and conductor 202 is elec-tri¢ally connected between terminals 26 and 126 of the two receptacles. This parallel connection of the fuses enables the fuses to share the continuous current-carrying duty and also:the current-interrupting duty, thus enabling the pro-25 tective equipment to handle higher continuous and available ;
short-circuit currents.
When it is desired to disconnect the transformer wind-ing from the incoming conductor 23, the load-break drawout assembly 40 is withdrawn from its receptacle 10, thus break-ing the load current at the load-break switch 19, 48 and i~'~91~6 5D 5 2 8 3 isolating the load side lead 51 from incoming (or source) lead 23. Because the load-break switch 19, 48 is in series with both fuses 42 and 142, it is to be noted that the fuses remain in parallel during the load-breaking operation, and thus both are available during this interval to share in interrupting possible short-circuit or other abnormal currents. Similarly, if the load-break drawout assembly 40 is inserted while the fuse assem~ly 140 is in place within its receptacle, the parallel combination of fuses is avail-able to share the interrupting duty from the instant thatthe load-break switch 19, 48 reestablishes the power circuit.
The above operation is in distinct contrast to that present when two load-break fuse assémblies are provided and are connected completely in parallel, as in the prior art.
- 15 ~hen the drawout assembly of one of these fuse assemblies is removed, the remaining one carries all the current and its fuse may be called upon to interrupt possible short-currents alone and without assistance from the first fuse should a fault occur during this interval. Similarly, should one of these drawout assemblies be inserted prior to insertion of the other one, the first-inserted one may be called upon to handle possible short-circuit, or other abnormal, currents unassisted until the other one is inserted.
The load-break fuse assembly 10, 40 is structurally quite similar to a prior load-break fuse assembly manu-factured by the assignee of the present invention and can therefore be manufactured using most of the same parts as ith the prior load-break fuse assembly and without drastic-ally changing the manufacturing process. But, there is at least one important structural difference between the load-~ 91~`6 5D5283 I break fuse assembly 10, 40 and the prior load-break fuse assembly, and that resides in the presence of the inboard sliding contact 46 and the inboard sleeve con~act 22 and ¦terminal 26 at the inboard end of the fuse, which components are not present in the prior load-break fuse assembly.
Although the fuse 142 is connected in parallel with fuse 42 and in series with load-break switch 19, 48, it is to be noted that the load-break drawout assembly can be remo~ed and reinserted without interference from the extra lQ fuse 142 and in generally the same straightforward manner as previously.
It is important, however, that the two drawout fuse assemblies be withdrawn in the proper sequence and also re-inserted in the proper sequence. More specifically, it is important that the load-break drawout assembly 40 be with-drawn before the non-load-break drawout assembly 140 and be reinserted after the non-load-break assembly 140. Unless this sequence is followed, there will be an interval during each of these operations when only one fuse will be connected in the~circuit and will be available to interru~t possible short-c,rcuit curre~ts. To assure that the correct sequence is followed in t~ese operations, an interlock arrangement .-such as shown in Figs. 2 and 3 is provided.
This interlock arrangement comprises a barrier 210 that is mounted on the outside of wall 12 and is guided for move-ent in a vertical path only by suita~le pin and slot con- I
Inections, one of which is shown at 215, 216. When the draw- ¦
fUt assemblies are both in their fully-inserted position of ?ig. 1, the barrier 210 is in a position to block drawout notion of the lower, or non-load-break, drawout assembly 140.
- L-~9~6 5D5283 If an attempt is made to lift the barrier 210 to unblock the lower drawout assemb~y, such lifting of the barrier is block-ed by the flange 80 of the upper drawout assembly 40, which is in the path of a projection 220 on the barrier. Thus, the lower drawout asse~bly is prevented from being withdrawn -before the upper dxawout~assembly is withdrawn.
l~hen the upper drawout assembly is withdrawn, upward movement of the barrier 210 is no longer blocked by flange 80, and the barrier 210 can therefore be lifted to unblock the lower drawout assembly, thus permitting its withdrawal.
When barrier 210 is thus lifted into an unblocking position with respect to the lower drawout assembly 140, it is latched in its elevated position b~ a latch 225 cooperat-ing with a projection 227 on the barrier 210. This latch 225 is pivotally mounted on a ~tationary pivot 230 and is biased counterclockwise by a spring 232 against a generally stationary, but ~lightly yieldahle, stop 235. When the barrier 210 is lifted, the latch is temporarily brushed aside by proiection 227 but is pivoted counterclockwise into place underneath the projection 227 when the projection moves above the latch.
When the lower drawout assembly is withdrawn, the flange 180 will pivot latch 225 clockwise a short distance against yieldable stop 235 but-not enough to release latch 225 from projection 227. Thus, the barrier 210 remains in its ele-vated position of Fig. 3 when both drawout assemblies are withdrawn. When barrier 210 is in this position, it blocks insertion of the upper drawout assembly. It is necessary to first insert the lower dra~tout assembly. During such in-sertion, the outer periphery of flange 180 of the lower 9 1~ 6 SDS283 drawout assembly trips latch 225, allowing barrier ZlO tofall into place behind flange 180 on the lower drawout assembly. When flange 180 nears its fully-seated position, l the latch 225 is free to reset by pivoting counterclockwise into its position of Fig. 2.
