Temperature measuring plug for cable joint of ring main unit

Abstract

The utility model belongs to the technical field of power equipment cable joints, and discloses a ring main unit cable joint temperature measurement plug which comprises a cable plug and an internal temperature measurement sensor insert. An internal temperature measurement sensor insert is arranged in the cable plug, and the cable plug and the internal temperature measurement sensor insert form a non-detachable whole through an integrated pouring process; the cable plug is made of insulating epoxy resin; the internal temperature measurement sensor insert comprises a high-voltage insert, a core circuit board, a low-voltage insert and a grading ring; the high-voltage insert and the low-voltage insert are arranged in an inserted and matched mode, and a core circuit board is arranged between the high-voltage insert and the low-voltage insert. According to the utility model, the temperature measurement accuracy and the response speed are both excellent, and the problem of large indirect temperature measurement error is solved; an extra power supply part is not needed, a coupling capacitor of a high-voltage insert and a low-voltage insert is matched with an inherent ground distributed capacitor of a cable system to form a voltage-dividing energy-taking loop, a battery and an external energy-taking coil are not needed, and the maintenance burden of regularly replacing the battery is thoroughly eliminated; and an existing plug is seamlessly replaced.

Description

Technical Field

[0001] This application relates to the field of power equipment cable joint technology, and more specifically, to temperature measuring plugs for ring main unit cable joints. Background Technology

[0002] Currently, during actual use, the internal temperature of cable accessories in ring main units often rises abnormally due to construction issues or operating environment. While temperature measurement can be achieved using sensors attached to the outside of the cable accessories, it is difficult to monitor the actual temperature of cable joints inside the distribution ring main unit (box) during operation. Defects such as overheating of joints are difficult to detect in a timely manner, easily leading to power distribution cable faults.

[0003] Existing technology publication CN110176743A discloses an insulating plug for a cable joint with temperature measurement function, belonging to the technical field of power equipment cable joints. It includes a plug body, a terminal block, a cable, and a terminal head. The plug body has a cavity, within which a protective sleeve is installed. The protective sleeve includes an insulating sleeve and an epoxy resin sleeve, with the epoxy resin sleeve covering the outside of the insulating sleeve. The insulating sleeve is filled with chlorinated paraffin, and a metal connector is located inside the insulating sleeve. The terminal head is securely connected to the metal connector. A first opening is provided on the side of the protective sleeve away from the terminal head, and a second opening communicating with the cavity is provided on the plug body. A sealing plate is securely installed in the second opening. Two temperature detection devices are symmetrically installed on the side of the metal connector away from the terminal head. This invention solves the problems of difficult replacement and flammability of temperature monitoring devices on existing insulating plugs, saving resources while maintaining a stable and compact structure.

[0004] Although the existing technical solutions mentioned above can achieve the relevant beneficial effects through the existing technical structure, they still have the following defects: they cannot directly sense the temperature of the internal electrical connection points, and cannot directly contact the internal electrical connection points of the cable, resulting in inaccurate temperature measurement; the existing devices have simple internal component fixing methods and no anti-vibration design, and long-term operation is prone to component displacement and circuit board desoldering and breakage due to vibration; they lack efficient heat dissipation structure, and core components are prone to failure due to high temperature.

[0005] In view of this, we propose a temperature measuring plug for the cable joint of the ring main unit. Utility Model Content

[0006] 1. The technical problems to be solved.

[0007] The purpose of this application is to provide a temperature measuring plug for cable joints in ring main units, which solves the technical problems mentioned in the background art. It realizes zero-distance temperature measurement by directly attaching the high-voltage insert to the internal electrical connection point of the cable and combining it with a high thermal conductivity ceramic column; it solves the problems of inaccurate temperature measurement and lag response of existing external sensors; the three-stage stepped power extraction structure of the low-voltage insert increases the power extraction area and improves coupling efficiency, and can still stably extract energy under low operating conditions with cable load ≤10%; combined with supercapacitor energy storage, it can continuously supply power for forty minutes after power failure, avoiding the loss of critical temperature data; the double helical groove and barb design of the high-voltage insert and the annular groove structure of the low-voltage insert form a firm mechanical engagement with the plug shell, which has the technical effect of resisting vibration and displacement.

[0008] 2. Technical solution.

[0009] This application provides a temperature-sensing plug for a ring main unit cable joint, comprising: a cable plug and an internal temperature sensor insert. The internal temperature sensor insert is fixedly installed inside the cable plug, and the two are integrated into a single, inseparable structure through a casting process, ensuring mechanical strength while avoiding electric field distortion caused by assembly gaps. The cable plug is made of insulating epoxy resin; the internal temperature sensor insert is fixedly installed inside the cable plug through casting.

[0010] As an optional solution of this utility model, the internal temperature sensor insert includes a high-voltage insert, a core circuit board, a low-voltage insert, and an equalizing ring.

[0011] The high-voltage and low-voltage inserts are connected and mated, with a core circuit board positioned between them. The high-voltage insert includes a nest and a connecting support post. The connecting support post is fixedly mounted on the nest. Threaded holes are provided on the nest and the connecting support post, through which the high-voltage insert connects to an external cable connection screw.

