EP0384347A1 - Surge protector for connection arrangement, particularly of a telephone equipment - Google Patents

Abstract

Line protection module comprising at least one tubular arrestor (3) held in position between end contacts (13, 13A) connected to pieces (6, 7) which are integral with the carrier structure of the module, one (7) forming an earth piece, the other bearing, via a contact (12), on a conductive connection strip (8A, 8B) contacting two conductive tabs (4A, 4B), one (4A) connected to a wire of the line to be protected, the other (4B) to a jumper wire, the said module further comprising a timed arrangement for taking the arrestor out of circuit and for cutting the line wire-jumper wire connection. The timed arrangement for taking the arrestor out of circuit is thermally coupled with the latter through a low melting point solder connecting two parts of the conductive connecting strip of which one terminates in a precurved end which, after the solder melts, bears on a piece connected to the earth piece, this solder causing, through rapid opening of a contact, the taking out of circuit of this arrestor, the cutting of the electrical continuity of the connection strip and the communicating with the earth of the second conductive tab (4B). <IMAGE>

Description

The present invention relates to a line protection module, in particular for a telephone connection block, comprising at least one arrester of tubular shape held in position between end contacts connected to parts integral with the support structure of the module, one of said parts, said mass part, opening to the outside by a first contact resting on a part connected to the mass arranged in correspondence on a wall of the support structure, the other of said parts coming to bear by a second contact on a conductive connecting strip coming into contact with two conductive tabs, a first tab being provided to be connected to a wire of the line to be protected, a second tab being provided to be connected to a jumper wire serving local equipment to which must be connected to the line, said module further comprising a timed arrangement for switching off the arrester e t break in the connection between line wire and jumper wire, triggered by a rise in temperature in the module, due to a permanent current flowing to the ground through the surge arrester, above a lower threshold value at the softening temperature of the insulating material constituting at least the part of the support structure to which said mass piece is subjected, this timed arrangement for switching off the arrester being thermally coupled with it by an element sensitive to elevation of temperature of the arrester above a determined threshold, which causes by rapid opening of a contact the deactivation of this arrester, the interruption of the electrical continuity of the connecting blade and the communication with the earth of the second conductive tab.

A module of this kind, of drawer type, was the subject of patent application FR-A-2560458 by the applicant. The timed arrangement for switching off the surge arrester following excessive heating of the latter resulting from a long-term overvoltage on the line, is formed therein according to a first variant. by a fusible insulating pad and an extension of the conductive connecting strip associated with the surge arrester, this extension developing beyond the contact area of this strip with the bottom tab and towards the ground piece, so as to take support on this mass piece by elastic return after melting of the insulating stud which is inserted between this extension and this mass piece, and which is fusible at the temperature threshold value. According to another variant, the conductive connecting strip is arched between its midpoint and a bulge in contact with the bottom tab, and this bulge is maintained by elastic stress in contact with the bottom tab due to the support of the end of the extension of the conductive connecting strip on the fusible insulating stud, the melting of this stud causing the opening of the contact between the bottom tongue and the connecting strip at the level of the bulge.

Although these devices provide good protection for the surge arrester in the event of a long-term overvoltage in the supply line, they have the drawback of ensuring only a very slow opening of the contact by crushing the pad and not to operate at a well-defined temperature, because one can practically use as a fusible insulating material only a thermoplastic polymer, which undergoes progressive softening and crushing in a fairly large temperature range. We are therefore led to choose a threshold temperature significantly lower than the softening temperature of the thermoplastic material of the drawer, which leads us to accept in certain cases a deactivation of the arrester while the temperature reached by it does not is not yet dangerous for the drawer material.

The object of the present invention is to provide a lightning arrester protection module which works quickly and at a precise temperature, which can therefore be chosen to be fairly close to that causing the softening of the thermoplastic material of the drawer, and which does not therefore switch off the arrester, while cutting the connection between the line wire and the jumper wire, only when the temperature reached really risks causing deterioration of the supporting structure.

