A Pitt-level magnetic field detection sensor

Abstract

The present invention discloses a Pitt-level magnetic field detection sensor, including a magnetic field system and a sensing system, wherein the sensing system includes a magnetic sensitive part, a signal processing part and a shell part, wherein the magnetic field system is a Pitt magnetic field signal, wherein the magnetic field system is connected to the magnetic sensitive part in the sensing system, wherein the magnetic sensitive part is connected to the signal processing part, and wherein the shell part is located outside the magnetic sensitive part and the signal processing part. The present invention adopts the above-mentioned Pitt-level magnetic field detection sensor, and since the TMR sensor measures the magnetic field of the space, the installation of the TMR sensor does not need to be connected to the working circuit of the lightning arrester, and only needs to be installed close to the grounding bus, and the modulation and secondary demodulation methods are used, which is conducive to the detection of extremely weak magnetic field signals, and the use of multilayer Permalloy as a magnetic field shielding material, and the provision of a shell magnetic field shielding is conducive to the Pitt-level magnetic field measurement.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic detection, and in particular to a Pitt-level magnetic field detection sensor. Background Art

[0002] Metal zinc oxide arrester is one of the key equipment of power equipment. The resistive current flowing through the arrester is an important indicator to measure the insulation degree of the arrester. Through real-time online monitoring of the total current, resistive current, capacitive current, number of lightning strikes and lightning strike time of the arrester, the insulation condition of high-voltage electrical equipment can be monitored in real time; at the same time, by analyzing the monitoring data, the potential faults of the metal zinc oxide arrester can be discovered in time and important data basis can be provided for status maintenance, which provides a strong and reliable guarantee for the safe, reliable, stable and economical operation of the power system, and provides reliable equipment insulation information and scientific maintenance basis for operation and maintenance personnel, so as to reduce the occurrence of accidents, extend the maintenance interval, reduce the number and time of power outage maintenance, and improve equipment utilization and overall economic benefits.

[0003] At present, there are several main means to monitor the leakage current of zinc oxide lightning arresters: special zinc oxide lightning arrester tester. This product is a special instrument for detecting the electrical performance of zinc oxide lightning arresters. It is suitable for energized or power-off detection of zinc oxide lightning arresters of various voltage levels, so as to timely discover dangerous defects such as moisture inside the equipment insulation and valve aging. It can measure the total current, resistive current and its harmonics, power frequency reference voltage and its harmonics, active power and phase difference of zinc oxide lightning arresters. Using digital waveform analysis technology, harmonic analysis and digital filtering and other software anti-interference methods make the measurement results accurate and stable, and can accurately analyze the content of fundamental wave and 3rd to 7th harmonics, and can overcome the influence of phase-to-phase interference, and correctly measure the resistive current of side phase lightning arresters with an accuracy of tens of microamperes.

[0004] Clamp-on ammeter. This product uses the principle of electromagnetic coupling and is often used for large current detection. Currently, the detection accuracy of mature products can reach the milliampere level. However, the arrester leakage current usually requires that the current of 50 microamperes can be detected, and the higher the accuracy, the better. Therefore, clamp-on ammeters are generally not used for high-precision current measurement.

[0005] Lightning arrester leakage current monitor. This product is installed in an intrusive manner and needs to occupy the power outage indicator. The circuit uses the coil mutual inductance method to convert the current into a high voltage, and then rectifies the high voltage and passes it into the coil to affect the pointer change. This method works stably and has high stability. It can measure 10 microampere level current, and the circuit is simple and low cost.

[0006] With regard to the detection of lightning arrester leakage current, it is currently difficult to achieve high-precision, non-invasive installation measurement methods.

