DE19545505C1 - Surge arrester for low-voltage, high power fuse - Google Patents

Abstract

The surge arrestor has at least one voltage dependent resistance (ie varistor) and several thermal cut-outs. There is a fuse housing 910) with metal end caps in which is an anti-surge fuse(4) electrically and mechanically connected at both end caps. The defect indicator is an isolated component fastened detachably to the fuse housing which after being detached, can be moved relative to the housing by a spring. W When the fuse melts, the fastening of the indicator inside the housing is released. The thermal trip is outside the fuse housing and is thermally connected to the varistor so that if unpermitted heat generation occurs in the varistor, the trip is activated and a defect is indicated.

Description

The invention relates to a surge arrester with at least least a voltage dependent resistor (varistor) and thermal cut-off devices consisting of a fuse strips and a thermal release with eutectic enamel alloy, whereby with separation of the security streak fens or thermal release by spring force indicator moved and thus made visible (Oberbe handle of claim 1). Such a surge arrester is usually used in low voltage systems, especially in NH fuse bases.

An overspan voltage arrester of the aforementioned type is from DE 77 19 678 U1 known. Here are one of the damage indicators Plate, the security strip, the thermal release and a adjoining voltage-dependent resistor (varistor) electrically and mechanically connected in series or to each other attached. The aforementioned components, including one additional spark gap provided in the row arrangement are housed in a common housing. A trigger sefeder is supported between a base plate and the plate of the damage indicator. Between the two above Plates is the security strip including the solder place firmly clamped. He is therefore constantly under one  tension resulting from the release spring. It got in practice has shown that excessive mechanical bean stress (e.g. shaking during transport) under tension tear up standing security strips. Also can vary according to length Fatigue the material of the security strip during the storage period and the Siche under the constant tension streak mechanically damage what its trigger character teristics can change. As a result, the overvoltage head unusable. The mechanical row arrangement of the aforementioned triggering means, the varistor and the spark gap cke required a corresponding space in the longitudinal direction of the surge arrester. In the event of a short circuit it happens by melting the security strip that he with the sand surrounding him of such a protection melts and thereby prevents it from being pressed out Spring force is prevented or even locked. This has the disadvantageous consequence that the display of the trigger is not or only partially in the position indicating the release ge reaches.

From DE 76 12 790 U1 a display device for electri cal fuse links known, at which to a Security strip in the form of a fuse element a fuse wire of the display device is arranged in parallel. Of the Fusible wire is with an indicator of the display device connected. When the fuse wire melts, the the indicator is under spring tension position one. Otherwise, this reference deals with with the problem of creating a so-called sintered bead, when the fuse element melts between it and forms the extinguishing sand. There is a risk that the Indicator fuse wire not fast enough melted and fixed by the solidifying sintered bead will hold. This is similar to the disadvantage explained above to DE 77 19 678 U1. On the special problem of the advertisement switching off or becoming unusable of a span voltage arrester according to the preamble of claim 1,  which both the consequences of a short-circuit current and the Consequences of inadmissible heating of the varistor eliminated DE 76 12 790 U1 does not give a hint and also no suggestion.

Finally, from DE 19 55 494 U1 is a switching state transmitter known for electrical fuses, where after responding the melt insert and lead out the indicator to A slide is released for the purpose of displaying the switching status will. This slide has the radio after its release tion of a switch to a contact device of a siche actuation lower part. This reference too does not provide any information or suggestions on how to report a damage Surge arrester according to the preamble of the claim 1.

The task or problem of the invention is in contrast, both in the case of aging arising inadmissible leakage current of the varistor, as well in the event of a surge current that is too high, a short circuit in the Varistor generated, the short circuit of security strips is interrupted, with simple means and in a space-saving manner Construction for an indication of the error that has occurred gene.

To solve this task or problem is according to the characterizing part of claim 1 initially provided that a surge current-proof fuse strips in a fuse housing arranged with metallic end caps and electrically and is mechanically connected to the two end caps that the Damage indicator a separate, detachable on the fuse housing attached and after loosening this attachment by the spring Component movable relative to the fuse housing, wherein an arrangement is provided such that when the Security strip the attachment of the damage indicator stored within the fuse box, d. H. Approved and that the thermal release is outside the safe  tion housing and with the varistor in a heat is conductive connection, the thermal release and the thermally conductive connection are designed so that at a inadmissible heating of the varistor the separation of the Thermal release and thus a damage report is made.

