Patent Publication Number: US-2012032772-A1

Title: Joining a current limiting device and a fuse

Description:
TECHNICAL FIELD 
     This description relates to joining a current limiting device and a fuse. 
     BACKGROUND 
     A current limiting fuse may be electrically connected to a fuse included in a fuse holder and/or a fuse assembly by crimping a bare conductive metal strip, which is electrically connected to the current limiting fuse, onto the fuse holder or onto the fuse assembly. 
     SUMMARY 
     A mounting bracket discussed below may be used to electrically and mechanically connect a fuse assembly and a current limiting device. The fuse assembly includes a fuse, a fuse holder, and a fuse housing, or body. The fuse assembly may be a bayonet fuse assembly and the current limiting device may be a current limiting fuse (CLF). The bayonet fuse assembly and the CLF may be placed in a fluid-filled tank of a transformer. 
     Previously, the fuse assembly and the current limiting device were connected with a conductive metal strip connected to the fuse holder, by, for example, a crimp connection. In contrast, the mounting bracket discussed below is secured about a body of the fuse assembly, thus eliminating the need for a crimp connection between the conductive metal strip and the fuse assembly. As compared to the mounting bracket, the crimp connection is more prone to failure, and failure of the crimp connection during use may cause the CLF to separate from the fuse assembly and drop to the floor of the tank. This separation may result in a line-to-ground fault and an arc through the bottom of the tank. Such a failure may cause catastrophic damage to the tank and/or components within and around the tank. The mounting bracket reduces, or eliminates, the possibility of this type of failure by securely mounting the CLF to the fuse assembly with a single conductive bracket that also provides an electrical connection between the CLF and the fuse within the fuse assembly. 
     Additionally, use of the mounting bracket may reduce or limit the amount of hardware required to place and secure the fuse assembly and the CLF in the tank, and may reduce the size of the tank due to the elimination of the conductive metal strip. Using the mounting bracket may also allow for quicker assembly of the fuse assembly and the CLF within the tank. 
     In some prior designs, the CLF was mounted onto the fuse assembly with a mounting bracket. However, in these designs, the mounting bracket does not provide an electrical connection between the CLF and the fuse included in the fuse assembly. Instead, these designs rely on a separate conductive cable to provide an electrical path from the CLF to the fuse. Without the separate conductive cable, these prior systems would not have an electrical connection between the CLF and the fuse, even if the mounting bracket could be made of a conductive material. In contrast to these designs, the mounting bracket discussed below provides both a physical and an electrical connection between the CLF and the fuse within the fuse assembly while eliminating the need for a separate conductive cable. 
     In one general aspect, an assembly includes an electrically conductive mounting bracket, a current limiting device electrically connected to the mounting bracket, and a fuse assembly that includes a body and a fuse. The electrically conductive mounting bracket is configured to mount about the body of the fuse assembly, and, when the electrically conductive mounting bracket is mounted about the body of the fuse assembly, the mounting bracket forms a path for electrical current between the current limiting device and the fuse. 
     Implementations may include one or more of the following features. The current limiting device may include a current limiting fuse. The current limiting fuse may include a protrusion configured to connect to a portion of the mounting bracket. The body of the fuse assembly may include a first contact and a second contact, both of which are electrically connected to the fuse, and the mounting bracket may be electrically connected to the first contact. The mounting bracket may be configured to hold the current limiting device at a predetermined angle relative to a longitudinal axis of the body of the fuse assembly. 
     In some implementations, the mounting bracket may include an end, a first side connected to the end, and a second side connected to the end. The first side and the second side may define an opening that is configured to be placed about the body of the fuse assembly. The mounting bracket may be formed from a single piece. A bore configured to receive a portion of the current limiting device may be formed in the end of the mounting bracket, a first opening may be formed in the first side of the mounting bracket, and a second opening may be formed in the second side of the mounting bracket. The first opening may include two separate openings that pass through the first side of the mounting bracket, and the second opening may include two separate openings that pass through the second side of the mounting bracket. A fastener may connect one of the openings on the first side of the mounting bracket to one of the openings on the second side of the mounting bracket to secure the mounting bracket about the body of the fuse assembly. A conductive connector may be accepted into the other one of the openings on either of the first side and the second side to make an electrical connection to the fuse included in the fuse assembly. 
     In some implementations, the fuse assembly may include a first contact and a second contact, both of which are electrically connected to the fuse, and the fuse assembly may withstand up to a first potential difference between the first contact and the second contact without producing an arc between the first contact and the second contact. The body of the fuse assembly may further include a voltage grading configured to allow the fuse assembly to withstand a second potential difference between the first contact and the second contact without producing an arc between the first contact and the second contact. The second potential difference may be greater than the first potential difference. The voltage grading may include a voltage grading spring. The voltage grading may be formed by rounding a portion of an edge of the mounting bracket. The voltage grading may include a skirt that increases a creep distance between the mounting bracket and one of the first and second contacts and that is included on the body of the fuse assembly. 
