Current and voltage combined transformer with calibration function

Abstract

The invention discloses a current and voltage combined transformer with a calibration function, which comprises a current transformer, a voltage transformer, a signal processing and sampling circuit, a calibration merging unit, a temperature compensation module and a capacitance and voltage indicator, and is characterized in that the current transformer is formed by uniformly winding enameled wires on an annular ultracrystalline iron core to form a metering winding; the two ends of the wire are connected with a bidirectional suppression transient diode and a current sampling resistor in parallel, the voltage transformer is formed by connecting a high-voltage capacitor and a bus sleeve in series for voltage division, a bus conducting rod is used as a power taking end, and signal conversion is achieved through electric field distribution of a coaxial cylindrical capacitor. Large current and high voltage are firstly converted into weak analog signals, after amplification conditioning, errors are eliminated through digital self-calibration compensation, finally, signals meeting the industrial standard are output, and the precision and reliability of power monitoring are effectively improved through the design.

Description

Technical Field

[0001] The present invention relates to the technical field of current and voltage combined mutual inductors, in particular to a current and voltage combined mutual inductor with a calibration function. Background Art

[0002] With the large-scale integration of new energy sources and the diversification of user-side loads, traditional ring main units (RMUs) face bottlenecks such as aging equipment, insufficient data collection accuracy, and delayed fault response. Furthermore, the transformation of distribution networks toward "digitalization + automation" requires sensors with real-time monitoring, intelligent diagnosis, and adaptive calibration capabilities to support rapid fault isolation (such as ground fault protection) and improve power supply reliability. Furthermore, RMUs are often deployed outdoors in confined spaces, facing challenges such as high humidity, dust, and electromagnetic interference. Traditional electromagnetic transformers are bulky and susceptible to ferromagnetic resonance. Their mechanical structure is prone to aging, leading to performance degradation. These sensors are unable to meet the urgent demand for high-precision, interference-resistant, and easily integrated sensing technologies required for intelligent distribution network upgrades.

[0003] Therefore, it is imperative to develop and manufacture new current sensors and voltage sensors in ring network cabinets, especially new current and voltage combined transformers with calibration functions. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, an embodiment of the present invention provides a current and voltage combined transformer with a calibration function. The technical problem to be solved is the technical shortcomings of traditional equipment in new energy access, adaptation to complex environments and digital collaboration, and provides support for the evolution of ring network cabinets into intelligent terminals with "status perception, fault isolation and electric energy metering".

[0005] To solve the above technical problems, the present invention provides the following technical solutions: a current and voltage combined transformer with calibration function, comprising a current transformer, a voltage transformer, a signal processing and sampling circuit, a calibration merging unit, a temperature compensation module, and a capacitance voltage indicator. The current transformer is formed by uniformly winding enameled wire on a toroidal ultrafine crystal iron core to form a metering winding, and a bidirectional transient suppression diode and a current sampling resistor are connected in parallel at both ends of the wire; The voltage transformer is composed of a high-voltage capacitor connected in series with a busbar bushing to divide the voltage, and uses the busbar conductive rod as the power supply terminal to achieve signal conversion through the electric field distribution of the coaxial cylindrical capacitor; The signal processing and sampling circuit includes an operational amplifier follower for isolating and processing the signals collected by the current transformer and the voltage transformer; The calibration merging unit has a built-in microcontroller unit and a D / A converter. The microcontroller unit has a built-in self-calibration algorithm, which calculates the compensation value based on the reference signal, converts the sampled signal into a dynamic compensation signal through the D / A converter, and then outputs a standard signal, which is transmitted to the intelligent electronic device. The temperature compensation module collects the ambient temperature in real time through the temperature sensor and transmits it to the microcontroller unit for correcting the temperature drift caused by temperature changes; Capacitor voltage indicator, used to detect device voltage status.

[0006] As a preferred solution of the current-voltage combined transformer with calibration function of the present invention, the coil of the current transformer is encapsulated in a metal shielding shell cast with epoxy resin; The current sampling resistors are connected in a two-series and two-parallel manner.

