Ultra-low current self-power-taking drop-type intelligent fuse

Abstract

The invention relates to the technical field of power distribution Internet of Things, discloses an ultra-small current self-power-taking drop-type intelligent fuse, and provides an integrated intelligent transformation scheme for solving the problems that a traditional 10kV drop-type fuse cannot be monitored on line and low-current power taking cannot be achieved. A power taking current transformer TA with a 1K107 amorphous alloy magnetic core is adopted, power taking is started under 0.2 A ultra-low current, and the low-load scene of a rural power grid is covered; an overcurrent protection circuit is designed, when the input current is larger than or equal to 1A, TA output short circuit is triggered, the temperature rise is limited to be smaller than or equal to 20 DEG C under the 100A working condition, and the long-term operation requirement is met; a three-axis angle sensor and a low-power-consumption RF module are integrated, and the two-remote function of fusion tube position, line current and fault warning is achieved. The distribution network end user demarcation point monitoring system fills the blank of distribution network end user demarcation point monitoring, is suitable for 10kV transformer areas and branch lines, and provides a low-cost and high-reliability intelligent upgrading scheme for the distribution internet of things.

Description

Technical Field

[0001] The present invention relates to the technical field of power distribution Internet of Things, and in particular to an ultra-small current self-powered drop-out intelligent fuse. Background Art

[0002] The power distribution Internet of Things (IoT), a new cyber-physical system that deeply integrates traditional industrial technologies with the Internet of Things (IoT), enables intelligent management of distribution networks through comprehensive device interconnection and data fusion. 12kV high-voltage drop-out fuses, a crucial protection device for distribution lines, are widely used at user demarcation points and branch lines. However, traditional fuses lack online monitoring capabilities, leaving the high-voltage side of substations in a long-term "monitoring blind spot," failing to meet the demands of lean distribution network management.

[0003] In recent years, smart fuse technology has gradually developed, for example, through the use of built-in current transformers (CTs) and wireless communication modules to achieve load monitoring and fault warning. However, existing technologies still have the following key issues:

[0004] 1. Insufficient power supply capability in low-current scenarios: The starting current of conventional current transformer (TA) power supply technology is generally ≥0.4A. However, approximately 30% of the high-voltage side normalized current in rural power grids is less than 0.4A. This results in equipment relying on backup batteries for power, which have a lifespan of only 1-3 years and cannot meet the requirements for long-term reliable operation.

[0005] 2. Difficulty controlling temperature rise under high current conditions: The fuse's rated current must reach 100A, but the current transformer's TA power module is prone to excessive temperature rise due to excess energy under high current, exceeding 20°C, threatening equipment safety.

[0006] 3. Poor compatibility between structural integration and operation and maintenance: Existing smart fuses mostly adopt a split design, which is complex to install and susceptible to environmental interference. The current transformer CT module is prone to parameter drift due to vibration and moisture, affecting measurement accuracy. Summary of the Invention

[0007] To solve the above problems, the present invention proposes an ultra-small current self-powered drop-out intelligent fuse. By optimizing the current transformer TA core material and structural design, innovating the overcurrent protection circuit and low-power control strategy, it can achieve 0.2A ultra-low current starting power supply, 100A large current temperature rise controllable, and integrate two remote control functions, filling the gap in distribution network terminal monitoring.

[0008] The technical solution adopted in the present invention is:

[0009] An ultra-low current self-collecting drop-out intelligent fuse, comprising: a standardized high-voltage drop-out fuse body installed at the end of a 10kV line, and an integrated intelligent data acquisition unit that is integrally sealed to the fuse tube of the fuse-carrying element of the standardized high-voltage drop-out fuse body through a clamp;

[0010] The integrated intelligent acquisition unit includes a power supply current transformer TA, a measuring current transformer CT, a measurement and control unit mainboard, and a power management module; the power supply current transformer TA is electrically connected to the power management module, the power management module is electrically connected to the measurement and control unit mainboard, and the measuring current transformer CT is electrically connected to the power management module; the power supply current transformer TA and the measuring current transformer CT are connected in series to the fuse carrier to directly sense the line current;

[0011] The power-taking current transformer TA starts to draw power at an input current of 0.2A, and limits the temperature rise to ≤20°C under 100A working conditions through the TA power-taking protection circuit of the power management module, and cooperates with the measurement and control unit mainboard to provide fuse-carrying element fuse tube position, line current and fault alarms.

[0012] Furthermore, the power-taking current transformer TA includes a current transformer body and a TA power-taking module electrically connected to the current transformer body; the power management module is electrically connected to the TA power-taking module, and a TA power-taking protection module is also provided which is electrically connected to the TA power-taking module.

[0013] Furthermore, the TA power supply module is provided with a TA power supply circuit, which includes a rectification and filtering circuit, a multi-stage voltage stabilization circuit, and a protection and current limiting circuit;

[0014] Rectification and filtering circuit: The output terminals CTDL1 and CTDL2 of the power-taking current transformer TA are connected to a bridge rectifier circuit consisting of diodes D1, D2, D3, and D4, which converts the AC signal into a DC signal. The rectified output is filtered by a filter circuit consisting of electrolytic capacitor EC1 and ceramic capacitor C1 to smooth out the ripple and form a stable DC voltage.

[0015] The multi-stage voltage stabilization circuit includes a primary voltage stabilization circuit and a secondary voltage stabilization circuit. The primary voltage stabilization circuit clamps the voltage to 10V through the voltage stabilization diode Z2, providing an intermediate stable voltage. The secondary voltage stabilization circuit steps down the voltage to 5.6V through the voltage stabilization diode Z3.

