Current transformer measurement method

Abstract

The invention discloses a current transformer measurement method, and particularly relates to the field of current transformer monitoring and measurement, which comprises the following steps of: before the measurement of a current transformer is started, carrying out initial magnetization on an iron core made of a nanocrystalline material of the current transformer, and enabling the iron core to reach a saturated state through a magnetic field; a known alternating current signal is applied in the current transformer through a primary winding, the alternating current generates an alternating magnetic field in an iron core to change the magnetic flux in the iron core, and after the current transformer senses the change of the current, induced electromotive force is generated through a secondary winding to reflect a measured value; the induced current in the secondary winding and the induced current in the primary winding change according to a fixed proportional relation, and the induced current is transmitted to a measuring device to be collected. By monitoring the external mechanical stress density and the iron core magnetic conductivity decline rate in real time, the system can judge and respond to the high stress state in time, and the working stability and the measurement precision of the current transformer under the high stress condition are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of current transformer monitoring and measurement, and more specifically, to a current transformer measurement method. Background Art

[0002] A current transformer is a device used to convert high current into a smaller current for use in measuring instruments or protection devices. It induces a large current through the primary winding, generates a magnetic field in the iron core, and then induces a small current proportional to the primary current in the secondary winding. The iron core of the current transformer can be made of nanocrystalline material, which has high magnetic permeability, low loss, low coercivity and high saturation magnetic induction intensity. It can significantly improve measurement accuracy and efficiency in high-frequency and high-current environments, reduce the degradation of the iron core under high stress conditions, and thus improve the long-term stability and working reliability of the transformer;

[0003] During the manufacturing or installation process of the current transformer, the nanocrystalline material core may be affected by mechanical stress, such as excessive extrusion, improper fixation, etc. Mechanical stress may change the magnetic domain structure of the nanocrystalline material, resulting in an unexpected increase in coercivity. This phenomenon is called stress-induced magnetic property degradation. Stress sometimes has irreversible effects on the magnetic properties of the material. Therefore, it is necessary to improve the measurement and monitoring methods of the current transformer to effectively evaluate the impact of stress on coercivity, thereby improving the long-term stability and measurement accuracy of the current transformer. Summary of the invention

[0004] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a current transformer measurement method. By real-time monitoring of the external mechanical stress density and the core magnetic permeability decrease rate, the system can timely judge and respond to high stress states to solve the problems raised in the above-mentioned background technology.

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

[0006] Before the measurement of the current transformer begins, the iron core made of nanocrystalline material of the current transformer is initially magnetized and brought into a saturation state by a magnetic field;

[0007] In the current transformer, a known AC current signal is applied through the primary winding. The AC current generates an alternating magnetic field in the iron core, causing the magnetic flux in the iron core to change. When the current transformer senses the change in current, an induced electromotive force is generated through the secondary winding, which reflects the measured 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 the measuring device for collection;

[0009] 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 through the data processing module;

[0010] Acquire external mechanical stress density data and core magnetic permeability reduction rate data in real time. When the external mechanical stress density is greater than the external mechanical stress density threshold preset by the system and the core magnetic permeability reduction rate is greater than the core magnetic permeability reduction rate threshold preset by the system, the system determines the environment as 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 increase in the coercive force of the core are obtained. If the thermal stress accumulation rate is greater than the thermal stress accumulation rate threshold preset by the system and the increase in the coercive force of the core is greater than the coercive force increase threshold preset by the system, the system determines the environment as a second-level high stress state. In the second-level high stress state, the system issues a first-level alarm and prompts manual processing; otherwise, it enters the detection mode;

[0012] In the detection mode, the stress-induced magnetic performance degradation information of the current transformer core to be measured is obtained, and 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 the thermal stress accumulation information. When the comprehensive evaluation index exceeds the comprehensive evaluation index threshold, a secondary alarm is issued and manual processing is prompted; otherwise, the system re-judges whether the environment is a primary 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 obtained by monitoring, and the external mechanical stress density is proposed to be σ ext , the preset external mechanical stress density threshold of the system is σ th , the judgment conditions for external mechanical stress density data are:

[0014] σ ext >σ th

[0015] σ in the formula ext represents the external mechanical stress density monitored in real time, σ th is the threshold set by the system according to the material and structural characteristics. ext Exceeding the threshold σ th When , it means that the mechanical stress exceeds the bearing range of the material;

[0016] The core magnetic permeability decrease rate is monitored in real time. By monitoring the core magnetic permeability decrease rate data, the core magnetic permeability decrease rate is proposed to be Δμ r , the system preset magnetic permeability decrease rate threshold is Δμ r,th , the judgment conditions for the magnetic permeability reduction rate data are:

