Electric signal sampling circuit, device and system of ring net cabinet digital unit

Abstract

The application relates to an electric signal sampling circuit, device and system related to a ring main unit digital unit, which comprises an electric signal sampling module containing a mutual inductor composed of a high magnetic permeability metal shielding shell and a transient characteristic magnetic core, which is used for collecting phase voltage of a power distribution network system and sending the phase voltage to a differential buffer operational amplifier module, and collecting phase current of the power distribution network and sending the phase current to a full differential gain operational amplifier module; the differential buffer operational amplifier module is used for buffering, impedance matching and filtering processing of the phase voltage, generating a voltage signal, and sending the voltage signal to an analog-digital conversion module; the full differential gain operational amplifier module is used for gain adjustment and phase angle compensation processing of the phase current and zero sequence current, generating a current signal, and sending the current signal to the analog-digital conversion module; and the analog-digital conversion module is used for converting the voltage signal and the current signal into digital signals and sending the digital signals to an external control unit. Through the sampling circuit, high-quality electric signals can be collected.

Description

Technical Field

[0001] This application relates to the field of power system sampling and control technology, and in particular to electrical signal sampling circuits, devices and systems for digital units of ring main units. Background Technology

[0002] Currently, voltage and current sampling circuits widely used in 10kV distribution network systems are mostly based on traditional electromagnetic induction principles. Their sensors typically use ordinary magnetic core materials and have simple shielding structures, making them susceptible to noise in environments with strong electromagnetic interference, especially exhibiting significant distortion in the acquisition of weak signals. Furthermore, conventional magnetic core sensors have poor overload capacity, making it difficult to capture transient fault characteristics. In addition, existing sampling circuits suffer from insufficient impedance matching design between the sensor and subsequent conditioning circuits, leading to reflections and attenuation during signal transmission, affecting signal transmission accuracy and resulting in poor signal quality. For these reasons, traditional sampling circuits, limited by signal quality, lack accuracy in judging complex operating conditions such as intermittent faults and high-resistance grounding, thus resulting in a high fault misjudgment rate. Utility Model Content

[0003] This application provides an electrical signal sampling circuit, device, and system for a ring main unit digital unit, so as to at least solve the problem of poor electrical signal quality acquired by traditional power distribution network sampling circuits in related technologies.

[0004] In a first aspect, this application provides an electrical signal sampling circuit for a digital unit of a ring main unit, comprising: The electrical signal sampling module includes a current transformer consisting of a high-permeability metal shielded shell and a transient characteristic magnetic core, used to collect the phase voltage of the distribution network system and send it to the differential buffer operational amplifier module, and to collect the phase current of the distribution network and send it to the fully differential gain operational amplifier module. The differential buffer operational amplifier module is used to buffer, impedance match and filter the phase voltage, generate a voltage signal and send the voltage signal to the analog-to-digital converter module; The fully differential gain operational amplifier module is used to perform gain adjustment and phase angle compensation processing on the phase current and zero-sequence current, generate a current signal, and send the current signal to the analog-to-digital converter module; An analog-to-digital converter module is used to convert the voltage and current signals into digital signals and send them to an external control unit.

[0005] Preferably, the current transformer includes a voltage sampling current transformer and a current sampling current transformer; wherein, The input terminal of the voltage sampling transformer is connected to the field sensor via a connecting cable, and the output terminal is connected to the differential buffer operational amplifier module for acquiring phase voltage. The input terminal of the current sampling transformer is connected to the field sensor via the connecting cable, and the output terminal is connected to the fully differential gain operational amplifier module for acquiring phase current.

[0006] Preferably, the differential buffer operational amplifier module includes a differential buffer, a first filtering unit, and a second filtering unit; wherein, The first input terminal of the differential buffer is connected to the positive output terminal of the voltage sampling transformer, and the second input terminal is connected to the negative output terminal of the voltage sampling transformer; the first filtering unit is connected between the first output terminal of the differential buffer and the analog-to-digital converter module; the second filtering unit is connected between the second output terminal of the differential buffer and the analog-to-digital converter module.

