Grounding resistance on-line monitor

Abstract

The utility model discloses a grounding resistance online monitor, which relates to the field of monitoring equipment and comprises a central processing module, an LCD (liquid crystal display) display module, a communication module, a grounding acquisition module, a power management module and an analog-to-digital conversion module, the output end of the grounding acquisition module is connected to the input end of the analog-to-digital conversion module, and the output end of the analog-to-digital conversion module is respectively connected to the central processing module and the grounding acquisition module; the grounding acquisition module is provided with a first acquisition end P and a second acquisition end C. The power management module is connected with the grounding acquisition module to supply power to the whole device. According to the utility model, the numerical value of the grounding resistance can be regularly recorded and automatically calibrated, multiple lightning induction voltage avoiding or recovering capabilities are provided, and the lightning induction and self-calibration functions are effectively slowed down, so that the manual operation requirement is reduced, and the equipment maintenance cost is reduced.

Description

Technical Field

[0001] The utility model relates to the field of monitoring equipment, in particular to an online grounding resistance monitoring instrument. Background Art

[0002] In the application of ground resistance online monitors, the equipment is usually installed near outdoor grounding points for a long time. Outdoor target monitoring grounding points often face various complex and severe weather conditions, especially extreme environments such as lightning induction and direct lightning strikes. Since the lightning protection device near the target monitoring grounding point may not completely cover the monitoring area, when thunderstorms occur, on the one hand, lightning induction and direct lightning strikes may cause great electromagnetic interference to the circuit of the monitoring instrument, and even cause circuit failure or equipment damage. On the other hand, the high-voltage instantaneous pulse caused by lightning strikes may have a devastating effect on the internal circuit and power supply system of the equipment. In order to ensure that these devices can operate stably for a long time under thunderstorm weather conditions, the existing technology currently has lightning protection devices or structures added to outdoor monitoring equipment. However, the self-calibration lightning protection devices added to the ground resistance monitor in the current existing technology are generally more complex in structure, which will lead to an increase in packaging volume and cost, which is not conducive to production and use and limits the size, thereby affecting the monitoring effect of the outdoor target monitoring grounding point. Utility Model Content

[0003] The utility model provides an on-line grounding resistance monitor, which solves the problem in the prior art of lacking a low-cost and simple-structured self-calibration monitoring lightning protection design device during outdoor grounding point monitoring.

[0004] The utility model is realized by the following technical solutions:

[0005] A grounding resistance online monitor comprises a central processing module, an LCD display module and a communication module which are mutually signal-connected, and also comprises a grounding acquisition module, a power management module and an analog-to-digital conversion module; the output end of the grounding acquisition module is connected to the input end of the analog-to-digital conversion module, and the output end of the analog-to-digital conversion module is respectively connected to the central processing module and the grounding acquisition module; the grounding acquisition module is provided with a first acquisition end P and a second acquisition end C, and the power management module maintains overall power supply for the device by connecting to the grounding acquisition module.

[0006] In order to ensure that these devices can operate stably for a long time under thunderstorm weather conditions, the existing technology currently adds lightning protection devices or structures to outdoor monitoring equipment. However, the lightning protection devices added to the ground resistance monitor in the existing technology are generally complex in structure, which will increase the packaging volume and cost, which is not conducive to production and use and limits the volume size, thereby affecting the monitoring effect of the outdoor target monitoring grounding point. Based on this, the utility model provides a ground resistance online monitor to solve the problem of the lack of low-cost and simple-structured monitoring lightning protection design devices in the process of outdoor grounding point monitoring in the existing technology.

[0007] Furthermore, the grounding acquisition module includes a double-throw relay M, a self-calibration unit and a lightning protection unit. The self-calibration unit maintains a switchable signal connection with the lightning protection unit through the double-throw relay M.

