An online monitoring device and method for comprehensive characteristics of ground grid

Abstract

The application provides a ground net characteristic comprehensive online monitoring device, which comprises a main control unit, an external signal unit, a current measurement unit, a voltage measurement unit and an electrode system; the main control unit is used for receiving measurement data of the current measurement unit and the voltage measurement unit and calculating ground net resistance or judging electrical connection integrity. The electrode system comprises a comprehensive ground net E pole, a voltage P1 pole, a current C1 pole, a voltage P2 pole, a current C2 pole, a voltage P3 pole and a current C3 pole; the main control unit controls the external signal unit to apply different types of excitation signals to corresponding electrodes in different measurement modes; the current measurement unit and the voltage measurement unit synchronously collect the current and the voltage of a test loop; and the main control unit calculates the ground net resistance or judges the electrical connection integrity, so that a comprehensive online monitoring device capable of simultaneously realizing ground net resistance measurement, loop ground net electrical integrity measurement and comprehensive ground net electrical integrity measurement is constructed.

Description

Technical Field

[0001] This invention relates to the field of smart grid technology, and in particular to a device and method for comprehensive online monitoring of ground grid characteristics. Background Technology

[0002] The grounding grid is a crucial safety facility in power systems, communication systems, buildings, and other applications. It is used to safely conduct fault currents and lightning currents from equipment or systems to the earth, preventing personal injury and equipment damage. During use, the grounding grid is affected by factors such as soil corrosion, environmental changes, lightning current surges, and poor electrical connections. This can cause the grounding resistance to gradually increase, leading to a rise in the voltage of the grounding grid and its grounding terminals, which in turn can result in personal injury accidents and equipment damage.

[0003] Currently, online monitoring devices for grounding grid characteristics mainly employ two technical solutions: one involves applying AC220V to the voltage electrode and injecting a constant current of 5A~8A at a different frequency (45Hz, 55Hz, or 60Hz) into the current electrode. This method allows for wiring distances up to 200 meters, with small measurement errors and high accuracy. However, because the injection frequency is close to the power frequency of 50Hz, it is susceptible to external signal interference, and applying AC220V poses a risk of accidental contact by personnel, resulting in poor safety. The other solution involves applying a voltage no higher than AC36V to the voltage electrode and injecting a constant current of 11mA at a different frequency (128Hz) into the current electrode. While this approach considers personnel safety, the smaller injection current limits the wiring distance between the voltage and current electrodes (not exceeding 30 meters), failing to meet the wiring distance requirements of standard TB-T3233-2010 "Measurement Method for Railway Integrated Grounding Systems" (which requires a wiring distance of 2 to 4 times the diagonal length of the grounding grid), leading to larger measurement errors. In addition, although AC36V is the safe voltage for the human body in a dry environment, the safe voltage for the human body should be lower than 12V in a humid environment. Therefore, this solution still poses a safety hazard in practical applications.

[0004] Furthermore, grounding grid characteristic monitoring should not only include the measurement of grounding grid resistance, but also the monitoring of the electrical integrity between the equipment system and the integrated grounding grid and ring grounding grid. If there is a loose connection or disconnection between the equipment system and the grounding grid, it will also lead to an increase in the equipment system voltage, increasing the risk to personal safety. Therefore, existing technologies still have shortcomings in the comprehensive monitoring of grounding grid characteristics, and there is an urgent need for an online monitoring device and method that can simultaneously measure grounding grid resistance and electrical connection integrity, while ensuring both measurement accuracy and safety. Summary of the Invention

[0005] This invention proposes a comprehensive online monitoring device and method for ground grid characteristics, which solves the problems that existing ground grid characteristic monitoring systems cannot simultaneously and accurately monitor ground grid resistance and electrical connection integrity.

[0006] The technical solution of this invention is implemented as follows: The first aspect of the present invention provides a comprehensive online monitoring device for ground grid characteristics, comprising: a main control unit, an external signal unit, a current measurement unit, a voltage measurement unit, and an electrode system; The electrode system includes an E pole for the integrated ground grid, a P1 pole for voltage, a C1 pole for current, a P2 pole for voltage, a C2 pole for current, a P3 pole for voltage, and a C3 pole for current. The E pole for the integrated ground grid is used to connect to the integrated ground grid to be tested. The P1 and C1 poles for voltage and current are buried in the soil away from the integrated ground grid and are used for measuring the resistance of the ground grid. The P2 and C2 poles for voltage and current are connected to the ring ground grid and are used for measuring the electrical integrity of the ring ground grid. The P3 and C3 poles for voltage and current are connected to the integrated ground grid and are used for measuring the electrical integrity of the integrated ground grid. The external signal unit is connected to the main control unit and receives instructions from the main control unit. In the ground grid resistance measurement mode, it applies a safe AC voltage to the voltage P1 terminal and injects a constant current of different frequency into the current C1 terminal; in the electrical integrity measurement mode, it applies a safe DC voltage to the voltage P2 or voltage P3 terminal. The current measurement unit is connected in series between the E pole of the integrated grounding grid and the current C1, current C2, and current C3 poles, and is used to measure the test current. The voltage measurement unit is connected in parallel between the E pole of the integrated grounding grid and the voltage poles P1, P2, and P3, and is used to measure the test voltage. The main control unit is used to receive measurement data from the current measurement unit and the voltage measurement unit, and to calculate the ground grid resistance or determine the integrity of the electrical connection.