[0007] Preferably, the differential buffer includes a first operational amplifier and a second operational amplifier, and the first and second operational amplifiers are configured in differential mode; wherein, The input terminal of the first operational amplifier is used as the first input terminal of the differential buffer, and the output terminal of the first operational amplifier is used as the first output terminal of the differential buffer; the input terminal of the second operational amplifier is used as the second input terminal of the differential buffer, and the output terminal of the second operational amplifier is used as the second output terminal of the differential buffer.

[0008] Preferably, the fully differential gain operational amplifier module includes a third operational amplifier, a first resistor, a second resistor, a first feedback unit, a second feedback unit, a third filter unit, and a fourth filter unit; wherein, The first input terminal of the third operational amplifier is connected to the positive output terminal of the current sampling transformer, and the second input terminal is connected to the negative output terminal of the current sampling transformer; the first resistor is connected between the first input terminal of the third operational amplifier and digital ground, and the second resistor is connected between the second input terminal of the third operational amplifier and digital ground; the first feedback unit is connected between the first input terminal and the first output terminal of the third operational amplifier; the second feedback unit is connected between the second input terminal and the second output terminal of the third operational amplifier; the third filtering unit is connected between the first output terminal of the third operational amplifier and the analog-to-digital converter module; and the fourth filtering unit is connected between the second output terminal of the third operational amplifier and the analog-to-digital converter module.

[0009] Preferably, the analog-to-digital conversion module includes a first analog-to-digital converter, an MCU unit containing a second analog-to-digital converter, and an FT3 encoding unit; The voltage sampling terminal of the first analog-to-digital converter (ADC) is connected to the output terminal of the differential buffer operational amplifier module; the current sampling terminal of the first ADC is connected to the output terminal of the fully differential gain operational amplifier module; the output terminal of the first ADC is connected to the input terminal of the MCU unit; the output terminal of the MCU unit is connected to the input terminal of the FT3 encoding unit; and the output terminal of the FT3 encoding unit is connected to an external control unit via an RS485 communication line. The second ADC is connected to the output terminal of the current sampling transformer. The first analog-to-digital converter is used to convert the received voltage and current signals into measurement digital signals. The second analog-to-digital converter is used to sample the protection current signal and convert it into a protection digital signal. The MCU unit is used to process the measurement digital signal and the protection digital signal. The FT3 encoding unit is used to encode the processed measurement digital signal and the protection digital signal and upload it to the external control unit.

[0010] Preferably, the transient characteristic magnetic core is a high permeability nickel-zinc ferrite magnetic core; the high permeability metal shielding shell is a 1J79 permalloy material shielding layer.

[0011] Secondly, this application provides an electrical signal sampling device for a digital unit of a ring main unit, including a metal protective housing and an electrical signal sampling circuit of the digital unit of the ring main unit as described in any of the above claims; wherein, the metal protective housing is provided with a sensor unit interface, the electrical signal sampling circuit is integrated and packaged in the metal protective housing, and the signal sampling circuit is connected to a field sensor and an external control unit through the sensor unit interface.

[0012] Preferably, the metal protective housing is an aluminum alloy housing with an IP67 protection rating, and both the inner and outer surfaces of the aluminum alloy housing are treated with a conductive oxidation process; the sensor unit interface uses a 360° shielded aviation plug.

[0013] Thirdly, this application provides an electrical signal sampling system for a digital unit of a ring main unit, including a control unit, a field sensor, and an electrical signal sampling circuit for the digital unit of the ring main unit as described in any of the preceding claims; The field sensor is installed in the power distribution network system to collect the phase voltage and phase current of the power distribution network and send them to the electrical signal sampling circuit. The output of the electrical signal sampling circuit is connected to the input of the control unit and is used to convert the phase voltage and phase current into electrical signals and send them to the control unit.