[0012] An equalizing ring is disposed on the outside of the high-voltage insert; three miniature conductive posts are evenly distributed on the inside of the equalizing ring, and the miniature conductive posts are connected to the high-voltage insert. The equalizing ring is made of semiconductor ceramic. The miniature conductive posts are made of a metal with excellent conductivity, preferably H62 brass.

[0013] In actual use, the high-voltage insert's threaded structure is connected to the cable connection screw. The high-voltage insert supports other internal inserts and forms one pole of the capacitor voltage divider plate in the voltage insert's power extraction circuit.

[0014] The core circuit board integrates a temperature sensing module, a wireless module, and a power module, enabling the cable accessories to have temperature sensing capabilities. They are directly fixed to the high-voltage insert via an epoxy resin insulation board, while the power module is connected to the low-voltage insert to achieve passive induction energy harvesting from the electric field.

[0015] As an optional embodiment of this utility model, the nest is shaped like a frustum, with a double helical groove on the outer side. Three sets of barbed anti-slip teeth are installed within the double helical groove, with an inclination angle of 45 degrees. During casting, modified epoxy resin fills the double helical groove and barbs, forming a dual mechanical fixation of helical engagement and barb locking, preventing relative displacement caused by long-term vibration.

[0016] Multiple heat dissipation fins are fixedly mounted on the outer side of the nest. The surface of the heat dissipation fins is treated with nickel plating passivation. After casting, the heat dissipation fins and modified epoxy resin form a thermally conductive path, which conducts the heat of the core circuit board to the outside through the insert, improving heat dissipation efficiency and avoiding circuit failure caused by high temperature.

[0017] As an optional solution of this utility model, a stepped hole is provided on the connecting support column, and a high thermal conductivity ceramic column is placed in the stepped hole. One end of the high thermal conductivity ceramic column is directly attached to the cable connecting screw, and the other end is connected to the temperature sensing module of the core circuit board through an elastic conductive sheet. This achieves zero-distance temperature measurement at the internal electrical connection point.

[0018] As an optional solution of this utility model, the connecting support column is vertically fixed at the center position of the nest, and has a stepped shaft structure, including a positioning and fitting section and a threaded connection section.

[0019] As an optional solution of this utility model, the core circuit board is a circular PCB board, which uses FR-4 epoxy fiberglass board as the substrate.

[0020] As an optional solution of this utility model, the core circuit board is fixed to the nest of the high-voltage insert by two epoxy resin insulating pads. The insulating pads adopt a slot-type connection and are sealed with high-temperature resistant epoxy potting compound, which not only ensures that the circuit board is firmly fixed, but also maintains an insulating distance between the circuit board and the high-voltage insert to avoid high-voltage breakdown.

[0021] Silicone buffer pads are provided above and below the core circuit board; the power module of the core circuit board is connected to the conductive pins of the low-voltage insert by two silver-plated copper wires, and the copper wires are covered with polytetrafluoroethylene insulating sleeves to prevent electrical short circuits with other components.

[0022] Multiple L-shaped insulating elastic arms are provided on the upper silicone buffer pad. The L-shaped insulating elastic arms are made of glass fiber reinforced PPS. One end of the multiple L-shaped insulating elastic arms is connected to the heat sink fins of the high voltage insert, and the other end is clamped to the core circuit board through the silicone buffer pad.

[0023] As an optional solution of this utility model, the low-pressure insert material is selected as H62 brass.

[0024] The low-voltage insert has a countersunk hole. Two flexible conductive leads are located at the top of the low-voltage insert.

[0025] As an optional solution of this utility model, the lower part of the low-pressure insert is provided with three steps, and several radial guide grooves are evenly distributed on the three steps.

[0026] The bottom of the low-voltage insert is provided with an elastic energy storage cavity; a supercapacitor assembly is provided inside the elastic energy storage cavity, and a spring is fixedly installed below the supercapacitor assembly.

[0027] 3. Beneficial effects.

[0028] One or more technical solutions provided in this application have at least the following technical effects or advantages.

[0029] 1. Accurate and efficient temperature measurement: The high-voltage insert is directly attached to the internal electrical connection point of the cable, and a high thermal conductivity ceramic column is used to achieve zero-distance temperature measurement; solving the problems of inaccurate temperature measurement and slow response of existing external sensors.

[0030] 2. Stable passive power extraction with no additional maintenance required: The low-voltage insert three-stage stepped power extraction structure increases the power extraction area and improves coupling efficiency. It can still extract power stably under low operating conditions with cable load ≤10%. With supercapacitor energy storage, it can provide power for 40 minutes after a power outage, avoiding the loss of critical temperature data.

[0031] 3. Compatible with existing structures and extremely low installation costs: It fully adopts the external dimensions, installation interface and sealing structure of existing standard plugs, and can directly replace ordinary plugs without modifying the ring main unit cabinet or cable joints; the modular integrated design simplifies the assembly process, reduces construction difficulty, significantly reduces replacement costs, and adapts to the needs of upgrading existing equipment.

