Disconnector device for a surge arrester and a protection assembly comprising a surge arrester connected to such a disconnector device

Abstract

This disclosure concerns a disconnector device for a surge arrester. The disconnector device comprises a housing encompassing a cavity and a disconnector unit provided inside the cavity. The disconnector device is connectable to the surge arrester and to ground potential. The housing forms an inner housing of a housing unit. The housing unit comprising an inner housing and an outer housing. The at least one ventilation opening of the inner housing is fluidly connected to the at least one further ventilation opening of the outer housing such that a labyrinth with a gas escape path for the gases from the operating disconnector cartridge is formed.

Claims

1. A disconnector device for a surge arrester, the disconnector device comprising: a housing encompassing a cavity; a disconnector unit provided inside the cavity, having a first terminal that is connectable to the surge arrester, a second terminal that is connectable to ground potential, a member provided at the second terminal and being fitted to the housing, and a disconnector cartridge provided in the cavity; wherein the housing forms an inner housing of a housing unit, the housing unit comprising further an outer housing, and wherein the inner housing comprises at least one ventilation opening connecting the cavity to an outside of the inner housing, and wherein the outer housing comprises at least one further ventilation opening connecting the outside of the inner housing to an outside of the disconnector device for releasing gases from the operating disconnector cartridge, and wherein the at least one ventilation opening and the at least one further ventilation opening are displaced against one another such that a labyrinth with a gas escape path for the gases from the operating disconnector cartridge is formed.

2. The disconnector device according to claim 1, wherein the labyrinth is designed such that no particle originating from the cavity can leave the cavity to the outside of the disconnector device unimpededly.

3. The disconnector device according to claim 1, wherein the at least one further ventilation opening is designed such that no particles of harmful size that are potentially capable of igniting a fire can pass through them.

4. The disconnector device according to claim 1, wherein the movable member is arranged in the housing in a movable manner such that it is guided by the inner housing from an initial position to an end position at an end of the cavity by gas from the disconnector cartridge in an operating state of the disconnector unit.

5. The disconnector device of claim 4, wherein the housing unit has a retaining section for retaining the movable member at the retaining section once the movable member was propelled towards the end of the cavity.

6. The disconnector device of claim 5, wherein the retaining section of the housing unit is formed in that the inner housing protruding into the cavity.

7. The disconnector device of claim 1, wherein the housing unit has an opening at the end of the cavity, and wherein the movable member and the opening are adjusted to each other such that a portion of the movable member fits into that opening and thereby closes it.

8. The disconnector device of claim 7, wherein the movable member has a tubular section with a diameter fitting to the opening such that a movement of the movable member during operation of the disconnector unit is guided by the opening.

9. The disconnector device of claim 7, wherein after operation of the disconnector unit, a portion of the movable member protrudes through the opening such that it is visible from an outside of the housing to an observer.

10. The disconnector device of claim 9, wherein the portion of the movable member that is protruding through the opening is formed by the tubular section.

11. The disconnector device of claim 9, wherein the tubular section of the movable member is that long that it protects a ground cable from buckling at the time of operating the disconnector device once the ground cable is connected to the second terminal.

12. The disconnector device of claim 8, wherein at least the portion of the movable member protruding through the opening after operation of the disconnector unit has a signal color for indicating on whether the disconnector unit already operated or whether it is still in its pristine state.

13. The disconnector device of claim 1, wherein the at least one ventilation opening is formed as a plurality of openings in the inner housing.

14. The disconnector device of claim 1, wherein the at least one ventilation opening has a slot-like shape extending in the direction of a longitudinal axis defined by the overall shape of the cavity and a moving direction of the movable member.

15. The disconnector device of claim 1, wherein at least a part of the movable member has a cup shaped portion, and wherein the cup portion encompasses the disconnector cartridge at least partly.

16. The disconnector device of claim 1, wherein the housing unit is mechanically connected to the first terminal of the disconnector unit.

17. The disconnector device of claim 1, wherein a cross-section of the movable member and of the cavity is of polygonal shape.

18. An overload protection assembly, comprising a high voltage surge arrester and a disconnector device according to claim 1, wherein a first terminal of the surge arrester is electrically connectable to an electrical grid line; and wherein the first terminal of the disconnector device is electrically connected to a second terminal of the high voltage surge arrester; and wherein the second terminal of the disconnector device is electrically connectable to ground potential.

