EP0466048B1 - Fault-current interruption switch - Google Patents

Description

The invention relates to a switching device according to the preamble of claim 1.

A known switching device of this type (US-A-3,240,901) has a housing with two connecting pieces provided at the axial ends, the housing being divided into chambers in the axial direction. In order to carry out repeated interruptions, there is a vacuum interrupter in a front chamber with a stationary and a switch contact movable in the axial direction of the housing, which can be adjusted by means of an toggle lever arrangement arranged in a central housing chamber via an external actuating device. The vacuum interrupter is assigned an opening spring which, when the switching contacts of the vacuum interrupter are closed, is latched in the mechanically pretensioned state in such a way that the switching contacts remain in the closed state. The vacuum interrupter is also associated with a magnetic element which, depending on the current flowing through the vacuum interrupter, exerts magnetic effects on a magnet armature which is coupled to the latching of the opening spring. If a fault current that exceeds the normal operating or overcurrent occurs, the magnetic element moves the magnet armature, which releases the latching of the opening spring via a linkage and rocker arrangement, so that the switching contacts of the vacuum interrupter are opened. The disadvantage here is that a special adjustment device is required on the magnet armature in order to be able to compensate for effect tolerances between the magnet element and the magnet armature, and it is a relatively complex construction volume demanding linkage and rocker arrangement necessary to transmit the triggering force occurring on the magnet armature to release the latch.

A switching device is also known (DE-A-1 808 730), in which a vacuum switching chamber is placed on an outer end face of a housing axially divided into chambers, from which the extension shaft of a movable switching contact projects into the housing and on the one hand with a mechanical actuator coupled and electrically connected in series with an actuating coil which is arranged coaxially to the actuating linkage of the vacuum interrupter. In the switched-on position of the switching contacts of the vacuum interrupter, the switching linkage is latched by means of a permanent magnet. If an increased fault current flows through the vacuum interrupter in this arrangement, the actuating coil generates in a metal disk which is firmly connected to the shift linkage a force component which is opposite to the force of the latching magnet and which is greater than the holding force of the magnet. As a result, the switching contacts of the vacuum interrupter are automatically opened when high fault currents occur. With this construction, the coordination of the opposing magnetic forces requires special care.

The invention has for its object to take measures in a switching device according to the preamble of claim 1, by which a reliable release of the latch is achieved with a simple structure and without adjusting means.

This object is achieved according to the invention by the characterizing features of claim 1.

In a configuration of a switching device according to the invention, the extension shaft of the movable switching contact is used as the primary conductor of a current transformer, the secondary coil of which directly feeds a ring coil of the magnetic release. Mechanically moved and adjustable parts for the detection of the fault current and for transmission to the magnetic release are therefore not necessary.

Appropriate embodiments of the inventive concept are specified in the subclaims.

• Fig. 1: Schaltvorrichtung im Schnitt in eingeschalteter und und ausgeschalteter Stellung.
• Figur 2: Einbau der Schaltvorrichtung in einer metallgekapselten, gasisolierten Schaltanlage; (einphasige Darstellung)
• Figur 3: Schaltschema des Sekundärkreises innerhalb der Schaltvorrichtung.
• Figur 4: Schaltschema des Sekundärkreises mit Kapazität.
• Figur 5: Schaltvorrichtung mit gewickeltem Kondensator.
• Figur 6: Schaltvorrichtung mit Plattenkondensator.

For a better understanding of the invention, reference is made to the following drawings:

• Fig. 1: Switching device in the cut in and and off position.
• Figure 2: Installation of the switching device in a metal-enclosed, gas-insulated switchgear; (single phase representation)
• Figure 3: Circuit diagram of the secondary circuit within the switching device.
• Figure 4: Circuit diagram of the secondary circuit with capacity.
• Figure 5: Switching device with a wound capacitor.
• Figure 6: Switching device with a plate capacitor.

