An open-close type current transformer, state recognition device and method

Abstract

This invention provides a closable current transformer, a state identification device, and a method. The closable current transformer includes a fixed housing, a movable top cover, a locking assembly, a magnet, at least one Hall sensor, and a main control unit. The magnet is mounted on the movable top cover or a component linked to it. The Hall sensor is fixed to the fixed housing and corresponds to the position of the magnet. The main control unit has at least two preset thresholds to form at least three signal intervals. Based on the signal interval into which the amplitude of the detection signal output by the Hall sensor falls, the current state is determined from a multi-level state set including closed state, half-open state, and false-open state, and a graded signal is output. This invention achieves multi-level reliable identification of the mechanical closed state of the closable current transformer by constructing a dedicated position sensing channel independent of the primary side working magnetic field and combining it with multi-threshold interval division. It has the advantages of being non-contact, anti-interference, and having precise discrimination.

Description

Technical Field

[0001] This invention relates to the field of current transformer condition detection technology, and in particular to an openable current transformer, a condition identification device and method. Background Technology

[0002] Switchable current transformers are widely used in power distribution monitoring, energy management, and equipment maintenance because they can be installed or upgraded without power interruption. Compared to integral current transformers, switchable products have the advantages of strong field adaptability and convenient construction, but this also introduces mechanical structures such as movable top covers, locking assemblies, clamping surfaces, and core connections. In actual use, if the locking assemblies are not locked, the movable top cover is not pressed in place, or it becomes loose due to long-term vibration, the fixed core and movable core of the transformer will be in a state of incomplete connection, partial opening, or poor contact, which will disrupt the continuity of the magnetic circuit, affect the measurement accuracy, and in severe cases may even lead to abnormal operation risks.

[0003] The primary method for determining whether a current transformer is properly closed relies on indirect inference based on the presence or absence of an output signal on the secondary side. However, when there is no current in the primary circuit, the absence of a signal output on the secondary side cannot distinguish between a structural abnormality and normal no-load operation; similarly, when there is current in the primary side, the presence of a signal output on the secondary side does not prove that the core is in an ideal closed state. This method, which relies on electrical output, cannot form a stable and reliable determination of the structural state.

[0004] Chinese utility model patent CN204651156U discloses a current transformer with a saturation self-alarm function. It uses a Hall element at the junction of two U-shaped iron cores to monitor the internal magnetic flux in real time and issue an alarm signal when the core saturates. However, this solution detects the working magnetic flux of the main magnetic circuit of the iron core, and its signal depends on the primary side working current. When there is no current on the primary side, even if the iron core structure is intact, the working magnetic flux is zero. The Hall element cannot distinguish between normal and abnormal structures, making it unsuitable for detecting the mechanical closed state of open-loop current transformers. Chinese invention patent CN111505363A discloses a closed-loop current transformer. It uses a Hall element at the gap in the magnetic ring and drives a dual-compensation coil with positive and negative power supplies to generate a reverse magnetic field to cancel the primary side magnetic field, thereby achieving precise current measurement. This solution is a continuous closed-loop analog measurement system, aiming to make the output strictly proportional to the input current, and it lacks discrete hierarchical discrimination logic for the mechanical structural state of the transformer.

[0005] In summary, existing applications of Hall effect sensors in current transformers, whether for monitoring the working magnetic flux of the iron core or for constructing closed-loop measurement circuits, cannot solve the problem of identifying the mechanical closed state of open-loop current transformers. Summary of the Invention

[0006] The purpose of this invention is to provide an openable current transformer, a state identification device and method to solve the problem that existing openable current transformers are difficult to reliably identify the closed state of the movable cover in multiple stages.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A switchable current transformer includes a fixed iron core and a movable iron core, and further includes: Fixed housing; The movable top cover is movably connected to the fixed housing and can move between a closed position and an open position. The fixed iron core is disposed inside the fixed housing, and the movable iron core is disposed inside the movable top cover. A locking assembly is disposed between the fixed housing and the movable upper cover, for locking the movable upper cover in the closed position; A magnet is disposed on the movable upper cover or a component that is linked to the movable upper cover; At least one Hall sensor is fixed on the fixed housing, corresponding to the position of the magnet, and is used to output a detection signal related to the distance between the magnet and the Hall sensor; The main control unit is electrically connected to the Hall sensor. The main control unit has at least two preset thresholds to form at least three signal intervals. The main control unit is configured to determine the current state in a multi-level state set including closed state, half-open state and false open state based on the signal interval into which the amplitude of the detected signal falls, and output a graded signal corresponding to the current state. When the movable top cover is in the closed position and the locking assembly is in the locked position, the end faces of the fixed iron core and the movable iron core are in contact with each other.

[0008] Furthermore, the at least one Hall sensor includes a linear Hall sensor, and the detection signal is an analog signal; the main control unit includes an analog-to-digital converter module for converting the analog signal into a digital signal.