[0016] The protection and current limiting circuit is connected in parallel to the output end of the rectifier bridge through the bidirectional TVS tube Z1 to suppress transient voltage spikes. At the same time, it is connected in series in the circuit through the high-power resistor DR2 to limit abnormal current impact.

[0017] Furthermore, the TA power taking protection module is provided with a TA power taking overcurrent protection circuit, and the TA power taking overcurrent protection circuit is composed of an operational amplifier U1, resistors R1 and R2 to form a voltage comparator;

[0018] Among them, op amp U1 uses a CMOS voltage comparator; resistors R1 and R2 form a voltage divider network to set the threshold voltage V TH ; V TH =VTA +1V; when the current transformer TA outputs the rectified and stabilized voltage V TA1 When the threshold is exceeded, the comparator output BH_GB flips to a high level;

[0019] The protection mechanism of the TA power supply protection module is as follows: the high level of BH_GB triggers the MOS tubes V1 and V2 to turn on, directly grounding the output terminals CTDL1 and CTDL2 of the power supply current transformer TA, forcing the power supply current transformer TA into a short-circuit state and blocking energy transmission; after the short circuit, the output power of the power supply current transformer TA is limited to 27.5mVA, leaving only 0.5mVA for system operation, and the remaining energy is dissipated through the protection circuit; under high current, the output terminal of the power supply current transformer TA is periodically short-circuited and restored, forming a pulse voltage output, which controls the average power within the safe range of ≤0.5mVA.

[0020] Furthermore, the power management module is also connected to a supercapacitor charging and discharging module and a backup lithium battery management module;

[0021] The supercapacitor charging and discharging module starts charging at 0.5A; when the overcurrent protection circuit is triggered, the power-taking current transformer TA gives priority to charging the supercapacitor charging and discharging module, and the backup lithium battery management module serves as a backup power supply.

[0022] Furthermore, the design process of the power-taking current transformer TA includes the following steps:

[0023] Step 1: Define objectives and constraints: The power-supply current transformer (TA) must start at 0.2A, support long-term operation at 100A, have a temperature rise of ≤20°C, and meet structural requirements of an inner diameter ≥36mm and a weight ≤1.8kg.

[0024] Step 2: Select the core material: The maximum power draw of the intelligent fuse TA is determined by the k value, which depends on the core material. The core material is determined through material comparison and analysis tests.

[0025] Step 3 parameter calculation and verification:

[0026] Calculate the power based on the following formula to verify the feasibility of the design;

[0027]

[0028] Where, P max is the maximum power of the current transformer TA; k is the proportional coefficient; I is the current flowing through the current transformer TA; V is the volume of the magnetic core; D is the distance between the magnetic core and the through-core current line;

[0029] The calculation formula of the core volume V is as follows:

[0030] V=π·r22 ·h-π·r1 2 ·h;

[0031] Where r2 is the outer diameter of the core; r1 is the inner diameter of the core; h is the height of the core;

[0032] Step 4: Optimize the number of turns of the secondary winding: Determine the number of turns of the secondary winding through experiments to balance the output voltage and the trigger threshold of the protection circuit;

[0033] Step 5: Output characteristic test: Verify the no-load voltage of 5.5V and the load power to determine whether it meets the low power consumption requirements;

[0034] Based on the above design process, the power current transformer TA adopts 1K107 amorphous alloy core with inner diameter ≥36mm, outer diameter ≤81mm, secondary winding 60 turns, and core volume 146cm 3 The distance from the core to the conductor is 16 mm, and the proportional coefficient is 0.03 V / cm 2 , the output power is ≥0.5mVA at 0.2A input and ≤27.5mVA at 100A.

[0035] Furthermore, the measurement and control unit mainboard is provided with a measurement CT conditioning circuit electrically connected to the measurement current transformer CT, a main controller electrically connected to the measurement CT conditioning circuit and the power management module, an RF communication management module electrically connected to the main controller, and a three-axis angle sensor electrically connected to the main controller;

[0036] The main controller converts the weak current signal output by the current transformer (CT) into a processable voltage signal through the measurement CT conditioning circuit, including amplification, filtering and analog-to-digital conversion (ADC). The main controller indirectly calculates the line temperature by measuring the temperature rise characteristics of the current transformer (CT) or using a built-in temperature sensor to prevent overload heating.

[0037] The main controller detects the mechanical position change of the fuse-carrying element and the fuse tube through a three-axis angle sensor, and transmits a status signal to the main controller through an SPI / I2C interface to determine whether the fuse is actuated;

[0038] The main controller transmits data through the RF communication management module, sends real-time current and temperature data to the distribution automation master station through a wireless channel, and reports the drop status of the fuse tube and short circuit / overload alarm.

[0039] Furthermore, the main controller uses a low-power single-chip microcomputer STM32L431RCT6, which is activated once per second to clear the watchdog operation and read the angle data once, with a continuous working time of 10ms; starts the A / D conversion once every 20 seconds, with a continuous working time of 60ms; turns on the RF communication module once every 5 seconds, for 10ms; and turns on the RF communication module once every 20s to send a data message, for 50ms;

[0040] The power consumption of the microcontroller in sleep mode is 28nA, and the power consumption in running mode is 84μA / MHz. The system frequency of the microcontroller in non-A / D sampling mode is 32768Hz, the power consumption is 2.75uA, the power consumption of A / D sampling is 1000uA, and the average power consumption of the microcontroller is 3.1uA.

[0041] Furthermore, the working power supply of the three-axis angle sensor LIS2DH12 is controlled by the IO port VCC_CTL of the microcontroller; when the fuse opening and closing position signal is read regularly, the working power supply of LIS2DH12 is first turned on through the microcontroller VCC_CTL, the angle data is read through the SPI port, and the fuse opening and closing position is determined by the angle data; the angle data is read once per second, and the working time of the three-axis angle sensor LIS2DH12 is 10ms each time. The power consumption in the working mode is 11uA, and the average power consumption is 0.11uA.