     In another general aspect, a mounting bracket for electrically and mechanically connecting a current limiting device to a body of a fuse assembly includes an end portion configured to join the mounting bracket to the current limiting device and, once joined, to electrically connect the mounting bracket to the current limiting device. The mounting bracket also includes a side portion attached to the end portion and configured to mount about the body of the fuse assembly such that, once the side portion is mounted about the body, a path for electrical current is formed between a fuse included in the fuse assembly, the mounting bracket, and the current limiting device. 
     Implementations may include one or more of the following features. The mounting bracket may include a second side portion connected to the end portion, and the second side portion may be substantially parallel to the side portion. The end portion may be angled relative to the side portion such that, once the side portion is mounted about the body, the current limiting element is held at an angle relative to a longitudinal axis of the body of the fuse assembly. The side portion may include a rounded edge. 
     In another general aspect, a method of electrically and mechanically connecting a current limiting device to a fuse included in a fuse assembly includes coupling a mounting bracket to the current limiting device such that the mounting bracket is secured to and electrically connected to the current limiting device, and mounting the mounting bracket about a body of the fuse assembly such that the mounting bracket is secured about the fuse holder and an electrical path is formed between the current limiting device, the mounting bracket, and the fuse. 
     In another general aspect, a system includes a tank, a fuse assembly mounted in the tank, a mounting bracket mounted about the body of the fuse assembly, and a current limiting device electrically and mechanically coupled to a fuse within the fuse assembly through the mounting bracket, the mounting bracket holding the current limiting device at an angle relative to a longitudinal axis of the body of the fuse assembly. 
     In some implementations, the fuse assembly may be mounted through one of a side wall or a top of the tank. 
     Implementations of any of the techniques described above may include a method, a process, a system, a device, an apparatus, or a mounting bracket. The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an example of a system that includes a mounting bracket mounted to a fuse assembly. 
         FIG. 2  shows a cross-sectional view of the fuse assembly of  FIG. 1 . 
         FIG. 3A  shows a developed view of the mounting bracket of  FIG. 1 . 
         FIG. 3B  shows a formed view of the mounting bracket of  FIG. 1 . 
         FIG. 3C  shows a perspective view of the mounting bracket of  FIG. 1 . 
         FIGS. 4 and 5  show perspective views of the mounting bracket of  FIG. 1 . 
         FIG. 6  shows a cross-sectional view of an exemplary current limiting device. 
         FIG. 7A  shows a developed view of another mounting bracket. 
         FIG. 7B  shows a formed view of the mounting bracket of  FIG. 7B . 
         FIG. 7C  shows a perspective view of the mounting bracket of  FIG. 7B . 
         FIG. 7D  shows a rounded edge of the mounting bracket taken along line B of  FIG. 7B . 
         FIGS. 8 and 9  show a spring that forms a voltage grading. 
         FIG. 10  shows a fuse holder that includes a voltage grading. 
         FIG. 11  shows an example process for connecting a current limiting device to a fuse. 
         FIG. 12A  shows an alternative exemplary system that includes a mounting bracket mounted to a fuse assembly. 
         FIG. 12B  shows a developed view of the mounting bracket shown in  FIG. 12A . 
         FIG. 12C  shows a formed view of the mounting bracket shown in  FIG. 12A . 
         FIG. 12D  shows a perspective view of the mounting bracket shown in  FIG. 12A . 
     
    
    
     Like reference symbols in the various drawings may indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a system  100  that includes a mounting bracket  105  mounted to a fuse assembly  110 .  FIG. 2  shows a cross-sectional view of the fuse assembly  110  and a cross-sectional view of a fuse link  900  within the fuse assembly  110 . When the mounting bracket  105  is mounted to the fuse assembly  110 , a current limiting device  115  is mechanically secured to the fuse assembly  110  and electrically connected to a contact  117  on a body  112  of the fuse assembly  110 . The fuse assembly  110  is mounted through a side wall  120  of a tank  125  that is filled with a fluid  107 . The fluid may be, for example, a mineral oil or some other dielectric fluid. The tank  125  and the components in the tank  125  may be part of a transformer. 
