A radio cable ground loop current acquisition device based on NB-IoT

Abstract

The application discloses a kind of radio cable ground loop current acquisition device based on NB-IoT, belong to electric power equipment monitoring technical field.The device aims at solving the problems such as wiring complex, transmission distance is limited, high power consumption, difficult to remote real-time monitoring in traditional cable ground loop current monitoring.The device includes main control chip, current sensor, temperature sensor, NB-IoT communication module and power management module.Temperature sensor collects cable operating temperature;Current sensor is used for non-contact acquisition ground loop current signal;NB-IoT communication module transmits the processed data to remote monitoring center through the message forwarding function of cloud platform, realizes remote real-time monitoring.Power management module supports lithium battery and solar power supply.The application has the advantages of simple installation, strong anti-interference ability, long transmission distance, low power consumption, remote configuration and alarm function, etc., can effectively improve the safety and reliability of cable operation, reduce operation and maintenance cost.

Description

Technical Field

[0001] This invention belongs to the field of power equipment monitoring technology and relates to a wireless cable grounding loop current acquisition device based on NB-IoT. Background Technology

[0002] In power systems, cables are critical equipment for power transmission and distribution, and their operating status directly affects the safety and stability of the entire power grid. Cable grounding circulating current is one of the important parameters reflecting the cable insulation condition and the health of the grounding system. When cable insulation ages, joints are faulty, or grounding faults occur, abnormal changes will appear in the grounding circulating current. If not monitored and handled in time, this may lead to serious safety accidents, such as cable fires and system tripping.

[0003] Currently, traditional cable grounding loop current monitoring devices mostly use wired connections, transmitting the current signal collected by the sensor to the nearest monitoring terminal or data acquisition unit via analog signal lines. This approach has the following prominent problems in practical engineering applications: Complex wiring and high construction costs: In environments such as cable trenches, tunnels, or overhead cable trays, space is limited and there are many sources of interference. Laying out a large number of signal lines not only makes construction difficult but also easily leads to signal interruption or measurement inaccuracies due to line aging, rodent damage, or mechanical damage. Limited transmission distance: Traditional analog signals are easily affected by factors such as line resistance and electromagnetic interference during long-distance transmission, leading to signal attenuation or distortion, limiting the distance between the monitoring device and the monitoring center. High power consumption and difficulty in long-term operation: While some existing wireless monitoring solutions (such as those based on Wi-Fi or ZigBee) can reduce wiring to some extent, their power consumption is relatively high, relying on frequent battery replacements or external power supplies, making them unsuitable for cable channels without a stable power supply. Difficulty in achieving remote centralized monitoring: Traditional devices mainly rely on local display or short-range wireless transmission, lacking effective integration with IoT cloud platforms, making it impossible to achieve remote real-time data viewing, historical data analysis, and unified management of multiple sites. Low hardware integration and high cost: Many existing solutions still adopt a multi-level architecture of "sensor + external signal conditioning circuit + independent analog-to-digital converter + main controller," resulting in complex circuits, numerous components, high failure rates, and difficulty in reducing system cost and power consumption. Single monitoring parameter: Some devices only collect circulating current signals and do not simultaneously monitor cable temperature. However, temperature and circulating current often couple to reflect insulation faults, making single-parameter monitoring insufficient for a comprehensive assessment of cable operating status. Summary of the Invention

[0004] 1. The technical problem to be solved:

[0005] Traditional cable grounding current monitoring devices suffer from problems such as complex wiring, limited transmission distance, high power consumption, and inability to be remotely monitored.

[0006] 2. Technical Solution:

[0007] To address the above problems, this invention provides a wireless cable grounding current acquisition device based on NB-IoT, characterized in that it includes a current sensor module, an RS485 conversion circuit, a main control chip, a display unit, a temperature acquisition module, an NB-IoT communication module, and a power management module. The current acquisition module is connected to the main control chip through the RS485 conversion circuit. The main control chip is connected to the display unit, the temperature acquisition module, and the NB-IoT communication module respectively. The NB-IoT communication module communicates wirelessly with the cloud platform monitoring terminal through a base station.

