Medium voltage controllable fuse

1. A medium voltage controllable fuse comprising:

a trigger wire comprised of an exothermic reactive intermetallic material, said trigger wire rapidly heating in response to a trigger signal and thereby initiating an exothermic reaction that destroys the trigger wire;

a high-current fault interrupting section responsible for opening the fuse and extinguishing arcs in the event of a high-current fault, said high-current fault interrupting section including a first fusible element comprised of a conducting member;

a low-current fault interrupting section responsible for opening the fuse and extinguishing arcs in the event of a low-current fault, said low-current fault interrupting section including:

a second fusible element series-connected with the first fusible element of the high-current fault interrupting section, wherein the second fusible element includes a first conducting member comprised of an exothermic reactive intermetallic material, and

an isolating member providing an enclosure that defines an inner recess, wherein at least a section of the first conducting member of the second fusible element and at least a section of the trigger wire are located proximate to each other within the inner recess, said isolating member providing a void area around the section of the first conducting member and the section of the trigger wire; and

a fuse housing defining a chamber for housing the trigger wire, the high-current fault interrupting section, and the low-current fault interrupting section, said fuse housing including a fuse body and a pair of conductive end caps mounted at opposite ends of the fuse body, wherein said high-current and low-current fault interrupting sections are connected in series between the pair of conductive end caps.

2. A medium voltage controllable fuse according to claim 1 , wherein said second fusible element is further comprised of a second conducting member, said first conducting member and said second conducting member comprised of different conductive materials.

3. A medium voltage controllable fuse according to claim 1 , wherein said second fusible element is further comprised of a second conducting member, said second conducting member comprised of an exothermic reactive intermetallic material.

4. A medium voltage controllable fuse according to claim 1 , wherein the low-current fault interrupting section further comprises:

a housing that houses said isolating member inside the fuse housing.

5. A medium voltage controllable fuse according to claim 1 , wherein said conducting member of the first fusible element is made of at least one of the following: silver, copper, copper alloy, aluminum, and zinc.

6. A medium voltage controllable fuse according to claim 5 , wherein said conducting member of the first fusible element is a metal ribbon having perforations and/or notches.

7. A medium voltage controllable fuse according to claim 2 , wherein said second conducting member of the second fusible element is made of at least one of the following: silver, copper, copper alloy, and aluminum.

8. A medium voltage controllable fuse according to claim 1 , wherein said isolating member includes:

a casing; and

a pair of end walls located at opposite ends of the casing.

9. A fuse system comprising:

(a) a medium voltage controllable fuse including:

a trigger wire comprised of an exothermic reactive intermetallic material, said trigger wire rapidly heating in response to a trigger signal and thereby initiating an exothermic reaction that destroys the trigger wire;

a high-current fault interrupting section responsible for opening the fuse and extinguishing arcs in the event of a high-current fault, said high-current fault interrupting section including a first fusible element comprised of a conducting member;

a low-current fault interrupting section responsible for opening the fuse and extinguishing arcs in the event of a low-current fault, said low-current fault interrupting section including:

a second fusible element series-connected with the first fusible element of the high-current fault interrupting section, wherein the second fusible element includes a first conducting member comprised of an exothermic reactive intermetallic material, and

an isolating member providing an enclosure that defines an inner recess, wherein at least a section of the first conducting member of the second fusible element and at least a section of the trigger wire are located proximate to each other within the inner recess, said isolating member providing a void area around the section of the first conducting member and the section of the trigger wire; and

a fuse housing defining a chamber for housing the trigger wire, the high-current fault interrupting section, and the low-current fault interrupting section, said fuse housing including a fuse body and a pair of conductive end caps mounted at opposite ends of the fuse body, wherein said high-current and low-current fault interrupting sections are connected in series between the pair of conductive end caps;

(b) a sensing device for detecting an external condition; and

(c) a fuse controller electrically connected with said trigger wire, said fuse controller supplying the trigger signal in response to the sensing device detecting the external condition.

10. A fuse system according to claim 9 , wherein said fuse controller includes an energy source for supplying a pulse of electrical energy to the trigger wire as said trigger signal.

11. A fuse system according to claim 10 , wherein said fuse controller includes a switch for electrically connecting the energy source to said trigger wire.

12. A fuse system according to claim 9 , wherein said external condition sensed by said sensing device is selected from one of the following:

an arc flash, an overvoltage condition, a temperature level, and a pressure level.

13. A fuse system according to claim 9 , wherein said fuse controller is electrically connected to said trigger wire by connecting wires.

14. A medium voltage controllable fuse according to claim 1 , wherein said trigger signal is a signal external to said medium voltage controllable fuse.

15. A medium voltage controllable fuse according to claim 1 , wherein said trigger signal is supplied by a fuse controller.

16. A medium voltage controllable fuse according to claim 15 , wherein said fuse controller supplies the trigger signal in response to a sensing device detecting an external condition.

17. A medium voltage controllable fuse according to claim 16 , wherein said external condition detected by said sensing device is selected from one of the following:

an arc flash, an overvoltage condition, a temperature level, and a pressure level.

18. A medium voltage controllable fuse according to claim 1 , wherein said medium voltage controllable fuse includes a plurality of said first fusible elements arranged in parallel.

19. A medium voltage controllable fuse according to claim 1 , wherein said medium voltage controllable fuse includes a plurality of said second fusible elements arranged in parallel.

20. A medium voltage controllable fuse according to claim 1 , wherein said section of the first conducting member and said section of the trigger wire located within the inner recess of the isolating member are oriented transverse to each other.