Arrester for surge protection
The surge arrester design with a conductive housing, ceramic insulation, and shielding element addresses insulation resistance and leakage current issues, resulting in a compact and reliable surge arrester with enhanced durability.
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Patents
- Current Assignee / Owner
- TDK ELECTRONICS AG
- Filing Date
- 2018-05-08
- Publication Date
- 2026-07-01
AI Technical Summary
Conventional gas discharge tubes suffer from reduced insulation resistance due to conductive electrode material deposition on the ceramic inner wall, leading to high leakage currents during nominal AC voltage operation, and require additional ceramic spacers which increase the arrester's size.
A surge arrester design featuring a conductive housing as the external electrode, a central electrode insulated by a ceramic body offset from the discharge space, and a shielding element to protect against thermal stress, along with a connection element and ignition aid to enhance efficiency and durability.
The design achieves improved insulation resistance, reduced leakage currents, and a compact arrester form without the need for additional ceramic spacers, ensuring high reliability and durability.
Smart Images
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Abstract
Description
[0001] A surge arrester for protection against overvoltages is described.
[0002] A surge arrester, or simply arrester, is used to limit dangerous or unwanted overvoltages in electrical lines and devices. This prevents damage to the lines and devices caused by overvoltages. Gas-filled arresters, also known as gas discharge arresters, are devices in which the overvoltage is dissipated within the gas discharge by the automatic ignition of a gas discharge. They operate on the gaseous principle of arc discharge, whereby, after reaching a surge arrester response voltage, also referred to as the trigger voltage or ignition voltage, an electric arc forms within nanoseconds in the gas-tight discharge chamber. Due to the high current-carrying capacity of the arc, the overvoltage is effectively short-circuited.
[0003] In conventional gas discharge tubes with two electrodes, the ceramic inner wall can become coated with conductive electrode material. This reduces the insulation resistance of the discharge tube. Furthermore, it can cause unacceptably high leakage currents when operating at the nominal AC voltage.
[0004] Document DE 1016354 B describes a surge arrester with a gas discharge vessel designed to be inserted or screwed into any socket. Furthermore, heating of the electrode is used to actuate a switching device.
[0005] Document CH 649176 A5 describes a surge arrester with two electrodes, the opposing central surfaces of which form a discharge space and an electrically insulating material is arranged between the outer parts of which a gas-tight interior is formed.
[0006] Document WO 2012 / 128729 A1 describes a gas discharge tube with an outer body which is also an outer electrode, a central electrode which consists of an inner part and an outer part and an insulating element, wherein inside a part of the body a cylindrical shield is arranged which occupies about one third of the inner part of the central electrode.
[0007] Document Sl 23 042 A describes a surge arrester with a metallic casing that acts as an external electrode. The arrester has an inner electrode, a primary insulating element, a secondary insulating element, and a metallic cavity. A carbon-based conductive layer is deposited on the secondary insulating element.
[0008] Document DE 10 2008 029 094 A1 describes a drain with an undercut ceramic element. This is intended to provide better protection for the inner ceramic wall.
[0009] One task to be solved is to specify a surge arrester for protection against overvoltages that has improved properties. For example, a surge arrester should be specified that is particularly reliable, compact, and / or durable.
[0010] This problem is solved by a conductor according to independent claim 1.
[0011] According to one aspect, a surge arrester is specified for protection against overvoltages. The arrester has a housing. The housing is designed to accommodate further components of the arrester within its interior. The housing can, for example, be in the form of a hollow cylinder. The housing is also designed to function as an external electrode. The housing is made of an electrically conductive material, for example, copper.
[0012] The surge arrester also has a central electrode or internal electrode. The central electrode is located entirely within the housing. A discharge space is formed between the central electrode and the housing. In other words, an arc discharge occurs between the central electrode and the housing in the event of an overvoltage. The central electrode is, for example, cylindrical in shape. The central electrode is made of an electrically conductive material, such as tungsten and / or copper.
