A transformer alarm system

Abstract

The application discloses a mutual inductor alarm system, which comprises a mechanical state detection module, an electric parameter detection module, a secondary sampling module, a main control module, a communication module and a local alarm module. The mechanical state detection module outputs mechanical state quantities reflecting the locking state or the compression state. The electric parameter detection module obtains impedance or phase electric parameter state quantities by injecting a test signal higher than the power frequency into the secondary winding. The secondary sampling module collects the secondary current effective value. The main control module is internally provided with a fusion criterion unit, a hierarchical alarm unit and a health score unit. The mutual inductor false opening state is judged by fusing the mechanical state quantities, the electric parameter state quantities and the secondary current effective value, and an alarm code is generated. Meanwhile, a health score value reflecting the health degree of the device is generated.

Description

Technical Field

[0001] This invention relates to the field of power system online monitoring and fault early warning technology, and in particular to an alarm system for switchable current transformers. Background Technology

[0002] Openable current transformers are widely used in power distribution automation, electricity monitoring, and energy efficiency management. Their structure consists of an openable / closable movable part and a fixed part, with the core end face pressed shut via a locking mechanism. In actual operation, due to improper installation, fatigue or aging of the locking mechanism, or vibration in the operating environment, the transformer may experience issues such as incomplete locking, poor contact at the core end face, or accidental loosening of the movable part, leading to potential opening problems. These issues can disrupt the continuity of the magnetic circuit, causing a decrease in measurement accuracy. In severe cases, they may trigger abnormal overvoltages on the secondary side or cause measurement data failure, affecting the reliable operation of subsequent protection devices and metering systems.

[0003] There are two main methods for detecting the erroneous opening state of open-type current transformers. One method involves directly sensing the mechanical position of the moving parts by installing a mechanical limit switch or magnetic sensing element at the latch position. This method is simple in structure but can only determine the macroscopic "open" and "closed" states, failing to identify the loose connection state where the latch is engaged but the core end face is not pressed tightly, and is insensitive to minute displacements and contact quality degradation. The other method involves inferring the magnetic circuit state by monitoring the amplitude change of the secondary side power frequency output signal. This method is greatly affected by the primary side load conditions. When the primary circuit is under no-load or light-load conditions, even if the core is fully open, the secondary side power frequency signal will not have a significant output, making it difficult to distinguish from normal no-load conditions and posing a risk of missed alarms. Furthermore, neither of these methods can quantitatively assess the long-term health status of the transformer, making it difficult for maintenance personnel to determine the urgency of the fault based on alarm information, and also hindering predictive maintenance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and solve at least one of the problems shown in the background art.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows.

[0006] A current transformer alarm system includes a fixed housing and a movable top cover, and further includes: Mechanical condition monitoring module, electrical parameter monitoring module, secondary sampling module, main control module, communication module, and local alarm module; The mechanical condition detection module is located between the fixed housing and the movable top cover, and its output end is connected to the main control module to output mechanical condition quantities. The electrical parameter detection module is connected to the secondary winding, and its output terminal is connected to the main control module to output electrical parameter status quantities. The secondary sampling module is connected to the secondary circuit, and its output terminal is connected to the main control module to output the effective value signal of the secondary current. The main control module has a built-in fusion criterion unit, a graded alarm unit, and a health scoring unit. The fusion criterion unit performs graded judgment on the transformer erroneous opening state based on the mechanical state quantity, electrical parameter state quantity, and secondary current effective value signal. The graded alarm unit generates an alarm code, and the health scoring unit generates a health score value.

[0007] Optionally, the mechanical condition detection module is at least one of a micro switch, a reed switch, a linear Hall sensor, and a pressure sensor; the pressure sensor contacts the locking assembly through an elastic pressure block to reflect the clamping force state.