[0007] As a preferred solution of the current-voltage combined transformer with calibration function described in the present invention, the inner and outer conductors of the coaxial cylindrical capacitor of the voltage transformer form a uniform electric field distribution, and the conductor spacing and dielectric material thickness are adjusted to reduce the risk of partial discharge. Its voltage output interface is provided with an overvoltage, overcurrent and anti-reverse connection protection circuit consisting of a varistor, a self-recovery fuse and a rectifier diode.

[0008] As a preferred solution of the current-voltage combined transformer with calibration function described in the present invention, the calibration merging unit directly outputs the collected current signal through the 8P terminal, transmits the voltage signal to the analog amplifier circuit, and outputs it to the microcontroller unit after amplification, isolation and protection. The microcontroller unit performs signal compensation with reference to the reference voltage, and the compensation value is converted by D / A to output a standard signal.

[0009] As a preferred embodiment of the current-voltage combined transformer with calibration function of the present invention, the capacitor voltage indicator is connected to the operational amplifier follower via the relay on the acquisition board when powered on, amplifies the collected voltage signal, and outputs it to the capacitor voltage indicator after optical coupling isolation. When the power is off, the voltage divided by the bushing is directly output to the capacitor voltage indicator.

[0010] As a preferred solution of the current-voltage combined transformer with calibration function described in the present invention, the current transformer adopts a bushing-through-core structure, the secondary winding is wound by a toroidal ultra-microcrystalline iron core and multi-turn enameled wire, and is insulated by epoxy resin encapsulation. The primary conductor passes through the center of the sensor, and the secondary side senses a current signal reduced by the transformation ratio, which is output as an analog small voltage signal through the conversion unit.

[0011] As a preferred solution of the current-voltage combined transformer with calibration function described in the present invention, the voltage transformer is integrated into the busbar bushing, and the bushing has a built-in capacitor ring. The primary high-voltage signal is converted into a low-voltage signal through coaxial capacitor voltage division. The conductive rod conducts the grounding current into the ground. The low-voltage signal is processed by a bidirectional transient suppression diode and a resistor-capacitor voltage divider, and then amplified to 220mV by an operational amplifier.

[0012] As a preferred solution of the current-voltage combined transformer with calibration function described in the present invention, the output end of the analog amplifier circuit is electrically connected to the input end of the bidirectional transient suppression diode for anti-static and surge protection; the 24V power supply provides positive and negative 12V power to the op amp follower through an isolated power supply module and a linear regulator.

[0013] As a preferred solution of the current-voltage combined transformer with calibration function described in the present invention, when the microcontroller detects that the voltage calibration button is triggered, it automatically executes the calibration procedure, dynamically compensates the sampled signal, ensures that the output voltage is stable at 3.25 / √3V, and stores the compensation parameters in a non-volatile memory.

[0014] As a preferred solution of the current-voltage combined transformer with calibration function described in the present invention, a bidirectional transient suppression diode is connected in parallel at the output end of the secondary winding of the current transformer for overcurrent transient protection, and four current sampling resistors are connected, which are electrically connected in a two-series and two-parallel manner, and the current signal is converted into a voltage signal and then transmitted to the calibration merging unit.

[0015] By means of the above technical solution, the present invention provides a current-voltage combined transformer with a calibration function, which has at least the following beneficial effects: This combined transformer combines low-power coil sensing with high-voltage capacitor high-voltage electric field sensing technology, combined with D / A conversion technology, to achieve precise measurement of strong electrical signals through multi-technical collaboration. Its operating principle is to first convert high current and high voltage into weak analog signals, then amplify and condition them, eliminate errors through digital self-calibration compensation, and ultimately output a signal that meets industrial standards. This design effectively improves the accuracy and reliability of power monitoring.

[0016] 2. The combined mutual inductor adopts non-contact space electric field sensing technology, which has the advantages of simple and reliable insulation structure and stable performance.