[0007] Specifically, the external signal unit includes a rectifier circuit, a function selection switch, an inverter circuit, a PWM modulation circuit, a current protection module, and a voltage protection module; The rectifier circuit is used to convert external alternating current into direct current. The function selection switch includes three independent switches, which correspond to the ground grid resistance measurement mode, the ring ground grid electrical integrity measurement mode, and the integrated ground grid electrical integrity measurement mode, respectively. The state of each switch is controlled and switched by the main control unit. When the function selection switch is switched to the ground grid resistance measurement mode, the inverter circuit converts DC power into AC power. The PWM modulation circuit generates a precise voltage control signal according to the instructions of the main control unit, modulates the AC power output by the inverter circuit, and realizes multi-level voltage output of the rated voltage. The current protection module uses a hardware comparator to achieve fast overcurrent protection. The voltage protection module achieves overvoltage and undervoltage protection through a voltage divider sampling circuit combined with a TVS diode.

[0008] Preferably, the monitoring device further includes a safety protection unit connected in the measurement circuit, which includes an overvoltage protection module, an overcurrent protection module, and a lightning protection module;

[0009] The overvoltage protection module uses a regulated power supply and a thyristor short-circuit protection circuit. When the output voltage exceeds the set voltage threshold, the thyristor short-circuit power supply forces the fuse to blow quickly.

[0010] The overcurrent protection module automatically cuts off the output circuit when the output current is short-circuited.

[0011] The lightning protection module is used to bypass the surge current during a lightning current surge to protect the internal circuitry of the device.

[0012] Specifically, both the current measurement unit and the voltage measurement unit include a safety protection module, a signal conditioning module, and a synchronous sampling ADC module connected in sequence.

[0013] The safety protection module uses a regulated power supply and an overvoltage protection circuit to provide voltage and current limiting protection for the input signal.

[0014] The signal conditioning module is used to amplify and filter the signal to suppress common-mode interference;

[0015] The synchronous sampling ADC module uses a multi-channel synchronous sampling chip to support multi-channel synchronous acquisition of voltage and current signals to eliminate phase difference.

[0016] Preferably, the monitoring device further includes a communication unit connected to the main control unit, including a remote communication network port, a USB debugging interface, an RS232 interface, and an RS485 interface;

[0017] The remote communication network port is an RJ45 network port, which is used to connect to the remote master station system, send monitoring information to the remote master station system, and receive control commands from the remote master station system.

[0018] The USB debugging interface connects to an external computer for program updates and parameter settings;

[0019] The RS232 and RS485 interfaces are used for communication connections with other local smart devices.

[0020] Preferably, the monitoring device further includes a display unit connected to the main control unit via optical coupling isolation, including indicator lights and a display screen;

[0021] The indicator lights include a power indicator light, a running indicator light, a communication indicator light, and a fault indicator light;

[0022] The display screen is used to display equipment information, fault information, and line operation information in real time.

[0023] Preferably, the monitoring device further includes a current-limiting resistor, which is connected between the current measurement unit and the main control unit;

[0024] The current-limiting resistor is a switchable resistor. In the ground grid resistance measurement mode, a 60Ω resistor is connected to control the current loop current below 100mA; in the electrical integrity measurement mode, a 24Ω resistor is connected to control the current loop current below 500mA.

[0025] A second aspect of the present invention provides a method for comprehensive online monitoring of ground network characteristics, comprising the following steps:

[0026] Initialize the device and complete the self-test;

[0027] Switch to the corresponding measurement mode based on the combination of states of the function selection switch;

[0028] In the ground grid resistance measurement mode, the external signal unit applies an AC voltage of no more than AC12V to the voltage P1 pole and injects a constant 100mA current of 128Hz into the current C1 pole. The current measurement unit and the voltage measurement unit synchronously collect current and voltage signals, and the main control unit calculates the grounding resistance value based on the collected signals.

