Abstract:
A multiple operation cutout and a method of operating the same and providing multiple fuse operation provides an assembly for a plurality of fuses. A mechanism individually and sequentially engages the fuses responsive to operation of the fuses.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. Provisional Patent Application No. 61/325,440 filed Apr. 19, 2010 for all purposes and the disclosure of which is hereby expressly incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This patent relates to electricity distribution protection systems and in particular to multi-operation fuse cutout. 
         [0003]    A fuse cutout is a structure that allows insertion of a fuse assembly that provides protection for an electricity distribution circuit. The fuse assembly includes a hollow insulating fuse tube having conductive ferrules mounted to the opposite ends thereof. One ferrule (often called the “exhaust” ferrule) is located at an exhaust end of the fuse tube and usually includes a trunnion that engages with a trunnion pocket or hinge of a first contact assembly carried by one end of an insulator. The other ferrule is normally held and latched by a second contact assembly carried by the other end of the insulator so that the fuse tube is normally retained in spaced relationship to the insulator. The insulator is mountable to the cross-arm of a utility pole or a similar structure. A fuse link is located within the fuse tube with its ends respectively electrically continuous with the ferrules. One point of an electrical circuit is connected to the first contact assembly, while another point of the circuit is connected to the second contact assembly. Often, the insulator and the fuse tube are oriented generally perpendicular to the ground so that the exhaust ferrule and the first contact assembly are located below the other ferrule and the second contact assembly. The fuse tube may include a high burst strength outer portion—for example, a fiber-glass-epoxy composite having an arc-extinguishing material within the inner portions thereof. Normal currents flowing through the electrical circuit flow without affecting the fuse link. Should a fault current or other over current, to which the fuse link is designed to respond, occur in the circuit, the fuse link operates. 
         [0004]    Operation of the fuse link permits the upper ferrule to disengage itself from the upper contact assembly, whereupon the fuse tube rotates downwardly due to action of the trunnion and the hinge. If the fuse link operates properly, current in the circuit is interrupted and the rotation of the fuse tube gives a visual indication that the cutout has operated to protect the circuit, e.g. dropout operation to a so-called dropout position. Typical fuse links include a first terminal and a second terminal, between which there is normally connected a fusible element made of silver, silver-alloys, or the like. Also connected between the terminals may be a strain wire, for a purpose described below. The second terminal is electrically continuous with, and is usually mechanically connected to, a button assembly, which is engagable by a portion of the upper ferrule on the fuse tube. The first terminal is connected to a flexible, stranded length of cable. Surrounding at least a portion of the second terminal, the fusible element, the strain wire (if used), the first terminal, and some portion of the flexible stranded cable is a sheath. The sheath is typically made of a so-called ablative arc-extinguishing material which, when exposed to the heat of a high-voltage arc, ablate to rapidly evolve large quantities of deionizing turbulent and cooling gases. Typically, the sheath is much shorter than the fuse tube and terminates short of the exhaust end of the fuse tube. 
         [0005]    The free end of the stranded cable exits the fuse tube from the exhaust end thereof and has tension or pulling force maintained thereon by a spring-loaded flipper on the trunnion. The tension or pulling force exerted on the cable by the flipper attempts to pull the cable and the first terminal out of the sheath and out of the fuse tube. The force of the flipper is normally restrained by the strain wire, typical fusible elements not having sufficient mechanical strength to resist this tension or pulling force. 
         [0006]    In the operation of typical cutouts, a fault current or other over-current results, first, in the melting or vaporization of the fusible element, followed by the melting or vaporization of the strain wire. Following such melting or vaporization, a high-voltage arc is established between the first and second terminals within the sheath and the flipper is now free to pull the cable and the first terminal out of the sheath and, ultimately, out of the fuse tube. As the arc forms, the arc-extinguishing materials of the sheath begin to ablate and high quantities of de-ionizing, turbulent and cooling gases are evolved. The movement of the first terminal under the action of the flipper, and the subsequent rapid movement thereof due to the evolved gases acting thereon as on a piston, results in elongation of the arc. The presence of the de-ionizing, turbulent and cooling gas, plus arc elongation, may, depending on the level of the fault current or other over-current, ultimately result in extinction of the arc and interruption of the current at a subsequent current zero. The loss of the tension on the stranded cable permits the trunnion to experience some initial movement relative to the exhaust ferrule permitting the upper ferrule to disengage itself from the upper contact assembly. This initiates a downward rotation of the fuse tube and its upper ferrule to a so-called “dropout” or “dropdown” position. 
