Methods and devices for testing and diagnosing a circuit breaker based on dynamic contact resistance measurement
The use of a high-intensity current source and data processing for dynamic resistance measurement in circuit breakers addresses the limitations of existing methods, ensuring stable and accurate wear identification for high-voltage circuit breakers.
Patent Information
- Application Number
- FR2023006288
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-06-19
- Publication Date
- 2025-10-10
- Estimated Expiration
- 2043-06-19
AI Technical Summary
Current methods for diagnosing high-voltage circuit breakers are limited by non-reproducible and complex dynamic resistance measurements due to low current density and source impedance issues, leading to potential over- or underestimation of wear, which can result in premature or late maintenance.
A test apparatus using a high-intensity direct current source (e.g., a storage battery) to inject currents above 1000 A, combined with a voltage sensor and data processing to measure dynamic contact resistance, and a diagnostic apparatus to detect contact type changes and determine characteristic parameters, enabling reliable wear indicators.
Ensures stable and repeatable measurements, allowing accurate identification of circuit breaker wear and improving maintenance scheduling by providing reliable wear indicators.
Smart Images
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Abstract
Description
Title of the invention: Methods and devices for testing and diagnosing a circuit breaker based on a dynamic contact resistance measurement Technical field
[0001] The field of the invention is that of the diagnosis of high voltage circuit breakers (HTA and HTB) with double switching of the main contacts and the arcing contacts, such as those using a cutting gas such as sulfur hexafluoride (SF6) or an alternative gas (CO2, O2, g3, etc.). Prior art
[0002] High voltage circuit breakers are used in high voltage electrical systems, such as electricity transmission networks, power plant switchyards and industrial equipment, to transmit energy, provide fault protection and connect / disconnect electrical networks, production plants or any loads.
[0003] Because these circuit breakers are essential to maintaining safe and efficient operations on an electrical network, they are constantly checked to confirm that they are operating correctly and to detect any early signs of failure.
[0004] Currently, a comprehensive diagnosis of all the internal parts of a circuit breaker can only be obtained by visual inspection after opening the breaking chamber. This inspection is a costly operation in terms of availability of electrical works (for example: unavailability of the production plant or factory) and in terms of labor (time-consuming site).
[0005] There are methods for diagnosing parts subject to the passage of current (conduction and breaking), based mainly on a static analysis of the parameters characterizing it: studies of dead times at opening, at closing, static value of the main resistance. But these methods provide very limited information on the real state of the parts checked.
[0006] A reliable and affordable alternative is the technique of diagnostics by dynamic resistance measurement. Its principle is based on a measurement of the resistance at the terminals of the breaking chamber (thus making it possible to indirectly measure the ohmic value of all the internal contacts) of a circuit breaker during the opening and closing phases at the nominal operating speed of the circuit breaker. To do this, a direct current source injects a current into the breaking chamber of the circuit breaker when a circuit breaker operation is triggered (opening or closing). A four-wire measurement makes it possible to separately obtain the value of the injected current and the voltage across the circuit breaker terminals. From these two values, the resistance of the contacts can be determined.
[0007] The dynamic resistance measurement is then represented in the form of a curve as a function of time (or as a function of the displacement of the moving contact in the case of using an additional motion sensor). Indicators can be extracted from this curve, and their evolution can be followed over the lifetime of the circuit breaker. These indicators are obtained by dividing the curve into different zones corresponding to the different types of contact seen by the current during its passage. This is followed by a calculation of average values, duration (or travel if the displacement is measured) and areas on each of these zones.
[0008] The devices currently available commercially for carrying out such a dynamic resistance measurement are made in line with what was previously done for static resistance measurement when the circuit breaker is in the closed position, by carrying out a low intensity current injection (maximum 100 A to 500 A) with a capacitive and generally inductive source impedance (filter).