[0014] The electrical signal sampling circuit, device, and system of the ring main unit digital unit provided in this application have at least the following technical advantages: This application improves the signal anti-interference capability by using a current transformer composed of a high-permeability metal shielded shell and a transient characteristic magnetic core, solving the problems of traditional sampling circuits being susceptible to electromagnetic noise interference, leading to distortion of weak signals and insufficient transient characteristics. Furthermore, it completes impedance matching, gain compensation, and filtering of the electrical signal through a differential buffer operational amplifier module and a fully differential gain operational amplifier module, thereby solving the problem of impedance mismatch between the sensor and subsequent circuits affecting signal transmission accuracy. Finally, it converts the electrical signal into a digital signal through an analog-to-digital converter module, ensuring data integrity. In summary, this application constructs a sampling circuit for a ring main unit using an electrical signal sampling module, a differential buffer operational amplifier module, a fully differential gain operational amplifier module, and an analog-to-digital converter module, thereby acquiring high-quality electrical signals, further reducing the fault misjudgment rate, and improving the accuracy of data analysis.

[0015] 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

[0016] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a structural block diagram of the electrical signal sampling circuit of the digital unit of the ring main unit in one embodiment of this application; Figure 2 This is a circuit diagram of the electrical signal sampling circuit of the digital unit of the ring main unit in one embodiment of this application; Figure 3 This is a structural block diagram of the electrical signal sampling system of the digital unit of the ring main unit in one embodiment of this application. Detailed Implementation

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] Existing fault diagnosis technologies for power distribution networks have the following shortcomings: 1. Weak anti-interference capability: Traditional sampling circuits are susceptible to electromagnetic noise interference, leading to distortion of weak signals; 2. Impedance mismatch: Impedance mismatch between the sensor and subsequent circuitry affects signal transmission accuracy; 3. Insufficient transient characteristics: Conventional magnetic core sensors have poor overload capacity and are difficult to capture transient fault characteristics; 4. High fault misjudgment rate: Due to the poor quality of the sampled signal, the accuracy of judgment on complex operating conditions such as intermittent faults and high-impedance grounding is insufficient.

[0022] Based on the above, this application provides an electrical signal sampling circuit, device, and system for a ring main unit's digital unit.

[0023] In a first aspect, embodiments of this application provide an electrical signal sampling circuit for a digital unit of a ring main unit. Figure 1 This is a structural diagram of the electrical signal sampling circuit.

[0024] refer to Figure 1 The electrical signal sampling circuit of this application includes: The electrical signal sampling module includes a current transformer consisting of a high-permeability metal shielded shell and a transient characteristic magnetic core, used to collect the phase voltage of the distribution network system and send it to the differential buffer operational amplifier module, and to collect the phase current of the distribution network and send it to the fully differential gain operational amplifier module. The differential buffer operational amplifier module is used to buffer, impedance match and filter the phase voltage, generate a voltage signal and send the voltage signal to the analog-to-digital converter module; The fully differential gain operational amplifier module is used to perform gain adjustment and phase angle compensation processing on the phase current and zero-sequence current, generate a current signal, and send the current signal to the analog-to-digital converter module; An analog-to-digital converter module is used to convert the voltage and current signals into digital signals and send them to an external control unit.

[0025] This embodiment proposes a fully shielded high-precision sampling circuit system, employing a three-stage signal processing architecture. Specifically, the electrical signal sampling module is the first-stage passive transmitter, using a precision sensor with a high-permeability metal shielding shell and a transient characteristic magnetic core to achieve anti-interference and high overload ratio signal acquisition; the differential buffer operational amplifier module and the fully differential gain operational amplifier module are the second-stage active conditioning, completing impedance matching, gain compensation, and filtering through the differential buffer operational amplifier (for the voltage loop) and the fully differential gain operational amplifier (for the current loop); the analog-to-digital conversion module is the third-stage analog-to-digital converter, ensuring data integrity through digital-to-analog conversion.

[0026] In one embodiment, reference Figure 2This embodiment uses one phase (A / B / C phase) as an example for illustration. The current transformer includes a voltage sampling transformer (voltage loop PT) and a current sampling transformer (current loop CT). The input terminal of the voltage sampling transformer is connected to a field sensor via a connecting cable, and the output terminal is connected to the differential buffer operational amplifier module for acquiring phase voltage (Uin+, ​​Uin-). The input terminal of the current sampling transformer is connected to a field sensor via the connecting cable, and the output terminal is connected to the fully differential gain operational amplifier module for acquiring phase current (Lin+, Lin-).

