EP1603141B1 - Surge arrester with insulation by gas - Google Patents

Description

TECHNICAL AREA

The invention is based on a gas-insulated surge arrester according to the preamble of patent claim 1.

Such a surge arrester contains an insulating gas-filled encapsulation of electrically conductive material. Inserted into the encapsulation and aligned along the encapsulation axis is an active part, which has varistors as well as a high-voltage lead and an earth-leadable electrode. The active part further comprises means for clamping a stack of varistors arranged between the high-voltage and ground electrodes to form a mechanically stable varistor column. In order to keep the dimensions of the enclosure low and at the same time to electrically load the individual varistors, an element connected to the high voltage electrode can be arranged between the active part and the enclosure, with which the electric field, which acts in the interior of the enclosure during operation of the arrester, is controlled becomes.

The encapsulation is designed to be safe from contact and generally consists of metal, such as aluminum, an aluminum alloy or steel, of conductive plastic or of insulating material, which is coated with an electrically conductive layer. The encapsulation is filled with an insulating gas, such as sulfur hexafluoride and / or nitrogen, of up to a few bar pressure and is formed predominantly axially symmetric. By "predominantly axisymmetric" are meant deviations from the axial symmetry, which do not significantly affect the formation of an axisymmetric electric field in the interior of the enclosure. Such deviations are generally applied to a jacket tube flange approaches with closable openings which record example, a burst protection or a measuring device or serve as a mounting access.

Depending on the voltage and current load, the active part can contain only one varistor column or else two or more varistor runs, which can be electrically connected in series and / or electrically in parallel. Each varistor column generally contains a plurality of stacked cylindrical varistors based on doped zinc oxide. At least between two of the varistors can also be arranged a heat absorption or an extension of the column serving metal body Are two or more varistor provided, so in the columns between two of the varistors or between an electrode and one of the varistors and insulator can be provided. Sections of the columns bounded by the insulating pieces can then be electrically connected in series to form a series connection of the varistor columns.

STATE OF THE ART

Gas-insulated surge arrester of the type mentioned are in the patent documents EP-B-0 050 723 ( EP-A-0 050 723 ) US-A-4,814,936 and EP-A-0 036 046 Each of these surge arresters contains a metal encapsulation filled with insulating gas, such as SF ₆ or N ₂ , in which an active part is arranged which, depending on the magnitude of the voltage to be limited, has a varistor column (EP-A, EP-A). B-0 050 723 . EP-A-0 036 046 ) or a plurality of varistor columns ( US-A-4,814,936 In the prior art according to EP-A, B-0 050 723 The varistor column contains stacked partial varistor columns which are each formed by a varistor stack, two terminal electrodes and a porcelain cylinder. By contrast, in the prior art after US-A-4,814,936 Insulating rods provided, which mechanically stabilize the varistor columns also show in the prior art US-A-4,814,936 and after US-A-4,504,089 the side-by-side varistor columns each have mutually electrically insulated column sections. By electrically connecting the individual sections in a spiral shape, a series connection of the individual column sections and thus a high withstand voltage can be achieved while at the same time having a low overall height of the active part.

In order to keep the dimensions of the metal enclosures small, each of these surge arresters between Varistor column resp Varistorsäulen and Kapselungswand a pillar resp. The field control element homogenizes the electric field acting inside the housing during operation of the arrester, so that the varistors arranged in the varistor column or in the varistor columns are loaded more or less uniformly.

EP-A-0 875 087 describes field-controlling material based on a microvaristor-filled polymer for electrical equipment such as high voltage power cables.

At one off EP-A-1 083 579 Prior art encapsulated surge arrester with a varistor column embedded in an elastomeric insulating sheath, the varistor column is stabilized with at least one insulating loop, the ends of which rest on two electrodes. Between the two electrodes a varistor stack acted upon by the loop with biasing force is arranged. By suitable design of the encapsulation, an equalization of the electric field is achieved in the section of the varistor column which is at high voltage potential.

Out US-A-5 912 611 . US-A-5 517 382 . EP-A-0 810 613 . EP-B-1 066 640 and the corresponding patent document US-A-5,936,826 It is also known that in overvoltage arresters for outdoor applications in which the varistor columns are embedded in an elastomeric polymer, one or more of the aforementioned Isolierstoffschlaufen be used for the mechanical stabilization of the Varistorsäulen field control elements are not provided in these arresters.