[0042] Furthermore, the RF communication management module uses Zhou Ligong ZLG470SX-L, and its RF_CTRL pin is controlled by the IO port of the single-chip microcomputer, which is closed at a high level and opened at a low level to switch the power supply; the RF communication management module is only activated when sending and receiving, and is powered off at other times;

[0043] Under normal circumstances, the RF communication management module opens the receiving state once every 5 seconds, which lasts for 10ms, and sends a data message every 20s, which lasts for about 50ms. The message sending time is less than 5ms; the RF communication management module consumes 3mA in the receiving state and 16mA in the sending state, with an average power consumption of 17.5uA.

[0044] The beneficial effects of the present invention are:

[0045] 1. Ultra-small current self-powering capability:

[0046] This ultra-small current self-powered drop-out intelligent fuse adopts a TA design with a 1K107 amorphous alloy core, breaking through the limitation of traditional TA power-taking starting current ≥0.4A, covering 30% low-load scenarios in rural power grids, and reducing dependence on backup batteries; at the same time, it supports continuous operation of 0.2A to 100A, and controls the temperature rise to ≤20°C through the overcurrent protection circuit, solving the problem of thermal failure under high current conditions.

[0047] 2. High reliability structure design:

[0048] The measurement CT and power CT of this ultra-low current, self-powered dropout smart fuse are sealed in an intelligent data acquisition unit (IDU). This unit, with an IP67 rating and waterproof and shockproof, prevents parameter drift caused by environmental interference, improving long-term operational stability by over 50%. The integrated IDU weighs ≤ 800g and is compatible with standardized fuse bodies, maintaining the same installation and maintenance procedures and reducing on-site operational complexity.

[0049] 3. Low power consumption and intelligent functions:

[0050] This ultra-low current, self-powered, drop-out smart fuse collects line current and temperature in real time, enabling telemetry. A three-axis angle sensor detects the drop status of the fuse tube and, based on current fluctuations, generates short-circuit / overload alarms, enabling remote signaling. This ultra-low current, self-powered, drop-out smart fuse utilizes an RF communication management module, supporting both scheduled and event-triggered modes. With an average power consumption of only 17.5μA, it's compatible with TA power supply capabilities.

[0051] 4. Economic efficiency and promotion value

[0052] This ultra-small current self-powered drop-out intelligent fuse integrates an intelligent unit based on a standardized fuse, eliminating the need to replace the original equipment. The cost per unit is significantly lower than that of a split-type solution. It provides an intelligent upgrade solution for 10kV user branches and demarcation points, supporting the improvement of end-of-line monitoring coverage in the distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction to the drawings required for use in the embodiments will be given below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0054] Figure 1 This is a schematic diagram of the overall structure of the ultra-small current self-powered drop-out intelligent fuse of the present invention;

[0055] Figure 2 This is a structural diagram of the integrated intelligent acquisition unit of the present invention;

[0056] Figure 3 This is a schematic diagram of power supply for the intelligent fuse TA of the present invention;

[0057] Figure 4 This is a circuit diagram of the TA power supply circuit of the present invention;

[0058] Figure 5 This is a circuit diagram of the TA power overcurrent protection circuit of the present invention;

[0059] Figure 6 This is a schematic diagram of module connections on the mainboard of the measurement and control unit of the present invention;

[0060] Figure 7 This is a connection diagram of the three-axis angle sensor of the present invention;

[0061] Figure 8 This is a connection diagram of the RF communication management module of the present invention;

[0062] Figure 9 A circuit diagram of the RF communication management module of the present invention;

[0063] In the figure: 1. Standardized high-voltage drop-out fuse body, 2. Melt-carrying fuse tube, 3. Integrated intelligent data acquisition unit. DETAILED DESCRIPTION

[0064] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0065] In order to solve the problem that traditional 10kV drop-out fuse cannot be monitored online and has low current power supply, this embodiment provides an ultra-low current self-powered drop-out intelligent fuse; Figure 1 As shown, the ultra-small current self-collecting power drop-out type intelligent fuse includes a standardized high-voltage drop-out type fuse body 1 installed at the end of the 10kV line, and an integrated intelligent acquisition unit 3 that is integrally sealed on the fuse-carrying element fusion tube 2 of the standardized high-voltage drop-out type fuse body 1 through a clamp.

[0066] like Figure 2 As shown, the integrated intelligent data acquisition unit 3 includes a power supply current transformer (TA), a measuring current transformer (CT), a measurement and control unit mainboard, and a power management module. The power supply current transformer (TA) is electrically connected to the power management module, which is in turn electrically connected to the measurement and control unit mainboard. The measuring current transformer (CT) is also electrically connected to the power management module. The power supply current transformer (TA) and the measuring current transformer (CT) are connected in series with the fuse carrier to directly sense the line current. Without changing the installation and operation of the high-voltage drop fuse, the integrated intelligent data acquisition unit 3 can perform two remote functions, including collecting the position signal of the drop fuse tube, current collection, and line fault alarms, thus realizing intelligent high-voltage drop fuses.

[0067] Furthermore, this embodiment provides the following detailed description of the power supply part of the integrated intelligent acquisition unit 3:

[0068] like Figure 2 and Figure 3 As shown, the power-taking current transformer TA includes a current transformer body and a TA power-taking module electrically connected to the current transformer body; the power management module is electrically connected to the TA power-taking module, and a TA power-taking protection module is also provided which is electrically connected to the TA power-taking module.

