A system and method for detecting the life of three-phase contacts of a low-voltage circuit breaker

Abstract

The present invention relates to a three-phase contact detection system and method for a low-voltage circuit breaker. A three-phase contact life detection system for a low-voltage circuit breaker includes a phase A detection component, a phase B detection component, a phase C detection component, a detection device, and a controller; the controller is connected to the phase A detection component, the phase B detection component, the phase C detection component, and the detection device, respectively; the detection device is used to detect whether the contact is in a closed state; the phase A detection component, the phase B detection component, and the phase C detection component are the same detection components; the detection component includes: a reference resistor, a signal conditioning device, an isolation device, and a current transformer. This device has a built-in reference resistor. During use, by calculating the voltage difference between the three-phase contact and the corresponding reference resistor, and detecting the instantaneous current in real time and then calculating the contact, the real-time detection of the contact resistance change is achieved, which is efficient and accurate, and is a great advancement in this field.

Description

Technical Field

[0001] The present invention relates to the field of contact detection, and in particular to a three-phase contact detection system and method for a low-voltage circuit breaker. Background Art

[0002] The electrical life of a low-voltage circuit breaker is closely linked to its contacts. Burnout of the contact system increases contact resistance, raising the breaker's temperature and reducing its breaking capacity, posing a risk to equipment operation. However, the life of a circuit breaker's contacts decreases with increasing breaking cycles. Therefore, a method for online contact life monitoring is needed to assess the electrical life of the circuit breaker and effectively prevent failures caused by these issues.

[0003] Patent document with application number 201811008454.8 discloses a high-precision online detection method for circuit breaker contact wear rate. It requires measuring the ambient temperature and current, and calculating the contact wear rate based on the number of switching times. This method can solve some problems, but it requires considering many parameters, and the calculation is relatively complex. The wear rate is also calculated, and its accuracy is limited by the model and material.

[0004] Existing low-voltage circuit breaker contact lifespan assessments often rely on statistical analysis of electrical wear, based on the number of trips and interruptions and the current during the trips. This method is inaccurate and can only serve as a rough guide, failing to accurately assess the contact lifespan of the circuit breaker. Therefore, this area presents deficiencies and calls for further research and innovation. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a three-phase contact detection system and method for a low-voltage circuit breaker. In order to solve the problem that the life of the low-voltage circuit breaker contacts cannot be accurately assessed, the life of the contacts is judged by the change in the resistance of the contacts, which can effectively and accurately monitor and assess the contact life.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A three-phase contact life detection system for a low-voltage circuit breaker, comprising a phase A detection component, a phase B detection component, a phase C detection component, a detection device, and a controller;

[0008] The controller is respectively connected to the A-phase detection component, the B-phase detection component, the C-phase detection component, and the detection device;

[0009] The detection device is used to detect whether the contact is in the closed state;

[0010] The A-phase detection component, the B-phase detection component and the C-phase detection component are the same detection components;

[0011] The detection component includes: a reference resistor, a signal conditioning device, an isolation device, and a current transformer;

[0012] The reference resistor is connected in series with the contact of the phase;

[0013] The signal conditioning device is used to detect the difference between the voltages at both ends of the contact and the reference resistor;

[0014] The isolation device is used to isolate the three-phase detection component to prevent signal serialization, and is connected to the signal conditioning device and the controller;

[0015] The current transformer is used to detect the current of the current phase circuit and is connected to the controller.

[0016] Preferably, in the three-phase contact life detection system for a low-voltage circuit breaker, the signal conditioning device includes a first voltage-dividing resistor, a second voltage-dividing resistor, a third voltage-dividing resistor, a pressure difference detection device, and an analog-to-digital conversion device;

[0017] The first voltage-dividing resistor and the second voltage-dividing resistor are connected to both ends of the contact respectively; the second voltage-dividing resistor and the third voltage-dividing resistor are connected to both ends of the reference resistor respectively;

[0018] The first voltage-dividing resistor, the second voltage-dividing resistor, and the third voltage-dividing resistor are respectively connected to the pressure difference device;

[0019] The pressure difference detection device is connected to the analog-to-digital conversion device; and the analog-to-digital conversion device is connected to the isolation device.

