A zero sequence current sensor for pole-mounted switch

Abstract

The utility model relates to the technical field of power supply, concretely relates to a zero sequence current sensor for pole-mounted switch. Include: electrically conductive pole, for three, respectively string in three -phase incoming line and three -phase outgoing line between, current transformer, with the electrically conductive pole one to one correspondence, primary side respectively with the electrically conductive pole and coupling, resistance group, for three groups, corresponding series connection between two lead of current transformer secondary side, and it is parallel between the resistance in the same group, output, respectively with three resistance groups parallel, wherein, electrically conductive pole, current transformer and resistance group set up in solid -sealed pole, in this application, electrically conductive pole, current transformer and resistance group are set up in solid -sealed pole together, realized compact structure and function height unification. Three electrically conductive poles are respectively string in three -phase incoming line and three -phase outgoing line between, directly bear main circuit current, provide accurate reliable signal source for current transformer.

Description

Technical Field

[0001] This utility model relates to the field of power supply technology, specifically to a zero-sequence current sensor for a pole-mounted switch. Background Technology

[0002] Currently, the zero-sequence current sensor inside the solid-sealed pole can detect the operating status of the three-phase power grid. If at least one of the three-phase lines fails, the voltage at its output terminal will not be 0, and staff can then carry out maintenance and inspection.

[0003] Existing zero-sequence current sensors contain current transformers, but the secondary side of the current transformer uses a single load resistor. The current on the secondary side is concentrated on the load resistor, which results in a large amount of heat generation and concentrated heat generation, affecting the service life. Utility Model Content

[0004] In view of this, the present invention provides a zero-sequence current sensor for pole-mounted switches to solve the problem of large and concentrated heat generation from the secondary load resistor.

[0005] This utility model provides a zero-sequence current sensor for pole-mounted switches, used to detect the state of a three-phase system, including: There are three conductive rods, which are connected in series between the three-phase incoming lines and the three-phase outgoing lines respectively; A current transformer, corresponding one-to-one with the conductive rod, has its primary side coupled to the conductive rod and the conductor rod respectively; There are three groups of resistors, which are connected in series between the two leads on the secondary side of the current transformer, and the resistors in the same group are connected in parallel. The output is connected in parallel with three sets of resistors. The conductive rod, current transformer, and resistor group are housed within the solid-sealed pole.

[0006] In this application, the conductive rods, current transformers, and resistor groups are all housed within a solid-sealed pole, achieving a compact structure and highly unified functionality. The three conductive rods are connected in series between the three-phase incoming and outgoing lines, directly carrying the main circuit current and providing an accurate and reliable signal source for the current transformers. The current transformers are connected to the conductive rods in a one-to-one correspondence and coupling manner, enabling non-contact, precise measurement of the three-phase current. This ensures electrical isolation between the high-voltage side and the low-voltage measurement circuit, improving equipment safety and anti-interference capabilities. Three resistor groups are configured, connected in series between the secondary leads of the current transformers. Resistors within the same group are connected in parallel, converting the current signal to a voltage signal while dispersing the secondary current through the parallel structure, thus reducing the power consumption of individual resistors. The heat generated by a single resistor in this application is less than that in existing technologies, reducing heat concentration effects and improving the thermal stability and long-term operational reliability of the entire sampling circuit. The output terminal is connected in parallel with the three resistor groups, directly outputting a voltage signal characterizing the zero-sequence current, which facilitates subsequent acquisition and processing by protection devices.

[0007] In one optional embodiment, an arc-extinguishing device is provided between the three-phase incoming lines and the conductive rod.