[0069] Power supply current transformer TA:

[0070] The design process of the power supply current transformer TA includes the following steps:

[0071] Step 1: Define objectives and constraints: The power-supply current transformer (TA) must start at 0.2A, support long-term operation at 100A, have a temperature rise of ≤20°C, and meet structural requirements of an inner diameter ≥36mm and a weight ≤1.8kg.

[0072] Step 2: Select the core material: The maximum power draw of the intelligent fuse TA is determined by the k value, which depends on the core material. The core material is determined through material comparison and analysis tests.

[0073] Step 3 parameter calculation and verification:

[0074] Calculate the power based on the following formula to verify the feasibility of the design;

[0075]

[0076] Where, P max is the maximum power of the current transformer TA; k is the proportional coefficient; I is the current flowing through the current transformer TA; V is the volume of the magnetic core; D is the distance between the magnetic core and the through-core current line;

[0077] The calculation formula of the core volume V is as follows:

[0078] V=π·r2 2 ·h-π·r1 2 ·h;

[0079] Where r2 is the outer diameter of the core; r1 is the inner diameter of the core; h is the height of the core;

[0080] Step 4: Optimize the number of turns of the secondary winding: Determine the number of turns of the secondary winding through experiments to balance the output voltage and the trigger threshold of the protection circuit;

[0081] Step 5: Output characteristic test: Verify the no-load voltage of 5.5V and the load power to determine whether the low power consumption requirement is met.

[0082] According to the design process of the aforementioned power-drawing current transformer (TA), and based on the State Grid Corporation of China's technical specifications, the outer diameter of the fuse tube is generally around 30 mm, plus the collector housing thickness is 3 mm. Therefore, the minimum inner diameter of the intelligent fuse power-drawing TA must not be less than 36 mm. The fuse carrier is manually installed using an insulating rod when replacing the fuse, and its weight should not be too large. In principle, the weight of an intelligent fuse should not exceed twice that of a conventional fuse. The fuse carrier of a conventional fuse weighs approximately 0.9 kg. The weight of the intelligent fuse, which includes the measuring current transformer, power-drawing current transformer, and collection unit, should be controlled to approximately 1.8 kg. This determines the size of the intelligent fuse power-drawing TA. The power-drawing TA selected in this embodiment has an inner diameter of 36 mm, an outer diameter of 81 mm, and a height of 42 mm; the magnetic core has an inner diameter of 32 mm, an outer diameter of 77 mm, and a height of 38 mm.

[0083] Based on the calculation formula of the core volume V, we get:

[0084] V=π·r2 2 ·h-π·r1 2 h=146316mm 3 =146cm 3 ;

[0085] Design: core outer diameter r2 = 38.5mm, core inner diameter r1 = 16mm, core height h = 38mm, the shortest distance D between the core and the through-core current line min =16mm=1.6cm.

[0086] Under the condition that the size of the power supply TA is clear, the maximum power supply capacity of the intelligent fuse TA is determined by the k value, which is determined by the core material. After repeated tests and comparative analysis of various core materials such as silicon steel sheets, amorphous alloys, and Permalloy, 1K107 amorphous alloy was finally selected as the core material of the power supply TA. 1K107 amorphous alloy is an iron-based soft magnetic alloy material with an ultra-fine crystal structure and a grain size of 10nm. It has excellent soft magnetic properties such as high saturation magnetic induction, high magnetic permeability, and low loss.

[0087] The designed power supply current transformer TA has a saturation current of about 10A;

[0088] In the saturation current range, the proportional coefficient k = 0.028, and the power calculation is:

[0089]

[0090] The maximum energy consumption P when the minimum starting current is 0.2A is tested max =0.5mVA; the output voltage of the rectification bridge is V = 5.5V, and the output current is 100uA.

[0091] In the non-saturated current state, the proportional coefficient k = 0.03V / cm2 , and calculate the power to get:

[0092] P max =27.5mVA.

[0093] Select an appropriate number of secondary turns for the current transformer (TA). The no-load output voltage of the TA is proportional to the number of turns. Given a given load, a smaller number of turns results in a lower output voltage and a higher startup current. A larger number of turns increases the output voltage, but this means the TA's output protection activates earlier, while the startup current remains constant, while maintaining the same power-taking capacity. Therefore, it's important to select an appropriate number of secondary turns. Repeated testing has shown that 60 turns provide the highest power-taking capacity.

[0094] In summary, based on the above design process, the current transformer TA in this embodiment adopts a 1K107 amorphous alloy core with an inner diameter of ≥36mm and an outer diameter of ≤81mm, a secondary winding of 60 turns, and a core volume of 146cm 3 The distance from the core to the conductor is 16 mm, and the proportional coefficient is 0.03 V / cm 2 , the output power is ≥0.5mVA at 0.2A input and ≤27.5mVA at 100A.

[0095] Further, such as Figure 2 and Figure 3 As shown, the TA power supply module is provided with a TA power supply circuit, which includes a rectification and filtering circuit, a multi-stage voltage stabilization circuit, and a protection and current limiting circuit.

[0096] The circuit diagram of TA power supply circuit is as follows Figure 4 As shown in the figure, the rectifier and filter circuit: the output terminals CTDL1 and CTDL2 of the power-taking current transformer TA are connected to a bridge rectifier circuit composed of diodes D1, D2, D3, and D4 to convert the AC signal into a DC signal; the rectified output is smoothed by a filter circuit composed of an electrolytic capacitor EC1 and a ceramic capacitor C1 to form a stable DC voltage.

[0097] The multi-stage voltage stabilization circuit includes a primary voltage stabilization circuit and a secondary voltage stabilization circuit; the primary voltage stabilization circuit clamps the voltage to 10V through the voltage stabilization diode Z2 to provide an intermediate stable voltage; the secondary voltage stabilization circuit reduces the voltage to 5.6V through the voltage stabilization diode Z3.

