Wireless-based three-phase synchronous grounding fault indication sensor in transformer substation

Abstract

The invention relates to the technical field of power system monitoring, and particularly discloses a wireless-based three-phase synchronous grounding fault indication sensor in a transformer substation, which comprises a master control sensing unit and at least two driven sensing units. The master control sensing unit and the driven sensing unit are mutually independent in physical structure, form a cooperative work system in a wireless communication mode, and are respectively used for being installed on a three-phase conductor of a transformer substation busbar. The master control sensing unit and the driven sensing unit are respectively provided with a current acquisition function module, a central processing function module, a wireless communication transceiving function module, a self-energy-taking function module, a power management function module and an opening and closing type installation mechanism function module. The technical effects of high-precision three-phase synchronous acquisition, long-term maintenance-free self power supply, reliable wireless data transmission and non-intrusive rapid deployment are achieved. Through a closed-loop time calibration mechanism based on local wireless broadcasting, time synchronization errors of all sensing units are ensured to be stably controlled within 1 microsecond.

Description

Technical Field

[0001] This invention relates to a fault indication sensor, specifically a wireless three-phase synchronous grounding fault indication sensor for use in substations, belonging to the field of power system monitoring technology. Background Technology

[0002] In modern power systems, substations serve as the core hubs for power transmission and distribution, and their operational reliability directly impacts the safety and stability of the power grid. Ground faults are among the most common electrical fault types in substations, and their rapid and accurate detection and location are crucial for ensuring equipment safety and minimizing power outage time. However, in practical applications, traditional ground fault detection methods often rely on centralized protection devices or manual inspections. These methods suffer from slow response times, complex deployments, and high maintenance costs, making it difficult to meet the demands of modern smart grids for efficient and precise monitoring.

[0003] While some sensor-based ground fault detection solutions can improve detection efficiency to some extent, they still face several technical bottlenecks. First, achieving high-precision synchronous acquisition of three-phase current signals in the complex electromagnetic environment of substations is a key challenge. Traditional sensors typically use wired connections, which are not only complex to install but also susceptible to electromagnetic interference, making it difficult to guarantee the accuracy and consistency of data acquisition. Second, the power supply for sensors is also a major problem. Existing power supply methods mostly rely on external power sources or batteries. The former requires additional wiring, increasing installation difficulty and cost, while the latter requires frequent replacement due to limited battery life, making long-term maintenance-free operation difficult. Furthermore, the application of wireless communication technology in substations is also limited. Due to severe electromagnetic interference, the reliability and stability of wireless signals are difficult to guarantee, especially at high frequencies, where insufficient communication link budget is particularly prominent. Finally, the installation of existing sensors is usually cumbersome, requiring tools for fixing, which not only reduces deployment efficiency but may also affect measurement accuracy or damage the busbar insulation layer due to improper installation.

[0004] To address the aforementioned issues, there is an urgent need for a novel ground fault indication sensor that overcomes the shortcomings of existing technologies. This sensor should possess high-precision three-phase synchronous acquisition capabilities, enabling stable data acquisition in complex electromagnetic environments. Simultaneously, it must solve the problem of long-term maintenance-free self-powered operation to adapt to diverse operating conditions within substations. Furthermore, the sensor should support reliable wireless data transmission and be rapidly deployed non-intrusively, significantly improving the system's practicality and operability. Based on this technical requirement, this invention proposes a wireless-based three-phase synchronous ground fault indication sensor for substations. Through a master-slave collaborative, hierarchical synchronization sensing architecture design, combined with an event-driven multi-level power management strategy and an integrated self-powered system, it systematically resolves the aforementioned technical contradictions, providing an innovative solution for the efficient detection of substation ground faults. Summary of the Invention

[0005] This invention addresses the technical challenges of achieving high-precision three-phase synchronous data acquisition, long-term maintenance-free self-powered operation, reliable wireless data transmission, and non-intrusive rapid deployment in the complex electromagnetic environment of substations. To resolve these issues, a three-phase synchronous grounding fault indication sensor for substations based on a master-slave collaborative, hierarchical synchronous sensing architecture is proposed. This sensor solves the aforementioned technical problems by combining an event-driven multi-level power consumption status management strategy with an integrated self-powering system.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A wireless-based three-phase synchronous grounding fault indication sensor for substations includes a master control sensing unit and at least two slave sensing units. The master control sensing unit and the slave sensing units are physically independent but form a cooperative working system via wireless communication, and are respectively installed on the three-phase conductors of the substation busbar. Both the master control sensing unit and the slave sensing units have functional modules for current acquisition, central processing, wireless communication transceiver, self-powering and power management, and a hinged installation mechanism.

