EP1164617B1 - Current limiting system - Google Patents

Abstract

System for limiting current comprises a self-recuperating current limiting device (10) containing electrodes (1) made of solid metal for connecting to a wiring system to be protected and partially filled with liquid metal (7) with compressor chambers (4) lying between the electrodes. The chambers are made of pressure-tight insulating bodies (5) and an intermediate wall (12) with a connecting channel (8). Gas channels (13) controlled using a control device (31) extend into the current path formed by the liquid metal. Preferably the gas channels terminate directly close to a connecting channel or in a connecting channel. The gas channels run within an intermediate wall. The control device is connected to at least one gas channel via a gas pulse generator (32).

Description

The invention relates to a system for current limiting with at least one self-recovering current-limiting device according to the preamble of claim 1.

From the document SU922911A a self-recovering current-limiting device is known, which contains two electrodes of solid metal which are formed flatly to the interior of the current-limiting device and are separated by a first insulating body formed as a cylindrical, pressure-resistant insulating housing. Within the insulating housing are formed by insulating intermediate walls and interposed second insulating body, which are formed as annular sealing discs with liquid metal partially filled, one behind the other compressor spaces, which are connected to each other via filled with liquid metal, off-center connection channels of the intermediate walls. Thus, in normal operation, there is a continuous internal conductive connection between the electrodes via the liquid metal. In current limiting case, the liquid metal is suddenly displaced from the connecting channels due to the high current density. Thus, the electrical connection of the electrodes is interrupted via the liquid metal, which leads to the automatic limitation of the short-circuit current. After switching off or elimination of the short circuit, the connecting channels fill again with liquid metal, whereupon the current limiting device is ready for operation again. The document DE4012385A1 mentions vacuum, protective gas or an insulating liquid as the medium above the liquid level. To improve the limiting properties, the connecting channels of adjacent intermediate walls are arranged offset from each other according to document SU1076981A. It is known from document DE2652506A1 to use gallium alloys, in particular gallium-indium-tin alloys (GalnSn alloys), in contact devices.

A generic current-limiting device according to DE19853580C1 contains electrodes made of solid metal for connection to a circuit to be protected and with liquid metal partially filled, between the electrodes one behind the other compression chambers, the pressure-resistant insulating body and at least one of this held insulating intermediate wall are formed with at least one connecting channel.

Such current limiting devices are intended to effectively protect an electrical load or equipment from the adverse effects of excessively high currents, in particular short-circuit currents, by quickly limiting the faulty currents to an innocuous level after occurrence. These current limiting devices are adapted to be used in series with a conventional circuit breaker, in particular circuit breaker, by preferably using a current limiting device per current phase. It would be desirable if in a complex electrical system, the current limiting devices could react differently depending on the location and situation to erroneously high currents, for example, to allow in a branched system a selective on the associated level of supply of the current limit.

There are long known circuit breakers with means for detection and electronic evaluation, also known as electronic triggers, for example, according to document EP0989653A2. Furthermore, according to document EP0548390B1 a controllable by a device for detecting and evaluating a load current actuator with a pyrotechnic gas generator is known. Furthermore, according to EP0450104B1 or DE19740490C1 electrical switching devices are known, which have a drive device according to the eddy current principle, also referred to as Thomson drive, using a short-circuit ring and an electrical energy storage to interrupt the flow of current

DE904067C shows an overcurrent breaker in which a liquid mercury conductor is used as the internal contactor and the current interruption is introduced by the flow of a quenching gas into the mercury conductor. This overcurrent breaker is not self-recovery, but must be returned to the on state by a suitable movement.

The invention has for its object to provide a self-recovering system for current limiting, the current limiting property is variable under certain conditions.

The object is achieved by the characterizing features of the independent claim, while the dependent claims advantageous developments of the invention can be found.