[0008] The main control chip is used to control the operation of the entire device, including data acquisition, processing and transmission.

[0009] The RS485 conversion circuit enables bidirectional digital communication between the main control chip and the current sensor.

[0010] The current acquisition module acquires the cable grounding circulating current signal in real time through the current sensor.

[0011] The temperature sensor is attached to the cable joint or near the grounding wire to collect the operating temperature of the cable.

[0012] The NB-IoT communication module is used to transmit the processed data to the remote monitoring center through the message forwarding function of the cloud platform.

[0013] The display unit is used to display the circulation value and temperature value in real time.

[0014] The power management module provides power support for the current sensor, temperature sensor, main control chip, and NB-IoT communication module.

[0015] The main control chip is an STM32F103C8T6 with a working frequency of 72MHz. The main control chip is connected to the NB-IoT communication module through a UART interface and to the current sensor through an RS485 interface. The built-in analog-to-digital converter module directly acquires the analog output signal of the temperature sensor.

[0016] It has built-in Flash and RAM for local data storage and supports remote configuration and firmware upgrades. Users can adjust the device's operating parameters through a remote monitoring center.

[0017] It also includes an alarm unit, which is connected to the main control chip. The specific working method of the alarm unit is as follows: The main control chip compares the collected circulating current value I and temperature value T with preset thresholds: Circulating current threshold: Under normal operating conditions, the grounding circulating current is usually less than 20A. Let the warning threshold be 30A and the alarm threshold be 50A. Temperature threshold: The warning threshold is 70℃ and the alarm threshold is 85℃. If I < 30A and T < 70℃, it is judged as normal; if 30A ≤ I < 50A or 70℃ ≤ T < 85℃, a warning is triggered, and the device issues an intermittent audible and visual alarm through the alarm unit, and at the same time sends a warning message to the monitoring center; if I ≥ 50A or T ≥ 85℃, an alarm is triggered, and the alarm unit issues a continuous audible and visual alarm and immediately uploads the alarm data. The main control chip has a circular storage area in its built-in Flash, which can store the most recent 1000 timestamped monitoring data. When the NB-IoT network is interrupted, the data is temporarily stored locally and automatically re-uploaded after the network is restored.

[0018] The current sensor is a JXK-10VD current transmitter, used for non-contact current measurement, with a measurement range of 0-100A and an accuracy of ±0.5%.

[0019] When the RS485 conversion circuit receives the differential signal output from the sensor, lines A and B, it enters the transceiver. The internal comparator of the chip converts the voltage difference between lines A and B into a TTL level: when line A is higher than line B, RO outputs high; when line A is lower than line B, RO outputs low. The converted signal is sent from the RO pin to the main control PA3. When transmitting, the TTL signal output by the main control PA2 is sent to the DI pin. At the same time, the main control PA1 controls RE / DE to be high, putting the chip in transmit mode. The DI level controls the driver to convert lines A and B into differential signals and output them to the sensor, thus completing the mutual conversion between level and differential signals.

[0020] The temperature sensor is a DS18B20 temperature sensor, which is attached to the cable connector or near the grounding wire. The temperature signal it outputs is transmitted to the main control chip after being converted from digital to analog within the temperature sensor.

[0021] The NB-IoT communication module uses a GA7 module, supports multi-band communication, operates in the frequency range of 700MHz-2200MHz, has a maximum transmission distance of 10 kilometers, and supports encrypted data transmission.

[0022] The display unit uses a 0.96-inch OLED display screen and is connected to the main control chip via an I2C interface.

[0023] The power management module includes a solar panel, a lithium battery, and a power management circuit: the solar panel converts light energy into electrical energy and stores it in the lithium battery, and the power management circuit realizes efficient distribution of electrical energy and overcharge and over-discharge protection.

[0024] 3. Beneficial effects:

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] Simplified wiring and easy installation: Using NB-IoT wireless communication, there is no need to lay signal cables, which significantly reduces construction difficulty and maintenance costs, making it particularly suitable for complex environments such as cable trenches and tunnels.