[0029] In the ring ground grid electrical integrity measurement mode, the external signal unit applies a constant DC12V voltage to the voltage P2 pole, the current measurement unit collects the current signal of the current C2 pole, and the main control unit calculates the ring ground grid electrical connection resistance based on the voltage and current.

[0030] In the integrated grounding grid electrical integrity measurement mode, the external signal unit applies a constant DC12V voltage to the voltage P3 pole, the current measurement unit collects the current signal of the current C3 pole, and the main control unit calculates the integrated grounding grid electrical connection resistance based on the voltage and current.

[0031] The calculation results are sent to the remote master station system via the communication unit.

[0032] Preferably, the ground grid resistance measurement mode further includes:

[0033] An AC voltage is applied to the voltage P1 terminal in a step-by-step increasing manner, starting from 0.6V and increasing by 0.6V step by step until it reaches 12V;

[0034] Under each voltage level, the current of the current-detecting current C1 pole is within the range of 95mA to 100mA. If it is within the preset range, the grounding resistance value is calculated and output based on the current voltage and current.

[0035] If the current is still outside the preset range at a rated voltage of 12V, the measurement is considered a failure and the process returns to the initialization step.

[0036] Specifically, the electrical integrity measurement mode further includes:

[0037] Apply a constant DC 12V voltage U and detect the current I at the corresponding current electrode, then calculate the total resistance R;

[0038] Subtracting the current-limiting resistor value yields the actual electrical connection resistance;

[0039] The actual electrical connection resistance is compared with a preset resistance threshold. If it is less than the preset resistance threshold, the connection is considered reliable. If it is greater than or equal to the threshold, the connection is considered abnormal and an alarm signal is output.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention sets up an electrode system including a comprehensive ground grid E pole, a voltage P1 pole, a current C1 pole, a voltage P2 pole, a current C2 pole, a voltage P3 pole, and a current C3 pole. The main control unit controls the external signal unit to apply different types of excitation signals to the corresponding electrodes under different measurement modes. At the same time, the current and voltage of the test circuit are synchronously collected by the current measurement unit and the voltage measurement unit. Finally, the main control unit calculates the ground grid resistance or judges the electrical connection integrity, thereby constructing a comprehensive online monitoring device that can simultaneously realize the measurement of ground grid resistance, the measurement of ring ground grid electrical integrity, and the measurement of comprehensive ground grid electrical integrity. (2) The external signal unit of the present invention integrates a rectifier circuit, a function selection switch, an inverter circuit, a PWM modulation circuit, a current protection module, and a voltage protection module. By controlling the switching of the function selection switch through the main control unit, it can flexibly switch between different measurement modes and realize the accurate output of multi-level voltages. The PWM modulation circuit generates an accurate voltage control signal according to the instruction to ensure the stability and adjustability of the output voltage. The current protection module uses a hardware comparator to realize fast overcurrent protection, and the voltage protection module uses a voltage divider sampling circuit combined with a TVS diode to realize overvoltage and undervoltage protection. The multiple protection mechanisms ensure the safe and reliable output of the external signal under various operating conditions. (3) The safety protection unit set in this invention is connected to the measurement circuit and integrates an overvoltage protection module, an overcurrent protection module and a lightning protection module, forming a comprehensive safety protection system. The overvoltage protection module adopts a regulated power supply and a thyristor short-circuit protection circuit, which can quickly cut off the output when the output voltage exceeds the set threshold. The overcurrent protection module automatically cuts off the output circuit when the output current is short-circuited. The lightning protection module bypasses the impact current when lightning current impacts. This multi-level protection mechanism effectively ensures the safety of the device itself and personnel in abnormal situations such as voltage short circuit, current short circuit, lightning current impact or accidental contact by personnel. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the overall architecture of a ground network characteristic integrated online monitoring device according to the present invention.

[0043] Figure 2 This is a schematic diagram of the internal principle of a comprehensive online monitoring device for ground grid characteristics according to the present invention.

[0044] Figure 3 This is a flowchart illustrating a method for comprehensive online monitoring of ground network characteristics according to the present invention.

[0045] Figure 4 This is a schematic diagram of the process for measuring the ground grid resistance in an embodiment of the present invention. Detailed Implementation

[0046] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0047] Reference Figure 1 , 2 The first aspect of the present invention provides a comprehensive online monitoring device for ground grid characteristics, comprising: a main control unit, an external signal unit, a current measurement unit, a voltage measurement unit, and an electrode system;

[0048] The electrode system includes an E pole for the integrated ground grid, a P1 pole for voltage, a C1 pole for current, a P2 pole for voltage, a C2 pole for current, a P3 pole for voltage, and a C3 pole for current. The E pole for the integrated ground grid is used to connect to the integrated ground grid to be tested. The P1 and C1 poles for voltage and current are buried in the soil away from the integrated ground grid and are used for measuring the resistance of the ground grid. The P2 and C2 poles for voltage and current are connected to the ring ground grid and are used for measuring the electrical integrity of the ring ground grid. The P3 and C3 poles for voltage and current are connected to the integrated ground grid and are used for measuring the electrical integrity of the integrated ground grid.

