Circuit breaker

Abstract

The utility model discloses a circuit breaker. The service life evaluation unit is used for evaluating the residual electric operation service life of the circuit breaker according to current measurement data records of the current measurement unit; the current measuring unit comprises a first current measuring circuit and a second current measuring circuit which are arranged in parallel; the first current measurement circuit is a current measurement circuit based on an iron core current transformer, a current measurement value ICT of the first current measurement circuit is used as a current basis for circuit breaker protection action judgment, and when the ICT is in a linear measurement range of the iron core current transformer, the ICT is used as current measurement data for recording; the second current measurement circuit is a current measurement circuit based on a PCB Rogowski coil transformer, and the current measurement value IRC of the second current measurement circuit is recorded as current current measurement data when the ICT is out of the linear measurement range of the iron core current transformer. Compared with the prior art, the device can accurately measure the fault current, and further provides an accurate basis for the evaluation of the service life of electric operation.

Description

Technical Field

[0001] This utility model relates to a circuit breaker. Background Technology

[0002] With the advancement of technology, low-voltage circuit breakers are constantly developing towards intelligence and miniaturization. In addition to traditional protection functions, functions such as health diagnosis and power monitoring are becoming new demands. These new functions are based on the accurate measurement of various electrical parameters, especially current, and rely on high-performance electronic protection devices and various sensors, including current transformers.

[0003] When a power system trips due to a fault, the circuit breaker contacts will burn out after interrupting the fault current. When the burnout reaches a certain level, the circuit breaker's operating capacity decreases, potentially preventing it from interrupting the fault current and causing a system accident. Therefore, it is necessary to assess and maintain the electrical operating life of the circuit breaker. The degree of contact burnout is related to the magnitude of the fault current it interrupts; the larger the interrupted fault current, the more severe the contact burnout. Tests can determine the reliable interruption count of the circuit breaker under different currents, allowing us to summarize the impact coefficient of interrupting different currents on the circuit breaker's electrical operating life. Therefore, accurately assessing the remaining electrical operating life of a circuit breaker requires accurate measurement of the fault current, especially larger fault currents.

[0004] Traditional low-voltage circuit breakers (especially molded case circuit breakers) commonly employ a technology that uses iron-core current transformers for both current detection and self-powered supply. However, because the primary operating current of low-voltage circuit breakers ranges from a few amperes to thousands or even tens of thousands of amperes, this current detection scheme using iron-core current transformers suffers from nonlinear distortion of the output signal due to high current saturation, making it impossible to accurately measure large fault currents. For example, circuit breaker iron-core current transformers can generally only guarantee a certain linearity requirement for the output at currents up to 1 to 4 times the rated current. Measuring larger currents requires different correction factors. The maximum measurable current of a circuit breaker based on an iron-core current transformer is generally limited to near its maximum protection setting current. However, the actual breaking current capacity of a circuit breaker may be far greater than its maximum protection setting current, which makes it impossible to accurately assess the remaining electrical operating life of circuit breakers based on this technology.

[0005] Another improved solution is to adopt a dual current transformer technology that integrates a core current transformer for power supply and a traditional Rogowski coil current transformer for measurement. The traditional Rogowski coil current transformer in this technology has advantages such as simple structure, no magnetic saturation problem, and wide current measurement range, and can realize large current measurement. However, due to process limitations, the traditional Rogowski coil current transformer is generally large in size, and it cannot guarantee uniform coil winding and equal cross-sectional area. Therefore, it is difficult to guarantee the consistency of parameters of the same batch of products, the anti-interference performance is poor, and the cost of precision winding of such a traditional Rogowski coil is high. Utility Model Content

[0006] The technical problem to be solved by this utility model is to overcome the shortcomings of the existing technology and provide a circuit breaker that can accurately measure fault currents that are much larger than the maximum protection setting current of the circuit breaker, thereby providing an accurate basis for the assessment of the electrical operating life of the circuit breaker.