[0008] Furthermore, the self-calibration unit includes a current relay KA, a transformer T and a first resistor R1; one end of the current relay KA is grounded; one end of the primary winding of the transformer T is grounded, and the other end is connected to the other end of the current relay KA; one end of the secondary winding of the transformer T and one end of the first resistor R1 are both connected to the endpoint F1, and the other end of the first resistor R1 is grounded; the other end of the secondary winding of the transformer T is connected to the double-throw relay M.

[0009] Further, the lightning protection unit includes a second resistor R2, a third resistor R3, a first TVS tube Q1 and a second TVS tube Q2; one end of the first TVS tube Q1, one end of the second TVS tube Q2, one end of the second resistor R2 and a grounding end are connected to the same point; the end of the other end of the first TVS tube Q1 is set as a first collection end P, and the end of the other end of the second TVS tube Q2 is set as a second collection end C; the other end of the second resistor R2 is connected to one end of the third resistor R3, and the other end of the third resistor R3 is connected to the inside of the double-throw relay M.

[0010] Furthermore, a first switch paddle K1 is provided inside the double-throw relay M, and the first switch paddle K1 is provided at the end of the other end of the secondary winding of the transformer T; a first switch contact D1 and a second switch contact D2 that can contact and close with the first switch paddle K1 are also provided inside the double-throw relay M, and the first switch contact D1 is connected to the end point E2 between the second TVS tube Q2 and the second collection end C, and the second switch contact D2 is provided at the end of the other end of the third resistor R3.

[0011] Furthermore, the double-throw relay M is also provided with a second switch paddle K2, a third switch contact D3 and a fourth switch contact D4, and the third switch contact D3 and the fourth switch contact D4 can contact and close with the second switch paddle K2; the third switch contact D3 is connected to the end point E1 between the first TVS tube Q1 and the first collection end P, and the fourth switch contact D4 is connected and arranged between the second resistor R2 and the third resistor R3.

[0012] Furthermore, the end point F1 is also connected to a first ADC branch ACH1 ; the second switch paddle K2 is also connected to a second ADC branch ACH2 from outside the double-throw relay M.

[0013] Compared with the prior art, the utility model integrates multiple functional modules in one, can regularly record the grounding resistance value and automatically calibrate it, has multiple lightning induced voltage avoidance or recovery capabilities, and has the advantages of reducing the need for manual operation and the beneficial effect of reducing equipment maintenance costs while ensuring effective lightning induction mitigation and self-calibration functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings described herein are used to provide a further understanding of the embodiments of the present utility model, constitute a part of this application, and do not constitute a limitation of the embodiments of the present utility model. In the drawings:

[0015] Figure 1 This is a schematic diagram of the data transmission structure of the utility model module;

[0016] Figure 2 This is a schematic diagram of the circuit structure of the ground acquisition module of the utility model;

[0017] Figure 3 This is a three-dimensional diagram of the packaging box of the utility model. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the utility model more clearly understood, the utility model is further described in detail below in conjunction with embodiments and drawings. The schematic implementation manner of the utility model and its description are only used to explain the utility model and are not intended to limit the utility model.

[0019] like Figure 1As shown, this embodiment is an online grounding resistance monitor, including a central processing module, an LCD display module and a communication module that maintain signal connection with each other, and also includes a grounding acquisition module, a power management module and an analog-to-digital conversion module; the output end of the grounding acquisition module is connected to the input end of the analog-to-digital conversion module, and the output end of the analog-to-digital conversion module is respectively connected to the central processing module and the grounding acquisition module; the grounding acquisition module is provided with a first acquisition terminal P and a second acquisition terminal C, and the power management module maintains overall power supply for the device by connecting to the grounding acquisition module.

[0020] Furthermore, the grounding acquisition module includes a double-throw relay M, a self-calibration unit and a lightning protection unit. The self-calibration unit maintains a switchable signal connection with the lightning protection unit through the double-throw relay M.

