Double range digitizing circuit of AC sensor for distribution network
By using a dual-range digital circuit for AC sensors used in power distribution networks, combined with synchronous sampling of current and voltage signals, the accuracy problem in judging small current grounding faults is solved, and high-precision fault detection is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHEJIANG HUACAI TECH CO LTD
- Filing Date
- 2025-05-30
- Publication Date
- 2026-07-07
AI Technical Summary
In existing technologies, it is difficult to accurately identify small-current grounding faults in line fault detection. Traditional solutions have insufficient accuracy in current and voltage acquisition, which cannot meet the requirements for line loss calculation.
A dual-range digital circuit for AC sensors used in power distribution networks is adopted. Large-range and small-range detection are performed by current generating device and voltage generating device respectively. Synchronous sampling is performed by analog-to-digital conversion circuit, and signal processing and encoding output are performed by processor circuit.
It achieves high-precision sampling of small current signals, avoids phase difference at sampling time, meets the judgment requirements of small current grounding faults in distribution networks, and improves the accuracy of fault detection.
Smart Images
Figure CN224471740U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power distribution, and in particular to a dual-range digital circuit for an AC sensor used in power distribution networks. Background Technology
[0002] With the increasing demands of power user management, the timeliness requirements for handling line faults are becoming higher and higher. Among all faults, low-current grounding faults are the most difficult to detect and determine. In order to solve this problem, a zero-sequence voltage-zero-sequence current transient waveform algorithm is proposed for fault judgment.
[0003] In traditional solutions, voltage and current are used as the criteria for fault diagnosis. Fault currents and voltages are usually large currents and large voltages, which leads to an overemphasis on the accuracy of large current and large voltage acquisitions. At the same time, the relatively low accuracy of small current and small voltage measurements does not meet the accuracy requirements for line loss calculation. Summary of the Invention
[0004] This application provides a dual-range digital circuit for an AC sensor used in power distribution networks to address the problem of insufficient accuracy in line loss calculation in related technologies.
[0005] In a first aspect, embodiments of this application provide a dual-range digital circuit for an AC sensor used in a power distribution network, comprising:
[0006] Current generating device, voltage generating device, analog-to-digital conversion circuit, and processor circuit;
[0007] The first current output terminal of the current generating device is electrically connected to the first input terminal of the processor circuit, and the processor circuit performs large-range detection on the current signal generated by the current generating device.
[0008] The second current output terminal of the current generating device is electrically connected to the first input terminal of the analog-to-digital conversion circuit. The current signal is detected in a small range in the analog-to-digital conversion circuit. The output terminal of the analog-to-digital conversion circuit is electrically connected to the second input terminal of the processor circuit.
[0009] The voltage output terminal of the voltage generating device is electrically connected to the second input terminal of the analog-to-digital converter circuit, and the output terminal of the analog-to-digital converter circuit is electrically connected to the second input terminal of the processor circuit.
[0010] The output terminal of the processor circuit is electrically connected to the encoding output circuit.
[0011] A first operational amplifier circuit is provided between the current generating device and the analog-to-digital conversion circuit, and a second operational amplifier circuit is provided between the voltage generating device and the analog-to-digital conversion circuit.
[0012] Optionally, the current signal includes a protective current signal with a first range and a measuring current signal with a second range.
[0013] Optional, including:
[0014] The protective current signal enters the built-in analog-to-digital sensor in the processor circuit via the first current output terminal for analog-to-digital conversion.
[0015] Optional, including:
[0016] The current signal used for measurement and the voltage signal generated by the voltage generating device enter the analog-to-digital conversion circuit for synchronous analog-to-digital conversion.
[0017] Optional, including:
[0018] The current signal includes three-phase current and zero-sequence current, and the voltage signal includes three-phase voltage and zero-sequence voltage.
[0019] Optionally, the encoding output circuit includes:
[0020] The encoding logic circuit is used to obtain communication frame data from the output of the processor circuit and convert the communication frame data into Manchester code.
[0021] A capacitive isolation circuit is used to transmit the Manchester code to the receiving device via an RS485 circuit.
[0022] Optional, including:
[0023] The processor circuit is electrically connected to the code memory and data memory via an I2C interface.
[0024] Optionally, it also includes a remote control device, wherein the remote control signal generated by the remote control device is electrically connected to the third input terminal of the processor circuit.