     The fuse assembly  110  includes a stationary housing  113  made up of the body  112  with the contact  117  and a contact  119 . The body  112  may be referred to as an outer tube or an outer housing. As shown in  FIG. 1 , the mounting bracket  105  mounts about the body  112 . The mounting bracket  105  is made from an electrically conductive material. As shown in  FIG. 2 , the fuse assembly  110  further includes a fuse holder  121 , which may be removable from the fuse assembly  110 . The fuse holder  121  includes an inner fuse cartridge holder assembly  1100  (which also may be referred to as a fuse stab  1100 ) and a fuse cartridge  202 . 
     The inner fuse cartridge holder assembly  1100  includes a handle  148 , a sealing member  145 , a gasket  140 , and a lock nut  142 . The fuse stab  1100  includes an end plug  1100   a , a stab body  1100   b , a connective insert  1100   c , and a gas port  210  (or fluid port  210 ). The sealing member  145  is mounted on the stab body  1100   b , which has an end plug  1100   a  securely assembled in a lower bore of the stab body  1100   b  and a connective insert  1100   c  in a top end. 
     The fuse cartridge  202  includes fuse cartridge ends  122   a  and  122   b , a fuse tube  122   c , and a fuse link  900 . The fuse link  900  includes fuse link end contacts  900   a  and  900   b , a fuse link tube  900   c  that defines a bore  901 , and a fuse wire  122 . 
     When mounted to the fuse assembly  110 , the mounting bracket  105  electrically connects an end cap  114  of a current limiting device  115  (such as a current limiting fuse) to the contact  117  of the fuse assembly  110  such that, when the mounting bracket  105  is mounted about the body  112 , the current limiting device  115  is electrically connected to the fuse cartridge assembly  202 . In the example of  FIG. 1 , the mounting bracket  105  is electrically and physically connected to the contact  117  through a fastener  118 . 
     When the mounting bracket  105  is mounted about the body  112  and connected to the contact  117 , an electrical circuit is formed between a coil (not shown) connected to a lead  130 , the mounting bracket  105 , and the current limiting device  115 . The lead  130  is connected to the contact  119 , thus providing an electrical connection between the mounting bracket  105  and the coil through the fuse wire  122 . The current limiting device  115  is electrically connected to a high-voltage bushing  135  though a lead  133 . The lead  133  is electrically connected to the current limiting device  115  at a connection point  134 . The connection point  134  may include a hex-head bolt that secures the lead  133  to an end cap  146  of the current limiting device  115 . In use, power may enter the system  100  through the bushing  135 , pass through the current limiting device  115  and into the bracket  105 , travel through the bracket  105  to the bottom contact  117  and into the fuse cartridge  202 , pass through the fuse wire  122  and exit through the top contact  119 , and travel to the coil connected to the lead  130 . 
     To assemble the system  100 , the fuse assembly  110  is placed through an opening in the tank wall  120 , and the opening is sealed with the gasket  140  to prevent the flow of fluid  107  from inside the tank  125  to the exterior of the tank  125 . The tank  125  is filled with fluid  107  to a height  137 , though in some examples more or less fluid may be used. For example, the tank  125  may be filled with fluid to a height  139 . On the exterior of the tank  125 , the lock nut  142  secures the fuse assembly  110  in the wall  120 . In the example shown in  FIG. 1 , the fuse assembly  110  is held at an angle of approximately 53° from the tank wall  120 , although other angles are possible. 
     Referring again to  FIG. 2 , the body  112  of the fuse assembly  110  includes the contacts  117  and  119 , each of which are electrically connected, respectively, by spring-loaded contact buttons  111  and  116  to the fuse cartridge ends  122   a  and  122   b . The fuse cartridge ends  122   a  and  122   b  are electrically connected, respectively, to the end contacts  900   a  and  900   b  (each of which have electrical contacts) of the fuse link  900 . The fuse cartridge end  122   a  is electrically connected to the contact of the fuse link end contact  900   a  by the end plug  205 . The fuse cartridge end  122   b  is electrically connected to the fuse link end contact  900   b  by the stab end plug  1100   a . The fuse wire (or fuse link or fuse element)  122  is electrically connected to the fuse link end contacts  900   a  and  900   b  by soldering or other known electrical connection techniques. 
     Thus, because the fuse wire  122  is electrically connected to the end contacts  900   a  and  900   b , which are respectively electrically connected to the fuse cartridge ends  122   a  and  122   b  that are connected to the contacts  117  and  119 , the contacts  117  and  119  on the body  112  are electrically connected through the fuse wire  122 . During fuse operation, the fuse wire  122  melts or otherwise is broken such that the wire  122  separates to prevent current from flowing from the fuse link contact  900   a  to the contact  900   b.    