A particularly advantageous embodiment of the inventive concept is shown in FIG. The housing of the switching device according to the invention has a cylindrical shape and is divided into two parts inside. In the upper room there is the vacuum interrupter 1, the fixed contact 1a of which is connected to the connector 2 via the conductor spiral 23. With the help of the spiral-shaped conductor 23, a magnetic field is generated which runs almost parallel to the switch axis in the open contact gap between the switching contacts 1a and 1b and thus improves the switching capacity of the vacuum interrupter in a known manner. Subsequent to the partition 8, which divides the housing into two parts, is the second room, in which the current transformer 4, the magnetic release 5, the opening spring 9 and the latch 10 are housed.
The second room is closed by the second connector 3. The essential part of the first space is enveloped by the insulating tube 6, while the second part of the housing is closed off by the metal tube 7. In this way, when the switching chamber is open, the recurring voltage at the switching contacts is present at the porcelain tube of the vacuum switching chamber 1 as well as at the ends of the insulating tube 6. Because inside the If there is a contamination-free environment for the vacuum interrupter chamber 1, the length of the ceramic tube can be significantly smaller than the length of the insulating tube 6, which can also be exposed to unfavorable environmental influences.

The current transformer 4 consists of a ring core 4a and a secondary coil 4b, while the shaft of the movable switching contact 1b or its extension 25 serves as the primary conductor. The latter is connected to the second connection piece 3 via a sliding contact 24 and is therefore flowed through by the primary current during operation. The magnetic release 5 includes an annular coil 5 and a ferromagnetic body 5b surrounding it on three sides, the lower leg of which is designed in such a way that it has a minimal air gap with respect to the magnet armature 5c movable in the vertical direction. The latter is under the action of a return spring 14, which presses it into its rest position when the ring coil 5a is not energized, forming the air gap 26 in the vertical direction relative to the ferromagnetic body 5b (left side of FIG. 1). The current transformer 4 and the magnetic release 5 form an annular gap with respect to the extension 25, in which in the present example the switch-off spring 9, which is supported with its upper end on the partition 8, is arranged. The lower end of the switch-off spring 9 rests on the pressure piece 10b, which in turn is supported over an inclined surface by means of the clamping bodies 10a in the axial direction on the support plate 10c and in the radial direction on the armature 5c (left side of FIG. 1). On the pressure piece 10b is also supported via the tube 11, the lower end of the contact force spring 12, which are designed in the present example as disc springs, and whose upper end acts on the shaft of the movable switching contact 1b of the vacuum switching chamber 1 via the shoulder 21. The pin 15 attached in the extension 25 ensures that the two switching contacts 1a and 1b in the switched-off state do not exceed the stroke h. The pin 15 interacts either with the lower surface of the pressure piece 10b or, as drawn in FIG. 1, with a groove 30 machined into the pressure piece (right side of FIG. 1). At the lower connection piece 3 there is a screw spindle 18, with the aid of which the vacuum interrupter 1 can be switched on again after each power interruption and the opening spring 9 can be tensioned until it is latched. The screw spindle in the tensioned position of the opening spring 9 is drawn on the left side of FIG. However, the switching device according to the invention is only ready for switching after the screw spindle 18 has been turned back into the starting position, namely when the required distance between the lower surface of the pressure piece 10b and the upper edge of the screw spindle 18 has been established. In order to enable easy assembly of the switching device according to the invention, it is advisable to screw the lower connecting piece 3 into the metal tube 7.

In the simplest embodiment of the switching device according to the invention, a spiral conductor 23 for generating an axial magnetic field can be dispensed with. No additional external energy source is required for the secondary circuit. Rather, the secondary winding 4b of the current transformer 4 is connected directly in series with the ring coil 5a.

• a) Induktion eines entsprechenden Sekundärstroms in der Sekundärwicklung 4b, der gleichzeitig in der Ringspule 5a ein magnetisches Feld im ferromagnetischen Körper 5b induziert. Dieses wirkt auf den Magnetanker 5c und zieht diesen entgegen der Kraft der Rückstellfeder 14 in den Luftspalt 26, bis der Magnetanker 5c mit der Unterkante des ferromagnetischen Körpers 5b in Berührung kommt.
• b) Die nun nicht mehr in radialer Richtung abgestützten Klemmkörper 10a werden von der Schrägfläche des Druckstücks 10b nach außen bewegt und geben den Ausschalthub des Druckstücks frei.
• c) Unter der Wirkung der Ausschaltfeder 9 bewegt sich das Druckstück 10b bis zu einem nicht dargestellten Anschlag nach unten und nimmt dabei über die Nut 30 und den Stift 15 den beweglichen Schaltkontakt 1b mit, bis der Schalthub h zwischen den Schaltkontakten 1a und 1b erreicht ist.