[0025] Optionally, the remote control device includes:
[0026] A remote control acquisition circuit is used to collect remote control signals and integrate the remote control signals;
[0027] An optocoupler isolation circuit is used to isolate interference from the integrated remote control signal and input the obtained remote control signal to the third input terminal of the processor circuit.
[0028] Optionally, it may also include a power supply module that supplies power to the various devices and circuits.
[0029] The dual-range digital circuit for an AC sensor used in a power distribution network provided in this application embodiment has at least the following technical effects.
[0030] The current signal is sampled using a combination of large and small ranges to address the accuracy issue of low-current sampling. Simultaneously, the current and voltage signals are sampled and converted synchronously in the analog-to-digital converter circuit to avoid phase differences caused by the order of sampling, thus meeting the requirements for judging low-current grounding faults in distribution networks.
[0031] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description
[0032] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:
[0033] Figure 1 This is a simplified block diagram of a dual-range digital circuit for an AC sensor used in a power distribution network, provided according to an embodiment of this application.
[0034] Figure 2 This is a complete module schematic diagram of a dual-range digital circuit for an AC sensor used in a power distribution network, provided according to an embodiment of this application. Detailed Implementation
[0035] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.
[0036] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.
[0037] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.
[0038] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms “a,” “an,” “an,” “the,” and similar words used in this application do not indicate quantity limitation and may indicate singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or devices. The terms “connected,” “linked,” “coupled,” and similar words used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following objects are in an "or" relationship. The terms "first," "second," and "third" used in this application are merely to distinguish similar objects and do not represent a specific ordering of the objects.
[0039] This application provides a dual-range digital circuit for an AC sensor used in power distribution networks, such as... Figure 1 As shown, it includes four main modules: a current generating device, a voltage generating device, an analog-to-digital conversion circuit, and a processor circuit. A first operational amplifier circuit is provided between the current generating device and the analog-to-digital conversion circuit, and a second operational amplifier circuit is provided between the voltage generating device and the analog-to-digital conversion circuit.
[0040] In terms of the direction of electrical signal transmission, the current generating device generates a current signal, which includes a protective current signal with a first range and a measuring current signal with a second range.
[0041] The protective current signal flows out from the first current output terminal of the current generating device and flows into the first input terminal of the processor circuit, where it undergoes large-range detection. The measuring current signal flows out from the second current output terminal of the current generating device and flows into the first input terminal of the analog-to-digital converter circuit, where it undergoes small-range detection. The voltage signal flows out from the voltage output terminal of the voltage generating device and flows into the second input terminal of the analog-to-digital converter circuit, where it undergoes analog-to-digital conversion.
[0042] Based on the above, the protection current signal enters the processor circuit via the first current output terminal of the current generating device and the first input terminal of the processor circuit, where it undergoes large-range sampling and detection. The measurement current signal enters the analog-to-digital converter (ADC) circuit via the second current output terminal of the current generating device and the first input terminal of the ADC circuit, where it undergoes small-range sampling and detection. This combination of large and small range sampling addresses the issue of low-current sampling accuracy. Simultaneously, the ADC circuit synchronously samples and converts the current and voltage signals to avoid phase differences caused by different sampling times, thus meeting the requirements for judging low-current grounding faults in the distribution network.
[0043] Specifically, the processor circuit in this embodiment employs 12 independent synchronous analog-to-digital conversion channels, with 4 channels for acquiring current signals for measurement, 4 channels for acquiring current signals for protection, and 4 channels for acquiring voltage signals. The current and voltage signals for measurement are input to the analog-to-digital conversion circuit, which uses 8 channels for synchronous analog-to-digital conversion. The current channels include 4 measurement channels and 4 protection channels. The measurement channels acquire the low end of the current signal (i.e., small current signal), and the protection channels acquire the high end of the same current signal (i.e., large current signal). Each current quantity is sampled using two channels: one for measurement current sampling and the other for protection current sampling. This dual-range sampling method addresses the accuracy issue of small current sampling.
[0044] The protective current signal is sent to the processor circuit, where a built-in AD converter converts it into a digital signal. The two digital signals are then spliced together to achieve large-range current detection. The measuring current and voltage signals are sent to an analog-to-digital converter for processing, yielding corresponding digital signals, which are then sent to the processor circuit.
[0045] The current signal consists of three-phase currents Ia / Ib / Ic and zero-sequence current Io. After being converted into a voltage signal by a sampling resistor, the current signal is connected to the first operational amplifier circuit. After passing through the first operational amplifier circuit, the current signal is split into two ranges: a measurement current signal and a protection current signal. The measurement current signal is input to the analog-to-digital converter circuit with a built-in 8-channel analog-to-digital converter chip, while the protection current signal is input to the processor circuit with a built-in analog-to-digital converter.