[0008] In this application, arc-extinguishing devices are installed between the three-phase incoming lines and the conductive rods. This improves the safety of equipment operation and the reliability of long-term operation. When a pole-mounted switch interrupts current, especially when interrupting fault current or load current, a high-temperature, high-pressure arc is generated at the moment the moving and stationary contacts separate. The arc-extinguishing device can suppress and extinguish this arc, preventing it from continuing to burn. This not only protects the conductive rod and contact surfaces from arc erosion, maintaining their good conductivity and mechanical strength, and extending the service life of key components, but also avoids phase-to-phase short circuits or ground faults that may be caused by the arc, preventing the accident from escalating. For solid-sealed poles integrating precision sensing elements, the arc-extinguishing device effectively isolates the huge thermal shock and electromagnetic interference generated by the arc, providing a stable working environment for the internal current transformers and resistors, ensuring the accuracy of measurement signals and the overall functional stability of the current transformers, enabling them to adapt to the frequent operations required by distribution network automation.

[0009] In one alternative embodiment, the conductive rod is suspended inside the current transformer.

[0010] In this application, the conductive rod, as part of the high-voltage main conductive circuit, undergoes thermal expansion due to heat accumulation after current flow and also bears enormous electrodynamic forces under short-circuit conditions. The suspended sleeve design eliminates the rigid mechanical connection between the conductive rod and the current transformer core, thus preventing the transfer of mechanical stress or deformation to the current transformer and preventing changes in the magnetic properties of the core due to external pressure, ensuring the linearity of current sensing and long-term measurement accuracy. Simultaneously, the suspended structure creates a uniform air insulation gap and epoxy resin insulation layer between the high-voltage conductive rod and the low-voltage side current transformer windings, effectively improving the electric field distribution, eliminating electric field concentration phenomena that may be caused by sharp burrs or contact points, increasing the partial discharge initiation voltage and overall insulation withstand capability, and enhancing electrical safety performance in harsh environments.

[0011] In one optional embodiment, the solid-sealed electrode further includes: The circuit board has resistors arranged in an array on it.

[0012] In this application, the solid-sealed terminal block also includes a circuit board, on which the resistors are arrayed, enabling modular integration and standardized manufacturing of the resistor devices. The circuit board provides precise and robust mechanical mounting and electrical connection paths for all resistors. Copper foil traces ensure the consistency of parallel branch impedances, reducing parameter dispersion caused by randomness in the connection process and guaranteeing highly consistent gain and phase characteristics for the three-phase signal conditioning channels. The array layout is compact, with high space utilization, facilitating uniform heat distribution and effective conduction and dissipation to the external epoxy resin.

[0013] In one optional embodiment, the solid-sealed electrode further includes: Mounting plate, the output terminal is mounted on the mounting plate.

[0014] In this application, the mounting plate provides a reliable external electrical interface and enhances overall sealing. As a rigid support platform, the mounting plate provides a solid mounting foundation for output terminals such as aviation sockets, effectively resisting the mechanical stress and torque generated during connector insertion and removal, preventing poor contact or signal interruption due to interface loosening, and ensuring long-term reliability of external connections.

[0015] In one alternative implementation, each group of resistors has the same number of resistors.

[0016] In one optional implementation, all resistors in the resistor group have the same resistance value.

[0017] In this application, each resistor group has the same number of resistors, and the resistance values ​​within each resistor group are identical, ensuring the symmetry of the three-phase measurement channels and the accuracy of zero-sequence detection. The zero-sequence current output is a representation of the vector sum of the three-phase current signals; any inconsistency in the transfer function of any phase measurement channel will directly introduce measurement errors. The three resistor groups contain the same number of resistors with the same resistance values, ensuring that the impedance network from the secondary side of each phase current transformer to the common output node is completely symmetrical in topology. Under normal three-phase balance, the theoretical output is zero, effectively suppressing common-mode interference; when a ground fault generates zero-sequence current, it can accurately reproduce the magnitude and phase of the fault signal, improving the measurement accuracy and reliability of the sensor.

[0018] In one optional implementation, there are three solid-sealed poles, which are connected to the three-phase lines respectively.