[0027] In a preferred embodiment, the sensor employs a precision voltage and current sensor with a high-permeability nickel-zinc ferrite core (initial permeability ≥ 5000), possessing an overload capacity of 20 times its rated value. The outer shell is shielded with a 1J79 permalloy material (thickness ≥ 0.2 mm). For signal input, the phase voltage, phase current, and zero-sequence current combined differential signals from the sensor are directly connected to the AC input connector on the aluminum alloy housing of the sensing unit via a 7-core shielded aviation cable, achieving full shielding protection for signal transmission.

[0028] Continue to refer to Figure 2 The differential buffer operational amplifier module in this embodiment includes a differential buffer (precision buffer), a first filtering unit, and a second filtering unit. The first input terminal of the differential buffer is connected to the positive output terminal of the voltage sampling transformer, and the second input terminal is connected to the negative output terminal of the voltage sampling transformer. The first filtering unit is connected between the first output terminal of the differential buffer and the analog-to-digital converter module. The second filtering unit is connected between the second output terminal of the differential buffer and the analog-to-digital converter module. More specifically, the first filtering unit includes a third resistor R3 and a first capacitor C1, and the second filtering unit includes a fourth resistor R4 and a second capacitor C2; the junction between the first capacitor C1 and the second capacitor C2 is connected to digital ground.

[0029] In this embodiment, the precision buffer uses a precision operational amplifier SGM8249-4 (8MHz bandwidth), arranged in pairs to form a differential buffer, serving as a conduit for signal buffering, impedance matching, and filtering. Specifically, the differential buffer includes a first operational amplifier U1 and a second operational amplifier U2, configured in differential mode. The input terminal of the first operational amplifier U1 serves as the first input terminal and the output terminal of the first operational amplifier U1 serves as the first output terminal of the differential buffer; the input terminal of the second operational amplifier U2 serves as the second input terminal and the output terminal of the second operational amplifier U2 serves as the second output terminal of the differential buffer.

[0030] Continue to refer to Figure 2 Continue to refer to this embodiment Figure 2 The fully differential gain operational amplifier module of this embodiment includes a third operational amplifier U3, a first resistor R1, a second resistor R2, a first feedback unit, a second feedback unit, a third filter unit, and a fourth filter unit. Specifically, the first input terminal of the third operational amplifier U3 is connected to the positive output terminal of the current sampling transformer, and the second input terminal is connected to the negative output terminal of the current sampling transformer; the first resistor R1 is connected between the first input terminal of the third operational amplifier U3 and digital ground, and the second resistor R2 is connected between the second input terminal of the third operational amplifier U3 and digital ground; the first feedback unit is connected between the first input terminal and the first output terminal of the third operational amplifier U3; the second feedback unit is connected between the second input terminal and the second output terminal of the third operational amplifier U3; the third filter unit is connected between the first output terminal of the third operational amplifier U3 and the analog-to-digital converter module; and the fourth filter unit is connected between the second output terminal of the third operational amplifier U3 and the analog-to-digital converter module.

[0031] More specifically, the third filtering unit includes a fifth resistor R5 and a third capacitor C3, and the fourth filtering unit includes a sixth resistor R6 and a fourth capacitor C4. The connection point between the third capacitor C3 and the fourth capacitor C4 is connected to digital ground. The first feedback unit includes a seventh resistor R7 and a fifth capacitor C5 connected in parallel, and the second feedback unit includes an eighth resistor R8 and a sixth capacitor C6 connected in parallel. Preferably, this embodiment uses a true differential gain operational amplifier (such as a low-power, 60MHz bandwidth, wide power supply voltage range fully differential amplifier) ​​to achieve gain adjustment and phase compensation.