By means of the at least one controllable means for the abrupt occurrence of gas in the current path formed by the liquid metal, a system capable of controllably triggering the current-limiting characteristic is formed in conjunction with a suitable control device. Only a small amount of gas per triggering process is required. The controllable means is the input side operatively connected to a control device, which may be arranged partially or completely separate from the current-limiting device. The liquid metal is partially displaced by the gas occurring, which abruptly the current carrying capacity of the remaining current path and thus the limit for the onset of the current limit is reduced by a significant extent, whereas without activation only at much higher currents would occur a current limit. With the invention, a controllable system is provided, the current limit is triggered when certain usable conditions occur. The controlled appearance of the gas advantageously occurs at a location or locations where the flow channel through the liquid metal is closer to the adjacent locations. This advantageously takes place in the immediate vicinity or in the interior of at least one of the connection channels. The number of partitions, the number of connection channels and the number of controllable means can be freely selected as required in a reasonable ratio.

Advantageous developments of the invention are that the at least one controllable means is designed either as a gas line or gas channel or as an ultrasonic probe. The triggering gas is injected in the first case directly into the current path. In the second case, a sufficiently high energy is released at the active end of the driven ultrasound probe, which leads to cavitation phenomena, i. leads to sudden formation of gas by negative pressure, and / or to local thermal evaporation of the liquid metal. Preferably, said controllable means extend within an intermediate wall or several intermediate walls.

An advantageous development of the invention is that the control of the at least one means for the jerky occurrence of gas is indirectly or directly controlled by a current-evaluating control device.

On the one hand, the current-evaluating control device can be connected via a gas generator generating a gas shock to said means in the form of a gas line or a gas channel. The gas impact generator may advantageously be designed as a per se known pyrotechnic generator or as a cylinder-piston device, for example as a known per se according to the eddy current principle operating device. On the other hand, the current-evaluating control device can be connected via a valve device to the named means in the form of a gas line or a gas channel, whereby the impulse-like delivery of compressed gas from a storage or supply device can be controlled via the valve device. The gas used is expediently protective gas, for example argon, nitrogen or sulfur hexafluoride. However, the use of air or other gases or gas mixtures should not be excluded.

The gas flow generator or the storage device forms a unit either with the current-limiting device or with a plurality of parallel current-limiting devices or is connected as a separate device via supply lines to the current-limiting device or the current-limiting devices.

In another advantageous embodiment of the invention, the current-evaluating control device can be operatively connected to said means in the form of an ultrasound probe, wherein suitably known electrical means for the controlled delivery of electrical energy of suitable frequency are interposed.

Advantageously, the current-evaluating control device is part of the electronic release of a circuit breaker, in particular a circuit breaker, wherein the electronic release with current detection devices which detect the phase currents of the circuit breaker connected or equipped. Conveniently, at least one current limiting device according to the invention is connected in series with the circuit breaker. The number of current-limiting devices according to the invention to be arranged in series with the circuit breaker can be smaller than the number of phase currents to be protected, the remaining phases can be connected without current-limiting device or with conventional non-triggerable current-limiting devices, for example according to the initially mentioned SU922911A.

With the triggerable current limiting devices, a feeder or outgoer protection switch can be equipped, connected or retrofitted within a branched system. Thus, a system for targeted current limiting is created in which the short-circuit level behind each of these current-limiting devices is halved, for example. The current limiting device is triggered by the trip unit of the associated circuit breaker, ie the function current limiting or the occurrence of the gas is switched according to demand, eg exceeding a detected by the triggering limit value, switched on. The advantages include a reduced nennstrombezoges short circuit level in downstream branches in spite of full feed-in, the cost-effective use of circuit breakers lower switching capacity for downstream supply levels, a lower thermal and magnetic Load of the switchgear in the event of a short circuit, a time selectivity which is possible to the full extent within certain current limits and the sensible combination of the functions disconnecting and current limits.

The current-limiting device which can be triggered by the current-evaluating control device, in particular the triggering device of a connected circuit breaker, has a limiting value which is quasi set by the current-evaluating control device. The thus made adjustment of the limit value of the current-limiting system can be made independent of nominal current by the customer or plant operator. The system according to the invention limits within wide limits the short-circuit level of the energy distribution to any desired level determined by the current-evaluating control device, with the possibility of total selectivity of the switchgear being provided. With such a system or with such systems, not only the system will be much cheaper to design, extensions are possible without reconfiguration and conversion.