[0046] Considering the insufficient strength of the current input signal for measurement, a differential amplifier circuit is used for amplification, while a lower-cost single-ended amplifier circuit is used for the current input signal for protection. Although the current signals for measurement and protection originate from the same source, their output amplitudes differ, with the current signal for measurement exhibiting a larger amplitude.
[0047] The protection current signal is input to the processor's built-in analog-to-digital converter (ADC) using a 4-channel scanning conversion method. While this scanning method introduces a phase difference, it is sufficient as there are no phase angle accuracy requirements for the protection current. The built-in ADC offers 12-bit conversion accuracy, and the protection current has a dynamic range of 20 times, providing adequate conversion precision.
[0048] The voltage signals are three-phase voltages Ua / Ub / Uc and zero-sequence voltage Uo. After the voltage signals are divided by voltage dividers to obtain appropriate voltage values, they are connected to the second operational amplifier circuit. The output voltage signals are input to an 8-channel analog-to-digital converter chip, which is used for both voltage signals and current signals for measurement.
[0049] Furthermore, the reason for using dual-range current sampling is that the protection device requires the measurement current to have an accuracy of 0.5S class, that is, an accuracy better than 0.5% for 1%Ir to 120%Ir (Ir is the rated current, and the error limit for 1%Ir is 1.5%), and the protection current to have an accuracy of 5P20, that is, an accuracy better than 5% for 120%Ir to 2000%Ir. The combined measurement and protection current ranges are 1% to 2000%, or 2000 times. Using a 16-bit analog-to-digital converter chip cannot meet the requirement of achieving 0.5S class accuracy in 1%Ir current measurement under 2000 times dynamic range.
[0050] The protection device requires the voltage measurement accuracy to be 0.5 class, that is, the accuracy of 20%Ur to 120%Ur is better than 0.5% (Ur is the rated voltage), and the protection voltage accuracy to be 3P, that is, the accuracy of 2%Ur to 20%Ur and 120%Ur to 300%Ur is better than 3%. The range of the combined measurement current signal and the protection voltage signal is 2% to 300%, that is, the amplitude is 150 times. The 16-bit analog-to-digital converter chip can fully meet the sampling accuracy requirements. Therefore, the voltage sampling adopts a single-range method.
[0051] In analog-to-digital conversion circuits, analog-to-digital conversion is synchronous, ensuring that phase voltages and currents, as well as zero-sequence voltages and currents, do not experience phase differences due to the timing of the analog-to-digital conversion. This ensures the accuracy of power calculations using phase voltages and currents, and the accuracy of determining whether a fault is within or outside the fault boundary using zero-sequence voltages and currents.
[0052] like Figure 2 As shown, the dual-range digital circuit for the AC sensor used in the distribution network provided in this embodiment further includes the following modules:
[0053] After the analog-to-digital conversion circuit and the processor circuit complete the analog-to-digital conversion in sequence, the processor circuit transmits the obtained signal to the encoding output circuit through the SPI interface.
[0054] The encoding output circuit includes an encoding logic circuit and a capacitive isolation circuit. The former is used to acquire communication frame data from the processor circuit output and convert the communication frame data into Manchester code; the latter is used to send the Manchester code to the receiving device via an RS485 circuit. The acquired voltage, current, and telemetry quantities are assembled into communication frames by the processor according to the FT3 protocol and then output to the encoding circuit through the SPI port. The encoding circuit encodes the data into Manchester code. The SPI port, in conjunction with the specially designed encoding circuit, completes the Manchester encoding, minimizing the complexity of the software and hardware.
[0055] The processor circuitry connects to the code memory via an SPI interface and to the data memory via an I2C interface. The code memory stores the program code that the processor runs, while the data memory stores configuration parameters and data that needs to be recorded during operation.
[0056] Optionally, a remote control device is also included, wherein the remote control signal generated by the remote control device is electrically connected to the third input terminal of the processor circuit. The remote control device includes a remote control acquisition circuit and an optocoupler isolation circuit. The former is used to collect and integrate the remote control signals, while the latter is used to isolate interference from the integrated remote control signals and input the obtained remote control signal to the third input terminal of the processor circuit. The communication acquisition circuit uses a high-speed communication chip and uses a capacitive isolation circuit instead of the commonly used optocoupler communication.