[0032] 4. Stable and durable structure, suitable for harsh environments: The high-voltage insert features a double helical groove and barb design, while the low-voltage insert has an annular groove structure, forming a firm mechanical engagement with the plug housing to resist vibration and displacement; the L-shaped insulating elastic arm and silicone buffer pad absorb vibration energy, preventing circuit board desoldering and breakage; heat dissipation fins improve heat conduction efficiency, the chip is coated with conformal coating, and the electromagnetic shielding layer suppresses interference, making it suitable for industrial scenarios with humid, dusty, and strong electromagnetic interference, thus extending its service life. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the high-voltage insert, core circuit board, and low-voltage insert of a ring main unit cable connector temperature measuring plug disclosed in a preferred embodiment of this application.

[0034] Figure 2 This is a schematic diagram of the internal temperature sensor insert of the temperature measuring plug of the ring main unit cable joint disclosed in a preferred embodiment of this application.

[0035] Figure 3 This is a schematic diagram of the overall temperature measuring plug of the ring main unit cable joint disclosed in a preferred embodiment of this application.

[0036] Figure 4 This is a schematic diagram of a high-voltage insert for a temperature measuring plug on a ring main unit cable connector, as disclosed in a preferred embodiment of this application.

[0037] Figure 5 This is a schematic diagram of a low-voltage insert for a temperature measuring plug of a ring main unit cable connector, as disclosed in a preferred embodiment of this application.

[0038] Figure 6 This is a schematic diagram of the equalizing ring of the temperature measuring plug of the cable joint of the ring main unit disclosed in a preferred embodiment of this application.

[0039] Reference numerals: 1. Cable plug; 2. High-voltage insert; 3. Core circuit board; 4. Low-voltage insert; 5. Equalizing ring; 6. L-shaped insulating elastic arm; 7. High thermal conductivity ceramic pillar; 8. Silicone buffer pad; 9. Supercapacitor assembly; 10. Spring; 21. Nesting; 22. Connecting support pillar; 23. Threaded hole; 24. Double helical groove; 25. Heat sink fin; 26. Stepped hole; 41. Countersunk hole; 42. Three-stage step; 43. Radial guide channel; 44. Elastic energy storage cavity; 51. Miniature conductive pillar. Detailed Implementation

[0040] The present application will be further described in detail below with reference to the accompanying drawings.

[0041] This application provides a temperature measuring plug for a ring main unit cable joint, which aims to solve the technical problems of existing temperature measuring solutions for ring main unit cable accessories being unable to directly sense the temperature of internal electrical connection points and the ease with which external sensors can damage insulation and partial discharge performance. Through modular integrated design and passive power extraction, it achieves the triple goals of accurate temperature measurement, compatibility with the original structure, and compliance with partial discharge standards.

[0042] Reference Figure 1 , Figure 2 and Figure 3 This application provides a temperature-sensing plug for a ring main unit cable connector, comprising: a cable plug 1 and an internal temperature sensor insert. The two are integrated into a single, inseparable structure through a casting process, ensuring mechanical strength while avoiding electric field distortion caused by assembly gaps.

[0043] An internal temperature sensor insert is fixedly installed inside the cable plug 1. The material of the cable plug 1 is insulating epoxy resin. The internal temperature sensor insert is fixedly installed inside the cable plug 1 by casting.

[0044] The internal temperature sensor insert transmits the measured temperature data to an external receiver via wireless communication.

[0045] Cable plug 1 has an insulating outer shell and is made using a matching mold of existing standard cable accessory plugs. It is cast in one piece using epoxy resin under high temperature and pressure, without altering the original plug's shape, dimensions, installation interface, or sealing structure. This ensures that the temperature measuring plug can directly replace existing ordinary cable plugs without requiring any modifications to the ring main unit or cable joints, reducing construction difficulty and replacement costs. Its structure and appearance are completely identical to existing cable accessory plugs, preserving their structural characteristics and maintaining their existing partial discharge levels.

[0046] The cable plug 1 is made of modified epoxy resin composite material, specifically bisphenol A type epoxy resin with added nano-alumina (particle size 50-100nm), cast at 80℃ and 15.0MPa high temperature and high pressure. The addition of nano-alumina increases the dielectric constant of the insulation material to 4.8-5.2, while the dielectric constant of ordinary epoxy resin is 3.5-4.0. This ensures that the insulation withstand voltage reaches AC42kV (meeting the requirements for 10kV ring main units). Through dielectric performance optimization, internal electric field distortion is reduced. Combined with the vacuum degassing process during casting, with a vacuum degree ≤-0.095MPa, it ensures that there are no air bubbles or shrinkage cavities inside the plug. Ultimately, under 10kV test conditions, the partial discharge value is <5.0pC, which is fully compatible with the insulation and partial discharge standards of existing cable accessories.

[0047] Reference Figure 2 , Figure 3 and Figure 6 The internal temperature sensor insert includes a high-voltage insert 2, a core circuit board 3, a low-voltage insert 4, and an equalizing ring 5.

