FR2788857A1 - Voltage collector for detection of directional or power loss type electrical defects in medium tension electrical circuits has a layered arrangement of conductor and isolators - Google Patents

Abstract

Electrical fault detection device works with a voltage collector device and is able to detect if a passing current in a part of network is active or reactive and works with a voltage device. The voltage collector connects to a current collector of capacitative divider type making electrical contact and being sealed at the same time. Device has a metallic insert (5) embedded in the isolator of a current measurement connection or separable connector (1). It comprises an internal conductor (14) connected to a cable (18,19) and adapted around a metallic screw (9) in a complementary shape. The screw (9) is locked in metallic insert (5). An intermediate isolator surrounds the whole of this interior assembly and is in turn surrounded by an external conductor (16) that has an extended annular skirt (22) that assures a sealed contact with a collar (6) that forms part of the conducting envelope (3) of the separable conductor.

Description

The present invention relates generally to the field of

  "medium voltage" electrical equipment. It relates more particularly to a potential tap for an electrical fault detector of the so-called "directional" or "wattmetric" type, in particular a fault detector operating with a capacitive voltage divider. A "directional" fault detector determines the direction of flow of a fault current in a part of an electrical network, and makes it possible to determine whether the current flow corresponds to an active or reactive power. It is a kind of voltage sensor, indicating a relative direction of current flow. Such a detector can be considered as a simplified embodiment of a "wattmetric" type detector. The MV electrical sockets, also called separable MV connectors, produced according to the NFC-33051 standard, have a capacitive divider used for checking that there is no voltage. Directional fault detection, using such sockets, requires knowing the voltage value, and the voltage divider is used for this purpose. In practice, a potential taking means must be adapted on the capacitive divider, in place of a cap usually mounted on the metal insert of the capacitive divider. As this particular device is not standardized, the various manufacturers of sockets do not currently offer universal, interchangeable and adaptable means for taking potential.

  sockets of the kind considered here.

  A particular embodiment of potential measurement, associated with a capacitive voltage divider, is described in French patent NI 9214535/2698696 in the name of the Applicant. This embodiment is not particularly studied for the realization of the seal, between the socket and the insert, in the form of a cap, hence the electric cable connected to the intermediate point (measuring point) of

capacitive divider.

  Starting from this state of the art, the present invention aims to provide a potential taking means, which can be fixed on the capacitive divider of all models of current sockets, can be connected

electrically, and be waterproof.

  To this end, the subject of the invention is essentially a potential tap for an electrical fault detector of the directional or wattmetric type, in particular a fault detector operating with a capacitive voltage divider of which one element is a metal insert embedded in an insulating part d '' a separable socket or connector, the potential tap consisting essentially, in combination: - of an electrically conductive inner element, electrically linked to a conductive cable leaving the potential tap, this inner element being resiliently adaptable to a metal screw with complementary conformation, tightened in the insert of the capacitive divider, - of an electrically insulating intermediate part, overmolding the internal element, and - of an electrically conductive external part, enveloping the internal element and the intermediate part and extended at one end by a suitable annular skirt ensuring tight contact on an annular flange surrounding the metal insert and forming part of the outer casing

  conductive separable connector.

  According to one embodiment of the invention, the internal element of the potential test is a part in semiconductor elastomer, overmolded on a stripped cable end, and having a central recess of complementary shape of the metal screw tightened in the insert of the capacitive divider. The external part of the potential test is also possible in semiconductor elastomer, while the intermediate part

  is available in electrically insulating elastomer.

  According to another embodiment of the invention, the internal element of the potential tap is a metallic element of tubular appearance, molded in the intermediate part and forming a plurality of elastic blades, separated from each other by slots , The end

  stripped of the cable being soldered or crimped on this metal element.

