|Title of Invention
ACTIVE PART FOR A SURGE ARRESTER
|Active part for a surge arrester The active part which i;3 provided for use in a surge arrester includes two connecting fittings (10, 20), which are arranged along an axis (7) at a distance from ore another, at least one cylindrical varistor column (30), which is provided between the tv;o connecting fittings (10, 20), and at least one dielectric loop (41,42). This loop (41, 42) is suppo:led on the two connecting fittings (10, 20) and thus holds the active part together thus forming a contact force. The active part is distinguished by a small physical height and little use of miiteriais. This is achieved in that at least one of \\"\e two connecting fittings (10, 20) has an electrode, which is arranged at right angles to the axis (z) and is in the fomn ol a plate (11, 12). as well as an electrical connection (12, 22), which is integrally fcimed on the plate (11, 12). Furthermore, supporting means which are in the form o1 shouders (13, i4, 23, 24) are provided for the dielectric loop (41, 42), and are formed in the plate (11, 21) and/or are integrally formed at the edge of the plate (11,21). (Figure 1)
DESCRIPTION Active part for a surge arrester
T-ie invention is based on an active part for a surge arrester as claimed in the prscharacterbihg clause of patent claim 1. The invention also relates to a surge arester which ncludes this active part.
The active pari: has two connecting fittings which are arranged along an axis at a distance from one another and to which a voltage in the voltage range above 1 kV can be applied. A varistor column, which is formed from a varistor element or from tvv: or more series-connected varistor elements, is located between the two connecting friings. The active part also has a dielectric loop or, possibly, two or more dielectric loops. This loop or the loops is or are supported on the two connecting fittings, thus holding the connecting fittings and the varistor column tojjether, thus forming a contact force. The loop or the loops may also be supported on ore of the two connecting fittings and on a connection piece, which is arranged between the two connecting fittings in the varistor column, and may hold together a s«=c:ion of the varistor column, which is bounded by the supporting GO meeting filing and the connection piece, thus forming a contact force.
A s;urge arrester is formed by protecting the active part against direct contact or dirt, fo- example by embedding it in a polymer or by installing it in a possibly 3£U5-insulatecl no using.
in 'he precharacterizing clause, the invention refers to a prior art of surge arresters .*$ is specified h E:P 614,198 B1 or in US 5'942'968. Surge arresters which are
described in these patent publications each include an active part, which is in the fc-.m of a column and is encapsulated by a polymer housing, with a varistor column which is; held between two connecting fittings. The holding force/but at the same time also the contact force in the active part, is applied by means of one or more pnsstres-sed dielectric loops which are supported on the two connecting fittings. The connecting fittings are each machined out of a metal cylinder and have slots and/or projections, each of which are used to hold one end of the dielectric loops. Furthermore, tha connecting fittings have holes in the column direction in order to accommodate electrical connections, possibly as well as a cavity, which likewise e>::ends in the column direction and is used to accommodate a section of the vaster column. The connecting fittings therefore extend over a comparatively long di-.tance- in the column direction, and thus increase the physical height of the active part, and hence: also of the surge arrester.
Furthernore. EP 1,066,640 B1 describes a surge arrestor having an active part wl'ich has a varistor column and in which a connection piece is arranged in the v£.;istor column, having bearing points on which prestressed dielectric loops are si. )portod which extend from an upper to a lower connecting fitting of the active pan:. These dielectric loops are also used to form a holding and contact force. The connection piece allows the active part to be dielectrically loaded to a greater 2>lont than in the prior art mentioned above, thus resulting in a surge arrestor for a richer voltage class.
DESCRIPTION OF THE INVENTION
Tha invention, a.3 it is defined in the patent claims, achieves the object of specifying ir; active part of the type mentioned initially, which is distinguished by a small physical height.
in i.he case of the active part according to the invention, at least one of the two ■xrmeethg firtiricjs has an electrode which is arranged at right angles to the axis .inci is in the form of a plate as well as an electrical connection which is integrally 'formed en the plate, and means for supporting one end of the dielectric loop, which means are formed in the plate and/or are integrally formed at the edge of the plate.
T >e physical height of the active part is thus on the one ha^d considerably reduced. On th3 other hand, the connecting fittings can now be manufactured using little m*.tt='ial; and with little effort, thus considerably reducing the production costs for the active part.
