Determining a state of a switching unit

Abstract

Method for detecting the state of a switching unit, the switching unit comprising an element movable between a first position and a second position.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for detecting the state of a switching unit.

[0002] The present invention also relates to a switching unit implementing such a method. BACKGROUND

[0003] A line supplying an electrical load generally comprises at least one switching unit. The switching unit comprises a mechanism for actuating a pair of contacts, said contacts being movable relative to each other to open or, if necessary, to make the current flow.

[0004] The failure of the actuation mechanism of a switching unit can have serious consequences, for example by the appearance of an unwanted electric arc during a bad mutual displacement between the contacts.

[0005] In addition, in order to ensure satisfactory maintenance, it is currently necessary to regularly check the good mechanical performance and the good operation of such a switching unit.

[0006] However, despite being generally satisfactory, this maintenance can prove to be insufficient, since a problem can appear after the check has been carried out, and thus only be discovered too late at the next maintenance operation.

[0007] Furthermore, these maintenance operations require the shutdown of the operation of the switching unit, sometimes for a long time and with the cumbersome disassembly / reassembly of certain elements.

[0008] Finally, these maintenance operations make it impossible to distinguish between, on the one hand, potential critical and serious faults of the switching unit, and on the other hand, relatively less problematic faults, which are generally related to an inherent wear or gradual aging, which is inherent to the elements of the switching unit, but which still allows the switching unit to work.

[0009] It is therefore one of the objectives of the present invention to propose a simple, reliable and cost-effective method for detecting the state of a switching unit, which makes it possible to ensure a more effective maintenance and diagnosis of its operation. SUMMARY

[0010] The present invention improves this situation.

[0011] A method is proposed for detecting the state of a switching unit comprising an element movable between a first position and a second position, for an iteration of index k greater than or equal to 2, the method comprising the following steps:

[0012] a) acquiring at least one measurement value, said measurement value being indicative of the displacement of the movable element (5) between the first position and the second position for the iteration of index k;

[0013] b) comparing at least the measurements acquired in the given iteration k with a first set of measurements acquired in previous iterations 1 to k-1 ;

[0014] c) generating a first alarm indicating that the switching unit is in an unusable state, based on the comparison obtained in step b) ;

[0015] d) comparing at least the measurements acquired in the given iteration k with a second set of measurements acquired in previous iterations 1 to k-1 ; and

[0016] e) generating a second alarm indicating that the switching unit is in a degraded state, based on the comparison obtained in step d).

[0017] In this way, a diagnosis of the switching unit is obtained which is representative of the real situation of the mechanical state of the elements of the switching unit, and not only of a simulated situation.

[0018] Moreover, the present application can distinguish between an unusable state which requires emergency maintenance and a degraded state which only requires an intensified monitoring and maintenance, in order to ensure the correct operation of the switching unit.

[0019] The features listed in the following paragraphs can optionally be implemented. They can be implemented independently of each other or in combination with each other.

[0020] According to one embodiment, the first set comprises, and possibly comprises only, measurements acquired between iterations k-L and k-1, L being an integer greater than or equal to 1.

[0021] According to another embodiment, the comparison obtained in step b) is performed by applying the Chauvenet criterion.

[0022] According to another embodiment, the comparison obtained in step b) is made according to the following formula:

[0023] [Formula 1]

[0024]

[0025]

[0026]

[0027] According to another embodiment, the second set comprises, and possibly comprises only, measurements acquired between iterations N and N+M-1, N and M being integers greater than or equal to 1.

[0028] According to another embodiment, the comparison obtained in step d) is made according to the following formula:

[0029] [Formula 2]

[0030]

[0031]

[0032]

[0033] According to another embodiment, said first alarm and / or said second alarm are generated when the comparison obtained in step b) and / or step d) is greater than a threshold value.

[0034] According to another embodiment, said measurement corresponds to a rotation range between 20% and 80% of the displacement stroke of said movable element between said first position and said second position.

[0035] According to another embodiment, said measurement is equal to the duration of the displacement of said movable element between two intermediate positions located between said open position and said closed position.

[0036] According to another embodiment, the method comprises an additional step:

[0037] f) storing the iterative measurements of the index k obtained in step a).