[0098] The protection and current limiting circuit is connected in parallel to the output end of the rectifier bridge through the bidirectional TVS tube Z1 to suppress transient voltage spikes. At the same time, it is connected in series in the circuit through the high-power resistor DR2 to limit abnormal current impact.

[0099] The TA power taking circuit converts the AC output of the power taking current transformer into a DC voltage output.

[0100] TA power protection module:

[0101] Furthermore, the difficulty with TA powering isn't its low-current draw capability; the key lies in the temperature rise and maximum current operating range when operating at high current. State Grid Corporation of China's technical specifications require a 100A rated current for 10kV drop-out fuses, meaning they must operate reliably and long-term at 100A. The technical specifications mandate an ambient temperature range of -40°C to +70°C for outdoor distribution automation terminals. At a maximum ambient temperature of 50°C, to ensure reliable operation of distribution automation terminals, the temperature rise of smart fuses must not exceed 20°C. TA powering differs fundamentally from voltage powering. Voltage powering depends on the load. While voltage powering modules draw energy from the power supply based on the overall load, TA powering modules draw energy independently of the load. Higher currents result in greater output power. Energy exceeding the load is converted to heat on the device side, generating a temperature rise. Higher currents increase the temperature rise, directly limiting the maximum current range of TA powering.

[0102] According to the above analysis of TA maximum energy consumption, TA provides 27.5mVA power at high current, and the actual average power consumption of the intelligent fuse controller is 0.5mVA, which means that 27mVA of power is generated in the TA power circuit for heat generation. Figure 2 and Figure 3 As shown, in this embodiment, a TA power taking overcurrent protection circuit is provided in the TA power taking protection module. When the current exceeds a certain value, the TA power taking circuit voltage output exceeds a certain value and automatically controls the TA power taking output terminal to be short-circuited. After the TA output terminal is short-circuited, the TA power taking circuit voltage output decreases and enters the TA power taking state. Therefore, when the input current is greater than a certain value, the TA power taking output is a pulse voltage, which ensures that the output power is maintained within a certain range under large current conditions and effectively reduces the temperature rise; at the same time, the maximum operating current range is increased.

[0103] Specifically, such as Figure 5 As shown, the TA power overcurrent protection circuit consists of an operational amplifier U1, resistors R1 and R2 forming a voltage comparator;

[0104] Among them, op amp U1 uses a CMOS voltage comparator; resistors R1 and R2 form a voltage divider network to set the threshold voltage V TH ; V TH =V TA +1V; when the voltage output by the current transformer TA exceeds the threshold after rectification and stabilization, the comparator output terminal BH_GB flips to a high level;

[0105] The protection mechanism of the TA power supply protection module is as follows: the high level of BH_GB triggers the MOS tubes V1 and V2 to turn on, directly grounding the output terminals CTDL1 and CTDL2 of the power supply current transformer TA, forcing the power supply current transformer TA into a short-circuit state and blocking energy transmission; after the short circuit, the output power of the power supply current transformer TA is limited to 27.5mVA, leaving only 0.5mVA for system operation, and the remaining energy is dissipated through the protection circuit; under high current, the output terminal of the power supply current transformer TA is periodically short-circuited and restored, forming a pulse voltage output, which controls the average power within the safe range of ≤0.5mVA.

[0106] The difficulty of TA power supply is not the ability to draw power at low currents, but the temperature rise and maximum current operating range when drawing high currents. The TA power supply overcurrent protection circuit ensures that the output power is maintained within a certain range under high current conditions, achieving the required temperature rise. This embodiment starts drawing power at an input current of 0.2A and activates overcurrent protection at around 1A. Testing has shown that while ensuring 0.2A power supply, the maximum input current can reach 100A and the maximum temperature rise does not exceed 20°C, further ensuring that the design goals are met.

[0107] Power management module, supercapacitor charging and discharging module and backup lithium battery management module:

[0108] In addition, if Figure 2 and Figure 3 As shown, the power management module is also connected to the supercapacitor charging and discharging module and the backup lithium battery management module. The supercapacitor charging and discharging module starts charging at 0.5A. When the overcurrent protection circuit is triggered, the power transformer (TA) prioritizes charging the supercapacitor charging and discharging module, with the backup lithium battery management module serving as a backup power source. The power management module primarily draws power from the TA, supplemented by the supercapacitor and lithium battery, reducing the frequency of battery replacements and thus extending the life of the device.

[0109] Furthermore, this embodiment provides a detailed description of the functional parts of the integrated intelligent acquisition unit 3 as follows:

[0110] Under certain core size, the power of TA is in the mW level or even lower, so low power consumption design is a necessary condition for TA power automation devices. Figure 6 、 Figure 7 and Figure 8 As shown, the measurement and control unit mainboard is provided with a measurement CT conditioning circuit electrically connected to the measurement current transformer CT, a main controller electrically connected to the measurement CT conditioning circuit and the power management module, an RF communication management module electrically connected to the main controller, and a three-axis angle sensor electrically connected to the main controller.

[0111] Main controller:

[0112] The main controller uses a low-power microcontroller and low-power peripheral circuits to effectively reduce the overall power consumption of the device. Tests show that the average power consumption of the entire device is 3.3V / 50uA. The low-power STM32L431RCT6 microcontroller serves as the main processor, and all peripheral circuits have controllable operating power supplies, minimizing overall power consumption.

