A current transformer measurement method

Abstract

The application discloses a current transformer measurement method, and particularly relates to the field of current transformer monitoring and measurement, which comprises the following steps: before the measurement of the current transformer starts, the nanocrystalline material made core of the current transformer is initially magnetized, and the core is brought to a saturation state through a magnetic field; a known alternating current signal is applied to the current transformer through a primary winding, the alternating current generates an alternating magnetic field in the core, and the magnetic flux in the core changes; after the current transformer senses the change of the current, an induced electromotive force is generated through a secondary winding, and a measurement value is represented; the induced current in the secondary winding and the induced current of the primary winding change in a fixed proportional relationship, and the induced current is transmitted to a measurement device for collection. Through real-time monitoring of the external mechanical stress density and the core magnetic permeability decline rate, the system can timely judge and respond to the high stress state, and ensure the working stability and measurement accuracy of the current transformer under the high stress condition.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current transformer monitoring measurement, and more particularly, to a current transformer measurement method. BACKGROUND

[0002] The current transformer is a device for converting high current into smaller current for use by measuring instruments or protective devices, which generates a magnetic field in the core through the primary winding to induce a small current proportional to the primary current in the secondary winding. The core of the current transformer can use nanocrystalline material, which has high magnetic permeability, low loss, low coercivity and high saturation magnetic induction, can significantly improve the measurement accuracy and efficiency in high frequency and strong current environment, reduce the degradation of the core in high stress state, and thus improve the long-term stability and working reliability of the transformer.

[0003] During the manufacturing or installation of the current transformer, the nanocrystalline material core may be affected by mechanical stress, such as excessive extrusion, improper fixation, etc. The mechanical stress may change the magnetic domain structure of the nanocrystalline material, resulting in unexpected increase of coercivity, which is called stress-induced magnetic property degradation. Stress sometimes shows irreversible effects on the magnetic properties of the material, so it is necessary to improve the measurement and monitoring method of the current transformer to effectively evaluate the influence of stress on coercivity, thereby improving the long-term stability and measurement accuracy of the current transformer. SUMMARY

[0004] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present application provide a current transformer measurement method, which can timely judge and respond to high stress state by monitoring the external mechanical stress density and core magnetic permeability reduction rate in real time, so as to solve the problems raised in the above background.

[0005] To achieve the above object, the present application provides the following technical scheme: a current transformer measurement method, comprising:

[0006] Before the measurement of the current transformer starts, the core made of nanocrystalline material of the current transformer is initially magnetized, and reaches a saturated state by a magnetic field;

[0007] An alternating current signal is applied to the primary winding in the current transformer, which generates an alternating magnetic field in the core, causing the magnetic flux in the core to change. When the current transformer senses the change of current, an induced electromotive force is generated through the secondary winding, which represents the measurement value;

[0008] The induced current in the secondary winding changes in a fixed proportional relationship with the induced current in the primary winding, and the induced current is transmitted to a measurement device for collection;

[0009] The current transformer performs error compensation and calibration while outputting the current signal; the current signal after error compensation is converted into a digital signal, and a measurement result is generated through a data processing module;

[0010] Real-time external mechanical stress density data and core magnetic permeability reduction rate data are acquired, and when the external mechanical stress density is greater than a system preset external mechanical stress density threshold and the core magnetic permeability reduction rate is greater than a system preset core magnetic permeability reduction rate threshold, the system judges that the environment is a first-level high stress state, otherwise, it is a normal state;

[0011] In the first-level high stress state, the thermal stress accumulation rate and the core coercive force increase are acquired, and if the thermal stress accumulation rate is greater than a system preset thermal stress accumulation rate threshold and the core coercive force increase is greater than a system preset core coercive force increase threshold, the system judges that the environment is a second-level high stress state, in which a first-level alarm is issued and manual processing is prompted; otherwise, the system enters a detection mode;

[0012] In the detection mode, stress-induced magnetic property degradation information of the current transformer core to be measured is acquired, including stress demagnetization information and thermal stress accumulation information, and a comprehensive evaluation index is generated based on the stress demagnetization information and the thermal stress accumulation information, and when the comprehensive evaluation index exceeds a comprehensive evaluation index threshold, a second-level alarm is issued and manual processing is prompted; otherwise, the system re-judges whether the environment is a first-level high stress state.