[0038] According to another embodiment, the measurement taken corresponds to an actual state transition of the switching module between the open position and the closed position.

[0039] A switching unit implementing the method according to the application is also proposed.

[0040] According to one embodiment, the movable element is a main rotary lever. BRIEF DESCRIPTION OF DRAWINGS

[0041] Other features, details and advantages will emerge on reading the following detailed description and analyzing the attached drawings in which:

[0042] Figure 1 is a cross-sectional view of a particular example of a module of a switching unit that can implement the detection method according to the application.

[0043] Figure 2 schematically represents Figure 1 the displacement stroke of the movable element of the switching unit of

[0044] Figure 3 is a schematic view of an embodiment of the detection method according to the application.

[0045] Figure 4Arepresentations of several acquisitions of a measure of the time taken for the movable element to cover between 25% and 75% of its displacement stroke when the switching module is transitioning from the closed position to the open position.

[0046] Figure 4B representations of a fraction making it possible to compare Figure 4A each of the measures and a first set comprising the 50 previous measures.

[0047] Figure 4C representations of a ratio making it possible to compare Figure 4A each of the measures and a second set comprising the 50 first measures.

[0048] Figure 5A representations of several acquisitions of a measure of the time taken for the movable element to cover between 25% and 75% of its displacement stroke when the switching module is transitioning from the open position to the closed position.

[0049] Figure 5B representations of a fraction making it possible to compare Figure 5A each of the measures and a first set comprising the 50 previous measures.

[0050] Figure 5C representations of a ratio making it possible to compare Figure 5A each of the measures and a second set comprising the 50 measures acquisitions. DETAILED DESCRIPTION

[0051] The figures and the description contain, for the most part, elements having some characteristics. They will therefore be able to be used not only to better understand the present disclosure, but also to contribute to its definition, where appropriate.

[0052] Switching unit

[0053] Figure 1 A switching module 1 of a switching unit according to a particular embodiment of the invention is shown, as is the document FR 2 807 204.

[0054] Although described in the context of a particular switching unit, the invention should not be limited in this respect. In particular, any other switching unit architecture can be envisaged. The switching unit can be chosen from among switches, circuit breakers, contactors, fuse switches and automatic reclosers.

[0055] The present application is more particularly applicable to medium- and / or high-voltage switch units. In the present document, the terms "medium-voltage" and "high-voltage" are used in their commonly accepted meaning, i.e. the term "medium-voltage" designates a voltage greater than 1000 volts in alternating current and greater than 1500 volts in direct current, but not exceeding 52000 volts in alternating current and 75000 volts in direct current, while the term "high-voltage" designates a voltage strictly greater than 52000 volts in alternating current and strictly greater than 75000 volts in direct current.

[0056] As illustrated in a non-limiting manner by Figure 1 The switch unit comprises a drive mechanism (not shown) and a switch module 1. The drive mechanism can be of any known type, in particular comprising a pole shaft 7. For example, it can be a mechanism of the type described in documents EP 0222645, EP 0789380 or EP 1347479, provided with a closing subassembly comprising a closing spring and an opening subassembly comprising an opening spring.

[0057] With reference to Figure 1 , the switch module 1 also generally comprises a vacuum interrupter 2 forming an enclosure that surrounds a fixed contact 3 and a movable contact 4.

[0058] The movable contact 4 is configured to be displaced with respect to the fixed contact so that the switch module 1 can alternately be in an open position, in which the contacts 3, 4 are far from each other, and in a closed position, in which the contacts 3, 4 are in contact with each other.

[0059] Outside the vacuum interrupter 2, the movable contact 4 is connected to the lever 5 by means of an insulating arm 6.

[0060] In operation, when the contacts 3, 4 are in the open position, the closing spring drives the pole shaft 7 in the counterclockwise direction. As Figure 1 illustrated, this movement is transmitted in particular to the lever 5 by means of the connecting rod 8, which pivots in the clockwise direction and compresses the spring 9. The closing force is then transmitted to the movable contact 4 by means of the spring 9.