[0019] In this application, three independent solid-sealed terminals are used to correspond to the three-phase lines, ensuring complete physical isolation of the high-voltage conductive circuit, sensing unit, and sampling circuit of each phase. This ensures sufficient distance between the high-voltage phases, and combined with the excellent insulation properties of the solid-sealed epoxy resin, prevents phase-to-phase short-circuit faults, meeting the stringent electrical insulation requirements of high-voltage equipment. The modular design facilitates standardized production, testing, and maintenance of components, with each phase terminal treated as an independent unit. If a phase fails during operation, it can be replaced specifically without scrapping the entire three-phase sensor, reducing the total lifecycle cost and maintenance complexity of the equipment. Simultaneously, the phase-separated design also facilitates heat dissipation, preventing the three-phase heat sources from concentrating in a single cavity.

[0020] In one alternative embodiment, the inner side of the solidified electrode is potted with epoxy resin.

[0021] In this application, liquid epoxy resin is poured into the electrode cavity under vacuum, filling every tiny gap. After curing, it forms a solid module that completely and tightly binds the conductive rod, current transformer, circuit board, resistor group, and internal wiring together. This solid module has high mechanical strength, effectively resisting the effects of vibration, impact, and stress, preventing internal component displacement or connection point breakage. Epoxy resin is an excellent insulating material, greatly enhancing the insulation strength between components at different potentials and eliminating the risk of surface creepage.

[0022] In one alternative embodiment, the outer layer of the epoxy resin is coated with silicone rubber.

[0023] In this application, the epoxy resin is coated with silicone rubber. This double-layer protective structure combines the rigid support of epoxy resin with the flexibility and weather resistance of silicone rubber, forming a perfect outdoor protection system. Silicone rubber material possesses extremely excellent resistance to UV aging, high and low temperature cycling, and hydrophobic properties. As the outermost protective layer, it directly faces atmospheric factors such as sunlight, rain, snow, and ozone, effectively delaying environmental aging, preventing material cracking or powdering, and protecting the internal epoxy resin core from external climatic erosion. Its hydrophobicity makes it difficult for water droplets to form a continuous conductive water film on its surface, ensuring high insulation resistance of the product's outer surface in humid environments. The elasticity of the silicone rubber layer also buffers minor external impacts and absorbs internal stress caused by thermal expansion and contraction between different materials due to temperature changes, preventing the protective layer from cracking and thus maintaining the integrity of the overall seal for a long time. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the circuit connection of an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of an embodiment of the present utility model.

[0026] Explanation of reference numerals in the attached figures: 1. Conductive rod; 2. Current transformer; 3. Resistor group; 4. Output terminal; 5. Arc extinguishing device; 6. Circuit board; 7. Mounting plate; 8. Phase A current transformer; 9. Phase B current transformer; 10. Phase C current transformer. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0028] The power distribution network is a crucial foundation of the energy internet and a key link affecting the level of power supply services. With the large-scale integration of electric vehicles, distributed energy sources, microgrids, energy storage devices, and other facilities, as well as the development of the electricity market and the emergence of various electricity demands, higher requirements are placed on the security, economy, and adaptability of the power distribution network. It is imperative to build a first-class modern power distribution network that is highly reliable, interactive, and cost-effective. The intelligentization of the power distribution network relies on intelligent terminals. Based on the quality control platform for power distribution terminal equipment, a full life-cycle quality control system for power distribution automation equipment should be established. This system should strengthen three-level quality control for power distribution terminals and circuit breakers: network entry inspection, full inspection upon arrival, and operational evaluation. It should achieve online integration of inspection reports, operational data, and defect records, and conduct comparative analysis by batch, manufacturer, model, region, and cycle. Through quality evaluation, it should achieve full-process tracking of product quality, simultaneous accountability, and timely handling.

[0029] Currently, the current sensors used in solid-sealed poles have internal current transformers and secondary output currents of 5A or 1A. A high-power load resistor connected in series with the secondary side is then installed on the circuit breaker housing, which generates a lot of heat, is unreliable, wastes electrical energy, and affects product lifespan.