[0027] Long transmission distance and wide coverage: NB-IoT technology has wide coverage and strong penetration characteristics, with a maximum transmission distance of up to 10 kilometers. It supports stable data transmission in complex environments and meets the needs of remote centralized monitoring.

[0028] Low power consumption and support for long-term operation: By adopting a low-power main control chip and NB-IoT module, combined with a solar and lithium battery power supply solution, the device can achieve long-term, stable and self-sustaining operation in the absence of an external power source.

[0029] High integration and controllable cost: The main control chip has a built-in analog-to-digital conversion module, eliminating the need for external independent analog-to-digital conversion circuits and complex signal conditioning circuits, simplifying hardware design and reducing system cost and failure rate.

[0030] Multi-parameter integrated monitoring enhances safety: Simultaneous monitoring of cable grounding circulation current and operating temperature, with the two parameters complementing each other, allows for a more comprehensive and accurate assessment of cable insulation status and potential faults.

[0031] Supports remote configuration and alarms: Users can remotely adjust the device's operating parameters and upgrade the firmware through the remote monitoring center; when abnormal circulation or temperature occurs, the system can simultaneously trigger a local alarm and push alarm information to mobile terminals or PCs through the cloud platform.

[0032] Strong anti-interference capability and reliable data security: It adopts RS485 differential communication and NB-IoT data encryption transmission, which effectively resists electromagnetic interference in industrial sites and ensures the accuracy and security of data transmission. Attached Figure Description

[0033] Figure 1 This is a system structure diagram disclosed in this invention.

[0034] Figure 2 This is the circuit schematic diagram disclosed in this invention. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific implementation examples.

[0036] like Figure 1As shown in the embodiment, a wireless cable grounding loop current acquisition device based on NB-IoT is provided, including: a current sensor module, an RS485 conversion circuit, a main control chip, a display unit, a temperature acquisition module, an NB-IoT communication module, and an alarm unit. The current acquisition module is connected to the main control chip via the RS485 conversion circuit. The main control chip is connected to the display unit, the alarm unit, the temperature acquisition module, and the NB-IoT communication module. The NB-IoT communication module wirelessly communicates with the cloud platform monitoring terminal via a base station.

[0037] The main control chip is used to control the operation of the entire device, including data acquisition, processing and transmission.

[0038] The RS485 conversion circuit enables bidirectional digital communication between the main control chip and the current sensor.

[0039] The current acquisition module acquires the cable grounding circulating current signal in real time through the current sensor.

[0040] The temperature sensor is attached to the cable joint or near the grounding wire to collect the operating temperature of the cable.

[0041] The NB-IoT communication module is used to transmit the processed data to the remote monitoring center through the message forwarding function of the cloud platform.

[0042] The display unit is used to display the circulation value and temperature value in real time.

[0043] The power management module provides power support for the current sensor, temperature sensor, main control chip, and NB-IoT communication module.

[0044] In one embodiment, the current acquisition module uses a JXK-10VD current transmitter with a measurement range of 0-100A, an accuracy of ±0.5%, and a response time ≤1μs. This sensor has an open structure and can be clamped onto the cable grounding wire for non-contact measurement. An RS485 conversion circuit enables bidirectional digital communication between the main control chip and the current sensor. During reception, the differential signal (A and B lines) output by the sensor enters transceiver U17 (TP8485E-SR). The chip's internal comparator converts the voltage difference between A and B into a TTL level: when A is higher than B, RO outputs high (3.3V); when A is lower than B, RO outputs low (0V). The converted signal is sent from the RO pin to the main control PA3 (RXD). During transmission, the TTL signal output by the main control PA2 (TXD) is sent to the DI pin. Simultaneously, the main control PA1 controls RE / DE to be high, putting the chip in transmit mode. The DI level controls the driver to convert the A and B lines into differential signals and output them to the sensor. This completes the mutual conversion between level and differential signals.