[0061] When the contacts 3, 4 are in the closed position, the opening spring drives the pole shaft 7 in the clockwise direction. As Figure 1 illustrated, this movement is transmitted in particular to the lever 5 by means of the connecting rod 8, which pivots in the counterclockwise direction, driving the movable contact 4 to the open position. The opening of the electrical current flowing through the fixed contact 3 and the movable contact 4 is thus achieved.

[0062] This kinematic chain thus makes it possible to define a plurality of geometric axes of rotation, allowing the pivoting movement of a plurality of movable elements of the switch unit. According to Figure 1In the embodiment shown, a first geometrical pivot axis 10 of the pole 7, a second geometrical pivot axis 11 of the rod 5, a third geometrical pivot axis 12 of the crank of the link 8 relative to the pole 7, a fourth geometrical pivot axis 13 of the link 8 relative to the rod 5, and a fifth geometrical pivot axis 14 of the insulating part 6 relative to the rod 5 are obtained.

[0063] Other geometrical pivot axes and other movable elements can also be present in the kinematic chain of the switching unit to switch between the open position and the closed position. These other geometrical axes and other movable elements are not described in detail hereinafter.

[0064] The switching unit thus comprises a plurality of movable elements that pivot about geometrical pivot axes in its operation.

[0065] The present invention relates to a method for detecting the operating state of a switching unit based on the time of displacement of one or more of these movable elements.

[0066] Detection method

[0067] The method aims to detect the state of the switching unit based on time measurements taken with respect to the movable elements of the switching unit. It is thus possible to know the mechanical performance of the switching unit and to draw therefrom a diagnosis regarding its operation.

[0068] The movable element can advantageously be chosen as the rod 5 as described above. However, it is possible to take measurements with respect to any other movable element of the switching unit, especially as described above.

[0069] Figure 2 The rotational displacement stroke of the movable element is shown as it passes between the closed position and the open position, advantageously continuously. In the closed position, the movable element is in a first position, corresponding to 0% of its displacement stroke. In the open position, the movable element is in a second position, corresponding to 100% of its displacement stroke. The displacement stroke can be measured in the form of a rotational angle or distance between the open position and the closed position.

[0070] Between the first position and the second position, the movable element passes through intermediate positions, for example the positions corresponding to 25%, 50% and 75% of the displacement stroke, respectively, as shown in Figure 2

[0071] The time measurements obtained according to the method advantageously correspond to the passage of the movable element between two intermediate positions. The intermediate positions can advantageously be chosen in the range of displacement stroke values between 20% and 80%, even more particularly in the range of displacement stroke values between 25% and 75%.

[0072] ​By choosing the range of these values, it is possible to eliminate any instabilities observed close to the 0% and 100% limits of the displacement stroke, which rarely represent the state of the switching unit, as they are more sensitive to various frictions, tripping modes and to the inherent rebound when the switching module is switched from the open position to the closed position or vice versa.

[0073] According to the time measurements taken, the method makes it possible to perform a statistical analysis to detect a plurality of states of the switching unit.

[0074] Advantageously, the statistical analysis is performed on relative values obtained by comparing with each other a measurement or a set of measurements taken at different times on the same switching unit. This thus makes it possible to limit the inclusion of external factors, such as temperature or mechanical vibrations, which are difficult to predict and which can otherwise influence the measurements.

[0075] The first state of the switching unit is defined as an unusable state. In this unusable state, the switching unit will no longer be able to function properly. In particular, the switching from the open position to the closed position of the switching module, or vice versa, can not be ensured at a suitable speed, or even not at all.

[0076] The unusable state is characterized by a sudden change in the mechanical properties of the movable elements of the switching unit, in particular a sudden change in the displacement time.

[0077] The unusable state can be due to a bad operation of the elements of the switching unit, in particular of the switching module or of the drive mechanism, for example due to a leak of switching fluid (oil, vacuum, etc.) or to a breakage of an element. In some cases, the detection of the unusable state leads to the prohibition of using the switching unit until it is repaired or replaced.

[0078] The second state of the switching unit is defined as a degraded state. In this degraded state, the switching unit can still work, but less efficiently than before. In particular, the switching from the open position to the closed position of the switching module, or vice versa, can be performed at a less suitable speed.