[0009] In the case of a dynamic contact resistance measurement with such devices, variations in resistance are observed due, on the one hand, to a variation in the injected current and, on the other hand, to an overvoltage exceeding the limits of the equipment.
[0010] These phenomena are directly explainable by the nature of the current source used to inject the direct current. The characteristic of an ideal voltage source is a constant straight line with the equation V = Vo. In theory, it provides a current proportional to the connected load, but in practice, voltage sources have a certain limit due to their internal impedance. A real voltage source is therefore a decreasing straight line with the equation V = -z. i + Vo, where z is the internal impedance of the source. This internal impedance causes an interaction (dissipation in the resistive case or oscillation in the inductive or capacitive cases) on the injected current or the measured voltage.
[0011] In the presence of capacitive source impedance, the observed current variation is the result of the voltage variation during switching of the contacts. Indeed, the injected current undergoes the spontaneous voltage variation according to La Switching contacts creates very sudden variations in resistance. When the circuit breaker is operated, the type of contact changes (parts in contact of different nature) and therefore the voltage at the terminals of the device changes. The injected current then undergoes strong variations and becomes unstable. Oscillations are therefore observable on the current which undergoes the spontaneous variation in voltage.
[0012] If an inductive element is present in the source impedance, an overvoltage exceeding the limits of the material may occur. This overvoltage is due to the failure to maintain the flow of current created by spontaneous breaks in its closed current loop during injection. Indeed, a constant flow of current through the contact is not necessarily guaranteed over the entire movement, especially if the current is of low amplitude. A furtive opening of the current loop generates violent overvoltages greatly exceeding the source voltage. The overvoltage is generated by the energy remaining in the inductances of the circuit (filter, cable, etc.) as described by u _ jiL.
[0013] The measuring devices currently available thus present several problems, in particular a low current density which makes the measurements non-reproducible on the same type of device. In addition, understanding the signal requires sequencing of the signal, currently commonly carried out visually. In addition to requiring an expert eye, such sequencing is particularly complex, or even impossible, during dynamic measurement with low currents affected by the source impedance which generates oscillations or overvoltages during the transitions between the different types of electrical contact and towards the gaseous state. This results in a risk of over- or underestimating the wear of the circuit breaker which can lead either to a failure or to late or premature maintenance. Statement of the invention
[0014] The invention aims to improve the quality of dynamic contact resistance measurements for checking the states of the internal contacts of high-voltage circuit breakers. To this end, the invention proposes, according to a first aspect, a test apparatus, comprising: - a direct current source capable of injecting a current into a breaking chamber of the high-voltage circuit breaker during an opening or closing operation of the high-voltage circuit breaker, - a voltage sensor capable of measuring a voltage at the terminals of the high-voltage circuit breaker during the opening or closing operation of the high-voltage circuit breaker, and - a data processing unit configured to deliver, from the voltage measurement carried out by the voltage sensor and the amplitude of the current injected by the direct current source, a signal measuring the dynamic contact resistance of the high-voltage circuit breaker during the opening or closing operation of the high-voltage circuit breaker.
[0015] The direct current source is a storage battery capable of injecting a current of intensity greater than 1000 A during the opening or closing operation of said circuit breaker.
[0016] The invention also proposes, according to a second aspect, a diagnostic apparatus for a high-voltage circuit breaker comprising main contacts and arcing contacts inside an extinguishing chamber. This apparatus comprises a processor configured to: - obtain a dynamic contact resistance measurement signal from the high-voltage circuit breaker during an opening or closing operation of the high-voltage circuit breaker, said operation causing a movement of the main contacts and the arcing contacts which results in changes in contact type, - detecting changes in contact type in the measurement signal, said changes forming transition-type time sections in the measurement signal which separate plateau-type time sections, - determine a characteristic parameter of each of the plateau-type time sections.
