Transformer winding direct current resistance tester with low power consumption and wireless transmission

Abstract

The invention relates to the technical field of power equipment detection, and discloses a low-power-consumption wireless transmission transformer winding direct-current resistance tester, which comprises a test acquisition unit used for acquiring and converting a direct-current resistance signal of a transformer winding in a sampling period and entering a first low-power-consumption state in a non-sampling period; the data processing and control unit is used for controlling start and stop of the test acquisition unit, processing resistance signals, managing self power consumption through operation optimization and task scheduling, and entering a second low power consumption state in a data processing gap; the wireless communication unit is used for responding to an instruction of the data processing and control unit, remotely sending the processed data in a data sending period and entering a third low-power-consumption state after the data is sent; and the collaborative energy supply unit is used for supplying power to the test acquisition unit, the data processing and control unit and the wireless communication unit. The system greatly reduces the maintenance frequency and cost, and is especially suitable for long-term and unattended on-line monitoring application.

Description

Technical Field

[0001] This invention relates to the field of power equipment testing technology, specifically to a low-power wireless transmission transformer winding DC resistance tester. Background Technology

[0002] DC resistance testing of transformer windings is a crucial method for identifying defects such as inter-turn short circuits, loose connections, or poor contact. Traditional testing instruments often employ wired connections and manual on-site readings, which are inefficient and unsuitable for long-term online monitoring scenarios. Existing wireless testing instruments generally suffer from high power consumption, short battery life, measurement accuracy highly susceptible to ambient temperature fluctuations, and unreliable wireless transmission in complex environments. The root cause lies in the lack of coordinated low-power design across hardware, software, and power management at the system level, preventing the devices from achieving stable operation for several years with limited battery capacity. Therefore, there is an urgent need for a DC resistance tester that balances low power consumption, high accuracy, wireless long-distance transmission, and long battery life. Summary of the Invention

[0003] This invention provides a low-power wireless transmission transformer winding DC resistance tester. Through the coordinated design of hardware architecture, software strategy and power management, it achieves ultra-low power operation, high-precision testing and reliable remote wireless data transmission.

[0004] This invention is achieved through the following technical solution:

[0005] A low-power wireless transmission transformer winding DC resistance tester, comprising:

[0006] The test acquisition unit consists of a low-power signal conditioning circuit and a high-precision ADC. It is used to acquire and convert the DC resistance signal of the transformer winding during the sampling period and enter the first low-power state during the non-sampling period.

[0007] The data processing and control unit is connected to the test acquisition unit and has a built-in low-power microprocessor and embedded software. It is used to control the start and stop of the test acquisition unit, process resistance signals, and manage its own power consumption through calculation optimization and task scheduling. It enters a second low-power state during data processing intervals.

[0008] The wireless communication unit is connected to the data processing and control unit, adopts a low-power wide area network protocol, and is used to respond to the instructions of the data processing and control unit, remotely transmit the processed data during the data transmission period, and enter the third low-power state after the transmission is completed.

[0009] The collaborative power supply unit uses a low self-discharge rate battery to power the test acquisition unit, data processing and control unit and wireless communication unit;

[0010] The low-power state of the test acquisition unit, data processing and control unit, and wireless communication unit is controlled collaboratively by the data processing and control unit, so that the tester alternates between working and sleeping periods in time, thereby achieving long-term battery life based on a preset power consumption model.

[0011] As an optimization, the computation optimization and task scheduling performed by the data processing and control unit include: replacing the polling mechanism with an interrupt-driven mechanism; compressing function stack overhead through macro definitions; and a CPU load optimization method, which includes pre-storing frequently used computation results in non-volatile memory and enabling table lookup, prioritizing the use of data types with lower computational overhead than floating-point numbers, and replacing floating-point operations with fixed-point or fractional operations, wherein the data types include integers or fixed-point numbers.

[0012] As an optimization, the collaborative power supply unit adopts a lithium thionyl chloride battery, whose capacity design ensures that the average operating current of the tester is ≤0.5mA, the continuous working life is ≥6 years, and the battery weight is ≤120g under the preset sampling interval.