[0007] The sensitivity of magnetic field measurement of tunnel magnetoresistive sensors has been getting better and better in recent years. Currently, the most sensitive TMR sensors in commercial use have reached the level of petascale magnetic field measurement. With the help of signal processing circuits, weak magnetic signals can be measured very well, which is very suitable for measuring the leakage current of lightning arresters. Summary of the invention

[0008] The purpose of the present invention is to provide a pitt-level magnetic field detection sensor. Since the TMR sensor measures the magnetic field in space, the installation of the TMR sensor does not need to be connected to the working circuit of the lightning arrester, and it only needs to be installed close to the grounding bus. The modulation and secondary demodulation methods are used, which is beneficial to the detection of extremely weak magnetic field signals. Multilayer Permalloy is used as a magnetic field shielding material, and the outer shell magnetic field shielding is set to facilitate pitt-level magnetic field measurement.

[0009] The present invention provides a Pitt-level magnetic field detection sensor, including a magnetic field system and a sensing system, wherein the sensing system includes a magnetic sensitive part, a signal processing part and a shell part, the magnetic field system is a Pitt magnetic field signal, the magnetic field system is connected to the magnetic sensitive part in the sensing system, the magnetic sensitive part is connected to the signal processing part, and the shell part is located on the outside of the magnetic sensitive part and the signal processing part.

[0010] Preferably, the magnetic sensitive part includes a modulation module and a magnetic sensitive element, the modulation module generates a carrier wave to the magnetic sensitive element, and the magnetic sensitive element senses the Pitt magnetic field signal of the external magnetic field system as a modulation signal.

[0011] Preferably, the signal processing part includes a first op amp filter, a first demodulation module, a second op amp filter, a second demodulation module, an MCU microcontroller and a LORA module, the first op amp filter is connected to the first demodulation module, the first demodulation module is connected to the second op amp filter, the second op amp filter is connected to the second demodulation module, the second demodulation module is connected to the MCU microcontroller, and the MCU microcontroller is connected to the LORA module.

[0012] Preferably, the magnetic sensitive element is a TMR sensor.

[0013] Preferably, the shielding material in the shell portion is wound with multiple layers of Permalloy.

[0014] Preferably, the modulation module generates a carrier frequency of 5.08 kHz.

[0015] Preferably, the first demodulation module uses AD630 as a core chip, and the second demodulation module uses AD8310 as a core chip.

[0016] Therefore, the present invention adopts the above-mentioned Pitt-level magnetic field detection sensor. Since the TMR sensor measures the magnetic field in space, the installation of the TMR sensor does not need to be connected to the arrester working circuit, and it only needs to be installed close to the grounding bus. The use of modulation and secondary demodulation is conducive to the detection of extremely weak magnetic field signals. Multi-layer Permalloy is used as a magnetic field shielding material. By setting the outer shell magnetic field shielding, it is conducive to Pitt-level magnetic field measurement.

[0017] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is an overall schematic diagram of a Pitt-level magnetic field detection sensor of the present invention;

[0019] Figure 2 A schematic diagram of the simulated working logic of a Pitt-level magnetic field detection sensor of the present invention;

[0020] Figure 3 A schematic diagram of the self-magnetic field noise of a magnetic sensitive element of a Pitt-level magnetic field detection sensor of the present invention;

[0021] Figure 4 A schematic diagram of a modulation signal generated by a 50 Hz signal to be measured by a Pitt-level magnetic field detection sensor of the present invention;

[0022] Figure 5 A schematic diagram of a spectrum diagram of a TMR sensor direct output signal of a Pitt-level magnetic field detection sensor of the present invention;

[0023] Figure 6 This is a schematic diagram of a 50Hz signal spectrum output by a TMR sensor of a pitt-level magnetic field detection sensor of the present invention. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0025] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0026] The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprises" and similar terms mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0027] Embodiment 1

[0028] like Figure 1-6 As shown, the present invention is a Pitt-level magnetic field detection sensor, including a magnetic field system and a sensing system. The magnetic field system is a Pitt magnetic field signal. The sensing system includes a magnetic sensitive part, a signal processing part and a shell part. The magnetic field system is connected to the magnetic sensitive part in the sensing system, and the magnetic sensitive part is connected to the signal processing part. The amplitude modulated signal measured by the magnetic sensitive part is sent to the signal processing part, which can ensure that the sensing system can accurately and reliably sense and convert the magnetic field changes in the environment into useful electrical signals.