[0048] The internal temperature sensor insert has a modular integrated structure. The high-voltage insert 2, the core circuit board 3, the low-voltage insert 4, and the equalizing ring 5 form a stable assembly through plug-in positioning and insulation isolation. Through the structural coordination of the four components, four functions are realized simultaneously: mechanical fixation, electric field energy harvesting, accurate temperature measurement, and wireless transmission, without changing the electric field distribution characteristics of the original plug.

[0049] The high-voltage insert 2 and the low-voltage insert 4 are connected and fitted together, and a core circuit board 3 is provided between the high-voltage insert 2 and the low-voltage insert 4.

[0050] The high-voltage insert 2 includes a nest 21 and a connecting support column 22.

[0051] A connecting support column 22 is fixedly installed on the nest 21. Threaded holes 23 are provided on the nest 21 and the connecting support column 22, and the high-voltage insert 2 is connected to the external cable connecting screw through the threaded holes 23.

[0052] A voltage equalization ring 5 is provided on the outside of the high voltage insert 2; three miniature conductive posts 51 are evenly distributed on the inside of the voltage equalization ring 5, and the miniature conductive posts 51 are connected to the high voltage insert 2.

[0053] The high-voltage insert 2 primarily serves a fixing function. In actual use, the threaded structure of the high-voltage insert is connected to the cable connection screw. The high-voltage insert 2 provides support for other internal inserts and forms one pole of the capacitor voltage divider plate in the voltage insert power supply circuit.

[0054] The core circuit board 3 integrates a temperature sensing module, a wireless module, and a power module, enabling the cable accessories to have temperature sensing capabilities. They are directly fixed to the high-voltage insert through an epoxy resin insulation board, and the power module is connected to the low-voltage insert to achieve passive induction energy harvesting from the electric field.

[0055] The low-voltage insert 4 is a key component for passive inductive energy harvesting from the electric field. The capacitor formed by the low-voltage insert 4, together with the inherent ground capacitance in the external cable system, forms a series voltage divider circuit, continuously transferring energy to the internal energy storage circuit. When the energy stored in the internal energy storage circuit meets the operating conditions, the sensing system and RF module are activated for data transmission. Simultaneously, the low-voltage insert 4 uses a rigid conductive material to avoid insufficient hardness in other media, altering the internal electric field distribution level during the casting process to ensure that partial discharge meets standard requirements.

[0056] In this technical solution, the high-voltage insert 2 is an integrally machined part, and the material is H62 brass, which ensures both rigid support and meets the conductivity requirements of the capacitor plate. The nest 21 and the connecting support column 22 are integrally formed structures to avoid contact resistance and electric field concentration caused by separate assembly.

[0057] Reference Figure 4 The nest 21 has a frustum-shaped structure, with its outer diameter precisely matching the internal cavity of the cable plug 1. The outer side of the nest 21 has a double helical groove 24, within which three sets of barbed anti-slip teeth are installed at a 45-degree angle. During casting, modified epoxy resin fills the double helical groove 24 and the barbs, forming a dual mechanical fixation of helical engagement and barb locking, preventing relative displacement caused by long-term vibration. A small amount of anaerobic adhesive, Loctite 638 (high-temperature resistant), is applied inside the double helical groove of the high-voltage insert. After curing, the anaerobic adhesive forms a strong bond with the epoxy and metal insert, preventing structural loosening that could lead to failure of temperature measurement and power extraction functions.

[0058] Multiple heat dissipation fins 25 are fixedly mounted on the outer side of the nest 21. The surface of the heat dissipation fins 25 is treated with nickel plating passivation. After casting, the heat dissipation fins 25 and the modified epoxy resin form a thermally conductive path, which conducts the heat of the core circuit board to the outside through the insert, thereby improving heat dissipation efficiency and avoiding circuit failure caused by high temperature.

[0059] Furthermore, a stepped hole 26 is provided on the connecting support column 22, and a high thermal conductivity ceramic column 7 with a thermal conductivity ≥300W / (mK) is installed inside the stepped hole 26. One end of the high thermal conductivity ceramic column 7 is directly attached to the cable connecting screw, and the other end is connected to the temperature sensing module of the core circuit board 3 through an elastic conductive sheet. This achieves zero-distance temperature measurement at the internal electrical connection point. A miniature pre-tightening spring made of phosphor bronze is provided at the end of the high thermal conductivity ceramic column, with a pre-tightening force of five to eight Newtons, to ensure surface contact between the ceramic column and the cable connecting screw and the elastic conductive sheet, avoiding contact gaps caused by long-term vibration.

[0060] Furthermore, the connecting support column 22 is vertically fixed at the center of the nest 21, and has a stepped shaft structure, including a positioning and fitting section and a threaded connection section. The outer circular surface roughness Ra of the positioning and fitting section is ≤0.8μm, which is used to form a clearance fit with the center hole of the low-pressure insert 4. The fit clearance is 0.03-0.05mm, which ensures smooth assembly and maintains the stability of electric field coupling through the extremely small clearance. The threaded connection section is provided with a fine thread hole for threaded connection with the external cable connection screw, so that the high-pressure insert 2 can directly fit against the internal electrical connection point of the cable, providing a short-distance conduction path for subsequent temperature measurement.