[0013] In a preferred embodiment, the external mechanical stress density is monitored in real time, and the external mechanical stress density data is acquired by monitoring, and the external mechanical stress density is set as σ ext The system preset external mechanical stress density threshold is σ th The judgment condition for the external mechanical stress density data is:

[0014] σ ext > σ th

[0015] In the formula, σ ext represents the real-time monitored external mechanical stress density, and σ th is a threshold set by the system according to material and structural characteristics, and when σ ext exceeds the threshold σ th , it indicates that the mechanical stress exceeds the bearing range of the material;

[0016] The core magnetic permeability reduction rate is monitored in real time, and the core magnetic permeability reduction rate data is acquired by monitoring, and the core magnetic permeability reduction rate is set as Δμ r The system preset magnetic permeability reduction rate threshold is Δμ r,th The judgment condition for the magnetic permeability reduction rate data is:

[0017] Δμ r >Δμ r,th

[0018] Where Δμ r It is the rate of decrease of the permeability of the iron core, representing the rate of change of permeability with external stress;

[0019] When the external mechanical stress density σ ext and the rate of decrease in permeability Δμ r When both threshold conditions are met simultaneously, the system will enter a first-level high-stress state. The judgment condition is as follows:

[0020] σ ext >σ th And Δμ r >Δμ r,th

[0021] The first-level high-stress state indicates that both the external mechanical stress density and the rate of decrease in the core permeability exceed the corresponding thresholds preset by the system, and the system will determine that the current environment is a first-level high-stress state.

[0022] In a preferred embodiment, the rate of thermal stress accumulation is monitored, and the rate of thermal stress accumulation is determined to be R. thermal The system's preset thermal stress accumulation rate threshold is R. thermal,th The criterion for determining the rate of thermal stress accumulation is:

[0023] R thermal >R thermal,th

[0024] Where R thermal In a real-time environment, the rate of thermal stress accumulation in the iron core due to temperature changes, if R thermal Greater than the system threshold R thermal,th This indicates that the stress exerted by the temperature on the iron core has reached a level that requires monitoring.

[0025] The increase in coercivity of the iron core was monitored, and the proposed increase in coercivity of the iron core was ΔH. c The system's preset threshold for the increase in coercivity is ΔH. c,th The criterion for judging the increase in core coercivity is:

[0026] ΔH c >ΔH c,th

[0027] Among them, the increase in coercivity ΔH c This refers to the increase in coercivity of the core material due to stress or environmental changes. If the increase in coercivity exceeds the threshold ΔH... c,th This indicates a degradation of the material's magnetic properties;

[0028] When judging the second-order high-stress state, when the thermal stress accumulation rate R thermal and the increase in core coercivity ΔH c Simultaneously, if the preset threshold is exceeded, the system will determine that it has entered a level two high-stress state. The determination condition is as follows:

[0029] R thermal >R thermal,th And ΔH c >ΔH c,th

[0030] When this condition is met, the system will issue a Level 1 alarm and prompt manual intervention.

[0031] In a preferred embodiment, when the system does not meet the judgment conditions for the second-level high-stress state, it enters the detection mode. In the detection mode, the stress-induced magnetic performance degradation information of the current transformer core is obtained, wherein the stress-induced magnetic performance degradation information includes stress demagnetization information and thermal stress accumulation information.

[0032] Stress demagnetization information includes two dimensions, namely the first dimension and the second dimension;

[0033] The first dimension includes the permeability loss rate and the domain reversal rate.

[0034] The proposed permeability loss rate is Used to represent the rate of change of magnetic permeability under mechanical stress; the proposed domain reversal rate is ω. domain ω domain The first dimension I in the stress demagnetization information is used to represent the frequency of domain reversal under stress. stress1 Expressed as:

[0035]

[0036] The function f represents a nonlinear mapping relationship used to describe the interaction between permeability loss and domain reversal rate;

[0037] The second dimension includes the stress-induced hysteresis loop extension and the permeability hysteresis factor.

[0038] Let the hysteresis loop extension be ΔA. hys ΔA hys The permeability hysteresis factor is λ, which represents the change in the area of ​​the hysteresis loop under stress. lag , λ lag The second dimension I of the stress demagnetization information represents the degree of hysteresis in permeability as it expands with the hysteresis loop. stress2 Expressed as:

[0039]

[0040] The function g represents a nonlinear relationship, used to describe the coupling between the hysteresis loop expansion and permeability hysteresis under stress. The comprehensive formula for stress demagnetization information is:

[0041] I demag =h(I stress1 ,I stress2 )

[0042] The h function integrates information from the first and second dimensions to generate a comprehensive index about stress demagnetization.