[0045] In one embodiment, the temperature acquisition module uses a DS18B20 temperature sensor with a temperature measurement range of -55℃ to 150℃ and an accuracy of ±0.5℃. The sensor is attached to the metal surface of the cable connector or grounding wire, and thermal coupling is enhanced by thermally conductive silicone grease. The main control chip has a built-in 12-bit analog-to-digital converter with a reference voltage of 3.3V and a sampling frequency of 1Hz. The temperature value is obtained through software mean filtering (averaging after 10 consecutive samples and removing extreme values).

[0046] In one embodiment, the main control chip is an STM32F103C8T6, operating at a frequency of 72MHz, with 64KB of Flash and 20KB of RAM. The main control chip compares the collected circulating current value I and temperature value T with preset thresholds: Circulating current threshold: Under normal operating conditions, the grounding circulating current is typically less than 20A. In this embodiment, the warning threshold is set to 30A, and the alarm threshold to 50A. Temperature threshold: The warning threshold is 70℃, and the alarm threshold is 85℃. If I < 30A and T < 70℃, it is considered normal; if 30A ≤ I < 50A or 70℃ ≤ T < 85℃, a warning is triggered, and the device issues intermittent audible and visual alarms through the alarm unit, while simultaneously sending warning information to the monitoring center; if I ≥ 50A or T ≥ 85℃, an alarm is triggered, and the alarm unit issues continuous audible and visual alarms and immediately uploads alarm data. A circular storage area is allocated in the main control chip's built-in Flash, which can store the most recent 1000 timestamped monitoring data entries. When the NB-IoT network is interrupted, the data is temporarily stored locally and automatically retransmitted after the network is restored.

[0047] In one embodiment, the NB-IoT communication module uses a GA7 module, supporting B5 / B8 / B20 frequency bands, operating at 3.1V–4.2V, and consuming approximately 5μA in sleep mode. The module connects to the main control chip via a serial port. The main control chip controls the module's network access, data transmission and reception, and sleep / wake-up via AT commands. The module connects to the operator's NB-IoT base station and sends data to the Alibaba Cloud platform using the UDP protocol. The cloud platform pushes the data to the server in the remote monitoring center via message forwarding. Users can view real-time data, historical curves, and alarm records via a web interface or mobile app. The module supports DTLS encrypted transmission to ensure data security.

[0048] In one embodiment, the display unit uses a 0.96-inch OLED display (128×64) and is connected to the main control chip via an I2C interface to display the circulating current value and temperature value in real time.

[0049] In one embodiment, the power management module consists of a solar panel (24V / 10W), a lithium iron phosphate battery (24V / 6Ah), and a power management circuit. The solar panel is connected to the charging management chip CN3791 via a reverse protection diode to provide maximum power point tracking charging for the battery. The battery output is converted to 5V by a DC-DC step-down chip LM2596HVS-ADJ / TR, and then to 3.3V by an LDO chip TPSPX3819M5-L-3-3. The 5V supplies power to the display unit, NB-IoT module, and RS485 conversion circuit; the 3.3V supplies power to the main control chip and temperature sensor.