         [0007]    As noted above, arc elongation within the sheath and the action of the evolved gases may extinguish the arc. At very high fault current or over-current levels, however, arc elongation and the sheath may not, by themselves, be sufficient to achieve this end. Simply stated, at very high fault current levels, either the sheath may burst (because of the very high pressure of the evolved gas) or insufficient gas may be evolved there from to quench the high current level arc. For these reasons, the fuse tube is made of, or is lined with, ablative arc-extinguishing material. In the event the sheath bursts, the arc-extinguishing material of the fuse tube interacts with the arc, with gas evolved as a result thereof achieving arc extinction. If the sheath does not burst, the arc-extinguishing material of the fuse tube between the end of the sheath and the exhaust end of the fuse tube is nevertheless available for evolving gas, in addition to that evolved from the sheath. The joint action of the two quantities of evolved gas, together with arc elongation, extinguish the arc. 
         [0008]    When a fuse tube is properly positioned between the upper and lower contact assemblies of the mounting, the contacts of the fuse tube are firmly engaged within the contact assemblies of the mounting. When the fuse link operates, gases evolved within the fuse tube thrust it against the upper contact assembly of the mounting. Ideally, the contact cap should not disengage the concavity until the fusible elements of the fuse link completely melts to release the tension in the cable and until the initial thrust of the fuse tube subsides. Release of this tension and subsiding of fuse tube thrust permits a limited amount of relative movement between the exhaust ferrule and the trunnion about a toggle joint there between. This limited movement permits the contact cap to move out of the concavity and the fuse tube to begin movement toward the dropout position due to rotation of the trunnion in the hinge pocket. If the fuse tube moves too far transversely during its thrusting, the contact cap may disengage the concavity too early. Third, transverse movement of the fuse tube can apply a bending movement thereon. This bending movement can fracture the fuse tube near the exhaust ferrule. Corrosion that builds up on various parts and dimensional changes of the fuse tube or fuse link sheath, e.g. due to environmental factors, can exacerbate the proper dropout action. 
         [0009]    Thus, it is important for achieving proper operation as explained above that dropout operation be readily achieved in spite of any deleterious operating environments or conditions. 
         [0010]    Cutouts of the type described provide a single operation before requiring service to replace the fuse link within the fuse assembly and to reinsert the fuse assembly into the cutout. Service requires dispatching a technician to the location of the cutout, which may require significant time and expense. While the cause of the fault or over current may be transient and is in many instances, the service interruption as a result of operation of the fuse link can be protracted because of the need to service the fuse assembly. 
         [0011]    One device that overcomes the deficiency of single operation fuse cutouts is the TripSaver® dropout recloser available from S&amp;C Electric Company, Chicago, Ill., United States of America. The TripSaver dropout recloser incorporates a vacuum interrupter and operating mechanism capable of multiple operations before requiring service by a technician and controls to provide for automated operation. In response to a fault or over current, the TripSaver dropout recloser operates to isolate the fault and the recloses after operation to restore service. If the fault is transient, the device remains closed and service is restored without intervention by a service technician. If the fault is persistent, after a defined number of operations, the TripSaver drops out of the cutout, similar to the fuse assembly. A complete discussion of the design and operation of the TripSaver dropout recloser may be found in U.S. patent application Ser. No. 12/095,067 filed Jul. 16, 2008, the disclosure of which is expressly incorporated herein by reference. 
         [0012]    Other attempts to provide multi-operation cutouts have included tying together two or more single cutouts. Upon operation of a fuse assembly of one of the cutouts, current is transferred to a second cutout. However, these structures have necessarily included multiple insulators, multiple moving contacts, complicated reset structures and open contract transfer operations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a bottom perspective view of a multi-operation cutout in accordance with a herein described embodiment of the invention. 
           [0014]      FIG. 2  is a top perspective view of the multi-operation cutout depicted in  FIG. 1 . 
           [0015]      FIG. 3  is a front view of the multi-operation cutout depicted in  FIG. 1  in a first operating state. 
           [0016]      FIG. 4  is a bottom view of a contact mechanism in an operating position corresponding to the first operating state. 