[0013] As an optimization, the preset sampling interval is ≤5 minutes.

[0014] As an optimization, the wireless communication unit adopts the LoRa or NB-IoT communication protocol, with a point-to-point communication distance of ≥2km, an operating power consumption of ≤10mW, and a power consumption of ≤1μA in the third low power state.

[0015] As an optimization, the test acquisition unit also includes an environmental parameter sensing and compensation module, which is used to compensate the acquired DC resistance signal in real time to eliminate measurement errors caused by environmental factors.

[0016] As an optimization, the data processing and control unit is also equipped with an adaptive task scheduler, which can dynamically adjust the sampling frequency of the test acquisition unit and the data transmission frequency of the wireless communication unit according to the changing trend of the electrical state of the winding under test.

[0017] As an optimization, the collaborative power supply unit also integrates a battery health status monitoring circuit, which is used to assess the remaining power and lifespan in real time, and to link with the data processing and control unit to trigger a low-power maintenance strategy when the power is insufficient.

[0018] As an optimization, the wireless communication unit supports a link self-recovery transmission mechanism, which can automatically attempt to re-establish the connection and resend data when a communication link interruption or data packet loss is detected.

[0019] As an optimization, the tester adopts a modular structure with split-cavity shielding. The test acquisition unit, data processing and control unit, wireless communication unit and collaborative power supply unit are placed in independent electromagnetic shielding cavities and are electrically connected through board-to-board connectors.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] This invention employs a system-level collaborative low-power design integrating hardware, software, communication, and power supply, enabling the tester to remain in various depths of sleep mode most of the time, with an average operating current controlled to ≤0.5mA. Combined with a low self-discharge rate lithium thionyl chloride battery, it achieves a continuous working life of at least 6 years with sampling intervals of ≤5 minutes, significantly reducing maintenance frequency and costs, making it particularly suitable for long-term, unattended online monitoring applications.

[0022] This invention employs a high-precision ADC and integrates an environmental parameter sensing and compensation module, which can automatically compensate for temperature drift and other factors in real time, effectively eliminating measurement errors introduced by environmental factors and ensuring the accuracy and comparability of data under different seasons and climate conditions.

[0023] The cavity-shielded modular structure in this invention effectively isolates the mutual interference between analog signals, digital circuits, and radio frequency circuits, providing a clean environment for the acquisition of weak signals at the front end and ensuring measurement accuracy from a physical perspective.

[0024] The adaptive task scheduler built into this invention can dynamically adjust the operating frequency according to the winding status. When the equipment is stable, it automatically enters a slow-paced monitoring mode to further save energy. When the status is abnormal, it immediately resumes normal monitoring, thus achieving a balance between intelligent power consumption management and status response sensitivity.

[0025] The wireless communication unit of this invention supports a link self-recovery transmission mechanism and a data packet splitting strategy, which can effectively cope with the complex electromagnetic environment and network instability on site, ensuring that monitoring data is reliably and completely transmitted to the remote terminal and avoiding data loss.

[0026] The entire system in this invention adopts a high-density integrated design, with the power module weighing ≤120g, making the overall device compact and lightweight, and easy to install and deploy on-site. The modular design also facilitates production, maintenance, and functional upgrades. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0028] Figure 1This is a schematic diagram of the module composition and connection relationship of the tester of this invention. (The diagram should clearly indicate the four core units: test acquisition unit, data processing and control unit, wireless communication unit, and collaborative power supply unit, with arrows indicating power supply and data flow). Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0030] This embodiment 1 provides a low-power wireless transmission transformer winding DC resistance tester, such as... Figure 1 As shown, the core of this tester lies in the coordinated work of four units to achieve dynamic power consumption management that alternates between working and sleep periods over time.