  In all cases, the internal element efficiently performs all the necessary functions, namely maintenance of the potential test, electrical contact and sealing: - the maintenance is ensured on the screw, which may in particular have a spherical head, by the elasticity of the inner part of the potential test - the semiconductor or metallic material of the inner element allows the electrical voltage to be transmitted from the screw to the cable, for measurement from the capacitive divider; - holding on the screw, accompanied by compression of the potential take-off, ensures pressure on the opposite face belonging to the capacitive divider, and consequently

a seal.

  In addition, the external part of the potential tap ensures by its flexible skirt the peripheral sealing, on the complementary part belonging to the capacitive divider, by accepting different diameters for this complementary part. Furthermore, being conductive, the external part of the potential tap maintains the ground continuity on the outside of this tap, by resting on the outer casing

  conductive separable connector.

  In a particular embodiment, a capacitor of the capacitive voltage divider is incorporated in the intermediate part

  insulator of the potential test, for better signal processing.

  As indicated above, the metal screw, tightened in the insert of the capacitive divider, can comprise a spherical head, on which is fixed elastically, with radial and longitudinal tightening, the internal element of the potential test. In variants, the screw has, for the same function, a conical or ogive protuberance, or even a groove

  annular semi-round profile, "V", ogive or other.

  The annular skirt, by which the conductive external part of the potential test performs the sealing and mass continuity functions, may comprise a simple annular sealing lip, facing inward. Alternatively, it may be an annular lip receiving a toric spring which presses it. According to another possibility, an O-ring is inserted under the annular skirt, the size of this seal being adapted to the dimensions of the complementary part belonging to the separable connector. The invention will in any case be better understood using the

  description which follows, with reference to the attached schematic drawing

  showing, by way of example, some embodiments of this potential tap for electrical fault detector Figure 1 is a sectional view of a potential tap according to the present invention, fixed on a separable connector with capacitive divider ; Figure 2 is a sectional view of another embodiment of the potential measurement according to the invention, shown apart from the separable connector; Figure 3 is a sectional view of a variant of the potential tap of Figure 1, with incorporated capacitor; Figures 4 and 5 are side views of variants of the screw, on which is fixed the potential object of the invention; Figures 6, 7 and 8 are side views, partially in section, of other variants of this potential test, with various configurations of the part ensuring sealing and / or adaptation on the separable connector. In FIG. 1 is partially shown a separable connector 1, with a capacitive voltage divider, on which a potential tap according to the invention is adaptable, generally designated by the

mark 2.

  The separable connector 1, fitted on the end of a line conductor, comprises an outer conductive envelope 3 made of elastomer, filled with an insulator 4 at a point of which an insert is embedded

  metal 5, constituting part of a capacitive voltage divider.

  The outer envelope 3 forms, around the insert 5, an annular flange 6.

  The part of the insulator 4, which coats the insert 5, extends in front of the annular flange 6 and is interrupted along a circular planar face 7. The metal insert 5 is flush with the circular planar face 7, in the center of this one. This insert 5 has a tapped blind hole 8, opening onto the flat face

circular 7.

  In the threaded hole 8 of the insert 5 is introduced and tightened a metal screw 9, which successively comprises: a threaded part 10, a hexagonal conformation 11 allowing its tightening, a frustoconical part

12 and a spherical head 13.

  The potential tap 2 comprises three overmolded elastomer parts 14, 15 and 16, arranged coaxially, their common axis being

designated by the reference 17.

  The innermost part 14 of the socket 2 is made of semiconductor elastomer, for example EPDM (ethylene propylene diene terpolymer) loaded with carbon. This part 14 is overmolded on a stripped end 18 of a conductive cable 19 with an insulating sheath, terminating on the side of the socket 2, and serving to transmit the potential drawn via the capacitive divider. The inner part 14 of the socket 2 has a central recess 20 opening out, the shape of which with constriction is complementary to the assembly formed by the frustoconical part

  12 and the spherical head 13 of the screw 9.

  The intermediate part of the socket 2 is made of electrically insulating elastomer, for example in uncharged EPDM. This intermediate part 15 surrounds the internal part 14, on its front side and on

its periphery.