     The fuse wire  122  is inside the bore  901  of the fuse link tube  900   c . The fuse link tube  900   c  is made from a high-strength, mechanical shock resistant, non-tracking material such as TEFLON that directs and contains gases during fuse operation. The electrically conductive end contacts  900   a  and  900   b  of the fuse link  900  may be cone-shaped to facilitate connection of the fuse link  900  to the fuse cartridge assembly  202 . The fuse cartridge  202  is made of a high-strength dielectric tube  122   c  (the fuse tube  122   c ) and includes the two conductive ends  122   a  and  122   b . The fuse cartridge ends  122   a  and  122   b  may include tapered leading and trailing edges to facilitate insertion and removal of the fuse cartridge  202  past the spring loaded contact buttons  111  and  116  on the stationary housing  113  contacts  117  and  119 . 
     The contacts  117  and  119  may be referred to as terminals and the contacts  117  and  119  are configured to connect to high-voltage leads and connections. The contacts  117  and  119  are electrically conductive and may be made from a solid, electrically conductive material or the contacts  117  and  119  may be plated with an electrically conductive material, such as copper, silver, or a combination thereof. The contacts  117  and  119  have respective openings  221  and  222  that are sized to receive a conductive fastener (such as bolt or screw or the fastener  118 ) that makes electrical contact with the mounting bracket  105 . The fuse assembly  110  also may include the flapper valve  123 , which is open when the fuse holder  121  is inserted and closed when the fuse holder  121  is removed to reduce an amount of oil or fluid spilled from the fuse assembly  110 . 
     The fuse holder  121  also includes an end plug  205  and fluid ports  210 . The end plug  205  includes a threaded end (not shown) that makes contact with the fuse link end contact  900   a , which is electrically connected to the fuse wire  122 . The end plug  205  also diverts gases during fault interruption. The fluid ports  210  (which may be referred to as gas ports) release gas during fuse operations and prevent excess pressure on the fuse holder  121 . The fluid ports  210  in the stab body  1100   b  are open to an exterior of the fuse assembly  110  through holes in the body  112  at the area where the flapper valve  123  may be assembled. In the example shown in  FIG. 2 , the fluid ports  210  are located at the lower end of the stab body  1100   b  aligned with openings in the body  112  where the flapper valve  123  may be installed. 
     The fuse assembly  110  includes a flange  215  that interacts with the gasket  140  in a compressed state during, for example, assembly. As shown in  FIG. 1 , the gasket  140  is retained on the inside of the tank  125  to seal the opening in which the fuse assembly  110  is placed. As discussed above with respect to  FIG. 2 , the inner fuse cartridge holder assembly  1100  includes the sealing member  145  and the handle  148 . The sealing member  145  may be, but is not limited to, a multiple-groove Nitrile rubber seal. The opening in the tank may be sealed by compressing the sealing member  145  in an axial direction by cam action of the handle  148 . The handle  148  is a hot or hook stick-operable handle that may be used to seal and unseal the fuse assembly  110  and/or to remove or place the fuse assembly  110  in the wall  120  and/or to remove or install the fuse holder  121 , perhaps under hot operation. For example, a hot stick may be inserted into an opening in the handle  148  to remove the fuse assembly  110 , thus opening the circuit, while the transformer is energized. In another example, the handle  148  may be used to remove the fuse holder  121  from the fuse assembly  110  such that the fuse holder  121  may be, for example, replaced without disturbing the current limiting device  115 . 
     Referring to  FIG. 3A , the mounting bracket  105  is shown after being stamped out or otherwise formed during manufacture. After initial formation, the mounting bracket  105  may be flat, or almost flat, and  FIG. 3A  shows the mounting bracket in this initial state. 
     The mounting bracket  105  includes an end portion  305  that includes a bore  307  configured to connect to the end cap  114  of the current limiting device  115  as shown in  FIG. 1 . The bore  307  may be a smooth opening that passes through the end portion  305 . Bore  307  is sized to receive a conductive fastener (such as a bolt or a screw) that, when tightened or otherwise fastened, makes electrical contact with the mounting bracket  105  and the current limiting device  115 . The mounting bracket  105  also includes a first side  309  and a second side  311 , both of which are connected to the end portion  305 . In the example shown, two openings  313  and  314  are formed in the first side  309 , and two openings  316  and  317  are formed in the second side  311 . 
     The mounting bracket  105  may be stamped out from a solid sheet of metal or other conductive material or the mounting bracket  105  may be formed by connecting or coupling more than one piece of conductive material together. The stamped out mounting bracket  105  may be folded or otherwise bent at locations  318  and  319  to shape the mounting bracket  105  for positioning about the body  112  of the fuse assembly  110 . The stamped out mounting bracket  105  may be bent at 90-degree angles relative to the end portion  305  such that, once formed, the first side  309  and the second side  311  are substantially parallel to each other and form an opening that receives the body  112  of the fuse assembly  110 . 