[0008] Optionally, the electrical parameter detection module includes a test signal injection unit and a parameter processing unit. The test signal generated by the test signal injection unit has a frequency higher than the power frequency. The parameter processing unit extracts the voltage and current components with the same frequency as the test signal using synchronous demodulation technology, and calculates the test impedance Z accordingly. test Estimate the inductance L test or phase parameter φ test , which serves as the electrical parameter state quantity.

[0009] Optionally, the secondary sampling module includes a current sampling circuit and an RMS value calculation circuit, wherein the secondary current RMS value signal corresponds to the secondary current RMS value I. sec-rms .

[0010] Optionally, the fusion criterion unit will use the effective value of the secondary current I sec-rms With a preset static current threshold I th Comparisons are made to form runtime context criteria; when I sec-rms th When I is in a state of no current or power outage, it is determined that the primary circuit is in a state of no current or power outage. sec-rms When Ith is greater than or equal to Ith, it is determined that the primary circuit should have operating current.

[0011] Optionally, the hierarchical judgment of the hierarchical alarm unit is configured as follows: When the mechanical state quantity is abnormal relative to the preset mechanical state reference value, a first alarm signal is output; When the mechanical state quantity is normal but the electrical parameter state quantity is abnormal relative to the preset electrical parameter reference value, and the operating context criterion determines that the primary circuit is in a no-current or power outage condition, a second alarm signal is output. ​When both the mechanical state quantity and the electrical parameter state quantity are abnormal, and the operating context criterion determines that the primary circuit should have operating current, a third alarm signal is output.

[0012] Optionally, the health scoring unit obtains the health score value based on the deviation of the mechanical state quantity from the preset mechanical state reference value, the deviation of the electrical parameter state quantity from the preset electrical parameter reference value, and the duration of the abnormal state.

[0013] Optionally, the health scoring unit normalizes the deviations of the mechanical state quantity and the electrical parameter state quantity to obtain the mechanical health component and the electrical parameter health component. The health scoring unit accumulates the mechanical health component and the electrical parameter health component at each sampling time within a set evaluation time window with a preset sampling period, and multiplies them by a degradation coefficient related to the proportion of cumulative abnormal duration to obtain the health score value.

[0014] Optionally, the degradation coefficient is a non-linear function. When the proportion of the cumulative abnormal duration within the evaluation time window exceeds a set threshold, the degradation coefficient increases rapidly, and the rate of decline of the health score value accelerates accordingly.

[0015] Optionally, the health score is calculated according to the following formula: H = H0 - ∑t[w1·ΔM] norm (t)+w2·ΔE norm (t)]·f(T abnormal / T window ) Where H is the current health score, H0 is the maximum health score, and ΔM norm (t) represents the normalized mechanical state deviation at sampling time t, ΔE norm (t) represents the normalized electrical parameter deviation at sampling time t, w1 and w2 are the weighting coefficients of mechanical state deviation and electrical parameter deviation, respectively, and satisfy w1+w2=1, w2>w1, ∑t represents the deviation within the evaluation time window T. window The weighted biases at each sampling time are accumulated, T abnormal To assess the cumulative duration of abnormal states within a time window, f(T) abnormal / T window The degradation coefficient is the percentage of the cumulative abnormal duration T. abnormal / T window When the value is less than the set ratio threshold, the value is 1. After exceeding the set ratio threshold, the value is incremented by a function greater than 1, and the value range is from 1.0 to 2.0.

[0016] The advantages and beneficial effects of this invention are as follows: the locking state is obtained through the mechanical state detection module, the test impedance or phase parameter is obtained through the electrical parameter detection module, and the effective value of the secondary current is obtained through the secondary sampling module. The three types of information are comprehensively processed in the fusion criterion unit of the main control module, and the mechanical position information and the electromagnetic characteristics of the magnetic circuit are mutually verified, thus avoiding the problem of insufficient criterion from a single information source.