[0043] In a preferred embodiment, the thermal stress accumulation information includes two dimensions, namely a third dimension and a fourth dimension;

[0044] The third dimension includes thermal stress gradient and magnetic property temperature coefficient;

[0045] The proposed thermal stress gradient is G. thermal G thermal This represents the stress gradient caused by temperature changes; the temperature coefficient of magnetic properties is α. μ (T), α μ (T) represents the sensitivity of magnetic permeability to temperature changes, the third dimension of thermal stress accumulation information I. thermal3 Expressed as:

[0046] I thermal3 =k(G thermal ·α μ (T))

[0047] Where k is a nonlinear function used to describe the combined effect of thermal stress and changes in magnetic properties;

[0048] The second dimension includes the rate of thermal stress accumulation and the rate of change of coercivity.

[0049] The proposed thermal stress accumulation rate is R. thermal The rate of change of coercivity is H c The fourth dimension of thermal stress accumulation information I thermal4 Expressed as:

[0050]

[0051] The function l represents the complexity of the effect of thermal stress on coercivity;

[0052] The comprehensive formula for thermal stress accumulation information is:

[0053] I thermal =m(I thermal3 ,I thermal4 )

[0054] The m-function combines the third and fourth dimensions of thermal stress accumulation information to generate a thermal stress information index.

[0055] In a preferred embodiment, based on stress demagnetization information I demag and thermal stress accumulation information I thermal A comprehensive evaluation index is generated jointly. The formula for the comprehensive evaluation index is:

[0056] I total =n(I demag ,I thermal )

[0057] Where n is a nonlinear mapping function used to integrate the effects of stress demagnetization and thermal stress accumulation, and the comprehensive evaluation index is used to determine the current stress state. total Exceeding the system's preset threshold I total,th At that time, the system issued a level-two alarm;

[0058]

[0059] When the comprehensive evaluation index I total When the threshold is exceeded, it indicates that the stress state has reached a dangerous level on the core, so a level two alarm is issued and manual intervention is requested.

[0060] The technical effects and advantages of this invention are as follows:

[0061] 1. By monitoring the external mechanical stress density and the rate of decrease in core permeability in real time, the system can promptly identify and respond to high stress conditions, ensuring the working stability and measurement accuracy of the current transformer under high stress conditions.

[0062] 2. Through error compensation and calibration, measurement errors caused by environmental changes or changes in the properties of the core material are automatically corrected, ensuring the accuracy of the output signal;

[0063] 3. The analysis of stress-induced magnetic performance degradation information in the detection mode enables the system to identify the degradation trend of the core magnetic performance in advance and generate a comprehensive evaluation index. This early warning mechanism reduces the possibility of equipment failure through early intervention and improves the service life and safety of the current transformer.

[0064] 4. Through graded high-stress condition judgment and automatic alarm mechanism, different response measures can be taken under different stress levels to avoid excessive damage to the equipment and ensure the efficient operation of the equipment in complex power systems. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0066] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] Refer to the instruction manual appendix Figure 1 An embodiment of the present invention provides a current transformer measurement method, comprising:

[0068] Before the measurement of the current transformer begins, the iron core made of nanocrystalline material of the current transformer is initially magnetized or pretreated, and saturated by a stable magnetic field. This step is used to ensure that the magnetic domains in the iron core are fully aligned, thereby providing consistent starting conditions for subsequent measurements. Common pretreatments also include annealing to reduce the effects of stress and residual magnetism.

[0069] In a current transformer, a known alternating current signal is applied through the primary winding. This alternating current generates an alternating magnetic field in the iron core, causing a change in the magnetic flux within the iron core. When the current transformer senses the change in current, it generates an induced electromotive force through the secondary winding, which is reflected in the measured value. The primary winding is the part directly connected to the current in the main circuit and usually carries a large current. The main function of the primary winding is to generate a magnetic field, which changes with the current, thereby inducing a change in the magnetic flux in the iron core. The secondary winding works by inducing current. It does not directly carry the current in the main circuit, but rather senses the change in the magnetic field generated by the primary winding. Due to the design of the current transformer, the induced current in the secondary winding is proportional to the current in the primary winding, and the magnitude of the current is usually greatly reduced to a range suitable for measurement and analysis. This reduction ratio is determined by the turns ratio of the primary winding to the secondary winding. In short, the primary winding is responsible for transmitting the main current, while the secondary winding generates a measurable small current proportional to the main current by inducing the change in the magnetic field of the current.