     In some implementations, the first side  309  and the second side  311  are angled at an angle “A,” which may be approximately 127 degrees. Angling the first side  309  and the second side  311  results in the mounting bracket  105  including flanges  321  and  322  that hold the current limiting device  115  at the angle “A” relative to a longitudinal axis of the body  112  of the fuse assembly  110 . Mounting the current limiting device  115  at the angle “A” results in a dampening of mechanical vibrations and a corresponding reduction in motion of the current limiting device  115 . Thus, by holding the current limiting device  115  at the angle “A,” motion of the current limiting device  115  may be eliminated or greatly reduced. 
     Reduction or elimination of motion of the current limiting device  115  may result in a system that is more robust and easier for the purchaser to set up and implement. For example, the system  100  shown in  FIG. 1  may be assembled prior to purchase and shipped to the end-user as a complete unit. Forming the mounting bracket  105  such that the current limiting device  115  is held at the angle “A” may help to ensure that the complete system is transported to the end-user without the current limiting device  115  snapping off, being damaged, or causing damage to other portions of the tank  125  during transit. Additionally, holding the current limiting device  115  at the angle “A” may impart benefits during operation of the system  100 . For example, if the tank  125  is bumped during operation, the current limiting device  115  stays in position. 
     Referring to  FIG. 3B , a side view of the mounting bracket  105 , formed into a shape that accommodates the body  112  of the fuse assembly  110 , is shown.  FIG. 3B  shows the mounting bracket  105  along the direction “D” as labeled in  FIG. 3C . Referring to  FIG. 3C  the openings  312 ,  316  and  314 ,  317  correspond to each other such that a fastener (such as a bolt) that has sufficient length to pass through the first side  309  and the second side  311 , passes through one of the openings  312 ,  316  and  314 ,  317  and also passes through the other of the openings  312 ,  316  and  314 ,  317 , respectively. In  FIG. 1 , the fastener  118  passes through the openings  314  and  317  to electrically connect the mounting bracket  105  to the contact  117 . Arrangement of the openings in this manner allows the mounting bracket  105  to be secured to the body  112  of the fuse assembly  110 . Additionally, an opening  325  is formed such that the mounting bracket  105  may accept the body  112  of the fuse assembly  110 . 
     Referring to  FIG. 4 , a perspective view of the mounting bracket  105  is shown. As compared to  FIG. 1 , the view shown in  FIG. 4  shows an underside of the mounting bracket  105 . The fastener  118  passes through openings  317  and  314  ( FIG. 3C ) formed in the bracket  105  and through the opening  221  ( FIG. 2 ) formed in the contact  117  and, in this example, the fastener  118  is secured with a nut  402 . Additionally, a fastener  408  passes through the openings  312  and  316  formed in the mounting bracket  105  and is bolted with a nut  410  to further secure the fuse assembly  110  to the body  112  of the fuse assembly  110 . In this example, the contacts  117  and  119  have spring loaded contact tabs formed on the contacts, with conductive arc resistant contact buttons  111  and  116  secured on the end. As discussed above with respect to  FIGS. 1 and 2 , the spring loaded contact buttons  111  and  116  electrically connect the contacts  117  and  119  to the fuse cartridge assembly ends  122   a  and  122   b , respectively, on the fuse holder  121 . 
       FIG. 5  shows a perspective view of an assembly that includes the fuse assembly  110  electrically and physically connected to the current limiting device  115  by way of the mounting bracket  105 . The mounting bracket  105  holds the current limiting device  115  at the angle “A” relative to a longitudinal axis “L” of the fuse assembly  110 . As discussed above, holding the current limiting device  115  at the angle “A” reduces mechanical vibrations and further secures the current limiting device  115  to the fuse assembly  110 . 
       FIG. 6  shows a cross-sectional view of an example current limiting device  115 . In this example, the current limiting device  115  is a current limiting fuse (CLF). The current limiting device  115  includes the end cap  114  and an end cap  146 , both of which may be conductive end caps, a fuse ribbon  610  that electrically connects the end cap  114  to the end cap  146 , a housing  620 , and a filler material  625 . In this example the end caps  114  and  146  have two conductive, threaded sealing bosses  114   b  and  146   b . The seal may be made through a known technique, such as soldering. In other examples fuse caps, the internal or external threads may be formed into a one piece cap. 