PRESENTATION OF THE INVENTION

The invention, as indicated in the claims, the object of the invention is to reduce the dimensions and the manufacturing costs of a gas-insulated surge arrester of the type mentioned

In the case of the surge arrester according to the invention, the tensioning means comprise at least one loop made of a material resistant to fission products of the insulating gas, which loop is supported on two electrodes of the varistor column, which are either the high voltage electrode or the ground electrode and an intermediate electrode or two intermediate electrodes, is the high voltage electrode having a contact element electrically conductively connected to the high-voltage potential sliding contact arrangement, a fixed mating contact of the sliding contact arrangement is held on a sealing gas-tight completion of the bushing insulator and connectable with an outside of the encapsulation end with the high voltage potential and the field control is flush with a lateral surface of the mating contact

Since electrodes are anyway present in the varistor column, the tensioning means formed by the loop and possibly provided further loops can be installed without additional parts, such as insulating tubes or insulating rods, and without much space to form a mechanically stable varistor column in the active part. The active part therefore has small dimensions transversely to the column axis. Therefore, the field control element in manufacturing technology favorable manner can be flush mounted on the lateral surface of the fixed mating contact of Gleitkontaktanordnung and this can also be significantly reduced in this case the diameter of the enclosure Since already prefabricated bearings for the loops are formed in the electrodes, the active part and thus the Surge arrester can be made in a simple manner, namely by applying the loops on the bearings and tightening the loops, such as with a pressure screw acting on a pressure plate or by heating the heat-shrinkable fibers containing loops. When operating the arrester due to heating occurring expansion of the varistor column in the direction of the column axis is also compensated by the sliding contact arrangement in an advantageous manner.

If the loops are arranged in a gas atmosphere which, during operation of the surge arrester, produces aggressive cleavage products due to moisture and partial discharges which can react with certain fiber materials, such as quartz, and thereby possibly impair the strength of the loops and thus the reliability of the arrester, then it is recommended itself to provide as a material for the loops a composite based on a fiber-reinforced polymer and to coat this composite with a cleavage product-resistant protective varnish and / or to use slit-product-resistant fibers.

A large height of the active part with good mechanical stability is achieved when the varistor column has at least two partial columns, of which the first contains the high voltage electrode, a first stack of varistors, a first intermediate electrode and a first loop and optionally further first loops and the second Partial column the earth electrode, a second stack of varistors, a second intermediate electrode and a second loop and possibly further second loops, Such a surge arrester can be operated with high nominal voltages, although it has only one or only a small number of series-connected varistor columns.

Characterized in that the varistor arranged between the first and the second part of the column column at least a third column having a third intermediate electrodes held on the third intermediate electrode, a third stack of varistors, a held on the first intermediate electrode or a fourth column fourth intermediate electrode and a third Loop and possibly other third loops, can still be achieved with good mechanical stability of the varistor column even greater height.

For a favorable production of advantage, it is when two in the Varistorsäule adjacent arranged partial columns formed as independent assembly units and releasably connected to each other. These partial columns can be prefabricated inexpensively From the prefabricated partial columns can subsequently in a few simple steps arresters, possibly with different nominal voltages determined by the height, are produced.

A particularly high stability of the varistor column and thus a particularly high reliability of the arrester according to the invention is achieved when two partial columns arranged adjacent in the varistor column have a common intermediate electrode.

If the arrester according to the invention is intended for large, high voltage levels, at least two varistor columns arranged side by side should be provided, which each have at least two insulators, of which a first one separates the potentials of two varistors adjacent in the varistor column to form two mutually electrically insulated column sections serves and the second of the separation of the potential of a varistor from the potential of an electrode of this varistor column. In addition, at least two current connectors are then provided, of which a first provided in a first varistor column first column portion with the provided in the second varistor column first column section and the second power connector, the first column section of the second varistor column with the second column section of the first or a third varistor column connects that the varistor columns are connected in series by electrically interconnecting the column sections.

It has proved to be advantageous to design the insulators in each case in tubular form and to align the tube axes in the direction of the encapsulation axis. The two annular ends of the insulators each provide a tipping support for a varistor or an electrode of the varistor column and thus contribute in addition to the loops essential to a mechanically stable active part.