[0009] Furthermore, the main control unit is configured to determine the current state as the half-open state when the amplitude of the detection signal corresponding to the digital signal falls into the middle interval of the at least three signal intervals and the duration exceeds a preset time threshold.

[0010] Furthermore, the at least one Hall sensor includes a first Hall sensor and a second Hall sensor arranged at intervals along the direction of movement of the magnet; the main control unit is electrically connected to the first Hall sensor and the second Hall sensor respectively, and is configured to determine the offset direction or degree of the movable cover during the closing or locking process based on the difference between the first detection signal output by the first Hall sensor and the second detection signal output by the second Hall sensor.

[0011] Furthermore, it also includes a temperature acquisition unit, which is electrically connected to the main control unit; the main control unit is configured to perform temperature compensation on the detection signal based on the ambient temperature value acquired by the temperature acquisition unit before determining the current state.

[0012] Furthermore, the main control unit stores a temperature compensation calibration table. The main control unit queries the temperature compensation calibration table based on the ambient temperature value to perform zero-point correction or sensitivity correction on the detection signal.

[0013] Furthermore, the graded signals include a first-level mechanical abnormality signal, a second-level suspected half-open signal, and a third-level highly reliable false opening signal; the first-level mechanical abnormality signal corresponds to the locking assembly not being locked, the second-level suspected half-open signal corresponds to the movable upper cover being in a half-open or loosely connected state, and the third-level highly reliable false opening signal corresponds to the movable upper cover being obviously open or offset.

[0014] Furthermore, the main control unit is further configured to determine that an equivalent air gap exists between the movable upper cover and the fixed housing when the first detection signal and the second detection signal exhibit any of the following characteristics, and to define the current state as the half-open state: The amplitude ratio of the first detection signal and the second detection signal when the movable cover is in the closed position deviates from a preset closing amplitude ratio, and the deviation remains consistent before and after the locking assembly is locked. The amplitude of the first detection signal or the second detection signal fluctuates back and forth between the signal interval corresponding to the closed position and the intermediate interval, and the number of fluctuations exceeds a preset threshold. The difference between the first detection signal and the second detection signal repeatedly crosses a preset fluctuation threshold within a preset time period.

[0015] The present invention also provides a switching current transformer status identification device, comprising: Fixed housing; The movable top cover is movably connected to the fixed housing and is used to move between a closed position and an open position; A locking assembly is disposed between the fixed housing and the movable upper cover, for locking the movable upper cover in the closed position; A magnet is disposed on the movable upper cover or a component that is linked to the movable upper cover; At least one Hall sensor is fixed on the fixed housing, corresponding to the position of the magnet, and is used to output a detection signal related to the distance between the magnet and the Hall sensor; The main control unit is electrically connected to the Hall sensor. The main control unit has at least two preset thresholds to form at least three signal intervals. The main control unit is configured to determine the current state from a multi-level state set including closed state, half-open state and false open state based on the signal interval into which the amplitude of the detected signal falls, and output a graded signal corresponding to the current state.

[0016] The present invention also provides a method for identifying the state of an open-close current transformer, comprising: Acquire a detection signal output by at least one Hall sensor fixed to a fixed housing, the detection signal reflecting the relative distance between the magnet disposed on the movable top cover and the Hall sensor; The amplitude of the detected signal is compared with at least two preset thresholds to determine the signal interval into which the amplitude falls, and the at least two thresholds form at least three signal intervals; When the amplitude falls within the first signal range, it is determined to be in a closed state; when the amplitude falls within the second signal range, it is determined to be in a half-open state; when the amplitude falls within the third signal range, it is determined to be in an erroneous open state. Output a hierarchical signal corresponding to the determined state.

[0017] Compared with existing technologies, this invention constructs a dedicated position sensing channel independent of the primary side working magnetic field by setting a magnet in the movable top cover and a Hall sensor in the fixed housing. The Hall sensor detects the magnetic field generated by the magnet, the intensity of which changes only with the opening and closing distance of the movable top cover. This decouples the sensor from the primary side working current, avoiding the defects of being unable to determine the structural state due to the absence of current on the primary side, or the masking of poor contact due to the presence of current. The state detection results are stable and reliable.

[0018] This invention elevates single-level distance detection to multi-level state recognition, including closed, half-open, and falsely opened states, by forming at least three signal intervals using at least two preset thresholds within the main control unit. The invention introduces a differential arrangement scheme with dual Hall sensors. By identifying characteristics such as the amplitude ratio deviation between the first and second detection signals, signal cyclical fluctuations, and repeated threshold crossings of the difference, it can determine whether an equivalent air gap exists between the movable top cover and the fixed housing, thereby distinguishing the indirect connection state from the half-open state.