[0017] Some preferred but non-limiting aspects of these devices are as follows: - the accumulator battery of the test device is a lithium titanate battery, a lithium iron phosphate battery or a lead acid battery; - to detect changes in contact type, the processor of the diagnostic device is configured to perform binary recursive partitioning of the measurement signal; - the processor of the diagnostic device is further configured to determine a circuit breaker wear indicator from the characteristic parameter determined for each of the plateau-type time sections; - to determine the wear indicator, the processor of the diagnostic device implements a pre-trained classifier; - the wear indicator qualifies a level of wear and / or a type of wear.
[0018] The invention also relates to a system for monitoring the health status of a high voltage circuit breaker, comprising a test apparatus according to the first aspect of the invention and a diagnostic apparatus according to the second aspect of the invention. Brief description of the drawings
[0019] Other aspects, objects, advantages and features of the invention will become more apparent from the following detailed description of preferred embodiments. of this, given as a non-limiting example, and made with reference to the attached drawings in which:
[0020] - [Fig.l] is a diagram illustrating a system for monitoring the health status of a high voltage circuit breaker according to the third aspect of the invention;
[0021] - [Fig.2] illustrates the automatic sequencing of a resistance measurement signal of dynamic contact made by the diagnostic apparatus according to the second aspect of the invention.
[0022] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS
[0023] According to a first aspect, and with reference to [Fig.l], the invention relates to a test apparatus 1 of a high voltage circuit breaker D. The high voltage circuit breaker D comprises main contacts (also called permanent contacts) and arcing contacts (also called breaking contacts) inside an extinguishing chamber. The high voltage circuit breaker may use a breaking gas such as sulfur hexafluoride (SF6) or an alternative gas (CO2, O2, g3, etc.).
[0024] The test apparatus 1 comprises a direct current source 10 capable of injecting a current into the breaking chamber of the high-voltage circuit breaker during an opening or closing operation of the high-voltage circuit breaker. The test apparatus 1 further comprises a voltage sensor 11 capable of measuring a voltage at the terminals of the high-voltage circuit breaker during the opening or closing operation of the high-voltage circuit breaker. The test apparatus 1 further comprises a data processing unit 12 configured to deliver, from the voltage measurement carried out by the voltage sensor and the amplitude of the current injected by the direct current source, an RCD signal for measuring the dynamic contact resistance of the high-voltage circuit breaker during the opening or closing operation of the high-voltage circuit breaker. In a possible embodiment shown in [Fig.l], the current source 10 and the voltage sensor 11 are connected to the breaking chamber so as to carry out a four-wire measurement.
[0025] The Applicant was able to demonstrate in the laboratory that the value of the dynamic resistance on the arcing contacts varies inversely with the amplitude of the current up to a certain threshold from which the value of the resistance then exhibits a certain stability allowing a repeatable measurement of it on the arcing contacts.
[0026] However, the current amplitudes generated by the devices currently available on the market are lower than that necessary to reach this stability zone. On the contrary, the invention proposes to use a current source which makes it possible to inject a sufficiently strong current. More particularly, in the test device according to the invention, the direct current source 10 is a storage battery capable of injecting a current of intensity greater than 1000 A during the opening or closing operation of said circuit breaker, for example an intensity between 1000 A and 1400 A. The high intensity of the injected current allows passage through all the contacts during the opening or closing operation and guarantees good repeatability of the measurements.
[0027] The recommended value based on the Applicant's experimental results is at least 1000 A. To take into account the aging of the battery modules, the dimensioning current used is preferably greater than this value, for example 1400 A.
[0028] In a preferred embodiment, the minimum battery capacity to be requested by injection is 200mAh. This value does not take into account any voltage drops in the resistances of the injection circuit (such as those of the cables for example). It makes it possible to reach, in short circuit, the high intensity current level necessary to ensure the success of the test, by preventing any variation in the voltage of the source during discharge.