[0030] This application utilizes low-temperature drift surface-mount resistors, multiple of which are connected in parallel to shunt the current, resulting in a secondary output current of 0.1A. This significantly reduces the load resistor power and disperses heat generation, allowing for encapsulation in epoxy resin within the solid-state terminal. Furthermore, sufficient power margin is maintained. It is an ideal product to replace the original solid-state terminal zero-sequence current sensor on circuit breakers.

[0031] The following is combined Figures 1 to 2 The following describes embodiments of the present invention.

[0032] According to an embodiment of this utility model, a zero-sequence current sensor for a pole-mounted switch is provided for detecting the state of a three-phase system, such as... Figure 1 As shown, it includes: There are three conductive rods 1, which are connected in series between the three-phase incoming line and the three-phase outgoing line respectively. The three-phase incoming line can be phase A incoming line, phase B incoming line and phase C incoming line, and the three-phase outgoing line can be phase A outgoing line, phase B outgoing line and phase C outgoing line. The three conductive rods 1 can be connected between phase A incoming line and phase A outgoing line, phase B incoming line and phase B outgoing line, and phase C incoming line and phase C outgoing line respectively.

[0033] Current transformer 2 corresponds one-to-one with each of the conductive rods 1, with its primary side coupled to each conductive rod 1. The current transformer 2 can be a three-phase current transformer 2. The primary side handles a large current, and the secondary side handles a small current. It may include an A-phase current transformer 8, a B-phase current transformer 9, and a C-phase current transformer 10, each corresponding to and coupled to one of the conductive rods 1.

[0034] It should be noted that a standard three-phase system typically has 3 live wires + 1 neutral wire + 1 ground wire, for a total of 5 conductors. Three current transformers (2) are connected to phases A, B, and C respectively, each independently measuring the current in its own phase. These three vector current signals (Ia, Ib, Ic) are sent to a common parallel summation point. Under normal conditions, the three phases are balanced, Ia + Ib + Ic ≈ 0, and the output is zero. When a ground fault occurs, the three-phase currents become unbalanced, Ia + Ib + Ic ≠ 0, and the portion that is not equal to zero is the zero-sequence current, which the sensor converts into a voltage signal output.

[0035] Resistor group 3 consists of three groups, connected in series between the leads at the two interfaces on the secondary side of the current transformer 2, with resistors within the same group connected in parallel. The resistors in resistor group 3 can be surface-mount resistors. As shown in the figure, they can include Ra1, Ra2, Ra3, ..., Ran, Rb1, Rb2, Rb3, ..., Rbn, Rc1, Rc2, Rc3, ..., Rcn. The resistance value of the parallel resistors in each resistor group 3 can be equal to the resistance value of a single resistor in the prior art, so that the load voltage output by resistor group 3 is the same as the load voltage of a single resistor in the prior art.

[0036] Output terminal 4 is connected in parallel with three sets of resistors 3; output terminal 4 can be an aviation socket. For example... Figure 1 As shown, output terminal 4's "1" and "2" can be two interfaces.

[0037] The conductive rod 1, the current transformer 2, and the resistor group 3 are installed inside the solid-sealed pole.

[0038] In this application, the conductive rod 1, current transformer 2, and resistor group 3 are all housed within a solid-sealed pole, achieving a compact structure and highly unified function. The three conductive rods 1 are connected in series between the three-phase incoming and three-phase outgoing lines, directly carrying the main circuit current and providing an accurate and reliable signal source for the current transformer 2. The current transformer 2 corresponds one-to-one with the conductive rod 1 and is connected via coupling, enabling non-contact, accurate measurement of the three-phase current. This ensures electrical isolation between the high-voltage side and the low-voltage measurement circuit, improving equipment safety and anti-interference capabilities. The resistor group 3 is configured in three groups, corresponding to the secondary leads of the current transformer 2, with resistors within the same group connected in parallel. This converts the current signal into a voltage signal while simultaneously dispersing the secondary current through the parallel structure, thereby reducing the power consumption of individual resistors. The heat generated by a single resistor in this application is less than that of a single resistor in the prior art, reducing heat concentration effects and improving the thermal stability and long-term operational reliability of the entire sampling circuit. Output terminal 4 is connected in parallel with three sets of resistors 3 to directly output a voltage signal characterizing the zero-sequence current, which can be easily collected and processed by subsequent protection devices.