[0079] The degraded state is characterized by a gradual change in the mechanical properties of the movable elements of the switching unit over time, in particular a gradual change in the displacement time over time.

[0080] The degraded state can be due to wear or aging of the elements of the switching unit, in particular of the switching module or of the drive mechanism, for example an increase in the softness of the springs of the actuation mechanism, an increase in the mechanical friction of the kinematic chain of the various movable elements of the switching unit, or an increase in the resistance on the stem of the switching unit. The detection of the degraded state makes it possible to intervene on the switching unit as soon as possible, so as to avoid a serious and potentially critical failure later on.

[0081] The method can detect other states of the switching unit, not described hereinafter.

[0082] In the following, with reference to Figure 3 The steps of the detection method according to the application are described. The method is repeated in several successive iterations. Each iteration corresponds to a transition of the switching module between the closed position and the open position. The iterations thus correspond to the actual use of the switching unit, i.e. its operation in the power line.

[0083] More particularly, Figure 3 The iteration of the index k is described, k being an integer greater than or equal to 2.

[0084] The switching unit is first ready for operation, the switching module being generally in the closed position or in the open position.

[0085] In step 101, the switching module enters the other of the open or closed position, in particular breaking the current on the power line or generating a current on the power line.

[0086] At least one measurement indicative of the displacement of the movable element between the first position and the second position is thus obtained in step 102.

[0087] In particular, the measurement can be taken by a rotation sensor 15 schematically shown in Figure 1 , for example a mechanical, capacitive, inductive, resistive or other sensor, configured to obtain a measurement indicative of the displacement of the movable element.

[0088] The measurement can be a time or speed quantity, or any other quantity measuring the ratio of the trend to time.

[0089] In step 103, at least the iteration k measurement taken is compared to a first set E1 of measurements taken in the previous iterations 1 to k-1. As a variant, a set of measurements, in particular the set comprising the iteration k measurement, can also be compared to the first set E1.

[0090] Advantageously, the first set E1 depends on the iteration k. In particular, the first set E1 comprises or consists of measurements that vary according to the iteration k concerned.

[0091] The comparison can be performed in different ways. According to one embodiment, the first set E1 can advantageously comprise only measurements taken between iterations k-L and k-1, L being an integer greater than or equal to 1. As an example, L can be equal to 50, the first set E1 then comprising all the measurements taken in the 50 iterations preceding the iteration of index k. Obviously, other first sets are possible, comprising measurements taken instantaneously more or less distant from the iteration of index k.

[0092] According to one embodiment, the comparison with the first set E1 is performed using a score D, also called "z-score" or "standard score". Such a score D makes it possible to express the distance between the iterated measured value of the index k acquired and the average of the measured values of the first set E1 as a number of standard deviations.

[0093] More particularly, the score D implements a Chauvenet test, which makes it possible to determine whether the iterated measured value x[k] of the index k acquired can be considered as an abnormal or non-abnormal measured value with respect to the other previous measured values of the first set E1. The score D can be calculated according to the following formula:

[0094] [Formula 3]

[0095]

[0096] where:

[0097] [Formula 4]

[0098]

[0099] [Formula 5]

[0100]

[0101] In step 104, the score D calculated is compared with a first threshold S1.

[0102] If the score D is greater than the first threshold S1, an alert is generated in step 105 to warn that the switching unit is in an unusable state as described above. In practice, this means that the iterated measured value of the index k is particularly far from the measured values contained in the first set E1, such that the most recent change in the switching unit has reduced its operating performance.

[0103] If the score is less than the first threshold S1, in step 106 at least the measured value acquired in the iteration of the index k is compared with a second set E2 of measured values acquired in the previous iterations 1 to k-1. It is also possible to compare the set of measured values, in particular the set comprising the iterated measured value of the index k, with the second set E2.

[0104] According to one embodiment, the second set E2 can advantageously comprise only the measured values acquired between the iteration N and N+M-1, N and M being integers greater than or equal to 1. For example, N can be equal to 1 and M can be equal to 50, then the second set E2 comprises all the first 50 measured values acquired. Thus, the second set E2 can comprise the values tested by the manufacturer of the switching unit (also called factory exit values). Obviously, other second sets are possible for the first set E1, comprising measured values acquired more or less far from the instant of the iterated measurement of the index k.