[0008] The main control sensing unit includes a first current acquisition module, a first central processing module, a first wireless communication transceiver unit, a second wireless communication transceiver unit, a first self-powered energy harvesting and power management module, and a first hinged mounting mechanism. The first current acquisition module, located inside the main control sensing unit, is used for non-contact measurement of the instantaneous current value of the conductor in its current phase and converts the analog electrical signal into a digital measurement sequence. The first central processing module is electrically connected to the first current acquisition module, and its core functions include performing system-level synchronization timing, data fusion, fault feature extraction, and communication protocol stack management. The first wireless communication transceiver unit, connected to the first central processing module, is used to establish a local high-speed, low-power wireless communication link, dedicated to broadcasting synchronization timing commands and collecting measurement data from each phase. The second wireless communication transceiver unit, connected to the first central processing module, is used to upload processed fault information or system status data to a remote monitoring center via a public wireless network. The first self-powered energy harvesting and power management module senses electrical energy from the conductor in its current phase and provides stable power to the various electronic components within the main control sensing unit. The first opening and closing mounting mechanism is used to quickly and securely fix the main control sensing unit to the busbar conductor in a non-invasive manner.

[0009] Furthermore, the driven sensing unit includes a second current acquisition module, a second central processing module, a third wireless communication transceiver unit, a second self-powered energy harvesting and power management module, and a second hinged mounting mechanism. The second current acquisition module is located inside the driven sensing unit and has the same structure and function as the first current acquisition module, used to measure the current in its phase conductor. The second central processing module is electrically connected to the second current acquisition module, and its core function is to receive synchronization commands from the master sensing unit, perform synchronous acquisition and preliminary processing of local current signals, and report data to the master sensing unit through the third wireless communication transceiver unit. The third wireless communication transceiver unit is connected to the second central processing module and is used to receive synchronization commands broadcast by the master sensing unit and upload locally acquired data. The functions of the second self-powered energy harvesting and power management module and the second hinged mounting mechanism are the same as those of the first self-powered energy harvesting and power management module and the first hinged mounting mechanism, respectively.

[0010] Specifically, both the first and second current acquisition modules consist of a Rogowski coil sensor, a precision integration and signal conditioning circuit, and an analog-to-digital converter. The Rogowski coil sensor comprises a non-magnetic flexible frame made of polyethylene terephthalate (PET), and an induction coil uniformly wound on the frame using 0.05mm diameter enameled copper wire at a density of 2000 turns per meter. The precision integration and signal conditioning circuit is connected to the output of the induction coil via a dual-core shielded cable. This circuit includes a precision integration circuit consisting of a chopper-stabilized operational amplifier with an input offset voltage below 1μV and a temperature drift coefficient less than 0.01μV / ℃. A second-order Butterworth low-pass filter is connected in series after the integration circuit, with its -3dB cutoff frequency set to 5kHz, to filter out high-frequency noise. Following the filter is a differential drive circuit to convert the single-ended signal into a differential signal output. The analog-to-digital converter is a synchronous sampling SARADC with 16-bit resolution. Its input is connected to the output of the differential drive circuit. The sampling rate is precisely set to 25.6 thousand samples per second, and the converted digital sequence is transmitted to the corresponding central processing module through a serial peripheral interface.