[0029] In order to conduct a complete test on a three-phase circuit breaker (involving 3 measurements), several repetitions of the measurement must be carried out with a minimum of 5 measurements per compartment. Since it is possible to carry out measurements on several circuit breakers during a test, a battery capacity of at least 30 Ah can be recommended for an uninterrupted day of testing. Of course, a recharge of the battery can be carried out if necessary.
[0030] The storage battery of the test apparatus according to the invention may comprise one or more battery modules. In a preferred embodiment, the storage battery is a lithium titanate battery or a lithium iron phosphate battery or a lead acid battery. These battery technologies have the particularity of having a relatively stable voltage without parasitic reactions. In addition, they support higher currents, thus making the voltage at the terminals of the circuit breaker under test more stable for a quality measurement.
[0031] By using a storage battery capable of injecting a current of at least 1000 A, the test apparatus according to the invention makes it possible to guarantee better stability and repeatability of the measurements and therefore of the wear indicators, both electrical and mechanical, which are deduced therefrom. In addition, any variations in the source voltage can be neglected, since the discharge of the battery takes place quickly compared to its complete cycle. Under these conditions, the current source has a quasi-zero impedance, which guarantees the reliability of the digital analysis (described below) of the collected data as well as the consistency of the successive measurements.
[0032] According to a second aspect, and still with reference to [Fig.l], the invention relates to a diagnostic apparatus 2 for a high-voltage circuit breaker. This diagnostic apparatus comprises a processor 20 configured to obtain a signal for measuring the dynamic contact resistance RCD of the high-voltage circuit breaker during an operation opening or closing of the high voltage circuit breaker. In a preferred embodiment, this RCD signal corresponds to a measurement signal delivered by the processing unit 12 of the test device 1 previously described. This RCD signal can be transcribed into a computer file stored on a remote server and thus be made available to the diagnostic device 2.
[0033] The opening or closing operation of the circuit breaker causes a movement of the main contacts and the arcing contacts which results in changes in contact type. Taking the example of an opening operation, this presents three types of contact in succession and therefore two phases of changes in contact type between respectively the first and second type of contact and between the second and third type of contact.The first type of contact corresponds to the contact of the main contacts (for example a first type of contact of the Ag / Ag type), the second type of contact corresponding to a closed type contact of the arcing contacts (for example a second type of contact of the WCu / Cu type, with WCu the material of the female arcing contact and Cu the material of the body of the rod forming the male arcing contact) and a third type of contact corresponds to an opening type contact of the arcing contacts (for example a third type of contact of the WCu / WCu type, with WCu the material of the female arcing contact and WCu the material of the tip of the rod forming the male arcing contact which is now in contact with the female arcing contact). The first change of contact type is therefore an Ag / Ag to WCu / Cu change and the second change of contact type is therefore a WCu / Cu to WCu / WCu change.
[0034] The processor 20 of the diagnostic device 2 is configured to detect these changes in contact type in the RCD measurement signal. [Fig. 2] shows, on the one hand, the evolution of the current A and, on the other hand, the RCD measurement signal during an opening operation of a circuit breaker. As shown in [Fig. 2], the changes in contact type form in the RCD measurement signal transition-type time sections S2, S4 which separate plateau-type time sections S1, S3, S5 which correspond to the different types of contact. The processor thus sequences the measurement signal by dividing it into these different sections S1-S5. It should be noted that it is thanks to the injection of a high-intensity current that the measurement signal has such plateaus, each corresponding to a type of contact.
[0035] In a preferred embodiment, in order to identify the different sections S1-S5, the processor can be configured to perform a binary recursive partitioning of the measurement signal. Binary recursive partitioning is a supervised classification algorithm that creates a dichotomous tree where, at each node, a variable makes it possible to determine whether the traversal of the tree must be continued towards the left of the node (when the value of the variable is lower than a fixed threshold), or to its right (if the value is greater than or equal to this threshold). The choice of the variable used at each node, as well as the threshold value, are determined by the algorithm so as to maximize the separation between the two sub-entities thus obtained, which must discriminate as best as possible between the different groups to be identified. The processing is continued throughout the tree recursively until reaching an end, called a “leaf”, which represents a given class. In this case, the regression tree resulting from the binary recursive partitioning of the RCD measurement signal includes five leaves, each corresponding to one of the sections S1-S3 and therefore to one of the contact types or contact changes.