  The outermost part 16 of the socket 2 itself envelops the intermediate part 15, and is made of semiconductor elastomer, for example made of carbon-laden EPDM. At its head end, this external part 16 forms a hooking ring 21, allowing a safety maneuver remote from the socket 2 using a pole. At its opposite end, the outer part 16 of the socket 2 projects beyond the inner 14 and intermediate 15 parts, and forms a flexible annular skirt

  22, provided with an annular sealing lip 23 facing inwards.

  For the installation of the potential plug 2, this is presented opposite the screw 9, and fitted by its central recess 20 on the spherical head 13 of the screw 9. This achieves the mechanical retention of the plug 2 , by complementarity of forms, the compression of the material of the inner 14 and intermediate 15 parts further ensuring a force support, therefore a blockage with sealing on the circular flat face 7 of the

separable connector 1.

  When the potential tap 2 is thus fixed, the inner part 14 of semiconductor material transmits electrical voltage between the screw 9, therefore the insert 5, and the cable 19, for the voltage measurement. The outer part 16, also made of semiconductor material, maintains the ground continuity between the outer casing 3 of the separable connector 1 and the outside of the potential tap 2, this continuity being ensured by the tightening of the flexible skirt 22 with lip 23 on the outside of the annular flange 6 of the casing 3. In addition, the pressure of lip 23 around

- -rT-

  this flange 6 provides external sealing, with adaptation to

  variations in diameters (within certain limits).

  In another embodiment of the potential tap 2, shown in FIG. 2, the inner elastomer part is replaced by a metallic element 24, of generally tubular appearance, overmolded in the intermediate part 15 of insulating elastomer. The metal element 24 has a plurality of profiled contact blades 25, separated from each other by slots 26, and joined together at one end of this element 24. The elasticity of the blades 25 allows their engagement and tightening on the spherical head 13 of the screw 9, to ensure mechanical tightening and electrical continuity. The stripped end 18 of the cable 19

  is here welded or crimped onto the metal element 24.

  According to another variant, illustrated by FIG. 3, a capacitor 27 belonging to the capacitive voltage divider is incorporated in the potential tap 2. The capacitor 27 is embedded in the insulating intermediate part 15, two connections 28, 29 connecting it,

  respectively, at the cable end 18 (therefore at the semi-internal part

  conductive 14), and to the semiconductor external part 16 (therefore grounded). FIGS. 4 and 5 illustrate variant forms of the metal screw 9, in particular of the part of this screw on which the potential tap 2 is fixed. In the case of FIG. 4, the spherical head is replaced by a conical protuberance 30, either constituting the tip of the screw 9 (see dotted line), or located behind the end of the screw (see line drawn). In the case of FIG. 5, the screw 9 has, on the contrary, an annular groove 31 with a "V" profile. Of course, the inner part of the potential tap 2 is, in each case, adapted to the particular shape of the screw 9, to allow the positioning and the

holdback.

  Finally, FIGS. 6, 7 and 8 illustrate variants relating to the production of the seal, at the level of the flexible skirt 22 of the external part 16 of the potential tap 2. According to FIG. 6, the skirt 22 forms a annular lip 32 turned inwards, an O-ring spring 33 being tightened around the lip 32. According to FIG. 7, the skirt 22 forms an annular lip 34 turned towards the outside, an O-ring spring 35 being engaged under this lip 34 According to FIG. 8, the skirt 22 does not have a lip, TTT 'but an O-ring 36 is inserted under the skirt 22, in a retaining groove, in contact with the flange 6; in this latter variant, the choice of the size of the O-ring 36 allows adaptation to various separable connectors. The potential tap 2, described above in various embodiments, can be used in particular on sockets or separable connectors 1 of straight or angled shape, associated with switchgear (circuit breakers, switches) or with transformers, on the

  "medium voltage" electrical networks (from 1000 V to 50,000 V).