[0050] Best Practices

[0051] like Figure 2As shown, the connection method of each module is as follows: The STM32F103C8T6 main control chip is the core, and its power supply is 3.3V, obtained from an external 24V power supply through two stages of conversion: First, the 24V power supply is sent to the VIN pin of the LM2596HVS-ADJ DC-DC converter (U43) through the CN2 interface (HT396R-3.96-2P, pin 1 connected to 24V, pin 2 grounded), in conjunction with inductor L1 (33µH), diode D9 (SS34), and output filter. The 5V voltage is generated by capacitors C72 (10µF), C73 (100nF), and C44 (680µF). This 5V is output through the CN3 interface and also serves as the input of the subsequent LDO. The 5V voltage is then input through the VIN pin of the TPSX3819M5-L-3-3 type LDO (U42). Its EN pin is pulled up to VIN through a 10kΩ resistor to enable it. The VOUT pin outputs 3.3V, which is filtered by C70 (10µF) and then used to power the main control chip and other 3.3V modules. The main control chip's power supply pins, such as VDD3 and VDD2, are all connected to 3.3V. A 100nF decoupling capacitor (C5, C12, C16, etc.) is placed near each power supply pin. The VSS_3 and VSSA pins are grounded. The reset pin, NRST, is pulled up to 3.3V via a 10kΩ resistor. The main clock uses an 8MHz crystal oscillator (X1) connected to PD0-OSC_IN and PD1-OSC_OUT, and is grounded via 20pF capacitors (C1, C2) respectively. The RTC clock uses a 32.768kHz crystal oscillator connected to PC14-OSC32_IN and PC15-OSC32_OUT, and is grounded via a 10pF capacitor. The BOOT0 pin is pulled down to ground via a 10kΩ resistor to select booting from Flash. The current sensor is powered by 24V, and its RS485 signal is transmitted to the main control chip through an RS485 conversion circuit: the RS485 conversion circuit model is TP8485E-SR (U17), its VCC pin is connected to 3.3V and connected to a 100nF decoupling capacitor C36, and the GND pin is grounded; the A / Y pin is connected to pin 1 of the bus terminal CN1 (HT396R-3.96-2P) through a 22Ω resistor R27, and is simultaneously pulled up to 3.3V through a 4.7kΩ resistor R31; the B / Z pin is connected to a 22Ω resistor R31 through a 100nF decoupling capacitor C36. Resistor R28 is connected to pin 2 of CN1, and is pulled down to ground through resistor R29 and pulled up to 3.3V through resistor R30. The bus port is also protected by SMBJ15CA TVS diodes D5 and D8 and resettable fuses F2 and F3. The receive output pin RO of U3 is connected to PA3 (RXD) of the main controller, the transmit input pin DI is connected to PA2 (TXD) of the main controller, and the direction control pins RE and DE are shorted and connected to PA4 pin of the main controller, so that the main controller controls the transmit and receive direction.The NB-IoT module connects via interfaces H44 and H45. The 5V power supply and GND are connected to the module's power supply, respectively. The serial communication lines connect the main controller's PB10 (USART3_TX) to the module's RX and PB11 (USART3_RX) to the module's TX. The OLED display module uses an I²C interface. Its GND is grounded, 3.3V is connected to the power supply, the SCL line is connected to the main controller's PB9 (I2C1_SCL), and the SDA line is connected to the main controller's PB8 (I2C1_SDA). External 4.7kΩ pull-up resistors are required to bring the SCL and SDA lines to 3.3V. The DS18B20 temperature sensor's VDD pin is connected to 3.3V, its DQ pin is connected to the main controller's PA11 and externally pulled up to 3.3V with a 4.7kΩ resistor, and its GND pin is grounded. The program download and debugging interface uses the SWD method, implemented through a 4-pin connector H5: pin 1 connects to 3.3V, pin 2 connects to the main controller's PA13 (SWDIO), pin 3 connects to the main controller's PA14 (SWCLK), and pin 4 connects to GND. All module grounding pins are uniformly connected to a common ground plane to ensure a complete ground loop.

Claims

1. A wireless cable grounding loop current acquisition device based on NB-IoT, characterized in that: It includes a current sensor module, an RS485 conversion circuit, a main control chip, a display unit, a temperature acquisition module, an NB-IoT communication module, and a power management module. The current acquisition module is connected to the main control chip through the RS485 conversion circuit. The main control chip is connected to the display unit, the temperature acquisition module, and the NB-IoT communication module respectively. The NB-IoT communication module communicates wirelessly with the cloud platform monitoring terminal through the base station. The main control chip is used to control the operation of the entire device, including data acquisition, processing and transmission; The RS485 conversion circuit enables bidirectional digital communication between the main control chip and the current sensor. The current acquisition module acquires the cable grounding circulating current signal in real time through the current sensor; The temperature sensor is attached near the cable joint or grounding wire to collect the cable's operating temperature. The NB-IoT communication module is used to transmit the processed data to the remote monitoring center through the message forwarding function of the cloud platform. The display unit is used to display the circulation value and temperature value in real time. The power management module provides power support for the current sensor, temperature sensor, main control chip, and NB-IoT communication module.

