EP0037363A1 - Over voltage arrester - Google Patents

Abstract

Disclosed are overvoltage arresters comprising a columnar arrangement of arrester elements, insulating elements and conducting elements. The elements are arranged to provide a current flow in at least one plane extending transversely to the columns. The conducting frame elements connect other elements thereto which elements extend both axially and transversely of the columns. For an arrester including n conducting frame members per plane, n-1 arrester elements are arranged per plane of the columnar structure. The current connection between adjacent plane is made by an arrester element or by a conducting member preferably such that opposite current flows are obtained in adjacent planes. Overvoltage arresters according to the invention are particularly suited for using voltage-dependent resistors of the zinc oxide type alone or in conjunction with spark gaps. The columnar structure may be disposed in a customary insulating gas such as nitrogen or in a gas with particularly high insulating strength such as SF6.

Description

• a) Anordnung von Ableiterelementen in Ebenen senkrecht zur Längserstreckung eines mehrere parallele Säulen aufweisenden Gerüstes; .
• b) einheitliche Abmessungen der Ableiterelemente sowie von isolierenden Stützkörpern und leitenden Gerüstelementen.

The invention relates to a surge arrester with the following features:

• a) arrangement of arrester elements in planes perpendicular to the longitudinal extent of a scaffold having a plurality of parallel columns; .
• b) uniform dimensions of the arrester elements and of insulating support bodies and conductive scaffolding elements.

A surge arrester of this type has become known from CH-PS 304 299. In this case, the arrester elements are arranged alternately in one of the columns in a plane running perpendicular to the longitudinal axis of the columns as a connection between two columns and then again as an element of another column. This results in an overall helical course with a saving in axial length.

The object of the invention is to enable a further substantial increase in the packing density of the arrester elements. In this way, surge arresters in particular for high operating voltages, for. B. 500 kV, can be created, which can be inserted into metal-enclosed, pressurized gas-insulated switchgear without difficulty, but are also suitable for outdoor installation.

• c) jedes leitende Gerüstelement Anschluß- und Verbindungsmittel in Richtung der weiteren Säulen besitzt und daß
• d) bei n Gerüstelementen je Ebene wenigstens (n-1) Ableiterelemente vorhanden sind.

This object is achieved with a surge arrester of the type mentioned in that

• c) each conductive scaffold element has connection and connection means in the direction of the further columns and that
• d) with n scaffolding elements per level there are at least (n-1) arrester elements.

In this way, z. B. accommodate three arrester elements in a four-column structure in each level. If one now chooses a version in which the levels are connected by a diverter element, one arrives at a surge arrester which is suitable for arrangement in air or the nitrogen which is frequently used in conventional surge arresters.

Within the scope of the invention, however, a conductive support body can be used to connect the scaffolding elements of two adjacent levels. This allows the distance between the levels to be reduced and the structure becomes much more compact. This arrangement is particularly suitable for installation in electronegative gas under pressure, for. B. SF ₆ , and enables the construction of arresters with favorable dimensions, as are desired for metal-enclosed switchgear.

In both designs described, the arrangement of a diverter element or a conductive support body between the levels, which changes from level to level, ensures that the flow direction of the current changes from level to level. The inductance of the overall arrangement thus becomes a minimum. The same property can also be achieved in a modified design in which arrester elements connected in parallel are present in the individual levels.

The structure provided in the invention with in-plane arrester elements, which are connected via scaffolding elements, offers the advantageous possibility of using control elements, such as. B. linear or non-linear control resistors and capacitors, to be included as required. For this purpose, n-1 arrester elements and a control element can be arranged in each level, the control element being connected between the current supply and discharge lines of each level. In this way, a chain of control elements connected in parallel to the arrester elements is created to equalize the voltage distribution. In addition, the control element completes the triangular, rectangular or polygonal shape of the planes in such a way that an increase in mechanical strength is achieved. If, on the other hand, it is only a question of increasing the strength, an insulating support body with the dimensions of an arrester element can also be inserted in each plane instead of a control element.

In the context of the invention, the scaffolding elements can be designed as hollow bodies. In the case of an embodiment with a pot-shaped main part and a cover, the modular construction of the arrester gives good access to the cavity and, if appropriate, fastening elements to be attached there.

In addition, the cavity of the scaffolding elements can be used as a collecting space for gases which can arise as a result of the thermal decomposition of arrester elements if the surge arrester is overloaded. To this end, in a further development of the invention, the interior spaces of the arrester elements can be connected to the cavities of the scaffolding elements and these can be connected to the surrounding atmosphere through a pressure compensation opening. This arrangement, the z. B. by hollow or tubular support body between the arrester elements and the scaffold elements is particularly suitable for surge arresters with a housing that is to be protected against sudden pressure when the arrester is overloaded. The hot gases first fill the cavities of the scaffolding elements before they dampen the housing with a time delay.