[0011] The high-precision synchronization acquisition between the master and slave sensing units is achieved through a closed-loop time calibration mechanism based on local wireless broadcasting. The first central processing module integrates a high-precision clock source, which consists of a temperature-compensated crystal oscillator (TCXO) with a frequency of 32.768MHz and a frequency stability better than ±1.0ppm within an operating temperature range of -40℃ to +85℃, and a hardware timestamp counter. The first central processing module periodically broadcasts a fixed-structure synchronization frame to all slave sensing units at a fixed frequency of 2Hz via the first wireless communication transceiver unit. The data structure of the synchronization frame includes, in sequence: an 8-byte preamble, a 4-byte synchronization word, an 8-byte master unit local timestamp captured by the hardware timestamp counter at the moment of transmission, and a 2-byte cyclic redundancy check (CRC) code. Correspondingly, upon receiving the synchronization frame, the second central processing module immediately captures the arrival time of the frame in its local hardware timestamp counter, recording it as the slave unit's local timestamp. The second central processing module executes a time synchronization calibration algorithm. The core steps of this algorithm are as follows: First, based on the received local timestamp of the master control unit and the captured local timestamp of the slave unit, the instantaneous deviation between them is calculated. This instantaneous deviation is then input into a Kalman filter. The Kalman filter uses the frequency drift rate of the local TCXO as the state variable and the instantaneous time deviation as the observation variable to perform state estimation and updating, thereby obtaining an accurate estimate of the local clock frequency drift. Based on this estimate, the timing rate of the local hardware timestamp counter is fine-tuned by adjusting the frequency control word of the internal digital phase-locked loop (DPLL), thus ensuring that the local clock of the slave unit accurately tracks the local clock of the master control unit. Through this continuous closed-loop calibration, the time synchronization error of all slave sensing units relative to the master sensing unit is stably controlled within 1 microsecond. When the first central processing module issues a synchronization sampling command, this command contains a future, precise sampling execution timestamp. Upon receiving the instruction, all sensing units synchronously trigger their analog-to-digital converters to sample the data the instant their local clock reaches the specified timestamp, thereby ensuring a high degree of consistency of the three-phase current data in terms of time reference.

[0012] Furthermore, to achieve reliable and low-power local wireless communication, both the first and third wireless communication transceiver units employ wireless transceiver chips operating in the 433MHz ISM band, based on Direct Sequence Spread Spectrum (DSSS) and Gaussian Frequency Shift Keying (GFSK) modulation technologies. The transmit power of these chips is set to +10dBm, with a receive sensitivity better than -120dBm. Signal transmission and reception are achieved through an impedance-matched inverted-F type PCB antenna integrated within the device housing, ensuring a communication link budget of at least 20dB between master and slave units within a 10-meter range in the complex electromagnetic environment of the substation. The second wireless communication transceiver unit uses a cellular communication module supporting the LTE Cat-1 communication protocol, connected to the public mobile communication network via an external 3dBi gain rod antenna for uploading processed fault data.

[0013] To achieve extremely low power consumption, both the first and second central processing modules (CPUs) employ an event-driven, multi-level power state machine management strategy. The power state machine defines five distinct operating states: deep sleep, synchronous monitoring, synchronous sampling, transient analysis, and data reporting. In deep sleep, the CPU's core processor, most peripherals, and wireless transceiver units are either power-off or clock-gated, with only the internal 32kHz real-time clock (RTC) and a small portion of static random access memory (SRAM) used to store state variables maintained by power. The static operating current of the entire sensing unit is controlled below 5 microamps. In synchronous monitoring, the CPU is woken up by a timed RTC interrupt, for example, every 500 milliseconds. Upon wake-up, only the receiver of the low-power wireless transceiver unit is activated. Within a very short time window, such as 10 milliseconds, it listens for synchronization frames from the main sensing unit. If a valid frame is detected, it enters a time calibration process and returns to deep sleep; otherwise, it immediately returns to deep sleep. The average power consumption in this state is below 50 microamps. In synchronous sampling mode, upon receiving a synchronous sampling command or being triggered by a fault detection algorithm, the central processing module wakes up and starts its high-speed clock to precisely control the analog-to-digital converter to continuously sample at specified times, and stores the data into the internal RAM via direct memory access (DMA). This mode has high power consumption, but its duration is strictly limited; for example, a transient waveform recording lasts only 200 milliseconds. In transient analysis mode, after sampling is completed, the central processing module locally executes a fault feature extraction algorithm on the acquired data sequence. The algorithm includes: first, performing vector synthesis on the three-phase current measurement sequence to calculate the zero-sequence current component; second, performing discrete wavelet transform (DWT) on the zero-sequence current sequence to extract the modulus maxima and polarity of the first-level detail coefficients of the current signal under the db4 wavelet basis at the time of the fault occurrence, as a fault direction criterion; simultaneously, calculating the abrupt change in the effective value of the current within one power frequency cycle before and after the fault occurrence, as a criterion for the severity of the fault. By performing local calculations at the sensing terminal, only the extracted key fault feature vectors are transmitted instead of the original massive waveform data, greatly reducing the communication overhead of data reporting. In data reporting mode, the second wireless communication transceiver unit (LTE module) will only be activated after the transient analysis status of the main control sensing unit confirms a ground fault. This unit will then package the fault feature vectors of all three phases and report them to the remote monitoring center via the public network in one go. The LTE module immediately enters power-off mode after reporting.