           [0017]      FIG. 5  is a front view of the multi-operation cutout depicted in  FIG. 1  in a second operating state. 
           [0018]      FIG. 6  is a front view of the multi-operation cutout depicted in  FIG. 1  in a third operating state. 
           [0019]      FIG. 7  is a front view of the multi-operation cutout depicted in  FIG. 1  in a fourth operating state. 
           [0020]      FIG. 8  is a perspective view of a hinge support of the contact mechanism in accordance with a preferred embodiment of the invention. 
           [0021]      FIG. 9  is a side view of a housing member of the contact mechanism in accordance with a preferred embodiment of the invention. 
           [0022]      FIG. 10  is a side view of a moving contact assembly of the contact mechanism in accordance with a preferred embodiment of the invention. 
           [0023]      FIG. 11  is a side view of a trigger mechanism of the contact mechanism in accordance with a preferred embodiment of the invention. 
           [0024]      FIG. 12  is a side view of a contact assembly of the contact mechanism in accordance with a preferred embodiment of the invention. 
           [0025]      FIG. 13  is a side view of a spring member of the contact mechanism in accordance with a preferred embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]      FIG. 1  depicts a multi-operation cutout  100 . The cutout  100  is configured having three fuse assemblies  102  and is referred to herein as a three-shot cutout. Of course the cutout  100  may be configured to have two or more fuse assemblies  102 , and the three-shot cutout  100  is shown as an illustrative example. 
         [0027]    Except as described the fuse assemblies  102  are typical and include a fuse tube  104 , a first terminal  106  that includes a grappler ring  108 , a second terminal  110  that includes a trunnion  112  for fitting into a hinge  114 . Corresponding in number with the fuse assemblies  102 , the cutout  100  includes a plurality of fuse assembly mountings  116 , which except as described are typical. Each mounting  116  includes an upper mounting assembly  118  and a lower mounting assembly  120  including hinge  114 . The upper mounting assemblies  118  secure to a support bracket  122  having an as-shown arcuate shape but which may have any suitable shape that is secured to an upper portion of an insulator assembly  124 . A secondary support bracket  126  is shown, and is optional, suitably secured to the upper mounting assemblies  118  at flanges  130 . While identical in construction, the fuses  102  are identified as fuses  102   a,    102   b  and  102   c  to facilitate description of the operating sequence. 
         [0028]    Each upper mounting assembly  118  are part of a contact assembly  119  and includes a contact member  132  held against a respective first terminal  106  of a fuse assembly  102  by a spring  134 . The contact member  132  secures to and is electrically coupled with the support bracket  122 . As is typical of upper mounting assemblies, the upper mounting assembly  118  also includes a support member  136  including fuse guides  138 . 
         [0029]    Each lower mounting assembly  120  is generally similar in structure, for example, each includes hinge  114 ; however, each also has one or more structural and functional differences. Therefore, the three lower mounting assemblies  120  are respectively designated  120   a,    120   b  and  120   c.  Each hinge  114  is secured by a bracket member  142  to a hinge support  144  secured to a lower portion of the insulator assembly  124 . The trunnion  112  of a corresponding fuse assembly  102  is received in the hinge  114  allowing the fuse assembly  102  to pivot about the trunnion  112  within the hinge  114 . 
         [0030]    The lower mounting assembly  120   a  includes a bracket  150   a  secured to the hinge  114 . The bracket  150   a  includes a portion  151  for electrically coupling a conductor to the cutout  100 . The bracket  150   a  further supports and guides a trigger mechanism  152  that extends into a housing assembly  154  secured to the hinge support  144  (also seen in  FIG. 8 ). The trigger mechanism  152  is engaged by the fuse assembly  102  as it drops out and rotates in the hinge  114  in response to clearing a fault current. A cam surface  156  is formed one the second terminal  110  that engages a rocker cam  158  of the trigger mechanism, which pivots translating a latching bar  160 . The trigger mechanism  152  couples to and releases a moving contact assembly disposed within the housing assembly  154 . That is, the latching bars  160  extend into the housing  154  and engage the moving contact assembly internal to the housing  154  and predetermined locations. As best seen in  FIG. 4 , each trigger mechanism  152  includes a spring  163  that biases the latching bar  160  such that it extends through an aperture  161  ( FIG. 12 ) into the housing assembly  154  and is partially withdrawn by engagement of the cam surface  156  with the rocker cam  158 . 