[0036] The processor 20 of the diagnostic apparatus 2 is further configured to determine one or more characteristic parameters of each of the plateau-type time sections S1, S3, S5. For example, the characteristic parameter(s) of a section comprise one and / or the other of an average value of the resistance over the section, the duration of the section, the distance traveled by the moving part of the contacts during the duration of the section (if displacement measured). It is easily understood that the more stable a plateau-type section is, the more the parameter(s) thus determined are representative of the state of the contact being checked.
[0037] These parameters can be transcribed into a computer file stored in a memory 22 of the diagnostic device. This file can also be transmitted for storage to a remote server, which may or may not be the same server as the one mentioned above storing the measurement files. Storing the parameters over the course of the various tests carried out on a circuit breaker makes it possible to monitor the evolution of these parameters and from there to make a diagnosis of the circuit breaker.
[0038] This method of analyzing the measurement signal for the automatic extraction of parameters representative of the different types of contacts controlled allows a non-expert profile to be able to easily interpret the results obtained as well as to compare them with each other. In this respect, the diagnostic device 2 can also comprise a human-machine interface 21 allowing an operator to view the resistance curve as well as the parameters determined during a test carried out on a circuit breaker. This human-machine interface 21 can also allow the operator to enter feedback on an inspection, for example visual, of the circuit breaker by allowing him to enter one or more wear indicators qualifying for example a level of wear and / or a type of wear of each of the types of contact of the circuit breaker. A level of wear is for example one of nine, correct, acceptable, degraded, bad, damaged.A wear type can be a mechanical wear type and / or an electrical wear type. A mechanical wear type can be taper wear, misalignment, mechanical clearance, or breakage. An electrical wear type can be weld spot wear or deep erosion.
[0039] This feedback makes it possible to feed a database in which the parameters determined during tests of different circuit breakers can be labeled by the wear indicators thus provided by feedback. This database can then be used as a training database for an automatic classification model.
[0040] The results of a test carried out on a circuit breaker can also be visualized by means of the human-machine interface 21 in a graphical representation where the results of reference tests which have been the subject of feedback are also represented. These reference test results can be associated in the graphical representation with a label corresponding to their wear indicator. Such a representation makes it possible to compare the results of a new test with the results of the reference tests and to evaluate a proximity with certain of the results of the reference tests. The label associated with the closest results makes it possible to estimate a wear indicator of the circuit breaker subject to the new test, for example a new rather than worn wear level.
[0041] In a possible embodiment, the processor 20 is further configured to determine a wear indicator of the circuit breaker from the characteristic parameter(s) of a type of contact determined for one or more plateau-type time sections. To perform this determination, the processor can implement a pre-trained classifier resulting from the training of the automatic classification model. This classifier makes it possible to assign the characteristic parameter(s) to a class from among a plurality of classes each representative of a level of wear and / or a type of wear.
[0042] The invention also extends to a system for monitoring the health status of a high-voltage circuit breaker, comprising a test device 1 and a diagnostic device 2 as described above. These devices may be remote devices or, on the contrary, be integrated into the same measuring case. This system considerably improves the accuracy of the measurements and allows more reliable identification of faults. It can also address the limitations of current devices by providing a more exhaustive and precise interpretation, which facilitates the consistent comparison of successive tests.