If an interference current occurs in the primary circuit, the following processes take place in succession in the switching device:

• a) induction of a corresponding secondary current in the secondary winding 4b, which simultaneously induces a magnetic field in the ferromagnetic body 5b in the toroidal coil 5a. This acts on the magnet armature 5c and pulls it against the force of the return spring 14 into the air gap 26 until the magnet armature 5c comes into contact with the lower edge of the ferromagnetic body 5b.
• b) The clamping bodies 10a, which are no longer supported in the radial direction, are moved outward from the inclined surface of the pressure piece 10b and release the switch-off stroke of the pressure piece.
• c) Under the action of the opening spring 9, the pressure piece 10b moves down to a stop, not shown, and takes the movable switching contact 1b with it via the groove 30 and the pin 15 until the switching stroke h between the switching contacts 1a and 1b is reached .

The shutdown is now complete.

1 shows the switched-on state on the left side and the switched-off state on the right side. Since the extension 25 or the shaft of the movable switching contact 1b penetrates the lower boundary surface of the connecting piece 3, the end face 25a can either be provided with a display device for the disconnection that has taken place, or with a mechanism with the aid of which an assigned disconnector moves into the disconnected position becomes. This can be done by means of a mechanical linkage to the switch-off energy store of the disconnector or via an auxiliary contact which triggers the switch-off energy store by an electrical pulse.

• d) mit der Schraubspindel 18 erfolgt eine Aufwärtsbewegung des Druckstücks 10b, bei der gleichzeitig die Ausschaltfeder 9 gespannt und die Schaltkontakte 1a und 1b zur Wiederanlage gebracht werden.
• e) nach erfolgter galvanischer Berührung der Schaltkontakte 1a und 1b wird im weiteren Verlauf der Drehung an der Schraubspindel 18 die Verklinkung 10 in ihre Sperrstellung gebracht.Dies geschieht mittels der auf den Magnettanker 5 c wirkenden Rückstellfeder 14, wobei die Klemmkörper 10 a über die schräge Fläche 29 in ihre Ausgangsstellung unter die schräge Fläche des Druckstücks 10b bewegt werden. Während dieses Vorganges stellt sich zwischen Nut 30 und Stift 15 ein kleiner Überhub ein, der zur betriebssicheren Erzeugung der erforderlichen Kontaktkraft durch die Kontaktkraftfeder 12 benötigt wird.
• f) die Schraubspindel 18 wird in Ihre Ausgangsstellung zurückgedreht, um den für eine weitere Ausschaltung erforderlichen Freiweg für das Druckstück 10b herzustellen.

The restart of the switching device according to the invention will now be described in the further course:

• d) with the screw spindle 18 there is an upward movement of the pressure piece 10b, in which the switch-off spring 9 is simultaneously tensioned and the switching contacts 1a and 1b are brought into reinstallation.
• e) after the galvanic contact of the switching contacts 1a and 1b has taken place, the catch 10 is brought into its blocking position in the further course of the rotation on the screw spindle 18 return spring 14 acting on the magnet armature 5 c, the clamping bodies 10 a being moved over the inclined surface 29 into their starting position under the inclined surface of the pressure piece 10 b. During this process, there is a small overstroke between groove 30 and pin 15, which is required for the reliable generation of the required contact force by the contact force spring 12.
• f) the screw spindle 18 is rotated back into its starting position in order to produce the free travel required for the pressure piece 10b for a further deactivation.

As a further feature of the invention, the screw spindle 18 can be designed such that, in addition to its function as a switch-on mechanism for the vacuum switching chamber 1, it also serves as a stop for the pressure piece 10b during each switch-off process.

In Figure 1 it can also be seen that the connecting pieces 2 and 3 have connection surfaces 2a and 3a, which can be used as an adapter for the terminal contacts of HV fuses. However, other connection surfaces can also be used in the same way.