In order to simplify the manufacture of an arrester with an active part containing several varistor columns, at least one of the current connectors should contain a detachable connection, in particular a plug connection. At least part of the varistor columns can then be manufactured very easily by mechanically connecting the assembly units, independently of the current connectors necessary for the formation of the series connection. By closing the detachable connection, the desired circuit can then be realized after completion of the varistor columns.

Since the insulators provided in the multi-column active part are exposed to large electrical loads during operation of the arrester according to the invention, it is advisable to arrange a field control electrode on at least one of the two pipe ends of the insulators. On the one hand, the electrical field acting in the isolator is thereby made uniform, and on the other hand, this electrode also serves to center the varistor adjacent to the varistor column. Advantageously, the field control electrode has a ring-shaped bead. This bead serves to receive the pipe end and the centering of the insulator. In order to save additional parts, one of the current connectors can be molded onto the field control electrode. If at least one vent opening is formed in the pipe wall of the insulator, the insulating gas quickly penetrates into the interior of the insulator during assembly and during operation of the arrester and thus always ensures the operational safety of the arrester according to the invention.

The gas-insulated arrester according to the invention is characterized by a particularly compact design, when the field control element contains a composite formed by a polymeric matrix and a filler embedded in the matrix, which when loaded with an alternating electric field of up to 100Hz, a dielectric constant between 5 and 45 and / or has a non-linear current-voltage characteristic. This composite acts macroscopically like an insulator. Therefore, the field control element close to the Varistorsäule resp. the Introduced Varistorsäulen or even on the Varistorsäule resp. the varistor columns are arranged. The dimensions of the gas-filled enclosure can then transverse to the column axis, respectively. the column axes are kept very small. Advantageously, a filler is used which contains a material of high dielectric constant, in particular conductivity black or a titanate, such as barium tanate, and / or microvaristors, which are formed at least partially from doped and sintered zinc oxide.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.1

eine Ansicht einer Ausführungsform des gasisolierten Überspannungsableiters nach der Erfindung mit einer axialsymmetrischen Kapselung und einem in der Kapselung angeordneten Aktivteil mit einer aus zwei Teilsäulen aufgebauten Varistorsäule, bei der die Kapselung, ein Feldsteuerelement und ein Kontaktelement längs der Achse der Kapselung geschnitten dargestellt sind,

Fig.2

eine Ansicht eines Teils des Aktivteils einer abgewandelten Ausführungsform des gasisolierten Überspannungsableiters gemäss Fig.1,

Fig.3

eine Ansicht des Aktivteils einer weiteren Ausführungsform des gasisolierten Überspannungsableiters nach der Erfindung, bei der das Aktivteil drei Varistorsäulen aufweist, welche neben Varistoren auch Isolatoren enthalten, und

Fig.4

eine Ansicht eines der Isolatoren des Aktivteils gemäss Fig.3.

With reference to drawings, embodiments of the invention will be explained in more detail. Hereby shows:

Fig.1

a view of an embodiment of the gas-insulated surge arrester according to the invention with an axially symmetric encapsulation and an active part arranged in the enclosure with a constructed of two partial columns varistor column, wherein the encapsulation, a field control element and a contact element along the axis of the encapsulation are shown in section,

Fig.2

a view of a portion of the active part of a modified embodiment of the gas-insulated surge arrester according to Fig.1 .

Figure 3

a view of the active part of another embodiment of the gas-insulated surge arrester according to the invention, in which the active part has three varistor columns, which in addition to varistors also contain insulators, and

Figure 4

a view of one of the insulators of the active part according to Figure 3 ,

WAYS FOR CARRYING OUT THE INVENTION

In all figures, like reference numerals refer to like acting parts. The in Fig.1 shown surge arrester has an executed as a pot axially symmetrical metal enclosure 1, in which an aligned along the encapsulation axis active part 2 is arranged. The active part contains a varistor column 3, an electrode 4 which can be led to high voltage, an electrode 5 which can be led to ground potential and an element 6 arranged between the varistor column 3 and the encapsulation 1 and electrically connected to the high voltage electrode 4 for controlling an internal operation of the arrester the encapsulation 1 acting electric field.

