EP1678729B1 - Device for detecting contact wear in switching appliances - Google Patents

Abstract

The invention concerns a device for detecting wear of switching contacts (K1,K1') in an electric switch appliance (S), the wear of the contacts being caused at least at a pair of switching contacts appliances (K1,K1') which open and close in the switching appliance (S). The inventive device comprises a lightwave guide (LWL) and a detector (D), a light exiting from at least one light source (Q) being capable of being injected into the lightwave guide (LWL) and guided by said lightwave guide (LWL) up to the detector (D). The lightwave guide (LWL) is arranged relative to the pair(s) of switching contacts (K1,K1'), such that the intensity of the light injected in the lightwave guide (LWL), which is measured by the detector, decreases in the switching appliance (S) as the number of wear particles of contacts generated by the wear of the contacts increases.

Description

The present invention relates to a device for detecting contact erosion in switching devices. In particular, the present invention relates to a device for detecting contact erosion on the switching contacts in an electrical switching device according to the preamble of claim 1.

In the electrical switching device, the opening and closing switching contacts for switching currents cause switching arcs between the switching contacts. These switching arcs lead to an increasing contact erosion at the switching contacts and thus to a wear of the switching contacts. Since this wear affects the switching behavior of the switching device, the contact erosion of the switching contacts must be monitored.

From the EP 1 022 904 A1 It is known to use a camera for visual monitoring of the wear of the switching contacts. Another from the EP 1 022 904 A1 Known device for monitoring the wear is the numerical monitoring using a switching counter or the numerical monitoring based on the summation of the cut-off currents.

From the DE 101 09 952 A1 An arrangement is known with which an arc fault can be detected in an electrical switchgear by means of an optical waveguide. For this purpose, the light emanating from a fault arc occurring is coupled radially into the optical waveguide and guided to a detector. Subsequently, it is detected in an interference light detection circuit on the basis of the injected and detected light, whether an arc fault has occurred.

In the document DE 19 727 986 Also disclosed is a device for detecting contact erosion on sound contacts.

Object of the present invention is to provide a further device for monitoring the wear of switching contacts in electrical switching devices.

This object is achieved by the device having the features of claim 1, wherein the contact erosion is effected on at least one opening and closing switching contact pair in the switching device, and the device comprises at least one optical waveguide and at least one detector, wherein light emitted from at least one light source the at least one optical waveguide can be coupled in and can be guided by the optical waveguide to the at least one detector and the at least one optical waveguide is arranged with respect to the at least one switching contact pair so that an intensity of the light coupled into the optical waveguide of an ascending number measured by the at least one detector decreases from the contact erosion generated contact erosion particles in the electrical switching device.

With increasing number of switching operations and thus with increasing number of recurring switching arcs occurs as a result of the contact burnup caused thereby at the switch contacts to an increased accumulation of Kontaktabbrandpartikeln, and thus to an increasing degree of contamination in the electrical switching device. According to the basic principle of the present invention, this increasing degree of contamination is now used as a measure of the assessment of the contact erosion and thus for the monitoring of the wear of the switching contacts of the electrical switching device. According to the present invention, this degree of contamination is determined with the aid of the at least one optical waveguide and the at least one detector. That is, one or more optical waveguides are arranged with respect to the at least one switching contact to be monitored such that the light emanating from a light source and entering one of the optical waveguides with increasing number of contact erosion particles and thus with increasing Degree of pollution is increasingly dampened. The light entering the one or more optical waveguides is guided by the optical waveguide to one or more detectors. An optical waveguide can lead the incoming light exactly to one but also to several detectors. On the other hand, the light entering into a plurality of optical waveguides, which are jointly assigned to the at least one switching contact, can also be led to only one detector. In all these cases, the intensity of the light coupled in at least one optical waveguide is measured by the at least one detector. Based on the measured intensity of the light entering the optical waveguide in the desired state of the switching device, that is, for example, in a new switching device, then by repeatedly measuring and evaluating the intensity of the light entering the at least one optical waveguide, the contact erosion and thus the wear of at least one assigned switching contact to be monitored. The device according to the invention thus permits contactless monitoring with opto-electronic means. In addition, the device according to the invention allows the determination of the contact erosion without the need for the switching device itself to be removed from its actual operating location. The necessary calibration of the measured intensity on the state of the switching contacts and thus on the degree of wear is determined depending on the particular design of the switching device and can be based for example on empirically determined values.