[0049] The external signal unit is connected to the main control unit and receives instructions from the main control unit. In the ground grid resistance measurement mode, it applies a safe AC voltage to the voltage P1 terminal and injects a constant current of different frequency into the current C1 terminal; in the electrical integrity measurement mode, it applies a safe DC voltage to the voltage P2 or voltage P3 terminal.

[0050] The current measurement unit is connected in series between the E pole of the integrated grounding grid and the current C1, current C2, and current C3 poles, and is used to measure the test current.

[0051] The voltage measurement unit is connected in parallel between the E pole of the integrated grounding grid and the voltage poles P1, P2, and P3, and is used to measure the test voltage.

[0052] The main control unit is used to receive measurement data from the current measurement unit and the voltage measurement unit, and to calculate the ground grid resistance or determine the integrity of the electrical connection.

[0053] In this embodiment, the main control unit uses a DSC chip of model STM32f407VG. The chip has a lot of internal resources, large storage capacity, and low price. At the same time, the ARM chip has a wireless communication interface, an Ethernet communication interface, and can also generate PWM waves. It can quickly process and output analog quantities, image information, control signals, alarm signals, and stored data, and has an embedded grounding resistance calculation method.

[0054] Specifically, the external signal unit includes a rectifier circuit, a function selection switch, an inverter circuit, a PWM modulation circuit, a current protection module, and a voltage protection module;

[0055] The rectifier circuit is used to convert external alternating current into direct current.

[0056] The function selection switch includes three independent switches, which correspond to the ground grid resistance measurement mode, the ring ground grid electrical integrity measurement mode, and the integrated ground grid electrical integrity measurement mode, respectively. The state of each switch is controlled and switched by the main control unit.

[0057] When the function selection switch is switched to the ground grid resistance measurement mode, the inverter circuit converts DC power into AC power.

[0058] The PWM modulation circuit generates a precise voltage control signal according to the instructions of the main control unit, modulates the AC power output by the inverter circuit, and realizes multi-level voltage output of rated voltage; when measuring the ground grid resistance, a voltage of no more than AC12V is applied to the voltage electrode, and a constant 100mA current of different frequency (128hz) is injected into the current electrode; when measuring the electrical integrity of the ring ground grid and the integrated ground grid, a voltage of no more than DC12V is applied to the voltage electrode, and a constant 500mA current is injected into the current electrode.

[0059] The current protection module uses a hardware comparator to achieve fast overcurrent protection.

[0060] The voltage protection module achieves overvoltage and undervoltage protection through a voltage divider sampling circuit combined with a TVS diode.

[0061] In this embodiment, the rectifier circuit uses a full-bridge topology to convert AC 12V, 50Hz AC power into DC 12V, 50Hz DC power. When performing ground grid resistance measurement, function selection switch 1 is closed, and function selection switches 2 and 3 are open. The inverter circuit uses an IGBT H-bridge to invert the DC 12V, 50Hz DC power into AC 12V, 128Hz AC output. The PWM modulation circuit generates precise voltage control based on the microcontroller, modulating the AC 12V, 128Hz AC power into AC 0.6V, AC 1.2V, AC 1.8V, etc., for output. When performing ring ground grid electrical integrity measurement, function selection switch 1 is open, function selection switch 2 is closed, and function selection switch 3 is open. When performing comprehensive ground grid electrical integrity measurement, function selection switch 1 is open, function selection switch 2 is open, and function selection switch 3 is closed. The main control unit (MCU) monitors the state of the function selection switches in real time.

[0062] Preferably, the monitoring device further includes a safety protection unit connected in the measurement circuit, which includes an overvoltage protection module, an overcurrent protection module, and a lightning protection module;

[0063] The overvoltage protection module uses a regulated power supply and a thyristor short-circuit protection circuit. When the output voltage exceeds the set voltage threshold, the thyristor short-circuit power supply forces the fuse to blow quickly.

[0064] The overcurrent protection module automatically cuts off the output circuit when the output current is short-circuited.

[0065] The lightning protection module is used to bypass the surge current during a lightning current surge to protect the internal circuitry of the device.

[0066] Specifically, both the current measurement unit and the voltage measurement unit include an analog signal acquisition unit, which includes a safety protection module, a signal conditioning module, and a synchronous sampling ADC module connected in sequence; the current measurement unit also includes a current sensor, and the voltage measurement unit also includes a voltage sensor.