The protection module according to the invention is characterized in that the conductive connecting strip consists of two parts connected by a low-melting point weld forming the member sensitive to the temperature rise of the module, its first part being connected to the first tab, and its second part connected to the second tab ending on the side of the weld by a pre-cambered end, of pre-camber so that after fusion of the weld this end comes to bear on a part connected to the part massive.

When the module comprises two surge arresters in parallel, it preferably includes two conductive connecting blades and two arrangements for setting the circuit of the corresponding arrester comprising in common the grounding piece.

When the module comprises a three-pole surge arrester, it preferably comprises two conductive connecting blades and two arrangements for deactivating the arrester in common comprising the grounding part.

• La figure 1 représente en coupe longitudinale par son plan médian un module de protection à deux parafoudres bipolaires, dont un seul est visible.
• La figure 2 représente schématiquement le fonctionnement d'un module de protection à deux parafoudres bipolaires.
• La figure 3 représente schématiquement le fonctionnement d'un module à un parafoudre tripolaire.

It is described below, by way of example and with reference to the figures of the appended drawing, a lightning protection line protection module for telephone connection block.

• Figure 1 shows in longitudinal section through its median plane a protection module with two bipolar surge arresters, only one of which is visible.
• FIG. 2 schematically represents the operation of a protection module with two bipolar surge arresters.
• FIG. 3 schematically represents the operation of a module with a three-pole surge arrester.

The protection module shown in Figure 1 is designed to be embedded in a cell of a connection block consisting of a stack of wafers each composed of a row of cells. Such connection blocks, used at the input of telephone exchanges, make it possible to connect the telephone lines served by these exchanges to local equipment and to protect the latter from overvoltages transmitted by the lines. following incidents such as lightning strikes or contact with power transmission lines. For this purpose, each incoming line is associated with a protection module containing as many lightning arresters as there are line wires, or a three-pole lightning arrester module corresponding to a double number of line wires. This module is in the form of a drawer which is housed in a cell assigned to the line.

Conventionally, as many bottom tabs such as 4A are provided in each cell as there are bipolar arresters in a protection module, or a double number if it includes one or more three-pole arresters. This protection module is in the form of a drawer which is housed in a cell assigned to the line.

Each cell, of rectangular parallelepiped shape, comprises on some of its walls of insulating material, conductive tabs intended to ensure the electrical connections between the line, equipment and ground wires and corresponding conductive elements of the protection module.

Each cell is provided, depending on whether it is provided with bipolar or three-pole surge arresters, as many so-called bottom tabs as 4A as there are surge arresters, or a double number of such tabs. These bottom tabs are arranged longitudinally and in parallel on a first half of one of the large internal faces of the cell, from the bottom; they open out through the bottom of the cell and each externally comprise a conventional connection device, for example with an insulation displacement slot, for at least one wire (not shown) of the incoming line.

Each cell is also provided with as many tabs, said to be input, such as 4B, as there are bottom tabs. These inlet tabs 4B extend longitudinally in parallel from the cell inlet on a second half of the large internal face carrying the bottom tabs 4A; they open to the outside of the cell entry each by a connection device for at least one so-called jumper wire intended to be connected to the local equipment served by the line in question.

Finally, each cell is provided with as many tabs, called mass, such as 5, as there are surge arresters. These mass tabs extend longitudinally in parallel from the bottom over the greater part of the large internal face opposite to that carrying the bottom and inlet tabs, and they open out through the wall of the face which carries them. so as to come into contact with a ground connection not shown.

Thus a mass tab 5 is arranged opposite a bottom tab 4B which corresponds to it and which is itself aligned with a corresponding input tab.

A protection module 1 is in the form of a drawer intended to be removably fitted into a cell. This drawer has a supporting structure of insulating material 2, which is capable of sliding between the walls of a cell.