[0017] 3. The combined transformer uses a low-power electronic sensor that passes through the core of the ring main unit. Compared with traditional power transformers, its output power is small, which is convenient for access to the intelligent distribution system and is in line with the current development trend of digitalization and intelligence of the power system.

[0018] 4. This combined mutual inductor has built-in digital calibration compensation, good linearity, strong anti-interference ability, and stable operation over a wide temperature range.

[0019] 5. Compared with traditional transformers, this combined transformer has a smaller space, smaller volume, lighter weight, lower manufacturing cost, simpler installation structure, and is easier to install and maintain.

[0020] 6. The combined transformer can realize visual monitoring of the live status and eliminate the risk of misjudgment of "false power outage" in the ring network cabinet. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application: Figure 1 It is a schematic diagram of the internal structure of the present invention.

[0022] Figure 2 It is a schematic diagram of the combined assembly of the present invention.

[0023] Figure 3 This is a circuit diagram of current signal acquisition and protection in the signal acquisition board of the present invention.

[0024] Figure 4 This is a circuit diagram of a dual CVI switch in the signal acquisition board of the present invention.

[0025] Figure 5 This is a circuit diagram of voltage sampling, operational amplifier amplification, and isolation protection in the signal acquisition board of the present invention.

[0026] Figure 6 This is a circuit diagram of the operation and disconnection of the driving relay in the signal acquisition board of the present invention.

[0027] Figure 7 This is a circuit diagram for calibrating the power supply in the merging unit of the present invention to stabilize the voltage to 15V and 5V outputs and supply power to the LED lamp.

[0028] Figure 8 This is a circuit diagram of a single motor minimum system and a program download interface in the calibration merging unit of the present invention.

[0029] Figure 9 This is a circuit diagram of amplifying the voltage sampling signal in the calibration merging unit through a dual-channel operational amplifier in the present invention.

[0030] Figure 10 This is a circuit diagram of the self-calibration measurement and signal compensation in the calibration merging unit of the present invention.

[0031] Figure 11 This is a circuit diagram of the external calibration button interface in the calibration merging unit of the present invention.

[0032] Figure 12 This is an interface circuit diagram between the signal acquisition board and the calibration merging unit in the calibration merging unit of the present invention.

[0033] Figure 1: 1. Bushing; 2. Current transformer; 3. Connection line between signal acquisition board and calibration merging unit; 4. Ground terminal of current transformer; 5. Capacitor voltage indicator; 6. Calibration merging unit; 7. Voltage port of signal acquisition board input from divided voltage in bushing; 8. Voltage line from signal acquisition board to CVI. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] like Figures 1-12 As shown, a current and voltage combined transformer with calibration function includes a current transformer, a voltage transformer, a signal processing and sampling circuit, a calibration merging unit, a temperature compensation module, and a capacitance voltage indicator. The current transformer adopts low-power coil sensing technology based on the principle of electromagnetic induction. The metering winding is formed by evenly winding enameled wire on a ring-shaped ultra-microcrystalline iron core. A bidirectional transient suppression diode (TVS) and a current sampling resistor are connected in parallel at both ends of the wire. The voltage transformer adopts high-voltage electric field sensing technology with coaxial voltage division. The voltage is divided by connecting a high-voltage capacitor in series with the busbar bushing. The busbar conductive rod is used as the power supply terminal, and signal conversion is achieved through the electric field distribution of the coaxial cylindrical capacitor. The signal processing and sampling circuit includes an op amp follower, which is used to isolate and process the signals collected by the current transformer and the voltage transformer; The signal processing circuit uses the OPA2197IDR operational amplifier to form an op amp follower, whose input impedance is as high as 10-12Ω and output impedance is lower than 100Ω, achieving impedance matching and isolation between the front and rear stage circuits.

[0036] The transfer function of the op amp follower is: ; Ensure that the signal is not distorted during transmission, such as Figure 3 As shown in , it is used for preliminary isolation of current and voltage sampling signals.