It is to be understood that our invention in its boarder aspects is not limited to any particular form of interlock. But it is highly desirable that some means be provided for providing reasonable assurance that the desired sequence of operations will be followed both during withdraw-al-and during reinsertion of the drawout fuse assemblies.
Whi}e I have shown only a single phase form of the inuention, it is to be understood that the invention is readily usable for polyphase apparatùs. In such apparatus, an assembly corresponding to tpat shown in Fig. l is provided for each phase; and, preferably, a suitable interlock is provided which assures that all of the load-break drawout assemblies will be withdrawn before any of the non-load-break assemblies are withdrawn and also assures that all of the .;
non-ldad-break assemblies will be inserted before any of the load break assemblies -are inserted.
While we have shown and described particular embodimentc ;
of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made with-out departing from our invention in its broader aspects; andwe, therefore, intend herein to cover all such changes and modifications as fall within the true spirit and scope of our invention.
WF:d;
Claims (7)
1) In combination, a) a wall having two spaced-apart openings, b) two tubular receptacles having bores respectively generally aligned with said openings and each having one end secured to said wall and its opposite end spaced from the wall, c) each receptacle comprising: an outboard contact and an inborad contact at axially-spaced locations along the bore of said receptacle, first tubular insulating structure insulating said contacts of a receptacle from each other when the receptacle is empty, and second tubular insulating structure insulating the outbaord contact of a receptacle from said wall, d) one of said receptacles further comprising a third tubular insulating portion located axially inwardly of the inboard contact of said one receptacle, e) a generally stationary load-break contact at said opposite end of said one receptacle and insulated from said inboard contact by said third tubular insulating portion when said one receptacle is empty, f) a load-break drawout assembly, insertable as a unit into said one receptacle and also removable as a unit therefrom, comprising: an electric fuse, two sliding contacts at opposite ends of the fuse, a movable load-break contact inboard of said fuse, and an insulating drawout rod at the outboard end of said fuse; said movable load-break contact engaging such stationary load-break contact, and said two sliding contacts respectively engaging said inboard and outboard contacts of said one receptacle when said drawout assembly is fully inserted, g) a non-load-break drawout assembly insertable into-said other receptacle as a unit and also removable therefrom as a unit comprising: an electric fuse, two sliding contacts at opposite ends of the fuse, and an in-sulating drawout rod at the outboard end of said fuse; said two sliding contacts respectively engaging said inboard and outboard contacts of said other receptacle when said non-load-break drawout assembly is fully inserted, h) and means for electrically connecting said two fuses in parallel with each other and in series with said load-break contacts comprising a first conductor intercon-necting the outboard contacts of the two receptacles and a second conductor interconnecting the inboard contacts of the two receptacles.
2. The apparatus of claim 1 in which said fuses remain connected in parallel while said load-break contacts are being separated.
3. The apparatus of claim 1 in combination with inter lock means preventing withdrawal of said non-load-break drawout assembly from its receptacle before said load-break drawout assembly is withdrawn from its receptacle.
4. The apparatus of claim 1 in combination with inter-lock means preventing insertion of said load-break drawout assembly into its receptacle before said non-load-break drawout assembly is inserted into its receptacle.
5. The apparatus of claim 3 in combination with interlock means preventing insertion of said load-break drawout assembly into its receptacle before said non-load-break drawout assembly is inserted into its receptacle.
6. The apparatus of claim 1 in which:
a) said inboard and outboard contacts of said one receptacle are conductive sleeves surrounding said bore of the associated receptacle, and b) the sliding contacts of the load-break drawout assembly respectively engage said sleeves when the load-break drawout assembly is near its fully-inserted position.
a) said inboard and outboard contacts of said one receptacle are conductive sleeves surrounding said bore of the associated receptacle, and b) the sliding contacts of the load-break drawout assembly respectively engage said sleeves when the load-break drawout assembly is near its fully-inserted position.
7. The apparatus of claim 1 in which the two sliding contacts of the load-break drawout assembly remain in contact with the inboard and outboard contacts of said one receptacle during withdrawal of said load-break drawout assembly until interruption is completed at said load-break contacts.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA330,884A CA1109106A (en) | 1979-06-29 | 1979-06-29 | Load-break fuse equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA330,884A CA1109106A (en) | 1979-06-29 | 1979-06-29 | Load-break fuse equipment |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1109106A true CA1109106A (en) | 1981-09-15 |
Family
ID=4114583
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA330,884A Expired CA1109106A (en) | 1979-06-29 | 1979-06-29 | Load-break fuse equipment |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1109106A (en) |
-
1979
- 1979-06-29 CA CA330,884A patent/CA1109106A/en not_active Expired
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