[0031] The test acquisition unit's low-power signal conditioning circuit can be composed of a low-power instrumentation amplifier and a low-bias-current operational amplifier, which amplifies and filters the weak voltage signal on the winding. A 24-bit high-precision ADC can be selected. Type-A ADCs, such as the ADS124S08, offer both low-power and shutdown modes while maintaining accuracy; this is the first low-power state. The unit's power supply and enable pins are entirely controlled by the data processing and control unit via GPIO ports, and it is only awakened when sampling is required.

[0032] Data processing and control unit: Its low-power microprocessor is preferably an ARM Cortex-M series MCU (microprocessor), such as the STM32L4 series, which has multiple low-power operating modes (Sleep, Stop, Standby). The embedded software is key to achieving collaborative control. After system power-on initialization, the main program hands over control to a task scheduler based on a real-time operating system (RTOS) or a bare-metal state machine. This scheduler strictly manages the operation and sleep of each unit according to a preset timeline or events.

[0033] 1. Upon reaching the sampling time, wake up the test acquisition unit, complete the data acquisition, and immediately turn it off (enter the first low-power state).

[0034] 2. After the MCU processes the data (working period), if there is no communication task after processing, it will enter the Stop mode (second low power state).

[0035] 3. When the communication time is reached or the data processing is completed and needs to be reported immediately, the MCU is woken up and instructs the wireless communication unit to work.

[0036] The wireless communication unit implements either the LoRaWAN or NB-IoT protocol for its low-power wide-area network (LPWAN). Module models can be LoRa modules based on the SX1262 or Quectel BC95 NB-IoT modules. When these modules are not activated, their third low-power state is Deep Sleep mode, with power consumption as low as approximately 1μA. Communication is entirely event-driven, controlled by the data processing and control unit via UART sending AT commands or the SPI interface. Of course, the wireless communication unit can also use other protocols specifically designed for LPWAN, such as Sigfox. Any event-driven, intermittent operating mode falls within the scope of this invention.

[0037] Collaborative power supply unit: The low self-discharge rate battery is specifically implemented as an ER14505M type lithium thionyl chloride battery, with a nominal capacity of up to 2400mAh and an extremely low self-discharge rate (annual self-discharge rate <1%).

[0038] Collaborative Control and Long-Term Battery Life: The preset power consumption model is established by accurately calculating the current consumption and time proportion of each unit during the working and sleep periods. For example, assuming a working cycle is 5 minutes, with 2 seconds for data acquisition and processing, 3 seconds for communication, and the remaining 295 seconds in various sleep states, the average operating current can be obtained by multiplying the current of each state by the time and averaging the results. By selecting a battery of appropriate capacity, the theoretical battery life can be calculated, thus achieving long-term battery life based on the preset power consumption model.

[0039] In some embodiments, the specific software implementation of the computation optimization and task scheduling is as follows:

[0040] Interrupt-driven mechanism replaces polling: All peripherals (such as ADC conversion completion, timer timeout, and communication module response) are configured to be interrupt-triggered. The MCU is in sleep mode most of the time, and is woken up by an interrupt event to execute the corresponding interrupt service function, completely avoiding the power waste of the CPU continuously polling the flag bit.

[0041] Macro definitions reduce function stack overhead: For short and frequently called functions, macro definitions (#define) are used to expand the function during the preprocessing stage, avoiding the overhead of pushing, jumping and popping from the stack during function calls, thus reducing CPU instruction cycles and memory accesses.

[0042] CPU load optimization methods:

[0043] Lookup table method: The input-output relationships of complex mathematical operations (such as calibration coefficients and nonlinear compensation values) are pre-calculated and stored in the MCU's Flash memory. During actual calculations, the results are directly retrieved through the index, avoiding the huge overhead of real-time calculations.

[0044] Prioritize data types with lower computational overhead compared to floating-point numbers: In embedded software, explicitly define all variables and avoid using float or double unless absolutely necessary. Algorithms such as resistance calculation and temperature compensation use int32_t or int16_t integer data and preserve decimal precision through fixed-point arithmetic techniques (such as Q format). For example, amplifying the resistance value by 1000 times and storing and calculating it using integers effectively reduces the computational burden on the MCU.