With the switching device according to the invention, for example, a ring cable switchgear according to FIG. 2 with two cable connections in the lower part of the encapsulation and with a transformer branch in the upper part, in which the residual current protection is integrated into the encapsulation, without using a complete functional circuit breaker got to. Since the switching device according to the invention is a self-sufficient unit which does not require any external energy and in which no replacement of components is required after the fault current has been interrupted, it can be fully incorporated into the encapsulated switching insert. In this case, the same high level of insulation applies to them as for all other equipment installed in the switchgear.

As an example, the ring cable switchgear system according to FIG. 2 has two three-position switches 32 in its lower part, with which the ring cable can be connected to the busbar 37 or with which each individual cable can be disconnected or grounded. The busbar 37 is connected at the top to a further three-position switch 32, to the switching contacts of which the switching device according to the invention is connected to interrupt fault currents. This switching device is constructed via two clamping contacts 35 and associated insulators on the encapsulation 31; the switching device is oriented so that the second connector 3 faces one of the walls of the encapsulation. The screw spindle 18, not shown, is extended by the insulating shaft 19, which is guided gas-tight to the outside of the switchgear. With your help, either by hand or with a motor drive 34 after the fault current has been interrupted, the switching device 33 can be switched on again or the switch-off spring 9 can be tensioned and latched.

The switching device according to the invention is a single-phase switching device. The end face 25 a (not shown) (see FIG. 1) of the switching device 33 according to the invention can be connected to the associated three-position switch 32 with a linkage 36 in order to generate a disconnection of the branch after a fault current interruption. In networks with rigid star earthing or if this is necessary for other reasons, this three-position switch should also be equipped with single-phase actuation.

FIG. 3 shows how the connection between the three single-phase switching devices 33 and a three-phase switch-disconnector 32a takes place by means of an electrical control, and how fault current interruptions do not occur in one phase must lead to the disconnection of the load break switch 32a, but only a two- or three-phase fault current interruptions leads to the final disconnection of the circuit. Each movable switch contact 1b of the switching device 33 is connected to a two-pole auxiliary switch 39 arranged outside the encapsulation 31. The auxiliary switches 39 of all three phases are connected to one another in such a way that an auxiliary contact of two phases is connected in series with one another and is connected to the shunt release of the energy store 38. The energy store can be switched off arbitrarily both via the button 41 and the energy source 40 and, in the event of a fault, via the auxiliary switch 39. The connecting lines between the auxiliary switches 39 of the individual phases are switched such that the shunt release of the energy store 38 is only live when the vacuum interrupters 1 have been interrupted in two phases. In the case of a single-phase interruption, only one contact auxiliary switch is closed, so that there is no control voltage at the energy store.

The switching device according to the invention according to FIG. 1 can also be used very advantageously in air-insulated switchgear. In such cases, the housing is designed and sealed so that corrosive influences from the environment cannot penetrate into the interior of the switching device. The length of the insulating tube 6 is also adapted to the harsher environmental influences.

In some applications, it is desirable not to trigger the device immediately in the event of a fault. In conventional switchgear, adjustable overcurrent protection relays are used, with which the response time of the release can be changed. However, such relays have the major disadvantage that they have to be checked at certain time intervals. This however, this is only permitted if the branch is disconnected.

Longer tripping times can be achieved with the switching device according to the invention according to a further feature by adding a capacitance 28, preferably parallel to the ring coil 5a of the magnetic release 5 according to FIG. The capacitance can be designed according to FIG. 5 as a cylindrical capacitor 28 a. The cylindrical capacitor 28 a is advantageously arranged in a gap between the secondary winding 4 b of the current transformer 4 and the metal tube 7 of the housing. The two pads are connected according to the circuit diagram of Figure 4 with the outputs of the secondary winding 4 b and the toroidal coil 5a. According to another feature of the invention, a plate capacitor 28 b can also be used as a capacitance for influencing the switch-off time for the switching device. This plate capacitor 28 can advantageously be arranged between the current transformer 4 and the magnetic release 5. Here, too, the connection is made according to the circuit diagram in FIG. 4. In all cases, openings b 42 are provided in the ferromagnetic body 5 b, through which the electrical connections to the capacitors or to the secondary coil 4 a of the current transformer 4 are made.

