Low voltage circuit breaker contact detection device and method

Abstract

The present invention relates to a low-voltage circuit breaker contact detection device and method. A low-voltage circuit breaker contact detection device includes a contact, a reference resistor connected in series with the contact, a pressure difference detector, a filter, an analog-to-digital converter, a current transformer and a controller; the pressure difference detector is used to detect the voltage difference between the contact and the reference resistor, and is connected to the filter; the filter is connected to the analog-to-digital converter, and the analog-to-digital converter is connected to the controller; the current transformer is connected to the analog-to-digital converter. Compared with the prior art, the present invention provides a low-voltage circuit breaker contact detection device and method. This device has a built-in reference resistor. During use, by calculating the voltage difference between the contact and the reference resistor, and detecting the instantaneous current in real time and then calculating the contact, the real-time detection of contact growth 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 circuit breaker detection, and in particular to a low-voltage circuit breaker contact detection device and method. 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] The contact life of existing low-voltage circuit breakers is often assessed through statistical analysis of electrical wear based on the number of trips and interruptions and the current during interruption. This method is less accurate and can only serve as a rough reference, but cannot accurately assess the contact life of the circuit breaker.

[0004] 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.

[0005] Therefore, there are deficiencies in this field, and it is urgent to solve the above problems and deficiencies. Summary of the Invention

[0006] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a low-voltage circuit breaker contact detection device and method, which is used to solve the problem that the life of the low-voltage circuit breaker contacts cannot be accurately measured, and can effectively and accurately realize detection and evaluate the life of the contacts.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A low-voltage circuit breaker contact detection device comprises a contact, a reference resistor connected in series with the contact, a voltage difference detector, a filter, an analog-to-digital converter, a current transformer and a controller;

[0009] The differential pressure detector is used to detect the voltage difference between the contact and the reference resistor, and is connected to the filter;

[0010] The filter is connected to the analog-to-digital converter, the analog-to-digital converter is connected to the controller; and the current transformer is connected to the analog-to-digital converter.

[0011] Preferably, in the low-voltage circuit breaker contact detection device, the differential pressure detector includes a voltage divider and an amplifier.

[0012] Preferably, in the low-voltage circuit breaker contact detection device, the voltage divider includes a first voltage divider resistor, a second voltage divider resistor, and a third voltage divider resistor, the first voltage divider resistor and the second voltage divider resistor are respectively connected to the two ends of the output, and the second voltage divider resistor and the third voltage divider resistor are respectively connected to the two ends of the reference resistor.

[0013] Preferably, in the low-voltage circuit breaker contact detection device, the amplifier 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.

[0014] Preferably, in the low-voltage circuit breaker contact detection device, the filter includes an aluminum foil 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.

[0015] Preferably, in the low-voltage circuit breaker contact detection device, the resistance values ​​of the first voltage-dividing resistor, the second voltage-dividing resistor, and the third voltage-dividing resistor have the following relationship:

[0016] R1:R2:R3=2:1:2;

[0017] 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.

[0018] Preferably, in the low-voltage circuit breaker contact detection device, the resistance of the reference resistor is equal to the initial resistance of the contact.

[0019] Preferably, in the low-voltage circuit breaker contact detection device, the controller model is a single-chip microcomputer, and the signal of the single-chip microcomputer is R5F100.

[0020] A low-voltage circuit breaker contact detection method for the detection device includes the following steps:

[0021] S1, the voltage difference detector detects the voltage difference between the two ends of the contact and the two ends of the reference resistor, and after filtering, converts the voltage difference into a digital signal through the analog-to-digital converter and transmits it to the controller;

[0022] S2. The current transformer sends the detected real-time current data to the analog-to-digital converter, which converts the data into digital signals and transmits them to the controller to calculate the increased resistance value of the contact.

[0023] Preferably, the low-voltage circuit breaker contact detection method further includes the steps of:

[0024] S3. Compare the increased resistance value with the contact limit resistance value to determine the life of the contact.

[0025] Compared with the existing technology, the present invention provides a low-voltage circuit breaker contact detection device and method. This device has a built-in reference resistor. During use, it calculates the voltage difference between the contact and the reference resistor, and detects the instantaneous current in real time to calculate the contact, thereby realizing real-time detection of contact growth. This is efficient and accurate, and is a great advancement in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural block diagram of a low-voltage circuit breaker contact detection device provided by the present invention;

[0027] Figure 2 It is a structural diagram of the low-voltage circuit breaker contact detection device provided by the present invention;

[0028] Figure 3 The present invention provides a flow chart of a method for detecting contacts of a low-voltage circuit breaker. DETAILED DESCRIPTION

[0029] 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.