[0070] The induced current in the secondary winding changes in a fixed proportional relationship with the induced current in the primary winding. This induced current is transmitted to a measuring device for acquisition. Typically, the current in the secondary winding is smaller, and its magnitude maintains a strictly linear correspondence with the current in the primary winding through the turns ratio of the current transformer. This proportional relationship ensures that the current transformer can effectively convert the large current in the main circuit into a small current suitable for measurement, ensuring the accuracy and reliability of the measurement. Based on the acquired secondary current signal, the measuring device generates a measurement output proportional to the primary current for further processing or display.

[0071] While outputting the current signal, the current transformer undergoes error compensation and calibration. The current signal after error compensation is converted into a digital signal, and the measurement result is generated by the data processing module. Due to the characteristics of the core material, such as hysteresis loss and eddy current loss, measurement errors may occur. Therefore, it is necessary to introduce an error correction algorithm or device to correct the output result and ensure the accuracy of the measurement. The calibration process also includes compensating for errors caused by ambient temperature or mechanical stress. The processed data can be transmitted to the monitoring system through a display device or transmission system for real-time monitoring or recording of current changes. Digital processing can also effectively improve the data sampling rate and accuracy, especially in high-frequency applications.

[0072] The system acquires external mechanical stress density data and core permeability reduction rate data in real time. When the external mechanical stress density is greater than the system's preset external mechanical stress density threshold and the core permeability reduction rate is greater than the system's preset core permeability reduction rate threshold, the system judges the environment as a first-level high-stress state; otherwise, it is a normal state.

[0073] Under the first-level high stress state, the thermal stress accumulation rate and the increase in core coercivity are obtained. If the thermal stress accumulation rate is greater than the system's preset thermal stress accumulation rate threshold and the increase in core coercivity is greater than the system's preset core coercivity increase threshold, the system judges the environment as a second-level high stress state. Under the second-level high stress state, the system issues a first-level alarm and prompts manual handling; otherwise, it enters the detection mode.

[0074] In the detection mode, the stress-induced magnetic performance degradation information of the current transformer core to be measured is obtained. The stress-induced magnetic performance degradation information includes stress demagnetization information and thermal stress accumulation information. A comprehensive evaluation index is generated based on the stress demagnetization information and thermal stress accumulation information. When the comprehensive evaluation index exceeds the comprehensive evaluation index threshold, a level two alarm is issued and manual handling is prompted; otherwise, the system re-determines whether the environment is a level one high stress state.

[0075] Real-time monitoring of external mechanical stress density is performed. External mechanical stress density data is obtained through monitoring, and the external mechanical stress density is defined as σ. ext The system's preset external mechanical stress density threshold is σ th The criteria for judging external mechanical stress density data are:

[0076] σ ext >σ th

[0077] σ in the formula ext σ represents the real-time monitored external mechanical stress density. th This is a threshold set by the system based on material and structural properties, when σ ext Exceeding the threshold σth When the mechanical stress exceeds the material's tolerance, it may lead to degradation of the material's magnetic properties.

[0078] The rate of decrease in the permeability of the iron core is monitored in real time. By monitoring the data on the rate of decrease in the permeability of the iron core, the rate of decrease in the permeability of the iron core is determined to be Δμ. r The system's preset threshold for the rate of decrease in permeability is Δμ r,th The criteria for judging the rate of decrease in magnetic permeability are as follows:

[0079] Δμ r >Δμ r,th

[0080] Where Δμ r It is the rate of decrease in the permeability of the iron core, representing the rate at which the permeability changes with external stress or other factors; if Δμ r Exceeding the preset threshold Δμ r,th This indicates that the magnetic properties of the iron core have degraded to a degree that cannot be ignored;

[0081] When the external mechanical stress density σ ext and the rate of decrease in permeability Δμ r When both threshold conditions are met simultaneously, the system will enter a first-level high-stress state. The judgment condition is as follows:

[0082] σ ext >σ th And Δμ r >Δμ r,th

[0083] The first-level high-stress state indicates that both the external mechanical stress density and the rate of decrease in the core permeability exceed the corresponding thresholds preset by the system, and the system will determine that the current environment is a first-level high-stress state.