[0113] STM32L431RCT6 is a 32-bit low-power microcontroller produced by STM. Its parameters are as follows:

[0114] 1.71V to 3.6V wide voltage operating power supply;

[0115] -40℃ to 85℃ wide operating temperature range;

[0116] 8nA shutdown mode;

[0117] 28nA standby mode;

[0118] 280nA standby mode with RTC;

[0119] 84μA / MHz operating mode;

[0120] Fast wake-up from stop mode: 4μs;

[0121] Up to 16 channels of 12-bit A / D, 5Msps, 200μA / Msps;

[0122] The microcontroller is activated once per second to clear the watchdog timer, which lasts less than 1ms. The A / D conversion is started every 20 seconds, with continuous sampling for 3 cycles of 60ms.

[0123] Three-axis angle sensor:

[0124] The three-axis angle sensor LIS2DH12 is used to collect the open and close positions of the drop-out fuse. The parameters of the three-axis angle sensor LIS2DH12 are as follows:

[0125] Wide supply voltage: 1.71V to 3.6V;

[0126] Ultra-low power consumption as low as 2μA, and 11uA in 50Hz ODR working mode;

[0127] 2g / ±4g / 8g / 16g select full scale;

[0128] I2C / SPI digital output interface;

[0129] Working range: -40°~+85°;

[0130] The operating power is controlled by the microcontroller's VCC_CTL IO port. To periodically read the fuse open / close position signal, the LIS2DH12 is powered on via the microcontroller's VCC_CTL port. Angle data is read via the SPI port, and the fuse open / close position is determined based on this data. The device reads the angle data once per second, with the LIS2DH12 three-axis angle sensor operating for 10 milliseconds. Power consumption in operating mode is 11uA, with an average power consumption of 0.11uA.

[0131] RF communication management module:

[0132] The RF communication management module uses Zhou Ligong ZLG470SX-L, based on Semtech's SX1212, using traditional FSK modulation technology. The parameters are as follows:

[0133] Power supply voltage Vcc: 2.1V~3.6V, nominal 3.3V;

[0134] Equipped with SPI interface;

[0135] Receiving current IRX: 3.0mA;

[0136] Transmit current ITX_12: 32.6mA, transmit power 12dBm;

[0137] Transmit current ITX_1: 16mA, transmit power 1dBm;

[0138] Working range: -40°~+80°;

[0139] The circuit diagram of the RF communication module is as follows Figure 9 As shown, U3-ZM470SL is the RF transceiver control chip with a center frequency of 470 MHz. It connects to the microcontroller via the SPI interface and implements data transmission and reception under the microcontroller's control. The U2_ANT pin is the wireless signal interface for connecting an external antenna. RF_CTRL is the microcontroller I / O port that controls the wireless communication module's operating power. When RF_CTRL is high, the module's power is turned off. When RF_CTRL is low, the module's power is turned on, and the module is in operation. This ensures that power consumption is only generated during transmission and reception, effectively reducing the average power consumption of the entire device.

[0140] The working power of the RF communication module is controlled by the MCU IO port RF_CTL and has two working modes:

[0141] Working mode 3 is the timed open receiving mode. After receiving the request message from the main control unit or debugging tool software, it is in a continuous receiving state and receives commands such as data query, parameter setting, and software upgrade from the main control unit;

[0142] Working mode 2 is the timed sending mode, which opens the receiving mode at regular intervals and sends data messages; working mode 3 is the timed triggering mode, which opens the receiving mode in time and sends data messages when the fuse opening and closing positions change or a line fault is detected.

[0143] Under normal circumstances, the device opens the receiving state every 5 seconds for 10ms and sends a data message every 20s for about 50ms, with the message transmission time being less than 5ms. The ZLG470SX-L consumes 3mA in receiving state and 16mA in transmitting state. At 1dB transmit power, the average power consumption is 17.5uA.

[0144] Measuring CT conditioning circuit:

[0145] Since the power consumption of the single-chip microcomputer in the A / D working mode reaches the mA level, in order to meet the normal operation of the device when drawing power with ultra-small current TA, A / D sampling cannot be performed continuously. The intelligent fuse is required to accurately monitor the phase-to-phase short circuit fault. The shortest duration of the two-phase short circuit fault is only about 30ms. The distribution terminal detects the fault time of 20-30ms, the spring-operated mechanism circuit breaker cuts off the fault time of about 30ms, and the fast permanent magnet cuts off the fault time of 5-10ms. To solve the above problems, this embodiment designs a measurement CT conditioning circuit between the main controller and the measurement current transformer CT. When the line current suddenly changes, an interrupt is automatically generated to activate the single-chip microcomputer. After the single-chip microcomputer is activated, the current value is continuously sampled, thereby accurately judging the phase-to-phase short circuit fault. The measurement CT conditioning circuit consists of the operational amplifier SGM8041 and peripheral circuits;

[0146] The parameters of the op amp SGM8041 are as follows:

[0147] Power supply voltage Vcc: 1.5V~5.5V, nominal 3.3V;

[0148] Power consumption is 710nA, or 0.71uA;

[0149] Working range: -40°~+85°;

[0150] In the non-fault state, the power consumption of the CT conditioning circuit is measured to be 0.71uA, which is negligible. The probability of failure is extremely low and has no impact on the average power consumption of the entire machine.

[0151] In summary, the main controller converts the weak current signal output by the current transformer (CT) into a processable voltage signal through the measurement CT conditioning circuit, including amplification, filtering and analog-to-digital conversion (ADC); the main controller indirectly infers the line temperature by measuring the temperature rise characteristics of the current transformer (CT) or the built-in temperature sensor to prevent overload heating; the main controller detects the mechanical position change of the fuse-carrying element molten tube 2 through the three-axis angle sensor, and transmits the status signal to the main controller through the SPI / I2C interface to determine whether the fuse is activated; the main controller transmits data through the RF communication management module, sends real-time current and temperature data to the distribution automation master station through the wireless channel, and reports the drop status of the fuse-carrying element molten tube 2 and the short circuit / overload alarm.