[0067] The safety protection module uses a 12V / 5A regulated power supply and an overvoltage protection circuit to limit the voltage and current of the input signal. The voltage regulation section consists of a 7805 three-terminal regulator connected to a current-amplifying transistor. The potential of its adjustment terminal is raised by a voltage drop of a Zener diode and an LED connected in series. The overvoltage protection uses a thyristor to short-circuit the power supply, forcing the fuse to blow quickly to protect the downstream circuit. The blowing time is 1~3 microseconds.

[0068] The signal conditioning module is used to amplify and filter the signal to suppress common-mode interference;

[0069] The synchronous sampling ADC module uses a multi-channel synchronous sampling chip, model ADS131M04, which supports multi-channel synchronous acquisition of voltage and current signals to eliminate phase difference.

[0070] Preferably, the monitoring device further includes a communication unit connected to the main control unit, including a remote communication network port, a USB debugging interface, an RS232 interface, and an RS485 interface;

[0071] The remote communication network port is an RJ45 network port, which is used to connect to the remote master station system, send monitoring information to the remote master station system, and receive control commands from the remote master station system.

[0072] The USB debugging interface connects to an external computer for program updates and parameter settings;

[0073] The RS232 and RS485 interfaces are used for communication connections with other local smart devices;

[0074] In this embodiment, the communication unit is connected to the main control unit via an RS232 serial port, and can transmit data to the remote master station system via an optical port (corresponding to an optical cable), a network port (corresponding to a network cable), or wireless communication (corresponding to a wireless communication network card).

[0075] Preferably, the monitoring device further includes a display unit connected to the main control unit via optical coupling isolation, including indicator lights and a display screen;

[0076] The indicator lights include a power indicator light, a running indicator light, a communication indicator light, and a fault indicator light;

[0077] The display screen is a human-computer interaction interface used to display device information, fault information, and line operation information in real time.

[0078] The optocoupler isolation model used in this embodiment is TLP112, which ensures the stability and anti-interference of input and output status quantities and analog signals.

[0079] Preferably, the monitoring device further includes a current-limiting resistor, which is connected between the current measurement unit and the main control unit;

[0080] The current-limiting resistor is a switchable resistor. In the ground grid resistance measurement mode, a 60Ω resistor is connected to control the current loop current below 100mA; in the electrical integrity measurement mode, a 24Ω resistor is connected to control the current loop current below 500mA.

[0081] The monitoring device in this embodiment also includes a power supply unit, which is connected to an external AC220V mains power supply and is used to convert it into DC12V power supply to provide power to the main control unit.

[0082] In this embodiment, the electrodes are connected as follows:

[0083] Integrated grounding grid E pole: A metal conductor with grounding function that is buried in the ground and in direct contact with the earth.

[0084] Voltage P1 electrode: Made of stainless steel angle steel, with good corrosion resistance and conductivity; the voltage electrode applies a voltage not exceeding AC12V to form an electric field in the soil. The voltage P1 electrode calculates the grounding resistance by measuring the potential difference of this electric field. It is a voltage grounding electrode arranged at a distance to form a measurement grounding impedance.

[0085] Current C1 electrode: made of stainless steel angle steel, with good corrosion resistance and conductivity, is an auxiliary electrode; a constant 100mA current of different frequency (128hz) is injected into the current electrode, and the injected current forms a current loop with the integrated grounding grid E electrode, which is a current grounding electrode arranged at a distance to form a measurement grounding impedance.

[0086] Voltage P2 pole: Connected to the grounding flat steel of the ring grounding grid, a constant DC12V voltage is applied to measure the electrical integrity of the ring grounding grid connection.

[0087] C2 current terminal: Connected to the grounding flat steel of the ring ground grid, it detects the output current and is used to measure the electrical integrity of the ring ground grid connection.

[0088] Voltage P3: Connected to the grounding flat steel of the integrated grounding grid, a constant DC 12V voltage is applied to measure the electrical integrity of the integrated grounding grid connection.

[0089] Current C3 pole: Connected to the grounding flat steel of the integrated grounding grid, detects the output current, and is used to measure the electrical integrity of the integrated grounding grid connection.

[0090] Grounding flat steel: a grounding electrode that reliably connects the equipment system grounding to the ring grounding grid, and a grounding electrode that reliably connects the ring grounding grid to the integrated grounding grid.

[0091] like Figure 3 As shown, the second aspect of the present invention provides a method for comprehensive online monitoring of ground network characteristics, comprising the following steps:

[0092] The device is initialized and a self-test is completed. After power-on, the device first undergoes initialization, including the initialization and configuration of each module of the main control unit, the reset of the external signal unit, and the initialization of the communication interface. Then, a self-test program is executed to check whether each functional module is working properly, whether the electrode connections are good, and whether the internal parameters are correct. After the self-test passes, the device enters standby mode, awaiting further instructions.