[0105] Advantageously, the second set E2 thus comprises measurement values that are independent of the iteration k concerned. The second set E2 thus comprises, in comparison with the first set E1, measurement values taken or fixed in iterations relatively far from the iteration measurement with respect to the index k.

[0106] The comparison can be performed in different ways. According to one embodiment, the comparison with the second set E2 is performed using a ratio R. The ratio R represents the relative difference between the average of all the measurement values obtained in the M iterations preceding the iteration x[k] of the index k and the average of the measurement values of the second set E2.

[0107] More particularly, the ratio R is calculated according to the following formula:

[0108] [Formula 6]

[0109]

[0110] With

[0111] [Formula 7]

[0112]

[0113] [Formula 8]

[0114]

[0115] In step 107, the ratio R calculated is compared with a second threshold S2.

[0116] If the ratio R is greater than the second threshold S2, an alert is generated in step 108 to warn that the switching unit is in a degraded state as described above. In practice, this means that a gradual drift of the measurement values with respect to the measurement values of the second set E2 is observed, which can prove detrimental to the operation of the switching unit.

[0117] If the ratio R is less than the second threshold S2, no alert is generated.

[0118] Finally, in step 109, the iteration measurement of the index k is stored. To do this, the switching unit can comprise a memory or transmit the measurement values taken to be stored on a remote server (not shown).

[0119] The method can then be repeated for the iteration of the index k+1 when the switching unit is again ready for operation.

[0120] Experimental results

[0121] Figure 4A , Figure 4B and Figure 4C An implementation of the detection method according to the first embodiment is shown.

[0122] In Figure 4A , the measurements acquired according to this first embodiment are observed. Each measurement corresponds to the time required to cover an intermediate position between 25% and 75% of the displacement stroke of the movable element in the transition from the first position to the second position, corresponding to the transition of the switching module from the closed position to the open position.

[0123] For the switching module, the measurements represent the phase of the current. However, the results obtained from these measurements can be converted for switching modules of other phases of the current.

[0124] Abrupt disconnections, such as lines B1 and B2 in Figure Figure 4A , correspond to operations of maintenance or replacement of the element actually performed on the switching unit, thus leading to a change in the switching characteristics and therefore to a change in the subsequent measurements. These disconnections should therefore not be taken into account in the method according to the application.

[0125] In particular, after an abrupt disconnection, the measurements of the first and second sets E1, E2, which allow comparison with the subsequently acquired measurements, are reset to define new reference values.

[0126] Figure 4B represents the score D obtained according to the Chauvenet test described above, making it possible to compare Figure 4A each of the measurements and the first set E1 comprising the 50 iterations immediately preceding said measurement.

[0127] In said Figure 4B , it can be seen that some measurements (in particular measurements 14151, 15649, 15975 and 25551 ) obtain a high score D, greater than 15, even greater than 20. These measurements can therefore exceed the predetermined threshold, in particular depending on the switching unit concerned, and thus characterise an unusable state of the switching unit.

[0128] Figure 4C represents the ratio R obtained as described above, making it possible to compare Figure 4A each of the measurements and the second set E2 comprising the first 50 measurements acquired on the switching unit.

[0129] In said Figure 4C , it can be seen that some measurements obtain a ratio R less than 1 (corresponding to a displacement speed relatively faster than the second set E2) or a ratio R greater than 1 (corresponding to a displacement speed relatively slower). These measurements can therefore exceed the predetermined threshold, in particular depending on the switching unit concerned, and thus characterise a degraded state of the switching unit, related to an inappropriate closing / opening speed of the switching module.

[0130] Generally, apart from any sudden disconnections or changes, it can be seen that the ratio R has a tendency to increase over time, reflecting the gradual wear and ageing of the switching unit that can lead to a degraded state.

[0131] Figure 5A , Figure 5B and Figure 5C shows the implementation of the detection method according to the second embodiment.

[0132] In Figure 5A , the measurements acquired according to this second embodiment can be observed. Each measurement corresponds to the time taken to cover the displacement travel between 25% and 75% of the intermediate position in the transition from the second position to the first position, corresponding to the transition of the switching module from the open position to the closed position.