[0061] In this technical solution, the high-voltage insert 2 performs three functions simultaneously: ① Mechanical fixing: It is fixed to the cable screw through the threaded connection section and engages with the plug shell through the nest 21; ② Electric field plate: Its outer surface serves as the high-voltage plate of the capacitor voltage divider circuit, forming a coupling capacitor with the low-voltage insert 4; ③ Temperature conduction: It can quickly conduct the temperature of the internal electrical connection point of the cable to the temperature measurement module of the core circuit board 3, reducing temperature measurement lag. The lag time is ≤0.5s, solving the problem of lag and slow response of existing external sensors.

[0062] Furthermore, the core circuit board 3 is a circular PCB board, using FR-4 epoxy fiberglass board substrate with a dielectric strength ≥20kV / mm. The core circuit board 3 highly integrates the three major functional modules of temperature measurement, energy harvesting, and transmission, achieving a balance between electrical insulation, mechanical stability, and temperature conduction.

[0063] The core circuit board 3 integrates a temperature sensing module, a wireless module, and a power module.

[0064] Temperature sensing module: Utilizing a surface-mount NTC thermistor with an accuracy of ±0.1℃, it is directly soldered to the side of the core circuit board 3 facing the high-voltage insert 2. The thermistor's leads are connected to the circuit board's copper foil via a silver-plated copper layer (thickness ≥35μm). This silver plating reduces contact thermal resistance, enabling the thermistor to quickly respond to the temperature conducted by the high-voltage insert 2. The NTC thermistor is tightly bonded to the surface of the high-voltage insert's nest 21 via thermally conductive silicone, and simultaneously abuts against the high-thermal-conductivity ceramic pillar 7 via an elastic conductive sheet, forming a dual temperature conduction path. The thermally conductive silicone thickness is ≤0.5mm, further reducing contact thermal resistance and ensuring a temperature measurement lag time ≤0.3s.

[0065] Wireless Module: Utilizes LoRa wireless communication technology for wireless data transmission. An industrial-grade LoRa RF chip (preferred models: SX1276 / SX1278 or domestic ASR6501) is selected, operating at 433MHz, fully adaptable to the wireless communication requirements of ring main unit industrial scenarios. The specific design is as follows.

[0066] Chip selection and performance parameters: The QFN-28 packaged chip is selected, which is compatible with the compact layout of the core circuit board. Its transmit power can be adjusted within the range of 1dBm~10dBm; the receive sensitivity is far superior to traditional RF chips, and the anti-electromagnetic interference capability is outstanding.

[0067] Integrated antenna design: A serpentine PCB antenna is used, arranged along the outer edge of the circular PCB board. The total antenna length is 16 cm, suitable for 1 / 4 wavelength in the 433MHz band. The antenna is modified with FR-4 substrate dielectric constant, has a line width of 1.5 mm, and is formed by etching 35.0 μm thick copper foil. The antenna maintains an electrical clearance of ≥5 mm from the temperature measurement module and power module on the core circuit board to avoid electromagnetic coupling interference. A π-type impedance matching network (consisting of two 0402 packaged surface-mount capacitors and one 0402 packaged surface-mount inductor) is added between the LoRa chip antenna pins and the PCB antenna to precisely match the antenna impedance to 50Ω, ensuring maximum efficiency in RF energy transmission.

[0068] Employing CSS spread spectrum modulation technology, it supports an adjustable spreading factor (SF) of 7.0-12.0, with a default setting of SF9, balancing communication distance and power consumption. The bandwidth is set to 125kHz, and with forward error correction coding (FEC), it effectively resists strong electromagnetic interference generated by frequency converters and high-voltage equipment in power scenarios, achieving a data transmission success rate of ≥99%. In unobstructed scenarios, the communication distance is ≥300m; in scenarios with metal enclosures in the ring main unit, the communication distance is ≥100m, meeting the needs of centralized deployment of multiple ring main units. A single LoRa gateway can cover fifty to one hundred temperature monitoring points.

[0069] Employing a low-power design: the chip's sleep mode current is ≤2.0μA, the transmit mode current is approximately 18mA (at 10dBm power), and the receive mode current is approximately 12.0mA, perfectly compatible with the power module's 100μF tantalum capacitor and 3.3V voltage regulator chip. Data transmission adopts an intermittent operating mode of temperature measurement, transmission, and sleep. The data frame format is designed as a simplified structure of an eight-bit address code, a sixteen-bit temperature data, and an eight-bit CRC checksum, with a total length ≤16 bytes and a single data upload time ≤100ms. Combined with an adjustable temperature measurement cycle of one to ten minutes, the overall current in low-power sleep mode is ≤10.0μA, ensuring a stable passive power supply without the need for an additional battery.