     The end cap  114  and the end cap  146  may be solid copper end caps with conductive inserts made from, for example, copper or brass. In some implementations, one or both of the end cap  114  and the end cap  146  may be threaded. The fuse ribbon  610  may be made from silver or another material that is stable when exposed to current cycling and thermal stress and that separates under relatively consistent conditions. The fuse ribbon  610  may include ribbon holes, notches, or deformations  611  that control and minimize peak arc voltages that result from current interruptions. The housing  620  may be made from fiberglass or another material that withstands and maintains the integrity of the housing when exposed to pressures and forces resulting from clearing currents of up to 50 kA and beyond. The filler  625  may be a material that absorbs heat and aids in quenching arcs. The filler  625  may be a silica sand. 
     Referring also to  FIG. 4 , the mounting bracket  105  is electrically connected to the current limiting device  115  at the conductive end cap  114 . The current limiting fuse end cap  114  includes a conductive threaded boss  114   b  ( FIG. 6 ) that seals the end cap  114  and provides a connection between the current limiting device  115  and the mounting bracket  105 . In some implementations, the current limiting device  115  is connected to the bracket  105  by passing a ¼″-20 bolt though the bore  307  and threading the bolt into the threaded boss  114   b  of the current limiting device  115 . Bolts of other sizes and other types of fasteners may be used. Once connected, the current limiting device  115  is electrically connected to the mounting bracket  105 , which is electrically connected to the fuse holder  121  through the contact  117 . Accordingly, the mounting bracket  105  electrically connects the current limiting device  115  to the fuse cartridge assembly  202 . 
       FIGS. 7A-7C  show another implementation of a mounting bracket. The mounting bracket  705  is similar to the mounting bracket  105  except that the mounting bracket  705  includes rounded edges  706  that increase a withstand capability of the fuse assembly  110  between the top contact  119  and the rounded edge  706  of the mounting bracket  705 . The withstand capability of the fuse assembly  110  is the maximum voltage impulse that may be withstood between the contact  117  and the contact  119 . 
     As shown  FIG. 2 , the contact  117  and the contact  119  are separated by a distance. A relatively short distance between the contact  117  and the contact  119  is desirable to, for example, achieve a smaller fuse assembly  110 , which allows for a corresponding reduction in, for example, the size of the tank  125 . However, if the distance between the contacts  117  and  119  is too short, an arc may form outside of the fuse assembly  110  and between the contact  117  and the contact  119  when the fuse holder  121  is activated. To increase the minimum voltage at which arcing occurs while also retaining the contact  117  and the contact  119  at a relatively close spacing to each other, one or more voltage grading methods between the contacts  117  and  119  may be used. 
     The presence of the one or more voltage gradings allows the fuse assembly  110  to withstand a higher voltage potential difference without arcing than an implementation of the fuse assembly  110  that does not include the one or more voltage gradings. For example, use of the voltage grading may allow the fuse assembly  110  to withstand up to about, but not limited to, a 45 kV high pot level without increasing the distance between the contacts  117  and  119 . 
     The voltage grading may be formed by rounding the edges of the mounting bracket  105  that are closest to the contact  119 , by placing a spring in electrical contact with the mounting bracket  105  and between the mounting bracket  105  and the contact  119 , or by adding skirts to the body  112  of the fuse assembly  110 . These techniques are discussed in turn, respectively, in  FIGS. 7A-7C ,  FIGS. 8 and 9 , and  FIG. 10 . 
       FIG. 7A  shows a developed view of the mounting bracket  705 ,  FIG. 7B  shows a formed view of the mounting bracket  705 ,  FIG. 7C  shows a perspective view of the mounting bracket  705 , and  FIG. 7D  shows one of the rounded edges  706  along the line “B.” The rounded edges  706  are on the side of the mounting bracket that is closer to the contact  119 . The rounded edges  706  may be formed by rolling the edges of the mounting bracket  705  to about, but not limited to, a radius between about 0.10 and 0.375 inches (between about 0.265 and 0.9525 centimeters). For example, in some implementations, the radius of the rounded edges  706  may be 0.25 inches (0.635 cm). The rounded edges  706  are rolled away from the contact  119 . In some implementations, one of the two edges may be rounded. 
     The mounting brackets  105  and  705  conduct electricity and are made from any suitable electrically conductive material having sufficient strength to support the current limiting device  115 . In some implementations, the conductive material may be dead soft copper. In some implementations, the conductive material may be ¼ Hard copper, which may result in the mounting bracket  105  or  705  being stronger (perhaps 4-5 times stronger) than a bracket made from dead soft copper. In other implementations, the mounting bracket  105  or  705  may be made from copper-plated or silver-plated steel. 