[0019] This invention corrects the zero-point drift and sensitivity changes of the Hall sensor through a temperature acquisition unit and a temperature compensation calibration table, ensuring the accuracy of the threshold discrimination under different ambient temperatures; and through a duration discrimination mechanism, it effectively eliminates misjudgments caused by instantaneous interference such as vibration. Attached Figure Description

[0020] Figure 1 This is an overall structural diagram of the device shown in this invention.

[0021] Figure 2 This is a diagram showing the arrangement of the magnet and Hall sensor in this invention.

[0022] Figure 3 This is a schematic diagram of the Hall output hierarchy in this invention.

[0023] Figure 4 This is a flowchart of the graded alarm method of the present invention.

[0024] Figure label: 1-Fixed housing; 2-Modible top cover; 3-Fixed iron core; 4-Modible iron core; 5-Magnet; 6-Hall sensor; 7-Signal conditioning circuit; 8-Main control unit; 9-Temperature compensation module; 10-Communication module; 11-Alarm output module; 12-First threshold; 13-Second threshold; 14-Third threshold; 15-Hall output curve. Detailed Implementation

[0025] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It is to be understood that the specific embodiments described herein are merely illustrative of this application and not intended to limit it. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0026] The terms used in this application include and have, and any variations thereof, and are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0027] References to embodiments herein mean that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly or implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] This invention provides an openable current transformer, a state identification device, and a method, aiming to solve the problem in the prior art that the mechanical closed state of an openable current transformer cannot be reliably identified. This invention constructs a dedicated position sensing channel independent of the primary side's working magnetic field by installing a magnet in the movable upper cover and a Hall sensor in the fixed housing.

[0029] Please see Figure 1 The openable current transformer provided by the present invention mainly includes a fixed housing 1, a movable top cover 2, a fixed iron core 3, a movable iron core 4, a locking assembly, a magnet 5, a Hall sensor 6, a signal conditioning circuit 7, a main control unit 8, and associated temperature compensation module 9, communication module 10 and alarm output module 11.

[0030] The fixed housing 1 serves as the basic supporting component of the entire current transformer, housing and fixing a roughly U-shaped or C-shaped fixed iron core 3. The movable top cover 2 is movably connected to the fixed housing 1 via a hinge or similar pivoting mechanism, and can reciprocate between a closed position and a fully open position. The movable iron core 4 is fixedly installed inside the movable top cover 2. When the movable top cover 2 is in the closed position and the locking assembly is reliably locked, the end faces of the fixed iron core 3 and the movable iron core 4 will achieve a tight mechanical fit, thus forming a complete, low-resistivity annular magnetic circuit, ensuring that the current transformer can measure with rated accuracy.

[0031] To achieve non-contact sensing of the mechanical closure state, the magnet 5 is fixedly mounted on the inner wall of the movable cover 2, or on any component with a defined linkage relationship to the movable cover 2, such as the movable end of the latch assembly. The Hall sensor 6 is fixedly mounted at a predetermined position on the fixed housing 1, a position that ensures that when the movable cover 2 is closed, the Hall sensor 6 is directly opposite the magnet 5 and spatially close to it. The output signal of the Hall sensor 6 has an amplitude that depends on the linear distance between the magnet 5 and the Hall sensor 6.

[0032] When the movable cover 2 becomes loose, shifts, or opens, the distance increases, the magnetic field strength decreases accordingly, and the output signal amplitude of the Hall sensor 6 decreases accordingly. Crucially, this detection process is completely independent of the operating current flowing through the primary conductor at the center of the transformer. Even if there is no current in the primary circuit, as long as the movable cover 2 is fully closed, the Hall sensor 6 can output a high-amplitude reference signal; conversely, even if there is a large current in the primary circuit, if the movable cover 2 is partially open, the Hall sensor 6 can accurately detect the weakening of the magnetic field strength.

[0033] In this invention, the Hall sensor 6 is preferably a linear Hall sensor. The output of a linear Hall sensor is an analog voltage signal, the amplitude of which is continuously linearly proportional to the sensed magnetic flux density. Compared with a switch-type Hall sensor that can only output 0 or 1, a linear Hall sensor can reflect subtle changes in the distance between the magnet 5 and the Hall sensor 6, thus providing a data basis for multi-level state division.

[0034] The analog signal is first fed into signal conditioning circuit 7. Signal conditioning circuit 7 typically includes a low-pass filter network and a signal amplification circuit. The low-pass filter network is used to remove high-frequency noise components introduced by power frequency magnetic fields, electromagnetic interference, etc.; the amplification circuit adjusts the weak millivolt-level signal output by Hall sensor 6 to a volt-level range suitable for analog-to-digital conversion. The conditioned analog signal is then sent to main control unit 8. Main control unit 8 typically employs a microcontroller or digital signal processor with an integrated analog-to-digital converter, which converts the analog signal into a digital quantity for subsequent logical judgment and algorithm processing.