[0037] The calibration merging unit has a built-in microcontroller unit (MCU) and a D / A converter. The MCU has a built-in self-calibration algorithm that calculates the compensation value based on the reference signal. After the D / A converter converts the sampled signal into a dynamic compensation value, it outputs a standard signal and transmits it to the intelligent electronic device. The temperature compensation module collects the ambient temperature in real time through the temperature sensor and transmits it to the microcontroller unit (MCU) to correct the temperature drift caused by temperature changes; The temperature compensation module uses an NTC thermistor as a temperature sensor, and its resistance-temperature relationship is: ; in, , Thermistor and 10kΩ precision resistor form a voltage divider circuit, and the output voltage for: ; When the temperature changes, As the data changes, the microcontroller unit (MCU) collects the data through the ADC. And calculate the actual temperature.

[0038] The temperature drift compensation formula is: ; in, is the temperature drift coefficient (α=50ppm / ℃ for current transformer and α=80ppm / ℃ for voltage transformer), is the temperature change.

[0039] The microcontroller unit (MCU) calculates the compensation coefficient according to the real-time temperature and dynamically corrects the sampling signal.

[0040] Capacitor Voltage Indicator (CVI), used to detect device voltage status.

[0041] like Figures 3 to 6 As shown in the figure, in the current signal acquisition and protection circuit, the bidirectional TVS tubes D3 and D4 play the role of overcurrent protection and electrostatic and surge protection; the four resistors R4, R5, R6, and R7 are sampling resistors, and the two-series and two-parallel connection method improves the working power.

[0042] In the voltage sampling, op amp amplification, and isolation protection circuit, bidirectional TVS diode D5 is used to protect subsequent circuits from damage caused by high voltage (such as static electricity or surges), and resistor R10 acts as a current limiter. Resistors R11 and R16 and capacitors C23 and C24 form a resistor-capacitor voltage divider. U7 is a dual-channel operational amplifier that performs impedance transformation on the voltage sampling signal and isolates the signal. R16, R17, and C22 form a feedback network to set the amplification factor. D6 is a clamping diode that prevents overvoltage from damaging subsequent circuits.

[0043] In the circuit that drives the relay to work and disconnect, U5 is a quasi-16-bit single-chip microcomputer. When powered on, it outputs instructions to the relay driver chip U8, so that it controls the relay K1 to connect to the operational amplifier. When the power is off, C26, C27, C28, and C29 discharge, and the relay driver chip controls the relay to disconnect again.

[0044] like Figures 7-12 As shown, the sampled current signal is directly output through the lower board interface of the merging unit; The sampled voltage signal is amplified, isolated and protected by dual-channel operation and development components U3A, U3B, U7B and diode D2 before being output. If the calibration button is pressed, the output signal is fed back to the microcontroller U3, the compensation value is calculated, and then output to the D / A converters U10 and U14 to be converted into analog signals for feedback compensation of the voltage sampling signal.

[0045] In some examples, the current transformer coil is entirely encapsulated in a stainless steel shielding shell with a thickness of 1 mm, and the shielding shell is grounded through a grounding terminal to suppress external electromagnetic interference.

[0046] The epoxy resin potting material uses E-51 epoxy resin, and the dielectric strength after curing is ≥20kV / mm, ensuring the insulation reliability under the 10kV system.

[0047] In some examples, the inner and outer conductors of the coaxial cylindrical capacitor of the voltage transformer form a uniform electric field distribution. By adjusting the conductor spacing of the coaxial capacitor (adjustable from 5 to 20 mm) and the thickness of the dielectric material (1 to 3 mm), the electric field strength is controlled below 3 kV / mm, which is lower than the breakdown field strength of polytetrafluoroethylene (20 kV / mm).

[0048] The protection circuit of the voltage output interface consists of a varistor (10D471K), a resettable fuse (1A) and a rectifier diode (1N4007), which provides overvoltage, overcurrent and reverse connection protection.

