EP0810613B1 - Surge arrester - Google Patents

Description

TECHNICAL AREA

The invention is based on an active part for a surge arrester according to the preamble of claim 1.

STATE OF THE ART

The invention refers to a prior art, as it results from EP 0614 198 A2. One in this state of the Technology described surge arrester contains several cylindrical resistance elements with varistor behavior, which column-shaped stacked between two power connection fittings are arranged. One the varistors and the two connection fittings to form an axially acting Contact force cohesive clamping part has at least two with their ends resting on the connection fittings Loops up. A cast housing made of a weatherproof Plastic surrounds the varistors, the loops and the most of the connection fittings.

The production of such a surge arrester is relatively expensive, because two or even more loops for fixing the varistors and the connection fittings containing columnar Ableiteraktivteils and the Generation of contact force are needed.

BRIEF SUMMARY OF THE INVENTION

The invention as defined in claim 1, the task is based, an active part of to create the aforementioned type, which despite simple construction due to good mechanical and electrical Characteristics distinguishes and which at the same time in particularly inexpensive manner can be produced.

The active part according to the invention faces the prior art the Advantage on that there is only a single loop for Fixing and clamping two connection fittings and at least one held between the valves varistor needed. Therefore, it can be special in particular be made economically. To his assembly becomes just a pre-made and temporarily a axial guide ensuring template needed in the Connection fittings and the at least one varistor first stacked in the form of a column and then by attaching the Loop to form a bias to mechanical stable active part of the surge arrester connected become. Since in this case the axis of the column-shaped Active part, the loop ends substantially symmetrical penetrates, the loop creates a in the entire active part uniform contact force. When an overvoltage occurs is thus a uniform current density of one in the active part ensured discharge current and is therefore a Inadmissibly high local heating of contact transitions of the Active part avoided with great certainty.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.1

eine Seitenansicht einer Ausführungsform des Aktivteils nach der Erfindung, welches unter Bildung eines Überspannungsableiters in ein gestrichelt angedeutetes transparent dargestelltes Gussgehäuse eingebaut ist,

Fig.2

eine Aufsicht auf einen längs II-II geführten Schnitt durch das nun perspektivisch dargestellte Aktivteil gemäss Fig.1, und

Fig.3

eine Explosionsdarstellung des Aktivteils gemäss Fig.1.

A preferred embodiment of the invention and the advantages that can be achieved thereby are explained in more detail below with reference to drawings. Hereby shows:

Fig.1

a side view of an embodiment of the active part according to the invention, which is incorporated to form a surge arrester in a dashed line indicated transparent cast housing,

Fig.2

a plan view of a longitudinal II-II guided section through the now shown in perspective active part according to Fig.1, and

Figure 3

an exploded view of the active part according to Fig.1.

WAYS FOR CARRYING OUT THE INVENTION

In all figures, the same reference numerals designate the same effect Parts. The active part shown in Figures 1 to 3 has two preferably made of aluminum existing and spaced apart along an axis z Connection fittings 1, 2 on. The connection fitting 1 is with a trained as a screw hole 11 fastening device for a not shown on high voltage potential provided with an executable electrical conductor. The connection fitting 2 is with a fastening screw 12 formed as a fastening device feasible at earth potential. She has one axially aligned threaded hole 3, in which a pressure screw 4 is guided displaceably in the axial direction. The Numeral 5 denotes a loop of a wound, glass fiber reinforced and in a plastic matrix embedded band. The loop 5 is with both ends in slit-shaped sections of material recesses 6, 7 out, which in the connection fittings 1, 2 are formed.

Between the connection fittings 1, 2 is to form a columnar Ableiteraktivteils a cylindrical varistor element 8 of non-linear resistance material, about the base of metal oxide, such as in particular ZnO arranged. Alternatively, instead of an element 8 and two or more columnar stacked varistor elements be provided.

In a molded into the connection fitting 1 disc-shaped Recess are electrically conductive parts, namely two contact pressure generating and each as a plate spring trained spring elements 9 and one preferably made Aluminum or copper or an aluminum or copper alloy existing thrust washer 10, in the axial direction slidably mounted (Fig.2). In a disc-shaped Recess of the connection fitting 2 is one of the same Material as the part 10 existing thrust washer 13 also Slidably mounted in the axial direction (Fig.2). Between the pressure plate 10 and the varistor element 8 and between the Thrust washer 13 and the varistor element 8 are current transfer elements 14 arranged, which in each case as a disc with concentrically guided around the axis and in the two end faces the disc formed grooves are formed (Fig.3). The current transfer elements 14 are advantageous with soft annealed aluminum formed.

From Fig.2 it can be seen that each of the reference numerals 15, 16 marked slot-shaped sections in essentially transverse to the axis z of the outer surface of the Electric connection fitting 1 and 2 extends over the axis z is. Each of the two ends of the loop 5 is above the axis z out into the slot-shaped section 15 or 16 introduced and lies in each case on a slit-shaped section 15 and 16 delimiting surface 17 and 18 (Figure 3). This ensures that the loop 5 in the area of Axis z is held centrally and a uniform contact pressure ensured in the arrester active part. A uniform Current density of the occurrence of an overvoltage in the arrester active part Guided arrester current is guaranteed. At the same time, inadmissibly high levels of local warming occur Arrester active part avoided.

Increased security against shifting the loop across Axis z is given when the slots 15, 16 opposite the axis by slightly more than 90 °, for example by up to 95 °, are inclined and / or if the slots 15, 16, the loop ends have fixing undercuts, which in the Support surfaces 17, 18 may be formed.