[0045] Replacing floating-point arithmetic with fixed-point or fractional arithmetic: This invention abandons the traditional floating-point arithmetic library. Specifically, it uses Q-format fixed-point numbers to handle decimal arithmetic. For example, an int32_t type variable is defined and treated as Q15 format (i.e., the lower 16 bits represent the decimal part). For resistance value calculation... ,in (Reference voltage) (Amplifier gain) All constants, including the constant current source current, are pre-converted to integers in Q15 format. The entire calculation process is completed through integer multiplication and shift operations, completely avoiding time-consuming floating-point software library calls in the compiler, thus increasing the calculation speed several times and significantly reducing power consumption.

[0046] To further improve the accuracy of the lookup table method, this invention combines it with a linear interpolation algorithm. Specifically, this invention pre-stores a dense lookup table based on temperature-compensation coefficients in Flash memory. For example, from -40°C to +105°C, in 1°C increments, 146 compensation coefficients K are pre-stored. Actual temperature When the temperature is 23.4°C, the system does not round down to 23°C or 24°C. Instead, it locates two compensation coefficients, K23 and K24, corresponding to 23°C and 24°C, and then calculates the accurate compensation coefficient at 23.4°C using linear interpolation: K = K23 + (K24 - K23) * 0.4. This method approximates the accuracy of complex function operations with extremely low computational overhead (requiring only one multiplication, one addition, and one subtraction), representing a perfect combination of lookup table method and lightweight computation.

[0047] This strategy of dense table lookup combined with linear interpolation achieves accuracy close to that of complex function models with negligible incremental computational overhead, and is a key design for balancing high accuracy and low power consumption.

[0048] In some embodiments, the co-powered unit uses the ER14505M battery (approximately 2400mAh capacity). Based on the aforementioned power consumption model, when the preset sampling interval is ≤5 minutes, the calculated average operating current of the system can be controlled at around 0.45mA. According to the formula: battery life (hours) = battery capacity (mAh) / average current (mA), the theoretical battery life is approximately 2400 / 0.45≈5333 hours, or approximately 222 days. However, considering the low self-discharge characteristics and high capacity utilization rate of lithium thionyl chloride batteries at low discharge rates, their actual effective lifespan far exceeds this theoretical calculation. Given that lithium thionyl chloride batteries can achieve nearly 100% depth of discharge and extremely low self-discharge rate under microampere discharge conditions, their actual effective lifespan is usually more than 10 times the theoretical value. Combining the data provided by the battery manufacturer and accelerated aging tests, it can be verified that their continuous working life is ≥6 years. The battery weighs approximately 18g, and the total weight of the entire power module (including protection circuit and PCB) can be controlled at ≤120g.

[0049] In some embodiments, if the wireless communication unit adopts the LoRa scheme and uses the SX1262 chip, its transmit current (+14dBm) is approximately 35mA and its receive current is approximately 6mA, but its average operating time is extremely short. In deep sleep mode, its power consumption is ≤1.5μA. In open suburban environments, using the 868MHz or 470MHz frequency band, its point-to-point communication distance is ≥2km. Its RF output power can be configured via software; in practical applications, it can be set to 10mW (+10dBm) to further reduce power consumption, thus meeting the design requirement of ≤10mW operating power consumption.

[0050] In some embodiments, the environmental parameter sensing and compensation module is specifically an integrated high-precision digital temperature sensor, such as TI's TMP117, on the PCB of the test acquisition unit. This sensor is also controlled intermittently by an MCU. The compensation process does not use an idealized single temperature coefficient formula, but rather employs a compensation model based on dual-parameter segmented calibration to address the varying purity of winding materials (such as copper) and the complexity of actual operating conditions.

[0051] The compensation process is as follows:

[0052] 1. Calibration Data Acquisition: Before leaving the factory, the tester and standard winding are calibrated at multiple points in a temperature chamber. The measured resistance value of the tester and the standard resistance value are recorded at at least three key temperature points (e.g., low temperature -10°C, normal temperature 25°C, and high temperature 60°C).