[0084] The rate of thermal stress accumulation is monitored, and the proposed rate of thermal stress accumulation is R. thermal The system's preset thermal stress accumulation rate threshold is R. thermal,th The criterion for determining the rate of thermal stress accumulation is:

[0085] R thermal >R thermal,th

[0086] Where R thermal In a real-time environment, the rate of thermal stress accumulation in the iron core due to temperature changes, if R thermal Greater than the system threshold R thermal,th This indicates that the stress exerted by the temperature on the iron core has reached a level that requires monitoring.

[0087] The increase in coercivity of the iron core was monitored, and the proposed increase in coercivity of the iron core was ΔH. cThe system's preset threshold for the increase in coercivity is ΔH. c,th The criterion for judging the increase in core coercivity is:

[0088] ΔH c >ΔH c,th

[0089] Among them, the increase in coercivity ΔH c This refers to a significant increase in the coercivity of the core material due to stress or environmental changes. If the increase in coercivity exceeds the threshold ΔH... c,th This indicates that the magnetic properties of the material have degraded, which may affect the measurement accuracy of the current transformer.

[0090] When judging the second-order high-stress state, when the thermal stress accumulation rate R thermal and the increase in core coercivity ΔH c Simultaneously, if the preset threshold is exceeded, the system will determine that it has entered a level two high-stress state. The determination condition is as follows:

[0091] R thermal >R thermal,th And ΔH c >ΔH c,th

[0092] A Level 2 high-stress state means that the system is in a dangerous state and may require manual intervention or protective measures. When this condition is met, the system will issue a Level 1 alarm and prompt manual handling. Through these formulas, the system can judge the stress state in real time and enter the high-stress level according to different stress parameters, thereby ensuring the safe operation of the equipment.

[0093] When the system does not meet the judgment conditions of the second-level high stress state, it enters the detection mode. In the detection mode, the stress-induced magnetic performance degradation information of the current transformer core is obtained. The stress-induced magnetic performance degradation information includes stress demagnetization information and thermal stress accumulation information.

[0094] Stress demagnetization information includes two dimensions, namely the first dimension and the second dimension;

[0095] The first dimension includes the permeability loss rate and the domain reversal rate.

[0096] The proposed permeability loss rate is Δμ r stress , Δμ r stress Used to represent the rate of change of magnetic permeability under mechanical stress; the proposed domain reversal rate is ω. domain ω domain The first dimension I in the stress demagnetization information is used to represent the frequency of domain reversal under stress. stress1 Expressed as:

[0097]

[0098] The function f represents a nonlinear mapping relationship used to describe the interaction between permeability loss and domain reversal rate. This formula shows that the faster the permeability decreases and the higher the domain reversal rate, the stronger the demagnetization effect.

[0099] The second dimension includes the stress-induced hysteresis loop extension and the permeability hysteresis factor.

[0100] Let the hysteresis loop extension be ΔA. hys ΔA hys The permeability hysteresis factor is λ, which represents the change in the area of ​​the hysteresis loop under stress. lag , λ lag The second dimension I of the stress demagnetization information represents the degree of hysteresis in permeability as it expands with the hysteresis loop. stress2 Expressed as:

[0101]

[0102] The function g represents a nonlinear relationship, used to describe the coupling between the hysteresis loop expansion and permeability hysteresis under stress. The comprehensive formula for stress demagnetization information is:

[0103] I demag =h(I stress1 ,I stress2 )

[0104] The h function integrates information from the first and second dimensions to generate a comprehensive index about stress demagnetization.

[0105] The thermal stress accumulation information includes two dimensions, namely the third dimension and the fourth dimension;

[0106] The third dimension includes thermal stress gradient and magnetic property temperature coefficient;

[0107] The proposed thermal stress gradient is G. thermal G thermal This represents the stress gradient caused by temperature changes; the temperature coefficient of magnetic properties is α. μ (T), α μ (T) represents the sensitivity of magnetic permeability to temperature changes, the third dimension of thermal stress accumulation information I. thermal3 Expressed as:

[0108] I thermal3 =k(G thermal ·α μ (T))

[0109] Where k is a nonlinear function used to describe the combined effect of thermal stress and changes in magnetic properties;

[0110] The second dimension includes the rate of thermal stress accumulation and the rate of change of coercivity.

[0111] The proposed thermal stress accumulation rate is R. thermal The rate of change of coercivity is H c The fourth dimension of thermal stress accumulation information I thermal4 Expressed as:

[0112]

[0113] The function l represents the complexity of the effect of thermal stress on coercivity. The faster the thermal stress accumulates, the more significant the change in coercivity, and the greater the magnetic performance degradation the system may face.