[0093] The main control unit switches to the corresponding measurement mode based on the state combination of the function selection switches. It monitors the state of the function selection switches in real time and determines the measurement mode to be executed based on the closed combination of the three switches: when the switch state is 100 (i.e., switch 1 is closed and switches 2 and 3 are open), it switches to the ground grid resistance measurement mode; when the switch state is 010, it switches to the ring ground grid electrical integrity measurement mode; when the switch state is 001, it switches to the integrated ground grid electrical integrity measurement mode; when the switch state is 000, the device remains in standby mode.

[0094] In the ground grid resistance measurement mode, the external signal unit applies an AC voltage of no more than AC12V to the voltage P1 terminal and injects a constant 100mA current at 128Hz into the current C1 terminal. The current measurement unit and voltage measurement unit synchronously acquire current and voltage signals, and the main control unit calculates the grounding resistance value based on the acquired signals. Using a safe voltage of no more than AC12V fundamentally eliminates the risk of electric shock to personnel. The use of a 128Hz heterogeneous current avoids the interference band of the 50Hz power frequency and its harmonics, and avoids the significant skin effect that would affect measurement accuracy due to excessively high frequencies. The 100mA test current is larger than the traditional 11mA small current scheme, which can obtain stronger signal strength and higher signal-to-noise ratio, thereby supporting longer wiring distances (up to 2 to 4 times the diagonal length of the ground grid) and meeting standard measurement requirements. The synchronous acquisition of voltage and current signals ensures that the voltage and current values ​​used for calculation correspond to the instantaneous values ​​at the same moment, avoiding calculation errors introduced by phase differences. The main control unit calculates the grounding resistance value based on the collected effective voltage and current values, according to Ohm's law R=U / I.

[0095] Preferably, such as Figure 4 As shown, the ground grid resistance measurement mode further includes:

[0096] An AC voltage is applied to the voltage P1 terminal in a step-by-step increasing manner, starting from 0.6V and increasing by 0.6V step by step until it reaches 12V;

[0097] Level 1 voltage (5% of rated voltage): Apply 0.6V (5% of 12V) and check if the current is between 95mA and 100mA; if it is, calculate the grounding resistance value Ra and output the calculated value from the monitoring device; if it is not, proceed to the next voltage level.

[0098] Second voltage level (10% of rated voltage): Apply 1.2V (10% of 12V) and check if the current is between 95mA and 100mA; if it is, calculate the grounding resistance value Ra and the monitoring device outputs the calculated value; if it is not, proceed to the next voltage level.

[0099] This process continues, gradually increasing the voltage by 0.6V each time (i.e., increasing by 5% of 12V) until 12V (100% of the rated voltage) is reached.

[0100] If the current is still outside the preset range (95mA~100mA) when the applied rated voltage is the maximum value of 12V, the measurement is determined to be a failure and the process returns to the initialization step.

[0101] This invention adapts to different grounding resistance values ​​by gradually increasing the voltage from a low starting point. When the grounding resistance is low, a lower voltage is sufficient to reach the preset current range, making low-voltage measurement both safe and energy-efficient. When the grounding resistance is high, the system automatically increases the voltage to maintain sufficient test current, ensuring the signal-to-noise ratio of the measurement signal. This adaptive measurement strategy avoids the problem of inaccurate measurements due to insufficient current caused by excessive grounding resistance under a fixed voltage, and also avoids the risk of exceeding limits due to excessive current caused by insufficient grounding resistance. Simultaneously, the gradual voltage increase also provides a soft-start effect, reducing the impact of voltage surges on the circuit. If the current still does not reach 95mA at the maximum rated voltage of 12V, it indicates that the grounding resistance is too high or there is an open circuit in the loop. The system determines the measurement has failed and returns to initialization, avoiding infinite waiting or erroneous output.

[0102] In the ring ground grid electrical integrity measurement mode, the external signal unit applies a constant DC12V voltage to the voltage P2 terminal, the current measurement unit collects the current signal from the current C2 terminal, and the main control unit calculates the ring ground grid electrical connection resistance based on the voltage and current. A DC12V constant voltage source is used, which is still within the safe voltage range in humid environments, ensuring personnel safety during the measurement process. Excitation is applied through the voltage P2 terminal, and the current C2 terminal detects the loop current, forming a complete measurement loop. The main control unit calculates the total loop resistance based on the collected voltage and current.