         [0031]    The lower mounting assembly  120   b  includes a bracket  150   b,  which is similar to the bracket  150   a;  however, does not include the portion  151 . The lower mounting assembly  120   c  does not include a bracket  150   a  or  150   b  as the final operating fuse assembly  102  of the cutout  100  is not required to actuate a trigger mechanism. Therefore, no trigger mechanism is provided for the last for the last fuse assembly of the cutout  100 . Of course, the lower mounting assemblies  120  and/or brackets  150  may all be the same to simplify manufacturing or for other reasons. 
         [0032]    A second conductor terminal  170  extends from a central portion of the insulator assembly  124 . Additionally, extending from the housing assembly  154  is a reset ring  172  that couples to the moving contact assembly disposed within the housing assembly  154 . 
         [0033]    Referring to  FIG. 4 , a rotating contact  180  is disposed within the housing  154  and includes a plurality of conducting contact tabs  182  as part of arcuate bus  183  secured to an insulating base  185 . The number of contact tabs  182  corresponds with the number of operations of the cutout  100 . The rotating contact  180  is secured to a rod  184  journally supported within the housing  154  to allow rotation of the rotating contact member  180  ( FIG. 10 ). The base  185  insulates the bus  183  and tabs  182  from the rod  184  and the housing  154 . The rotating contact  180  rotates responsive to a spring bias force provided by a spring  190  ( FIG. 13 ) engaging a slot  212  formed in the rod  184  and a slot (not depicted) in the housing  154 . Also shown in  FIG. 13  is an alternative rotating contact member  180   a  with an arcuate contact surface  192  in place of the contract tabs  182 . 
         [0034]    The contract tabs  182  engage jaw contacts  200  ( FIG. 12 ) disposed within the housing  154  and including a conductor portion  202  that extend through slots  210  formed in the housing  154  to couple to a respective hinge  114 . Each jaw contact  200  includes first and second jaw contact members  204  and  206 , edges  208  of which are chamfered to guide the contact tab  182  into engagement with the jaw contact  200 . 
         [0035]      FIG. 1  illustrates the cutout  100  in a fully reset starting position. The spring  190  is charged and the reset ring  172  is in a first position corresponding with fully reset. Current flows, from the connector  170  through the upper contact assembly  119 , in to the upper mountings  118  and contacts  132 . Current flows through the fuse  102   a  to the hinge end, and the hinge  114  into the bracket  151 , which is connected to the load&#39;s cable. 
         [0036]    In response to a fault current, the fuse  102   a  operates, and fails out of its mounting  116  ( FIG. 5 ). As the fuse  102   a  falls out of its mounting, the cam surface  156  engages the trigger cam  158  of the associated trigger mechanism. This causes the trigger cam  158  to rotate translating the latching bar  160  releases the moving contact  182  within the housing  154 . The moving contact  182  is urged to move by the spring  190  and starts to rotate. 
         [0037]    The moving contact  180  rotates to the second position, where its rotation is stopped once the contact assembly engages the latching bar of the second mounting associated with fuse  102   b.    
         [0038]    The moving contact  180  comes to rest with contact tabs  182  engaging the stationary contacts of the mountings associated with the fuses  102   a  and  102   b  at the second position. Current flows from the upper connector through the fuse  102   b  into its hinge  114 . From the hinge  114  current flows into the associated contact  200 , through the moving contact  180 , which connects via the fuse  102   a  contact  200  and bracket  151  re-energizing the circuit. 
         [0039]    The fault and dropout process described above is repeated causing operation of the fuse  102   b  ( FIG. 6 ). Upon dropout of the fuse  102   b  and engagement of its associated trigger mechanism  152 , the moving contact  180  again rotates and comes to rest at its fully cycled position. The moving contact  180  cannot continue any further as its rotation is stopped by a stop  210 . The resetting ring  172  is the fully cycled position. 
         [0040]    Upon occurrence of a third fault, the fuse  102   c  is caused to operate and drops from its mounting  116  ( FIG. 7 ). At this point, the circuit cannot be restored without intervention of a service technician. 