[0020] Preferably, in the three-phase contact life detection system for a low-voltage circuit breaker, the pressure difference detection device is an operational amplifier, and the other ends of the first voltage-dividing resistor and the third voltage-dividing resistor are respectively connected to the negative electrode of the input end of the operational amplifier; the other end of the second voltage-dividing resistor is connected to the positive electrode of the input end of the operational amplifier.

[0021] Preferably, in the low-voltage circuit breaker three-phase contact life detection system, the resistance values ​​of the first voltage-dividing resistor, the second voltage-dividing resistor, and the third voltage-dividing resistor have the following relationship:

[0022] R1:R2:R3=2:1:2;

[0023] Wherein, R1 is the resistance value of the first voltage-dividing resistor; R2 is the resistance value of the second voltage-dividing resistor; and R3 is the resistance value of the third voltage-dividing resistor.

[0024] Preferably, in the low-voltage circuit breaker three-phase contact life detection system, the isolation device includes an isolation signal device and an isolation power supply, the signal conditioning device is connected to the isolation signal device and the isolation power supply respectively; the isolation signal device is connected to the controller.

[0025] Preferably, in the low-voltage circuit breaker three-phase contact life detection system, the resistance value of the reference resistor is the same as the initial resistance value of the contact.

[0026] Preferably, in the low-voltage circuit breaker three-phase contact life detection system, the controller includes a data processor and a current collector; the current collector is connected to the current transformer and the data processor respectively.

[0027] A method for detecting the life of three-phase contacts of a low-voltage circuit breaker for the system includes the following steps:

[0028] S1, the detection device detects whether the contacts of the three phases are all in the closed state. If not, the detection ends; if so, step S2 is executed;

[0029] S2. The controller receives the pressure difference signals between the contacts of the phase A detection component, the phase B detection component, and the phase C detection component and the reference resistor and the line instantaneous current, and calculates the contact growth resistance value of each phase in the three phases;

[0030] S3. Compare the resistances with the predetermined resistances to determine whether they are greater than the predetermined resistances. If so, the corresponding circuit breaker contacts are at risk of failure or are faulty. If not, the corresponding circuit breaker contacts are normal, and step S1 is executed.

[0031] Preferably, in the method for detecting the life of three-phase contacts of a low-voltage circuit breaker, in step S3, when there is a risk of failure or failure of the circuit breaker contacts, a warning message is issued externally.

[0032] Preferably, in the method for detecting the life of three-phase contacts of a low-voltage circuit breaker, the predetermined resistance is 1-1.5 milliohms.

[0033] Compared with the existing technology, the present invention provides a three-phase contact detection system and method for a low-voltage circuit breaker. This device has a built-in reference resistor. During use, it calculates the voltage difference between the three-phase contacts and the corresponding reference resistor, and detects the instantaneous current in real time to calculate the contacts, thereby realizing real-time detection of changes in contact resistance. This is efficient and accurate, and is a great advancement in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention provides a low-voltage circuit breaker three-phase contact life detection system structure frame Figure 1 ;

[0035] Figure 2 It is a structural block diagram of the detection component provided by the present invention;

[0036] Figure 3 It is a structural block diagram of the signal conditioning device provided by the present invention;

[0037] Figure 4 The present invention provides a low-voltage circuit breaker three-phase contact life detection system structure frame Figure 2 ;

[0038] Figure 5 The present invention provides a circuit diagram for implementing a three-phase contact life detection system for a low-voltage circuit breaker. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] See also Figures 1-4 The present invention provides a three-phase contact life detection system for a low-voltage circuit breaker, comprising an A-phase detection group 1, a B-phase detection component 2, a C-phase detection component 3, a detection device 4, and a controller 5;