Figur 1:

ein erste Ausführung der systemgemäßen Strombegrenzungseinrichtung im Längsschnitt;

Figur 2:

ein zweite Ausführung der systemgemäßen Strombegrenzungseinrichtung im Längsschnitt;

Figur 3:

ein erstes Ausführungsbeispiel des erfindungsgemäßes System mit Strombegrenzungseinrichtungen gemäß Fig. 1;

Figur 4:

ein zweites Ausführungsbeispiel des erfindungsgemäßes System mit Strombegrenzungseinrichtungen gemäß Fig. 1;

Figur 5:

ein Beispiel für einen Gasstoßgenerator im Längsschnitt als Einzelheit aus Fig. 4;

Figur 6:

ein drittes Ausführungsbeispiel des erfindungsgemäßes System mit Strombegrenzungseinrichtungen gemäß Fig. 2.

Further details and advantages of the invention will become apparent from the following, with reference to figures explained embodiments. Show it

FIG. 1:

a first embodiment of the system current limiting device in longitudinal section;

FIG. 2:

a second embodiment of the system current limiting device in longitudinal section;

FIG. 3:

A first embodiment of the inventive system with current limiting devices of FIG. 1;

FIG. 4:

a second embodiment of the inventive system with current limiting devices of FIG. 1;

FIG. 5:

an example of a gas impact generator in longitudinal section as a detail of Fig. 4;

FIG. 6:

A third embodiment of the system according to the invention with current-limiting devices according to FIG. 2.

The current-limiting device 10 according to FIG. 1 or the current-limiting device 20 according to FIG. 2 contains on both sides one respective electrode 1 made of solid metal, preferably copper, which is rotationally symmetrical and in an outer Connecting conductor 2 passes. Between the electrodes 1 there are a plurality of compressor chambers 4, which are formed by a corresponding number of annular sealing disks 11 and of insulating intermediate walls 12. By a mold housing 5, the electrodes 1, the sealing discs 11 and the intermediate walls 12 are held, with known means for sealing the compressor chambers 4 and the non-positive connection of the mold housing 5 mounted elements 1, 11 and 12 are provided, but not shown for reasons of clarity are. The means for sealing can be, for example, sealing rings between the sealing disks 11 and the intermediate walls 12 or electrodes 1. The means for non-positive connection, for example, continuous clamping screws parallel to the longitudinal axis 3 of the current limiting device 10 and 20. The two outer compressor chambers 4 are each bounded laterally by one of the electrodes 1 and by an intermediate wall 12. The inner compressor chambers 4 are each bounded laterally by two intermediate walls 12. The generally multi-part mold housing 5 and the sealing washers 11 are pressure-resistant first and second insulating body. All compressor chambers 4 are partially filled with a liquid metal 7, for example a GaInSn alloy. Above the liquid metal 7 is vacuum or inert gas, for example nitrogen or argon. The intermediate walls 12 are provided below the liquid level 9 with connecting channels 8. The connecting channels 8 are also filled with liquid metal 7, so that there is a continuous electrically conductive connection between the electrodes 1. The intermediate walls 12 are made of a dimensionally stable material, such as ceramic.

According to FIG. 1, the intermediate walls 12 of the current-limiting device 10 are provided with controllable means in the form of gas channels 13 reaching from the edge region to the connecting channels 12. Two of the four gas ducts 13 extend with pneumatic control terminals 14 through the mold housing 5 to the outside, the two other channels 13 blind ends on the mold housing 5. About the control terminals 14 are controlled small gas shocks introduced into the corresponding connection channels 8, so that by the constriction of the Current paths in these connection channels targeted a current limiting operation is triggered. Depending on requirements, more or fewer gas channels 13 may be provided with control connections 14 leading to the outside or fewer intermediate walls 12 with gas channels 13.