In the case of surge arresters with a housing, the arrangement just described can be made even more effective in that the cavities of the scaffolding elements can be connected to the atmosphere surrounding the housing by means of a crushing membrane when an inadmissible overpressure occurs. In this case, there is no pressure on the housing or any contamination. It can therefore be used again after the defective arrangement of arrester elements has been removed.

The invention is explained in more detail below with reference to the exemplary embodiments shown in the figures.

Fig. 1 shows a perspective view of the internal structure of a surge arrester for outdoor installation.

2 also shows in perspective the internal structure of a surge arrester for a compressed gas-insulated, metal-enclosed switchgear.

3 shows a scaffolding element as an individual part.

A parallel connection of arrester elements is shown schematically in FIG. 4.

5 and 6 show a section of a column structure of arrester elements, one for receiving each Gas-compatible scaffolding element with the adjacent arrester elements.

Fig. 7 shows a section through an encapsulated surge arrester with crushing membranes.

The surge arrester 1 shown in FIG. 1 comprises a housing 2 which is designed as a hollow porcelain insulator with shields. In the interior of the housing, a four-pillar structure of arrester elements is arranged between support plates 3 and 4, which are connected to a voltage-side connection 5 or an earth connection 6. Each of the columns 10, 11, 12 and 13 is composed of arrester elements 14, insulating support bodies 15 and framework elements 16 in a specific order. The arrester elements 14 and the insulating support body 15 have the same length, so that these elements can be combined as desired.

In the surge arrester 1 shown in FIG. 1, starting from the voltage connection 5, there follows first a conductor element 14 in the course of the column 10. The further columns 11, 12 and 13 contain insulating support bodies 15 at the same height. In the following, perpendicular to the longitudinal axis of the column-extending plane are then in a U-shaped arrangement three further arrester elements 14, which are connected to one another by frame elements 16 in a conductive and load-bearing manner. The open side of the U-shape is located between the columns 10 and 11. In the course of the column 11, the connection to the lower level is then likewise established via a scaffold element 16 by means of a conductor element 14, in which the current path through further conductor elements 14 is reversed Direction as in the upper level. Another conductor element 14 located in the course of the column 10 establishes the connection with the lower support plate 4, which is connected to the earth connection. The other columns contain insulating supporting bodies of the same dimensions, parallel to the lowermost conductor element 14.

The mentioned arrester elements 14 are preferably voltage-dependent resistors based on zinc oxide. The actual resistance body is surrounded by an insulating housing, the dimensions of which are adapted to the insulating support bodies. The high mechanical strength of the zinc oxide resistors also makes it possible to dispense with separate insulating housings. In this case, the resistors are connected directly to the scaffolding elements using suitable connection fittings which are fixedly attached to the resistance body. The elimination of the insulating housing increases the volume of the resistance material to be accommodated and improves its cooling.

Instead of a series connection of voltage-dependent resistors, a series connection of spark gaps with voltage-dependent resistors can also be provided. This can e.g. B. happen that one or more of the arrester elements 14 in Fig. 1 are designed as spark gaps. The spark gaps do not need their own gas-tight encapsulation if the structure shown in FIG. 1 is arranged within the housing 2 in an atmosphere which leads to the desired mode of operation of the spark gaps. In a known manner, this can be achieved by filling the housing 2 with nitrogen.

FIG. 2 shows a further exemplary embodiment of a surge arrester. Similar to FIG. 1, a column structure with four columns 20, 21, 22 and 23 is again selected, which are arranged in the corner points of a square. Likewise, by means of scaffolding elements 24, insulating support body 25 and conductive support body 26 and arrester elements 27 have a uniform structure with a number of planes lying perpendicular to the longitudinal axis of the columns. In contrast to the exemplary embodiment according to FIG. 1, however, no arrester elements are used in the longitudinal direction of the columns, that is to say to connect the planes to one another, but instead only insulating support bodies 25 and conductive support bodies 26 are used alternately. These support bodies are smaller than the corresponding parts in the example according to FIG. 1. As a result, the spacing of the planes from one another is significantly smaller, which results in a higher packing density of the arrester elements. This embodiment is therefore particularly suitable for installation in a gas with a high insulating capacity, for. B. the sulfur hexafluoride (SF ₆ ) used in pressurized gas-insulated, metal-enclosed switchgear assemblies _o For this purpose, a metal housing 28 is provided in the example according to FIG. 2, into which the voltage connection is introduced by means of a disk bushing 29.