[0013] The surge arrester also includes a ceramic body. The ceramic body serves as insulation. In particular, the ceramic body is designed and arranged to electrically separate the housing from the central electrode. Preferably, the ceramic body is in direct mechanical contact with the housing. Preferably, direct mechanical contact between the ceramic body and the central electrode is prevented, preferably by the housing. The ceramic body is arranged offset from the discharge chamber.
[0014] The electrical separation between the central electrode and the housing is coaxial, with the ceramic body acting as an insulator between the central electrode and the housing. This eliminates the need for a ceramic spacer between the electrodes of the surge arrester. Specifically, the outer electrode becomes the body / housing of the arrester. This reduces the outer diameter of the arrester. Furthermore, the inner wall of the ceramic body is optimally protected from electrode material deposition. High leakage currents during operation at the nominal AC voltage can thus be avoided.
[0015] The surge arrester also includes a shielding element. The shielding element is designed and arranged to protect the housing against thermal stress. The shielding element forms a covering for at least a portion of the housing's inner surface. The shielding element is located on the inside of the housing. The shielding element is preferably permanently connected to the housing, for example, by brazing or press fit. The shielding element extends along a longitudinal axis of the surge arrester. Furthermore, the central electrode also extends along the longitudinal axis of the surge arrester, i.e., it has a longitudinal extension. The shielding element extends over the entire longitudinal extent of the central electrode along the inside of the housing. In this way, the housing can be efficiently protected against thermal stress.In an alternative embodiment, the shielding element can also extend at least partially perpendicular to the longitudinal axis of the conductor. This allows an end face of the inner area of the housing to also be protected against thermal stress / fusion.
[0016] The arrangement described above provides a surge arrester that is not only particularly efficient and durable, but also has a small outer diameter.
[0017] According to one embodiment, the surge arrester has a connection element. The connection element is designed and arranged to electrically contact the central electrode. The connection element is made of copper, for example. The ceramic body has a hole. The hole preferably penetrates the ceramic body completely in a central region. The connection element is designed and arranged to extend at least partially through the hole into the interior of the housing.
[0018] In particular, the connecting element has a connection area. The connection area is elongated or pin-shaped. The connection area is designed to be connected to the central electrode. The connection area extends through the opening. The connecting element, especially the connection area, is soldered to the central electrode.
[0019] The connector also has an end section. This end section protrudes from the housing and the ceramic body. Specifically, the end section does not extend through the opening. The end section is designed to be connected to another electronic component or device. The end section has a thread, for example, an M8 screw.
[0020] The connecting element also has a central area.
[0021] The central section is formed between the end section and the connection section. Preferably, the connecting element is formed in one piece. In other words, the connection section, central section, and end section merge seamlessly into one another.
[0022] The connecting element is attached to the ceramic body via the central section, for example by soldering. The central section is plate- or disc-shaped. The central section has a larger diameter than the connection area. The central section has a larger diameter than the end area. The end area has a larger diameter than the connection area.
[0023] According to the invention, the surge arrester incorporates a ceramic element. This ceramic element serves as an insulator. In particular, the ceramic element is designed and arranged to further improve the shielding of the ceramic body from the discharge space. This further increases the efficiency and service life of the surge arrester.
[0024] The ceramic element is, for example, ring-shaped. For instance, the ceramic element has a ceramic disc with an opening. The opening serves to allow the connection element to pass through. The ceramic element is formed between the ceramic body and the central electrode. The ceramic element is preferably arranged at a distance from the central electrode. The ceramic element is preferably attached to the shielding element, for example, by soldering. The ceramic element, for example, a circumferential edge region of the ceramic element, preferably rests directly against a portion of the inside of the housing.
[0025] The ceramic element preferably has a step or protrusion. The step is preferably formed around a surface of the ceramic element. The step or protrusion preferably rises from an outer surface of the ceramic element facing the central electrode. The step reduces leakage currents after loading.