[0021] Wherein, the self-calibration unit includes a current relay KA, a transformer T and a first resistor R1; one end of the current relay KA is grounded; one end of the primary winding of the transformer T is grounded, and the other end is connected to the other end of the current relay KA; one end of the secondary winding of the transformer T and one end of the first resistor R1 are both connected to the endpoint F1, and the other end of the first resistor R1 is grounded; the other end of the secondary winding of the transformer T is connected to the double-throw relay M.

[0022] Further, the lightning protection unit includes a second resistor R2, a third resistor R3, a first TVS tube Q1 and a second TVS tube Q2; one end of the first TVS tube Q1, one end of the second TVS tube Q2, one end of the second resistor R2 and a grounding end are connected to the same point; the end of the other end of the first TVS tube Q1 is set as a first collection end P, and the end of the other end of the second TVS tube Q2 is set as a second collection end C; the other end of the second resistor R2 is connected to one end of the third resistor R3, and the other end of the third resistor R3 is connected to the inside of the double-throw relay M.

[0023] Furthermore, a first switch paddle K1 is provided inside the double-throw relay M, and the first switch paddle K1 is provided at the end of the other end of the secondary winding of the transformer T; a first switch contact D1 and a second switch contact D2 that can contact and close with the first switch paddle K1 are also provided inside the double-throw relay M, and the first switch contact D1 is connected to the end point E2 between the second TVS tube Q2 and the second collection end C, and the second switch contact D2 is provided at the end of the other end of the third resistor R3.

[0024] Furthermore, the double-throw relay M is also provided with a second switch paddle K2, a third switch contact D3 and a fourth switch contact D4, and the third switch contact D3 and the fourth switch contact D4 can contact and close with the second switch paddle K2; the third switch contact D3 is connected to the end point E1 between the first TVS tube Q1 and the first collection end P, and the fourth switch contact D4 is connected and arranged between the second resistor R2 and the third resistor R3.

[0025] Furthermore, the end point F1 is also connected to a first ADC branch ACH1 ; the second switch paddle K2 is also connected to a second ADC branch ACH2 from outside the double-throw relay M.

[0026] like Figure 1 As shown, the central processing module uses a low-power MCU to process signals, execute algorithms and control the work of other modules; a certain current AC excitation is achieved through a waveform excitation amplifier circuit and a transformer driver stage; the excitation frequency avoids the power frequency signal and its harmonics to obtain a more accurate effect; the excitation frequency of the reference channel and the measurement channel is digitized synchronously, and a high-precision ground resistance measurement result is obtained by calculation. The LCD display module is used to display real-time data, such as ground resistance and device status. The communication module is used to achieve communication with external devices or networks, including data transmission and remote monitoring. The grounding acquisition module is responsible for collecting grounding resistance related signals, converting them into digital signals and passing them to the analog-to-digital conversion module. The power management module provides power supply for all modules to ensure the normal operation of the system. The analog-to-digital conversion module converts the analog signal generated by the grounding acquisition module into a digital signal, which is convenient for the central processing module to process. The MCU in the central processing module generates a signal source for the test working frequency. The output amplitude of the signal source will automatically adjust the measurement function of multiple ranges according to the test process, and the software automatically controls the program to obtain better measurement accuracy and numerical stability. The excitation current is sent out through the second acquisition terminal C after the transformer, and forms a loop with the sampled 50-ohm first resistor R1; the first acquisition terminal P is the voltage sampling point of the grounding resistor. The current obtained at this point is reduced by a high-resistance amplifier, which can maximize the measurement accuracy.