[0070] A 0.1μF ceramic filter capacitor is connected in parallel between the power supply pin of the LoRa chip and ground to suppress electromagnetic interference on the power line; the core circuit board adopts a single-point grounding design, and the antenna area is separately grounded to reduce ground loop interference and ensure communication stability; the chip surface is coated with a three-proof paint (moisture-proof, salt spray-proof, and mildew-proof) to adapt to the humid and dusty operating environment of the ring main unit and extend its service life.

[0071] Power module: Includes rectifier bridge, filter capacitor, energy storage capacitor (tantalum capacitor, 100μF capacity, 25.0V withstand voltage) and low voltage regulator chip (output voltage 3.3V), used to convert the alternating voltage of induction energy into stable DC power to power the temperature measurement module and wireless module.

[0072] The temperature sensing module, wireless module, and power module are all existing technologies and are only used in this utility model, so they will not be described in detail here. All electronic components (LoRa chip, voltage regulator chip, NTC thermistor, tantalum capacitor, etc.) on the core circuit board 3 are industrial-grade products with a temperature resistance of ≥125℃ to ensure the stability of casting and long-term operation.

[0073] The power module is equipped with a set of overcharge and over-discharge protection chips, model DW01+8205A, surface mount package, directly soldered onto the PCB board; the protection chip can prevent the supercapacitor from being damaged by voltage fluctuations and ensure the energy storage function is stable for forty minutes after a power outage.

[0074] Furthermore, the core circuit board 3 is fixed to the nest 21 of the high-voltage insert 2 by two epoxy resin insulating pads. The insulating pads use a slot-type connection (two positioning notches are provided on the edge of the circuit board, which engage with the protrusions of the pads). Combined with high-temperature resistant epoxy potting compound for sealing, this ensures both a firm fixation of the circuit board and maintains an insulating distance between the circuit board and the high-voltage insert 2, preventing high-voltage breakdown. The core circuit board 3 is sealed with a high-temperature epoxy potting compound with a temperature resistance of ≥130℃ (e.g., DELOKATIOBOND EP620). After potting, it undergoes pre-curing at 80 degrees Celsius for two hours to ensure that the circuit board components are not affected during subsequent medium-temperature casting.

[0075] Silicone buffer pads 8 are provided above and below the core circuit board 3; the power module of the core circuit board 3 is connected to the conductive pins of the low-voltage insert 4 by two silver-plated copper wires, and the copper wires are covered with polytetrafluoroethylene insulating sleeves to prevent electrical short circuits with other components.

[0076] Multiple L-shaped insulating elastic arms 6 are provided on the upper silicone buffer pad 8. The L-shaped insulating elastic arms 6 are made of glass fiber reinforced PPS. One end of the multiple L-shaped insulating elastic arms 6 is snapped into the heat sink fins 25 of the high-voltage insert, and the other end is clamped to the core circuit board through the silicone buffer pad. The deformation of the elastic arms can absorb 90% of the vibration energy, solving the problem of easy desoldering and breakage of traditional ring sleeves.

[0077] Reference Figure 5 The low-voltage insert 4 is made of H62 brass. Through the synergy of structural design and material selection, it can achieve both passive induction energy harvesting from the electric field and precise control of the partial discharge level.

[0078] The low-voltage insert 4 has a countersunk hole 41, the diameter of which matches the diameter of the positioning and mating section of the high-voltage insert 2, with a clearance of 0.03-0.05mm. The inner surface of the hole is polished to avoid electric field concentration due to surface roughness. The outer surface of the low-voltage insert 4 has two annular grooves. During casting, epoxy resin fills the grooves to form a mechanical interlocking structure, enhancing the bonding strength between the low-voltage insert 4 and the cable plug 1.

[0079] The upper end of the low-voltage insert 4 is provided with two elastic conductive pins made of phosphor bronze with an elastic deformation range of ≤0.5mm. The pin ends are soldered to the power module of the core circuit board 3. The elastic design can compensate for assembly tolerances and ensure reliable electrical connection.

[0080] Furthermore, the lower part of the low-pressure insert 4 is provided with three steps 42, and several radial guide grooves 43 are evenly distributed on the three steps 42.

[0081] The low-voltage insert 4 has an elastic energy storage cavity 44 at its bottom; a supercapacitor assembly 9 is disposed within the elastic energy storage cavity 44, and a spring 10 is fixedly disposed below the supercapacitor assembly 9. The supercapacitor assembly 9 is existing technology and can be purchased directly from the market; it is only used in this utility model and will not be described in detail here. The spring 10 is made of phosphor bronze and has both elastic support and conductive functions.

[0082] In this technical solution, a three-tiered stepped structure is used, with radial guide grooves machined on the end face of each tier, forming three independent power extraction units. Compared to a traditional single capacitor electrode, the power extraction area is increased by 60%, and the coupling efficiency with the distributed capacitance to ground is improved by 150%, ensuring stable power extraction even under low operating conditions with cable load ≤10%. A spring 10 and a supercapacitor assembly 9 are installed within the elastic energy storage cavity 44 of the low-voltage insert 4. The supercapacitor assembly 9 is connected to an elastic contact piece via the spring, and the surface of the contact piece is plated with nano-silver. This structure ensures close contact with the three-tiered stepped power extraction electrodes of the low-voltage insert and stores redundant energy through the supercapacitor, enabling continuous operation for forty minutes after a power outage and ensuring that critical temperature data is not lost. The free end of the elastic contact piece is directly attached to the conductive surface of the three-tiered stepped structure power extraction electrodes, forming a power extraction link between the power extraction unit, the elastic contact piece, the spring, and the supercapacitor assembly.