[0039] In one optional embodiment, an arc-extinguishing device 5 is provided between each of the three-phase incoming lines and the conductive rod 1. The arc-extinguishing device 5 can be an arc-extinguishing chamber, as shown in the figure, which can be an A-phase arc-extinguishing chamber, a B-phase arc-extinguishing chamber, and a C-phase arc-extinguishing chamber, respectively.

[0040] In this application, an arc-extinguishing device 5 is provided between the three-phase incoming lines and the conductive rod 1. This improves the safety of equipment operation and the reliability of long-term operation. When the pole-mounted switch interrupts current, especially when interrupting fault current or load current, a high-temperature and high-pressure arc is generated at the moment the moving and stationary contacts separate. The arc-extinguishing device 5 can suppress and extinguish this arc, preventing it from continuing to burn. This not only protects the conductive rod 1 and the contact surface from arc erosion, maintaining its good conductivity and mechanical strength, and extending the service life of key components, but also avoids phase-to-phase short circuits or ground faults that may be caused by the arc, preventing the accident from escalating. For solid-sealed poles integrating precision sensing elements, the arc-extinguishing device 5 effectively isolates the huge thermal shock and electromagnetic interference generated by the arc, providing a stable working environment for the internal current transformer 2 and resistor, ensuring the accuracy of measurement signals and the overall functional stability of the current transformer 2, enabling it to adapt to the frequent operations required by distribution network automation.

[0041] In one alternative embodiment, the conductive rod 1 is suspended and sleeved inside the current transformer 2.

[0042] In this application, the conductive rod 1, as part of the high-voltage main conductive circuit, undergoes thermal expansion due to heat accumulation after current flow and also bears enormous electrodynamic forces under short-circuit conditions. The suspended sleeve design eliminates the rigid mechanical connection between the conductive rod 1 and the core of the current transformer 2, thus preventing the transfer of mechanical stress or deformation to the current transformer 2. This prevents changes in the magnetic properties of the core due to external pressure, ensuring the linearity of current sensing and long-term measurement accuracy. Simultaneously, the suspended structure creates a uniform air insulation gap and epoxy resin insulation layer between the high-voltage conductive rod 1 and the winding of the low-voltage current transformer 2, effectively improving the electric field distribution, eliminating electric field concentration phenomena that may be caused by sharp burrs or contact points, increasing the partial discharge initiation voltage and overall insulation withstand capability, and enhancing electrical safety performance in harsh environments.

[0043] In one alternative implementation, such as Figure 2 As shown, the solid-sealed electrode also includes: The resistors are arranged in an array on the circuit board 6.

[0044] In this application, the solid-sealed terminal block also includes a circuit board 6, on which the resistors are arrayed, enabling modular integration and standardized manufacturing of the resistor devices. The circuit board 6 provides precise and robust mechanical mounting and electrical connection paths for all resistors. Copper foil traces ensure the consistency of parallel branch impedances, reducing parameter dispersion caused by randomness in the connection process and guaranteeing highly consistent gain and phase characteristics for the three-phase signal conditioning channels. The array layout is compact, with high space utilization, facilitating uniform heat distribution and effective conduction and dissipation to the external epoxy resin.

[0045] In one optional embodiment, the solid-sealed electrode further includes: Mounting plate 7, the output terminal 4 is mounted on mounting plate 7.

[0046] In this application, mounting plate 7 provides a reliable external electrical interface and enhances overall sealing. As a rigid support platform, mounting plate 7 provides a solid mounting foundation for output terminals 4 such as aviation sockets, effectively resisting the mechanical stress and torque generated when plugging and unplugging connectors, preventing poor contact or signal interruption due to interface loosening, and ensuring long-term reliability of external connections.

[0047] In one alternative implementation, each group of resistors 3 has the same number of resistors.