[0103] In the integrated grounding grid electrical integrity measurement mode, the external signal unit applies a constant DC12V voltage to the voltage P3 pole, the current measurement unit collects the current signal from the current C3 pole, and the main control unit calculates the integrated grounding grid electrical connection resistance based on the voltage and current. Through the connection points between the voltage P3 pole and the current C3 pole and the integrated grounding grid, the connection resistance between the integrated grounding grid and the grounding system of each device is measured. In conjunction with the ring grounding grid electrical integrity measurement, comprehensive monitoring of the connection status of each key node in the grounding grid system is realized, making up for the shortcomings of traditional grounding grid monitoring that only focuses on grounding resistance and ignores connection integrity.

[0104] The calculation results are sent to the remote master station system through the communication unit. The master control unit encapsulates the calculated ground grid resistance value, ring ground grid electrical connection resistance value, comprehensive ground grid electrical connection resistance value, and related alarm information according to the agreed communication protocol, and sends them to the remote master station system through the remote communication network port of the communication unit. It can also be sent to the local monitoring equipment through RS232 or RS485 interface.

[0105] Specifically, the electrical integrity measurement mode further includes:

[0106] A constant DC 12V voltage U is applied, and the current I at the corresponding current electrode is detected. The total resistance R = U / I is calculated, which includes the current-limiting resistor, the resistance of the connecting wires, the contact resistance, and the resistance of the connection point being tested. Then, the known current-limiting resistor value (24Ω) is subtracted to obtain the actual electrical connection resistance, which mainly reflects the contact condition of the connection point being tested. Finally, the actual electrical connection resistance is compared with a preset threshold (e.g., 50mΩ). If it is less than the threshold, it indicates that the connection point has good contact and the resistance is very small, indicating a reliable connection. If it is greater than or equal to the threshold, it indicates that the connection point has a loose connection, is unstable, or is subject to oxidation or corrosion, resulting in increased contact resistance, indicating an abnormal connection and triggering an alarm signal. The preset threshold of 50mΩ is determined based on engineering experience and can effectively distinguish between normal and abnormal connection states.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A comprehensive online monitoring device for ground grid characteristics, characterized in that, include: The system includes a main control unit, an external signal unit, a current measurement unit, a voltage measurement unit, and an electrode system. The electrode system includes an E pole for the integrated ground grid, a P1 pole for voltage, a C1 pole for current, a P2 pole for voltage, a C2 pole for current, a P3 pole for voltage, and a C3 pole for current. The E pole for the integrated ground grid is used to connect to the integrated ground grid to be tested. The P1 and C1 poles for voltage and current are buried in the soil away from the integrated ground grid and are used for measuring the resistance of the ground grid. The P2 and C2 poles for voltage and current are connected to the ring ground grid and are used for measuring the electrical integrity of the ring ground grid. The P3 and C3 poles for voltage and current are connected to the integrated ground grid and are used for measuring the electrical integrity of the integrated ground grid. The external signal unit is connected to the main control unit and receives instructions from the main control unit. In the ground grid resistance measurement mode, it applies a safe AC voltage to the voltage P1 terminal and injects a constant current of different frequency into the current C1 terminal; in the electrical integrity measurement mode, it applies a safe DC voltage to the voltage P2 or voltage P3 terminal. The current measurement unit is connected in series between the E pole of the integrated grounding grid and the current C1, current C2, and current C3 poles, and is used to measure the test current. The voltage measurement unit is connected in parallel between the E pole of the integrated grounding grid and the voltage poles P1, P2, and P3, and is used to measure the test voltage. The main control unit is used to receive measurement data from the current measurement unit and the voltage measurement unit, and to calculate the ground grid resistance or determine the integrity of the electrical connection.

2. The integrated online monitoring device for ground grid characteristics as described in claim 1, characterized in that, The external signal unit includes a rectifier circuit, a function selection switch, an inverter circuit, a PWM modulation circuit, a current protection module, and a voltage protection module. The rectifier circuit is used to convert external alternating current into direct current. The function selection switch includes three independent switches, which correspond to the ground grid resistance measurement mode, the ring ground grid electrical integrity measurement mode, and the integrated ground grid electrical integrity measurement mode, respectively. The state of each switch is controlled and switched by the main control unit. When the function selection switch is switched to the ground grid resistance measurement mode, the inverter circuit converts DC power into AC power. The PWM modulation circuit generates a precise voltage control signal according to the instructions of the main control unit, modulates the AC power output by the inverter circuit, and realizes multi-level voltage output of the rated voltage. The current protection module uses a hardware comparator to achieve fast overcurrent protection. The voltage protection module achieves overvoltage and undervoltage protection through a voltage divider sampling circuit combined with a TVS diode.