[0017] The health scoring mechanism introduced based on the graded alarm system continuously records the deviation amplitude and the distribution density of abnormal events within a set evaluation time window. A nonlinear degradation coefficient generates differentiated responses to sparse, occasional anomalies and dense, recurring anomalies. Occasional anomalies have limited impact on the score because the degradation coefficient remains at 1, while dense, recurring anomalies trigger a sharp drop in the score due to the accelerated increase in the degradation coefficient. Therefore, the system can reveal hidden faults such as intermittent contact defects or fatigue of the locking mechanism in advance based solely on the trend of health score changes, before the alarm level escalates. This invention enables the instrument transformer maintenance mode to proactively identify potential hazards. Attached Figure Description

[0018] Figure 1 This is a general block diagram of the system of the present invention.

[0019] Figure 2 This is a schematic diagram illustrating the fusion relationship between three types of information: mechanical state, electrical parameters, and operating context.

[0020] Figure 3 This is a flowchart of the hierarchical alarm logic.

[0021] Figure 4 This is a schematic diagram of the health score calculation process.

[0022] Figure label: 1-Mechanical condition detection module, 2-Electrical parameter detection module, 3-Secondary sampling module, 4-Main control module, 5-Fusion criterion unit, 6-Graded alarm unit, 7-Health scoring unit, 8-Communication module, 9-Local alarm module, 10-Latch status signal, 11-Test impedance signal, 12-Estimated inductance signal, 13-Phase parameter signal, 14-Secondary current RMS value signal, 15-Alarm code, 16-Health score value, 17-Remote monitoring platform. Detailed Implementation

[0023] 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.

[0024] The terms “comprising” and “having”, and any variations thereof, used in this application 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.

[0025] In this document, the term "embodiment" means 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.

[0026] Please see Figure 1 The present invention provides a current transformer alarm system, including a fixed housing and a movable top cover, and also includes a mechanical status detection module 1, an electrical parameter detection module 2, a secondary sampling module 3, a main control module 4, a communication module 8, and a local alarm module 9.

[0027] Before elaborating on the system workflow, it is necessary to explain the fault physical mechanism of the switchable current transformer in order to understand why this invention adopts a multi-source information fusion architecture.

[0028] The core of the openable current transformer is divided into a fixed part and a movable part, and the two parts are closed by end face pressing through a locking mechanism. Ideally, the fixed core and the movable core end faces are tightly fitted to form a complete low magnetic reluctance ring magnetic circuit, and the primary current is accurately converted into secondary current through electromagnetic induction.

[0029] However, the accidental opening state does not only refer to the extreme case of the movable cover fully opening; it is actually a continuous degradation spectrum from fully closed to fully open. In this spectrum, there are a series of intermediate states, such as the latch being engaged but the clamping force decreasing, the iron core end face being slightly misaligned due to vibration and wear, the presence of foreign objects or oxide layers between the end faces causing local suspension, and the latch being loose but the movable cover still remaining roughly in the closed position due to cable restraint.

[0030] These intermediate states introduce an equivalent air gap into the magnetic circuit. According to Ohm's law for magnetic circuits, magnetic reluctance is directly proportional to the air gap length and inversely proportional to the permeability. Even an air gap of only tens of micrometers can cause a sharp increase in magnetic reluctance, leading to a significant reduction in the alternating magnetic flux established in the core. The direct consequence is that the secondary-side transmission ratio deviates from the nominal value, resulting in decreased measurement accuracy; simultaneously, the excitation current nonlinearity increases, core heating intensifies, and long-term operation may burn out the transformer.

[0031] Traditional detection methods suffer from structural flaws when dealing with this degradation spectrum. Mechanical travel detection schemes relying on microswitches or reed switches can only determine whether the moving part has exceeded a specific spatial position threshold, binarizing the continuous degradation process into open or closed states. They are completely unable to detect the intermittent connection state where the clamping force is severely insufficient but the travel has not yet deviated to the trigger threshold. Electrical detection schemes relying on the secondary side power frequency output signal face the problem of criterion confusion: when the primary circuit is unloaded or de-energized, there is also no power frequency output on the secondary side, and the system cannot distinguish between normal no-load and fault open circuit; when there is current on the primary side but only a small equivalent air gap at the iron core end face, the excitation impedance is large at power frequency, and the small magnetic reluctance change is not obvious in the secondary current amplitude and is easily drowned out by measurement noise.