[0027] The grounding acquisition module measures the grounding resistance through two main ports, namely, through the first acquisition terminal P and the second acquisition terminal C. The circuit forms a relay switching network through the current relay KA, and regular calibration is achieved through the built-in first resistor R1 and transformer T to avoid the accuracy drift caused by long-term circuit parameter changes and large-scale temperature changes. In the specific implementation of monitoring in thunderstorm weather, the overall device in this embodiment measures the grounding resistance according to a predetermined period. After the short measurement time is over, the double-throw relay M disconnects the first acquisition terminal P and the second acquisition terminal C to avoid the 1500V voltage causing the lightning induced impulse voltage to damage the internal circuit of the monitor. At the same time, when the first acquisition terminal P and the second acquisition terminal C are working, they are also connected to the first TVS tube Q1 and the second TVS tube Q2 to avoid damaging the internal circuit when the internal withstand voltage is exceeded, and further protect the safety of the working circuit; the first TVS tube Q1 and the second TVS tube Q2 are turned on at a certain voltage, and then they can be restored to the disconnected state, so that the circuit can work normally again. Even if the lightning induced voltage exceeds the energy and it is damaged, it is very easy to judge and manually replace and repair the instrument. In order to prevent the lightning induced voltage from damaging the measurement circuit, the first collection terminal P and the second collection terminal C are both connected to TVS tubes. When one of the collection terminals is subjected to a high voltage impact, the corresponding TVS tube is turned on, which can protect the circuit of the core part of the grounding resistor from being damaged.

[0028] It should be noted that Figure 1 The direction of the arrow in means the direct transmission direction of data during the implementation process, indicating the direction of data during actual operation in this embodiment; and the "mutual signal connection" between the central processing module, LCD display module and communication module is a commonly used preset state of equipment in the prior art, which means that the three are in a mutually communicative state, and has no common meaning with the direction of the arrow. The first ADC branch ACH1 and the second ADC branch ACH2 are both connected to the ADC device access port in the analog-to-digital conversion module, and are both used to realize the digitization of 3.3V analog signals; the ADC is an analog-to-digital converter or similar device in conventional technology. The two signals of ACH2 and ACH1 are buffered and sent to the ADC for waveform acquisition and analysis, and finally an accurate resistance measurement value is obtained. When the double-throw relay M is in the formal working measurement state, it switches to the normally open node, and correspondingly switches to connect to the external points C and P, so as to measure the ground resistance value. The switching instrument is connected to the external circuit, relying on the insulation capacity of the relay to obtain an isolation capacity greater than 1500V to avoid damage to the internal circuit by the lightning induced voltage; at this time, the second resistor R2 is set to a 100 ohm high-precision low-temperature drift reference resistor in this embodiment, and the measurement circuit performs an acquisition action on the reference circuit, and self-calibrates the current instrument measurement circuit by digitizing and calculating the waveforms of ACH2 and ACH1 to ensure the accuracy of the next measurement of the external ground resistance.

[0029] In specific implementation, the double-throw relay M is used to assist automatic calibration and avoid induced lightning damage. When the device is initialized, the central processing module in the device will start the automatic calibration process and switch the switch of the double-throw relay M to the internal calibration circuit. At this time, the voltage obtained at point P (ACH2) comes from the internal 100 ohm high-precision low-temperature drift reference resistor (i.e., the second resistor R2). The values ​​tested by the calibration software process are calculated and stored for each range inside the instrument. So that the instrument can always maintain sufficient accuracy and resist the influence of temperature drift that may occur during large temperature changes in different seasons. When the system measures the ground resistance intermittently according to the predetermined plan, once each measurement task is completed, the relay switches the contacts of the first switch paddle K1 and the second switch paddle K2 to the second switch contact D2 and the fourth switch contact D4 representing the inside of the instrument. At this time, the internal circuit is disconnected from the first acquisition terminal P and the second acquisition terminal C of the external connection. If a higher voltage induced by lightning is generated during this period, which is not greater than the withstand voltage of the current relay KA and the double-throw relay M, the internal circuit is protected, which can greatly reduce the probability of damage to the instrument caused by lightning induced voltage.