So the two above are in such a span voltage arrester with varistor possible damage and are displayed. In addition, it will work out for itself DE 76 12 790 U1 known advantage achieved that the spring and the spring indicator is not a mecha niche connection with the security strip. Consequently the constant force of this spring is not a pull transferred force to the security strip. Rather pulls the force of the spring only on the damage indicator or with it connected component. If the security strip that over the two end caps of the fuse housing are contacted, too hot and melts due to a short circuit this for the release or separation of the attachment of the Damage indicator used and the spring can then in to move its display position. The related Disadvantages described to the prior art are avoided. The advantages of such a security strip and its Tripping behavior is retained. It is an advantage ner that the thermal release is not in the fuse housing, but is located outside of it and with the varistor in such a thermally conductive contact is that at a inadmissible heating of the varistor the thermal release he follows. This is advantageously this thermal release separated from the security strip and can also from this not be influenced thermally. With the presence a surge current-proof fuse strip is guaranteed that this surge arrester has the required stress when used in a power supply network or withstands the like.

The features of claim 2 serve to simplify and also reducing the footprint by doing the same  Damage notification both when the fuse indicator melts gers, as well as in the case of thermal release.

An embodiment of the invention is recommended Claim 3. According to this, an identification wire is provided the damage indicator directly or via an attached to it Component against the spring force in the "no display" position stops and is connected to the security strip in such a way that the indicator wire either when the Security strip is separated, or that the Kennmel wire with the electrical supply and discharge lines of the safety approximately in an electrically conductive connection is that after the fuse strip has melted total short-circuit current flows over the indicator wire and this immediately melts.

The features of claim 4 achieve in the case of thermo triggered by moving the fuse housing with means the required display, preferably preferred the same spring that is used to move the Display after the fuse strip has melted and of the indicator wire is provided. This arrangement, esp particular in the preferred embodiment, has included Lich the fuse housing and its components a considerable Lich space-saving design, so that with the same equipment housing volume higher performance data, e.g. B. by means of a its dimensions larger Vatistor can be achieved.

The features of claim 5 contain an advantageous mechanical-thermal design of a connection between the fuse housing and the outside of this housing located varistor with the help of a thermal bridge and the Thermal release. This is particularly advantageous Way with the melting of the thermal release so far in fuse box firmly held in its operating position released in its entirety, so that the spring it in the  Bring display position, can preferably move. This can (see above) using the same spring or spring arrangement happen according to the previous remarks a melting of the security strip also the Scha brings the indicator into the display position. In each of these The operator of the system has been warned of damage and thus compelled by the surge arrester in question to replace a new device.

According to claim 6, it is a constructive and practical before preferred embodiment of the invention, the thermal release one of the metal end caps of the fuse housing to attach while the other metallic end cap to their electrical connection and for the sliding storage of the Damage indicator serves. Located between the two end caps the security strips and the inside of the housing Identification wire. This also becomes a very compact and space-saving structure of the arrangements of this surge arrester reached because its length is essentially on the The length of the fuse housing is reduced.

The fuse housing, damage indicator and varistor are according to claim 11 can be accommodated in a single housing. It are not external components for damage reporting and / or a backup is required. Rather, these are components all integrated in one device.

Further advantages and refinements of the invention are the others Subclaims and the execution described below Possibilities of the invention, including the zugehö see drawing below. The drawing shows:

Fig. 1 and Fig. 1a, the electrical connection of two comments submitted to the invention,

Fig. 2 shows in perspective the dung structural and constructive structure of an embodiment according to the OF INVENTION,

Fig. 3 is a section according to the line III-III in Fig. 2, wherein no tripping and therefore no trip indication is made,

Fig. 3a shows a section of Fig. 3 after a release of the securing strip and corresponding display,

FIG. 3b shows a section according to FIG. 3 after initiation of the thermal release and the appropriate display,

Fig. 4 shows a section through the fuse with a damage indicator

Fig. 5 is a plan view of the embodiment of FIG. 2 omitting parts not of interest here.

In Fig. 1, 1a, the only dash-dotted and schematically indicated surge arrester 1 with the outer connections 2 , 3 is shown. In it are, also indicated schematically, the security strip 4 , a varistor 5 , a thermally influenced thermal trip 6 and optionally, ie if necessary, another surge in the form of a spark gap 7 , preferably a gas arrester.