[0032] To address the complexity of the aforementioned physical mechanisms, this invention utilizes three sensing channels—mechanical state detection module 1, electrical parameter detection module 2, and secondary sampling module 3—to detect different features within the degradation spectrum, and then performs fusion judgment in the main control module 4, fundamentally overcoming the problem of insufficient criteria from a single information source.

[0033] The mechanical condition detection module 1 is located between the fixed housing and the movable top cover, and its output is connected to the main control module 4 to output mechanical condition parameters. The mechanical condition detection module 1 is at least one of a micro switch, a reed switch, a linear Hall sensor, and a pressure sensor.

[0034] In a preferred embodiment, the mechanical condition detection module 1 includes both a linear Hall sensor and a pressure sensor. The pressure sensor contacts the locking assembly via an elastic block, which converts the localized, potentially uneven, clamping force of the locking assembly into a concentrated and linearly measurable force signal, reflecting the clamping force status. When the clamping force of the locking mechanism decreases due to material creep or spring fatigue, the pressure sensor can detect the decrease in clamping force even if the position of the movable cover has not yet shifted in a way that can be sensed by a limit switch.

[0035] A linear Hall effect sensor, in conjunction with a permanent magnet mounted on the movable cover, measures the precise position of the cover relative to the fixed housing by sensing continuous changes in magnetic field strength over distance. Unlike a reed switch that only outputs a switching signal, the linear Hall effect sensor outputs an analog voltage signal proportional to distance. When the movable cover experiences a minute displacement of tens of micrometers due to a loose latch, this signal changes proportionally, providing high-resolution data for subsequent quantitative evaluation.

[0036] The electrical parameter detection module 2 is connected to the secondary winding, and its output is connected to the main control module 4 to output electrical parameter status values. The electrical parameter detection module 2 includes a test signal injection unit and a parameter processing unit.

[0037] The test signal injected by the test signal injection unit has a frequency higher than the power frequency. The parameter processing unit extracts the voltage and current components with the same frequency as the test signal through synchronous demodulation technology, and calculates the test impedance Z accordingly. test Estimate the inductance L test or phase parameter φ test , as an electrical parameter state quantity.

[0038] Choosing a test frequency higher than the power frequency completely separates the test response from the power frequency measurement signal in the frequency domain, avoiding mutual interference. At high frequencies, the excitation impedance is more sensitive to changes in the equivalent air gap. The excitation inductance L is directly proportional to the magnetic permeability of the magnetic circuit and inversely proportional to the equivalent air gap length. When a gap appears at the end face of the iron core, the permeability drops sharply, and L decreases significantly accordingly. Under the excitation of a test signal at frequency f, the inductive reactance is 2πfL. The higher the frequency, the greater the absolute value of the change in inductive reactance corresponding to the same change in inductance, and the higher the measurement resolution.

[0039] Under normal closed-circuit conditions, the core magnetic circuit is intact, the magnetizing inductance is large, and the secondary side exhibits high impedance and near-pure inductive characteristics to high-frequency test signals, with a phase angle close to 90 degrees. When the equivalent air gap is generated or increased, the inductance decreases, and the impedance magnitude decreases proportionally. Simultaneously, the phase angle between voltage and current shifts in the hysteresis direction due to the decrease in the inductive component, moving from near 90 degrees to 0 degrees. This shift is unidirectional and definite; as long as a gap appears at the core end face, the phase angle will inevitably hysteresis. Therefore, the hysteresis shift of the phase angle can serve as a reliable criterion for determining the presence of an opening / closing gap at the core end face, unaffected by the presence or absence of primary side current.