In the surge arrester according to FIG. 2, a spark gap unit 30, which is encapsulated in an insulating housing 31, is used as a further arrester element in the second level from above in addition to the arrester elements 27 consisting of voltage-dependent resistors. As a result, a different gas than the insulating gas mentioned can be used in the region of the electrodes of the spark gap unit in order to achieve a desired response and extinguishing behavior of the spark gap. Nitrogen is particularly suitable for operating the spark gap. Due to its parallel connection to three of the arrester elements 27, the spark gap unit 30 short-circuits this part of the arrester during the response process.

In both examples described, four parallel _' columns are provided, which are in the corner points of a square stand. Of course, a smaller number, e.g. B. three, or a larger number of columns, e.g. B. six can be selected. In any case, the direct connection of the scaffold elements with the arrester elements and support bodies creates a mechanically extremely stable structure that does not require any further stiffening.

A scaffolding element is shown as an individual part in FIG. 3. The scaffold element 33 is designed as a cylindrical body and has an upper and a lower cover surface 34 or 35, each with a threaded opening 36 or 37, and on its circumference three threaded openings 40, 41 and 42 at an angle of 90 ° Arrangement of the threaded holes, the scaffold element 33 can be used at any point of the surge arrester shown in FIGS. 1 and 2. If the arrester elements as well as the insulating and conductive support bodies are provided with suitable threaded pins, the surge arresters described can be assembled in a modular manner. Instead of threaded holes, profile holes or simple through holes can also be provided if the scaffolding elements are designed as hollow bodies and the interior for attaching fastening elements, eg. B. pins, nuts or the like, is accessible. For this purpose, the scaffolding element can be formed in two parts by division along a line 43 shown in dashed lines in FIG. 3 in the manner of a pot and a lid.

In the examples according to FIGS. 1 and 2, arrester elements are respectively connected in series in the planes perpendicular to the longitudinal extension of the columns. However, arrester elements connected in parallel can also be provided, as is shown schematically in FIG. 4. The arrester elements 45 are ent here by dashes in the arrangement symbolizing speaking of the four-column structure. Two arrester elements are connected in parallel by conductive connections 46. Each level of the arrester therefore contains six instead of three arrester elements. If a further increase in the leakage current to be controlled or the energy to be absorbed is desired, more than two arrester elements can be connected in parallel for each level. The rest of the arrangement, in particular the arrangement of conductive and insulating support bodies between the levels, remains unchanged.

In Fig. 4 it is also shown that a control element 73, z. B. a linear or a non-linear resistor or a capacitor is connected, which, in conjunction with the same control elements 73 of the other levels, forms a chain of control elements connected in parallel with the arrester elements 45, which uniformize the voltage distribution. Just as two arrester elements 45 are connected in parallel on one side of the polygon arrangement, control elements can also be connected in parallel. However, it is also possible to use only one control element in each case and to provide this arrangement even when the levels are constructed in accordance with FIG. 2.

The described structure of surge arresters is not only suitable for arresters with a housing (2 in Fig. 1, 28 in Fig. 2). Rather, the active part itself can be set up as a surge arrester because the multi-column structure with the scaffolding elements can be carried out in a mechanically stable and stable manner. All that is required for outdoor installation is the weatherproof design of the components.

When encapsulating surge arresters with both an insulating housing and a metal housing, a device for pressure relief is generally required, which discharges the pressurized hot gases into the outside space when the arrester is overstressed. The described column structure of the new trap offers an advantageous option for incorporating a pressure relief system. For this purpose, the interior spaces of the scaffolding elements can be used as collecting spaces for the decomposition gases, as shown in FIGS. 5 and 6.

If the arresters are set up without a housing or encapsulation, there is also interest in an orderly discharge of the gases that occur in the event of overload. Therefore, the interior of the active part can also be used as collecting spaces in this embodiment, which can be provided at a desired location with an opening opening into the surroundings.

5 shows, as a section of an arrester according to FIGS. 1 or 2, an arrester element 45 with a framework element 46 and a subsequent support body 47. The arrester element 45 contains within an insulating housing 48 a resistance body 49 which is conductively connected to the scaffolding element 46 by means of a threaded connector 50. By screwing the threaded connector 50 into the scaffold element 46, in addition to the electrical and mechanically load-bearing connection, a seal from the environment is also created. The gases that occur when the resistance body 49 is overloaded therefore pass through a bore 51 of the threaded connector 50 into a cavity 52 of the scaffold element 46, from where they can spread through the subsequent tubular support body 47 to further scaffold elements. A gradual decrease in pressure occurs through a small opening 53 in the framework element 46 achieved. Correspondingly further openings can also be made in the other scaffolding elements, not shown. The overpressure only gradually takes up the environment and thus any existing housing. A crushing membrane can be arranged in a suitable location in the housing, through whose bursting the gases can escape to the outside.