[0014] In conjunction with the aforementioned low-power management strategy, both the first and second self-powered energy harvesting and power management modules employ a three-tiered composite energy architecture: "inductive energy harvesting + supercapacitor main energy storage + primary lithium battery backup." Each module includes a current transformer (CT) energy harvesting unit, an energy storage and voltage regulation unit, and a power path management unit. The CT energy harvesting unit consists of an open-type current transformer using permalloy as the core material, with a relative permeability greater than 80,000. Precision grinding at the opening minimizes the air gap reluctance after the magnetic circuit is closed. When a power frequency current of 5A or more flows through the busbar conductor, sufficient energy can be induced in its secondary winding. The induced AC current passes through a full-bridge rectifier circuit composed of Schottky diodes with ultra-low forward voltage drop and a filter capacitor, outputting DC current. The core of the energy storage and voltage regulation unit is a capacitor module consisting of six supercapacitors connected in series, each with a rated voltage of 2.7V and a rated capacitance of 10F. The total capacity of this module is 1.67F, capable of storing approximately 20 joules of energy. The rectified DC power charges the supercapacitor module through a synchronous boost-buck charging controller with maximum power point tracking (MPPT) capability. The charging controller also provides a stable 3.3V operating voltage to the backend system. The core of the power path management unit is a power management chip that integrates a low-dropout linear regulator, a battery protection circuit, and power switching logic. A 2400mAh, 3.6V lithium thionyl chloride primary battery is connected to the PMIC as a backup power source. During normal operation, the system is powered by the supercapacitor. When the busbar current is too low, causing the supercapacitor voltage to drop below a preset threshold, the PMIC can seamlessly switch the power path to the backup lithium battery within microseconds and automatically switch back after the supercapacitor voltage recovers, thus ensuring the sensor's continuous operation under extreme conditions such as system startup or prolonged low-load operation.

[0015] To adapt to the compact and high-potential installation environment within substations, both the first and second hinged installation mechanisms are designed as an integrated hinged structure. The main body of the housing is made of a polycarbonate and ABS engineering plastic alloy, reinforced with 15% glass fiber, giving it UL94 V-0 flame retardant properties and excellent mechanical strength. The housing consists of two halves connected by a stainless steel pin, allowing it to open and close more than 180 degrees around the axis. At the closed end of the housing, a bistable over-midpoint spring-loaded latch structure ensures a secure lock after installation. On the inner side of the housing, the surface in contact with the busbar conductor, two N42 neodymium iron boron permanent magnets are embedded, their surfaces treated with a nickel-copper-nickel triple-layer electroplating process for corrosion resistance. The permanent magnets are covered with a 1mm thick silicone rubber pad with a high coefficient of friction. This pad provides strong magnetic attraction while protecting the insulation layer on the busbar surface and further preventing sensor displacement under vibration. The entire installation process requires no tools, and operators can complete the opening, closing, locking, and clamping actions with one hand, greatly improving installation efficiency and safety.