       FIGS. 8 and 9  show a spring  805  disposed between the mounting bracket  105  and the contact  119  to form a voltage grading. The spring  805  is made from a conductive material and includes ends  806  and  807 . The ends  806  and  807  may be placed in an interference fit between the body  112  of the fuse assembly  110  and the mounting bracket  105  such that the spring  805  makes electrical contact with the mounting bracket  105 . The spring  805  may be referred to as a voltage grading spring. 
       FIG. 10  shows an alternative implementation of a fuse assembly  1010 . As compared to the fuse assembly  110 , the fuse assembly  1010  includes a body  1012  on which one or more skirts  1011  are formed. The mounting bracket  105  is mounted to the body  1012 . The fuse assembly  1010  includes an upper contact  1014  and a lower contact  1015 . The upper contact  1014  and the lower contact  1015  are both electrically connected to a fuse link, such as the fuse link  122 , and the upper contact  1014  and the lower contact  1015  are placed along the fuse assembly  1010  similarly to how the contacts  117  and  119  are arranged relative to each other on the fuse assembly  110 . 
     The skirt  1011  is between the mounting bracket  105  and an upper contact  1014  such that the skirt  1011  acts as a creep distance extender and increases the withstand capability of the fuse assembly  1010 . The skirt  1011  adds creep distance between the upper contact  1014  and the mounting bracket  105  without significantly adding to the physical distance that separates the upper contact  1014  and the lower contact  1015 . The skirt  1011  may be molded directly into the body  1012  of the fuse assembly  1010 . 
       FIG. 11  shows an example of a process for electrically and mechanically mounting a current limiting device  115  to a body  112  of a fuse assembly  110 . The end portion  305  of the mounting bracket  105  is coupled or otherwise connected to the current limiting device  115  such that the mounting bracket  105  is secured to and electrically connected to the current limiting device  115  ( 1210 ). The current limiting device  115  may be coupled to the bracket  105  by connecting the current limiting device  115  to the bracket  105  by passing a ¼″-20 bolt through the bore  307  in the bracket  105  and into the threaded boss  114   b  of the current limiting device  115 . Connection in such a manner results in the current limiting device  115  being electrically and mechanically connected to the bracket  105 . The mounting bracket  105  is mounted about the body  112  of the fuse assembly  110  such that the mounting bracket  105  is secured about the fuse assembly  110  and an electrical path is formed between the current limiting device  115 , the mounting bracket  105 , and the fuse holder  121  ( 1220 ). 
     The mounting bracket  105  may be secured about the fuse assembly  110  by passing the fastener through the openings  314  and  317  of the mounting bracket  105  and through the opening  221  of the contact  117  such that the fastener makes electrical contact with the contact  117 . The end portion  305  of the mounting bracket  105  may be coupled to the current limiting device  115  by threading a threaded end of the current limiting device  115  to a threaded bore  307  formed in the end portion  305 . 
       FIG. 12A  shows another example system  1300  that includes a mounting bracket  1305  mounted to a fuse assembly  1310 . The mounting bracket  1305  is made from an electrically conductive material, such as ¼ Hard copper or dead soft copper. The mounting bracket  1305  electrically and mechanically connects the current limiting device  115  and the fuse assembly  1310 . The fuse assembly  1310  is mounted in a tank  1311  by passing the fuse assembly  1310  through an opening in the top of the tank  1311  or a cover that covers the top of the tank  1311 . As shown in  FIG. 12A , the fuse assembly  1310  is placed vertically, or nearly vertically, in the tank  1311 . The tank  1311  is filled with a fluid to a fluid level  1307  that is a distance “B” below the top of the tank  1311 . 
     The fuse assembly  1310  includes a body  1312  with contact leads  1317  and  1319 , and a molded portion  1314 . Springs  1321  and  1322  encircle the body  1312  of the fuse assembly  1310  and hold contact buttons  1323  and  1324 , respectively, in place. In the example shown in  FIG. 12A , each of the contact buttons  1323  and  1324  include four separate contact buttons, three of which are shown in  FIG. 12A . The contact buttons  1323  are held to the body  1312  with the spring  1321 , and the contact buttons  1324  are held to the body  1312  with the spring  1322 . The contact lead  1317  is electrically connected to the contact buttons  1323  and the contact lead  1319  is electrically connected to the contact buttons  1324 . Similar to the contacts  117  and  119  of the fuse assembly  110  discussed above, the contact leads  1317  and  1319  of the fuse assembly  1310  are electrically connected to each other through a fuse wire (not shown) that is internal to the fuse assembly  1310  and that electrically connects the contact buttons  1323  to the contact buttons  1324 . The contact leads  1317  and  1319  each include a connection interface, such as a connection interface  1317   a , which may be a crimp connection. 