[0048] In one optional implementation, all resistors in resistor group 3 have the same resistance value.

[0049] In this application, each resistor group 3 contains the same number of resistors, and the resistance values ​​within each resistor group 3 are identical, ensuring the symmetry of the three-phase measurement channels and the accuracy of zero-sequence detection. The zero-sequence current output is a representation of the vector sum of the three-phase current signals; any inconsistency in the transfer function of any phase measurement channel will directly introduce measurement errors. The three resistor groups 3 contain the same number of resistors with the same resistance values, ensuring that the impedance network from the secondary side of each phase current transformer 2 to the common output node is completely symmetrical in topology. Under normal three-phase balance, the theoretical output is zero, effectively suppressing common-mode interference; when a ground fault generates zero-sequence current, it can accurately reproduce the magnitude and phase of the fault signal, improving the measurement accuracy and reliability of the sensor.

[0050] In one optional embodiment, three solid-sealed terminals are connected to the three-phase lines respectively. Each solid-sealed terminal contains a conductive rod 1, a current transformer 2, a resistor group 3, a circuit board 6, and a mounting plate 7, forming three independent solid-sealed terminals, respectively connected between the A-phase input and output lines, the B-phase input and output lines, and the C-phase input and output lines. The output terminal 4 can be connected in parallel with the secondary side resistors within each of the three solid-sealed terminals to obtain an output voltage.

[0051] In this application, three independent solid-sealed terminals are used to correspond to the three-phase lines, ensuring complete physical isolation of the high-voltage conductive circuit, sensing unit, and sampling circuit of each phase. This ensures sufficient distance between the high-voltage phases, and combined with the excellent insulation properties of the solid-sealed epoxy resin, prevents phase-to-phase short-circuit faults, meeting the stringent electrical insulation requirements of high-voltage equipment. The modular design facilitates standardized production, testing, and maintenance of components, with each phase terminal treated as an independent unit. If a phase fails during operation, it can be replaced specifically without scrapping the entire three-phase sensor, reducing the total lifecycle cost and maintenance complexity of the equipment. Simultaneously, the phase-separated design also facilitates heat dissipation, preventing the three-phase heat sources from concentrating in a single cavity.

[0052] In one alternative embodiment, the inner side of the solidified electrode is potted with epoxy resin. The operating environment of the device inside the solidified electrode can be greater than the melting point of the epoxy resin, for example, greater than 180°C, so that it can still function normally during potting.

[0053] In this application, liquid epoxy resin is poured into the electrode cavity under vacuum, filling every tiny gap. After curing, it forms a solid module that completely and tightly binds the conductive rod 1, current transformer 2, circuit board 6, resistor group 3, and internal wiring together. This solid module has high mechanical strength, effectively resisting the effects of vibration, impact, and stress, preventing internal component displacement or connection point breakage. Epoxy resin is an excellent insulating material, greatly enhancing the insulation strength between components at different potentials and eliminating the risk of surface creepage.

[0054] In one alternative embodiment, the outer layer of the epoxy resin is coated with silicone rubber.

[0055] In this application, the epoxy resin is coated with silicone rubber. This double-layer protective structure combines the rigid support of epoxy resin with the flexibility and weather resistance of silicone rubber, forming a perfect outdoor protection system. Silicone rubber material possesses extremely excellent resistance to UV aging, high and low temperature cycling, and hydrophobic properties. As the outermost protective layer, it directly faces atmospheric factors such as sunlight, rain, snow, and ozone, effectively delaying environmental aging, preventing material cracking or powdering, and protecting the internal epoxy resin core from external climatic erosion. Its hydrophobicity makes it difficult for water droplets to form a continuous conductive water film on its surface, ensuring high insulation resistance of the product's outer surface in humid environments. The elasticity of the silicone rubber layer also buffers minor external impacts and absorbs internal stress caused by thermal expansion and contraction between different materials due to temperature changes, preventing the protective layer from cracking and thus maintaining the integrity of the overall seal for a long time.