[0114] The comprehensive formula for thermal stress accumulation information is:

[0115] I thermal =m(I thermal3 ,I thermal4 )

[0116] The m-function combines the third and fourth dimensions of thermal stress accumulation information to generate a thermal stress information index.

[0117] Based on stress demagnetization information I demag and thermal stress accumulation information I thermal A comprehensive evaluation index is generated jointly. The formula for the comprehensive evaluation index is:

[0118] I total =n(I demag ,I thermal )

[0119] Where n is a nonlinear mapping function used to integrate the effects of stress demagnetization and thermal stress accumulation, and the comprehensive evaluation index is used to determine the current stress state. total Exceeding the system's preset threshold I total,th At that time, the system issued a level-two alarm;

[0120]

[0121] When the comprehensive evaluation index I total When the threshold is exceeded, it indicates that the stress state has reached a dangerous level on the core, so a level two alarm is issued and manual intervention is requested.

[0122] It is important to note that the initial magnetization and saturation processes are crucial. The initial magnetization of the current transformer core is to ensure that the magnetic domains are in a consistent state before the measurement begins. Due to their small grain size and excellent magnetic properties, nanocrystalline materials can quickly reach saturation through a magnetic field, thus avoiding the influence of residual magnetic flux or local hysteresis in the core on subsequent measurements. The pretreatment process usually includes annealing to eliminate residual stress, which may cause magnetic domain disorder and affect accuracy. This initial magnetization and pretreatment process lays a stable foundation for subsequent current measurements. In addition, in terms of material selection, nanocrystalline materials have higher permeability, lower eddy current loss and coercivity than traditional silicon steel. These characteristics make them perform well in high-frequency applications and better maintain the stability of magnetic properties.

[0123] Next, the current conduction and induction process of the primary and secondary windings is the core part of the current transformer measurement. The primary winding transmits the current in the main circuit, while the secondary winding measures and monitors the small current generated by inducing the main current. The turns ratio in the design ensures that the change of the primary current can be sensed by the secondary winding in a precise proportion. This proportional relationship needs to be very strict to avoid introducing errors during transmission. In practical applications, this proportion can be achieved by adjusting the turns ratio, but the control of eddy current loss and the management of core saturation effect must be considered, especially under high current conditions. These issues are crucial to the accuracy of the measurement.

[0124] Subsequently, error compensation and calibration further ensure the accuracy of the measurement. During operation, especially under high stress, current transformers are affected by external environments such as temperature and mechanical stress, which can cause subtle changes in the magnetic properties of the iron core, thus affecting the induced electromotive force and the final measurement results. Therefore, the system must perform real-time error compensation and calibration. This process includes correcting for magnetic domain disturbances caused by temperature changes and mechanical vibrations, ensuring that the transformer's measurement data remains reliable even under harsh conditions. The choice of error compensation algorithm can be based on the actual application scenario. In high-frequency and high-voltage applications, the eddy current effect and hysteresis loss of the iron core must be considered, as these factors will directly affect the accuracy of the data.

[0125] The iron core of a current transformer is affected by external mechanical stress and temperature, which may cause the gradual degradation of its magnetic properties. To address this, the system is designed with a function to monitor the mechanical stress density and the rate of decrease in permeability in real time, ensuring a timely response when the stress exceeds a preset threshold. Under first-level high stress conditions, the system will further acquire the thermal stress accumulation rate and the increase in the coercivity of the iron core. This design aims to predict and detect potential problems in advance, especially under high stress conditions, to prevent measurement distortion caused by a sharp increase in coercivity. In addition, these thresholds are based on the stress-magnetic curve of the iron core material, which has been experimentally determined and optimized, ensuring wide applicability under different working conditions.

[0126] The evaluation of detection modes and stress degradation information further enhances the intelligent monitoring of the system. When the system has not reached the second-level high stress state, it enters the detection mode to acquire stress demagnetization information and thermal stress accumulation information. The stress demagnetization information reflects how mechanical stress affects the magnetic properties of the iron core by analyzing the permeability loss rate and magnetic domain reversal rate. The thermal stress accumulation information mainly evaluates the changes in stress gradient and magnetic temperature coefficient caused by temperature changes. These two parts of information interact to generate a comprehensive evaluation index to determine whether a higher stress state has been entered. This not only provides real-time feedback on the equipment status but also provides early warning of potential problems. In practical applications, this method can be used to correct measurement data under different stress conditions through multiple experiments to ensure accurate stress assessment in various environments.