[0049] In some examples, the calibration merging unit directly outputs the collected current signal through the 8P terminal, and the voltage signal is transmitted to the analog amplifier circuit, which is then output to the microcontroller unit (MCU) after amplification, isolation, and protection. The microcontroller unit (MCU) performs signal compensation with reference to the reference voltage, and the compensation value is converted into a standard signal through D / A conversion.

[0050] The calibration merging unit is based on the STC8H3K32S2 microcontroller. The current signal is fed directly into the ADC channel of the microcontroller via an 8P terminal block, while the voltage signal is processed by an analog amplifier circuit and fed into another ADC channel. The microcontroller has a built-in 12-bit ADC with a sampling rate of 100kSPS, meeting the real-time monitoring requirements of the power system.

[0051] In some examples, when the capacitor voltage indicator (CVI) is powered on, it is connected to an op amp follower through a relay on the acquisition board, amplifies the collected voltage signal, and outputs it to the capacitor voltage indicator after optical coupling isolation; When the power is off, the voltage divided by the bushing is directly output to the capacitor voltage indicator.

[0052] The capacitor voltage indicator includes domestic model (lighting voltage 3kV, capacitance 10nF) and foreign model (lighting voltage 3.5kV, capacitance 5nF), and the output voltage is switched by a double-pole double-throw switch.

[0053] When powered on, the 24V power supply is connected to the op amp follower through relay K1, amplifying the voltage signal to the lighting threshold of CVI: ; in, is the magnification factor.

[0054] When the power is off, the relay is disconnected and the divided voltage of the bushing is directly output to the capacitor voltage indicator, ensuring that the energized state can still be indicated in the power outage state.

[0055] In some examples, the current transformer adopts a bushing-through-core structure, the secondary winding is made of a toroidal ultra-microcrystalline iron core and multiple turns of enameled wire, and is insulated by epoxy resin potting. The primary conductor passes through the center of the sensor, and the secondary side senses a current signal reduced by the transformation ratio, which is output as an analog small voltage signal through the conversion unit.

[0056] The annular ultra-microcrystalline core has high magnetic permeability and low loss characteristics, ensuring efficient transfer of magnetic flux.

[0057] The secondary winding is made of 0.1mm diameter enameled wire wound evenly with 200 turns to form a metering winding. After winding is completed, the epoxy resin vacuum potting process is used to form an integral insulation structure between the winding and the iron core.

[0058] The primary conductor (such as a 10kV busbar) passes through the center hole of the transformer. According to the principle of electromagnetic induction, the expression of the induced electromotive force on the secondary side is: ; Where N is the number of turns of the secondary winding (200 turns), is the magnetic flux. When the magnetic flux changes As time changes, the current induced on the secondary side , the transformation ratio relationship is: ; Due to the number of turns of the primary winding , secondary turns , so the transformation ratio is 200:1.

[0059] In some examples, the voltage transformer is integrated into the busbar bushing, which has a built-in capacitor ring. The primary high-voltage signal is converted into a low-voltage signal through coaxial capacitor voltage division. The conductive rod conducts the grounding current into the ground. The low-voltage signal is processed by a bidirectional transient suppression diode and a resistor-capacitor voltage divider, and then amplified to 220mV by the OPA2197IDR operational amplifier.

[0060] The voltage transformer is integrated into the busbar bushing and uses a coaxial cylindrical capacitor voltage divider structure. The inner conductor is the busbar conductive rod, and the outer conductor is a ring-shaped capacitor screen. The space between the two is filled with polytetrafluoroethylene dielectric material (dielectric constant ε = 2.1). Based on the principle of electric field distribution, the capacitance calculation formula of the coaxial capacitor is: ; in, For capacitive screen length, is the inner conductor radius, is the outer conductor radius, and the capacitance is calculated as: ; Primary high voltage The voltage is divided by this capacitor and the secondary capacitor, and the voltage division ratio is: ; When the primary voltage is 10kV, the secondary output voltage ; In some examples, the output terminal of the analog amplifier circuit is electrically connected to the input terminal of a bidirectional transient voltage suppression diode (TVS) for anti-static and surge protection.