[0035] The main control unit 8 in this invention pre-stores at least two, preferably three or more, calibrated voltage thresholds. These thresholds divide the entire effective output signal range of the Hall sensor 6 into at least three, preferably four or more signal intervals. Each signal interval corresponds to a specific state.

[0036] Specifically, please see Figure 2 The figure depicts the typical variation of the Hall output curve 15 under the single Hall sensor scheme as the movable cover 2 gradually moves from the closed position (displacement of 0) to the fully open position (displacement of maximum). The curve exhibits a non-linear decay characteristic, with the slope being the largest near the closed point, and then gradually flattening out. Based on this curve, this scheme sets a first threshold 12, a second threshold 13, and a third threshold 14.

[0037] The first threshold 12 is a relatively high voltage value, close to the saturation output range of the Hall sensor 6 in its ideal closed state. When the amplitude of the real-time detection signal after digital processing is greater than or equal to the first threshold 12, the main control unit 8 determines that the movable cover 2 is in a normally closed state. This state indicates that the movable cover 2 has been reliably locked by the locking assembly, the end faces of the fixed iron core 3 and the movable iron core 4 are tightly fitted, and the magnetic circuit is intact. In this state, the alarm output module 11 does not generate any alarm signal, or only outputs a green indicator signal indicating normal operation.

[0038] The second threshold 13 is a voltage value lower than the first threshold 12. When the amplitude of the real-time detection signal is between the first threshold 12 and the second threshold 13, the main control unit 8 determines that the transformer has entered the warning zone. This zone corresponds to the situation where the movable cover 2, although not fully opened, has already shown looseness or slight displacement beyond the allowable range.

[0039] To eliminate misjudgments caused by momentary interference such as vibration, the main control unit 8 starts a duration discrimination timer. An alarm signal will only be output when the amplitude of the detection signal is continuously maintained for more than a preset first time threshold (e.g., 500 milliseconds or 1 second) within this range, indicating that the locking assembly may not be fully locked in place, or that the current transformer has become initially mechanically loose due to vibration during long-term operation.

[0040] The third threshold 14 is a lower voltage value, close to the lower limit of the output of Hall sensor 6 when the movable cover 2 is fully open. When the amplitude of the real-time detection signal is between the second threshold 13 and the third threshold 14, the main control unit 8 determines that the transformer is in a half-open or loosely connected state. At this time, there is a significant equivalent air gap between the end faces of the fixed iron core 3 and the movable iron core 4. This air gap increases the magnetic reluctance of the magnetic circuit, causing the excitation current of the transformer to increase. This not only causes the measurement error to exceed the tolerance, but also causes the iron core to overheat, which may burn out the transformer after long-term operation. When the signal falls into this area and the duration exceeds a more stringent second time threshold (e.g., 200 milliseconds continuously), the main control unit 8 will output a second-level alarm signal.

[0041] When the amplitude of the detected signal further decreases to below the third threshold 14, the main control unit 8 determines that the transformer is in a high-confidence false opening state. This means that the movable cover 2 has been clearly opened, fully popped open, or has undergone a significant lateral displacement that has caused the magnet 5 to almost completely deviate from the sensing range of the Hall sensor 6.

[0042] To achieve more accurate and intelligent status judgment, the main control unit 8 introduces the signal change rate as an auxiliary criterion. For example, when the movable cover 2 pops open rapidly due to a sudden snap, the Hall signal will drop at a very steep slope. By calculating this change rate, the main control unit 8 can quickly lock the false opening event if its absolute value exceeds a preset change rate threshold. It can immediately trigger a level three alarm without waiting for the duration timer to accumulate to the normal duration, thus achieving rapid response.

[0043] In a particularly preferred embodiment of the present invention, to overcome the influence of ambient temperature on the output characteristics of the linear Hall sensor (especially zero-point drift and sensitivity drift), a temperature compensation module 9 is integrated into the system. The temperature compensation module 9 contains a high-precision digital temperature sensor for real-time measurement of the current ambient temperature or the operating temperature of the transformer body. This temperature sensor is electrically connected to the main control unit 8 and transmits real-time temperature data to the main control unit 8.

[0044] The main control unit 8 internally contains an experimentally calibrated temperature compensation lookup table. This lookup table records the relationship between the output signal amplitude of the Hall sensor 6 and temperature changes in the standard closed position. Before each state judgment, the main control unit 8 first reads the current temperature value, and then uses this lookup table or a pre-fitted polynomial compensation formula to correct the original Hall signal value obtained from the analog-to-digital converter. The specific compensation algorithm can be: H... corrected = H raw + α(T) * (T - T ref ), where α(T) may be a linear or quadratic function of temperature. Alternatively, a lookup table method can be used: for each possible temperature range, the corresponding zero-point correction value and sensitivity correction coefficient are pre-stored.

[0045] By performing precise temperature compensation on the Hall signal, this invention completely eliminates the problem of blurred decision threshold boundaries caused by high summer temperatures and low winter temperatures, ensuring that the hierarchical alarm logic remains consistent and reliable.