According to FIG. 2, 20 controllable means in the form of ultrasonic probes 23 are embedded in the intermediate walls 12 of the current-limiting device, which are connected to their Sound energy radiating end 25 to reach the connecting channels 8. The ultrasonic probes 23 extend with their other ends through the mold housing 5 and are provided there with electrical control terminals 24. Via the control terminals 24 controlled electrical energy pulses corresponding frequency can be supplied, leading to the formation of gas bubbles in the connecting channels 8 at the ends 25, so that targeted by the narrowing of the current path in the connecting channels 8, a current limiting operation is triggered. As required, fewer ultrasonic probes 23 in the current limiting case to be triggered can be supplied with electrical energy surges or fewer intermediate walls 12 can be equipped with ultrasonic probes 23.

The control terminals 14 and 24 of the current limiting device 10 and 20 shown in FIG. 1 and 2 are to be connected to control devices, which preferably evaluate the current through the current limiting device 10 and 20 respectively. This may be a multi-pole, equipped with an electronic release circuit breaker, in particular a circuit breaker, which is connected with at least one of its main current paths in series with a current limiting device 10 and 20 respectively. The circuit breaker has in addition to current detecting means also still evaluating means as part of the electronic shutter. 1, the current sensing means are to be connected to the control ports 14 of the gas passages 13 via a pneumatic means for providing gas shocks (e.g., as shown in FIGs. 3 or 4). The gas used is preferably protective gas, for example nitrogen, argon or sulfur hexafluoride. When using the current-limiting device 20 according to Fig. 2, the current-detecting means are to be connected to those control terminals 24 (for example according to Fig. 6) via a per se known electrical means for providing the energy for the ultrasound probes 23.

In FIGS. 3 and 4, two current limiting systems with current limiting devices 10 according to FIG. 1 are shown by way of example. Each current phase of a three-pole system part is equipped with a current limiting device 10. The current limiting devices 10 are simplified compared to FIG. 1 only shown with one intermediate wall 12 and two compressor chambers 4.

Referring to FIG. 3, a current evaluating controller 31 is connected to a gas impact generator 32. The control device 31 outputs when exceeding a preset Limit value for the current to be monitored from an electrical control signal to the gas shock generator 32 from which then emits a small gas burst via the pneumatic lines 33 to the control terminals 14 of the gas channels 13 of the current limiting devices 10. The gas bubbles thereby injected into the connecting channels 8 then trigger the current limiting operation in the current limiting devices 10. The current-detecting control device 31 is preferably - but not necessarily - part of the electronic release of a circuit-breaker connected in series with the current-limiting devices 10. The gas impact generator 31 may be formed, for example, as a pyrotechnic gas generator or as a fast-acting cylinder-piston device. The gas impact generator 31 may be directly connected to or disconnected from the current limiting devices 10.

According to FIG. 4, a current-evaluating control device 31 is connected to the control input of an electrically controllable valve device 34. The valve device 34 is connected on one side with a pneumatic storage or supply device 35 and on the other side via the pneumatic lines 33 to the control terminals 14 of the gas channels 13 of the current limiting devices 10. The storage or supply device 35 may be, for example, a so-called air chamber or a customary supply line for pressurized gas. The valve device 34 should react quickly to signals supplied by the control device 31. The control device 31 outputs when exceeding a preset limit for the current to be monitored from an electrical control signal to the valve device 34, which then briefly the way for a gas shock from the storage or supply device 35 via the pneumatic lines 33 to the control terminals 14 of the gas ducts 13th the current limiting devices 10 releases. The gas bubbles thereby injected into the connecting channels 8 then trigger the current limiting operation in the current limiting devices 10. The current-detecting control device 31 is preferably - but not necessarily - part of the electronic release of a circuit-breaker connected in series with the current-limiting devices 10. The valve device 34 and / or the storage or supply device 35 may be connected directly to the current limiting devices 10 or separated from them.