[0152] The main controller's single-chip microcomputer is activated once per second to clear the watchdog timer and read the angle data at the same time, with a continuous working time of 10ms; the A / D conversion is started once every 20 seconds, with a continuous working time of 60ms; the RF communication module is turned on once every 5 seconds, with a continuous working time of 10ms; and the RF communication module is turned on once every 20s to send a data message, with a continuous working time of about 50ms.

[0153] The microcontroller consumes a negligible 28nA in sleep mode and 84μA / MHz in run mode. In non-A / D sampling mode, the system frequency is 32768Hz, and the power consumption is 2.75uA; the power consumption during A / D sampling is 1000uA. The average power consumption of the microcontroller is 3.1uA.

[0154] Average power consumption of the entire device = 3.1uA MCU power consumption + 0.11uA timing three-axis angle sensor LIS2DH12 power consumption + 17.5uA timing RF short-range wireless power consumption = 20.71uA.

[0155] The above measures have effectively reduced the power consumption of the whole machine. After testing, the average power consumption of the whole machine is 3.3V / 50uA.

[0156] The integrated intelligent data acquisition unit enables ultra-low current TA power supply and low current startup supercapacitor charging, greatly expanding the application scenarios of smart fuses. The battery truly becomes a backup power source, effectively extending the life of the device. After actual testing, the comparative data is as follows:

[0157]

[0158]

[0159] This ultra-small current, self-powered, drop-out intelligent fuse integrates an intelligent measurement and control unit based on a standardized drop-out high-voltage fuse. This simplifies operation and maintenance by not changing the installation and operation methods. The measuring CT and power-drawing CT are sealed in the intelligent acquisition unit box, which is waterproof, moisture-proof, and vibration-proof, ensuring the stability of the parameters of the measuring CT and power-drawing CT under long-term operating conditions. It integrates a variety of technical means, including a low-power single-chip microcomputer, a three-axis angle sensor to collect the position of the fuse carrier, and a power-controllable RF short-range wireless communication module. Under the long-term operating conditions of an ultra-small current of 0.2A and a maximum of 100A, the TA can reliably self-power, realize the two remote functions of fuse position signal collection, current collection, and line fault alarm, and realize the intelligence of the high-voltage drop-out fuse. It is suitable for most substation application scenarios.

[0160] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. An ultra-small current self-powered drop-out intelligent fuse, characterized in that: include: The standardized high-voltage drop-out fuse body is installed at the end of the 10kV line, and the integrated intelligent data acquisition unit is sealed on the fuse-carrying element of the standardized high-voltage drop-out fuse body through a clamp; The integrated intelligent acquisition unit includes a power supply current transformer TA, a measuring current transformer CT, a measurement and control unit mainboard, and a power management module; The power-taking current transformer TA is electrically connected to the power management module, the power management module is electrically connected to the measurement and control unit mainboard, and the measuring current transformer CT is electrically connected to the power management module; the power-taking current transformer TA and the measuring current transformer CT are connected in series to the fuse-carrying fuse to directly sense the line current; The power-taking current transformer TA starts to draw power at an input current of 0.2A, and limits the temperature rise to ≤20°C under 100A working conditions through the TA power-taking protection circuit of the power management module, and cooperates with the measurement and control unit mainboard to provide fuse-carrying element fuse tube position, line current and fault alarms.

2. The ultra-low current self-powered drop-out intelligent fuse according to claim 1 is characterized in that: The power-taking current transformer TA includes a current transformer body and a TA power-taking module electrically connected to the current transformer body; the power management module is electrically connected to the TA power-taking module, and a TA power-taking protection module is also provided which is electrically connected to the TA power-taking module.

3. The ultra-low current self-powered drop-out intelligent fuse according to claim 2 is characterized in that: The TA power supply module is provided with a TA power supply circuit, which includes a rectification and filtering circuit, a multi-stage voltage stabilization circuit, and a protection and current limiting circuit; Rectification and filtering circuit: The output terminals CTDL1 and CTDL2 of the power-taking current transformer TA are connected to a bridge rectifier circuit consisting of diodes D1, D2, D3, and D4, which converts the AC signal into a DC signal. The rectified output is filtered by a filter circuit consisting of electrolytic capacitor EC1 and ceramic capacitor C1 to smooth out the ripple and form a stable DC voltage. The multi-stage voltage stabilization circuit includes a primary voltage stabilization circuit and a secondary voltage stabilization circuit. The primary voltage stabilization circuit clamps the voltage to 10V through the voltage stabilization diode Z2, providing an intermediate stable voltage. The secondary voltage stabilization circuit steps down the voltage to 5.6V through the voltage stabilization diode Z3. The protection and current limiting circuit is connected in parallel to the output end of the rectifier bridge through the bidirectional TVS tube Z1 to suppress transient voltage spikes. At the same time, it is connected in series in the circuit through the high-power resistor DR2 to limit abnormal current impact.

4. The ultra-low current self-powered drop-out intelligent fuse according to claim 2 is characterized in that: The TA power protection module is provided with a TA power overcurrent protection circuit, which is composed of an operational amplifier U1, resistors R1 and R2 to form a voltage comparator; Among them, op amp U1 uses a CMOS voltage comparator; resistors R1 and R2 form a voltage divider network to set the threshold voltage V TH ; V TH =V TA +1V; when the current transformer TA outputs the rectified and stabilized voltage V TA1 When the threshold is exceeded, the comparator output BH_GB flips to a high level; The protection mechanism of the TA power supply protection module is as follows: the high level of BH_GB triggers the MOS tubes V1 and V2 to turn on, directly grounding the output terminals CTDL1 and CTDL2 of the power supply current transformer TA, forcing the power supply current transformer TA into a short-circuit state and blocking energy transmission; after the short circuit, the output power of the power supply current transformer TA is limited to 27.5mVA, leaving only 0.5mVA for system operation, and the remaining energy is dissipated through the protection circuit; under high current, the output terminal of the power supply current transformer TA is periodically short-circuited and restored, forming a pulse voltage output, which controls the average power within the safe range of ≤0.5mVA.