[0040] The secondary sampling module 3 is connected to the secondary circuit, and its output is connected to the main control module 4 to output the secondary current effective value signal 14. The secondary sampling module 3 includes a current sampling circuit and an effective value calculation circuit; the secondary current effective value signal 14 corresponds to the secondary current effective value I. sec-rms .

[0041] The main control module 4 has a built-in fusion criterion unit 5, a hierarchical alarm unit 6, and a health scoring unit 7.

[0042] Fusion criterion unit 5 first sets the effective value of the secondary current I sec-rms With a preset static current threshold I th The comparisons are used to form the runtime context criteria. This static current threshold I... th It is much lower than the rated secondary current of the transformer, but higher than the inherent noise level of the circuit. When Isec-rms < Ith, the primary circuit is judged to be in a no-current or power outage condition; when I... sec-rms ≥ I th When this is the case, it is determined that the primary circuit should have operating current.

[0043] Please see Figure 2 and Figure 3 The fusion criterion unit 5 performs a comprehensive classification judgment on the transformer erroneous opening state based on the mechanical state quantity, electrical parameter state quantity, and secondary current effective value signal 14, and the classification alarm unit 6 generates an alarm code 15 accordingly. The specific logic of the classification judgment is as follows.

[0044] When the mechanical state parameters deviate from the preset mechanical state reference value, a first alarm signal is output. This level of alarm indicates that the locking mechanism itself is malfunctioning, such as not locking, being loose, or experiencing mechanical wear. At this time, the system will issue an alarm regardless of the electrical parameters or operating conditions.

[0045] When the mechanical status is normal but the electrical status is abnormal relative to the preset electrical parameter reference value, and the operating context criterion determines that the primary circuit is in a no-current or power-off condition, a second alarm signal is output.

[0046] The above logic combination corresponds to an extremely subtle fault scenario: the locking mechanism has pressed the movable cover into place, but due to foreign objects, oxide film, or non-conductive deposits caused by fretting wear on the iron core end face, the magnetic circuit has not actually formed a complete low magnetic reluctance path. When there is no current in the primary circuit, this fault does not produce any power frequency manifestations and cannot be detected by traditional methods. However, the electrical parameter detection module 2, because it actively injects test signals, can still detect the abnormality of the magnetic circuit parameters.

[0047] When both mechanical and electrical state parameters are abnormal, and the operating context criterion determines that the primary circuit should have operating current, a third alarm signal is output. This indicates that the movable cover is likely to be obviously opened or severely misaligned, the iron core magnetic circuit is severely broken, and the primary circuit is operating under load. Not only is the measurement completely ineffective, but dangerous overvoltages may also be induced on the secondary side due to iron core saturation, requiring immediate action.

[0048] The three-level alarm system described above addresses the issues of real-time fault identification and classification. However, in actual industrial operations and maintenance, a more proactive question needs to be answered: can the deterioration trend be predicted in advance, before the fault develops to the point of triggering an alarm?

[0049] Please see Figure 4 The health scoring unit 7 calculates the health score 16 based on the deviations of the mechanical state quantities from the preset mechanical state reference values, the deviations of the electrical parameter state quantities from the preset electrical parameter reference values, and the duration of the abnormal state.

[0050] Specifically, health scoring unit 7 first normalizes the deviations of mechanical state variables and electrical parameter state variables to obtain mechanical health components and electrical parameter health components. Then, this unit accumulates the mechanical health components and electrical parameter health components at each sampling time within a set evaluation time window using a preset sampling period, and combines them with a degradation coefficient related to the proportion of accumulated abnormal duration to obtain a health score value of 16.