[0017] Δμ r >Δμ r,th

[0018] where Δμ r is the rate of decrease of the magnetic permeability of the core, which indicates the rate of change of magnetic permeability with external stress;

[0019] When the external mechanical stress density σ ext and the magnetic permeability decrease rate Δμ r When the respective threshold conditions are met at the same time, the system will enter the first-level high stress state. The judgment conditions are:

[0020] σ ext >σ th And Δμ r >Δμ r,th

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

[0022] In a preferred embodiment, the thermal stress accumulation rate is monitored and the thermal stress accumulation rate is set to R thermal The system preset thermal stress accumulation rate threshold is R thermal,th , the judgment condition of thermal stress accumulation rate is:

[0023] R thermal >R thermal,th

[0024] Where R thermal is the rate of thermal stress accumulation in the core due to temperature changes in a real-time environment. If R thermal Greater than the system threshold R thermal,th , indicating that the stress caused by temperature on the core has reached a level that requires monitoring;

[0025] Monitor the increase in the coercive force of the core and set the increase in the coercive force of the core to ΔH c , the system preset threshold value of coercive force increase is ΔH c,th , the judgment condition for the increase in the coercive force of the core is:

[0026] ΔH c >ΔH c,th

[0027] The coercivity increase ΔH c It means that due to stress or environmental changes, the coercivity of the core material increases. If the coercivity increase exceeds the threshold ΔH c,th , indicating that the magnetic properties of the material are degraded;

[0028] When judging the secondary high stress state, when the thermal stress accumulation rate R thermal and the increase in core coercivity ΔH c When the preset threshold is exceeded at the same time, the system will judge that it has entered the secondary high stress state. The judgment conditions are:

[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 processing.

[0031] In a preferred embodiment, when the system does not meet the judgment condition of the secondary high stress state, it enters the detection mode, in which the stress-induced magnetic performance degradation information of the iron core of the current transformer is obtained, wherein the stress-induced magnetic performance degradation information includes stress demagnetization information and thermal stress accumulation information;

[0032] The 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 magnetic domain reversal rate;

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

[0035]

[0036] The function f is expressed as a nonlinear mapping relationship, which is used to describe the interaction between the permeability loss and the magnetic domain reversal rate;

[0037] The second dimension includes the expansion of the hysteresis loop and the hysteresis factor of the magnetic permeability caused by stress;

[0038] Assume that the expansion of the hysteresis loop is ΔA hys , ΔA hys It represents the area change of the hysteresis loop under stress, and the proposed permeability hysteresis factor is λ lag ,λ lag The second dimension of stress demagnetization information is I, which represents the hysteresis degree of the magnetic permeability as the hysteresis loop expands. stress2 Expressed as:

[0039]

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

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

[0042] Among them, the h function integrates the information of the first dimension and the second dimension to generate a comprehensive index about stress demagnetization.

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

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

[0045] The thermal stress gradient is assumed to be G thermal , G thermal Represents the stress gradient caused by temperature change; 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 effects of thermal stress and magnetic property changes;

[0048] The second dimension includes the thermal stress accumulation rate and the coercive force change rate;

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

[0050]

[0051] 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 dimension information of thermal stress accumulation information to generate a thermal stress information index.

[0055] In a preferred embodiment, based on the stress demagnetization information I demag and thermal stress accumulation information I thermal The comprehensive evaluation index is jointly generated. The formula of 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. The comprehensive evaluation index is used to judge the current stress state. total Exceeds the system preset threshold I total,th When the system issues a level 2 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 secondary alarm is issued and manual processing is prompted.

[0060] Technical effects and advantages of the present invention:

[0061] 1. By real-time monitoring of external mechanical stress density and core magnetic permeability drop rate, the system can timely judge and respond to high stress state, ensuring the working stability and measurement accuracy of the current transformer under high stress conditions;

[0062] 2. Through error compensation and calibration, it is helpful to automatically correct the measurement error caused by environmental changes or changes in core material properties, 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 state 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0066] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0067] Refer to the instruction manual Figure 1 , a current transformer measurement method according to an embodiment of the present invention comprises:

[0068] Before the measurement of the current transformer begins, the core made of nanocrystalline material of the current transformer is initially magnetized or pre-treated, and a stable magnetic field is used to make it reach saturation. This step is used to ensure that the magnetic domains in the core are fully arranged, thereby providing consistent starting conditions for subsequent measurements. Common pre-treatment also includes annealing to reduce stress and residual magnetic effects.