In order to save material, it is recommended that the electrical connection which is inl=jgraiiy for red on the pi'aie be flat. An electrical connection such as this may be connected to ths plate s.t any desired angle with respect to the plane of the plate, depending en the arrangement and configuration of the conductor that is to be connected to it. In order to allow the conductor to be connected easily, it is advantageous iter the electrical connection to be in the form of a perforated plate or a pug-in contact.
In one embodiment of the active part according to the invention, in which the contact force is achieved by means of at least one cup spring, this spring may be centered while? maintaining a predetermined physical height by means of an axially symmetrical centering tab which projects from a surface of the plate facing the va istcr coiurnns. This tab may be formed in the plate but may also be in the form of an insert part and may be fixed in a recess in the plate. The tab is passed through the hols in the cup spring, which is generally in the form of a conical ar lular disk. In order to prevent overextension of the cup spring during installation it during operation of the active part, the diameter of the centering tab and the nlornaf diameter of the annular disk should be matched to one another so as to invent "he cup .spring from being pressed flat.
n the case of ihe active part according to the invention, the supporting means ■acvantageou&iy have at least one shoulder which is integrally formed at the edge of !hi; plaro and is narrower than the diameter of the varistor column. A narrow shoulder such us this is particularly suitable for manufacturing active parts with iarjja diameters. Two or more such narrow shoulders and a corresponding number of dielectric loops make It possible to produce a mechanically robust active part wh'Ie maintaining a small physical height, which is also governed by the thickness of the p'ate.
If the supporting means have a shcuider which is formed in the piate and passes through the axis of the varistor column, then the mechanical strength and the desired contact force of the active part can be achieved while maintaining the small physical heoht and with a single dielectric loop, The mechanical strength is ir oreas«3d further by supporting means which have two shouiders, each of which is formec in one of two sections of the plate edge which run in a straight line. Irrespective of whether only one, two or possibly even more shoulders is or are provided in the plate, it is advantageous, in order to ensure good mechanical slrength and a uniform contact pressure while maintaining the small physical h-:-right, for each shoulder to have a surface which is largely parallel to the plate surface over ttv-j majority of the plate extent, and for the associated loop to be in th.5 form of a rectangle and to be supported on the inside by means of one of the r«i»otangjlar laces on the surface.
BRIEF DESCRIPTION OF THE DRAWINGS
T-•:& invention vWII be explained in the following texf with reference to exemplary embodiments. In the figures:
Figure 1 shows an exploded illustration of a first embodiment of the active part according to the invention,
F gure 2 shows a front view of the first embodiment of the active pan,
F gure 3 shows a side view of the first embodiment of the active part,
Figure Figure 5 chows an embodiment of a surge arrester which is intended for outdoor applications and includes the active part as shown in Figures "! to 3,
Figure & shows a viaw of a second embodiment of the active part according to fhE? invention, which is intended for a high dielectric load,
Figure 7 shows a view of a third embodiment of the active part according tc the invention, which is designed such that it can be plugged in.
Fijj-jre S &hows a view of a fcurth embodiment of the active part according to the invention, and
Ficjure 3 shows a view of a fifth embodiment of the active part according to the invention,
APPROACHES TO IMPLEMENTATION OF THE INVENTION
Th.=i same reference symbols in ail of the figures denote parts which also have the same effect. The active part which is illustrated in Figures 1 to 3 has two xnnec:ing fittings 10, 20 which are composed of electrically conductive material, such as aluminum, and are separated from one another along an axis z (Figure 1). £a:h of the tv/o connecting fittings 10 and 20 has an electrode which is arranged at ic;ht angles 1c the axis and is in the form of a plate 11 or 21, respectively, as well .is a respective electrical connection 12 or 22, which is integrally formed on the respective plate 11 or 21. Shoulders 13, 14 and 23, 24 are formed in sections of l:h The respective tab 15 or 25, the respective cup spring 16 or 26 and a cylindrical vuistor column 30 composed of non-linear resistance material, for example based on metal oxicla, such as ZnO in particular, are arranged coaxiahy between the connecting fittings 10, 20. As can be seen, the varistor column 30 is formed from a Kindle varistor aliment, but may also include two or more elements stacked one on lop of the other. The upper or the lower end face of the varistor column 30,
respectively, mixes contact with a current contact element 17 or 27, respectively. An electrically conductive pressure absorbing plate 18 or 28, respectively, is provided between the respective cup spring 16 or 26 and the current contact aliment 17cr27.