[0041] The controller 5 is respectively connected to the A-phase detection component 1, the B-phase detection component 2, the C-phase detection component 3, and the detection device 4;

[0042] The detection device 4 is used to detect whether the contact is in the closed state;

[0043] The A-phase detection component 1, the B-phase detection component 2, and the C-phase detection component 3 are identical detection components;

[0044] The detection component includes: a reference resistor 12, a signal conditioning device 13, an isolation device 14, and a current transformer 15;

[0045] The reference resistor 12 is connected in series with the contact 11 of the phase;

[0046] The signal conditioning device 13 is used to detect the difference between the voltages at both ends of the contact 11 and the reference resistor 12;

[0047] The isolation device 14 is used to isolate the three-phase detection component to prevent signal serialization, and is connected to the signal conditioning device 13 and the controller 5;

[0048] The current transformer 15 is used to detect the current of the phase circuit and is connected to the controller 5 .

[0049] Accordingly, the present invention also provides a method for detecting the life of three-phase contacts of a low-voltage circuit breaker for the system, comprising the steps of:

[0050] S1, the detection device 4 detects whether the contacts of the three phases are all in the closed state. If not, the detection ends; if so, step S2 is executed;

[0051] S2, the controller receives the pressure difference signals between the contacts and the reference resistor of the A-phase detection component 1, the B-phase detection component 2, and the C-phase detection component 3, and the instantaneous current of the line, and calculates the contact growth resistance value of each phase in the three phases;

[0052] S3. Compare the resistances with the predetermined resistances to determine whether they are greater than the predetermined resistances. If so, the corresponding circuit breaker contacts are at risk of failure or are faulty. If not, the corresponding circuit breaker contacts are normal, and step S1 is executed.

[0053] Specifically, due to the large voltage difference between the three-phase lines, they need to be isolated from each other. The life detection device of the contact in the three-phase line has three groups of detection components, namely the A-phase detection component 1, the B-phase detection component 2 and the C-phase detection component 3. The A / B / C-phase detection components are the same detection components. The detection components include the reference resistor 12, the signal conditioning device 13, the isolation device 14, and the current transformer 15. Further, the A-phase detection component 1 includes the A-phase reference resistor 102, the A-phase signal conditioning device 103, the A-phase signal conditioning device 104, the A-phase signal conditioning device 105, the A-phase signal conditioning device 106, the A-phase signal conditioning device 107, the A-phase signal conditioning device 108, the A-phase signal conditioning device 109, the A-phase signal conditioning device 110, the A-phase signal conditioning device 111, the A-phase signal conditioning device 112, the A-phase signal conditioning device 113, the A-phase signal conditioning device 114, the A-phase signal conditioning device 115, the A-phase signal conditioning device 116, the A-phase signal conditioning device 117, the A-phase signal conditioning device 118, the A-phase signal conditioning device 119, the A-phase signal conditioning device 120, the A-phase signal conditioning device 119, the A-phase signal conditioning device 111, the A-phase signal conditioning device 111, the A-phase signal conditioning device 112, the A-phase signal conditioning device 113, the A-phase signal conditioning device 114, the A-phase signal conditioning device 115, the A-phase signal conditioning device 116, the A-phase signal conditioning device 117, the A-phase signal conditioning device 118, the A-phase signal conditioning device 119, the A-phase signal conditioning device 119, the A-phase signal conditioning device Phase isolation device 104, A-phase current transformer 105; the A-phase reference resistor 102 is connected in series with the A-phase contact 101; the B-phase detection component 2 includes a B-phase reference resistor 202, a B-phase signal conditioning device 203, a B-phase isolation device 204, and a B-phase current transformer 205; the B-phase reference resistor 202 is connected in series with the B-phase contact 201; the C-phase detection component 3 includes a C-phase reference resistor 302, a C-phase signal conditioning device 303, a C-phase isolation device 304, and a C-phase current transformer 305; the C-phase reference resistor 302 is connected in series with the C-phase contact 301.