[0069] In the current transformer, a known AC current signal is applied through the primary winding. The AC current generates an alternating magnetic field in the iron core, causing the magnetic flux in the iron core to change. 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 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 when the current changes, thereby causing a change in the magnetic flux in the iron core. The secondary winding works by inducing current. It does not directly carry the current of the main circuit, but 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 current size 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, and the secondary winding generates a measurable small current proportional to the main current by sensing the change in the magnetic field of the current.

[0070] 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 collection; usually the current in the secondary winding is small, and its magnitude is strictly linearly corresponding to the turns ratio of the primary winding current through the 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 collected 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 performs error compensation and calibration; the current signal after error compensation is converted into a digital signal, and the measurement result is generated through the data processing module; among them, due to the characteristics of the core material, such as hysteresis loss, eddy current loss, etc., measurement errors may occur, so it is necessary to introduce an error correction algorithm or device to correct the output result to ensure the accuracy of the measurement. The calibration process also includes compensation for errors caused by ambient temperature or mechanical stress; the processed data can be transmitted to the monitoring system through a display device or a transmission system for real-time monitoring or recording of current changes. Digital processing can also effectively improve the sampling rate and accuracy of the data, especially in high-frequency applications;

[0072] Acquire external mechanical stress density data and core magnetic permeability reduction rate data in real time. When the external mechanical stress density is greater than the external mechanical stress density threshold preset by the system and the core magnetic permeability reduction rate is greater than the core magnetic permeability reduction rate threshold preset by the system, the system determines the environment as a first-level high stress state, otherwise it is a normal state.

[0073] In the first-level high stress state, the thermal stress accumulation rate and the increase in the coercive force of the core are obtained. If the thermal stress accumulation rate is greater than the thermal stress accumulation rate threshold preset by the system and the increase in the coercive force of the core is greater than the coercive force increase threshold preset by the system, the system determines the environment as a second-level high stress state. In the second-level high stress state, the system issues a first-level alarm and prompts manual processing; 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, and 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 the thermal stress accumulation information. When the comprehensive evaluation index exceeds the comprehensive evaluation index threshold, a secondary alarm is issued and manual processing is prompted; otherwise, the system re-judges whether the environment is a primary high stress state.

[0075] The external mechanical stress density is monitored in real time, and the external mechanical stress density data is obtained through monitoring. The external mechanical stress density is proposed to be σ ext , the preset external mechanical stress density threshold of the system is σ th , the judgment conditions for external mechanical stress density data are:

[0076] σ ext >σ th

[0077] σ in the formula ext represents the external mechanical stress density monitored in real time, σ th is the threshold set by the system according to the material and structural characteristics. ext Exceeding the threshold σth When the mechanical stress exceeds the material's tolerance, it may cause the material's magnetic properties to deteriorate;

[0078] The core magnetic permeability decrease rate is monitored in real time. By monitoring the core magnetic permeability decrease rate data, the core magnetic permeability decrease rate is proposed to be Δμ r , the system preset magnetic permeability decrease rate threshold is Δμ r,th , the judgment conditions for the magnetic permeability reduction rate data are:

[0079] Δμ r >Δμ r,th

[0080] where Δμ r is the rate of decrease of the magnetic permeability of the core, indicating the rate of change of magnetic permeability with external stress or other factors; if Δμ r Exceeds the preset threshold Δμ r,th , indicating that the magnetic performance degradation of the core has reached a level that cannot be ignored;

[0081] When the external mechanical stress density σ ext and the magnetic permeability decrease rate Δμ r When the respective threshold conditions are met at the same time, the system will enter the first-level high stress state. The judgment conditions are:

[0082] σ ext >σ th And Δμ r >Δμ r,th

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

[0084] The thermal stress accumulation rate is monitored and the thermal stress accumulation rate is proposed to be R thermal The system preset thermal stress accumulation rate threshold is R thermal,th , the judgment condition of thermal stress accumulation rate is:

[0085] R thermal >R thermal,th

[0086] Where R thermal is the rate of thermal stress accumulation in the core due to temperature changes in a real-time environment. If R thermal Greater than the system threshold R thermal,th , indicating that the stress caused by temperature on the core has reached a level that requires monitoring;

[0087] Monitor the increase in the coercive force of the core and set the increase in the coercive force of the core to ΔH c, the system preset threshold value of coercive force increase is ΔH c,th , the judgment condition for the increase in the coercive force of the core is:

[0088] ΔH c >ΔH c,th

[0089] The coercivity increase ΔH c It means that due to stress or environmental changes, the coercivity of the core material has increased significantly. If the coercivity increase exceeds the threshold ΔH c,th , indicating that the magnetic properties of the material are degraded, which may affect the measurement accuracy of the current transformer;

[0090] When judging the secondary high stress state, when the thermal stress accumulation rate R thermal and the increase in core coercivity ΔH c When the preset threshold is exceeded at the same time, the system will judge that it has entered the secondary high stress state. The judgment conditions are:

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

[0092] The second-level high stress state means that the system is in a dangerous state and may require human intervention or protective measures. When this condition is met, the system will issue a first-level alarm and prompt manual processing. Through these formulas, the system can judge the stress state in real time and enter a 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 condition of the secondary high stress state, it enters the detection mode, in which the stress-induced magnetic performance degradation information of the iron core of the current transformer is obtained, wherein the stress-induced magnetic performance degradation information includes stress demagnetization information and thermal stress accumulation information;

[0094] The 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 magnetic domain reversal rate;

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

[0097]

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

[0099] The second dimension includes the expansion of the hysteresis loop and the hysteresis factor of the magnetic permeability caused by stress;

[0100] Assume that the expansion of the hysteresis loop is ΔA hys , ΔA hys It represents the area change of the hysteresis loop under stress, and the proposed permeability hysteresis factor is λ lag ,λ lag The second dimension of stress demagnetization information is I, which represents the hysteresis degree of the magnetic permeability as the hysteresis loop expands. stress2 Expressed as:

[0101]

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

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

[0104] Among them, the h function integrates the information of the first dimension and the second dimension 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 thermal stress gradient is assumed to be G thermal , G thermal Represents the stress gradient caused by temperature change; 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 effects of thermal stress and magnetic property changes;

[0110] The second dimension includes the thermal stress accumulation rate and the coercive force change rate;

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

[0112]

[0113] 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 is, and the system may face greater magnetic performance degradation.

[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 dimension information 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 The comprehensive evaluation index is jointly generated. The formula of 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. The comprehensive evaluation index is used to judge the current stress state. total Exceeds the system preset threshold I total,th When the system issues a level 2 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 secondary alarm is issued and manual processing is prompted.

[0122] It should be noted that the initial magnetization and saturation process 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. Nanocrystalline materials can quickly reach a saturation state through a magnetic field due to their tiny grains and excellent magnetic properties, thereby avoiding the influence of residual flux or local hysteresis in the core on subsequent measurements. The pretreatment process usually also 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 measurement. In addition, in material selection, nanocrystalline materials have higher magnetic permeability, lower eddy current loss and coercive force than traditional silicon steel. These characteristics make it have excellent performance in high-frequency applications and can better maintain the stability of magnetic properties.

[0123] Next, the current conduction and induction process of the primary winding and the secondary winding 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 the induction of the main current. The turns ratio in the design ensures that the change of the primary current can be sensed by the secondary winding with a precise ratio. This proportional relationship needs to be very strict to avoid introducing errors in the transmission process. In practical applications, this ratio 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 in 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 conditions, the current transformer will be affected by the external environment, such as temperature and mechanical stress, which will cause subtle changes in the magnetic properties of the core, thereby affecting the induced electromotive force and the final measurement results. Therefore, the system must perform real-time error compensation and calibration. This process includes the correction of magnetic domain disorder caused by temperature changes and mechanical vibrations to ensure that the measurement data of the transformer is still reliable even under harsh conditions. The choice of error compensation algorithm can be based on the actual usage scenario. In high-frequency and high-voltage applications, the eddy current effect and hysteresis loss of the core must be considered. These factors will have a direct impact on the accuracy of the data;

[0125] The core of the current transformer is affected by external mechanical stress and temperature, which may cause the gradual degradation of magnetic properties. For this reason, the system is designed with the function of real-time monitoring of mechanical stress density and magnetic permeability decrease rate to ensure timely response when the stress exceeds the preset threshold. Under the first-level high stress state, the system will further obtain the thermal stress accumulation rate and the increase in the coercive force of the core. This design aims to predict and discover potential problems in advance, especially in high stress environments, to prevent measurement distortion caused by a sharp increase in coercive force. In addition, these thresholds are based on the stress-magnetic curve of the core material, measured and optimized through experiments, which can ensure wide applicability under different working conditions.