[0016] The beneficial effects of this invention are:

[0017] This invention achieves high-precision three-phase synchronous data acquisition, long-term maintenance-free self-powered operation, reliable wireless data transmission, and non-intrusive rapid deployment through the aforementioned technical solutions. A closed-loop time calibration mechanism based on local wireless broadcasting ensures that the time synchronization error of all sensing units is stably controlled within 1 microsecond. A three-level composite energy architecture of "inductive energy harvesting + supercapacitor main energy storage + primary lithium battery backup" ensures the continuous operation of the sensors under various working conditions. DSSS and GFSK modulation technology in the 433MHz ISM band ensures reliable communication in complex electromagnetic environments. An integrated hinged mounting mechanism simplifies operation and greatly improves installation efficiency and safety. An event-driven multi-level power state machine management strategy significantly reduces the overall power consumption of the system and extends the service life of the equipment. Attached Figure Description

[0018] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0019] Figure 1 This is a schematic diagram of the system architecture provided in an embodiment of the present invention;

[0020] Figure 2 This is a block diagram of the internal module structure of the main control sensing unit in an embodiment of the present invention. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figure 1-2 As shown, a wireless-based three-phase synchronous grounding fault indication sensor for substations includes a master control sensing unit 100 and at least two slave sensing units 200. The master control sensing unit 100 and the slave sensing units 200 are physically independent but form a collaborative working system via wireless communication, and are respectively installed on the three-phase conductors of the substation busbar. The master control sensing unit 100 includes a first current acquisition module 110, a first central processing module 120, a first wireless communication transceiver unit 130, a second wireless communication transceiver unit 140, a first self-powered energy extraction and power management module 150, and a first hinged mounting mechanism 160. The slave sensing units 200 include a second current acquisition module 210, a second central processing module 220, a third wireless communication transceiver unit 230, a second self-powered energy extraction and power management module 240, and a second hinged mounting mechanism 250.

[0023] S1: The first current acquisition module 110 of the main control sensing unit 100 is internally located and is used for non-contact measurement of the instantaneous current value of the conductor in the current phase, and converts the analog electrical signal into a digital measurement sequence. The first current acquisition module 110 consists of a Rogowski coil sensor, a precision integration and signal conditioning circuit, and an analog-to-digital converter. The Rogowski coil sensor includes a non-magnetic flexible frame made of polyethylene terephthalate and an induction coil uniformly wound on the frame using 0.05mm diameter enameled copper wire at a density of 2000 turns per meter. The output of the induction coil is connected to the precision integration and signal conditioning circuit via a two-core shielded cable. This circuit includes a precision integration circuit consisting of a chopper-stabilized operational amplifier with an input offset voltage of less than 1μV and a temperature drift coefficient of less than 0.01μV / ℃. A second-order Butterworth low-pass filter is connected in series after the integration circuit, with its -3dB cutoff frequency set to 5kHz, to filter out high-frequency noise. Following the filter is a differential drive circuit, used to convert the single-ended signal into a differential signal output. The analog-to-digital converter is a synchronous sampling SARADC with 16-bit resolution. Its input is connected to the output of the differential drive circuit, the sampling rate is precisely set to 25.6 kilosamples per second, and the converted digital sequence is transmitted to the first central processing module 120 through a serial peripheral interface.

[0024] S2: The first central processing module 120 is electrically connected to the first current acquisition module 110. Its core functions are to perform system-level synchronization timing, data fusion, fault feature extraction, and communication protocol stack management. The first central processing module 120 integrates a high-precision clock source, which consists of a temperature-compensated crystal oscillator with a frequency of 32.768MHz and a frequency stability better than ±1.0ppm within an operating temperature range of -40℃ to +85℃, and a hardware timestamp counter. The first central processing module 120 periodically broadcasts a fixed-structure synchronization timing frame to all slave sensing units 200 at a fixed frequency of 2Hz through the first wireless communication transceiver unit 130. The data structure of the synchronization timing frame includes, in sequence: an 8-byte preamble, a 4-byte synchronization word, an 8-byte local timestamp of the master control unit captured by the hardware timestamp counter at the moment of transmission, and a 2-byte cyclic redundancy check code. The first wireless communication transceiver unit 130 is connected to the first central processing module 120 and is used to establish a local high-speed, low-power wireless communication link, which is dedicated to broadcasting synchronization timing commands and collecting measurement data of each phase.