[0083] The supercapacitor module 9 uses an LTC3350 industrial-grade cylindrical supercapacitor energy storage module. Its positive electrode surface is bonded to the conductive surface of the three-stage stepped power extraction electrode of the low-voltage insert through an elastic contact piece, while the negative electrode surface abuts against the upper end of the phosphor bronze spring 10. The lower end of the spring 10 is fixed to the bottom of the elastic energy storage cavity 44, forming a complete power extraction and energy storage conductive link. The LTC3350 energy storage module's input voltage is adapted to the 3.3V output of the power module, and the output voltage is stable at 3.3V, perfectly matching the power supply requirements of the core circuit board and ensuring seamless connection between charging and backup power supply.

[0084] The principle of function implementation and partial discharge control is as follows:

[0085] Energy harvesting function: The annular inner surface of the low-voltage insert 4 serves as the low-voltage plate of the capacitor voltage divider circuit, forming a coupling capacitor C1 (capacitance value 50-100pF) with the positioning and matching section (high-voltage plate) of the high-voltage insert 2. This coupling capacitor forms a series voltage divider circuit with the inherent ground distributed capacitance C2 of the external cable system (parasitic capacitance between the cable conductor and the grounding system, typical value 100-200pF). When the cable is energized (10kV power frequency voltage), the alternating electric field induces an alternating voltage of 10-20V on the low-voltage insert 4 through the coupling effect of C1 and C2. After rectification, filtering and energy storage by the power module of the core circuit board 3, when the energy storage capacitor voltage reaches 3.0V, the temperature measurement module is triggered to start temperature measurement. At the same time, the wireless module is activated to send the temperature data up (data transmission time ≤100ms). After the transmission is completed, the power module enters a low-power energy storage state to realize periodic temperature measurement. The temperature measurement period can be set by the circuit parameters.

[0086] Partial discharge control: The low-voltage insert 4 uses a rigid conductive material to avoid uneven distribution of internal electric field due to material deformation during casting; at the same time, the ring structure design makes the electric field distribution uniform, without sharp corners or edges, and all corners are rounded to further suppress partial discharge; combined with the modified epoxy resin material of the cable plug 1 and the vacuum casting process, the partial discharge value is finally achieved to be <5pC under 10kV test conditions, which meets the strict requirements for partial discharge in GB / T 11022-2020 "Common Technical Requirements for High Voltage Switchgear and Controlgear Standards".

[0087] In this technical solution, there is no need to set up additional components such as energy harvesting coils and batteries. Passive energy harvesting is achieved only through the coupling capacitors of high voltage insert 2 and low voltage insert 4, combined with the inherent ground distribution capacitance of the cable system. This solves the problem of traditional temperature measurement devices relying on batteries and external energy harvesting coils. At the same time, through the triple synergy of material selection, structural optimization and process coordination, it is ensured that after the temperature measurement function is integrated, the partial discharge performance of the plug is no lower than that of existing ordinary plugs, achieving functional upgrade without degradation.

[0088] Furthermore, an ultra-thin electromagnetic shielding layer, consisting of 0.1mm thick tin-plated copper foil, is installed between the power module and the wireless module of the core circuit board 3. This shielding layer is electrically connected to the ground plane of the circuit board via vias, forming a closed shielding cavity. This confines the rectification noise of the power module and the interference from the charging and discharging of the energy storage capacitor within the shielding cavity, preventing coupling interference to the LoRa module's RF signal. Simultaneously, the power traces of the core circuit board 3 employ a star topology and a wide copper foil design, reducing power impedance and minimizing the impact of current fluctuations on the temperature measurement module. This ensures that the temperature measurement accuracy remains stable at ±0.3℃ even under strong electromagnetic interference, resolving the temperature drift problem caused by power interference in industrial scenarios.

[0089] Furthermore, the temperature sensing module incorporates a built-in temperature grading threshold logic: preset normal threshold (-40℃~70℃), warning threshold (70℃~90℃), and emergency threshold (>90℃). When the temperature is within the normal threshold, it measures the temperature every five minutes; upon reaching the warning threshold, the measurement cycle automatically shortens to one minute, and a warning flag is added to the LoRa module data frame; when the emergency threshold is reached, a rapid energy storage mode is triggered, the energy storage capacitor voltage threshold drops to 2.8V, the measurement cycle is compressed to ten seconds, and a three-times continuous retransmission mechanism is used when uploading data to ensure that abnormal temperature signals are transmitted without delay. This solves the problem of delayed response in traditional fixed-cycle temperature measurement and provides more time for handling cable fault warnings.