[0127] Finally, the design of the secondary high-stress state and system alarm further improves the intelligent measurement function of the instrument transformer. By monitoring the comprehensive evaluation index, when the index exceeds the set safety threshold, the system will issue a secondary alarm and prompt manual intervention. This alarm not only protects the equipment from further damage, but also reminds operators to deal with potential risks in a timely manner, thereby extending the equipment life. For example, in the application of high-voltage transmission lines, if stress-induced magnetic degradation is detected, timely manual intervention can prevent serious accidents. In addition, the system design can include a redundant judgment mechanism to ensure that the alarm is triggered only when multiple stress parameters reach the critical value at the same time, thereby avoiding false alarms.

[0128] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for measuring current transformers, characterized in that, include: Before the measurement of the current transformer begins, the iron core of the current transformer, made of nanocrystalline material, is initially magnetized and saturated by a magnetic field. In a current transformer, a known alternating current signal is applied through the primary winding. This alternating current generates an alternating magnetic field in the iron core, causing a change in the magnetic flux within the iron core. When the current transformer senses the change in current, it generates an induced electromotive force through the secondary winding, which reflects the measured value. The induced current in the secondary winding changes with the induced current in the primary winding in a fixed proportional relationship, and the induced current is transmitted to the measuring device for acquisition. While outputting the current signal, the current transformer performs error compensation and calibration; the current signal after error compensation is converted into a digital signal, and the measurement result is generated by the data processing module. The system acquires external mechanical stress density data and core permeability reduction rate data in real time. When the external mechanical stress density is greater than the system's preset external mechanical stress density threshold and the core permeability reduction rate is greater than the system's preset core permeability reduction rate threshold, the system judges the environment as a first-level high-stress state; otherwise, it is a normal state. Under the first-level high stress state, the thermal stress accumulation rate and the increase in core coercivity are obtained. If the thermal stress accumulation rate is greater than the system's preset thermal stress accumulation rate threshold and the increase in core coercivity is greater than the system's preset core coercivity increase threshold, the system judges the environment as a second-level high stress state. Under the second-level high stress state, the system issues a first-level alarm and prompts manual handling. Otherwise, enter detection mode; In the detection mode, the stress-induced magnetic performance degradation information of the current transformer core to be measured is obtained. The stress-induced magnetic performance degradation information includes stress demagnetization information and thermal stress accumulation information. A comprehensive evaluation index is generated based on the stress demagnetization information and thermal stress accumulation information. When the comprehensive evaluation index exceeds the comprehensive evaluation index threshold, a level two alarm is issued and manual handling is prompted; otherwise, the system re-determines whether the environment is a level one high stress state.

2. The current transformer measurement method according to claim 1, characterized in that: Real-time monitoring of external mechanical stress density is performed. External mechanical stress density data is obtained through monitoring, and the external mechanical stress density is defined as σ. ext The system's preset external mechanical stress density threshold is σ th The criteria for judging external mechanical stress density data are: s ext >s th σ in the formula ext σ represents the real-time monitored external mechanical stress density. th This is a threshold set by the system based on material and structural properties, when σ ext Exceeding the threshold σ th When this occurs, it indicates that the mechanical stress exceeds the material's tolerance range; The rate of decrease in the permeability of the iron core is monitored in real time. By monitoring the data on the rate of decrease in the permeability of the iron core, the rate of decrease in the permeability of the iron core is determined to be Δμ. r The system's preset threshold for the rate of decrease in permeability is Δμ r,th The criteria for judging the rate of decrease in magnetic permeability are as follows: Dm r >Dm r,th Where Δμ r It is the rate of decrease of the permeability of the iron core, representing the rate of change of permeability with external stress; When the external mechanical stress density σ ext and the rate of decrease in permeability Δμ r When both threshold conditions are met simultaneously, the system will enter a first-level high-stress state. The judgment condition is as follows: s ext >s th AndDm r >Dm r,th The first-level high-stress state indicates that both the external mechanical stress density and the rate of decrease in the core permeability exceed the corresponding thresholds preset by the system, and the system will determine that the current environment is a first-level high-stress state.