[0025] S3: The second current acquisition module 210 of the slave sensing unit 200 is internally located. Its structure and function are the same as the first current acquisition module 110, and it is used to measure the current of the conductor in its phase. The second central processing module 220 is electrically connected to the second current acquisition module 210. Its core function is to receive synchronization commands from the master sensing unit 100, perform synchronous acquisition and preliminary processing of local current signals, and report data to the master sensing unit 100 through the third wireless communication transceiver unit 230. The third wireless communication transceiver unit 230 is connected to the second central processing module 220 and is used to receive the synchronization timing frame broadcast by the master sensing unit 100 and upload the locally acquired data. After receiving the synchronization timing frame, the second central processing module 220 immediately captures the arrival time of the frame in its local hardware timestamp counter and records it as the slave unit's local timestamp. The second central processing module 220 executes a time synchronization calibration algorithm. The core steps of this algorithm are as follows: First, based on the received local timestamp of the master control unit and the captured local timestamp of the slave unit, the instantaneous deviation between the two is calculated. Second, this instantaneous deviation is input into a Kalman filter. The Kalman filter uses the frequency drift rate of the local TCXO as the state variable and the instantaneous time deviation as the observation variable to perform state estimation and update, thereby obtaining an accurate estimate of the local clock frequency drift. Based on this estimate, the timing rate of the local hardware timestamp counter is fine-tuned by adjusting the frequency control word of the internal digital phase-locked loop, so that the local clock of the slave unit accurately tracks the local clock of the master control unit. Through this continuous closed-loop calibration, the time synchronization error of all slave sensing units 200 relative to the master control sensing unit 100 is stably controlled within 1 microsecond.

[0026] S4: Both the first wireless communication transceiver unit 130 and the third wireless communication transceiver unit 230 employ wireless transceiver chips operating in the 433MHz ISM band, based on direct sequence spread spectrum and Gaussian frequency shift keying modulation technology. The transmit power of the wireless transceiver chip is set to +10dBm, and the receive sensitivity is better than -120dBm. Signal transmission and reception are performed through an impedance-matched inverted-F type PCB antenna integrated inside the device housing, ensuring that the communication link budget between the master and slave units within a 10-meter range has a margin of no less than 20dB in the complex electromagnetic environment of the substation. The second wireless communication transceiver unit 140 employs a cellular communication module supporting the LTE Cat-1 communication protocol. It connects to the public mobile communication network through an external rod antenna with a gain of 3dBi for uploading processed fault data.

[0027] S5: Both the first central processing module 120 and the second central processing module 220 execute an event-driven multi-level power state machine management strategy. The power state machine defines five strictly distinguished operating states: deep sleep state, synchronous listening state, synchronous sampling state, transient analysis state, and data reporting state. In deep sleep state, the core processor of the central processing module, most peripherals, and wireless communication transceiver units are in a power-off or clock-gated state. Only the internal 32kHz real-time clock and a small portion of static random access memory used to store state variables are powered. At this time, the static operating current of the entire sensing unit is controlled below 5 microamps. In synchronous listening state, the central processing module is woken up by an RTC timer interrupt, for example, every 500 milliseconds. After waking up, only the receiver of the low-power wireless transceiver unit is turned on. Within a very short time window, such as 10 milliseconds, it listens for the synchronization time frame from the main control sensing unit 100. If a valid frame is detected, it enters the time calibration process and then returns to deep sleep; if no frame is detected, it immediately returns to deep sleep. The average power consumption in this state is less than 50 microamps. In synchronous sampling mode, upon receiving a synchronous sampling command or being triggered by a fault detection algorithm, the central processing module wakes up and starts its high-speed clock to precisely control the analog-to-digital converter to continuously sample at specified times, storing the data into the internal RAM via direct memory access. This mode has high power consumption but its duration is strictly limited; for example, a transient waveform recording lasts only 200 milliseconds. In transient analysis mode, after sampling is completed, the central processing module locally executes a fault feature extraction algorithm on the acquired data sequence. The algorithm includes: first, performing vector synthesis on the three-phase current measurement sequence to calculate the zero-sequence current component; second, performing discrete wavelet transform on the zero-sequence current sequence to extract the modulus maxima and polarity of the first-level detail coefficients of the current signal at the time of fault occurrence under the db4 wavelet basis, as a fault direction criterion; simultaneously, calculating the abrupt change in the effective current value within one power frequency cycle before and after the fault occurrence, as a criterion for fault severity. By performing local calculations at the sensing terminal, only the extracted key fault feature vectors are transmitted instead of the original massive waveform data, greatly reducing the communication overhead of data reporting. In data reporting mode, the second wireless communication transceiver unit 140 (LTE module) will only be activated after the transient analysis status of the main control sensor unit 100 confirms a ground fault. It will then package all three-phase fault feature vectors and report them to the remote monitoring center via the public network in one go. The LTE module immediately enters power-off mode after reporting.