[0054] Before the detection begins, the detection device detects whether the three-phase contacts (i.e., phase A contact 101, phase B contact 201, and phase C contact 301) are all in the closed state at the same time, that is, the three-phase line is in a normal conductive state. When it is determined that the three-phase contacts are all in the closed state, the three-phase signal conditioning device respectively detects the voltage difference data between the contact of the phase and the reference resistance of the phase, and the three-phase current transformer respectively detects the instantaneous current value of the phase. Then, the controller respectively receives the pressure difference data and instantaneous current data transmitted by the isolation device in the three-phase detection component, and calculates the growth resistance value of each of the three-phase contacts. After the calculation, the growth resistance value of the A / B / C phase contacts is respectively compared with the predetermined resistance value to determine whether each contact has a fault. As long as there is a risk of failure in any of the three-phase contacts, the circuit breaker is judged to be faulty.

[0055] As a preferred solution, in this embodiment, the signal conditioning device 13 includes a first voltage-dividing resistor 131, a second voltage-dividing resistor 132, a third voltage-dividing resistor 133, a pressure difference detection device 134 and an analog-to-digital conversion device 135;

[0056] The first voltage-dividing resistor 131 and the second voltage-dividing resistor 132 are connected to both ends of the contact 11 respectively; the second voltage-dividing resistor 132 and the third voltage-dividing resistor 133 are connected to both ends of the reference resistor 12 respectively;

[0057] The first voltage-dividing resistor 131 , the second voltage-dividing resistor 132 , and the third voltage-dividing resistor 133 are respectively connected to the pressure difference device 134 ;

[0058] The pressure difference detection device 134 is connected to the analog-to-digital conversion device 135 ; the analog-to-digital conversion device 135 is connected to the isolation device 14 .

[0059] It should be noted that the signal conditioning devices are respectively an A-phase signal conditioning device 103, a B-phase signal conditioning device 203, and a C-phase signal conditioning device 303; the A-phase signal conditioning device 103 includes an A-phase first voltage-dividing resistor 1031, an A-phase second voltage-dividing resistor 1032, an A-phase third voltage-dividing resistor 1033, an A-phase pressure difference detection device 1034, and an A-phase analog-to-digital conversion device 1035; the B-phase signal conditioning device 203 includes a B-phase first voltage-dividing resistor 2031, a B-phase second voltage-dividing resistor 2032, a B-phase third voltage-dividing resistor 2033, a B-phase pressure difference detection device 2034, and a B-phase analog-to-digital conversion device 2035; the C-phase signal conditioning device 303 includes a C-phase first voltage-dividing resistor 3031, a C-phase second voltage-dividing resistor 3032, a C-phase third voltage-dividing resistor 3033, a C-phase pressure difference detection device 3034, and a C-phase analog-to-digital conversion device 3035.

[0060] As a preferred solution, in this embodiment, the pressure difference detection device 134 is an operational amplifier, and the other ends of the first voltage-dividing resistor 131 and the third voltage-dividing resistor 133 are respectively connected to the negative electrode of the input end of the operational amplifier; the other end of the second voltage-dividing resistor 132 is connected to the positive electrode of the input end of the operational amplifier.

[0061] As a preferred solution, in this embodiment, the resistance values ​​of the first voltage-dividing resistor 131 , the second voltage-dividing resistor 132 , and the third voltage-dividing resistor 133 have the following relationship:

[0062] R1:R2:R3=2:1:2;

[0063] R1 is the resistance of the first voltage-dividing resistor 131 ; R2 is the resistance of the second voltage-dividing resistor 132 ; and R3 is the resistance of the third voltage-dividing resistor 133 .