[0046] This invention further solves the problem of lateral displacement that may occur when the movable cover 2 is closed. Although a single Hall sensor can detect distance changes, it cannot distinguish between two situations: vertical incomplete closure and horizontal displacement with normal vertical height. Therefore, this invention provides a dual Hall differential arrangement scheme.

[0047] In this embodiment, two Hall sensors are arranged at intervals on the fixed housing 1 along the expected movement trajectory (or potential offset direction) of the magnet 5. The magnet 5 moves under the action of the movable cover 2. When the movable cover 2 is accurately and centrally closed, the magnet 5 simultaneously approaches the two Hall sensors 6. Due to the magnetic field distribution characteristics of the magnet 5, the signal amplitudes output by the two sensors are basically equal, and their difference ΔH = |H1-H2| is close to zero or within a very small symmetric tolerance range.

[0048] The degree of offset is the amount of lateral displacement of the movable cover 2 in a plane perpendicular to the closing direction. When the movable cover 2 shifts laterally, for example to the right, the magnet 5 will move closer to the first Hall sensor and further away from the second Hall sensor.

[0049] At this point, the signal amplitude H1 output by the first Hall sensor will decrease less or even remain unchanged (if the original magnet's center is biased to the left), while the signal amplitude H2 output by the second Hall sensor will decrease significantly. The difference ΔH between the two will immediately change from near 0 to a definite positive or negative non-zero value. The absolute value of this difference directly quantifies the magnitude of the offset, and its sign indicates the direction of the offset.

[0050] For distinguishing between offset and open states, the dual-Hall sensor solution provides unique logic that a single-Hall sensor cannot achieve. For example, consider an extreme but common fault scenario: although the latch assembly is engaged in the closed position, due to obstruction by foreign objects or buckle deformation, the movable cover 2 is in a tilted state—one side is pressed into place, while the other side remains open by a few millimeters. In this case, if only a single-Hall sensor is used, its output signal amplitude might fall precisely into the secondary suspected half-open zone. However, this cannot distinguish whether the cover is uniformly half-open or tilted. With a dual-Hall sensor, the main control unit 8 will simultaneously detect H1 in the normal closed zone and H2 in the secondary warning zone. By calculating that the ratio H1 / H2 deviates significantly from the preset closed amplitude ratio, the main control unit 8 can immediately determine that there is a significant offset and output the corresponding alarm information accordingly.

[0051] To more sensitively detect loosening events, the main control unit 8 further dynamically monitors the signals from the first Hall sensor and the second Hall sensor. For example, when the first detection signal and the second detection signal exhibit any of the following typical characteristics, the main control unit 8 will determine that there is an unacceptable equivalent air gap between the movable top cover 2 and the fixed housing 1, and forcibly determine the current state as a half-open state or an accidentally opened state.

[0052] When the system is in a steady-state, normally closed state, the value of ΔH remains stable within ±δ (a small dead zone threshold). If the main control unit 8 detects that ΔH jumps from ±δ to a value much greater than δ within a very short time (e.g., within 10 milliseconds), this strongly indicates that the latch has slipped off instantly or the top cover has experienced an impact-induced shift. Even if the two absolute amplitudes H1 and H2 have not yet completely fallen below the third threshold 14, the system can determine in advance that this is a precursor to accidental opening and output a warning.

[0053] When a locking system with slight mechanical clearance is subjected to external vibration, the movable cover 2 may generate high-frequency micro-vibrations relative to the fixed housing 1. These vibrations manifest as the amplitudes of H1 and / or H2 oscillating back and forth at a high frequency between the normal closed range and the warning range. The main control unit 8 performs spectral analysis or simple counting comparison on the received signal sequence. If H1 or H2 is detected repeatedly crossing the first threshold 12 a preset number of times (e.g., more than 3 times) within a unit of time (e.g., within 1 second), it is determined that the locking system has a false lock or severe wear. Even if the fluctuation center value is still high, a level one mechanical abnormality or a higher level two suspected partial opening alarm can be output.

[0054] If the system detects that the value of ΔH exhibits a monotonically slow changing trend over several minutes or hours, such as H1 gradually decreasing while H2 gradually increases, this indicates that the movable cover 2 is slowly deflecting due to thermal expansion and contraction or mechanical creep. Based on this, the main control unit 8 can predict future failure risks and output a predictive maintenance alarm in advance.

[0055] In another important embodiment, the present invention quantifies and evaluates the degree of abrupt change in the difference signal of the dual Hall effect sensor. The degree of abrupt change is defined as the change in the difference signal ΔH within a unit time Δt, i.e., the first derivative d(ΔH) / dt. When the latch breaks open, the absolute value of d(ΔH) / dt reaches a maximum value. The main control unit 8 has an internal threshold for the degree of abrupt change. Once the detected d(ΔH) / dt value exceeds this threshold, the system immediately triggers the highest priority interlocking protection, driving the relay output unit of the alarm output module 11 to directly cut off the sampling circuit on the secondary side of the transformer or send a trip command to the upper-level protection device.