  It goes without saying that the invention is not limited to

  forms of carrying out this potential gain which have been described below

  above, as examples; on the contrary, it embraces all of the variant embodiments and applications respecting the same principle. In particular, we would not depart from the scope of the invention by modifying the detail of the shapes of the potential tap 2 and of the screw 9, on which this plug is fixed, or by using other materials for making the various parts of this socket, or by providing special arrangements, such as a means for retaining the cable 19 in tension, for example by bending this cable or by bending its stripped end 18.

Claims (11)

  1 - Potential tap for electrical fault detector of directional or wattmetric type, in particular fault detector operating with a capacitive voltage divider, one element of which is a metal insert (5) embedded in an insulating part (4) of a socket current or separable connector (1), characterized in that it essentially consists, in combination: - of an interior element (14; 24) electrically conductive, electrically connected to a conductive cable (18, 19) starting from the socket potential (2), this inner element (14) being resiliently adaptable to a metal screw (9) with complementary conformation (13; 30; 31), clamped in the metal insert (5) of the capacitive divider, - by a electrically insulating intermediate part (15), overmolding the internal element (14; 24), and - an electrically conductive external part (16), enveloping the internal element (14; 24) and the intermediate part (15), and pr extended at one end by an annular skirt (22) capable of ensuring leaktight contact on an annular flange (6) surrounding the metal insert (5) and forming part of the conductive outer casing (3) of the separable connector (1).   2- potential test according to claim 1, characterized in that its inner element is a part in semiconductor elastomer (14), overmolded on one end of stripped cable (18), and having a central recess (20) complementary to the metal screw (9)   clamped in the insert (5) of the capacitive divider.   3 - potential test according to claim 1, characterized in that its inner element is a metallic element (24) of tubular appearance, molded in the intermediate part (1 5) and forming a plurality of elastic blades (25), separated from each other by slots (26), the stripped end (18) of the cable (19) being welded or crimped on this metallic element (24).   4- potential gain according to any one of the claims   1 to 3, characterized in that its outer part (16) is made of semiconductor elastomer, while its intermediate part (15) is made of insulating elastomer.   - Potential gain according to any one of the claims   1 to 4, characterized in that the metal screw (9), tightened in the insert (5) of the capacitive divider, comprises a spherical head (13), on which is fixed elastically, with radial and longitudinal tightening, the element interior (14 24) of the socket (2).   6 - Potential gain according to any one of the claims   1 to 4, characterized in that the metal screw (9), tightened in the insert (5)   of the capacitive divider, has a conical protrusion (30) or ogive.   7- potential gain according to any one of the claims   1 to 4, characterized in that the metal screw (9), tightened in the insert (5) of the capacitive divider, has an annular groove (31) of "V" profile, semi-round or pointed.   8- potential gain according to any one of the claims   1 to 7, characterized in that a capacitor (27) of the voltage divider   capacitive is incorporated in the insulating intermediate part (15).   9 - potential test according to claim 8, characterized in that the capacitor (7) has two connections (28, 29) connecting it respectively to the cable end (18) and to the external part conductive (16).   - Potential gain according to any one of   Claims 1 to 9, characterized in that the annular skirt (22) of the   conductive outer part (16) has a single sealing lip   annular (23), facing inward.   11 - Potential gain according to any one of   Claims 1 to 9, characterized in that the annular skirt (22) of the   conductive outer part (16) has an annular lip (32; 34)   receiving an O-ring spring (33; 35) which presses it inwards.   12 - Potential gain according to any one of   Claims 1 to 9, characterized in that an O-ring (36) is inserted   under the annular skirt (22) of the conductive outer part (16), the size of the seal (36) being adapted to the dimensions of the part   complementary (6) belonging to the separable connector (1).   13 - Potential gain according to any one of   Claims 1 to 12, characterized in that the outer part (16)   forms, at its front end, a hooking ring (21) for   remote maneuver using a pole.