[0064] Specifically, when collecting the voltage across the circuit breaker contact and the reference resistor, the voltage is divided by the first voltage-dividing resistor 131, the second voltage-dividing resistor 132, and the third voltage-dividing resistor 133, and then connected to the signal input end of the amplifier after voltage division. Therefore, the difference between the circuit breaker contact voltage and the voltage across the reference resistor can be compared, and the difference signal is amplified and conditioned. The difference signal is then converted into a digital signal by the analog-to-digital conversion device 135 for analysis and judgment by the controller 5, and then combined with the real-time current value detected by the current transformer to determine the contact resistance of the circuit breaker contact.

[0065] Specifically, since the resistance of the circuit breaker contacts changes from extremely small to extremely large when opening and closing. And the primary circuit is energized, it is necessary to divide the signal by a large resistor (megaohm level) to achieve signal range control within the voltage tolerance range of the signal conditioning module. Therefore, the resistance value of the first / second / third voltage divider resistor is in the megaohm (MΩ) level, and the voltage divider is composed of three voltage divider resistors. The resistance value range of the first / third voltage divider resistor 131 / 133 is: 20-200MΩ, and the resistance value range of the second voltage divider resistor 132 is 10-100MΩ. Therefore, when the circuit breaker contacts are disconnected, the voltage across the contacts is as high as several hundred volts and will not damage the circuit.

[0066] As a preferred solution, in this embodiment, the filter includes a filter resistor and a filter capacitor, one end of the filter resistor is connected to the amplifier, and the other end is respectively connected to the filter capacitor and the analog-to-digital converter; the other end of the filter capacitor is grounded to form a low-pass filter to filter out high-frequency noise.

[0067] Since the resistance values ​​of the contacts and the reference resistor are extremely small, the voltage signals at both ends of the two are very small. Therefore, the pressure difference between the two needs to be amplified by an amplifier circuit, and then filtered by a filter to filter out high-frequency noise. Finally, it is sent to an analog-to-digital conversion circuit to convert the analog signal into a digital signal, which is then sent to the isolation device and then to the controller.

[0068] As a preferred solution, in this embodiment, the isolation device 14 includes an isolation signal device and an isolation power supply, and the signal conditioning device is connected to the isolation signal device and the isolation power supply respectively; the isolation signal device is connected to the controller.

[0069] Please also refer to Figure 5 , the terminals with the same markings in the figure are connected together, and the unnumbered components are peripheral components. Specifically, in order to prevent signal interference between the three-phase detection components, an isolation device is added between the analog-to-digital conversion device and the controller, and the isolation device includes the isolation signal device and the isolation power supply. The analog-to-digital conversion device is connected to the isolation signal device, and the isolation signal device is connected to the controller; the isolation signal device is used to transmit the signal to the controller, and the isolation power supply is used to power the pressure difference detection. The isolation signal device is connected to the controller and is used to transmit the differential pressure data of each phase to the controller. The A-phase isolation device includes the A-phase isolation signal device U20 and the A-phase isolation power supply U8; the B-phase isolation device includes the B-phase isolation signal device U21 and the B-phase isolation power supply U9; the C-phase isolation device includes the C-phase isolation signal device U23 and the C-phase isolation power supply U10.

[0070] As a preferred solution, in this embodiment, the controller includes a data processor U3 and a current collector U11; the current collector U11 is connected to the current transformer 15 and the data processor U3 respectively.

[0071] Specifically, the current transformer 15 is a magnetic induction element with an isolation function, so the current transformer does not need to be isolated and can be directly connected to the controller to transmit real-time current data.

[0072] As a preferred solution, in this embodiment, the resistance value of the reference resistor is the same as the initial resistance value of the contact.

[0073] As a preferred solution, this embodiment further includes an alarm device for issuing a warning message according to the instruction of the controller in the event of a circuit breaker failure.

[0074] In step S3, when there is a risk of failure or failure of the circuit breaker contacts, a warning message is issued to the outside.

[0075] As a preferred solution, in this embodiment, the predetermined resistance is 1-1.5 milliohms.