[0029] The outer shell is located outside the magnetic sensitive part and the signal processing part. The function of the outer shell is to protect the magnetic sensitive part and the signal processing part from the influence of the external environment, ensuring that the sensor can still work normally in various harsh environments and maintain its performance and accuracy. The shielding material in the outer shell is wound with multiple layers of Permalloy. Completing the environmental magnetic field shielding can further enhance the magnetic shielding effect of the outer shell, reduce the interference of the magnetic field part on the internal components of the sensor system, and thus improve the accuracy and stability of the sensor system.

[0030] The magnetic sensitive part includes a modulation module and a magnetic sensitive element. The modulation module generates a carrier to the magnetic sensitive element. The modulation module contains an oscillator or signal generator for generating a carrier signal of a specific frequency and amplitude.

[0031] The modulation module transmits the generated carrier signal to the magnetic sensitive element through the circuit connection. The magnetic sensitive element senses the pitot magnetic field signal of the external magnetic field system as the modulation signal. The magnetic sensitive element adopts TMR sensor, and TMR has broken through the pitot-level magnetic field measurement. With the help of signal processing circuit, weak magnetic signals can be measured well. It is very suitable for measuring the leakage current of lightning arresters. By modulating the sensor system, the operating frequency of the sensor system is modulated to a higher frequency. At this time, the noise of the sensor system will be reduced several times, which means that the sensor system may measure the pitot-level magnetic field signal when working at this frequency.

[0032] The signal processing part includes a first op amp filter, a first demodulation module, a second op amp filter, a second demodulation module, an MCU microcontroller and a LORA module. The first op amp filter is connected to the first demodulation module. The first op amp filter receives the electrical signal from the TMR sensor and is used to remove noise and interference in the signal. At the same time, the signal may also be amplified to ensure that the signal has sufficient amplitude for subsequent processing. The demodulation module extracts detailed information about the Pitt magnetic field signal from the filtered signal.

[0033] The first demodulation module is connected to the second operational amplifier filter to further remove noise and interference in the signal, further improve the quality of the signal, and enhance the accuracy and reliability of the signal.

[0034] The second op amp filter is connected to the second demodulation module, which further extracts detailed information about the Pitt magnetic field signal from the filtered signal. The second demodulation module is connected to the MCU microcontroller, which is responsible for processing these demodulated signals and performing necessary calculations and control tasks. The MCU microcontroller is connected to the LORA module. The first demodulation module uses AD630 as the core chip, and the second demodulation module uses AD8310 as the core chip. AD630 and AD8310 as core chips have high accuracy and stability, and are suitable for precision signal processing with a wide dynamic range.

[0035] The modulated signal is firstly amplified and narrow-band filtered by the first op amp filter to further reduce the noise on the entire spectrum. The center frequency of the first narrow-band filter in the first op amp filter is set to the operating frequency after the TMR sensor is modulated. Then the modulated signal is input into the first demodulation module for demodulation, and the demodulated modulated signal should be the power frequency. At this time, the modulated signal is sent to the second op amp filter, the amplitude is modulated appropriately, and the center frequency of the second narrow-band filter is set to the power frequency. Then the modulated signal is sent to the second demodulation module for demodulation. The demodulated DC quantity is positively correlated with the amplitude of the power frequency signal to be measured. Finally, the data is encoded by the MCU microcontroller and sent to the node through the LORA module to complete the current information transmission.

[0036] The analog working logic of the sensing system: The modulation module uses an oscillation source, which is generated by NE555 and becomes a sine wave (carrier) through filtering; the carrier frequency is about 5.08 kHz. The magnetic sensitive element uses a full-bridge TMR sensor, and the modulation module generates a carrier for the magnetic sensitive element.