[0056] The alarm output module 11 includes multiple output formats. Local indicators include multi-color LEDs (e.g., green for normal operation, yellow for level 1 alarm, orange for level 2 alarm, and red for level 3 alarm) and a buzzer for providing audible and visual alerts on-site. The relay output unit provides one or more pairs of passive dry contacts, which can be easily connected to the user's automation system, such as directly connecting to the PLC's digital input module or being connected in series in the control loop to achieve shutdown interlocking. The communication module 10 supports common industrial fieldbus protocols and can package and send all raw diagnostic data, including the original Hall effect value before temperature compensation, the compensated value, the values ​​of the first and second Hall effect sensors, the difference ΔH, the degree of change d(ΔH) / dt, and the timestamp of the event duration, to a host computer or cloud maintenance platform. The event logging unit stores all alarm events in non-volatile memory, forming a log for easy fault tracing and analysis afterward.

[0057] Example 1 Please see Figure 1 The openable current transformer provided by the present invention mainly includes a fixed housing 1, a movable top cover 2, a fixed iron core 3, a movable iron core 4, a locking assembly, a magnet 5, a Hall sensor 6, a signal conditioning circuit 7, a main control unit 8, and associated temperature compensation module 9, communication module 10 and alarm output module 11.

[0058] The fixed housing 1 serves as the basic supporting component of the entire transformer, housing and fixing a roughly U-shaped or C-shaped fixed iron core 3. The movable top cover 2 is movably connected to the fixed housing 1 via a hinge or similar pivoting mechanism, and can reciprocate between a closed position and a fully open position. The movable iron core 4 is fixedly installed inside the movable top cover 2. When the movable top cover 2 is in the closed position and the locking assembly is reliably locked, the end faces of the fixed iron core 3 and the movable iron core 4 will achieve a tight mechanical fit, thus forming a complete, low-resistivity annular magnetic circuit.

[0059] When the movable cover 2 becomes loose, shifts, or opens, the distance increases, the magnetic field strength decreases accordingly, and the output signal amplitude of the Hall sensor 6 decreases accordingly. This detection process is completely independent of the operating current flowing through the primary conductor at the center of the transformer: even if there is no current in the primary circuit, as long as the movable cover 2 is closed, the Hall sensor 6 can output a high-amplitude reference signal; conversely, even if there is a large current in the primary circuit, if the movable cover 2 is half-open, the Hall sensor 6 can accurately detect the weakening of the magnetic field strength.

[0060] Example 2 In this invention, the Hall sensor 6 is preferably a linear Hall sensor. The output of the linear Hall sensor is an analog voltage signal, the amplitude of which is continuously linearly proportional to the sensed magnetic flux density. This analog signal is first sent to the signal conditioning circuit 7, and after low-pass filtering and amplification, it is sent to the main control unit 8.

[0061] The main control unit 8 has at least two, preferably three or more, calibrated voltage thresholds pre-stored inside. These thresholds divide the entire effective output signal range of the Hall sensor 6 into at least three, preferably four or more signal intervals.

[0062] Please see Figure 2 This scheme sets a first threshold 12, a second threshold 13, and a third threshold 14. The first threshold 12 is a relatively high voltage value, close to the saturation output range under ideal closed conditions. When the amplitude of the real-time detection signal after digital processing is greater than or equal to the first threshold 12, it is determined that the movable cover 2 is in a normal closed state.

[0063] The second threshold 13 is a voltage value lower than the first threshold 12. When the amplitude of the real-time detection signal is between the first threshold 12 and the second threshold 13, the transformer is determined to have entered the warning zone. Only when the amplitude of the detection signal continuously exceeds a preset first time threshold within this range will a first-level alarm signal be output. The third threshold 14 is an even lower voltage value. When the amplitude of the real-time detection signal is between the second threshold 13 and the third threshold 14 and the duration exceeds the second time threshold, it is determined to be in a half-open or loose connection state and a second-level alarm signal is output. When the amplitude of the detection signal is lower than the third threshold 14, it is determined to be a high-confidence false opening and a third-level alarm is output.

[0064] In addition, the main control unit 8 also introduces the signal change rate as an auxiliary criterion. When the Hall signal drops at a very steep slope and the absolute value of the slope exceeds the preset change rate threshold, the false opening event will be quickly locked and a level three alarm will be triggered immediately.