Claims (27)

1. Switching device for interrupting fault currents, preferably for outgoing transformer circuits in medium-voltage switchgear, comprising a housing (6, 7) provided with two connectors (2, 3) - in which housing are housed a vacuum interrupter chamber (1), which is adapted to carry out repeated interruptions, is actuated from a power supply with at least one cut-out spring (9), and comprises a fixed and a moving contact (1a, 1b) - and a tripping device which only becomes active when a fault current occurs and which comprises a latch (10) for the cut-out spring (9) which can be released by an electromagnetic magnetic tripping device (5) by means of a magnetic armature (5c), characterised in that an extension shaft (25) of the moving switch contact (1b) forms the primary conductor of a current converter (4) provided with a secondary coil (4b), in that the magnetic tripping device (5) has an annular coil (5a) for tripping the latch (10), and in that the secondary coil (4b) of the current converter (4) supplies the annular coil (5a) of the magnetic tripping device (5).
2. Switching device for interrupting fault currents according to claim 1, characterised in that the housing comprises in a first chamber the vacuum interrupter chamber (1) and means for connecting its fixed switch contact (1a) to the first terminal (2), and in that the moving switch contact (1b) penetrates with its shaft or optionally with an extension (25) a partition wall (8) leading to a second chamber, in which the remaining operating means (4, 5, 9, 10) and a displaceable contact connection (24) between the shaft of the moving contact (1b) or optionally the extension (25) and the second connector (3) are incorporated.
3. Switching device for interrupting fault currents according to claim 2, characterised in that the housing has a cylindrical shape, into which the vacuum switching chamber (1) and the remaining operating means (4, 5, 9, 10) are fitted in a coaxial arrangement, in that an insulating tube (6) closed at the front face with the first connector (2) forms at least in part the casing of the first chamber, and in that a metal tube (7), which is closed off from the first chamber by the partition wall (8) and in whose end face the second connector (3) is set, forms the casing of the second chamber.
4. Switching device for interrupting fault currents according to claim 2 or 3, characterised in that fitted in the second chamber of the housing are, starting from the partition wall (8), the current converter (4) consisting of an annular core (4a) surrounding the shaft of the moving switch contact (1b) or optionally its extension (25) and a secondary winding (4b), the magnetic tripping device (5) consisting of an annular coil (5a) and a ferromagnetic body (5b) enclosing the annular coil except in an air gap (26) for a displaceable magnetic armature (5c), and the latch (10) of the cut-out coil (9).
5. Switching device for interrupting fault currents according to claim 4, characterised in that the current converter (4) and the magnetic tripping device (5) form, relative to the shaft of the moving switch contact (1b) or optionally its extension (25) an annular gap for receiving the cut-out spring (9) which bears on the partition wall (8) and a pressure member (10b) of the latch (10).
6. Switching device for interrupting fault currents according to claim 5, characterised in that in the switched-on position of the vacuum interrupter switch (1) the pressure member (10b) acts on clamping bodies (10a) disposed on the circumference via an inclined face in such a manner that the latter bear with an axial component on a support plate (10c) and a radial component on the inner face of the magnet armature (5c).
7. Switching device for interrupting fault currents according to claim 6, characterised in that the annular coil (5a) acted upon by a fault current draws the magnet armature (5c) into the air gap (26), whereupon the clamping bodies (10a), under the action of the radial components of the cut-out spring (9) and unlocking the device by means of the pressure member (10b) move outward and trigger the cut-out motion of the moving contact (1b).
8. Switching device for interrupting fault currents according to one of claims 4 to 7, characterised in that the magnetic armature (5c) has an inclined end face (29) which, after bracing of the cut-out spring (9) and under the action of a restoring spring (14) guides the clamping bodies (10a) into their locked position and holds them there.
9. Switching device for interrupting fault currents according to claim 2 or one of the subsequent claims, characterised in that in the shaft of the moving contact (1b) or optionally in its extension (25) a pin (15) is mounted, to which the pressure member (10b) transmits the force of the cut-out spring (9) during opening of the vacuum interrupter switch (1).
10. Switching device for interrupting fault currents according to claim 9 or one of the preceding claims, characterised in that between a step (21) on the shaft of the moving switch contact (1b) and the pressure member (10b) or optionally with the interposition of a tube (11), a contact force spring (12) is provided, which when the vacuum interrupter switch (1) is cut out bears on the pin (15).