[0051] A health score of 16 is calculated using the following formula: H = H0 - ∑t[w1·ΔM] norm (t)+w2·ΔE norm (t)]·f(T abnormal / T window ) Where H is the current health score of 16, H0 is the maximum health score, and Δ Mnorm (t) represents the normalized mechanical state deviation at sampling time t, Δ Enorm (t) represents the normalized electrical parameter deviation at sampling time t. w1 and w2 are the weighting coefficients for mechanical state deviation and electrical parameter deviation, respectively, satisfying w1 + w2 = 1, and w2 > w1. The weight of electrical parameter deviation is greater than that of mechanical deviation, considering that changes in electrical parameters directly reflect the integrity of the magnetic circuit function, and have a more direct and definite impact on measurement accuracy. Σt represents the deviation within the evaluation time window T. window The weighted deviations at each sampling time are accumulated.

[0052] T abnormal To assess the cumulative duration of abnormal states within a time window. f(T) abnormal / T window ) represents the degradation coefficient.

[0053] A current transformer might experience a momentary parameter shift due to a strong external vibration, which would then return to normal; this does not necessarily indicate a decline in its inherent health. Another current transformer, however, might experience irreversible fatigue of its locking spring, causing the clamping force to decrease gradually each day. Although the deviation may be small on a single sampling, the duration of the abnormal condition accumulates. These two scenarios might yield similar scores in a simple deviation accumulation mode, but their indicative significance for equipment lifespan and operational risk differs.

[0054] The degradation factor is set to differentiate between the two scenarios mentioned above. This factor represents the percentage of cumulative abnormal duration T. abnormal / T windowWhen the deviation is less than the set threshold, the value is 1. At this point, the deduction in the health score is entirely determined by the weighted sum of the deviation amplitudes, and occasional instantaneous fluctuations have a relatively mild impact on the score. After exceeding the set threshold, the degradation coefficient increases according to a function greater than 1, ranging from 1.0 to 2.0. This means that once the transformer enters a persistent abnormal state, the system not only deducts points normally due to the accumulation of deviations, but also experiences an accelerated deduction penalty effect due to the degradation coefficient being greater than 1. The longer and more frequent the abnormality, the larger the degradation coefficient, and the faster the rate of decline of the health score value of 16, exhibiting a clear accelerated decay trend.

[0055] The following example illustrates the actual operation of this mechanism. Assume a current transformer H0 = 100, T... window = 24 hours, the proportion threshold is set to 5%, w1 = 0.4, w2 = 0.6.

[0056] During the first three months of normal operation, the deviations of mechanical and electrical parameters were minimal, the weighted deviation at each sampling time was almost zero, the cumulative abnormal duration was also close to zero, the degradation coefficient remained at 1, and the health score remained above 98.

[0057] Starting in the fourth month, fretting oxidation began to appear on the core end face, and intermittent hysteresis shifts in the phase angle occurred, meaning that the electrical parameters deviated periodically from their baseline values, while the mechanical parameters remained normal. At this point, the cumulative abnormal duration was approximately 0.5 hours per day, accounting for about 2%, which did not exceed the 5% threshold, and the degradation coefficient remained at 1. The health score of 16 gradually decreased to approximately 92 points due to the cumulative deviation. During this stage, the score decline mainly exhibited a gentle, linear trend.

[0058] In the sixth month, oxidation intensified, leading to an expansion of the equivalent air gap and a continued deviation of the phase angle from the baseline range. The cumulative abnormal duration increased to 3 hours per day, accounting for approximately 12.5%, exceeding the 5% threshold. At this point, the degradation coefficient rose to approximately 1.4 on an increasing function basis, and the health score of 16 began to decline rapidly, dropping to approximately 68 points. The scoring curve showed its first significant inflection point here, with a steeper slope.

[0059] In the eighth month, the locking springs experienced fatigue relaxation, and the clamping force remained consistently below the lower limit of the pressure reference range. Mechanical parameters also became abnormal. Both mechanical and electrical parameter deviations occurred simultaneously, and both were persistent rather than sporadic. The combined effect of these two anomalies caused the cumulative abnormal duration to exceed 30%, the degradation coefficient to rise to approximately 1.8, and the health score to plummet from 16 to below 40. The scoring curve formed a second, even steeper inflection point here, exhibiting a precipitous drop.