The varistor column 3 is composed of two stacked sub-columns 7 and 7 ', each containing a plurality of stacked fully cylindrical varistor elements 8 of non-linear resistance material, such as based on metal oxide, in particular of suitably doped ZnO. The partial columns 7, 7 'are in each case mechanically stabilized by loops 9 which are designed to be electrically insulating and which are supported on two electrodes to form a stable assembly unit with prestressing.

The two electrodes are in the sub-column 7, the groundable electrode 5 and an intermediate electrode 10, in which the sub-column 7 'held on the intermediate electrode 10 in an electrically conductive intermediate electrode 11 and the high-voltage electrode 4. In embodiments in which the varistor column 3 no resp , contains at least three partial columns, only the two electrodes 4 and 5 are provided, resp. For example, a middle partial column arranged between the two partial columns 7 and 7 'has two intermediate electrodes which are mechanically and electrically connected to the two intermediate electrodes 10 and 11.

Each of the aforementioned electrodes contains two holders 12 (indicated only for the electrode 5), on each of which one end of two loops 9 is supported. Depending on the size of the Varistorsäule resp. It is also sufficient for the partial columns if only one loop or evenly distributed in the circumferential direction of the column three and more loops are used.

The loops 9 are made of a material resistant to fission products of the insulating gas. Depending on which composition has the insulating gas, different requirements are placed on the material, which are significantly lower in the case of an insulating gas based on nitrogen than in the case of an insulating material based on sulfur hexafluoride. Such material is advantageously a composite based on fiber-reinforced polymers. The fiber reinforcement is generally formed by wound glass or polymer based filaments, such as polyester, polyamide or polyimide, but may also otherwise incorporate structures incorporated into the polymer of the composite such as fabrics, tapes or mats. To protect the fiber reinforcement, the composite is coated with a cleavage product resistant protective varnish. Alternatively or additionally, the fibers and optionally also the polymer embedding the fibers can be formed from a product which is resistant to cracking. The cross-sectional profile of the loops can have virtually all between round and triangular lying forms. For manufacturing reasons, however, rectangular profile is preferable.

If the varistor column constructed of partial columns, so instead of the two intermediate electrodes 10 and 11 one Fig.2 apparent single intermediate electrode 13 are used. In this intermediate electrode 13 then the holders 12 of the electrodes 10 and 11 are formed. In order to keep the design of this intermediate electrode in the direction of the column axis low, the brackets 12 for the two sub-columns 7 and 7 'associated loops 9 are arranged offset in the circumferential direction of the electrode 13 against each other.

The varistor column 3 has, depending on the voltage levels in which the arrester according to the invention is used, lengths that are in the meter range. When operating the arrester, the varistor column heats up and expands in the direction of the column axis. Therefore, the high voltage electrode 4 is electrically connected to a contact element 14 of a sliding contact 15, respectively. This contact element 14 may be molded into the high voltage electrode 4. In an operational change in length of the varistor column 3, the contact element 14 slides in the direction of the column axis in an axially aligned bore 151 of a fixed counter-contact 16 of the sliding contact arrangement and thus compensates for this change in length. The current transition from the mating contact 16 to the contact element 14 is characterized by an annular ensured. The fixed mating contact 16 is held on a sealing gas-tight closing the terminal enclosure 17 and is connected with its located outside of the enclosure 1 end with a monitored by the arrester high voltage line. Since the loops 9 can be fixed to brackets 12, which are formed in the lateral surface or formed on the lateral surface, the contact element 14 and the high voltage electrode 4 can be made of one part.

The loops 9 are predominantly held in the electrodes 4, 5, 10, 11, 13 and take up little space in the radial direction. The field control element 6 can therefore be attached flush to the lateral surface of the gas-tight guided by the enclosure, fixed counter-contact 16. The diameter of the encapsulation 1 can therefore be considerably reduced.

