Arrester for Protection Against Overvoltages

Abstract

An arrester such as an arrester for protection against overvoltages is disclosed. In an embodiment an arrester includes a housing configured to act as an external electrode, a central electrode arranged completely within an inner region of the housing, a discharge region arranged between the central electrode and the housing, a ceramic body separating the housing and the central electrode, wherein the ceramic body is arranged in an offset manner relative to the discharge region and a shielding element arranged on an inside of the housing, and wherein the shielding element extends over an entire longitudinal extent of the central electrode along the inside of the housing.

Claims

1-14. (canceled)

15. An arrester comprising: a housing configured to act as an external electrode; a central electrode arranged completely within an inner region of the housing; a discharge region arranged between the central electrode and the housing; a ceramic body separating the housing and the central electrode; wherein the ceramic body is arranged in an offset manner relative to the discharge region; and a shielding element arranged on an inside of the housing, wherein the shielding element extends over an entire longitudinal extent of the central electrode along the inside of the housing.

16. The arrester according to claim 15, further comprising a coupling element, wherein the ceramic body comprises an aperture, and wherein the coupling element passes through the aperture into the inner region of the housing.

17. The arrester according to claim 16, wherein the coupling element is soldered to the central electrode.

18. The arrester according to claim 16, wherein the coupling element comprises an end region which protrudes from the housing and from the ceramic body, and wherein the end region comprises a screw thread.

19. The arrester according to claim 16, wherein the coupling element comprises a central region, wherein the central region has a larger diameter than a connection region via which the coupling element is connected to the central electrode, and wherein the coupling element is connected to the ceramic body via the central region.

20. The arrester according to claim 15, further comprising a ceramic element, wherein the ceramic element is arranged between the ceramic body and the central electrode.

21. The arrester according to claim 20, wherein the ceramic element is spaced from the central electrode and fastened to the shielding element.

22. The arrester according to claim 20, wherein the ceramic element rests directly on a partial region of the inside of the housing.

23. The arrester according to claim 20, wherein the ceramic element has a step, wherein the step is formed circumferentially on a surface of the ceramic element.

24. The arrester according to claim 16, further comprising an ignition aid, wherein the ignition aid is formed on an inner wall of the aperture of the ceramic body.

25. The arrester according to claim 24, wherein the ignition aid is arranged parallel to a longitudinal axis of the arrester.

26. The arrester according to claim 24, wherein the ignition aid comprises graphite strips.

27. The arrester according to claim 15, wherein the ceramic body comprises an end region facing away from the central electrode, wherein the end region is arranged outside the housing, and wherein a gradation is formed on the end region.

28. The arrester according to claim 27, wherein the gradation is formed circumferentially around an edge region of an aperture.

29. An arrester comprising: a housing configured to act as an external electrode; a central electrode arranged completely within an inner region of the housing; a discharge region arranged between the central electrode and the housing; a ceramic body separating the housing and the central electrode, wherein the ceramic body is arranged in an offset manner relative to the discharge region; a shielding element, wherein the shielding element is arranged on an inside of the housing, and wherein the shielding element extends over an entire longitudinal extent of the central electrode along the inside of the housing; and a ceramic element, wherein the ceramic element located between the ceramic body and the central electrode, and wherein the ceramic element is fastened to the shielding element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described below are not to be interpreted as being true to scale; rather, in individual dimensions the representations may have been represented in enlarged, reduced or even distorted manner.

[0025] FIG. 1a shows a sectional representation of an arrester for protection against overvoltages, according to the state of the art;

[0026] FIG. 1b shows a perspectival view of the arrester according to FIG. 1a;

[0027] FIG. 2a shows a sectional representation of an arrester for protection against overvoltages, according to the state of the art;

[0028] FIG. 2b shows a perspectival view of the arrester according to FIG. 2a;

[0029] FIG. 3a shows a sectional representation of an arrester for protection against overvoltages; and

[0030] FIG. 3b shows a perspectival view of the arrester according to FIG. 3a.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0031] FIGS. 1a, 1b, 2a and 2b show arresters 1, 10 for protection against overvoltages, according to the state of the art. The arresters 1, 10 represented in FIGS. 1b and 2b are to be regarded as being true to scale.

[0032] The conventional structural design of surge arresters includes two electrodes 2, 3 (FIG. 1a) or 11, 12 (FIG. 2a) which are positioned either coaxially or against one another. Furthermore, in each instance a ceramic body 4, 13 is provided as insulator or spacer between the electrodes.

[0033] At high current loads (for example, wave 10/350 s, currents up to 100 kA), a vapor deposition of conducting electrode material occurs on an inner wall of the ceramic body 4, 13. This leads to a reduction of the insulation resistance of the arrester 1, 10. Under certain circumstances, impermissibly high leakage currents arise as a result in the course of operation at rated AC voltage.