[0007] The present invention specifically adopts the following technical solution to solve the above-mentioned technical problems:

[0008] A circuit breaker includes a current measuring unit and a life assessment unit for evaluating the remaining electrical operating life of the circuit breaker based on the current measurement data recorded by the current measuring unit. The current measuring unit includes a first current measuring circuit and a second current measuring circuit arranged in parallel. The first current measuring circuit is a current measuring circuit based on an iron core current transformer, and its current measurement value ICT is used as the current basis for determining the circuit breaker's protection operation. When ICT is within the linear measurement range of the iron core current transformer, ICT is recorded as the current current measurement data. The second current measuring circuit is a current measuring circuit based on a PCB Rogowski coil current transformer, and its current measurement value IRC is recorded as the current current measurement data when ICT is outside the linear measurement range of the iron core current transformer.

[0009] Furthermore, the iron core current transformer in the first current measurement circuit also serves as the self-generated power source for the circuit breaker.

[0010] Preferably, the second current measurement circuit includes a PCB Rogowski coil current transformer, an integrating amplifier circuit, and a voltage boosting circuit connected in sequence.

[0011] Preferably, the iron core current transformer used to measure the current of the same phase is tightly fitted and packaged with the PCB Rogowski coil transformer.

[0012] Preferably, the three PCB Rogowski coil current transformers used for measuring the three-phase current are arranged in parallel on the same PCB board.

[0013] Preferably, the other circuit components in the second current measurement circuit, except for the PCB Rogowski coil, are mounted on the same PCB board as the PCB Rogowski coil.

[0014] Compared with the prior art, the technical solution of this utility model has the following beneficial effects:

[0015] This invention leverages the complementary advantages of iron-core current transformers and PCB Rogowski coil current transformers in current measurement performance. Compared to traditional circuit breakers based on iron-core current transformers, it can accurately measure fault currents far exceeding the circuit breaker's maximum protection setting current. This enables the assessment and diagnosis of the circuit breaker's electrical operating life, facilitating users in locating line faults and analyzing the causes of circuit breaker tripping. Compared to circuit breaker solutions using traditional wound-rotor Rogowski coil current transformers, it offers advantages such as smaller size, better anti-interference performance, lower cost, better consistency, and ease of mass production. Attached Figure Description

[0016] Figure 1 This is a basic structural block diagram of the circuit breaker of this utility model;

[0017] Figure 2 This is a circuit block diagram of a current measurement circuit based on a PCB Rogowski coil transformer;

[0018] Figure 3 for Figure 2 A specific circuit structure diagram of the RC signal detection circuit;

[0019] Figure 4 This is a block diagram of another circuit structure for a current measurement circuit based on a PCB Rogowski coil transformer.

[0020] Figure 5 for Figure 4 A specific circuit structure diagram of the RC signal detection circuit;

[0021] Figure 6 This is an example diagram of a tightly integrated package of an iron-core current transformer and a PCB Rogowski coil transformer.

[0022] Figure 7 This is an example diagram showing three PCB Rogowski coil current transformers arranged in parallel on the same PCB board. Detailed Implementation

[0023] Traditional low-voltage circuit breakers suffer from nonlinear distortion due to high current saturation in their core current transformers, making it difficult to accurately measure large fault currents. They can generally only guarantee high measurement and protection accuracy within 1 to 4 times the rated current. Measuring larger currents requires correction based on the nonlinear curve of the transformer, thus reducing accuracy. Furthermore, the maximum measurable current is generally slightly greater than the maximum protection setting current, while the actual breaking current capacity of the circuit breaker may be much greater than its maximum protection setting current. This makes it difficult to assess the remaining electrical operating life of traditional low-voltage circuit breakers based on fault current, and it is also not conducive to accurately analyzing the cause of faults in the protected lines using fault current data.