2. The NB-IoT-based wireless cable grounding loop current acquisition device as described in claim 1, characterized in that: The main control chip is an STM32F103C8T6 with a working frequency of 72MHz. The main control chip is connected to the NB-IoT communication module through a UART interface and to the current sensor through an RS485 interface. The built-in analog-to-digital converter module directly acquires the analog output signal of the temperature sensor.

3. The NB-IoT-based wireless cable grounding loop current acquisition device as described in claim 2, characterized in that: It has built-in Flash and RAM for local data storage and supports remote configuration and firmware upgrades. Users can adjust the device's operating parameters through a remote monitoring center.

4. The NB-IoT-based wireless cable grounding loop current acquisition device as described in claim 3, characterized in that: It also includes an alarm unit, which is connected to the main control chip. The specific working method of the alarm unit is as follows: The main control chip compares the collected circulating current value I and temperature value T with preset thresholds: Circulating current threshold: Under normal operating conditions, the grounding circulating current is usually less than 20A. Let the warning threshold be 30A and the alarm threshold be 50A. Temperature threshold: The warning threshold is 70℃ and the alarm threshold is 85℃. If I < 30A and T < 70℃, it is judged as normal; if 30A ≤ I < 50A or 70℃ ≤ T < 85℃, a warning is triggered, and the device issues an intermittent audible and visual alarm through the alarm unit, and at the same time sends a warning message to the monitoring center; if I ≥ 50A or T ≥ 85℃, an alarm is triggered, and the alarm unit issues a continuous audible and visual alarm and immediately uploads the alarm data. The main control chip has a circular storage area in its built-in Flash, which can store the most recent 1000 timestamped monitoring data. When the NB-IoT network is interrupted, the data is temporarily stored locally and automatically re-uploaded after the network is restored.

5. The NB-IoT-based wireless cable grounding loop current acquisition device as described in claim 4, characterized in that: The current sensor is a JXK-10VD current transmitter, used for non-contact current measurement, with a measurement range of 0-100A and an accuracy of ±0.5%.

6. The NB-IoT-based wireless cable grounding loop current acquisition device as described in claim 4, characterized in that: When the RS485 conversion circuit receives the differential signal output from the sensor, lines A and B, it enters the transceiver. The internal comparator of the chip converts the voltage difference between lines A and B into a TTL level: when line A is higher than line B, RO outputs high; when line A is lower than line B, RO outputs low. The converted signal is sent from the RO pin to the main control PA3. When transmitting, the TTL signal output by the main control PA2 is sent to the DI pin. At the same time, the main control PA1 controls RE / DE to be high, putting the chip in transmit mode. The DI level controls the driver to convert lines A and B into differential signals and output them to the sensor, thus completing the mutual conversion between level and differential signals.

7. The NB-IoT-based wireless cable grounding loop current acquisition device as described in claim 6, characterized in that: The temperature sensor is a DS18B20 temperature sensor, which is attached to the cable connector or near the grounding wire. The temperature signal it outputs is transmitted to the main control chip after being converted from digital to analog within the temperature sensor.

8. The NB-IoT-based wireless cable grounding loop current acquisition device as described in claim 7, characterized in that: The NB-IoT communication module uses a GA7 module, supports multi-band communication, operates in the frequency range of 700MHz-2200MHz, has a maximum transmission distance of 10 kilometers, and supports encrypted data transmission.

9. The NB-IoT-based wireless cable grounding loop current acquisition device as described in claim 8, characterized in that: The display unit uses a 0.96-inch OLED display screen and is connected to the main control chip via an I2C interface.

10. The NB-IoT-based wireless cable grounding loop current acquisition device as described in claim 9, characterized in that: The power management module includes a solar panel, a lithium battery, and a power management circuit: the solar panel converts light energy into electrical energy and stores it in the lithium battery, and the power management circuit realizes efficient distribution of electrical energy and overcharge and over-discharge protection.

Images