How out Figure 3 can be seen, the active part instead of only one varistor column, two and more side by side arranged varistor columns 3, 3 '3 "have .. These columns can be electrically connected in parallel for a higher current carrying capacity, but are generally - as well as in Figure 3 is shown - electrically connected in series. This series connection is realized with the aid of insulators 18, 18 ', which enable sections of electrical interconnection of the columns arranged side by side. The design of the arrester can be significantly shortened, which has a particularly advantageous effect when used in high voltage levels. The insulators 18 each serve to separate the potentials of two in the varistor column 3, 3 'or 3 "adjacent varistors 8 to form two mutually electrically insulated column sections 19 and 20, whereas the insulators 18' of the separation of the potential of a varistor 8 of the varistor column from the potential In addition, current connectors 21, 21 'are provided which connect the column sections of the various varistor columns 3, 3', 3 "to one another. The power connectors 21 connect the column sections 19 or 20 and the power connectors 21 the column sections 19 and 20. Thus, the power connector 21 connects the column section 19 provided in the varistor column 3 'with the column section 19 provided in the varistor column 3 "and the power connector 21' connects the column section 19 of the varistor column 3 "with the column section 20 of the varistor column 3rd

How out Fig. 4 can be removed, the insulators 18 and, accordingly, the insulators 18 'are each tubular. The tube axes are respectively in the direction of the axes of the varistor columns. the axis of the encapsulation 1 aligned. The two annular ends of the insulators 18 each provide a kippfeste support for one of the varistors 8, one of the electrodes, for. B. 10, or optionally provided column-extending metal discs. The partial columns 7, 7 'resp. The varistor columns 3, 3 ', 3 "are characterized by high mechanical stability after clamping with the loops 9. At each of the two tube ends of the insulator 18, one of two field control electrodes 22 is mounted, which homogenize the electric field during operation of the arrester loads the insulator 18. Each of the two field control electrodes 22 has an annular bead 23 for receiving the pipe end and for centering the insulator 18. The insulator 18 'can be omitted from the electrode lying on the electrode, for example 11, end of the pipe because the electrode 11 then acts field-controlling itself.

To the field control electrode 22 of the current connector 21 is formed. As a result, the assembly of the varistor column is facilitated and not only the individual components of the sub-column contacted with each other during the clamping of the sub-columns 7, 7 'with the loops 9, but at the same time also made contact with the power connector 21, 21'. In this power connector, a plug contact 24 is formed. When mounting the arrester, this plug contact 24 after the completion of the varistor columns 3, 3 ', 3 "with a mating plug contact of another of the current connector 21, 21' are electrically connected to form the desired series connection of the varistors.

In order to ensure a rapid penetration of the insulating gas into the tube interior when filling the enclosure 1 with the insulating gas, 18 vents 25 are formed in the tube wall of the insulator.

The mehrsäulig running active part 2 can be clamped between two holding plates, not shown, with the help of other loops. Operational changes in length of the varistor columns 3, 3 ', 3 "can then be compensated by elastically deformable force transducers 26, which are arranged in recesses of the electrodes 4, 5, 10, 11 and 13. One such - for example, current-conducting disc springs exhibiting - is in Fig.2 schematically shown. The power connections to this multi-column active part are ensured by current connectors 27 and 28, which are each performed electrically isolated from the enclosure. This in Figure 3 but active part can also be only part of an active part, the other part of the Varistorsäulen 3, 3 ', 3 "down added and electrically connected to the illustrated part via the power connector 27.

LIST OF REFERENCE NUMBERS

1

encapsulation

2

active part

3, 3 ', 3 "

Varistorsäulen

4

High-voltage electrode

5

groundable electrode

6

Field control

7, 7 '

part pillars

8th

varistors

9

clamping loops

10, 11

between electrodes

12

brackets

13

intermediate electrode

14

contact element

15

sliding contact

151

drilling

152

Spring contact element

16

countercontact

17, 18, 18 '

insulators

19, 20

column sections

21

power connectors

22

Field control electrode

23

beading

24

plug contact

25

openings

26

Load cell

27, 28

power connectors

Claims (13)