[0024] The present invention specifically adopts the following technical solution to solve the above-mentioned technical problems:

[0025] A circuit breaker includes a current measuring unit and a life assessment unit for evaluating the remaining electrical operating life of the circuit breaker based on the current measurement data recorded by the current measuring unit. The current measuring unit includes a first current measuring circuit and a second current measuring circuit arranged in parallel. The first current measuring circuit is a current measuring circuit based on an iron core current transformer, and its current measurement value ICT is used as the current basis for determining the circuit breaker's protection operation. When ICT is within the linear measurement range of the iron core current transformer, ICT is recorded as the current current measurement data. The second current measuring circuit is a current measuring circuit based on a PCB Rogowski coil current transformer, and its current measurement value IRC is recorded as the current current measurement data when ICT is outside the linear measurement range of the iron core current transformer.

[0026] To facilitate public understanding, the technical solution of this utility model will be described in detail below through a specific embodiment and in conjunction with the accompanying drawings:

[0027] like Figure 1 As shown, the circuit breaker in this embodiment includes a core current transformer for self-generated power supply and current measurement, electronic components for detecting and analyzing fault current and issuing trip commands, and an actuator for disconnecting the fault current according to the trip commands issued by the electronic components. The electronic components include a CT signal detection circuit connected to the output of the core current transformer, a microprocessor unit for analyzing and judging the detection signals of the CT signal detection circuit and issuing trip signals, and a trip circuit for controlling the actuator to operate according to the trip signals issued by the microprocessor unit. Based on this, as... Figure 1 As shown, the circuit breaker also includes a PCB Rogowski coil current transformer for accurate measurement of large fault currents. An RC signal detection circuit connected to the output of the PCB Rogowski coil current transformer is added to the electronic components. The output of the RC signal detection circuit is connected to a microprocessor unit for accurate measurement of large fault currents. The core current transformer provides the current signal basis for determining the circuit breaker's protection operation and provides current measurement data within its linear measurement range. The PCB Rogowski coil current transformer provides current measurement data outside the linear measurement range of the core current transformer.

[0028] The microprocessor records the current measurement data as follows: It reads the pre-set upper limit of the linear measurement range of the iron core current transformer (ILM), and then obtains the current measurement value ICT from the iron core current transformer and the current measurement value IRC from the PCB Rogowski coil current transformer. When ICT is greater than the circuit breaker's set operating current, a trip signal is issued. The magnitude of ICT is compared with that of ILM. When ICT is less than or equal to ILM, ICT is recorded as a fault current; otherwise, IRC is recorded as a fault current.

[0029] The upper limit of the linear measurement range of the iron core current transformer can be freely set between 1 and 10 times the rated current of the circuit breaker, or determined based on the actual linear measurement range data of the iron core current transformer.

[0030] The RC signal detection circuit connected to the PCB Rogowski coil current transformer can be implemented using various existing technologies, such as through cascaded integrating amplifier circuits or voltage boosting circuits.

[0031] Figure 2 This illustrates one possible circuit block diagram, including an amplifier circuit, an integrator circuit, and a voltage boosting circuit connected in sequence. The output of the PCB Rogowski coil current transformer is connected to the amplifier circuit, and the output of the voltage boosting circuit is connected to the microprocessor unit. A specific implementation of this RC signal detection circuit is shown below. Figure 3 As shown, the first and second stages are an amplifier circuit and an integrator circuit, respectively, to amplify and integrate the output signal of the PCB Rogowski coil current transformer. Capacitor C1 is the integrating capacitor used to restore the phase of the Rogowski coil output signal. The third stage is a voltage boosting circuit, where capacitor C2 is a DC blocking capacitor used to cut off the bias voltage generated by the operational amplifier, the reference voltage Vref is used to boost the output signal voltage, thus facilitating A / D sampling by the microprocessor unit, and capacitor C3 is a filter capacitor used to remove high-frequency noise. In this RC signal detection circuit, the sequentially connected amplifier circuit, integrator circuit, and voltage boosting circuit enable the output signal to completely reconstruct the measured primary current waveform.