[0061] The voltage sampling signal is first suppressed by a bidirectional transient suppression diode to suppress the surge voltage, and then further reduced by a resistor-capacitor voltage divider.

[0062] The operational amplifier uses OPA2197IDR, and its amplification circuit is as follows Figure 5 As shown, the closed-loop gain is determined by the feedback resistor R16 and the input resistor R11: ; The 15V divided voltage signal is amplified to about 220mV (15V / 48≈312mV, the actual voltage is adjusted to 220mV due to the voltage divider network). The formula is: ; A bidirectional transient suppression diode is set at the output end of the analog amplifier circuit for anti-static protection to ensure signal stability.

[0063] The 24V power supply is converted to 5V through an isolated power supply module (B0505S-1W), and then outputs ±12V through linear regulators CJ79L12 and CJ78L12 respectively, providing stable power for the op amp follower.

[0064] The power supply filter circuit uses a 100μF electrolytic capacitor in parallel with a 0.1μF ceramic capacitor to suppress the ripple voltage to below 50mV.

[0065] In some examples, when the microcontroller detects that the voltage calibration button is triggered, it automatically executes a calibration procedure, dynamically compensates the sampled signal to ensure that the output voltage is stable at 3.25 / √3V, and stores the compensation parameters in a non-volatile memory.

[0066] The self-calibration algorithm is based on the least squares fitting error model, assuming that the relationship between the ideal output and the actual output is: ; in, is the gain coefficient, During the calibration process, the MCU first connects to the reference voltage source (2.5V) and collects the actual sampling value. , calculate the initial error: ; Then connect to another reference point (1.25V) and collect ,calculate: ; The final compensation formula is: ; When the calibration button is triggered, the MCU executes the above algorithm and and Stored in non-volatile memory.

[0067] The compensated digital signal is converted into an analog signal through a 12-bit D / A converter, and the output standard voltage is 3.25 / √3V (about 1.876V). The formula is: ; in, , For digital value (0-4095), when hour, .

[0068] Data transmission complies with the IEC62056-21 protocol, uses FT3 format encoding, and is output to intelligent electronic devices through the RS-485 interface.

[0069] In some examples, a bidirectional transient suppression diode is connected in parallel to the output end of the secondary winding of the current transformer for overcurrent transient protection, and four current sampling resistors are connected and electrically connected in a two-series and two-parallel manner to convert the current signal into a voltage signal and transmit it to the calibration merging unit.

[0070] When the induced current exceeds the rated value, the TVS quickly breaks down and limits the current, protecting the subsequent circuits. The sampling circuit uses four high-precision sampling resistors (CSR0204FTDV2R50, 2.5Ω±0.1%), connected in two series and two parallel. The total resistance is: ; This connection method increases the power capacity of a single resistor from 0.25W to 1W, meeting the needs of large current sampling. The current signal is converted into a voltage signal through the sampling resistor, and the formula is: ; When the secondary current When the output voltage .

[0071] The combined current and voltage transformer with calibration function provided by this invention integrates functional modules such as current sensing, voltage sensing, signal processing, calibration compensation, and status indication. It is suitable for power monitoring scenarios in ring main unit distribution networks. Its core operating principle is to achieve high current and high voltage signal conversion through low-power coil technology and coaxial capacitor voltage division technology, respectively. After signal conditioning, the microcontroller uses a self-calibration algorithm to eliminate errors, and finally outputs a signal that meets industrial standards.