[0065] Example 3 To overcome the influence of ambient temperature on the output characteristics of the linear Hall sensor, a temperature compensation module 9 is integrated into the system. The temperature compensation module 9 contains a high-precision digital temperature sensor for real-time measurement of the current ambient temperature or the operating temperature of the transformer itself. The main control unit 8 internally encapsulates an experimentally calibrated temperature compensation lookup table. Before each state judgment, the main control unit 8 first reads the current temperature value, and then uses this lookup table or a pre-fitted polynomial compensation formula to correct the original Hall signal value. By performing precise temperature compensation on the Hall signal, this invention eliminates the problem of ambiguous decision threshold boundaries, ensuring the reliability of the graded alarm logic at all times.

[0066] Example 4 To address the potential lateral displacement issue that may occur when the movable cover 2 closes, this invention provides a dual-Hall differential arrangement scheme. Two Hall sensors are spaced apart on the fixed housing 1 along the expected movement trajectory or potential displacement direction of the magnet 5. When the movable cover 2 is accurately aligned and closed, the amplitudes of the output signals from the two sensors are essentially equal, and their difference ΔH is close to zero.

[0067] When the movable cover 2 shifts laterally, the magnet 5 will move closer to one of the Hall sensors and further away from the other. The difference between the two sensors, ΔH, will become a distinct positive or negative non-zero value. The absolute value quantifies the degree of shift, and the sign indicates the direction of shift. When the ratio of H1 to H2 deviates significantly from the preset closing amplitude ratio, the main control unit 8 immediately determines that there is a significant shift and outputs the corresponding alarm information.

[0068] The main control unit 8 also dynamically monitors the dual Hall effect signals. When ΔH jumps from the normal range to a value much larger than the normal value in a very short time, even if the absolute amplitude has not yet completely fallen into the abnormal zone, it can be determined in advance as a precursor to false opening and an early warning can be output. When the amplitudes of H1 and / or H2 fluctuate back and forth at a high frequency between the normal closed interval and the warning interval, and repeatedly cross the first threshold a preset number of times within a unit of time, it is determined that the locking system has a false lock or severe wear and an alarm is output. If ΔH is detected to show a monotonically slow changing trend over a long period of time, a predictive maintenance alarm can be output accordingly.

[0069] In addition, the main control unit 8 also performs a quantitative assessment of the degree of change in ΔH. When the detected first derivative d(ΔH) / dt value exceeds the degree of change threshold, the system will immediately trigger the highest priority interlocking protection, driving the relay output unit of the alarm output module 11 to directly cut off the secondary side sampling circuit of the current transformer or send a trip command to the upper-level protection device.

[0070] Example 5 In actual deployment, due to differences in magnetization of the magnet 5, sensitivity tolerance of the Hall sensor 7, and slight differences in installation position, the absolute signal amplitude of each current transformer in its closed state exhibits dispersion. To eliminate this influence, the main control unit 8 integrates a self-learning reference establishment program. After the device is initially powered on or manually confirmed, the main control unit 8 collects the initial 1000 sets of closed state signals, performs statistical averaging, and uses this average value as the personalized zero-point reference for that specific device. All preset thresholds are converted into a certain attenuation ratio relative to this zero-point reference, thereby achieving dynamic and adaptive threshold adjustment. This scheme ensures that the accuracy of state recognition is not affected by component consistency deviations, and the manufacturing process eliminates the need for cumbersome individual unit calibration.

[0071] Comparative Example 1 One solution uses a mechanical microswitch to detect the closed state of the cover. If the cover is half-open but the contacts are still pressed down, the system will incorrectly report that it is normally closed. This invention, however, uses a linear Hall sensor to sense the continuously changing distance between the magnet and the sensor. Any slight half-open or intermittent connection will cause the magnetic field strength to decrease proportionally, thus being detected and triggering a graded alarm.

[0072] Comparative Example 2 A scheme for directly measuring changes in main magnetic flux by installing Hall elements at the opening / closing section of the iron core. The Hall element signal is determined by both the primary side current and the contact state of the iron core. When the primary side line is unloaded, even if the movable cover is fully opened, the Hall element outputs a zero signal, and the system cannot distinguish it from normal no-load conditions, leading to serious missed alarms.

[0073] Comparative Example 3 A detection scheme using only a single switch-type Hall effect device and a single threshold value. This scheme can only distinguish between closed and open states. It cannot provide warnings for minor loosening caused by latch wear or vibration, or for devices in a critical half-open state about to disengage.

[0074] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A switchable current transformer, comprising a fixed iron core (3) and a movable iron core (4), characterized in that, Also includes: Fixed housing (1); The movable top cover (2) is movably connected to the fixed housing (1) and can move between a closed position and an open position. The fixed iron core (3) is disposed inside the fixed housing (1), and the movable iron core (4) is disposed inside the movable top cover (2). A locking assembly (5) is disposed between the fixed housing (1) and the movable upper cover (2) for locking the movable upper cover (2) in the closed position; A magnet (6) is disposed on the movable upper cover (2) or a component that is linked to the movable upper cover (2); At least one Hall sensor (7) is fixed on the fixed housing (1) and corresponds to the position of the magnet (6) for outputting a detection signal related to the distance between the magnet (6) and the Hall sensor (7); The main control unit is electrically connected to the Hall sensor (7). The main control unit has at least two preset thresholds to form at least three signal intervals. The main control unit is configured to determine the current state in a multi-level state set including closed state, half-open state and false open state according to the signal interval into which the amplitude of the detected signal falls, and output a graded signal corresponding to the current state. When the movable top cover (2) is in the closed position and the locking assembly (5) is in the locked position, the end faces of the fixed iron core (3) and the movable iron core (4) are in contact with each other.