Preferably, the, caused by the opening and closing switching contacts, arc itself is used as a light source for the device according to the invention. In order to use different light intensities of different switching arcs, a mathematical standardization is to be brought about in a suitable manner. In particular, this standardization should also include possible changes in the light intensity of the arc, with increasing contact erosion can occur. By means of such normalization, it can then be assumed during the evaluation that the intensity of the light emanating from the arc is almost constant. Thus, based on the measurement of the intensity of the outgoing from the arc, increasingly damped by the Kontaktabbrandpartikeln and coupled into the at least one optical waveguide light on the contact erosion closed and thus the wear of the switch contacts are monitored.

In a further embodiment, in particular a light-emitting diode is provided as a light source, which forms a light barrier together with the at least one optical waveguide. In this case, the light barrier must be arranged in relation to the at least one switching contact pair such that the light emitted by the light emitting diode and coupled into the at least one optical waveguide is attenuated by the contact erosion particles located in the space between the light emitting diode and the optical waveguide. If commercial photocells, which comprise precisely one optical waveguide and one light-emitting diode, are preferably used, the wear can be monitored with the simplest means.

In a further embodiment, a further LichtweLlenleiter is provided as a light source. Of course, since an optical waveguide itself is a passive element, light from a light source, such as a light emitting diode, is first to be coupled into this further light waveguide. If the light is guided by this further optical waveguide so that the light exits at one of its end faces, this end face can be regarded as a light source for the device according to the invention and form a light barrier together with the first optical waveguide. This makes it possible to arrange all necessary for the present invention electrical components, such as bulbs or detectors outside the actual switching device.

In an alternative embodiment, the light is guided by the further optical waveguide acting as a light source so that it emerges radially over its length. Due to this constant light emission, the intensity remaining in the optical waveguide will continue to decrease with increasing length, that is, with increasing distance from the illuminant. As a result, as the distance from the light source increases, so does the intensity of the light that emerges. By a suitable arrangement of the further optical waveguide with respect to the switching contact pair to be monitored, it is now possible to introduce a local weighting in the detection of the contact erosion.

In a further embodiment, a plate is provided between the light source and the at least one optical waveguide, which has a defined transmittance for the light emitted by the light source, and which is arranged with respect to the switch contacts so that contact erosion particles can attach to the plate. With increasing contact erosion, more and more contact erosion particles will then accumulate on the plate and thus the degree of transmittance for the light passing through the plate will continue to decrease. On the basis of the decrease in the intensity of the light coupled into the optical waveguide, it is then possible in turn to deduce the degree of contact erosion and thus the wear of the switching contacts.

The device according to the invention allows at least one switching contact pair to be monitored, that is to say one but also a plurality of switching contact pairs are monitored by a common arrangement of at least one optical waveguide and at least one detector. This common arrangement then allows a common statement on the contact wear on this at least one pair of switching contact. In a further embodiment, at least one optical waveguide can be provided in particular for each switching contact pair of a multi-pole switching device. Thus, the degree of burnup and thus the wear of the individual switching contact pairs are monitored separately.

If a signal corresponding to the light intensity measured by at least one detector is transmitted to a triggering unit for the electrical switching device, then the switching device can be controlled by this triggering unit. If the measured light intensity falls below a certain value as a result of an ever increasing number of contact erosion particles, the tripping unit will recognize that a critical degree of wear has been reached and prevent further switching of the electrical switching device.

If the intensity measured by the at least one detector is transmitted by suitable means, for example wirelessly, for further evaluation, then the evaluation can also be evaluated at a location further away from the switching device and thus the switching device can be monitored. In particular, the state of the switching contacts can then be remotely reported during operation of the circuit breaker. Wear of the switching contact can thus be detected early, which then preventive maintenance is possible.

Preferably, the device according to the invention is used for detecting contact erosion in low-voltage circuit breakers or contactors.