         [0041]    On arrival at the unit, the service technician removes the down fuses  102   a,    102   b  and  102   c  (not the device does not need to be fully cycled to be serviced. The service technician using an appropriate tool can withdrawn unused fuse from their mountings and service the cutout  100 . With the fuses withdrawn, the service technician moves the resetting ring  172  to the fully reset position, replaces the fuses  102  and engages the fuses in the mountings starting from the fuse  102   c.  The cutout  100  is then fully reset and the service is restored. 
         [0042]    The operating sequence can follow a flow as follows: 
         [0043]    1.—Starting position ( FIGS. 1-3 ). 
         [0044]    2.—Fuse  102   a  operates and hits the associated trigger mechanism  152  which releases the latching bar  160  and allows the moving contact  180  to rotate to the stationary contact  200  of the fuse  102   b  ( FIG. 5 ). 
         [0045]    3.—Fuse  102   b  operates and hits its trigger mechanism  152  releasing its latching rod  160  and allowing the moving contact  180  to rotate to the stationary contact  200  of the fuse  102   c  ( FIG. 6 ). 
         [0046]    4.—Fuse  102   c  operates. Service of the cutout  100  is required to restore operation ( FIG. 7 ). 
         [0047]    5—A service technician resets moving contact  180  by rotating the resetting ring  172  recharging the spring  190  and rotating the moving contact  180  back to the fully reset portion. Fuses  102  are restored and reengaged with their associated mounting beginning with fuse  102   c,  then fuse  102   b  and finally fuse  102   a,  restoring service. 
         [0048]    One of ordinary skill in the art will be able to identify and specify suitable materials, insulating or conducting as the case may be, for building and assembling the cutout  100 . In one preferred embodiment, the hinge support  144  used to attach the housing assembly  154  to the insulator  124  provides mechanical and dielectric strength to support the cutout  100  operation under normal conditions and under fault conditions. It may be made of resin and uses pass trough stainless steel inserts for screws to complete assembly. 
         [0049]    The moving contact assembly  180  transfers the path of current from one fuse  102  to another. The contact tabs  182  engage stationary contacts  200  and current is carried within the bus  183 . The latching bars  160  engage the base  185  to stop rotation of the moving contact  180  on the required position. The base  183  is made of resin and provides insulation between the live parts, tabs  182  and bus  183 , and the shaft  184 . The tabs  182  and bus  183  carry current during the normal conditions and under fault conditions. These are made of copper, e.g., alloy C-110, or another suitable conductor. The shaft  184  holds the base  185  and engages the spring  190 . It is made of a suitable structural material; for example, it may be made of stainless steel. 
         [0050]    The housing  154  supports the moving contact assembly  180 , the trigger mechanisms  156  and the load spring  190 . It also provides insulation to the moving contact  180  and stationary contacts  200  and is made of a suitable structural insulator, for example, resin. An insulating, for example, resin bottom cover  220  encloses the housing  154  and prevents unnecessary access to the housing  154  and the spring  190 . 
         [0051]    The contact tab  182  bus  183  construction of the moving contact  180  allows the current path disengaged while the transition from one fuse  102  to the next is accomplished. This may reduce incidence of flashover caused by the transition. Additionally, while the moving contact  180  begins to rotate, an electrical field is forming between the stationary contacts. The structure of the moving contact  180  gives direction to the electrical field and limits its action to this part inside the housing. When the tab  182  of the moving contact  180  is approaching a stationary contact, the electrical field is more intensive on the approach side of both stationary contacts. Again, this arrangement gives direction to the forming of the electrical field and limits the action of the flashover. Contact pressure between the tab  182  and the stationary contact  200  is also controlled to avoid any hot spots or melting of the contacts causing incomplete or sticking of the rotating contact  180 . 
         [0052]    Additionally, while the structures and methods of the present disclosure are susceptible to various modifications and alternative forms, certain embodiments are shown by way of example in the drawings and the herein described embodiments. It will be understood, however, that this disclosure is not intended to limit the invention to the particular forms described, but to the contrary, the invention is intended to cover all modifications, alternatives, and equivalents defined by the appended claims. 
         [0053]    It should also be understood that, unless a term is expressly defined in this patent using the sentence “As used herein, the term ‘_____’ is hereby defined to mean . . . ” or a similar sentence, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term by limited, by implication or otherwise, to that single meaning. Unless a claim element is defined by reciting the word “means” and a function without the recital of any structure, it is not intended that the scope of any claim element be interpreted based on the application of 35 U.S.C. §112, sixth paragraph.