Advantageously, the support surfaces 17, 18 substantially circular arc-shaped surface profile. The loop ends then lie with a uniform, relatively small Curvature on the connection fittings 1, 2 on. This will be undesirably large bending and shearing stresses of Loops largely avoided.

A rectangular, in particular a square, cross-sectional profile the loop 5 with a relative small width transverse to the axis z is particularly advantageous because then the slit-shaped section 15 or 16 only must be extended slightly over the axis z addition. The connection fitting 1 or 2 then has a high mechanical Strength on.

The connection fittings 1, 2 are partial, the varistor elements 8, the printing plates 10, 13 and the loop 5 are completely from a shielded cast housing 19 of insulating material, preferably of an elastomeric Silicone, enclosed (Fig.1).

To make the active part of the series after the connection fitting 2, the pressure plate 13, one of the Current transfer elements 14, the varistor element 8, another Stromübergangselement 14, the pressure plate 10, the two Spring elements 9 and the connection fitting 1 in a template stacked and with a biasing force applied. The connection fittings 1, 2 are doing so aligned such that the two slot-shaped sections 15, 16 congruent superimposed (Figures 2 and 3). thereupon is a prefabricated loop 5, which preferably made a wound, band-shaped prepreg, which after the Winding was cured so deep into the slots 15, 16 pushed until the loop ends of the axis z be penetrated. The biasing force is then canceled and the arrester active part is completed. By Twisting the pressure screw 4 can additionally contact and Holding force to be generated in the arrester active part.

Instead of a prefabricated loop can also be a loop used during the manufacture of the surge arrester is formed. For this purpose, a with a biasing force applied band around the arrester active part wound and on the two bearing surfaces 17, 18 stored. Here are the two connection fittings 1, 2 under the formation of contact force firmly clamped together and thereby a mechanically stable active part of the produced Surge arrester formed. For a good mechanical Strength of the arrester active part extends this tension in the general already completely off. When using a Bandes with sufficient elasticity, such as one out Optionally, fiberglass fabricated tape may therefore be used the spring elements 9 omitted.

Preferably, such a band is a prepreg, in particular based on glass fibers and epoxy. A prepreg points a good adhesion effect. One from a toughened one Therefore, prepreg wound loop is also after winding stable without additional fastening device and can then Cured at elevated temperatures. This forms then one of glass fibers and one of the glass fibers embedding, hardened plastic matrix existing loop.

By bracing the two connection fittings 1, 2 is in addition to a good contact of the individual in the current path between the two connection fittings located parts at the same time a nestling of the grooves of the current transfer elements 14 to the end faces of the varistor element 8 and the Pressure discs 10, 13 reached. During the subsequent pouring the Ableiteraktivteils with insulating material, preferably on the base of an elastomeric silicone, the penetration of liquid insulating material between the individual in the current path located so avoided parts.

LIST OF REFERENCE NUMBERS

1, 2

connection fittings

3

threaded hole

4

pressure screw

5

loop

6, 7

material recesses

8th

varistor

9

spring elements

10

thrust washer

11, 12

screw holes

13

thrust washer

14

Current transfer elements

15, 16

slit-shaped sections

17, 18

support surfaces

19

cast housing

z

axis

Claims (11)

1. Active part for an overvoltage suppressor having two connecting fittings (1, 2) which are spaced apart from one another along an axis (z), having at least one cylindrical varistor element (8) which is arranged between the two connecting fittings (1, 2) and a clamping part which holds the connecting fittings (1, 2) and the at least one varistor element (8) together forming contact force and has a loop (5) made of insulating material, characterized in that in each case one material cutout (6, 7) is formed in each of the two connecting fittings (1, 2) with a section (15, 16) which runs essentially transversely with respect to the axis (z), is designed in the form of a slot and extends from the outer surface of the fitting (1, 2) to beyond the axis (z), and in that the loop (5) is inserted into the sections (15, 16), which are in the form of slots, in the two connecting fittings (1, 2) in the region of the loop ends beyond the axis (z), and each of the two loop ends rests on in each case one surface (17, 18) which bounds the section (15, 16) which is in the form of a slot.
2. Active part according to Claim 1, characterized in that the contact surface (17, 18) has a surface profile which is essentially in the form of a circular arc.
3. Active part according to one of Claims 1 or 2, characterized in that a cutout in the form of a disc is formed in at least one of the two connecting fittings (1, 2) in order to accommodate at least one spring element (9) which produces the contact force and/or a thrust washer (10, 13).
4. Active part according to one of Claims 1 to 3, characterized in that the loop (5) contains a wound strip.
5. Active part according to Claim 4, characterized in that the wound strip is embedded in a plastic matrix.
6. Active part according to Claim 5, characterized in that the plastic matrix is formed by curing the curable plastic before the loop (5) is placed on the contact surfaces (17, 18).
7. Active part according to Claim 5, characterized in that the plastic matrix is formed by curing the curable plastic after the loop (5) is placed on the contact surfaces (17, 18).
8. Active part according to one of Claims 1 to 7, characterized in that the loop (5) has a rectangular cross-sectional profile.
9. Active part according to one of Claims 1 to 8, characterized in that at least one current transmission element (14), which can be deformed when the contact force is formed, is provided in the current path between the two connecting fittings (1, 2).
10. Active part according to Claim 9, characterized in that the current transmission element (14) is designed as a disc and has grooves which pass concentrically around the axis (z) and are formed in end surfaces of the disc.
11. Overvoltage suppressor having an active part according to one of Claims 1 to 10 and having a moulded housing (19) which at least partially sheaths at least one varistor element (8) and the clamping part and is made of insulating material.

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