19. The disconnector device of claim 2, wherein the housing unit has an opening at the end of the cavity, and wherein the movable member and the opening are adjusted to each other such that a portion of the movable member fits into that opening and thereby closes it.

20. An overload protection assembly, comprising a high voltage surge arrester and a disconnector device according to claim 2, wherein a first terminal of the surge arrester is electrically connectable to an electrical grid line; and wherein the first terminal of the disconnector device is electrically connected to a second terminal of the high voltage surge arrester; and wherein the second terminal of the disconnector device is electrically connectable to ground potential.

21. The disconnector device according to claim 1, wherein the labyrinth continues to exist after an electrical separation of the first terminal from the second terminal.

22. The disconnector device according to claim 21, wherein the at least one ventilation opening of the inner housing penetrates therethrough transversely to a direction of a longitudinal axis of the disconnector unit defined by the overall shape of the cavity and a moving direction of the movable member.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a schematic cross-sectional view of a disconnector device according to a first embodiment in a pristine state, i.e. before operation;

(2) FIG. 2 shows the disconnector device of FIG. 1 after operation;

(3) FIG. 3 shows a cross-sectional view of a disconnector device according to the first embodiment without disconnector elements like the first terminal, the second terminal, the disconnector cartridge, the movable member and the like;

(4) FIG. 4 shows an overload protection assembly with a surge arrester and a disconnector device according to the first embodiment;

(5) FIG. 5 shows a simplified schematic cross-sectional view of a disconnector device according to a second embodiment in a pristine state, i.e. before operation; and

(6) FIG. 6 shows the disconnector device of FIG. 5 after operation.

DETAILED DESCRIPTION OF THE FIGURES AND EMBODIMENTS

(7) FIG. 1 shows together with FIG. 3 a first embodiment of a disconnector device 10 for a surge arrester. The disconnector device 10 has a housing unit 14, comprising an inner housing 15 and an outer housing 16 that extends about the inner housing 15. A gap 17 is provided between the inner housing 15 and the outer housing 16. FIG. 1 shows just one halve of the housing unit 14. The halves of the housing unit 14 are connected to one another at a flange portion 18 by a bolt-nut connection, by fusion, riveting or other suitable connection means. The housing unit is made of an insulating material, such as a polymeric material.

(8) The inner housing 15 delimits a cavity 20 where a disconnector unit 25 is provided. The disconnector unit 25 has a first terminal 30, which protrudes out of the housing unit 14. The first terminal 30 is designed to be fastened to a surge arrester (not shown). A second terminal 35 of the disconnector unit is connectable to ground potential 37, for example by way of an electrical cable 36 that is advantageous because of its flexibility. A disconnector cartridge 26 is provided between the first terminal 30 and the second terminal 35 of the disconnector unit 25 in a pristine state of the disconnector unit 25, i.e. before operation of the disconnector device. A movable member 40 is connected to the second terminal 35 of the disconnector unit 25. The movable member is fitted to the cross section of the cavity 20 such that it is guided like a piston within the cylindrical cavity 20. This is achieved by a rim 50 of the movable member 40 matching the shape and the size of the cross-section of the cavity 20 such that it acts as a slider geometry such that the movable member 40 can move freely inside the cavity 20 along a longitudinal axis 19.

(9) When the disconnector unit 25 operates in case of a current overload in the conductive pathway between the first terminal 30 and the second terminal 35 connected to ground, the disconnector cartridge 26 rapidly heats up and causes the disconnector unit 25 to break apart due to the developing hot gas, which is produced by the disconnector cartridge 26 and interrupt the current path between the first terminal 30 and the second terminal 35. The technology of disconnector cartridges is well known. The disconnector cartridge 26 is a charge comprising a varistor element formed by a SiC-block and a blank cartridge that is designed such that it superheats and operate by igniting the blank cartridge by temperature before the dedicated surge arrester 140 forming a further varistor superheats such that it reaches its thermal limit and fails.

(10) Consequently, the movable member 40 together with the second terminal 35 is propelled inside the cavity 20 by the developing gas from the cartridge 26 towards a lower end 45 of cavity 20 shown in FIG. 1.

(11) The cross-section of the movable member 40 and of the cavity 20 is hexagonal when seen in the direction of the longitudinal axis 19.