[0043] The invention also relates to a method for testing a high voltage circuit breaker, comprising the following steps: - injection, by a storage battery, of a direct current with an amplitude greater than 1000 A into a breaking chamber of the high-voltage circuit breaker during an opening or closing operation of the high-voltage circuit breaker, - measurement of a voltage at the terminals of the high voltage circuit breaker during the opening or closing operation of the high voltage circuit breaker, and - determination, from the measured voltage and the amplitude of the injected direct current, of a dynamic contact resistance measurement signal of the high voltage circuit breaker during the opening or closing operation of the high voltage circuit breaker.
[0044] The invention also relates to a method for diagnosing a high-voltage circuit breaker comprising main contacts and arcing contacts inside an extinguishing chamber, comprising the following steps: - obtaining a dynamic contact resistance measurement signal of the high voltage circuit breaker during an opening or closing operation of the high voltage circuit breaker, said operation causing a movement of the main contacts and the arcing contacts which results in changes in contact type, - detection of changes in contact type in the measurement signal, said changes forming in the measurement signal transition-type time sections which separate plateau-type time sections, - determination of a characteristic parameter of each of the plateau-type time sections.
[0045] The invention also relates to a computer program product comprising instructions which, when the program is executed by a computer, cause the latter to implement the test method and / or the diagnostic method.
Claims
Claims
1. Diagnostic apparatus (2) of a high voltage circuit breaker comprising main contacts and arcing contacts inside an extinguishing chamber, comprising a processor (20) configured to: - obtain a dynamic contact resistance (DCR) measurement signal of the high voltage circuit breaker during an opening or closing operation of the high voltage circuit breaker, said operation carrying out a movement of the main contacts and the arcing contacts which causes changes in contact type, - carry out a binary recursive partitioning of the measurement signal to detect the changes in contact type in the measurement signal, said changes forming in the measurement signal transition-type time sections which separate plateau-type time sections, - determine a characteristic parameter of each of the plateau-type time sections.
2. The diagnostic apparatus of claim 1, wherein the processor is further configured to determine a circuit breaker wear indicator from the characteristic parameter determined for each of the plateau-type time sections.
3. A diagnostic apparatus according to claim 2, wherein to determine the wear indicator, the processor implements a pre-trained classifier.
4. Diagnostic apparatus according to one of claims 2 and 3, in which the wear indicator qualifies a level of wear and / or a type of wear.
5. System for monitoring the health status of a high-voltage circuit breaker, comprising a diagnostic apparatus according to one of claims 1 to 4 and a test apparatus which comprises: - a direct current source (10) capable of injecting a current into a breaking chamber of the high-voltage circuit breaker during an opening or closing operation of the high-voltage circuit breaker, the direct current source being a storage battery capable of injecting a current of intensity greater than 1000A during the opening or closing operation of said circuit breaker; - a voltage sensor (11) capable of measuring a voltage at the terminals of the high-voltage circuit breaker during the opening or closing operation of the high-voltage circuit breaker, and - a data processing unit (12) configured to deliver, from the voltage measurement carried out by the voltage sensor and the amplitude of the current injected by the direct current source, a signal for measuring the dynamic contact resistance (RCD) of the high-voltage circuit breaker during the opening or closing operation of the high-voltage circuit breaker.
6. The system of claim 5, wherein the storage battery is a lithium titanate battery, a lithium iron phosphate battery or a lead acid battery.
7. A method for diagnosing a high-voltage circuit breaker comprising main contacts and arcing contacts inside an extinguishing chamber, comprising the following steps: - obtaining a dynamic contact resistance measurement signal of the high-voltage circuit breaker during an opening or closing operation of the high-voltage circuit breaker, said operation carrying out a movement of the main contacts and the arcing contacts which results in changes in contact type, - carrying out a binary recursive partitioning of the measurement signal to detect changes in contact type in the measurement signal, said changes forming transition-type time sections in the measurement signal which separate plateau-type time sections, - determining a characteristic parameter of each of the plateau-type time sections.
8. A computer program product comprising instructions which, when the program is executed by a computer, cause the latter to implement the method according to claim 7.