[0060] This example clearly illustrates the mechanism of accelerated score decay: in the early, intermittent anomaly phase, the degradation coefficient is 1, and the score decreases gradually and linearly; as the anomaly evolves from intermittent to persistent, the degradation coefficient jumps, and the score enters an accelerated decline phase; when multiple anomalies overlap, the score plummets. For operations and maintenance personnel, the shape of the score curve itself is the most intuitive warning signal. The inflection point from a gradual decline to an accelerated decline indicates that the degradation process has crossed the critical point, and planned maintenance must be arranged before the score falls below the safety threshold.

[0061] From the perspective of failure physics, the accumulation of fatigue damage in mechanical components and the expansion of fretting wear on contact surfaces often enter an accelerated development stage once a certain critical point is crossed. In the early stress relaxation stage of the locking spring, the clamping force decreases slowly, the iron core end face can still maintain basic contact, the equivalent air gap is extremely small, and the electrical parameter deviation is mainly manifested as a small hysteresis shift in the highly sensitive phase angle, with a very short cumulative abnormal duration. When the spring relaxation develops to the point that the clamping force is insufficient to resist operational vibrations, the movable cover begins to show intermittent slight loosening. The frequency and duration of loosening events both increase, the proportion of cumulative abnormal duration rises rapidly, and the degradation coefficient jumps accordingly. The nonlinear increasing design of the degradation coefficient essentially maps this physical accelerated damage accumulation effect to a mathematically accelerated decay of the score.

[0062] In the earliest stages of degradation, mechanical state variables often show no perceptible changes, but the electrical parameter detection module 2, due to its high sensitivity to the equivalent air gap, can detect abnormal signals first. The oxide film gradually growing on the core end face causes a measurable hysteresis shift in the phase angle of the test impedance even before the latching force decreases. The health scoring unit 7 records these early electrical parameter deviations and slowly deducts the health score value 16 using a weighted accumulation method. While a single deviation may be small, as long as the oxidation process continues, the abnormal state will evolve from sporadic to persistent, the degradation coefficient will increase, and the score will begin to decline rapidly. Therefore, the electrical parameter detection module 2 essentially provides the health scoring unit 7 with a flaw detection capability, allowing contact degradation that has not yet manifested at the mechanical level but has already begun at the electromagnetic level to be included in the health assessment model in advance.

[0063] The system also includes a communication module 8 and a local alarm module 9. The communication module 8 connects to the main control module 4 and supports wired or wireless communication. It is used to upload alarm codes 15, health score values ​​16, and underlying raw data, including mechanical state quantities, test impedance, estimated inductance, phase parameters, and secondary current RMS values, to the remote monitoring platform 17. The local alarm module 9 provides on-site alarms via multi-color LED indicators and a buzzer.

[0064] 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 current transformer alarm system, comprising a fixed housing and a movable top cover, characterized in that, Also includes: Mechanical condition detection module (1), electrical parameter detection module (2), secondary sampling module (3), main control module (4), communication module (8) and local alarm module (9); The mechanical state detection module (1) is located between the fixed housing and the movable top cover, and its output end is connected to the main control module (4) to output mechanical state quantities; The electrical parameter detection module (2) is connected to the secondary winding, and its output terminal is connected to the main control module (4) to output electrical parameter status quantities; The secondary sampling module (3) is connected to the secondary circuit, and its output terminal is connected to the main control module (4) to output the effective value signal (14) of the secondary current. The main control module (4) has a built-in fusion criterion unit (5), a graded alarm unit (6) and a health scoring unit (7). The fusion criterion unit (5) performs graded judgment on the transformer erroneous opening state based on the mechanical state quantity, electrical parameter state quantity and secondary current effective value signal (14). The graded alarm unit (6) generates an alarm code (15), and the health scoring unit (7) generates a health score value (16).