3. The integrated online monitoring device for ground grid characteristics as described in claim 1, characterized in that, The monitoring device also includes a safety protection unit, which is connected to the measurement circuit and includes an overvoltage protection module, an overcurrent protection module, and a lightning protection module. The overvoltage protection module uses a regulated power supply and a thyristor short-circuit protection circuit. When the output voltage exceeds the set voltage threshold, the thyristor short-circuit power supply forces the fuse to blow quickly. The overcurrent protection module automatically cuts off the output circuit when the output current is short-circuited. The lightning protection module is used to bypass the surge current during a lightning current surge to protect the internal circuitry of the device.

4. The integrated online monitoring device for ground grid characteristics as described in claim 1, characterized in that, Both the current measurement unit and the voltage measurement unit include a safety protection module, a signal conditioning module, and a synchronous sampling ADC module connected in sequence. The safety protection module uses a regulated power supply and an overvoltage protection circuit to provide voltage and current limiting protection for the input signal. The signal conditioning module is used to amplify and filter the signal to suppress common-mode interference; The synchronous sampling ADC module uses a multi-channel synchronous sampling chip to support multi-channel synchronous acquisition of voltage and current signals to eliminate phase difference.

5. The integrated online monitoring device for ground grid characteristics as described in claim 1, characterized in that, The monitoring device also includes a communication unit connected to the main control unit, including a remote communication network port, a USB debugging interface, an RS232 interface and an RS485 interface; The remote communication network port is an RJ45 network port, which is used to connect to the remote master station system, send monitoring information to the remote master station system, and receive control commands from the remote master station system. The USB debugging interface connects to an external computer for program updates and parameter settings; The RS232 and RS485 interfaces are used for communication connections with other local smart devices.

6. The integrated online monitoring device for ground grid characteristics as described in claim 1, characterized in that, The monitoring device also includes a display unit connected to the main control unit via optical coupling isolation, including indicator lights and a display screen; The indicator lights include a power indicator light, a running indicator light, a communication indicator light, and a fault indicator light; The display screen is used to display equipment information, fault information, and line operation information in real time.

7. The integrated online monitoring device for ground grid characteristics as described in claim 1, characterized in that, The monitoring device also includes a current-limiting resistor, which is connected between the current measurement unit and the main control unit; The current-limiting resistor is a switchable resistor. In the ground grid resistance measurement mode, a 60Ω resistor is connected to control the current loop current below 100mA; in the electrical integrity measurement mode, a 24Ω resistor is connected to control the current loop current below 500mA.

8. A method for comprehensive online monitoring of ground grid characteristics, based on the comprehensive online monitoring device for ground grid characteristics as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Initialize the device and complete the self-test; Switch to the corresponding measurement mode based on the combination of states of the function selection switch; In the ground grid resistance measurement mode, the external signal unit applies an AC voltage of no more than AC12V to the voltage P1 pole and injects a constant 100mA current of 128Hz into the current C1 pole. The current measurement unit and the voltage measurement unit synchronously collect current and voltage signals, and the main control unit calculates the grounding resistance value based on the collected signals. In the ring ground grid electrical integrity measurement mode, the external signal unit applies a constant DC12V voltage to the voltage P2 pole, the current measurement unit collects the current signal of the current C2 pole, and the main control unit calculates the ring ground grid electrical connection resistance based on the voltage and current. In the integrated grounding grid electrical integrity measurement mode, the external signal unit applies a constant DC12V voltage to the voltage P3 pole, the current measurement unit collects the current signal of the current C3 pole, and the main control unit calculates the integrated grounding grid electrical connection resistance based on the voltage and current. The calculation results are sent to the remote master station system via the communication unit.

9. The method for comprehensive online monitoring of ground grid characteristics as described in claim 8, characterized in that, The ground grid resistance measurement mode further includes: An AC voltage is applied to the voltage P1 terminal in a step-by-step increasing manner, starting from 0.6V and increasing by 0.6V step by step until it reaches 12V; Under each voltage level, the current of the current-detecting current C1 pole is within the range of 95mA to 100mA. If it is within the preset range, the grounding resistance value is calculated and output based on the current voltage and current. If the current is still outside the preset range at a rated voltage of 12V, the measurement is considered a failure and the process returns to the initialization step.

10. The method for comprehensive online monitoring of ground grid characteristics as described in claim 8, characterized in that, The electrical integrity measurement mode further includes: Apply a constant DC 12V voltage U and detect the current I at the corresponding current electrode, then calculate the total resistance R; Subtracting the current-limiting resistor value yields the actual electrical connection resistance; The actual electrical connection resistance is compared with a preset resistance threshold. If it is less than the preset resistance threshold, the connection is considered reliable. If it is greater than or equal to the threshold, the connection is considered abnormal and an alarm signal is output.

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