The embodiment according to Fig. 1a corresponds substantially to the omitted in FIG. 1 with the exception that the additional spark gap 7 and is replaced by a short-circuiting bridge 7 '.

The structural construction of an embodiment according to the invention can be seen in FIGS. 2 to 5.

Fig. 2 shows the surge arrester 1 with its housing 8 and two connecting blades 9 , which are used for insertion into corre sponding mating contact openings and electrically correspond to the connections 2 , 3 from FIGS. 1, 1a. In the housing B of the surge arrester, a fuse housing 10 is provided with an upper end cap 11 and a lower end cap 12 , the aforementioned expressions "upper" and "lower ren" refer only to the illustration in FIG. 2. In the upper end cap 11 , a movable damage indicator 14 is provided, the actuation and function of which will be explained below. Further, Fig. 2 shows a spring 26 and which is only schematically numbered 6 on the lower end cap 12, a thermal tripping. The heat of the varistor 5 is conducted via a thermal bridge 17 to the thermal release 6 and triggers there if the heating of the varistor becomes too great. The thermal release 6 is connected to the end cap 12 via a sheet 16 attached to it.

The upper end cap 11 is connected via a connecting plate 19 to the upper connecting knife 9 , while an electrical connection, not shown in the drawing, between the varistor 5 and the lower connecting knife 9 . This is mechanically the electrical circuit of FIGS. 1 and realized 1a, wherein additionally an overvoltage protection in the form of a spark gap, a Gasablei preferred diester in accordance with point 20 in FIG. 3 (1 corresponds to numeral 7 in Fig.) Into a space 21 can be provided within the housing 8 . If such overvoltage protection is not required, a short-circuit bridge 20 '(corresponds to number 7 ' according to FIG. 1a) can take its place. The short circuit bridge can be a metal tube adapted in shape. Short-circuit bridge and gas arrester preferably have the same outer contour, so that they can be accommodated in the same recess in the housing 8 of the surge arrester. They are in conductive contact with an adjacent metal plate and thus the relevant supply or discharge of the surge arrester.

The fuse housing 10 shown in more detail in FIGS. 3 to 5 with the metallic end caps 11 , 12 can correspond in its construction to a conventional fuse. According to the sectional view of Fig. 4 of the securing strip 4 is electrically conductively connected both to the bottom end cap 12 and also secured to the upper end cap 11 and with these. The security strip 4 consists of a fusible material and is also provided with predetermined breaking points 18 . Furthermore, an indicator wire 22 is arranged within the fuse housing 10 , which is fixedly attached with its lower end 22 'to the lower end cap 12 and at the same time electrically contacted. The upper end 22 '' of the Kennmel derdrahtes is attached to the shaft 13 of the damage indicator 14 . This shaft 13 is guided within a bore 23 of the upper end cap 11 in the direction of the double arrow 24 . On the shaft 13 there is an abutment plate 25 , which extends approximately perpendicular to the longitudinal direction of the shaft 13 and serves as an abutment for two compression springs 26 . In particular, Fig. 3, 3a and 3b it can be seen that these springs 26, one with her, the upper end cap 'supported on the abutment plate 25, while its cap opposite, the lower end 12 facing end 26' 11 facing end 26 ' is supported on a corresponding abutment 27 of the housing 8 of the surge arrester.

The securing strip 4 is preferably contacted on the metallic end caps 11 , 12 . It is designed both in its materi al and in its dimensions so that it does not trigger in normal size surge discharge currents, z. B. at a normal discharge current of 10 kA. Rather, the fuse strip is dimensioned so that it melts and triggers only in the event of a defective arrester or in the event of an overload due to the resulting correspondingly high short-circuit current. According to the inven tion, this triggering causes the attachment of the damage indicator 13 , 14 on the fuse housing to be removed or released. This can be done in various ways, for example due to the melting temperature of the fuse strip and the heat generated thereby. In the present, preferred exemplary embodiment of the invention, the relatively thin identification wire 22 is connected in parallel to the security strip 4 . When the fuse strip melts, the current profile that previously occurred through it is no longer available and the short-circuit current flows via the indicator wire 22 . This will melt immediately due to its small cross-section, so that the previous hold of the damage indicator 13 , 14 given by the indicator wire is no longer present in the position shown in FIG. 4. The springs 26 pressing on the abutment plate 25 can now press this plate with the damage indicator 14 upwards in FIG. 4 or to the right according to FIG. 3a. The damage indicator 14 thus comes into its display position within a transparent dome 31 . In this triggering due to the melting of the security strip, the Sicherheitsge housing 10 remains in the starting position (see Fig. 3 and 3a) and it is only the damage indicator 14 pushed ver by means of the spring 26 .