     Referring to  FIG. 12B , the mounting bracket  1305  includes openings  1305   a ,  1305   b , and  1305   c . The mounting bracket  1305  is bent about the locations  1306   a  and  1306   b  to form the formed mounting bracket  1305  shown in  FIG. 12C . In the example shown in  FIG. 12C , the mounting bracket  1305  is bent at the locations  1306   a  and  1306   b  at an angle of about 90° such that the openings  1305   a  and  1305   c  align with each other. However, in other examples, the mounting bracket  1305  may be bent at another angle. 
     Referring to  FIGS. 12A and 12C , the bracket  1305  is electrically connected to the contact lead  1317  by aligning the openings  1305   a  and  1305   c  with an opening (such as the connection interface  1317   a ) of the contact lead  1317  and passing a bolt  1330  through the opening  1305   a , the connection interface  1317   a , and the opening  1305   c  of the bracket  1305 . The bolt  1330  is secured with a nut  1334 . The bolt  1330  is made of an electrically conductive material and makes physical contact with the connection interface  1317   a  such that the contact lead  1317  is electrically connected to the bracket  1305 . 
     The molded portion  1314  of the fuse assembly  1310  is also secured to the bracket  1305  by passing the bolt  1330  through an opening in the molded portion  1314 . The molded portion  1314  is made of a flexible material that bends into the bracket  1305  such that the current limiting device  115  is aligned vertically, or substantially vertically, in the tank  1311 . In other implementations, the molded portion  1314  is rigid and protrudes from the body  1312  at an angle that is perpendicular to a surface of the body  1312  such that the bracket  1305  holds the current limiting device  115  horizontally, or approximately horizontally, in the tank. The molded portion  1314  may protrude from the surface of the body  1312  at any angle, and in examples in which the molded portion  1314  is rigid, the current limiting device  115  is held at an angle relative to the top of the tank  1311  that is determined by the angle at which the molded portion  1314  protrudes from the surface of the body  1312 . The molded portion  1314  may be made of a material that does not conduct electricity. 
     The current limiting device  115  is electrically connected to the bracket  1305  by connecting the end cap  114  to a bolt  1336  that passes through the opening  1305   b  of the bracket  1305 . The bolt  1336  may be threaded into the threaded boss  114   b  of the current limiting device  115 .  FIG. 12D  shows a side view of the mounting bracket  1305  without the bolt  1330  and also illustrates how the bolt  1336  is disposed in the mounting bracket  1305  for connection to the current limiting device  115 . 
     Once mounted to the fuse assembly  1310  by way of the mounting bracket  1305 , the current limiting device  115  is electrically connected to the contact lead  1317  and mechanically connected to the body  1312 . 
     Other implementations are within the scope of the claims. For example, the fuse assembly  110  may have a one-inch cross-sectional diameter. More than one skirt  1011  may be formed on the fuse assembly  1010 . Multiple of the voltage gradings discussed with respect to  FIGS. 7A-7C  and  8 - 10  may be employed on a single fuse assembly. Any or all of the voltage gradings discussed with respect to  FIGS. 7A-7C  and  8 - 10  may be employed on the fuse assembly  1310 . 
     The fuse assembly  110  may be a Bay-O-Net fuse assembly, available from Cooper Power Systems™. The flapper valve  123  may be an optional feature and the fuse assembly  110  may be formed without the flapper valve  123 . The system  100  shown in  FIG. 1  may include a tank cover, and the fuse assembly  110  may be mounted through that tank cover. 
     The angle “A” shown in  FIG. 5  may be an angle other than 127 degrees. For example, the angle “A” may be such that the current limiting device  115  is positioned vertically in the tank  125  parallel to the tank wall  120 . In another example, the angle “A” may be such that the current limiting device  115  is positioned horizontally in the tank  125 , with cap  146  toward the back of the tank  125 . Such an arrangement minimizes the distance required from the lower surface of the fuse to the tank bottom  126 . The current limiting device  115  may be mounted with the end cap  146  near the tank front wall  120  and parallel to the center line of the fuse assembly  110 . Such an arrangement provides a relatively compact design. In some implementations, the mounting bracket  105  may be configured to mount the current limiting device  115  vertically above the lower contact  117 , with the current limiting device  115  end cap  114  toward the surface of the fluid  107  at the height  137  or  139 . In these implementations, the current limiting device  115  is sized such that the device  115  remains in the fluid  107  despite being oriented vertically towards the top of the tank  125 . 
     The fuse assembly  110  may include any type of submersible or under-fluid expulsion fuse, such as an under-oil expulsion fuse. For example, the fuse link  900 , included in the fuse cartridge  202 , may be an under-oil expulsion fuse. The fuse link  900  may be a fault or thermal actuating fuse.