[0026] According to the invention, the surge arrester has an ignition aid. The ignition aid reduces the dynamic response voltage of the arrester, resulting in a highly efficient arrester. The ignition aid, for example, has graphite lines. According to the invention, the ignition aid is arranged on the ceramic body. Specifically, the ignition aid is formed on an inner wall of the opening in the ceramic body. Optionally, the ignition aid is arranged parallel to a longitudinal axis of the surge arrester.
[0027] By arranging it parallel to the longitudinal axis, a charge difference can be achieved at the end regions of the ignition aid.
[0028] According to one embodiment, the ceramic body has an end region facing away from the central electrode. This end region is located outside the housing. A step is formed at this end region. The step extends around an edge region of the opening.
[0029] The stepping improves the insulation resistance of the surge arrester.
[0030] The above will be explained in more detail below using examples.
[0031] The drawings described below are not to be considered to scale; rather, the representations may be enlarged, reduced, or distorted in individual dimensions. They show:
[0032] Figure 1a shows a sectional view of a surge arrester for protection against overvoltages according to the prior art, Figure 1b shows a perspective view of the surge arrester according to Figure 1a Figure 2a shows a sectional view of a surge arrester for protection against overvoltages according to the prior art, Figure 2b shows a perspective view of the surge arrester according to Figure 2a Figure 3a shows a sectional view of a surge arrester for protection against overvoltages; Figure 3b shows a perspective view of the surge arrester according to Figure 3a .
[0033] The Figures 1a, 1b , 2a and 2b The diagram shows surge arresters 1 and 10 for protection against overvoltages in accordance with the state of the art. The diagrams in the Figures 1b and 2b The depicted drains 1, 10 are to be regarded as true to scale.
[0034] The conventional design of surge arresters includes two electrodes 2, 3 ( Figure 1a ) or 11, 12 ( Figure 2a), which are positioned either coaxially or opposite each other. Furthermore, a ceramic body 4, 13 is provided as an insulator or spacer between the electrodes.
[0035] Under high current loads (e.g., wave 10 / 350 µs, currents up to 100 kA), a conductive electrode material is deposited on the inner wall of the ceramic body 4, 13. This leads to a reduction in the insulation resistance of the surge arrester 1, 10. Under certain circumstances, this can result in unacceptably high leakage currents when operating at the nominal AC voltage.
[0036] The one in connection with the Figures 3a and 3b The described surge arrester 30 solves the problems described above by providing better protection of the ceramic inner wall and an improvement in insulation resistance after loading.
[0037] The surge arrester 30 has a housing 31. The housing 31 serves to accommodate further components of the surge arrester 30. At the same time, the housing also functions as an external electrode. The housing 31 preferably comprises copper.
[0038] In a first end region 43, the housing 31 has a connection element 42, for example a thread. The connection element 42 has a length 52 of less than or equal to 8 mm, for example 7 mm.
[0039] The housing 31 further comprises a central region 45. The central region 45 serves to accommodate a central electrode 33 or internal electrode, as will be described in detail later. The housing 31 further comprises a second end region 44. The second end region 44 serves to connect the housing 31 to an insulator or ceramic body 36, as will be described in detail later.
[0040] The first and second end sections 43, 44 each adjoin the central section 45 directly. In particular, the housing 31 is preferably formed in one piece. The first end section 43 has a diameter that is smaller than the diameter of the central section 45 and the second end section 44. The diameter of the second end section 44 is also smaller than the diameter of the central section 45. The diameter of the central section 45 of the housing 31 is preferably less than or equal to 20 mm, for example 16.8 mm.
[0041] An outer surface of the middle section 45 runs parallel to a longitudinal axis L of the conductor 30. An outer surface of the second end section 44, however, forms an angle with the longitudinal axis L. In other words, the second end section 44 is inclined.