(12) Adjacent to the end 45 of cavity 20 there is a retaining section 60 provided for retaining the rim 50 of the movable member 40 in its end position at the lower end 45 of the cavity 20 is formed by an annular protrusion 48 on the inner wall of the inner housing. The cross-section of said annular protrusion 48 is slightly deformable and has a conical shoulder 21 that allows the rim 50 of the movable member 40 to slide over it from the initial position 31 to the end position 32 and a stop shoulder 22 that reliably and permanently prevents the rim 50 of the movable member 40 from moving back to its initial position.

(13) In FIG. 1 the electric conduction path between the first terminal 30 and the second terminal 35 is not yet interrupted and leads via the electrically conductive disconnector cartridge 26.

(14) In FIG. 2, the status of the disconnector device 10 known from FIG. 1 is shown in a state after operation of the disconnector device 10. The movable member 40 has been propelled by the developing gas pressure from the operating disconnector unit 25 together with the second terminal 35 towards the end 45 of the cavity 20. The first terminal 30 and the second terminal 35 are displaced from one another by a predeterminable insulating distance such that the electric conduction path between the first terminal 30 and the second terminal 35 is interrupted. Since the disconnector cartridge 26 has vanished, i.e. its structure was dissolved during the operation of the disconnector unit 25.

(15) In FIG. 2, the movable member 40 is located at the end 45 of cavity 20 and secure against any movement back to its initial position by the stop shoulder 22 of the protrusion 48. At the same time, the cavity 20 is effectively closed, with the exception of ventilation openings described further below. Thus, hot solid particles from the operating disconnector unit 25 are kept inside the cavity 20, and thus inside the housing 15.

(16) The housing is designed to achieve different functions: It defines together with the movable member 40 a confined variable volume of the cavity 20, that makes use of the blasting energy of the disconnector cartridge 26 to provide a pressure build-up, which is suitable to cause a parting speed of the first terminal 30 (fixed) and the second terminal 35 (connected to the propelled movable member and to ground potential 37) which is high enough to interrupt the overload current. Further, by the retaining of the movable member 40, a subsequent restrike after current zero is avoided. The insulation distance between the first terminal 30 and the second terminal 35 is sufficient to prevent an undesired re-arcing in case of an overload.

(17) In embodiments, the housing 15 has an opening 55 (see FIG. 1) located in the end 45 of the cavity 20. The movable member 40 and the opening 55 are adjusted to each other, such that after operation of the disconnector unit 25, a part of the movable member 40 fits into the opening 55 and thereby closes it. Exemplarily, this is shown in FIG. 1 and FIG. 2, while in the latter, the closed status after operation of the disconnector unit is shown. Thereby, the part of the movable member 40 protruding through the opening 55 is visible from an outside of the housing 15 by a human observer. In order to make the operated status more easily detectable by an observer, at least the part of the movable member 40 protruding through the opening 55 (see FIG. 2) may have a signal color, for example red or orange. There is only a small circumferential gap between the opening 55 and the tubular section 42, for example having a size from 0.1 mm to 5 mm, more typically from 0.5 mm to 3.5 mm.

(18) As shown in FIG. 1 and FIG. 2 along with FIG. 3, the inner housing 15 has a plurality of ventilation openings 65 connecting the cavity 20 to the gap 17 outside the inner housing 15. The outer housing 16 has a plurality of further ventilation openings 66 connecting the gap 17 to an outside of the disconnector device 10. The ventilation openings 65 and the further ventilation openings 66 are displaced against one another such that a labyrinth 67 for the gases from the operating disconnector cartridge 26 is formed on their way out of the cavity 20, i.e. on their gas escape path 68. FIG. 3 is a simplified cross-sectional view through the housing unit 14 without the movable member 40 such that the opening 55 at the bottom of the housing unit 14 is visible.

(19) The ventilation openings 65 as well as the further ventilation openings 66 are slots having a slot-like shape extending in the direction of the longitudinal axis 19. The effect of the ventilation openings 65 is that the decrease of the gas pressure inside cavity 20 is promoted, while the movable member 40 moves towards the end 45 of the cavity 20.

(20) In the embodiments depicted in FIGS. 1 and 2, the movable member 40 has the shape of a cup with a protruding rim 50, having a hexagonal cross section at least at a portion with the largest diameter. FIG. 1 discloses that the disconnector device 10 encompasses the disconnector cartridge 26 at least partly. In this manner, the volume between the first terminal 30 and the movable member 40 is designed such that is forms a significant part taken up by the disconnector cartridge 26. This ensures a very high acceleration when the movable member 40.