A« can oe se Ac can be seen from Figure 3, the shoulders 13, 23 have a surface which is largely .oa.'allel to trie plate surface over the majority of the plate extent, and the -ectangular dielectric loop 41 is supported on the inside by two mutually opposite rectangular faces on these surfaces. This configuration of the shoulders and of the dielectric loop allow the dimensions of the connecting fittings 10, 20 to be kept small and to be reduced to the thicknesses of the plates 11 or 21. In addition to a
small physic.;!.] height of the active part, this also at the same time ensures its nncdchar.ical strength and its current-carrying capacity.
Ir order to reduce the use of m&tarials and the manufacturing costs, the electrical connections 12, 22 are flat, In practice, they may be integrally formed at any desired angto on the plates 11, 22. If they are aligned in the direction of the axis z, ar-a integrally formed centrally on the plates and are in the form of a perforated plate, as is illustrated in the exemplary embodiment shown in Figures 1 to 3, then even a heavy :;able conductor lo which a high voltage can be applied can be screwed to r.e connection 12, and a corresponding grounding conductor can be so revved to ine connection 22 in a space-saving manner. Alternatively, as is illustrated in Figure 7, the connections 12, 22 may oe routed in the direction of the plates 11,2: and, for example, may be in the form of plug-in connections.
A: can be se*n from Figures 4 and 5, the varistor column, the plates of the connecting filings and the dielectric loops may be surrounded by insulating materia-, fc example a polymer, for example based on silicone or epoxy. Copending on the design of the surrounding dieiectric compound, this results in a surge arrester which is suitable for indoor applications (Figure 4) or for outdoor applications (Fiuure 5} and has electrical connections 12, 22 which are passed out of a dielectric hcusing 50.
TVie dielectric loops need not necessarily be supported on both connecting fittings. A': can be s^en from the* exemplary embodiment in.Figure 6, a metallic connection pioce 31 may be arranged in the varistor column in an active part which can be leaded at high voltages- The dielectric loops 41, 42 are then supported on the u\:per plate 11 of the connecting fitting 10 and on the connection piece 31: and produce the hdding and contact force in an upper section of the active part. A diolectric loop 43 and a further dielectric loop, which cannot be seen, are supported or the connection piece 31 and on the plate 21 of the lower connecting fitting 20, ard produce tha holding and contact force in a lower section of the active part.
ir, the embodiment of the active part as shown in Figure 9, only two shoulders 200 ar.d 201 are provided as the supporting means, and these are formed in the plates 1 I, 21 and passed through the axis z of the varistor column. This ensures that a
dielectric loop. 40, which is likewise in the form of a rectangle, is held centrally in the a-ea of the axis z, and ensures a uniform holding and contact force in the active p.=Lrt, This ensures a uniform current density for a dissipation current which is carried In the active part when an overvoltage occurs.
A;-; is illustrated in Figure 8, shoulders 131, 132, 231, 232 may be formed at the e<:ges of the plates as supporting means and these shoulders are narrower than thtt dianeler varistor column. without having to sacrifice advantage o a small physical height saving in materiafs holding contact force ir part can be achieved by comparatively large number narrow dielectric loops>
LIST OF REFERENCE SYMBOLS
10 20 Connecting fittings
11 21 Plates
1£' 22 Electrical connections
13 14.ii3.24, 131, 132,
15 25 Centering tabs
10 26 Cup springs
17, 27 Current contact elements
12, 28 Pressure absorbing plates
30 Varistor column
31 Connection piece
40, 41, 42, 43, 4" 1,412 Dielectric loops
■30 Dielectric housing
12. An active part for a surge arrester substantially as herein described with reference to the accompanying drawings.
|Indian Patent Application Number
|PG Journal Number
|Date of Filing
|Name of Patentee
|ABB TECHNOLOGY AG
|AFFOLTERNSTRASSE 44, CH-8050 ZURICH
|PCT International Classification Number
|PCT International Application Number
|PCT International Filing date