This supporting structure encloses the lightning arresters such as 3, of the tubular type, which are arranged therein longitudinally and in parallel. Each surge arrester, of the gas type, has a connection tail corresponding to each of its electrodes. In the case of bipolar surge arresters, corresponding to FIG. 1, the arrester has a connection tail (13, 13A) at each end. These two connection tails are each inserted into a slot of two conductive holding pieces 6 and 7 secured to the support structure of the drawer on either side of the arrester 3. There are as many holding pieces 7 as there are surge arresters in the drawer, and as many holding pieces 6, or a double number, depending on whether the surge arresters are bipolar or tripolar.

The holding pieces 7 are called mass pieces. They are arranged in parallel at the bottom of the drawer and each comprise a contact pad read opening outwards and at the end of the drawer to come to bear on a ground tab 5 when the drawer is in place.

The holding pieces 6 are arranged in parallel at the top of the drawer and each comprise a connector pad such as 12 coming to bear on a conductive and elastic connecting blade 8A, 8B, which is subject to the supporting structure of the drawer outside a wall located on the other side of this drawer relative to the connector pads 12. The blades 8A, 8B are arranged longitudinally, parallel to each other, so that each of them, appropriately arched at one end, comes from the insertion of the drawer to contact an input tab 4B and the tab of bottom 4A aligned to ensure electrical continuity between the line and garter wires respectively connected to these tabs.

For this purpose, each connecting blade, enclosed by its ends in the support structure of the drawer, comprises at least one contact area near each of its ends for connection with the tongues. This contact area is generally formed by a bulge 10 or 11 which is pressed against the tongue concerned 45A or 4B by elastic effect when the drawer is put in place.

In the embodiment shown in Figure 1, each holding part 6 or 7 is constituted by a conductive strip which is connected and split in the center, at its fold and perpendicular to this fold, to allow the wedging of one connection tails 13, 13A of the arrester.

One of the ends of each retaining part 6 or 7 is shaped so as to form a shoe 12 or 10, while the other end elastically increases the support pressure of the shoe by pressing on a bulge, such as 16 or 17, formed upstream of the shoe on the blade which forms it.

According to the invention, the conductive and elastic blade of laision is not unitary, but formed of two elements 8A, 8B joined by a low-temperature fusible weld at 9. The element 8B of the connecting blade comprises nearly the weld a pre-cambered part 15, provided on its face facing the arrester with a contact pad 18, the camber of this part 15 being such that in the absence of the solder its end comes to bear on the body of the arrester.

The welding of the two elements of the conductive strip at 9 is chosen from an alloy having a substantially frank melting point below the softening temperature of the insulating material constituting the supporting structure of the drawer.

Thus, if the drawer is made of a polycarbonate softening from 140 ° C., an alloy close to a ternary eutectic rich in bismuth such as the Darcet alloy with a weight composition of 50% bismuth, 25% of will be chosen. tin and 25% lead, melting at 96 ° - 98 ° C, or Newton's alloy with 50% bismuth, 18.8% tin and 31.2% lead, melting at 96 ° -97 ° vs.

In the event of an overvoltage occurring on a line wire, the arrester concerned starts and a current flows through the line wire to ground through the bottom tab 4A, the connecting tail 8A-8B, the holding part. 6 by means of the pad 12, the arc produced in the arrester, the ground piece 7 and the ground tab 5 via the pad 14.

If the overvoltage created generates an intensity greater than that admissible for the line wires, for example in the event of contact of a wire with a conductor of an electrical energy distribution network, the arrester 3 starts and heats up. Its radiation causes the weld 9 to heat up, which melts after a certain period corresponding to its rise to its melting temperature, and releases the end 15 of element 8B from the elastic connecting strip. This end comes into contact with the envelope of the arrester by its contact pad 18, and thus earths the input tab 4B by means of the holding part 7 and the ground tab 5. The electrodes of the arrester are thus switched off.