3. The current transformer measurement method according to claim 2, characterized in that: The rate of thermal stress accumulation is monitored, and the proposed rate of thermal stress accumulation is R. thermal The system's preset thermal stress accumulation rate threshold is R. thermal,th The criterion for determining the rate of thermal stress accumulation is: R thermal >R thermal,th Where R thermal In a real-time environment, the rate of thermal stress accumulation in the iron core due to temperature changes, if R thermal Greater than the system threshold R thermal,th This indicates that the stress exerted by the temperature on the iron core has reached a level that requires monitoring. The increase in coercivity of the iron core was monitored, and the proposed increase in coercivity of the iron core was ΔH. c The system's preset threshold for the increase in coercivity is ΔH. c,th The criterion for judging the increase in core coercivity is: ΔH c >ΔH c,th Among them, the increase in coercivity ΔH c This refers to the increase in coercivity of the core material due to stress or environmental changes. If the increase in coercivity exceeds the threshold ΔH... c,th This indicates a degradation of the material's magnetic properties; When judging the second-order high-stress state, when the thermal stress accumulation rate R thermal and the increase in core coercivity ΔH c Simultaneously, if the preset threshold is exceeded, the system will determine that it has entered a level two high-stress state. The determination condition is as follows: R thermal >R thermal,th and ΔH c >ΔH c,th When this condition is met, the system will issue a Level 1 alarm and prompt manual intervention.

4. The current transformer measurement method according to claim 3, characterized in that: When the system does not meet the judgment conditions of the second-level high stress state, it enters the detection mode. In the detection mode, the stress-induced magnetic performance degradation information of the current transformer core is obtained. The stress-induced magnetic performance degradation information includes stress demagnetization information and thermal stress accumulation information. Stress demagnetization information includes two dimensions, namely the first dimension and the second dimension; The first dimension includes the permeability loss rate and the domain reversal rate. The proposed permeability loss rate is Used to represent the rate of change of magnetic permeability under mechanical stress; the proposed domain reversal rate is ω. domain ω domain The first dimension I in the stress demagnetization information is used to represent the frequency of domain reversal under stress. stress1 Expressed as: The function f represents a nonlinear mapping relationship used to describe the interaction between permeability loss and domain reversal rate; The second dimension includes the stress-induced hysteresis loop extension and the permeability hysteresis factor. Let the hysteresis loop extension be ΔA. hys ΔA hys The permeability hysteresis factor is λ, which represents the change in the area of ​​the hysteresis loop under stress. lag , λ lag The second dimension I of the stress demagnetization information represents the degree of hysteresis in permeability as it expands with the hysteresis loop. stress2 Expressed as: The function g represents a nonlinear relationship, used to describe the coupling between the hysteresis loop expansion and permeability hysteresis under stress. The comprehensive formula for stress demagnetization information is: I demag =h(I stress1 ,I stress2 ) The h function integrates information from the first and second dimensions to generate a comprehensive index about stress demagnetization.

5. The current transformer measurement method according to claim 4, characterized in that: The thermal stress accumulation information includes two dimensions, namely the third dimension and the fourth dimension; The third dimension includes thermal stress gradient and magnetic property temperature coefficient; The proposed thermal stress gradient is G. thermal G thermal This represents the stress gradient caused by temperature changes; the temperature coefficient of magnetic properties is α. μ (T), α μ (T) represents the sensitivity of magnetic permeability to temperature changes, the third dimension of thermal stress accumulation information I. thermal3 Expressed as: I thermal3 =k(G thermal ·α μ (T)) Where k is a nonlinear function used to describe the combined effect of thermal stress and changes in magnetic properties; The second dimension includes the rate of thermal stress accumulation and the rate of change of coercivity. The proposed thermal stress accumulation rate is R. thermal The rate of change of coercivity is The fourth dimension I of thermal stress accumulation information thermal4 Expressed as: The function l represents the complexity of the effect of thermal stress on coercivity; The comprehensive formula for thermal stress accumulation information is: I thermal =m(I thermal3 ,I thermal4 ) The m-function combines the third and fourth dimensions of thermal stress accumulation information to generate a thermal stress information index.

6. The current transformer measurement method according to claim 5, characterized in that: Based on stress demagnetization information I demag and thermal stress accumulation information I thermal A comprehensive evaluation index is generated jointly. The formula for the comprehensive evaluation index is: I total =n(I demag ,I thermal ) Where n is a nonlinear mapping function used to integrate the effects of stress demagnetization and thermal stress accumulation, and the comprehensive evaluation index is used to determine the current stress state. total Exceeding the system's preset threshold I total,th At that time, the system issued a level-two alarm; When the comprehensive evaluation index I total When the threshold is exceeded, it indicates that the stress state has reached a dangerous level on the core, so a level two alarm is issued and manual intervention is requested.

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