[0076] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A three-phase contact life detection system for a low-voltage circuit breaker, characterized in that: It includes a phase A detection component, a phase B detection component, a phase C detection component, a detection device and a controller; The controller is respectively connected to the A-phase detection component, the B-phase detection component, the C-phase detection component, and the detection device; The detection device is used to detect whether the contact is in the closed state; The A-phase detection component, the B-phase detection component and the C-phase detection component are the same detection components; The detection component includes: a reference resistor, a signal conditioning device, an isolation device, and a current transformer; The reference resistor is connected in series with the contact of the phase; The signal conditioning device is used to detect the difference between the voltages at both ends of the contact and the reference resistor; The signal conditioning device includes a first voltage-dividing resistor, a second voltage-dividing resistor, a third voltage-dividing resistor, a pressure difference detection device and an analog-to-digital conversion device; The first voltage-dividing resistor and the second voltage-dividing resistor are connected to both ends of the contact respectively; the second voltage-dividing resistor and the third voltage-dividing resistor are connected to both ends of the reference resistor respectively; The first voltage-dividing resistor, the second voltage-dividing resistor, and the third voltage-dividing resistor are respectively connected to the pressure difference detection device; The pressure difference detection device is connected to the analog-to-digital conversion device; the analog-to-digital conversion device is connected to the isolation device; The isolation device is used to isolate the three-phase detection component to prevent signal serialization, and is connected to the signal conditioning device and the controller; The isolation device includes an isolation signal device and an isolation power supply, and the signal conditioning device is connected to the isolation signal device and the isolation power supply respectively; the isolation signal device is connected to the controller; The current transformer is used to detect the current of the current phase circuit and is connected to the controller.

2. The low-voltage circuit breaker three-phase contact life detection system according to claim 1, characterized in that: The pressure difference detection device is an operational amplifier, the other ends of the first voltage-dividing resistor and the third voltage-dividing resistor are respectively connected to the negative electrode of the input end of the operational amplifier; the other end of the second voltage-dividing resistor is connected to the positive electrode of the input end of the operational amplifier.

3. The low-voltage circuit breaker three-phase contact life detection system according to claim 1, characterized in that: The resistance values ​​of the first voltage-dividing resistor, the second voltage-dividing resistor, and the third voltage-dividing resistor have the following relationship: R1:R2:R3=2:1:2; Wherein, R1 is the resistance value of the first voltage-dividing resistor; R2 is the resistance value of the second voltage-dividing resistor; and R3 is the resistance value of the third voltage-dividing resistor.

4. The low-voltage circuit breaker three-phase contact life detection system according to claim 1, characterized in that: The resistance value of the reference resistor is the same as the initial resistance value of the contact.

5. The low-voltage circuit breaker three-phase contact life detection system according to claim 1, characterized in that: The controller includes a data processor and a current collector; the current collector is connected to the current transformer and the data processor respectively.

6. A method for detecting the life of three-phase contacts of a low-voltage circuit breaker used in the system according to any one of claims 1 to 5, characterized in that: Including steps: S1, the detection device detects whether the contacts of the three phases are all in the closed state. If not, the detection ends; if so, step S2 is executed; S2. The controller receives the pressure difference signals between the contacts of the phase A detection component, the phase B detection component, and the phase C detection component and the reference resistor and the line instantaneous current, and calculates the contact growth resistance value of each phase in the three phases; S3. Compare the resistances with the predetermined resistances to determine whether they are greater than the predetermined resistances. If so, the corresponding circuit breaker contacts are at risk of failure or are faulty. If not, the corresponding circuit breaker contacts are normal, and step S1 is executed.

7. The method for detecting the life of three-phase contacts of a low-voltage circuit breaker according to claim 6, characterized in that: In step S3, when there is a risk of failure or failure of the circuit breaker contacts, a warning message is issued to the outside.

8. The method for detecting the life of three-phase contacts of a low-voltage circuit breaker according to claim 6, characterized in that: The predetermined resistance is 1-1.5 milliohms.

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