[0072] It should be noted that, in this document, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0073] Furthermore, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0074] While the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions, and alterations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. Current and voltage combined transformer with calibration function, characterized by: include, The current transformer is made of enameled wire evenly wound on a toroidal ultra-microcrystalline iron core to form a metering winding, with a bidirectional transient suppression diode and a current sampling resistor connected in parallel at both ends of the wire; The voltage transformer is a voltage transformer that is connected in series with a high-voltage capacitor and a busbar bushing to divide the voltage. The busbar conductive rod is used as the power supply terminal, and the signal conversion is achieved through the electric field distribution of the coaxial cylindrical capacitor. Signal processing and sampling circuit, including an op amp follower, for isolating and processing the signals collected by the current transformer and the voltage transformer; A calibration merging unit has a built-in microcontroller unit and a D / A converter. The microcontroller unit has a built-in self-calibration algorithm, calculates a compensation value based on a reference signal, converts the sampled signal into a dynamic compensation value through the D / A converter, and then outputs a standard signal for transmission to the intelligent electronic device. The temperature compensation module collects the ambient temperature in real time through the temperature sensor and transmits it to the microcontroller unit to correct the temperature drift caused by temperature changes; Capacitor voltage indicator, used to detect device voltage status.

2. The current-voltage combined transformer with calibration function according to claim 1, characterized in that: The coil of the current transformer is encapsulated in a metal shielding shell.

3. The current-voltage combined transformer with calibration function according to claim 1, characterized in that: The inner and outer conductors of the coaxial cylindrical capacitor of the voltage transformer form a uniform electric field distribution, and the risk of partial discharge is reduced by adjusting the conductor spacing and the thickness of the dielectric material. Its voltage output interface is equipped with an overvoltage, overcurrent and anti-reverse connection protection circuit consisting of a varistor, a self-recovery fuse and a rectifier diode.

4. The current-voltage combined transformer with calibration function according to claim 1, characterized in that: The calibration merging unit directly outputs the collected current signal through the wiring terminal, and transmits the voltage signal to the analog amplifier circuit. After amplification, isolation and protection, it is output to the microcontroller unit. The microcontroller unit performs signal compensation with reference to the reference voltage, and the compensation value is converted by D / A to output the standard signal.

5. The current-voltage combined transformer with calibration function according to claim 1, characterized in that: In the capacitor voltage indicator, when powered on, the relay on the acquisition board is connected to the operational amplifier follower, the collected voltage signal is amplified and output to the capacitor voltage indicator after optical coupling isolation; When the power is off, the voltage divided by the bushing is directly output to the capacitor voltage indicator.

6. The current-voltage combined transformer with calibration function according to claim 2, characterized in that: The current transformer adopts a bushing-through-core structure. The secondary winding is made of a toroidal ultra-microcrystalline iron core and multiple turns of enameled wire, and is insulated by epoxy resin encapsulation. The primary conductor passes through the center of the sensor. The secondary side senses a current signal reduced by the transformation ratio, which is output as an analog small voltage signal through a conversion unit.

7. The current-voltage combined transformer with calibration function according to claim 1, characterized in that: The voltage transformer is integrated into the busbar bushing, which has a built-in capacitor ring. The primary high-voltage signal is converted into a low-voltage signal through coaxial capacitor voltage division. The conductive rod conducts the grounding current into the ground. The low-voltage signal is processed by a bidirectional transient suppression diode and a resistor-capacitor voltage divider, and then amplified to 220mV by an operational amplifier.

8. The current-voltage combined transformer with calibration function according to claim 4, characterized in that: The output end of the analog amplifier circuit is electrically connected to the input end of the bidirectional transient suppression diode for anti-static and surge protection.

9. The current-voltage combined transformer with calibration function according to claim 1, characterized in that: When the microcontroller detects that the voltage calibration button is triggered, it automatically executes the calibration procedure, dynamically compensates the sampling signal, and stores the compensation parameters in the non-volatile memory.

10. The current-voltage combined transformer with calibration function according to claim 1, characterized in that: A bidirectional transient suppression diode is connected in parallel to the output end of the secondary winding of the current transformer for overcurrent transient protection, and is connected to four current sampling resistors, which are electrically connected in a two-series and two-parallel manner to convert the current signal into a voltage signal and transmit it to the calibration merging unit.

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