(21) The first terminal 30 of the disconnector unit 25 is in some embodiments mounted to the housing 15 by screwing. That is, where the first terminal extends through the housing unit 14, the housing has an inner thread fitting an outer thread on the first terminal 30.

(22) FIG. 4 shows an overload protection assembly 11 with a disconnector device 10 that is electrically connected to a high voltage surge arrester 140. A first terminal 141 of the surge arrester 140 is electrically connectable to an electrical grid line 139. The first terminal 30 of the disconnector device 10 is electrically connected to a second terminal 142 of the high voltage surge arrester 140. The second terminal 35 of the disconnector device 10 is electrically connectable to ground potential 37 via a flexible ground cable 36. A bracket 143 is provided for mechanically fastening the overload protection assembly 11 to a structure such as a mast or pylon in an electrically insulated manner.

(23) The overload protection assembly 11 works as follows. When the surge arrester 140 enters its conductive state once a predetermined threshold current is exceeded due to an over voltage fault, the resulting high current flows from the electrical grid line 139 through the surge arrester 140 and the disconnector device 10 towards ground. While it flows through disconnector unit 25 in an initial state of the overload, the disconnector cartridge 26 operates after a predetermined time span that is determined by the current flowing and the characteristics of the disconnector cartridge 26. Next, the disconnector unit 25 operates, while producing a volume of hot gas as well as some solid residues that are typically very hot. The resulting fast rise of the pressure in the cavity 20 propels the movable member 40 towards the end 45 of the cavity. At the same time, the current flow between the surge arrester 140 and ground connected via the second terminal 35 to the disconnector device 10 is interrupted. By safely retaining the movable member 40 at the end of the cavity 20, and thus in a position distant to the first terminal, the risk of an undesired secondary arc ignition is eliminated and the overload problem is dissolved. Once the disconnector device 10 was operated, it has to be replaced because its disconnector cartridge 26 was consumed in the operating state.

(24) A second embodiment of a disconnector device 100 is shown and described with respect to FIG. 5 and FIG. 6. Said second embodiment of a disconnector device 100 has basically the same working principle as the one described with respect to FIGS. 1 and 2. Hence, only the differences of the second embodiment compared to the first embodiment shall be discussed hereinafter whereas identical or at least functionally identical elements are provided with the same reference characters. FIG. 5 shows the disconnector device 100 in its pristine state, i.e. before operation whereas FIG. 6 shows it in its state after operation.

(25) Please note that in the second embodiment of the disconnector device, the display of the outer housing 16 is there and arranged in the same fashion as shown in FIG. 3 but is not displayed in FIGS. 5 and 6 to keep the figures as simple as possible.

(26) In the second embodiment, the cavity 20 in the inner housing 15 as well as the movable member 41 have a circular cross section. The rim 50 of the movable member 41 is longer in the direction of the longitudinal axis for easing the travel from the first position to an end position. The movable member 41 is again cup shaped and encompasses the disconnector cartridge 26 laterally and axially towards the lower end 45 of the cavity 20.

(27) The tubular section 42 has a smaller diameter than the cup-shaped portion of the movable member 41. The diameter of the tubular section 42 and the diameter of the opening 55 are adjusted to each other such that the tubular section 42 can move freely in the opening 55. Again, there is only a small circumferential gap between the opening 55 and the tubular section 42, for example having a size from 0.1 mm to 5 mm, more typically from 0.5 mm to 3.5 mm. Once the disconnector cartridge 26 operates and the movable member 41 is propelled towards the end 45 of cavity 20, the movement of the movable member 41 is guided twofold, once by the rim 50 and the inner wall of the inner housing 15 and once by the diameter of the tubular section 42 and the opening 55.

(28) In yet another embodiment of the disconnector device (not shown) forming a variation to the second embodiment 100, the cylindrical wall of the inner housing 15 has no ventilation openings 65. The gas escape path 68 leads through a first annular gap between the rim 50 of the movable member 41 and through a second annular gap between the tubular section 42 of the movable member 41 and the opening 55 of the housing unit 14. Thus, hot particles from the operating disconnector unit 25 are again kept inside the cavity 20, and thus inside the housing unit 14 as the first annular gap and the second annular gap form the labyrinth.

(29) This written description uses examples to disclose the invention, including the best mode, and to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. While various specific embodiments have been disclosed in the foregoing, those skilled in the art will recognize that the spirit and scope of the claims allows for equally effective modifications. Especially, mutually non-exclusive features of the embodiments described above may be combined with each other. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.