[0034] The arrester 30 described in connection with FIGS. 3a and 3b solves the problems described above by exhibiting a better protection of the ceramic inner wall and an improvement of the insulation resistance after loading.

[0035] The arrester 30 exhibits a housing 31. The housing 31 serves for receiving further components of the arrester 30. At the same time, the housing also acts as an external electrode. The housing 31 preferentially features copper.

[0036] In a first end region 43 the housing 31 exhibits a coupling element 42, for instance a screw thread. The coupling element 42 has a length 52 of less than or equal to 8 mm, for instance 7 mm.

[0037] The housing 31 further exhibits a central region 45. The central region 45 serves for receiving a central electrode 33 or internal electrode, as will be described in detail later. The housing 31 further exhibits a second end region 44. The second end region 44 serves for connecting the housing 31 to an insulator or ceramic body 36, as will be described in detail later.

[0038] The first and second end regions 43, 44 each directly adjoin the central region 45. In particular, the housing 31 has preferentially been formed in one piece. The first end region 43 has a diameter that is smaller than a diameter of the central region 45 and of the second end region 44. The diameter of the second end region 44 is furthermore smaller than the diameter of the central region 45. The diameter of the central region 45 of the housing 31 is preferentially less than or equal to 20 mm, for instance 16.8 mm.

[0039] An outer surface of the central region 45 extends parallel to a longitudinal axis L of the arrester 30. An outer surface of the second end region 44, on the other hand, includes an angle with the longitudinal axis L. In other words, the second end region 44 is formed obliquely.

[0040] The housing 31 exhibits an inner region 31a. The central electrode 33 is arranged in the inner region 31a. The inner region 31a forms a discharge chamber between the housing or the external electrode 31 and the central electrode 33. The inner region 31a has a diameter 57 that is preferentially less than or equal to 15 mm, for instance 12 mm or 13 mm.

[0041] The central electrode 33 preferentially features tungsten-copper. The central electrode 33 has a diameter 55 of less than or equal to 10 mm, for instance 7.5 mm. The central electrode 33 has for instance been designed to be cylindrical.

[0042] The central electrode 33 is spaced from an inside or inner longitudinal side 31b and from an inner front side 31c of the housing 31. The inside 31b and front side 31c together constitute a wall of the inner region 31a of the housing 31.

[0043] The spacing between the central electrode 33 and the inside 31b or front side 31c preferentially amounts to up to 6 mm. A spacing 51 between a front side of the central electrode 33 and front side 31c amounts, for instance, to 5.5 mm or less.

[0044] The arrester 30 further exhibits a shielding element 32. The shielding element 32 serves to enhance the performance of the external electrode 31. In particular, the shielding element 32 protects the housing or the external electrode 31 against thermal loading. The shielding element 32 preferentially features tungsten-copper.

[0045] The shielding element 32 is formed in the inner region 31a of the housing 31. The shielding element 32 consequently reduces the diameter 57 of the inner region 31a. A diameter 56 of the inner region 31a reduced by the shielding element 32 preferentially amounts to less than or equal to 12 mm, for instance 11 mm. A thickness or radial extent (extent at right angles to the longitudinal axis L) of the shielding element 32 amounts to less than or equal to 2 mm. The shielding element 32 has been firmly connected to the housing 31, for instance by brazing or press fit.

[0046] The shielding element 32 extends on the inside 31b of the housing 31 along the longitudinal axis L of the arrester 30. A length of the shielding element 32 is such that the shielding element 32 extends along a complete length of the central electrode 33. In other words, a longitudinal extent of the shielding element 32 is greater than a longitudinal extent of the central electrode 33. In particular, the shielding element 32 extends along the complete inside 31b of the housing 31. For instance, the length of the shielding element 32 amounts to up to 20 mm, for instance 17 mm. An overall length 50 of the arrester 30 preferentially amounts to less than or equal to 50 mm, for instance 46 mm or 47 mm. In addition, the shielding element 32 may also extend at least partly on the inner front side 31c of the housing 31 (not represented explicitly).

[0047] The arrester 30 further exhibits the ceramic body or insulator 36. The arrester 30 exhibits a coupling element 34.

[0048] The ceramic body 36 serves for electrical insulation of the housing 31 and of the central electrode 33. The ceramic body 36 is arranged in the second end region 44 of the housing 31. The ceramic body 36 is consequently arranged in a manner offset from the discharge chamber which is formed between the housing 31 and the central electrode 33. Hence an insulating body directly between the housing or external electrode 31 and the central electrode 33 is dispensed with. Hence an outside diameter of the arrester 30 is reduced. For instance, the outside diameter of the arrester 30 amounts to less than or equal to 20 mm, for instance 17 mm (see also FIG. 3b, which is to be understood as a true-to-scale representation of an embodiment of the arrester 30).

[0049] The ceramic body 36 exhibits a central aperture 36a. The aperture 36a has a diameter 54 of less than or equal to 10 mm, for instance 8.5 mm. The aperture 36a serves for feeding the coupling element 34 through into the inner region 31a. The coupling element 34 will be described in detail later.