[0028] S6: Both the first self-powered energy harvesting and power management module 150 and the second self-powered energy harvesting and power management module 240 adopt a three-level composite energy architecture of "inductive energy harvesting + supercapacitor main energy storage + primary lithium battery backup". The module includes a current transformer (CT) energy harvesting unit, an energy storage and voltage regulation unit, and a power path management unit. The CT energy harvesting unit consists of an open-type current transformer using permalloy as the magnetic core material, with a relative permeability greater than 80,000. The opening is precision-ground to minimize the air gap magnetic reluctance after the magnetic circuit is closed. When a power frequency current of 5A or more flows through the busbar conductor, its secondary winding can induce sufficient energy. The induced AC current passes through a full-bridge rectifier circuit composed of Schottky diodes with ultra-low forward voltage drop and a filter capacitor, outputting DC current. The core of the energy storage and voltage regulation unit is a capacitor module consisting of six supercapacitors with a rated voltage of 2.7V and a rated capacitance of 10F connected in series. The total capacity of this module is 1.67F, capable of storing approximately 20 joules of energy. The rectified DC power charges the supercapacitor module through a synchronous boost-buck charging controller with maximum power point tracking (MPPT). The charging controller also provides a stable 3.3V operating voltage to the backend system. The core of the power path management unit is a power management chip (PMIC), which integrates a low-dropout linear regulator, a battery protection circuit, and power switching logic. A 2400mAh, 3.6V lithium thionyl chloride primary battery is connected to the PMIC as a backup power source. During normal operation, the system is powered by the supercapacitor. When the busbar current is too low, causing the supercapacitor voltage to drop below a preset threshold, the PMIC can seamlessly switch the power path to the backup lithium battery within microseconds and automatically switch back after the supercapacitor voltage recovers. This ensures the sensor's continuous operation under extreme conditions such as system startup or prolonged low-load operation.

[0029] S7: Both the first and second opening / closing mounting mechanisms 160 and 250 are designed as an integrated hinged structure. The main body of the housing is made of a polycarbonate and ABS engineering plastic alloy, reinforced with 15% glass fiber, giving it UL94 V-0 flame retardant properties and excellent mechanical strength. The housing consists of two halves connected by a stainless steel pin, allowing it to open and close more than 180 degrees around the axis. At the closed end of the housing, a bistable over-midpoint spring-loaded latch structure ensures a secure lock after installation. On the inner side of the housing, the surface in contact with the busbar conductor, two N42 neodymium iron boron permanent magnets are embedded, their surfaces treated with a nickel-copper-nickel triple-layer electroplating process for corrosion resistance. The permanent magnets are covered with a 1mm thick silicone rubber gasket with a high coefficient of friction. This gasket provides strong magnetic attraction while protecting the insulation layer on the busbar surface and further preventing sensor displacement under vibration. The entire installation process requires no tools, and operators can complete the opening, closing, locking, and clamping actions with one hand, greatly improving installation efficiency and safety.