In the example according to FIG. 6, which shows a further connection point within the column structure in a representation rotated by 90 ° in relation to FIG. 5, two arrester elements 54 are directly connected to a scaffold element 55 without a screw connection. For this purpose, cylindrical lugs 56 are formed on the scaffold element 55, which receive the ends of the arrester elements 54 like sleeves. The connection can e.g. B. by an external thread of the housing of the arrester elements and an internal thread of the lugs 56. In addition, putty or glue are also suitable for a permanent connection. In any case, a conductive transition between the arrester elements and the scaffolding elements must be ensured. Compared to the embodiment according to FIG. 5, larger cross sections for the passage of gases from the arrester elements into the scaffolding elements can be achieved according to FIG. 6.

While in the examples according to FIGS. 5 and 6 the cavities of the column structure serve as a collecting space for the decomposition gases, from which they gradually flow out through pressure equalization openings, FIG. 7 shows how the gases from an encapsulated arrester are of both insulating and metal encapsulated type can be derived without stressing the housing or the encapsulation in any way. For this purpose, the column structure, designated overall by 60, is designed to be closed with respect to the interior 61; H. there are no pressure equalization openings in the scaffolding elements.

The cavities of the support body of the column structure first open with the interposition of crushing membranes 67 in a buffer space 62 which is formed by a lower support plate 63 for the column structure 60 and the end fitting 64 of a housing 65. An opening 66 of the end fitting 64 is closed by a further breaking membrane 68. If, after the crushing membranes 67 have responded, gases enter the buffer space 62, the crushing membrane 68 bursts and the gases get directly into the environment without straining the housing 65. Therefore, the housing remains in a clean and reliable condition and can be used again after the defective active part 60 has been removed.

In Fig. 7 is also indicated by dashed lines that the gases can not only exit from the housing 65 in the axial direction according to the direction of arrow 70, but also with a correspondingly selected design of the end fitting 64 also perpendicular to the longitudinal axis of the housing 65 in the direction of Arrow 71 or by deflecting in the direction of arrow 72.

The surge arresters described can be constructed not only using the zinc oxide resistors mentioned above, which are characterized by a particularly pronounced, non-linear current-voltage characteristic, but also with other resistors suitable for surge arresters, alone or in conjunction with spark gaps connected in series or in parallel. Therefore z. B. Resistors based on silicon carbide can also be used, as well as combinations of different types of resistors or mixed bodies made of different resistance materials.

Otherwise, arrester elements can also be inserted into the columnar structure, which serve to control the voltage distribution, as is known by Resistors and / or capacitors can be achieved. For the same purpose, control rings can be used in addition or on their own, particularly in the case of the described arrester without a housing.

Claims (8)

1. Surge arrester with the following features: a) arrangement of arrester elements within the housing in planes perpendicular to the longitudinal extent of a scaffold consisting of several parallel columns; b) uniform dimensions of the arrester elements and of insulating support bodies and conductive scaffolding elements,
characterized in that c) each conductive scaffold element (16) has connection and connection means in the direction of the further columns (1 ₀ , 11, 12, 13) and d) with n scaffolding elements (16) at least (n-1) arrester elements (14) are present per level. (Fig.1) 2. Surge arrester according to claim 1, characterized in that a conductive support body (27) is inserted between the levels for connecting two scaffolding elements (24). (Fig. 2) 3. Surge arrester according to claim 1, characterized in that a diverter element (14) or a conductive support body (27) from level to level changing in another column (10, 11, 12, 13 or 20, 21, 22, 23) is arranged in such a way that a current flow direction changes from level to level. (Fig. 1 and Fig. 2) 4. Surge arrester according to claim 1, characterized in that in each level (n-1) arrester elements (45) and a control element (73) are arranged at ^g e, the control element (73) between the current supply and discharge each Level is switched. 5. Surge arrester according to claim 1, characterized in that the scaffolding elements (33) are designed as hollow bodies. (Fig. 3) 6. Surge arrester according to claim 5, characterized in that the interiors of the arrester elements (45) with the cavities (52) of the scaffold elements (46) and these are in communication with the surrounding atmosphere through a pressure compensation opening (53). (Fig. 5) 7. Surge arrester according to claim 6 with a housing, characterized in that the cavities of the active part (60) with the housing (65) surrounding atmosphere when an inadmissible overpressure can be connected by means of a crushing membrane (68). (Fig. 7) 8. Surge arrester according to claim 7, characterized in that the housing (65) has a buffer space (62) into which the cavities of the active part (60) open with the interposition of crushing membranes (67) and which in turn with the surrounding atmosphere by a further crushing membrane (68) can be connected.

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