It is essential, as already explained at the beginning, that the springs 26 act only on the indicator wire 22 , but not on the security strip 4, which is sensitive to the material. This is without mechanical tensile stress inside the hedging housing 10 electrically and mechanically connected to the end caps 11 , 12 .

As already indicated, the thermal release 6 in the form of a eutectic soldering point serves to interrupt the current flow through the device if the varistor 5 is heated to an unacceptably high degree. This also removes the previous hold of the fuse housing in the position of FIGS. 2 and 3, which existed on the associated sheet metal 16 by means of the intact thermal release 6 , due to the melting of the solder of the thermal release 6 . Then the springs 26 can move the fuse housing 10 over the abutment plate 25 , which is held firmly in this position by the indicator wire 22 , from the position in FIG. 2 upwards or from the position in FIG. 3 to the right. The fuse housing 10 with the damage indicator 14 thus assumes the position shown in FIG. 3b. The springs 26 , which in another embodiment could also be designed as tension springs, therefore cause the damage indicator 14 to be moved into the display position of FIGS . 3a and 3b in both possible triggering cases. In contrast to the design according to the state of the art explained at the beginning, the thermal release is removed from the immediate vicinity of the security strip and thus from the security area and deliberately moved outwards, ie here to the outside of the fuse housing 10 or the associated end cap 12 . Thus, their thermal release is only influenced by the heating of the varistor 5 and the thermal bridge 17 , this heat being supplied via the thermal bridge 17 and the strip 16 to the corresponding solder mass. The thermal fuse 6 is thus limited to the varistor and the thermal bridge and thereby reliable protection against inadmissible heating of the varistor 5 . The varistor 5 can become defective for two reasons. Firstly due to aging and secondly due to an excessively high surge current, which creates a short circuit in the varistor. In the former case, an impermissible leakage current flows, so that the varistor heats up to an impermissibly high level and the thermal triggering takes effect. In the second case, an increased follow current (short circuit current) flows, which is interrupted by the fuse strip.

Only one display 14 is provided in the transparent dome 31 , which applies to both triggering cases. The surveillance person must replace the surge arrester in any case of a damage report.

The explained structure of this preferred embodiment of the Invention has several advantages. So the wiring can finished assemblies, namely a special cylinder lock with security strips and indicator wire.

A separate back-up fuse for the arrester in its application is not necessary, since the integrated special cylinder fuse ensures this function in addition by means of the fuse strip 4 , which is advantageously integrated into this fuse.

In the top view of FIG. 5, the space-saving accommodation of the fuse housing 10 and the varistor 5 in the housing 8 is shown schematically here. In the z. B. rectangular device housing 8 , the fuse is housed with its housing 10 in the area of a corner. The varistor 5 can be positioned in an inclined position, ie approximately in the diagonal between a corner 28 and the opposite corner 29 of the aforementioned rectangle. This allows a varistor with a relatively large width to be placed in the desired standard dimensions on a relatively small footprint.

The entire surge arrester can be made watertight. This is advantageous for installation in distribution systems where moisture can occur. The dome 31 made of glass or a transparent plastic can be pressed watertight via seals 32 into an upper plate or cover 30 of the device housing. This results in a closed housing with a degree of protection that is also suitable for use in damp conditions.

Claims (13)