1. Gas-insulated surge arrester comprising an insulating gas-filled encapsulation (1) which is of predominantly axially symmetrical design and is composed of electrically conductive material, and comprising an active part (2) which is arranged in the encapsulation (1) and is oriented along the encapsulation axis and has varistors (8), an electrode (4) which can be connected to high-voltage potential, an electrode (5) which can be connected to earth potential, at least one intermediate electrode (10, 11, 13), tensioning means and an element (6), which is arranged between the active part (2) and the encapsulation (1) and can be connected to the high-voltage potential, for controlling an electrical field which acts in the interior of the encapsulation (1) during operation of the arrester,
   wherein the active part has at least one mechanically stable varistor column (3, 3', 3") which is formed by clamping at least one stack of the varistors (9) which is arranged between two of the electrodes (4, 5, 10, 11, 13), characterized in that the tensioning means contain at least one loop (9) which is composed of a material which is resistant to cleavage products of the insulating gas, which loop is mounted on two electrodes (4, 5, 10, 11, 13) of the varistor column (3, 3', 3") which are either the high-voltage electrode (4) or the electrode (5) which can be connected to earth and an intermediate electrode (10, 11, 13) or two intermediate electrodes, in that the high-voltage electrode (4) is electrically conductively connected to a contact element (14) of a sliding contact arrangement (15) which can be connected to high-voltage potential, in that a stationary mating contact (16) of the sliding contact arrangement (15) is held on a bushing insulator (17), which closes off the encapsulation (1) in a gas-tight manner, and can be connected to the high-voltage potential by way of an end which is located outside the encapsulation (1), and in that the control element (6) is mounted flush on a casing surface of the mating contact (16).
2. Arrester according to Claim 1, characterized in that the varistor column (3) contains at least two column elements (7, 7'), of which the first column element (7) contains the high-voltage electrode (4), a first stack of varistors (8), a first intermediate electrode (11) and also the first loop (9) and possibly further first loops (9), and the second column element (7') contains the electrode (5) which can be connected to earth, a second stack of varistors (8), a second intermediate electrode (10) and also a second loop (9) and possibly further second loops (9).
3. Arrester according to Claim 2, characterized in that the varistor column (3) contains at least one third column element which is arranged between the first column element (7) and the second column element (7') and has a third intermediate electrode which is held on the second intermediate electrode (10), a third stack of varistors, a fourth intermediate electrode which is held on the first intermediate electrode (11) or a fourth column element, and also has a third loop and possibly further third loops.
4. Arrester according to either of Claims 2 and 3, characterized in that two column elements (7, 7') which are arranged adjacent to one another in the varistor column (3) each form an assembly unit and are connected to one another in a releasable manner.
5. Arrester according to one of Claims 2 to 4, characterized in that two column elements (7, 7') which are arranged adjacent to one another in the varistor column (3) have a common intermediate electrode (13).
6. Arrester according to Claim 5, characterized in that the field control element contains a composite material which is formed by a polymer matrix and also a filler which is embedded in the matrix, the said composite material having a dielectric constant of between 5 and 45 and/or a non-linear current/voltage characteristic curve when loaded with an electrical AC field of up to 100 Hz.
7. Arrester according to Claim 1, characterized in that at least two varistor columns (3, 3', 3") which are arranged next to one another are provided, the said varistor columns each having at least two insulators (18, 18'), of which a first insulator (18) serves to disconnect the potentials of two varistors (8), which are adjacent to one another in the varistor column (3), so as to form two column sections (19, 20) which are electrically insulated from one another, and the second insulator (18') serves to disconnect the potential of a varistor (8) from the potential of an electrode (10) of this varistor column, and in that at least two current connectors (21, 21') are provided, of which a first current connector (21) connects the first column section (19, 20), which is provided in a first varistor column (3'), to the first column section (19), which is provided in the second varistor column (3"), and the second current connector (21') connects the first column section (19) of the second varistor column (3") to the second column section (20) of the first or a third varistor column (3) in such a way that the varistor columns (3, 3', 3") are connected in series by electrically interconnecting the column sections (19, 20).
8. Arrester according to Claim 7, characterized in that the insulators (18, 18') are each of tubular design and have a tube axis which is oriented in the direction of the encapsulation axis.
9. Arrester according to either of Claims 7 and 8, characterized in that at least one of the current connectors (21, 21') contains a releasable connection, in particular a plug connection (24).
10. Arrester according to either of Claims 8 and 9, characterized in that in each case one field control electrode (22) is arranged on at least one of the two tube ends of the insulators (18, 18').
11. Arrester according to Claim 10, characterized in that the field control electrode (22) has a bead (23) of annular design for receiving the pipe and for centring the insulator (18, 18').
12. Arrester according to either of Claims 10 and 11, characterized in that one of the current connectors (21) is integrally formed on the field control electrode (22).
13. Arrester according to one of Claims 8 to 12, characterized in that at least one ventilation opening (25) is made in the tube wall of the insulator (18).

Images