2. The switchable current transformer according to claim 1, characterized in that, The at least one Hall sensor (7) includes a linear Hall sensor, and the detection signal is an analog signal; the main control unit includes an analog-to-digital converter module for converting the analog signal into a digital signal.

3. The switchable current transformer according to claim 2, characterized in that, The main control unit is configured to determine the current state as the half-open state when the amplitude of the detection signal corresponding to the digital signal falls into the middle interval of the at least three signal intervals and the duration exceeds a preset time threshold.

4. The switchable current transformer according to claim 1, characterized in that, The at least one Hall sensor (7) includes a first Hall sensor and a second Hall sensor arranged at intervals along the movement direction of the magnet (6); the main control unit is electrically connected to the first Hall sensor and the second Hall sensor respectively, and is configured to determine the offset direction or offset degree of the movable cover (2) during the closing or locking process based on the difference between the first detection signal output by the first Hall sensor and the second detection signal output by the second Hall sensor.

5. The switchable current transformer according to claim 1, characterized in that, It also includes a temperature acquisition unit (9), which is electrically connected to the main control unit; the main control unit is configured to perform temperature compensation on the detection signal based on the ambient temperature value acquired by the temperature acquisition unit (9), and then determine the current state.

6. The switchable current transformer according to claim 5, characterized in that, The main control unit stores a temperature compensation calibration table. The main control unit queries the temperature compensation calibration table based on the ambient temperature value to perform zero-point correction or sensitivity correction on the detection signal.

7. The switchable current transformer according to claim 1, characterized in that, The graded signals include a first-level mechanical abnormality signal, a second-level suspected half-open signal, and a third-level highly reliable false opening signal; the first-level mechanical abnormality signal corresponds to the locking assembly (5) not being locked, the second-level suspected half-open signal corresponds to the movable upper cover (2) being in a half-open or loosely connected state, and the third-level highly reliable false opening signal corresponds to the movable upper cover (2) being obviously open or offset.

8. The switchable current transformer according to claim 4, characterized in that, The main control unit is further configured to determine that there is an equivalent air gap between the movable upper cover (2) and the fixed housing (1) when the first detection signal and the second detection signal exhibit any of the following characteristics, and to determine the current state as the half-open state: The amplitude ratio of the first detection signal and the second detection signal when the movable cover (2) is in the closed position deviates from the preset closing amplitude ratio, and the deviation remains consistent before and after the locking assembly (5) is locked. The amplitude of the first detection signal or the second detection signal fluctuates back and forth between the signal interval corresponding to the closed position and the intermediate interval, and the number of fluctuations exceeds a preset threshold. The difference between the first detection signal and the second detection signal repeatedly crosses a preset fluctuation threshold within a preset time period.

9. A switching current transformer status identification device, characterized in that, include: Fixed housing (1); The movable top cover (2) is movably connected to the fixed housing (1) and is used to move between a closed position and an open position; A locking assembly (5) is disposed between the fixed housing (1) and the movable upper cover (2) for locking the movable upper cover (2) in the closed position; A magnet (6) is disposed on the movable upper cover (2) or a component that is linked to the movable upper cover (2); At least one Hall sensor (7) is fixed on the fixed housing (1) and corresponds to the position of the magnet (6) for outputting a detection signal related to the distance between the magnet (6) and the Hall sensor (7); The main control unit is electrically connected to the Hall sensor (7). The main control unit has at least two preset thresholds to form at least three signal intervals. The main control unit is configured to determine the current state in a multi-level state set including closed state, half-open state and false open state according to the signal interval into which the amplitude of the detected signal falls, and output a graded signal corresponding to the current state.

10. A method for identifying the state of an open-close current transformer, characterized in that, include: Acquire a detection signal output by at least one Hall sensor (7) fixed on the fixed housing (1), the detection signal reflecting the relative distance between the magnet (6) disposed on the movable cover (2) and the Hall sensor (7); The amplitude of the detected signal is compared with at least two preset thresholds to determine the signal interval into which the amplitude falls, and the at least two thresholds form at least three signal intervals; When the amplitude falls within the first signal range, it is determined to be in a closed state; when the amplitude falls within the second signal range, it is determined to be in a half-open state; when the amplitude falls within the third signal range, it is determined to be in an erroneous open state. Output a hierarchical signal corresponding to the determined state.

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