Referring to Figure 5, a possible embodiment for a gas blast generator 32 for use in the system of Figure 3 is shown. The gas impact generator 32 is as executed according to the known eddy current principle cylinder-piston device. In a cylinder 41 acting as a housing 41 acting as a piston pressure plate 42 light material is performed. The pressure plate 42 is provided with a short-circuiting ring 43 made of aluminum, which slides around a stationary ferrite core 44 of high permeability. When a control signal from the current-evaluating control device 31 is applied, an energy burst, preferably high frequency, is supplied via the coil connections 45 to an electromagnetic coil 46 via an electrical energy store, whereupon, under the electrodynamic interaction between coil 46 and ferrite core 44 on the one hand and short-circuit ring 42 on the other hand, the short-circuit ring 43 is abruptly thrown in the direction of the arrow 47 with the pressure plate 42, whereupon a gas shock is discharged into the pneumatic line.

FIG. 6 shows, by way of example, a system for limiting the current with current-limiting devices 20 according to FIG. 2. Each current phase of a three-pole system part is equipped with a current-limiting device 20. The current limiting devices 20 are simplified compared to FIG. 2 only shown with one intermediate wall 12 and two compressor chambers 4. A current-evaluating controller 31 is connected to an electric frequency generator 36. The control device 31 outputs when exceeding a preset limit for the current to be monitored from an electrical control signal to the frequency generator 36, which then emits an AC energy of suitable frequency via the electrical lines 37 to the control terminals 24 of the ultrasonic probes 23 of the current limiting devices 20. The gas bubbles generated thereby in the connecting channels 8 then trigger the current limiting operation in the current limiting devices 20. The current-detecting control device 31 is preferably - but not necessarily - part of the electronic release of a circuit-breaker connected in series with the current-limiting devices 20. The frequency generator 36 may be connected directly to the current limiting devices 20 or separated from them.

Claims (15)

1. Current limiting system with at least one self-recovering current limiting device (10; 20) comprising solid-metal electrodes (1) for connection to an electric circuit to be protected and successive compressor chambers (4), partially filled with liquid metal (7), located between the electrodes (1), with the chambers being formed by pressure-proof insulating bodies (5, 11) and at least one insulating partition (12) held by the latter with at least one connecting channel (8), characterised in that at least one controllable medium (13; 23) in active contact with a control device (31) reaches into the current path formed by the liquid metal (7) for the intermittent occurrence of gas and the said medium (13; 23) ends at least in the immediate vicinity of a connecting channel (8).
2. System in accordance with claim 1, characterised in that the said medium is designed as a gas channel (13) or gas line.
3. System in accordance with claim 1, characterised in that the said medium is designed as an ultrasonic probe (23).
4. System in accordance with one of the foregoing claims, characterised in that the said medium (13; 23) runs within a partition (12).
5. System in accordance with one of the foregoing claims, characterised in that the said medium (13; 23) is at least indirectly connected with a current-evaluating control device (31).
6. System in accordance with claim 2, characterised in that a current-evaluating control device (31) is connected via a gas-surge generator (32) with at least one gas channel (13) or at least one gas line.
7. System in accordance with claim 6, characterised in that a pyrotechnic gas generator is provided as gas-surge generator (32).
8. System in accordance with claim 6, characterised in that a cylinder-piston device is provided as gas-surge generator (32).
9. System in accordance with the foregoing claim, characterised in that the piston (42) is connected to a short-circuit ring (43) of a driving device operating on the eddy-current principle.
10. System in accordance with claim 2, characterised in that a compressed-gas storage or supply device (35) is connected to at least one gas channel (13) or at least one gas line via a valve (34) which can be controlled from a current-evaluating control device (31).
11. System in accordance with one of claims 6 to 10, characterised in that a protective gas such as argon, nitrogen or sulphur hexafluoride is used.
12. System in accordance with claim 3, characterised in that a current-evaluating control device (31) is effectively connected with at least one ultrasonic probe (23).
13. System in accordance with the foregoing claim, characterised in that the current-evaluating control device (31) is connected to the ultrasonic probe (23) via a frequency generator (36).
14. System in accordance with one of claims 5 to 13, characterised in that the current-evaluating control device (31) is a constituent part of the electronic trigger of a protective switch.
15. System in accordance with the foregoing claim, characterised in that at least in one current phase a current limiting device (10; 20) is connected in series with the protective switch.

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