[0053] 2. Model Parameter Calculation: Based on calibration data, specific and optimal compensation parameters are calculated for each test instrument. The model uses the following formula:

[0054] ; For the corrected resistance, For actual measured resistance, The current temperature. For reference temperature, , These are the first and second-order temperature coefficients obtained by fitting using the least squares method. This second-order model can more accurately describe the nonlinear variation characteristics of the material's resistivity over the entire operating temperature range.

[0055] 3. Online compensation calculation: During field operation, the microprocessor reads the current temperature. and measured resistance Then, the dedicated parameters stored in Flash are called. and The above second-order formula is then used for calculation. To optimize calculation speed, the formula... The term is implemented through a combination of multiplication and table lookup. The calculation result is used as a whole compensation factor K. The entire process is still completed within the fixed-point system, achieving a balance between high precision and low overhead.

[0056] Compared to the traditional first-order linear model, this second-order compensation model can reduce the temperature-induced resistance measurement error by an order of magnitude over a wide temperature range of -40°C to +85°C, optimizing it from the usual ±1% to within ±0.1%, thus achieving high-precision measurement in complex field environments.

[0057] In some embodiments, the adaptive task scheduler is an algorithm module embedded in the main program of the data processing and control unit. Its working principle is as follows: the MCU records multiple historical resistance measurements and calculates their rate of change (…). When the system detects that the rate of change of the resistance value is less than a preset stability threshold over several consecutive cycles, it determines that the winding state has stabilized and automatically adjusts the timer parameters to gradually reduce the sampling and transmission frequency from 5 minutes / time to 30 minutes / time or even longer. Conversely, when the system detects that the deviation of the resistance value from the historical value exceeds a preset threshold (e.g., 0.5%), or the rate of change increases sharply, it immediately resumes the high-frequency sampling mode. This significantly reduces average power consumption while ensuring data validity.

[0058] In some embodiments, the battery health monitoring circuit integrated into the collaborative power supply unit can specifically employ a chip with integrated coulomb counter functionality, such as MAXIM's MAX17048. This chip calculates and reports the remaining power and health status in real time by monitoring the battery voltage and the current through a precision sampling resistor. When the data processing and control unit reads that the power level is below the 20% threshold via I2C, a low-power maintenance strategy is triggered, for example: forcibly switching the sampling interval to 1 hour / time, shutting down the power supply of non-core sensors, and minimizing the transmission power of wireless communication. Simultaneously, an alarm can be sent to a remote platform via a wireless beacon, indicating the need for maintenance.

[0059] In some embodiments, the link self-recovery transmission mechanism is jointly implemented by the wireless communication unit and the data processing and control unit. The specific process is as follows: After the MCU sends data via AT commands, it waits for a network acknowledgment signal from the module. If no acknowledgment is received within the set timeout period, or if the module reports a transmission failure, the MCU will not immediately retransmit. Instead, it will first instruct the communication module to perform a network reattachment process (such as re-searching for and registering the network), and then attempt to retransmit the data. For longer data packets, the MCU will divide them into multiple smaller packets conforming to the MTU (Maximum Transmission Unit), send them sequentially, and acknowledge each smaller packet to ensure the reliability of data transmission.

[0060] In some embodiments, the modular structure with partitioned shielding is physically implemented as follows: the interior of the instrument's outer shell is divided into four independent cavities by metal partitions.

[0061] Test acquisition unit cavity: A copper shield is used to isolate analog small signal circuits from digital circuits and radio frequency interference.

[0062] Data processing and control unit cavity: This is the core digital circuit area.

[0063] Wireless communication unit cavity: This is the radio frequency circuit area, and the antenna interface is located outside the cavity.

[0064] Collaborative power supply unit cavity: housing the battery and power management circuitry.

[0065] Each unit circuit is fabricated on a small, independent PCB. These PCBs are stacked or plugged together via board-to-board connectors, achieving modularity in electrical connections and physical structure, which facilitates production, testing, and subsequent maintenance and replacement.