[0042] The housing 31 has an inner chamber 31a. The central electrode 33 is arranged in the inner chamber 31a. The inner chamber 31a forms a discharge space between the housing / outer electrode 31 and the central electrode 33. The inner chamber 31a has a diameter 57, which is preferably less than or equal to 15 mm, for example 12 mm or 13 mm.
[0043] The central electrode 33 preferably comprises tungsten-copper. The central electrode 33 has a diameter 55 of less than or equal to 10 mm, for example 7.5 mm. The central electrode 33 is, for example, cylindrical.
[0044] The central electrode 33 is spaced apart from an inner side 31b and an inner end face 31c of the housing 31. The inner side 31b and the end face 31c together form a wall of the inner region 31a of the housing 31.
[0045] The distance between the central electrode 33 and the inner surface 31b or end face 31c is preferably up to 6 mm. A distance 51 between an end face of the central electrode 33 and the end face 31c is, for example, 5.5 mm or less.
[0046] The surge arrester 30 further comprises a shielding element 32. The shielding element 32 serves to increase the performance of the outer electrode 31. In particular, the shielding element 32 protects the housing / outer electrode 31 from thermal stress. The shielding element 32 preferably comprises tungsten-copper.
[0047] The shielding element 32 is formed in the inner region 31a of the housing 31. The shielding element 32 thus reduces the diameter 57 of the inner region 31a. The diameter 56 of the inner region 31a reduced by the shielding element 32 is preferably less than or equal to 12 mm, for example 11 mm. The thickness or radial extent (extent perpendicular to the longitudinal axis L) of the shielding element 32 is less than or equal to 2 mm. The shielding element 32 is firmly connected to the housing 31, for example by brazing or press fit.
[0048] The shielding element 32 extends along the inner surface 31b of the housing 31 along the longitudinal axis L of the surge arrester 30. The length of the shielding element 32 is such that it extends along the entire length of the central electrode 33. In other words, the longitudinal extent of the shielding element 32 is greater than the longitudinal extent of the central electrode 33. In particular, the shielding element 32 extends along the entire inner surface 31b of the housing 31. For example, the length of the shielding element 32 is up to 20 mm, for example, 17 mm. The overall length 50 of the surge arrester 30 is preferably less than or equal to 50 mm, for example, 46 mm or 47 mm. Additionally, the shielding element 32 can also extend at least partially along the inner end face 31c of the housing 31 (not explicitly shown).
[0049] The surge arrester 30 further comprises the ceramic body or insulator 36. The surge arrester 30 has a connection element 34.
[0050] The ceramic body 36 serves as electrical insulation between the housing 31 and the central electrode 33. The ceramic body 36 is located in the second end region 44 of the housing 31. Consequently, the ceramic body 36 is positioned offset from the discharge space formed between the housing 31 and the central electrode 33. This eliminates the need for an insulating body directly between the housing / outer electrode 31 and the central electrode 33. This reduces the outer diameter of the arrester 30. For example, the outer diameter of the arrester 30 is less than or equal to 20 mm, for example, 17 mm (see also [reference]). Figure 3b , which is to be understood as a scale representation of an embodiment of the drain 30).
[0051] The ceramic body 36 has a central opening 36a. The opening 36a has a diameter 54 of less than or equal to 10 mm, for example, 8.5 mm. The opening 36 serves to allow the connecting element 34 to pass into the interior space 31a. The connecting element 34 will be described in detail later.
[0052] The ceramic body 36 is firmly connected to the housing 31. For example, the ceramic body 36 and the housing 31 are soldered together. In particular, the ceramic body 36 is soldered to the housing 31 in a soldering area 38 in the end region 44 of the housing 31.
[0053] For this purpose, the ceramic body 36 has a specially shaped first end region. The first end region faces the housing 31. The first end region has a step. The step is formed around the entire circumference. The step serves as a stop surface for the end region 44 and as a soldering area 38.