[0057] Optionally, it may also include a power supply module that supplies power to the various devices and circuits.
[0058] The encoded signal is sent to the RS485 circuit via a high-speed capacitive isolation circuit, and then transmitted to the receiving device. One isolated power supply line powers the RS485 circuit. The processor receives four remote signaling signals; to ensure device safety and interference resistance, optocoupler isolation circuits are used, and one isolated power supply line powers the remote signaling acquisition circuit.
[0059] The power supply module provides power to the processor circuit, analog-to-digital converter circuit, code memory, data memory, and encoding logic circuit. The function of the operational amplifier circuit power supply is to generate the positive and negative power required for the operational amplifier to operate.
[0060] Actual test results: The phase difference between the converted current signal and voltage signal is less than 1 minute. The error of the current signal at 1% Ir is approximately 0.5%, which is a large margin compared to the 1.5% margin required for 1% Ir under the 0.5S accuracy standard. The error of the voltage signal at 2% Ur is approximately 0.5%, which is also a large margin compared to the 3P accuracy standard.
[0061] It should be noted that the dual-range digital circuit of the AC sensor for power distribution networks provided in this embodiment is used to implement the above-described embodiments, and will not be repeated as already described. As used above, the terms "module," "unit," "subunit," etc., can refer to a combination of software and / or hardware that performs a predetermined function. Although the apparatus described in the above embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.
[0062] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0063] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A dual-range digital circuit for an AC sensor used in power distribution networks, characterized in that, include: Current generating device, voltage generating device, analog-to-digital conversion circuit, and processor circuit; The first current output terminal of the current generating device is electrically connected to the first input terminal of the processor circuit, and the processor circuit performs large-range detection on the current signal generated by the current generating device. The second current output terminal of the current generating device is electrically connected to the first input terminal of the analog-to-digital conversion circuit. The current signal is detected in a small range in the analog-to-digital conversion circuit. The output terminal of the analog-to-digital conversion circuit is electrically connected to the second input terminal of the processor circuit. The voltage output terminal of the voltage generating device is electrically connected to the second input terminal of the analog-to-digital converter circuit. The output terminal of the processor circuit is electrically connected to the encoding output circuit. A first operational amplifier circuit is provided between the current generating device and the analog-to-digital conversion circuit, and a second operational amplifier circuit is provided between the voltage generating device and the analog-to-digital conversion circuit.
2. The dual-range digital circuit for AC sensors used in power distribution networks according to claim 1, characterized in that, include: The current signal includes a protective current signal with a first range and a measuring current signal with a second range.
3. The dual-range digital circuit for AC sensors used in power distribution networks according to claim 2, characterized in that, include: The protective current signal enters the built-in analog-to-digital sensor in the processor circuit via the first current output terminal for analog-to-digital conversion.
4. The dual-range digital circuit for an AC sensor used in power distribution networks according to claim 2, characterized in that, include: The current signal used for measurement and the voltage signal generated by the voltage generating device enter the analog-to-digital conversion circuit for synchronous analog-to-digital conversion.
5. The dual-range digital circuit for an AC sensor used in power distribution networks according to claim 4, characterized in that, include: The current signal includes three-phase current and zero-sequence current, and the voltage signal includes three-phase voltage and zero-sequence voltage.
6. The dual-range digital circuit for an AC sensor used in power distribution networks according to claim 1, characterized in that, The encoding output circuit includes: The encoding logic circuit is used to obtain communication frame data from the output of the processor circuit and convert the communication frame data into Manchester code. A capacitive isolation circuit is used to transmit the Manchester code to the receiving device via an RS485 circuit.
7. The dual-range digital circuit for an AC sensor used in power distribution networks according to claim 1, characterized in that, include: The processor circuit is electrically connected to the code memory and data memory via an I2C interface.
8. The dual-range digital circuit for an AC sensor used in power distribution networks according to claim 1, characterized in that, It also includes a remote control device, wherein the remote control signal generated by the remote control device is electrically connected to the third input terminal of the processor circuit.
9. The dual-range digital circuit for an AC sensor used in power distribution networks according to claim 8, characterized in that, The remote control device includes: A remote control acquisition circuit is used to collect remote control signals and integrate the remote control signals; An optocoupler isolation circuit is used to isolate interference from the integrated remote control signal and input the obtained remote control signal to the third input terminal of the processor circuit.
10. The dual-range digital circuit for an AC sensor used in a distribution network according to any one of claims 1 to 9, characterized in that, It also includes power supply modules that supply power to various devices and circuits.