[0032] Continue to refer to Figure 2 The analog-to-digital conversion module in this embodiment includes a first analog-to-digital converter, an MCU unit containing a second analog-to-digital converter, and an FT3 encoding unit; The first analog-to-digital converter (ADC) has its voltage sampling terminal connected to the output terminal of the differential buffer operational amplifier module, its current sampling terminal connected to the output terminal of the fully differential gain operational amplifier module, its output terminal connected to the input terminal of the MCU unit, its output terminal connected to the input terminal of the FT3 encoding unit, and its output terminal connected to an external control unit via an RS485 communication line. The second ADC is connected to the output terminal of the current sampling transformer. Specifically, the first ADC converts the received voltage and current signals into measurement digital signals, the second ADC samples the protection current signal and converts it into a protection digital signal, the MCU unit processes the measurement and protection digital signals, and the FT3 encoding unit encodes the processed measurement and protection digital signals and uploads them to the external control unit.

[0033] In a preferred embodiment, the electrical signal sampling circuit is integrated and packaged within a metal protective housing. The signal sampling circuit is connected to a field sensor and an external control unit via a sensor unit interface on the housing. The metal protective housing is an IP67-rated aluminum alloy housing, and both the inner and outer surfaces of the aluminum alloy housing are treated with a conductive anodizing process. The sensor unit interface uses a 360° shielded aviation connector.

[0034] Specifically, the first digital-to-analog converter (DAC) of this application is a measurement channel AD converter, employing a 16-bit SAR-AD converter (AD7606BSTZ, sampling rate 200KSPS) to receive the conditioned voltage and current signals of the measurement channel; the second DAC is a protection channel AD converter, employing an on-chip 12-bit AD converter (MIMXRT1061CVL5) to synchronously sample the protection current signal with a sampling period of 100μs. The communication interface with the control unit adopts RS485, transmitting data to the control unit at a baud rate of 5Mbps and CRC check.

[0035] In terms of data processing, the MCU achieves data synchronization through hardware-triggered synchronous AD sampling, with a timestamp accuracy of ±1μs; the control unit uses wavelet transform (DB4 basis function) to extract transient features and combines SVM algorithm to classify fault types to achieve fault assessment; based on the assessment results, the system links up and controls the circuit breaker to perform load switching through the spring-loaded mechanism, with a response time of <20ms.

[0036] During the testing of the electrical signal sampling circuit, the test conditions were set as follows: a single-phase ground fault in a 10kV distribution network (grounding resistance 500Ω); the test results obtained were: transient current capture error <2%, fault judgment accuracy 98.7%, which is 32% higher than the traditional solution.

[0037] In summary, the electrical signal sampling circuit provided in this application, applied to a 10kV power distribution network, solves the problems of inaccurate fault diagnosis caused by factors such as susceptibility to interference with weak signals, impedance mismatch in the sampling circuit, and poor transient characteristics. This application employs a fully shielded structure design to combat environmental interference. The input signal is transmitted as a first-stage passive signal transducer via a high-permeability metal shielded shell and a high-overload-ratio precision voltage and current sensor with a magnetic core possessing good transient characteristics. Subsequently, a high-performance precision differential buffer operational amplifier (voltage loop) and a low-temperature drift differential gain operational amplifier (current loop) are cascaded for impedance matching and gain / phase angle compensation, followed by filtering for active second-stage signal conditioning. Finally, the signals are connected to a high-performance 16-bit successive approximation AD for measurement and an on-chip AD for protection within the MCU. The sampled data is collected in real-time by the MCU and then synchronously sent to the control unit for analysis and processing via a high-speed, low-error-rate RS-485 port. Therefore, the sampling circuit of this invention can effectively compensate for the deficiencies of traditional sampling circuits and significantly improve the accuracy of fault diagnosis and load switching.

[0038] Secondly, this application provides an electrical signal sampling device for a digital unit of a ring main unit, including a metal protective housing and an electrical signal sampling circuit for the digital unit of the ring main unit as described in any of the preceding embodiments; wherein, the metal protective housing is provided with a sensor unit interface, the electrical signal sampling circuit is integrated and packaged within the metal protective housing, and the signal sampling circuit is connected to a field sensor and an external control unit through the sensor unit interface. A schematic diagram of some interfaces on the metal protective housing of this embodiment is shown below. Figure 3 For example, A / B / C phase sampling input interfaces, FT3 sampling output interfaces, and DBG spare ports are set up. The A / B / C phase sampling input interfaces are connected to external sensors (i.e., sensors installed at the distribution network site) to receive three-phase sampling current (phase current) and three-phase sampling voltage (phase voltage). The FT3 sampling output interface is connected to an external control unit to encode the received electrical signals into uplink data and send them to the control unit.