[0054] The ceramic body 36 further comprises a second end region 36b. The second end region 36b faces away from the housing 31. The second end region 36b has a step or undercut 39. The step 39 is formed around the opening 36. In other words, the step 39 represents a protrusion of the ceramic body 36, in particular of an end face of the ceramic body 36, which is formed directly adjacent to the opening 36. The step 39 extends radially outwards from the side edges of the opening 36a. The step 39 has a diameter 53 of less than or equal to 13 mm, for example, 11 mm. The step 39 serves to reduce leakage currents after the arrester 30 is loaded.
[0055] The terminal element 34 is pin-shaped. The terminal element 34 is firmly connected to the central electrode 33, for example, by soldering. In particular, the terminal element 34 is soldered to the electrode 33 in a connection or end region 34c. This makes the central electrode 33 more resistant to the thermal stress occurring during discharge. The terminal element 34 is made of copper, for example. The terminal element 34, in particular the connection region 34c, has a diameter 58 of less than or equal to 8 mm, for example, 6 mm. For electrical contact with the central electrode 33, the terminal element 34, in particular the connection region 34c, is guided through the opening 36 and into the inner region 31a.
[0056] The connecting element 34 has an end region 34a which projects from the ceramic body 36. A thread 41, for example an M8 screw, is formed on the end region 34a. The diameter of the end region 34a is larger than the diameter 58 of the connection region 34c.
[0057] The connecting element 34 is firmly connected to the ceramic body 36, for example by brazing. For this purpose, the connecting element 34 has a widened central region 34b. The diameter of the central region 34b is larger than the diameter 58 of the connection region 34a and larger than the diameter of the end region 34a. The central region 34b is disc-shaped. The central region 34b adjoins the end region 34a directly. In particular, the central region 34b is arranged between the end region 34a and the connection region 34c. The central region 34a rests directly against the ceramic body 36, in particular an end face of the ceramic body 36, at least in a partial area.
[0058] A soldering area 47 is formed between the end face of the ceramic body 36 and a top surface of the central area 34a, in particular an annular outer surface of the top surface, for soldering the connecting element 34 and the ceramic body 36.
[0059] In this embodiment, the surge arrester 30 further comprises a ceramic element 35. However, embodiments without a ceramic element 35 are also conceivable. The ceramic element 35 is ring-shaped. In particular, the ceramic element 35 has an opening for the passage of the connecting element 34.
[0060] The ceramic element 35 is arranged in the inner area 31a. In particular, the ceramic element 35 closes off or limits the inner area 31a of the housing in the direction of the ceramic housing 36. The ceramic element 35 rests directly against the housing 31 in a side area, in particular against its inner side 31b. The ceramic element 35 is arranged longitudinally along the current collector 30 between the shielding element 32 and the ceramic housing 36.
[0061] The ceramic element 35 improves the shielding from the ceramic body 36 to the discharge space located between the housing 31 and the central electrode 33. Preferably, the ceramic element 35 has a step or protrusion 40. The step 40 is formed circumferentially on an outer surface of the ceramic element 35, for example, a surface of the ceramic element 35 facing the shielding element 32. The step 40 is designed to reduce leakage currents after the load has been applied.
[0062] The ceramic element 35 is soldered to the shielding element 32, for example by brazing. For this purpose, a soldering area 46 is formed between the shielding element 32 and the ceramic element 35, in particular the step 40. The surge arrester 30 also has an ignition aid 37. The ignition aid 37 can have one or a plurality of graphite lines. The ignition aid 37 runs parallel to the longitudinal axis L of the surge arrester 30.
[0063] The ignition aid is arranged on an inner wall of the ceramic body 36. In particular, the ignition aid 37 is formed in the area of the opening 36a and especially in the area of the side walls of the opening 36a. The ignition aid 37 serves to reduce the response voltage of the arrester 30.