[0030] See also Figure 1-3 The present invention provides a low-voltage circuit breaker contact detection device, comprising a contact 1, a reference resistor 2 connected in series with the contact 1, a pressure difference detector 3, a filter 4, an analog-to-digital converter 5, a current transformer 6 and a controller 7;

[0031] The differential pressure detector 3 is used to detect the voltage difference between the contact 1 and the reference resistor 2, and is connected to the filter 4;

[0032] The filter 4 is connected to the analog-to-digital converter 5 , the analog-to-digital converter 5 is connected to the controller 7 ; the current transformer 6 is connected to the analog-to-digital converter 5 .

[0033] Accordingly, the present invention also provides a method for detecting contacts of a low-voltage circuit breaker using the detection device, comprising the steps of:

[0034] S1, the voltage difference detector 3 detects the voltage difference between the two ends of the contact 1 and the two ends of the reference resistor 2, and after filtering, converts it into a digital signal through the analog-to-digital converter and transmits it to the controller 7;

[0035] S2. The current transformer 6 sends the detected real-time current data to the analog-to-digital converter 5, which converts the data into digital signals and transmits them to the controller 7 to calculate the increased resistance value of the contact 1.

[0036] Specifically, since the rated current passing through the circuit breaker is large, generally hundreds to thousands of amperes, in order to ensure that the circuit breaker generates little heat, the resistance of its contacts is very small, generally in the micro-ohm level, so the conventional method of directly measuring the circuit breaker contacts is not feasible. Therefore, this is achieved by adding a reference resistor, and the resistance of the circuit breaker contacts is measured by comparing the resistance value of the reference resistor. The contact 1 and the reference resistor 2 are both connected in series in the primary circuit of the circuit breaker. Since the rated current of the circuit breaker is generally hundreds or thousands of amperes, during use, the number of times the circuit breaker contact 1 is used will cause its own resistance to increase. At this time, due to the increase in resistance, its heating power is calculated according to the formula: p=I 2 *R (P is the heating power of contact 1, I is the current flowing through contact 1, and R is the resistance of contact 1) will also increase rapidly. If the circuit breaker's contact resistance is too high, the heating power will increase. If the circuit breaker overheats abnormally for a long time, the circuit breaker temperature will continue to rise, damaging components and eventually burning out the circuit breaker. In the initial stage of the circuit breaker, its resistance is micro-ohms. After repeated opening and closing, when the resistance of contact 1 increases to the milliohm level, the life of contact 1 has reached the end. If it continues to use, the heating power may increase, and contact 1 may cause a fuse failure, which is dangerous.

[0037] Therefore, if the growing resistance of the contact 1 can be determined simply and quickly, the service life of the contact 1 can be determined quickly. However, it is not easy to measure or calculate the resistance of the contact 1, because the resistance of the contact 1 is in the micro-ohm range, so the voltage across the contact 1 is also very low, and the measurement accuracy is very high. In order to quickly and effectively measure the growing resistance of the contact 1, the present invention connects a reference resistor 2 in series in the circuit where the contact 1 is located, and can measure the voltage difference signal across the contact 1 and the reference resistor 2. After filtering by the filter 4, the voltage difference signal is sent to the analog-to-digital converter 5 to be converted into a digital signal. At the same time, the instantaneous current value is detected by the current transformer 6. The measurement accuracy can be improved through calculation by the controller 7, and fast measurement can be achieved.

[0038] Because the circuit breaker's contact 1 and reference resistor 2 both enter and exit the primary circuit, the current in the primary circuit of contact 1 and reference resistor 2 at the same time is the same. Therefore, the voltage signals of the two depend on their resistance values.

[0039] Generally, the voltage calculation formula across the contact 1 is:

[0040] Uct =I*R ct ;

[0041] Among them, U ct is the voltage across the contact 1; R ct is the resistance value of the contact 1; I is the current in the primary circuit.

[0042] The voltage calculation formula across the reference resistor 2 is:

[0043] U jz =I*R jz ;

[0044] Among them, U jz is the voltage across the reference resistor 2; R jz is the resistance value of the reference resistor 2; I is the current in the primary circuit.

[0045] The voltage difference between the contact 1 and the reference resistor 2 is calculated as follows:

[0046] △U=U ct -U jz ;

[0047] Among them, U ct is the voltage across the contact 1; U jz is the voltage across the reference resistor 2; ΔU is the voltage difference between the contact 1 and the reference resistor 2.

[0048] As a preferred solution, in this embodiment, the differential pressure detector 3 includes a voltage divider and an amplifier 32 .

[0049] As a preferred solution, in this embodiment, the voltage divider includes a first voltage divider resistor 311, a second voltage divider resistor 312, and a third voltage divider resistor 313. The first voltage divider resistor 311 and the second voltage divider resistor 312 are respectively connected to the two ends of the output, and the second voltage divider resistor 312 and the third voltage divider resistor 313 are respectively connected to the two ends of the reference resistor 2.

[0050] As a preferred solution, in this embodiment, the amplifier 32 is an operational amplifier. The other ends of the first voltage-dividing resistor 311 and the third voltage-dividing resistor 313 are respectively connected to the negative input terminal of the operational amplifier; the other end of the second voltage-dividing resistor 312 is connected to the positive input terminal of the operational amplifier. The signal of the operational amplifier is AD620.