2. The current transformer alarm system according to claim 1, characterized in that, The mechanical condition detection module (1) is at least one of a micro switch, a reed switch, a linear Hall sensor, and a pressure sensor; the pressure sensor contacts the locking assembly through an elastic pressure block to reflect the clamping force state.

3. The current transformer alarm system according to claim 1, characterized in that, The electrical parameter detection module (2) includes a test signal injection unit and a parameter processing unit. The test signal generated by the test signal injection unit has a frequency higher than the power frequency. The parameter processing unit obtains the voltage and current components of the test signal at the same frequency and determines the test impedance Z accordingly. test Estimate the inductance L test or phase parameter φ test , which serves as the electrical parameter state quantity.

4. The current transformer alarm system according to claim 1, characterized in that, The secondary sampling module (3) includes a current sampling circuit and an RMS value calculation circuit. The secondary current RMS value signal (14) corresponds to the secondary current RMS value I. sec-rms .

5. The current transformer alarm system according to claim 4, characterized in that, The fusion criterion unit (5) will determine the effective value of the secondary current I. sec-rms With a preset static current threshold I th Comparisons are made to form runtime context criteria; when I sec-rms th When I is in a state of no current or power outage, it is determined that the primary circuit is in a state of no current or power outage. sec-rms When Ith is greater than or equal to Ith, it is determined that the primary circuit should have operating current.​ 6. The current transformer alarm system according to claim 5, characterized in that, The hierarchical judgment of the hierarchical alarm unit (6) is configured as follows: When the mechanical state quantity is abnormal relative to the preset mechanical state reference value, a first alarm signal is output; When the mechanical state quantity is normal but the electrical parameter state quantity is abnormal relative to the preset electrical parameter reference value, and the operating context criterion determines that the primary circuit is in a no-current or power outage condition, a second alarm signal is output. When both the mechanical state quantity and the electrical parameter state quantity are abnormal, and the operating context criterion determines that the primary circuit should have operating current, a third alarm signal is output.

7. The current transformer alarm system according to claim 1, characterized in that, The health scoring unit (7) calculates the health score (16) based on the deviation of the mechanical state quantity from the preset mechanical state reference value, the deviation of the electrical parameter state quantity from the preset electrical parameter reference value, and the duration of the abnormal state.

8. The current transformer alarm system according to claim 7, characterized in that, The health scoring unit (7) normalizes the deviations of the mechanical state quantity and the electrical parameter state quantity respectively to obtain the mechanical health component and the electrical parameter health component; the health scoring unit (7) accumulates the mechanical health component and the electrical parameter health component at each sampling time within a set evaluation time window with a preset sampling period, and obtains the health score value (16) by combining it with the degradation coefficient related to the cumulative abnormal duration.

9. The current transformer alarm system according to claim 8, characterized in that, The degradation coefficient is a non-linear function. When the proportion of the cumulative abnormal duration within the evaluation time window exceeds a set threshold, the degradation coefficient increases rapidly, and the rate of decrease of the health score (16) accelerates accordingly.

10. The current transformer alarm system according to claim 9, characterized in that, The health score (16) is calculated according to the following formula: H=H0-∑t[w1·ΔM norm (t)+w2·ΔE norm (t)]·f(T abnormal / T window ) Where H is the current health score (16), H0 is the maximum health score, and ΔM norm (t) represents the normalized mechanical state deviation at sampling time t, ΔE norm (t) represents the normalized electrical parameter deviation at sampling time t, w1 and w2 are the weighting coefficients of mechanical state deviation and electrical parameter deviation, respectively, and satisfy w1+w2=1, w2>w1, ∑t represents the deviation within the evaluation time window T. window The weighted biases at each sampling time are accumulated, T abnormal To assess the cumulative duration of abnormal states within a time window, f(T) abnormal / T window The degradation coefficient is the percentage of the cumulative abnormal duration T. abnormal / T window When the value is less than the set ratio threshold, the value is 1. After exceeding the set ratio threshold, the value is incremented by a function greater than 1, and the value range is from 1.0 to 2.0.

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