1. Surge arrester with at least one voltage-dependent resistor (varistor) and thermal switch-off devices, which consist of a security strip and a thermal release with eutectic melting alloy, whereby a damage indicator is actuated by opening the security strip or the thermal release by spring force and is thus made visible, thereby characterized in that a fuse housing ( 10 ) with metallic end caps ( 11 , 12 ) is provided, in which electrical and mechanical connections with the two end caps are connected to a surge current-proof fuse strip ( 4 ) that the damage indicator ( 14 ) is a separate, is releasably attached to the fuse housing and after releasing this attachment by the spring ( 26 ) relative to the fuse housing movable component ( 13 , 14 ), an arrangement being provided such that when the security strip melts, the attachment of the damage indicator within the fuse Housing is lifted, ie released, and that the thermal release ( 6 ) is arranged outside the fuse housing ( 10 ) and with the varistor ( 5 ) in a thermally conductive connection ( 17 ), the thermal release and the thermally conductive connection are designed so that if the varistor heats up inadmissibly, the thermal release ( 6 ) is disconnected and a damage indicator is displayed. 2. Surge arrester according to claim 1, characterized in that the same damage indicator ( 14 ) serves both for the display of the melting of the security strip ( 6 ) and for the display of the separation of the Thermoauslö solution. 3. Surge arrester according to claim 1 or 2, characterized in that an indicator wire ( 22 ) is provided which holds the damage indicator ( 14 ) directly or via a component ( 13 ) attached to it against the spring force in the position "no display" and in connection with the security strip is such that the indicator wire is either cut when the security strip ( 4 ) melts, or that the indicator wire is connected to the electrical supply and discharge lines of the fuse housing in an electrically conductive connection such that after the security strip has melted the Whole short-circuit current flows over the indicator wire and this melts immediately. 4. Surge arrester according to one of claims 1-3, characterized in that with the separation of the thermal release ( 6 ) a displacement of the Sicherheitsge housing ( 10 ) is released by spring force, the spring force preferably being effected by the same spring ( 26 ), which moves the display ( 14 ) relative to the fuse housing into the display position after the fuse strip has melted. 5. Surge arrester according to one of claims 1-4, characterized in that the thermal release ( 6 ) is attached to the fuse housing and that of it via the heat-conducting connection ( 17 ) also a mechanical connection between the fuse housing ( 10 ) and the outside of this housing located varistor ( 5 ) is formed, wherein the heat-conducting connection ( 17 ) leads to a heat-emitting point of the varistor, which is firmly connected to the housing ( 8 ) of the surge arrester, so that the fuse housing ( 10 ) against this when the thermal release is not separated the force of the spring ( 26 ) is held in its operating position ( Fig. 3). 6. Surge arrester according to one of claims 1 to 5, characterized in that the thermal release ( 6 ) is located on the end cap ( 12 ) of the fuse housing ( 10 ) which is opposite to the other end cap ( 11 ) of the fuse housing, in which the damage indicator ( 13 , 14 ) is movable, preferably slidably guided. 7. Surge arrester according to one of claims 1 to 6, characterized in that the fuse housing ( 10 ) in the region of its damage indicator ( 14 ) having end cap ( 11 ) via a resilient connecting plate ( 19 ) with the electrical contact in this area of the device housing ( 8 ), preferably the associated connection knife ( 9 ) is connected. 8. Surge arrester according to one of claims 1 to 7, characterized in that the spring for moving the damage indicator ( 14 ) or the fuse housing ( 10 ) in the respective display position ( Fig. 3a or Fig. 3b) from one or more compression springs ( 26), on the one hand (26 ') of the shaving dens indicator (14) and the other part (26 on an abutment (25)' ') 27) of the housing (8) supported on an abutment (the surge arrester, or brace. 9. surge arrester according to one of claims 1 to 8, characterized in that a spark gap or a gas arrester ( 20 ) is installed in a recess ( 21 ) of the housing ( 8 ) of the surge arrester and is thus used in the electrical series connection. 10. Surge arrester according to claim 9, characterized by a short-circuit bridge ( 20 ') which in place of the spark gap or the gas arrester ( 20 ) in the Ausneh line ( 21 ) of the housing ( 8 ) can be introduced and at the same time inserted into the electrical series connection. 11. Surge arrester according to one of claims 1 to 10, characterized in that the fuse housing ( 10 ), the damage indicator ( 14 ) and the varistor ( 5 ) with thermal release ( 6 ) are within a common housing ( 8 ) of the surge arrester. 12. Surge arrester according to one of claims 1 to 11, characterized in that the housing ( 8 ) of the surge arrester is rectangular or square in plan view, that the fuse housing ( 10 ) with the associated components in the region of one of the corners of the rectangle or squares, while a varistor ( 5 ) is arranged approximately in the diagonal between the two corners of the rectangle or square, each of which is adjacent to the first-mentioned corner. 13. Surge arrester according to one of claims 1 to 12, characterized by a watertight design including a transparent dome ( 31 ) in which the damage indicator ( 14 ) is in its display position.