Fig.1

schematisch eine erste Ausführungsform mit einer Leuchtdiode als Lichtquelle,

Fig.2

eine zweite Ausführungsform mit einem weiteren Lichtwellenleiter als Lichtquelle,

Fig.3

schematisch eine dritte Ausführungsform mit dem Lichtbogen als Lichtquelle,

Fig.4

schematisch eine vierte Ausführungsform mit einer Platte zwischen Lichtquelle und Lichtwellenleiter,

Fig.5

eine Lichtwellenleiteranordnung für mehrere Schaltkontaktpaare,

Fig.6

eine Anordnung von drei Lichtwellenleitern für drei Schaltkontaktpaare.

The invention and advantageous embodiments thereof are described in more detail below with reference to the following figures. Show it:

Fig.1

schematically a first embodiment with a light emitting diode as a light source,

Fig.2

a second embodiment with a further optical waveguide as the light source,

Figure 3

schematically a third embodiment with the arc as a light source,

Figure 4

schematically a fourth embodiment with a plate between the light source and optical fiber,

Figure 5

an optical waveguide arrangement for a plurality of switching contact pairs,

Figure 6

an arrangement of three optical fibers for three switching contact pairs.

The exemplary embodiments shown in FIGS. 1 to 4 always have just one light source Q, an optical waveguide LWL for coupling in the light emanating from the light source, and a detector D for a switching contact pair for simplifying the description of the present invention. In more complex arrangements, instead of the one optical waveguide LWL shown at least one optical waveguide and instead of the one detector D at least one detector for the device according to the invention may be provided.

FIGS. 1-4 show various embodiments of an electrical switching device S. The switching device S has a first K1 and a second K1 'switching contact. One of the switching contacts is movable in a suitable manner, so that with appropriate control, the contacts can be moved towards or away from each other. With the existing of the Schaltkantakten K1 and K1 `switching contact pair can then switch corresponding switching currents. When opening and closing the switching contact pair K1, K1 'occurs when switching high currents, as they are usually switched in low-voltage circuit breakers or contactors, to an arc between the switch contacts K1 and K1'. This arc causes an increasing burnup of the switching contacts K1 and K1 'with increasing number of switching operations and thus an increasing wear of the switching device S. If the burnup is too high, the switching device S can no longer safely switch the currents to be switched and must be replaced.

Various methods and devices for detecting wear are already known. Based on some embodiments, the device according to the invention for monitoring, that is, for detecting contact erosion will now be described. For this purpose, as shown in Figure 1, an optical fiber LWL and a light source Q are provided. Preferably, this light source Q is a light-emitting diode, which forms a commercially available light barrier LS together with the optical waveguide LWL. The light emanating from the light source Q will have a certain intensity, depending on the type of light source and its activation. According to the arrangement of light source Q and optical fiber LWL a certain part of the light is coupled into the optical waveguide LWL and guided by this to a detector D. In the case of a new switching device S, the intensity, measured by the detector D, of the light coupled into the optical waveguide LWL has a defined amount, that is to say a nominal value. With increasing contact erosion at the switching contacts K1 and K1 ', the number of contact erosion particles in the housing G of the electrical switching device S will increase. If these contact erosion particles now reach the region between the light source Q and the optical waveguide LWL, the light emanating from the light source Q and entering the optical waveguide LWL is attenuated by this contact erosion particle. This means that the more contact erosion particles within the housing G and thus in the region between the light source Q and the optical waveguide LWL are present, the lower will be the intensity of the light coupled into the optical waveguide LWL as measured by the detector D. Once a relationship between contact erosion and the number of located in the switching device S Kontaktabbrandpartikel once found, can be determined by the number of contact erosion caused by the decrease in the intensity of in the light waveguide coupled light the wear of the switching contacts K1 and K1 'and thus the wear of the switching device S are monitored.