[0051] Specifically, the voltage across the circuit breaker contact 1 and the reference resistor 2 is collected, divided by the first voltage-dividing resistor 311, the second voltage-dividing resistor 312, and the third voltage-dividing resistor 313, and connected to the signal input end of the amplifier after voltage division. Therefore, the difference between the voltage across the circuit breaker contact 1 and the voltage across the reference resistor 2 can be compared, and the difference signal is amplified and conditioned. The difference signal is converted into a digital signal by the analog-to-digital converter 5 for analysis and judgment by the controller 7. The signal is then combined with the real-time current value detected by the current transformer 6 to determine the contact resistance of the circuit breaker contact 1.

[0052] As a preferred solution, in this embodiment, the filter 4 includes a filter resistor 41 and a filter capacitor 42. One end of the filter resistor 41 is connected to the amplifier 32, and the other end is respectively connected to the filter capacitor 42 and the analog-to-digital converter 5; the other end of the filter capacitor 42 is grounded to form a low-pass filter 4 to filter out high-frequency noise.

[0053] Since the resistance values ​​of the contact 1 and the reference resistor 2 are extremely small, the voltage signal at both ends of the two is very small. Therefore, the pressure difference between the two needs to be amplified by the amplifier circuit, and then filtered by the filter 4 to filter out high-frequency noise. Finally, it is sent to the analog-to-digital conversion circuit to convert the analog signal into a digital signal and transmit it to the controller 7.

[0054] As a preferred solution, in this embodiment, the resistance values ​​of the first voltage-dividing resistor, the second voltage-dividing resistor, and the third voltage-dividing resistor have the following relationship:

[0055] R1:R2:R3=2:1:2;

[0056] R1 is the resistance of the first voltage-dividing resistor 311 ; R2 is the resistance of the second voltage-dividing resistor 312 ; and R3 is the resistance of the third voltage-dividing resistor 313 .

[0057] As a preferred solution, in this embodiment, the resistance of the reference resistor 2 is equal to the initial resistance of the contact 1 .

[0058] 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 is: 20-200MΩ, and the resistance value range of the second voltage divider resistor is 10-100MΩ. Therefore, when the circuit breaker contact 1 is disconnected, the voltage across the contact 1 is as high as several hundred volts and will not damage the circuit.

[0059] The analog-to-digital converter 5 includes an AD conversion chip and peripheral devices, and converts the analog signal of the voltage difference into a digital signal. The specific model of the AD conversion chip is AD7768. The specific model of the controller 7 is R5F100.

[0060] Of course, in this embodiment, the detection device also includes an alarm device with a display and a speaker, which sends out fault information according to the instructions of the controller 7 and reminds the user to replace the circuit breaker immediately.

[0061] 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 low voltage circuit breaker contact detection device, characterized in that: It includes a contact, a reference resistor connected in series with the contact, a voltage difference detector, a filter, an analog-to-digital converter, a current transformer and a controller; The differential pressure detector is used to detect the voltage difference between the contact and the reference resistor, and is connected to the filter; The filter is connected to the analog-to-digital converter, the analog-to-digital converter is connected to the controller; the current transformer is connected to the analog-to-digital converter; The differential pressure detector includes a voltage divider and an amplifier; the voltage divider includes a first voltage divider resistor, a second voltage divider resistor, and a third voltage divider resistor, the first voltage divider resistor and the second voltage divider resistor are respectively connected to the two ends of the contact, and the second voltage divider resistor and the third voltage divider resistor are respectively connected to the two ends of the reference resistor; the amplifier is an operational amplifier, the other ends of the first voltage divider resistor and the third voltage divider resistor are respectively connected to the negative electrode of the input end of the operational amplifier; the other end of the second voltage divider resistor is connected to the positive electrode of the input end of the operational amplifier; the resistance value of the reference resistor is equal to the initial resistance value of the contact; The filter includes an aluminum foil resistor and a filter capacitor. One end of the aluminum foil 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.

2. The low-voltage circuit breaker contact detection device 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.

3. The low-voltage circuit breaker contact detection device according to claim 1, characterized in that: The controller model is a single chip microcomputer, and the signal of the single chip microcomputer is R5F100.

4. A low-voltage circuit breaker contact detection method for the detection device according to any one of claims 1 to 3, characterized in that: Including steps: S1, the voltage difference detector detects the voltage difference between the two ends of the contact and the two ends of the reference resistor, and after filtering, converts the voltage difference into a digital signal through the analog-to-digital converter and transmits it to the controller; S2. The current transformer sends the detected real-time current data to the analog-to-digital converter, which converts the data into digital signals and transmits them to the controller to calculate the increased resistance value of the contact.

5. The low-voltage circuit breaker contact detection method according to claim 4, characterized in that: Also includes the steps: S3. Compare the increased resistance value with the contact limit resistance value to determine the life of the contact.

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