[0133] For the switching module, the measurements represent the phase of the current. However, the results obtained from these measurements can be converted for switching modules of other phases of the current.

[0134] In the same way as for Figure 4A , sudden disconnections, such as the lines B1'and B2' in figure Figure 5A , correspond to operations of maintenance or replacement of the element actually performed on the switching unit, thus leading to a change in the switching characteristics and therefore to a change in the subsequent measurements. These disconnections should therefore not be taken into account in the method according to the application.

[0135] Figure 5B represents the score D obtained according to the Chauvenet test described above, making it possible to compare Figure 5A the measurements and a first set E1 comprising the 50 most recent measurements immediately preceding said measurements.

[0136] In said Figure 5B , it can be seen that some acquisitions, in particular the measurements 14151 and 15975, obtain a high score D, greater than 10, even greater than 50. These measurements can therefore exceed the predetermined threshold and thus characterise an unusable state of the switching unit.

[0137] Figure 5C represents the ratio R obtained as described above, making it possible to compare Figure 5A each measurement and a second set E2 comprising the 50 most recent measurements acquired from the switching unit.

[0138] In said Figure 5CAmong them, it can be seen that some of the obtained ratios R are less than 1 (corresponding to a faster displacement speed) or ratios R greater than 1 (corresponding to a slower displacement speed). These measurements can therefore exceed the predetermined threshold and thus characterize a degraded state of the switching unit, related to an inappropriate closing / opening speed of the switching module.

[0139] Obviously, the application is not limited to the embodiments given by way of example and previously described. It encompasses the various modifications, alternative forms and other variants that the person skilled in the art can conceive within the framework of the application, and in particular all combinations of the different embodiments previously described, which can be used separately or in combination.

[0140] In particular, although the comparisons have been advantageously illustrated above by using the specific fractions D and ratios R to determine the state of the switching unit, other comparison methods can be envisaged, also implementing a ratio or a sequential-based relationship between the measurements indicative of the displacement of the movable element.

[0141] Finally, the above has only described a method for detecting two states of unavailability or degradation. However, this method can advantageously be extended to other states characterizing the operating and / or mechanical state of the switching unit.

Claims

1. A method for detecting the status of a switching unit, said switching unit comprising an element (5) movable between a first position and a second position, for iterations of index k greater than or equal to 2, said method comprising the steps of: a) acquiring at least one measurement value indicative of the displacement of the movable element (5) between the first position and the second position at iteration index k; b) comparing at least the measurement value acquired in the given iteration k with a first set (El) of measurement values acquired in the previous iterations 1 to k-1, said first set (El) comprising the measurement values acquired between iterations k-L and k-1, L being an integer greater than 1; c) generating a first alarm, indicative of the switching unit being in an unusable state, if the comparison result obtained in step b) is greater than a first threshold value (SI); d) comparing at least the measurement value acquired in the given iteration k with a second set (E2) of measurement values acquired in the previous iterations 1 to k-1, the second set (E2) comprising the measurement values acquired between iterations N and N+M-1, N and M being integers greater than 1; and e) generating a second alarm, indicative of the switching unit being in a degraded state, if the comparison result obtained in step d) is greater than a second threshold value (S2), wherein the comparison in step b) is performed by applying the Chauvenet criterion, wherein the comparison in step b) is performed on the basis of a score D according to the following formula: ， wherein: wherein, in step d), the comparison is performed based on a ratio R according to the following formula: wherein: ， 。 2. The method of claim 1, wherein, said measurement values corresponding to a rotation range between 20% and 80% of the displacement travel of the movable element (5) between the first position and the second position.

3. The method of claim 1, wherein, said measurement values being equal to the duration of the displacement of the movable element (5) between two intermediate positions located between the open position and the closed position.

4. The method according to claim 1, comprising the additional step of: f) storing the iteration measurement values of index k obtained in step a).

5. The method of claim 1, wherein, said acquired measurement values corresponding to the actual state transition of the switching module between the open position and the closed position.

6. A switching unit implementing the method according to any one of the preceding claims.

7. The switching unit of claim 6, wherein, said movable element (5) being a main rotary lever.

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