Figure 2 shows in more detail, another embodiment of the electrical switching device S with the two switching contacts K1 and K1 '. Due to the shape of the switching contacts K1 and K1 'shown here, it will be in the marked area in particular to an increased contact erosion and thus to increased pollution. If this locally stronger contamination is to be taken into account when detecting the contact erosion, a development of the device according to the invention is advantageous. In the embodiment shown in FIG. 2, therefore, the device according to the invention comprises an optical waveguide LWL for coupling in light and a further optical waveguide LWLQ, which is designed as a light source. In the embodiment shown here, light from a luminous means Q at both ends of the further optical waveguide LWLQ is coupled into this further optical waveguide acting as a light source. The further optical waveguide LWLQ is designed so that the light guided therein radially emerges over its length. As a result of this permanent light emission, the intensity of the light emerging radially from the further optical waveguide LWLQ will continue to decrease with increasing distance from the luminous means Q. This means that, in the arrangement shown in FIG. 2, light with the least intensity will emerge from the further optical waveguide LWLQ in the marked area. Since this region encompassed by a dashed line is also the region with the greatest contamination, the light emerging radially from the further optical waveguide LWLQ with reduced intensity is also attenuated even more than in other regions. Thus, the light entering the optical waveguide LWL arranged, for example, parallel to the further optical waveguide LWLQ, will always have a lower intensity in the marked region than the light which is coupled into the optical waveguide LWL in the other regions becomes. As for that in the. Optical fiber LWL coupled and guided to the detector D light the intensity is determined over all spatially coupled light components, the light entering from the marked area with a different weighting in the determination of the intensity and thus in the assessment of Kontaktabbrandes received as the light in other areas is coupled. In addition to the arrangement of optical waveguide LWL and further optical waveguide LWLQ shown in Figure 2, many other arrangements are conceivable and included in the invention. Thus, an arrangement is conceivable in which the optical waveguides LWL and LWLQ are not meandering, but are formed only as a simple loop. Furthermore, it is conceivable that both optical waveguides LWL and LWLQ are arranged so that the switching contact pair K1, K1 'is located between the optical waveguide LWL and the further optical waveguide LWLQ. Furthermore, it is also readily possible, as described above, to provide a plurality of optical waveguides or detectors for monitoring one switching contact pair instead of one optical waveguide LWL and one detector D in this embodiment as well.

In the third embodiment, shown schematically in Figure 3, the arc generated by the opening and closing switch contacts K1 and K1 'itself is the light source Q. Then additionally only an optical fiber LWL and a detector D are necessary to use the inventive device To detect contact erosion, and thus to monitor the wear of the switching device S. With increasing erosion, the number of contact erosion particles generated by the burnup will increase between the arc Q and the optical waveguide LWL and thus the light emanating from the arc Q will be increasingly dampened until it enters the optical waveguide. Thus, in turn, the wear of the switching device can be monitored indirectly on the basis of the intensity of the light coupled into the optical waveguide LWL and guided to the detector D light. A possibly during the operation, that is, with increasing number of switching operations of the switching device, changing intensity of the outgoing light from the arc must be determined empirically and taken into account in the monitoring in a corresponding normalization.

FIG. 4 schematically shows a fourth embodiment, in which again the arc is the light source Q. Here, a plate P is additionally provided between arc Q and optical fiber LWL, at which the contact erosion particles can accumulate. This means that with increasing erosion, more and more contact erosion particles will accumulate on the plate P, whereby the transmittance for the light transmitted from the arc to the optical waveguide becomes ever smaller, that is, increasingly attenuated. Thus, in turn, the wear of the switching device can be monitored indirectly on the basis of the intensity of the light coupled into the optical waveguide LWL and guided to the detector D light. The plate P shown in FIG. 4 may also be readily used in combination with one of the embodiments shown in FIG. 1 or 2. Also, the plate P itself could be a window in the housing, wherein the light emitted from the arc light is transmitted via the plate P to an arranged outside the housing optical fiber LWL and coupled into this. In addition to the previously described embodiments are still a variety of other embodiments or combinations of devices according to the invention conceivable as long as the basic principle of the present invention is satisfied, namely that with the help of Kontaktabbrandpartikel indirectly the contact erosion of the switching contacts K1 and K1 'and thus the wear of the electrical switching device S is monitored.