[0056] It should be noted that using resistors to convert signals inevitably generates heat (power equals the square of the current multiplied by the resistance).

[0057] If a single large resistor is used to complete the conversion (e.g., a 50-ohm / 5-watt high-power resistor), the following problems will occur: Large size: High-power resistors are bulky and cannot be placed in compact solid-sealed terminals.

[0058] Heat concentration: All the heat is concentrated at one point, forming a localized high temperature. This can cause thermal stress on the surrounding epoxy resin potting material, which may lead to cracking, aging, and damage to insulation and sealing in the long run.

[0059] Reliability risk: If a single component fails, the entire sensor will fail.

[0060] To address this, this application employs a scheme of multiple low-power surface-mount resistors connected in parallel. For example, to convert a 0.1 amp current to a 5 volt voltage, the required resistance is equal to the voltage divided by the current, which equals 50 ohms.

[0061] Use 10 500-ohm surface mount resistors in parallel (total resistance 500 ohms divided by 10 equals 50 ohms).

[0062] The current is divided into 10 paths, with each resistor carrying only 0.01 amperes of current.

[0063] The power consumption of each resistor (equal to the square of the current multiplied by the resistance) is 0.05 watts.

[0064] The technical effect is as follows: Heat distribution: Each resistor generates only 0.05 watts of heat, resulting in uniform heat distribution, avoiding localized overheating, and ensuring the long-term stability of the potting compound.

[0065] Compact size: Surface mount resistors are very small in size. Even when multiple resistors are connected in parallel, their total footprint is still much smaller than that of a single high-power resistor, making them suitable for integration onto circuit boards and encapsulation.

[0066] Improved reliability: Multiple resistors connected in parallel create redundancy. Even if individual resistors fail, the total resistance does not change significantly, and the sensor can still function normally, although the accuracy will decrease slightly. This achieves "degraded operation" and greatly improves system reliability.

[0067] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A zero-sequence current sensor for a pole-mounted switch, used to detect the state of a three-phase system, characterized in that, include: Three conductive rods (1) are connected in series between the three-phase incoming line and the three-phase outgoing line respectively; The current transformer (2) corresponds one-to-one with the conductive rod (1), and its primary side is coupled to the conductive rod (1) respectively; The resistor group (3) consists of three groups, which are connected in series between the two leads on the secondary side of the current transformer (2), and the resistors in the same group are connected in parallel. The output terminal (4) is connected in parallel with three sets of resistors (3); The conductive rod (1), current transformer (2) and resistor group (3) are installed inside the solid-sealed pole.

2. The zero-sequence current sensor for a pole-mounted switch according to claim 1, characterized in that, An arc-extinguishing device (5) is provided between the three-phase incoming line and the conductive rod (1).

3. The zero-sequence current sensor for a pole-mounted switch according to claim 1, characterized in that, The conductive rod (1) is suspended inside the current transformer (2).

4. The zero-sequence current sensor for a pole-mounted switch according to claim 1, characterized in that, The solid-sealed electrode also includes: The circuit board (6) has resistors arranged in an array on it.

5. The zero-sequence current sensor for a pole-mounted switch according to claim 4, characterized in that, The solid-sealed electrode also includes: Mounting plate (7), the output terminal (4) is mounted on the mounting plate (7).

6. The zero-sequence current sensor for a pole-mounted switch according to claim 1, characterized in that, Each group of resistors (3) has the same number of resistors.

7. The zero-sequence current sensor for a pole-mounted switch according to claim 6, characterized in that, The resistance values ​​in the resistor group (3) are all the same.

8. The zero-sequence current sensor for a pole-mounted switch according to claim 1, characterized in that, The three solid-sealed poles are connected to the three-phase lines respectively.

9. The zero-sequence current sensor for a pole-mounted switch according to claim 1, characterized in that, The inner side of the solidified electrode is potted with epoxy resin.

10. The zero-sequence current sensor for a pole-mounted switch according to claim 9, characterized in that, The epoxy resin is coated with silicone rubber.

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