[0030] Through the above implementation methods, this invention achieves the technical effects of high-precision three-phase synchronous acquisition, long-term maintenance-free self-powered operation, reliable wireless data transmission, and non-intrusive rapid deployment. A closed-loop time calibration mechanism based on local wireless broadcasting ensures that the time synchronization error of all sensing units is stably controlled within 1 microsecond. A three-level composite energy architecture of "inductive energy harvesting + supercapacitor main energy storage + primary lithium battery backup" ensures the continuous operation of the sensors under various working conditions. DSSS and GFSK modulation technology in the 433MHz ISM band ensures reliable communication in complex electromagnetic environments. The integrated hinged installation mechanism is easy to operate, greatly improving installation efficiency and safety. An event-driven multi-level power state machine management strategy significantly reduces the overall power consumption of the system and extends the service life of the equipment.

[0031] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A wireless-based three-phase synchronous grounding fault indication sensor for use in substations, characterized in that, It includes a master control sensing unit (100) and at least two slave sensing units (200), the master control sensing unit (100) and the slave sensing units (200) work together via wireless communication and are respectively installed on the three-phase conductors of the substation busbar; the master control sensing unit (100) includes a first current acquisition module (110), a first central processing module (120), a first wireless communication transceiver unit (130), a second wireless communication transceiver unit (140), a first self-powered energy and power management module (150) and a first openable installation mechanism (160); the slave sensing unit (200) includes a second current acquisition module (210), a second central processing module (220), a third wireless communication transceiver unit (230), a second self-powered energy and power management module (240) and a second openable installation mechanism (250).

2. The wireless-based three-phase synchronous grounding fault indication sensor in a substation according to claim 1, characterized in that, The first current acquisition module (110) and the second current acquisition module (210) are both composed of a Rogowski coil sensor, a precision integration and signal conditioning circuit and an analog-to-digital converter. The Rogowski coil sensor includes a non-magnetic flexible frame made of polyethylene terephthalate and an induction coil wound on the frame.

3. The wireless-based three-phase synchronous grounding fault indication sensor in a substation according to claim 2, characterized in that, The induction coil is made of enameled copper wire with a diameter of 0.05mm, wound uniformly at a density of 2000 turns per meter.

4. The wireless-based three-phase synchronous grounding fault indication sensor in a substation according to claim 1, characterized in that, The first central processing module (120) integrates a clock source, which consists of a temperature-compensated crystal oscillator with a frequency of 32.768MHz and a hardware timestamp counter.

5. The wireless-based three-phase synchronous grounding fault indication sensor in a substation according to claim 4, characterized in that, The first central processing module (120) periodically broadcasts a synchronization time frame through the first wireless communication transceiver unit (130) at a fixed frequency of 2Hz. The synchronization time frame includes a preamble, a synchronization word, a local timestamp of the main control unit, and a cyclic redundancy check code.

6. The wireless-based three-phase synchronous grounding fault indication sensor in a substation according to claim 1, characterized in that... Both the first wireless communication transceiver unit (130) and the third wireless communication transceiver unit (230) use wireless transceiver chips operating in the 433MHz ISM band. The transmit power of the wireless transceiver chip is set to +10dBm, and the receive sensitivity is better than -120dBm.

7. The wireless-based three-phase synchronous grounding fault indication sensor in a substation according to claim 1, characterized in that, Both the first self-powered energy harvesting and power management module (150) and the second self-powered energy harvesting and power management module (240) adopt a three-level composite energy architecture, including a CT energy harvesting unit, an energy storage and voltage regulation unit, and a power path management unit.

8. The wireless-based three-phase synchronous grounding fault indication sensor in a substation according to claim 7, characterized in that, The CT energy harvesting unit is composed of an open-type current transformer, whose core material is permalloy with a relative permeability greater than 80,000.

9. The wireless-based three-phase synchronous grounding fault indication sensor in a substation according to claim 1, characterized in that, Both the first and second opening and closing mounting mechanisms (160 and 250) are designed as hinged structures.

10. The wireless-based three-phase synchronous grounding fault indication sensor in a substation according to claim 9, characterized in that, Two neodymium iron boron permanent magnets are pre-embedded on the inner side of the first and second opening and closing installation mechanisms (160) and the permanent magnets are covered with a layer of silicone rubber pad with a thickness of 1mm.

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