[0050] The ceramic body 36 is firmly connected to the housing 31. For instance, the ceramic body 36 and the housing 31 have been soldered together. The ceramic body 36 has been soldered to the housing 31, in particular in a soldering region 38 in the end region 44 of the housing 31.

[0051] For this purpose, the ceramic body 36 exhibits a specially shaped first end region. The first end region faces toward the housing 31. The first end region exhibits a step. The step is formed circumferentially. The step serves as stop surface for the end region 44, and also as soldering region 38.

[0052] The ceramic body 36 further exhibits a second end region 36b. The second end region 36b faces away from the housing 31. The second end region 36b exhibits a gradation or undercut 39. The gradation 39 is formed circumferentially around the aperture 36. In other words, the gradation 39 is constituted by a bulge of the ceramic body 36, in particular of a front face of the ceramic body 36, that is formed directly adjacent to the aperture 36. The gradation 39 extends outward in the radial direction from lateral edges of the aperture 36a. The gradation 39 has a diameter 53 of less than or equal to 13 mm, for instance 11 mm. The gradation 39 serves to reduce surface-leakage currents after loading of the arrester 30.

[0053] The coupling element 34 is pin-shaped. The coupling element 34 has been firmly connectedfor instance, solderedto the central electrode 33. In particular, the coupling element 34 has been soldered to the electrode 33 in a connection region or end region 34c. In this way, the central electrode 33 becomes more resistant to the thermal loading arising during the discharge. The coupling element 34 features copper, for instance. The coupling element 34, in particular the connection region 34c, has a diameter 58 of less than or equal to 8 mm, for instance 6 mm. For the electrical contacting of the central electrode 33, the coupling element 34, in particular the connection region 34c, has been passed through the aperture 36 and into the inner region 31a.

[0054] The coupling element 34 exhibits an end region 34a which protrudes from the ceramic body 36. On the end region 34a a screw thread 41, for instance an M8 screw, is formed. A diameter of the end region 34a is larger than the diameter 58 of the connection region 34c.

[0055] The coupling element 34 has been firmly connected to the ceramic body 36, for instance by means of brazing. For this purpose, the coupling element 34 exhibits a widened central region 34b. A diameter of the central region 34b is larger than the diameter 58 of the connection region 34c and larger than the diameter of the end region 34a. The central region 34b is disk-shaped. The central region 34b directly adjoins the end region 34a. In particular, the central region 34b is arranged between the end region 34a and the connection region 34c. The central region 34b rests, at least in a partial region, directly on the ceramic body 36, in particular on a front face of the ceramic body 36.

[0056] Between the front face of the ceramic body 36 and an upper side of the central region 34b, in particular an annular outer region of the upper side, a soldering region 47 is formed for soldering the coupling element 34 and the ceramic body 36 together.

[0057] In this embodiment, the arrester 30 further exhibits a ceramic element 35, but embodiments without a ceramic element 35 are also conceivable. The ceramic element 35 is annular. In particular, the ceramic element 35 exhibits an aperture for feeding the coupling element 34 through.

[0058] The ceramic element 35 is arranged in the inner region 31a. In particular, the ceramic element 35 seals or bounds the inner region 31a of the housing in the direction of the ceramic body 36. The ceramic element 35 rests in a lateral region directly on the housing 31, in particular on the inside 31b thereof. The ceramic element 35 is arranged in the longitudinal direction of the arrester 30 between the shielding element 32 and the ceramic body 36.

[0059] The ceramic element 35 improves the shielding of the ceramic body 36 relative to the discharge chamber which is located between the housing 31 and the central electrode 33. The ceramic element 35 preferentially exhibits a step or elevation 40. The step 40 is formed circumferentially on an outer surface of the ceramic element 35, for instance on a surface of the ceramic element 35 facing toward the shielding element 32. The step 40 is designed to reduce surface-leakage currents after loading.

[0060] The ceramic element 35 has been soldered to the shielding element 32, for instance by means of brazing. For this purpose, a soldering region 46 is formed between the shielding element 32 and the ceramic element 35, in particular the step 40.

[0061] The arrester 30 further exhibits an ignition aid 37. The ignition aid 37 may exhibit a graphite strip or a plurality of graphite strips. The ignition aid 37 extends parallel to the longitudinal axis L of the arrester 30.

[0062] The ignition aid is arranged on an inner wall of the ceramic body 36. In particular, the ignition aid 37 is formed in the region of the aperture 36a and, in particular, in the region of the side walls of the aperture 36a. The ignition aid 37 serves to reduce the response voltage of the arrester 30.

[0063] The description of the subject-matters specified herein is not limited to the individual special practical forms. Rather, the features of the individual practical forms canto the extent that this is technically meaningfulbe combined arbitrarily with one another.