[0037] The output of the full-bridge TMR sensor in the magnetic sensitive element is sent to the first op amp for filtering. The first op amp filtering amplification circuit, the center frequency of the first narrowband filter in the first op amp filtering is about 50Hz. The first op amp filtering is sent to the first demodulation module, the first demodulation module uses the first demodulator, the first demodulator uses AD630 as the core chip, the first demodulation module sends the signal to the second op amp for filtering, the bandwidth of the second narrowband filter in the second op amp filtering needs to be slightly wider than the bandwidth of the first narrowband filter, about 48Hz-52Hz. Since the power frequency is often not an absolute 50Hz, there will be a fluctuation of 1-2Hz; the second op amp filtering sends the signal to the second demodulation module, the second demodulation module uses the second demodulator, the second demodulator uses AD8310 for demodulation, the DC signal obtained after demodulation contains the background signal, and the back-end zero adjustment amplification needs to be performed according to the zero input response.

[0038] Apply 5mA current and calculate that the magnetic field at the sensor system is about 10uT. The spectrum of the direct output signal of the TMR sensor is as follows: Figure 5 As shown in Figure 2, the signal-to-noise ratio of a 50Hz signal is about 70dB. The spectrum of the 50Hz signal output by the TMR sensor is shown in Figure 2. Figure 6 As shown in the figure, the signal-to-noise ratio is about 84dB, and the sensor sensitivity is improved by 14dB compared with the direct measurement method. The minimum measurable magnetic field is reduced from 3nT to 600pT.

[0039] Use MCU microcontroller to control LORA module to send and receive signals. You can easily configure module parameters, send and receive data. Work stably in complex environments and achieve reliable data transmission. The operating frequency used by LORA module is 470MHz.

[0040] Therefore, the present invention adopts the above-mentioned Pitt-level magnetic field detection sensor. Since the TMR sensor measures the magnetic field in space, the installation of the TMR sensor does not need to be connected to the arrester working circuit, and it only needs to be installed close to the grounding bus. The use of modulation and secondary demodulation is conducive to the detection of extremely weak magnetic field signals. Multi-layer Permalloy is used as a magnetic field shielding material. By setting the outer shell magnetic field shielding, it is conducive to Pitt-level magnetic field measurement.

[0041] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A Pitt-level magnetic field detection sensor, characterized in that: It includes a magnetic field system and a sensor system, the sensor system includes a magnetic sensitive part, a signal processing part and a shell part, the magnetic field system is a Pitt magnetic field signal, the magnetic field system is connected to the magnetic sensitive part in the sensor system, the magnetic sensitive part is connected to the signal processing part, and the shell part is located on the outside of the magnetic sensitive part and the signal processing part; the signal processing part includes a first operational amplifier filter, a first demodulation module, a second operational amplifier filter, a second demodulation module, an MCU microcontroller and a LORA module, the first operational amplifier filter is connected to the first demodulation module, the first demodulation module is connected to the second operational amplifier filter, the second operational amplifier filter is connected to the second demodulation module, the second demodulation module is connected to the MCU microcontroller, and the MCU microcontroller is connected to the LORA module.

2. A Pitot-level magnetic field detection sensor according to claim 1, characterized in that: The magnetic sensitive part includes a modulation module and a magnetic sensitive element. The modulation module generates a carrier wave to the magnetic sensitive element. The magnetic sensitive element senses the Pitt magnetic field signal of the external magnetic field system as a modulation signal.

3. A Pitt-level magnetic field detection sensor according to claim 2, characterized in that: The magnetic sensitive element adopts a TMR sensor.

4. A Pitt-level magnetic field detection sensor according to claim 1, characterized in that: The shielding material in the shell part is wound with multiple layers of Permalloy.

5. A Pitt-level magnetic field detection sensor according to claim 2, characterized in that: The modulation module generates a carrier frequency of 5.08 kHz.

6. A Pitt-level magnetic field detection sensor according to claim 3, characterized in that: The first demodulation module uses AD630 as a core chip, and the second demodulation module uses AD8310 as a core chip.

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