[0090] The working principle of this utility model of a temperature-measuring plug for a ring main unit cable connector is as follows: The three-stage stepped power-taking unit of the low-voltage insert 4 forms a series voltage-dividing circuit with the cable's distributed capacitance to ground. By increasing the power-taking area and optimizing the coupling structure, stable induced electrical energy can be generated even under low cable load. After rectification and voltage regulation by the power module, the energy is supplied to the circuit. The high-voltage insert 2 is directly attached to the internal electrical connection point of the cable, and the temperature is quickly conducted to the NTC thermistor of the core circuit board through a high thermal conductivity ceramic pillar. The LoRa module of the core circuit board 3 adopts a low-power intermittent working mode, encodes the temperature data, and wirelessly transmits it to the external gateway through the PCB integrated antenna. It has strong anti-electromagnetic interference and a transmission success rate of ≥99%. The supercapacitor assembly 9 is tightly connected to the power-taking unit through elastic contact pieces to store redundant electrical energy for backup. It can continuously supply power for forty minutes after a power outage, ensuring that critical temperature data is not lost.

[0091] This invention achieves zero-distance temperature measurement by directly attaching a high-voltage insert to the internal electrical connection point of the cable, combined with a high thermal conductivity ceramic pillar; solving the problems of inaccurate temperature measurement and delayed response of existing external sensors. The three-stage stepped power extraction structure of the low-voltage insert increases the power extraction area and improves coupling efficiency, enabling stable energy extraction even under low operating conditions with cable load ≤10%; combined with supercapacitor energy storage, it can provide continuous power for forty minutes after a power outage, avoiding the loss of critical temperature data. The double helical groove and barb design of the high-voltage insert and the annular groove structure of the low-voltage insert form a firm mechanical engagement with the plug shell, resisting vibration and displacement; the L-shaped insulating elastic arm and silicone buffer pad absorb vibration energy, preventing the circuit board from desoldering and breaking.

Claims

1. A temperature-sensing plug for a ring main unit cable connector, comprising: a cable plug and an internal temperature sensor insert; characterized in that: An internal temperature sensor is fixedly installed inside the cable plug. The two are integrated into an inseparable whole structure through an integrated casting process. The cable plug is made of insulating epoxy resin. The internal temperature sensor insert includes a high-voltage insert, a core circuit board, a low-voltage insert, and an equalizing ring; The high-voltage and low-voltage inserts are connected and fitted together, and a core circuit board is placed between the high-voltage and low-voltage inserts; the core circuit board integrates a temperature sensing module, a wireless module and a power module; The high-voltage insert includes a nest and a connecting support post; the connecting support post is fixedly installed on the nest; the nest and the connecting support post are provided with threaded holes; an equalizing ring is provided on the outside of the high-voltage insert; three micro conductive posts are evenly distributed on the inside of the equalizing ring, the micro conductive posts are connected to the high-voltage insert, the equalizing ring is made of semiconductor ceramic; the micro conductive posts are made of brass.

2. The temperature measuring plug for the cable joint of the ring main unit according to claim 1, characterized in that: The nest is shaped like a frustum. The outer side of the nest has a double helical groove with three sets of barbed anti-slip teeth inside. Multiple heat dissipation fins are fixedly installed on the outer side of the nest.

3. The temperature measuring plug for the cable joint of the ring main unit according to claim 1, characterized in that: The connecting support column is provided with stepped holes, and a high thermal conductivity ceramic column is installed in the stepped holes. One end of the high thermal conductivity ceramic column is directly attached to the cable connecting screw, and the other end is connected to the temperature sensing module of the core circuit board through an elastic conductive sheet.

4. The temperature measuring plug for the cable joint of the ring main unit according to claim 2, characterized in that: The core circuit board is a circular PCB board. The core circuit board is fixed to the high voltage insert by two epoxy resin insulating pads. The insulating pads are connected by a slot. Silicone buffer pads are set on the top and bottom of the core circuit board. The power module of the core circuit board is soldered to the conductive pin of the low voltage insert by two silver-plated copper wires. Multiple L-shaped insulating elastic arms are provided on the upper silicone buffer pad, and one end of the L-shaped insulating elastic arm is engaged with the heat dissipation fins of the high voltage insert.

5. The temperature measuring plug for the cable joint of the ring main unit according to claim 3, characterized in that: The lower part of the low-pressure insert is provided with three steps, and several radial guide grooves are evenly distributed on the three steps.

6. The temperature measuring plug for the cable joint of the ring main unit according to claim 5, characterized in that: The bottom of the low-voltage insert is provided with an elastic energy storage cavity; a supercapacitor assembly is provided inside the elastic energy storage cavity, and a spring is fixedly installed below the supercapacitor assembly.

7. The temperature measuring plug for the cable joint of the ring main unit according to claim 1, characterized in that: The cable plug is made of bisphenol A type epoxy resin with added nano-alumina, which is cast.

8. The temperature measuring plug for the cable joint of the ring main unit according to claim 1, characterized in that: The low-voltage insert is made of brass; the upper end of the low-voltage insert has two flexible conductive pins.

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