So far, the present invention has only been described in relation to an electrical switching device S with a switching contact pair K1, K1 '. FIG. 5 shows, by way of example, a possible arrangement of the optical waveguide LWL for a multi-pole switching device with three switching contact pairs. The optical waveguide here has three loops, each of the loops being associated with a switching contact pair of the switching device. Not shown here are the light sources. However, as explained in the previously described embodiments, these can be either the arc itself or an additional light source, in particular a light-emitting diode or another optical waveguide. Thus, for each of the switching contact pairs, the intensity of the emanating from the respective light source Q and coupled into the optical waveguide LWL and forwarded by this light from the detector D is measured and then transmitted to a trip unit A. This trip unit will control the electrical switching device depending on the measured intensity of the light. If the measured light intensity falls below a certain value only for one of the switching contact pairs as a result of an ever increasing number of contact erosion particles, the tripping unit A will recognize that a critical degree of wear has been achieved at least for this switching contact pair and a further switching of all switching contact pairs of the multi-pole electrical switching device S. prevention. If the switching contact pairs of a multi-pole switching device are to be monitored separately, a separate optical waveguide LWL1, LWL2 and LWL 3 as well as an associated detector D1, D2 and D3 can be provided for each switching contact pair as shown in FIG. If the individual switching contact pairs are interconnected with a time offset and this time information is available to a detector, then the three detectors D1, D2 and D3 can be replaced by a single detector D, as indicated in FIG. 6 by a dashed line. The intensities measured by the detectors D1, D2 and D3 or the detector D can then be transmitted again to the tripping unit A, and this can then react accordingly, as already described above.

Claims (11)

1. Apparatus for detection of contact erosion on switching contacts (K1, K1') in an electrical switching device (S), with the contact erosion occurring on at least one opening and closing switching contact pair (K1, K1') in the switching device (S), having a least one optical waveguide (LWL) and at least one detector (D), in which case light which emerges from at least one light source (Q) can be injected into the at least one optical waveguide (LWL), and can be passed from the optical waveguide (LWL) to the at least one detector (D),
   characterized in that
   the at least one optical waveguide (LWL) is arranged with respect to the at least one switching contact pair (K1, K1') such that the intensity, as measured by the at least one detector (D), of the light which is injected into the at least one optical waveguide (LWL) decreases with an increasing number of contact erosion particles, produced by contact erosion, in the electrical switching device (S).
2. Apparatus according to Claim 1,
   characterized in that
   the light source (Q) is the arc produced by the opening and closing switching contact pair (K1, K1').
3. Apparatus according to Claim 1 or 2,
   characterized in that
   the light source (Q) is at least one light-emitting diode, which, together with the at least one optical waveguide (LWL), forms a light barrier (LS).
4. Apparatus according to Claim 1 or 2,
   characterized in that
   the at least one light source (Q) is a further optical waveguide (LWLQ).
5. Apparatus according to Claim 4,
   characterized in that
   the light from the further optical waveguide (LWLQ) emerges at one of its end faces and, together with the at least one optical waveguide (LWL), this end face forms a light barrier (LS) .
6. Apparatus according to Claim 4,
   characterized in that
   the light from the further optical waveguide (LWLQ) emerges radially over its length.
7. Apparatus according to one of Claims 1 to 6,
   characterized in that
   a plate (P) is arranged between the light source (Q) and the at least one optical waveguide (LWL), which plate (P) has a radiant transmittance for the light emerging from the light source (Q) and is arranged with respect to the at least one switching contact pair (K1, K1') such that contact erosion particles accumulate on the plate (P), with the radiant transmittance decreasing as the number of contact erosion particles increases.
8. Apparatus according to one of the preceding Claims 1 to 7,
   characterized in that
   one switching contact pair in a multipole switching device (S) has an associated optical waveguide (LWL1, LWL2, LWL3), with the optical waveguide (LWL1, LWL2, LWL3) being arranged with respect to the associated switching contact pair such that the intensity, as measured by the detector (D), of the light injected via the optical waveguide (LWL1, LWL2, LWL3) is a measure of the contact erosion of the associated switching contact pair.
9. Apparatus according to one of Claims 1 to 8,
   characterized in that
   the detector (D) transmits a signal, which corresponds to the measured intensity, to a tripping unit (A), and this tripping unit (A) controls the switching device (S) as a function of the signal.
10. Apparatus according to one of Claims 1 to 9,
    characterized in that
    the intensity, as measured by the detector (D), is transmitted via means for communication for further evaluation.
11. Electrical switching device having an apparatus according to one of Claims 1 to 10,
    characterized in that
    the electrical switching device (S) is a low-voltage circuit breaker or a contactor.

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