[0039] Preferably, the metal protective housing is an aluminum alloy housing with an IP67 protection rating, and both the inner and outer surfaces of the aluminum alloy housing are treated with a conductive oxidation process; the sensor unit interface uses a 360° shielded aviation plug.

[0040] Preferably, the metal shielding shell and metal protective housing of the voltage and current transformers are grounded at a single point (grounding resistance < 0.1Ω).

[0041] This embodiment utilizes a 360° shielded aviation connector cable combined with an IP67-rated metal housing for full shielding and interference prevention, effectively blocking environmental electromagnetic interference. Furthermore, regarding signal input, the phase voltage, phase current, and zero-sequence current combined differential signals from external sensors are directly connected to the AC input aviation connector on the aluminum alloy housing of the sensing unit via a 7-core shielded aviation connector cable, achieving full shielding protection throughout signal transmission.

[0042] Preferably, in one embodiment of this application, the housing structure is optimized, that is, the inner and outer surfaces of the IP67 protection-rated aluminum alloy housing (thickness 5.3mm) are treated with conductive oxidation process to ensure reliable grounding shielding effect, and the aviation plug adopts a 360° shielding layer (shielding effectiveness ≥60dB).

[0043] Thirdly, one embodiment of this application provides an electrical signal sampling system for a digital unit of a ring main unit, including a control unit, a field sensor, and an electrical signal sampling circuit for the digital unit of the ring main unit as described in any of the preceding embodiments. See details. Figure 3 The field sensors are installed in the power distribution network system to collect the three-phase voltage and three-phase current of the power distribution network and send them to the electrical signal sampling circuit through the sensor unit interface; the output terminal of the electrical signal sampling circuit is connected to the input terminal of the control unit to convert the three-phase voltage and three-phase current into electrical signals and send them to the control unit.

[0044] 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.

[0045] 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 utility model 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. An electrical signal sampling circuit for a digital unit of a ring main unit, characterized in that, include: The electrical signal sampling module includes a current transformer consisting of a high-permeability metal shielded shell and a transient characteristic magnetic core, used to collect the phase voltage of the distribution network system and send it to the differential buffer operational amplifier module, and to collect the phase current of the distribution network and send it to the fully differential gain operational amplifier module. The differential buffer operational amplifier module is used to buffer, impedance match and filter the phase voltage, generate a voltage signal and send the voltage signal to the analog-to-digital converter module; The fully differential gain operational amplifier module is used to perform gain adjustment and phase angle compensation processing on the phase current and zero-sequence current, generate a current signal, and send the current signal to the analog-to-digital converter module; An analog-to-digital converter module is used to convert the voltage and current signals into digital signals and send them to an external control unit.

2. The electrical signal sampling circuit according to claim 1, characterized in that, The current transformer includes a voltage sampling current transformer and a current sampling current transformer; wherein... The input terminal of the voltage sampling transformer is connected to the field sensor via a connecting cable, and the output terminal is connected to the differential buffer operational amplifier module for acquiring phase voltage. The input terminal of the current sampling transformer is connected to the field sensor via the connecting cable, and the output terminal is connected to the fully differential gain operational amplifier module for acquiring phase current.

3. The electrical signal sampling circuit according to claim 2, characterized in that, The differential buffer operational amplifier module includes a differential buffer, a first filtering unit, and a second filtering unit; wherein... The first input terminal of the differential buffer is connected to the positive output terminal of the voltage sampling transformer, and the second input terminal is connected to the negative output terminal of the voltage sampling transformer; the first filtering unit is connected between the first output terminal of the differential buffer and the analog-to-digital converter module; the second filtering unit is connected between the second output terminal of the differential buffer and the analog-to-digital converter module.