5. The ultra-low current self-powered drop-out intelligent fuse according to claim 4 is characterized in that: The power management module is also connected to a supercapacitor charging and discharging module and a backup lithium battery management module; The supercapacitor charging and discharging module starts charging at 0.5A; when the overcurrent protection circuit is triggered, the power-taking current transformer TA gives priority to charging the supercapacitor charging and discharging module, and the backup lithium battery management module serves as a backup power supply.

6. The ultra-low current self-powered drop-out intelligent fuse according to claim 1 is characterized in that: The design process of the power-taking current transformer TA includes the following steps: Step 1: Define objectives and constraints: The power-supply current transformer (TA) must start at 0.2A, support long-term operation at 100A, have a temperature rise of ≤20°C, and meet structural requirements of an inner diameter ≥36mm and a weight ≤1.8kg. Step 2: Select the core material: The maximum power draw of the intelligent fuse TA is determined by the k value, which depends on the core material. The core material is determined through material comparison and analysis tests. Step 3 parameter calculation and verification: Calculate the power based on the following formula to verify the feasibility of the design; Where, P max is the maximum power of the current transformer TA; k is the proportional coefficient; I is the current flowing through the current transformer TA; V is the volume of the magnetic core; D is the distance between the magnetic core and the through-core current line; The calculation formula of the core volume V is as follows: V=π·r2 2 ·h-π·r1 2 ·h; Where r2 is the outer diameter of the core; r1 is the inner diameter of the core; h is the height of the core; Step 4: Optimize the number of turns of the secondary winding: Determine the number of turns of the secondary winding through experiments to balance the output voltage and the trigger threshold of the protection circuit; Step 5: Output characteristic test: Verify the no-load voltage of 5.5V and the load power to determine whether it meets the low power consumption requirements; Based on the above design process, the power current transformer TA adopts 1K107 amorphous alloy core with inner diameter ≥36mm, outer diameter ≤81mm, secondary winding 60 turns, and core volume 146cm 3 The distance from the core to the conductor is 16 mm, and the proportional coefficient is 0.03 V / cm 2 , the output power is ≥0.5mVA at 0.2A input and ≤27.5mVA at 100A.

7. The ultra-low current self-powered drop-out intelligent fuse according to claim 1, characterized in that: The measurement and control unit mainboard is provided with a measurement CT conditioning circuit electrically connected to the measurement current transformer CT, a main controller electrically connected to the measurement CT conditioning circuit and the power management module, an RF communication management module electrically connected to the main controller, and a three-axis angle sensor electrically connected to the main controller; The main controller converts the weak current signal output by the current transformer (CT) into a processable voltage signal through the measurement CT conditioning circuit, including amplification, filtering and analog-to-digital conversion (ADC). The main controller indirectly calculates the line temperature by measuring the temperature rise characteristics of the current transformer (CT) or using a built-in temperature sensor to prevent overload heating. The main controller detects the mechanical position change of the fuse-carrying element and the fuse tube through a three-axis angle sensor, and transmits a status signal to the main controller through an SPI / I2C interface to determine whether the fuse is actuated; The main controller transmits data through the RF communication management module, sends real-time current and temperature data to the distribution automation master station through a wireless channel, and reports the drop status of the fuse tube and short circuit / overload alarm.

8. The ultra-low current self-powered drop-out intelligent fuse according to claim 7, characterized in that: The main controller uses a low-power single-chip microcomputer STM32L431RCT6, which is activated once per second to clear the watchdog operation and read the angle data at the same time, with a continuous working time of 10ms; the A / D conversion is started every 20 seconds, with a continuous working time of 60ms; the RF communication module is turned on once every 5 seconds, with a continuous working time of 10ms; and the RF communication module is turned on once every 20s to send a data message, with a continuous working time of 50ms. The power consumption of the microcontroller in sleep mode is 28nA, and the power consumption in running mode is 84μA / MHz. The system frequency of the microcontroller in non-A / D sampling mode is 32768Hz, the power consumption is 2.75uA, the power consumption of A / D sampling is 1000uA, and the average power consumption of the microcontroller is 3.1uA.

9. The ultra-low current self-powered drop-out intelligent fuse according to claim 7, characterized in that: The working power supply of the three-axis angle sensor LIS2DH12 is controlled by the IO port VCC_CTL of the microcontroller; when regularly reading the fuse opening and closing position signal, the working power supply of LIS2DH12 is first turned on through the microcontroller VCC_CTL, the angle data is read through the SPI port, and the fuse opening and closing position is determined based on the angle data; the angle data is read once per second, and the working time of the three-axis angle sensor LIS2DH12 is 10ms each time. The power consumption in the working mode is 11uA, and the average power consumption is 0.11uA.

10. The ultra-low current self-powered drop-out intelligent fuse according to claim 7, characterized in that: The RF communication management module uses Zhou Ligong ZLG470SX-L, and its RF_CTRL pin is controlled by the IO port of the single-chip microcomputer. The high level is closed and the low level is opened to switch the power supply. The RF communication management module is only activated when sending and receiving, and is powered off at other times. Under normal circumstances, the RF communication management module opens the receiving state once every 5 seconds, which lasts for 10ms, and sends a data message every 20s, which lasts for about 50ms. The message sending time is less than 5ms; the RF communication management module consumes 3mA in the receiving state and 16mA in the sending state, with an average power consumption of 17.5uA.

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