[0064] The description of the items listed here is not limited to the individual specific designs. Reference symbol list
[0065] 1. Current collector 2. First electrode 3. Second electrode 4. Ceramic body 10. Arrester 11. First electrode 12. Second electrode 13. Ceramic body 30 Surge arrester 31 Housing / outer electrode 31a Inner area 31b Inner side / inner longitudinal side 31c End face 32 Shielding element 33 Inner electrode / central electrode 34 Connection element 34a End area 34b Middle area 34c Connection area 35 Ceramic element 36 Ceramic body 36a Breakout 36b End area 37 Ignition aid 38 Soldering area 39 Step 40 Step 41 Thread 42 Connection area 43 First end area 44 Second end area 45 Middle area 46 Soldering area 47 Soldering area 50 Total length 51 Spacing 52 Length 53 Diameter 54 Diameter 55 Diameter 56 Diameter 57 Diameter 58 Diameter Longitudinal axis
Claims
1. Arrester (30) for protection against overvoltages, having: - a housing (31), wherein the housing (31) acts as an external electrode, - a central electrode (33), wherein the central electrode (33) is arranged completely in an inner region (31a) of the housing (31), and wherein a discharge space is formed between the central electrode (33) and the housing (31), - a ceramic body (36) for electrical isolation of the housing (31) and the central electrode (33), wherein the ceramic body (36) is arranged offset with respect to the discharge space, - a shielding element (32), wherein the shielding element (32) is arranged on an inner side (31b) of the housing (31) and wherein the shielding element (32) extends over an entire longitudinal extent of the central electrode (33) along the inner side (31b) of the housing (31), - a ceramic element (35), wherein the ceramic element (35) is formed between the ceramic body (36) and the central electrode (33), - a terminal element (34), wherein the ceramic body (36) has a perforation (36a), and wherein the terminal element (34) extends through the perforation (36a) into the inner region (31a) of the housing (31), - an ignition aid (37), wherein the ignition aid (37) is formed on an inner wall of the perforation (36a) of the ceramic body (36).
2. Arrester (30) according to claim 1, wherein the terminal element (34) is soldered to the central electrode (33).
3. Arrester (30) according to any one of the preceding claims, wherein the terminal element (34) has an end region (34a) protruding from the housing (31) and the ceramic body (36), and wherein the end region (34) has a thread (41).
4. Arrester (30) according to any one of the preceding claims, wherein the terminal element (34) has a central region (34b), wherein the central region (34b) has a larger diameter than a connection region (34c), via which the terminal element (34) is connected to the central electrode (33), and wherein the terminal element (34) is connected to the ceramic body (36) via the central region (34b).
5. Arrester (30) according to any one of the preceding claims, wherein the shielding element (32) comprises tungstencopper.
6. Arrester (30) according to any one of the preceding claims, wherein the ceramic element (35) is arranged in a manner spaced apart from the central electrode (33) and is secured to the shielding element (32).
7. Arrester (30) according to any one of the preceding claims, wherein the ceramic element (35) bears directly on a partial region of the inner side (31b) of the housing (31).
8. Arrester (30) according to any one of the preceding claims, wherein the ceramic element (35) has a step (40), wherein the step (40) is formed circumferentially on a surface of the ceramic element (35).
9. Arrester (30) according to any one of the preceding claims, wherein the ignition aid (37) is arranged parallel to a longitudinal axis (L) of the arrester (30).
10. Arrester (30) according to any one of the preceding claims, wherein the ignition aid (37) has graphite strips.
11. Arrester (30) according to any one of the preceding claims, wherein the ceramic body (36) has an end region (36b) facing away from the central electrode (33), wherein the end region (36b) is arranged outside the housing (31), and wherein a gradation (39) is formed at the end region (36b).
12. Arrester (30) according to claim 11, wherein the gradation (39) is formed circumferentially around an edge region of the perforation (36a).