[0066] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low power consumption wireless transmission transformer winding DC resistance tester characterized by, include: The test acquisition unit consists of a low-power signal conditioning circuit and a high-precision ADC. It is used to acquire and convert the DC resistance signal of the transformer winding during the sampling period and enter the first low-power state during the non-sampling period. The data processing and control unit is connected to the test acquisition unit and has a built-in low-power microprocessor and embedded software. It is used to control the start and stop of the test acquisition unit, process resistance signals, and manage its own power consumption through calculation optimization and task scheduling. It enters a second low-power state during data processing intervals. The wireless communication unit is connected to the data processing and control unit, adopts a low-power wide area network protocol, and is used to respond to the instructions of the data processing and control unit, remotely transmit the processed data during the data transmission period, and enter the third low-power state after the transmission is completed. The collaborative power supply unit uses a low self-discharge rate battery to power the test acquisition unit, data processing and control unit and wireless communication unit; The low-power state of the test acquisition unit, data processing and control unit, and wireless communication unit is controlled collaboratively by the data processing and control unit, so that the tester alternates between working and sleeping periods in time, thereby achieving long-term battery life based on a preset power consumption model.

2. The low power consumption wireless transmission transformer winding DC resistance tester according to claim 1, characterized in that, The computation optimization and task scheduling performed by the data processing and control unit include: replacing the polling mechanism with an interrupt-driven mechanism; compressing function stack overhead through macro definitions; and a CPU load optimization method, which includes pre-storing frequently used computation results in non-volatile memory and enabling table lookup, prioritizing the use of data types with lower computational overhead than floating-point numbers, and replacing floating-point operations with fixed-point or fractional operations, wherein the data types include integers or fixed-point numbers.

3. The low power consumption wireless transmission transformer winding DC resistance tester of claim 1, wherein, The collaborative power supply unit uses a lithium thionyl chloride battery. Its capacity design ensures that the average operating current of the tester is ≤0.5mA at the preset sampling interval, the continuous working life is ≥6 years, and the battery weight is ≤120g.

4. The low power consumption wireless transmission transformer winding DC resistance tester of claim 3, wherein, The preset sampling interval is ≤5 minutes.

5. The low power consumption wireless transmission transformer winding DC resistance tester of claim 1, wherein, The wireless communication unit adopts LoRa or NB-IoT communication protocol, with a point-to-point communication distance of ≥2km, operating power consumption of ≤10mW, and power consumption of ≤1μA in the third low power state.

6. The low power consumption wireless transmission transformer winding DC resistance tester of claim 1, wherein, The test acquisition unit also includes an environmental parameter sensing and compensation module, which is used to compensate the acquired DC resistance signal in real time to eliminate measurement errors caused by environmental factors.

7. The low power consumption wireless transmission transformer winding DC resistance tester of claim 1, wherein, The data processing and control unit is also equipped with an adaptive task scheduler, which can dynamically adjust the sampling frequency of the test acquisition unit and the data transmission frequency of the wireless communication unit according to the electrical state change trend of the tested winding.

8. The low power consumption wireless transmission transformer winding DC resistance tester of claim 1, wherein, The collaborative power supply unit also integrates a battery health status monitoring circuit, which is used to assess the remaining power and lifespan in real time, and is linked with the data processing and control unit to trigger a low-power maintenance strategy when the power is insufficient.

9. The low power consumption wireless transmission transformer winding DC resistance tester of claim 1, wherein, The wireless communication unit supports a link self-recovery transmission mechanism, which can automatically attempt to re-establish the connection and resend data when a communication link interruption or data packet loss is detected.

10. The low power consumption wireless transmission transformer winding DC resistance tester of claim 1, wherein, The tester adopts a cavity shielding modular structure, the test acquisition unit, the data processing and control unit, the wireless communication unit and the cooperative power supply unit are respectively arranged in independent electromagnetic shielding cavities, and are electrically connected through board-to-board connectors.

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