[0030] This embodiment can timely detect abnormal voltage conditions of grounding resistance in thunderstorm weather by real-time monitoring of grounding resistance changes, and transmit data to the monitoring center through remote communication, thereby realizing dynamic management of the grounding system and improving the safety and reliability of electrical equipment. At the same time, this embodiment can be installed on the grounding point to work continuously, regularly record the grounding resistance value, and upload it to the cloud platform at the same time. It has multiple lightning induced voltage avoidance or recovery capabilities, and has an automatic calibration function. It can ensure the accuracy of measurement data in outdoor, especially northern climates, and a wide range of temperature changes in four seasons.

[0031] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the utility model in detail. It should be understood that the above description is only the specific implementation method of the utility model and is not used to limit the protection scope of the utility model. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the utility model should be included in the protection scope of the utility model.

Claims

1. A ground resistance online monitor, comprising a central processing module, an LCD display module and a communication module which are mutually connected in signal connection, characterized in that: It also includes a grounding acquisition module, a power management module and an analog-to-digital conversion module; the output end of the grounding acquisition module is connected to the input end of the analog-to-digital conversion module, and the output end of the analog-to-digital conversion module is respectively connected to the central processing module and the grounding acquisition module; the grounding acquisition module is provided with a first acquisition terminal P and a second acquisition terminal C, and the power management module maintains overall power supply for the device by connecting to the grounding acquisition module.

2. The ground resistance online monitoring instrument according to claim 1, characterized in that: The grounding acquisition module includes a double-throw relay M, a self-calibration unit and a lightning protection unit. The self-calibration unit maintains a switchable signal connection with the lightning protection unit through the double-throw relay M.

3. The ground resistance online monitoring instrument according to claim 2, characterized in that: The self-calibration unit includes a current relay KA, a transformer T and a first resistor R1; one end of the current relay KA is grounded; one end of the primary winding of the transformer T is grounded, and the other end is connected to the other end of the current relay KA; one end of the secondary winding of the transformer T and one end of the first resistor R1 are both connected to the endpoint F1, and the other end of the first resistor R1 is grounded; the other end of the secondary winding of the transformer T is connected to the double-throw relay M.

4. The ground resistance online monitoring instrument according to claim 3 is characterized in that: The lightning protection unit includes a second resistor R2, a third resistor R3, a first TVS tube Q1 and a second TVS tube Q2; one end of the first TVS tube Q1, one end of the second TVS tube Q2, one end of the second resistor R2 and a grounding end are connected to the same point; the end of the other end of the first TVS tube Q1 is set as a first collection end P, and the end of the other end of the second TVS tube Q2 is set as a second collection end C; the other end of the second resistor R2 is connected to one end of the third resistor R3, and the other end of the third resistor R3 is connected to the inside of the double-throw relay M.

5. The ground resistance online monitoring instrument according to claim 4, characterized in that: The double-throw relay M is provided with a first switch paddle K1 inside, and the first switch paddle K1 is arranged at the end of the other end of the secondary winding of the transformer T; the double-throw relay M is also provided with a first switch contact D1 and a second switch contact D2 that can contact and close with the first switch paddle K1, the first switch contact D1 is connected to the end point E2 between the second TVS tube Q2 and the second collection end C, and the second switch contact D2 is arranged at the end of the other end of the third resistor R3.

6. The ground resistance online monitoring instrument according to claim 4, characterized in that: The double-throw relay M is also provided with a second switch paddle K2, a third switch contact D3 and a fourth switch contact D4, and the third switch contact D3 and the fourth switch contact D4 can contact and close with the second switch paddle K2; the third switch contact D3 is connected to the end point E1 between the first TVS tube Q1 and the first collection end P, and the fourth switch contact D4 is connected and arranged between the second resistor R2 and the third resistor R3.

7. The ground resistance online monitoring instrument according to claim 3, characterized in that: The endpoint F1 is also connected to a first ADC branch ACH1.

8. The ground resistance online monitoring instrument according to claim 6, characterized in that: The second switch paddle K2 is also connected to a second ADC branch ACH2 from outside the double-throw relay M.

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