4. The electrical signal sampling circuit according to claim 3, characterized in that, The differential buffer includes a first operational amplifier and a second operational amplifier, and the first and second operational amplifiers are configured in differential mode; wherein... The input terminal of the first operational amplifier is used as the first input terminal of the differential buffer, and the output terminal of the first operational amplifier is used as the first output terminal of the differential buffer; the input terminal of the second operational amplifier is used as the second input terminal of the differential buffer, and the output terminal of the second operational amplifier is used as the second output terminal of the differential buffer.

5. The electrical signal sampling circuit according to claim 2, characterized in that, The fully differential gain operational amplifier module includes a third operational amplifier, a first resistor, a second resistor, a first feedback unit, a second feedback unit, a third filter unit, and a fourth filter unit; wherein, The first input terminal of the third operational amplifier is connected to the positive output terminal of the current sampling transformer, and the second input terminal is connected to the negative output terminal of the current sampling transformer; the first resistor is connected between the first input terminal of the third operational amplifier and digital ground, and the second resistor is connected between the second input terminal of the third operational amplifier and digital ground; the first feedback unit is connected between the first input terminal and the first output terminal of the third operational amplifier; the second feedback unit is connected between the second input terminal and the second output terminal of the third operational amplifier; the third filtering unit is connected between the first output terminal of the third operational amplifier and the analog-to-digital converter module; and the fourth filtering unit is connected between the second output terminal of the third operational amplifier and the analog-to-digital converter module.

6. The electrical signal sampling circuit according to claim 2, characterized in that, The analog-to-digital conversion module includes a first analog-to-digital converter, an MCU unit containing a second analog-to-digital converter, and an FT3 encoding unit; The voltage sampling terminal of the first analog-to-digital converter (ADC) is connected to the output terminal of the differential buffer operational amplifier module; the current sampling terminal of the first ADC is connected to the output terminal of the fully differential gain operational amplifier module; the output terminal of the first ADC is connected to the input terminal of the MCU unit; the output terminal of the MCU unit is connected to the input terminal of the FT3 encoding unit; and the output terminal of the FT3 encoding unit is connected to an external control unit via an RS485 communication line. The second ADC is connected to the output terminal of the current sampling transformer. The first analog-to-digital converter is used to convert the received voltage and current signals into measurement digital signals. The second analog-to-digital converter is used to sample the protection current signal and convert it into a protection digital signal. The MCU unit is used to process the measurement digital signal and the protection digital signal. The FT3 encoding unit is used to encode the processed measurement digital signal and the protection digital signal and upload it to the external control unit.

7. The electrical signal sampling circuit according to claim 1, characterized in that, The transient characteristic magnetic core is a high permeability nickel-zinc ferrite magnetic core; the high permeability metal shielding shell is a 1J79 permalloy material shielding layer.

8. An electrical signal sampling device for a digital unit of a ring main unit, characterized in that, The device includes a metal protective housing and an electrical signal sampling circuit for the digital unit of the ring main unit as described in any one of claims 1-7; wherein the metal protective housing is provided with a sensor unit interface, the electrical signal sampling circuit is integrated and encapsulated within the metal protective housing, and the signal sampling circuit is connected to a field sensor and an external control unit through the sensor unit interface.

9. The electrical signal sampling device according to claim 8, characterized in that, The metal protective housing is made of aluminum alloy with an IP67 protection rating, and both the inner and outer surfaces of the aluminum alloy housing are treated with conductive oxidation process; the sensor unit interface uses a 360° shielded aviation plug.

10. An electrical signal sampling system for a digital unit of a ring main unit, characterized in that, Includes a control unit, field sensors, and an electrical signal sampling circuit for the digital unit of the ring main unit as described in any one of claims 1-7; The field sensor is installed in the power distribution network system to collect the phase voltage and phase current of the power distribution network and send them to the electrical signal sampling circuit. The output of the electrical signal sampling circuit is connected to the input of the control unit and is used to convert the phase voltage and phase current into electrical signals and send them to the control unit.

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