11. Switching device for interrupting fault currents according to claim 1, characterised in that the cut-out spring (9) can be stressed via a threaded spindle (18) mounted in the base of the second connector (3).
12. Switching device for interrupting fault currents according to claim 11, characterised in that the threaded spindle (18) is actuatable from outside a covering (31) of the switchgear via an insulating shaft (19).
13. Switching device for interrupting fault currents according to either of claims 11 or 12, characterised in that a motor drive (34) is provided for stressing the cut-out spring (9) and for switching on the vacuum interrupter switch (1), which is equipped with means for automatic operation after elimination of a fault, which include the automatic reversal of the threaded spindle (18) after carrying out the switching-on movement.
14. Switching device for interrupting fault currents according to claim 1 or one of the subsequent claims, characterised in that the connectors (2, 3) have adapters (2a, 3a) for receiving the switching device in clamp contacts (35) provided for high-power fuses.
15. Switching device for interrupting fault currents according to claim 2, characterised in that as a displaceable contact connection, a sliding contact (24) is provided, whose elements are guided on the connector (3).
16. Switching device for interrupting fault currents according to claim 1 or one of the subsequent claims, characterised in that between the first connector (2) and the fixed switching contact (1a) a conductor in the form of a coil is provided for generating an axial magnetic field for the switching section of the vacuum interrupter switch (1).
17. Switching device for interrupting fault currents according to claim 16, characterised in that the conductor (23) is wound in a spiral manner and with its outer end is conductively connected to the first connector (2) and with its inner end to the fixed switching contact (1a).
18. Switching device for interrupting fault currents according to claim 17, characterised in that the shaft of the fixed switching contact (1a) is held by means of a threaded connection (27) mounted in an insulated manner in the first connector (2).
19. Switching device for interrupting fault currents according to claim 2 or 3, characterised in that the shaft of the fixed switching contact (1a) is connected to the inner face of the first connector (2) by means of a threaded connection.
20. Switching device for interrupting fault currents according to claim 1 to 4, characterised in that the secondary winding (4b) of the current converter (4) and the annular coil (5a) of the magnetic tripping device (5) are connected in series.
21. Switching device for interrupting fault currents according to one of claims 1 to 4, characterised in that the annular coil (5a) of the magnetic tripping device is connected in series with the secondary winding (4b) of the current converter and a capacitor (28) is connected in parallel preferably to the annular coil.
22. Switching device for interrupting fault currents according to claim 21, characterised in that the capacitance is formed as a wound capacitor (28a) and is disposed around the turn (4b) of the current converter (4).
23. Switching device for interrupting fault currents according to claim 21, characterised in that the capacitor is formed as a plate capacitor (28b) and is disposec between the current converter (4) and the magnetic tripping device (5).
24. Switching device for interrupting fault currents according to claim 1 or one of the subsequent claims, characterised by means with which the cut-off motion of the moving switch contact (1b) or its extension (25) can be transferred to separate an associated disconnector or load interrupter switch (32a).
25. Switching device for interrupting fault currents according to claim 24, characterised in that the end (25a) projecting from the housing acts on the power source (38) of the disconnector or load interrupter switch (32a) via a linkage (36) and effects its separation after a fault current interruption by the vacuum interrupter switch (1).
26. Switching device for interrupting fault currents according to claim 24, characterised in that the ends (25a) projecting from the housing act on auxiliary contacts (29) which are preferably disposed outside the casing (31) and with which, after a fault current interruption, a working current tripping device in the power supply (38) of the disconnector or load interrupter switch can be acted on.
27. Switching device for interrupting fault currents according to claim 26, characterised in that the switching devices (33) cooperate respectively with two auxiliary currents (39), and in that each auxiliary contact is connected by two different phases to the other auxiliary contact and in series with the working current tripping device of the power supply (38).

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