[0032] Figure 4 The diagram shows another circuit structure block diagram for an RC signal detection circuit, including an integrator circuit, an amplifier circuit, and a voltage boosting circuit connected in sequence. The output of the PCB Rogowski coil current transformer is connected to the integrator circuit, and the output of the voltage boosting circuit is connected to the microprocessor unit. Clearly, this embodiment is different from... Figure 2 The difference in the illustrated embodiment is that this embodiment first integrates and then amplifies the output signal of the PCB Rogowski coil current transformer, but the final effect is the same. A specific implementation circuit of the RC signal detection circuit in this embodiment is as follows: Figure 5 As shown.

[0033] To further reduce the size of components, the entire device can be made more compact through special structural design and packaging processes. For example, the iron core current transformer used to measure the current of the same phase can be tightly packaged with the PCB Rogowski coil transformer; or, three PCB Rogowski coil transformers used to measure the three-phase current can be arranged in parallel on the same PCB board; or, other circuit components in the second current measurement circuit, except for the PCB Rogowski coil, can be arranged on the same PCB board as the PCB Rogowski coil.

[0034] Figure 6 This illustration shows an example of a tightly integrated package of a core current transformer and a PCB Rogowski coil current transformer. The PCB Rogowski coil current transformer consists of two identical PCB Rogowski coil printed circuit boards. The core current transformer is wrapped with insulating tape and then further wrapped with insulating tape to form a combined current transformer. To accurately measure the fault current on each phase of the circuit breaker, one such combined current transformer is installed on each phase busbar.

[0035] For ease of production and manufacturing, it can also be like Figure 7 As shown, the PCB Rogowski coil current transformers corresponding to phases A, B, and C of the circuit breaker are arranged in parallel on the same printed circuit board in the form of PCB Rogowski coils. Other circuit components in the RC signal detection circuit are integrated onto this same printed circuit board, or connected to another printed circuit board containing the electronic components using a low-cost hard-wired connection. Alternatively, the PCB Rogowski coil current transformers corresponding to phases A, B, and C of the circuit breaker can be arranged on separate printed circuit boards in the form of PCB Rogowski coils, and then connected to another printed circuit board containing the electronic components using a low-cost hard-wired connection.

Claims

1. A circuit breaker, comprising a current measuring unit and a life assessment unit for evaluating the remaining electrical operating life of the circuit breaker based on current measurement data recorded by the current measuring unit; characterized in that, The current measurement unit includes a first current measurement circuit and a second current measurement circuit arranged in parallel. The first current measurement circuit is a current measurement circuit based on an iron core current transformer. Its current measurement value ICT is used as the current basis for determining the circuit breaker protection action. When ICT is within the linear measurement range of the iron core current transformer, ICT is recorded as the current measurement data. The second current measurement circuit is a current measurement circuit based on the PCB Rogowski coil transformer. Its current measurement value IRC is recorded as the current measurement data when the ICT is outside the linear measurement range of the iron core current transformer.

2. The circuit breaker as described in claim 1, characterized in that, The iron core current transformer in the first current measurement circuit also serves as the self-generated power source for the circuit breaker.

3. The circuit breaker as described in claim 1, characterized in that, The second current measurement circuit includes a PCB Rogowski coil current transformer, an integrating amplifier circuit, and a voltage boosting circuit connected in sequence.

4. The circuit breaker as described in claim 1, characterized in that, The iron-core current transformer used to measure the current of the same phase is tightly encapsulated with the PCB Rogowski coil transformer.

5. The circuit breaker as described in claim 1, characterized in that, Three PCB Rogowski coil current transformers for measuring three-phase current are arranged in parallel on the same PCB board.

6. The circuit breaker as described in claim 1, characterized in that, In the second current measurement circuit, all circuit components except the PCB Rogowski coil are mounted on the same PCB board as the PCB Rogowski coil.

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