FIG. 2 represents the electrical diagram of the connections in a protection module with bipolar surge arresters in normal operation and in the event of a permanent overvoltage producing the fusion of the solder at 9. The welds of the connecting blades are represented by three-terminal contacts 20 , 21. Normal operation is represented by the positions of the contacts in solid lines, and operation in the event of a permanent current flowing, risking to produce a softening of the plastic of the supporting structure of the drawer, by the positions of the contacts in dashed line.

In normal operation, the current flows from the bottom tabs 4A, 4C to the input tabs 4B, 4D via the connecting blades. In the event of an overvoltage on one of the lines connected to the bottom tabs 4A, one of the surge arresters 3A, 3B initiates and flows the current to earth 22 by means of its holding part 7 and the ground tabs shown by the earth connection 23. If this overvoltage persists sufficiently to abnormally heat the corresponding arrester, under the effect of the thermal coupling represented by one of the segments 24A, 24B, the fusion of the solder causes the contact to be established, no longer between the tabs 4A, 4B, but between the tab 4B and the ground by means of the envelope of the arrester and of the corresponding mass piece and mass tab.

FIG. 3 represents the electrical diagram of the connections in a three-pole surge arrester protection module 23. In normal operation, the current flows from the bottom tabs 4A, 4C to the input tabs 4B, 4D via blades link (positions in solid lines of the three-terminal contacts 20, 21). In the event of an overvoltage on one of the lines connected to the bottom tabs 4A, 4C, the arrester strikes between the electrode corresponding to the line in question and the electrode connected to the ground tab and flows the current to earth. If the overvoltage persists enough to abnormally heat the arrester, under the effect of the thermal coupling represented by one of the segments 24A, 24B, the fusion of the corresponding solder causes the contact to be established, no longer between the tabs 4A, 4B and 4C, 4D, but between one of the tabs 4B, 4D and the earth via the envelope of the arrester, the ground piece and the corresponding ground tab.

Claims (3)

1 / Line protection module, in particular for telephone connection block, comprising at least one arrester (3) of tubular shape held in position between end contacts (13, 13A) connected to integral parts (6, 7) of the support structure of the module, one of said parts, called mass part (7), emerging outside by a first contact (14) resting on a part (5) connected to the mass arranged in correspondence on one wall of the support structure, the other (6) of said parts coming to bear by a second contact (12) on a conductive connecting blade (8A, 8B) coming into contact with two conductive tabs (4A, 4B), a first tab (4A) being provided to be connected to a wire of the line to be protected, a second tab (4B) being provided to be connected to a jumper wire serving local equipment to which the line must be connected, said module comprising at besides a temporis arrangement é (8B, 9) for switching off the surge arrester and cutting the connection between the line wire and the jumper wire, triggered by a rise in temperature in the module, due to a permanent current flowing to the earth through the arrester, above a threshold value lower than the softening temperature of the insulating material constituting at least the part of the supporting structure to which said mass piece (7) is subject, this timed arrangement for switching off the arrester being thermally coupled thereto by a member sensitive to the rise in temperature of the arrester above a determined threshold, which causes by rapid opening of a contact the deactivation of this arrester, the interruption of continuity electrical connection blade and the communication with the mass of the second conductive tab (4B), characterized in that the conductive link blade (8A, 8B) consists of two parts are connected by a low melting point weld (9) forming the member sensitive to the temperature rise of the module, the first part (8A) being connected to the first tab (4A) and the second part (8B) connected to the second tab (4B) ending on the side of the weld by a pre-cambered end (15), of precambrage such that after fusion of the weld this end comes to bear on a part connected to the mass part. 2 / Module according to claim 1, comprising two surge arresters in parallel (3A, 3B) fig.2), characterized in that it comprises two conductive connecting blades and two arrangements (20, 21) for switching off the corresponding arrester comprising in common the grounding part (23). 3 / Module according to claims 1 or 2, comprising a three-pole arrester (3) fig.3), characterized in that it comprises two conductive connecting blades and two arrangements (20, 21) for switching off the arrester comprising at common the grounding piece (23).

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