[0126] The evaluation of the detection mode and stress degradation information further strengthens the intelligent monitoring of the system. When the system does not reach the secondary high stress state, it enters the detection mode to obtain stress demagnetization information and thermal stress accumulation information. The stress demagnetization information reflects how mechanical stress affects the magnetic properties of the core by analyzing the magnetic permeability loss rate and the magnetic domain reversal rate. The thermal stress accumulation information mainly evaluates the changes in stress gradient and magnetic property temperature coefficient caused by temperature changes. These two parts of information interact with each other to generate a comprehensive evaluation index to determine whether to enter a higher stress state. 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 correct the measurement data under different stress conditions through multiple experiments to ensure accurate stress evaluation in various environments.

[0127] Finally, the design of the secondary high stress state and system alarm further improves the intelligent measurement function of the transformer. Through the system monitoring of 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 time, thereby extending the life of the equipment. For example, in the application of high-voltage transmission lines, if stress-induced magnetic property 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 only 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 in the protection scope of the present invention.

Claims

1. A current transformer measurement method, characterized in that: include: Before the measurement of the current transformer begins, the iron core made of nanocrystalline material of the current transformer is initially magnetized and brought into a saturation state by a magnetic field; In the current transformer, a known AC current signal is applied through the primary winding. The AC current generates an alternating magnetic field in the iron core, causing the magnetic flux in the iron core to change. When the current transformer senses the change in current, an induced electromotive force is generated through the secondary winding, which reflects the measured value. 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 the measuring device for collection; 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 through the data processing module; Acquire external mechanical stress density data and core magnetic permeability reduction rate data in real time. When the external mechanical stress density is greater than the external mechanical stress density threshold preset by the system and the core magnetic permeability reduction rate is greater than the core magnetic permeability reduction rate threshold preset by the system, the system determines 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 the coercive force of the core are obtained. If the thermal stress accumulation rate is greater than the thermal stress accumulation rate threshold preset by the system and the increase in the coercive force of the core is greater than the coercive force increase threshold preset by the system, the system determines the environment as a second-level high stress state. In the second-level high stress state, the system issues a first-level alarm and prompts manual processing; 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, and 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 the thermal stress accumulation information. When the comprehensive evaluation index exceeds the comprehensive evaluation index threshold, a secondary alarm is issued and manual processing is prompted; otherwise, the system re-judges whether the environment is a primary high stress state.

2. A current transformer measurement method according to claim 1, characterized in that: The external mechanical stress density is monitored in real time, and the external mechanical stress density data is obtained through monitoring. The external mechanical stress density is proposed to be σ ext , the preset external mechanical stress density threshold of the system is σ th , the judgment conditions for external mechanical stress density data are: s ext >s th σ in the formula ext represents the external mechanical stress density monitored in real time, σ th is the threshold set by the system according to the material and structural characteristics. ext Exceeding the threshold σ th When , it means that the mechanical stress exceeds the bearing range of the material; The core magnetic permeability decrease rate is monitored in real time. By monitoring the core magnetic permeability decrease rate data, the core magnetic permeability decrease rate is proposed to be Δμ r , the system preset magnetic permeability decrease rate threshold is Δμ r,th , the judgment conditions for the magnetic permeability reduction rate data are: Dm r >Dm r,th where Δμ r is the rate of decrease of the magnetic permeability of the core, which indicates the rate of change of magnetic permeability with external stress; When the external mechanical stress density σ ext and the magnetic permeability decrease rate Δμ r When the respective threshold conditions are met at the same time, the system will enter the first-level high stress state. The judgment conditions are: s ext >s th AndDm r >Dm r,th The first-level high stress state indicates that the external mechanical stress density and the core magnetic permeability decrease rate both exceed the corresponding thresholds preset by the system. The system will judge the current environment as a first-level high stress state.

3. A current transformer measurement method according to claim 2, characterized in that: The thermal stress accumulation rate is monitored and the thermal stress accumulation rate is proposed to be R thermal The system preset thermal stress accumulation rate threshold is R thermal,th , the judgment condition of thermal stress accumulation rate is: R thermal >R thermal,th Where R thermal is the rate of thermal stress accumulation in the core due to temperature changes in a real-time environment. If R thermal Greater than the system threshold R thermal,th , indicating that the stress caused by temperature on the core has reached a level that requires monitoring; Monitor the increase in the coercive force of the core and set the increase in the coercive force of the core to ΔH c , the system preset threshold value of coercive force increase is ΔH c,th , the judgment condition for the increase in the coercive force of the core is: ΔH c >ΔH c,th The coercivity increase ΔH c It means that due to stress or environmental changes, the coercivity of the core material increases. If the coercivity increase exceeds the threshold ΔH c,th , indicating that the magnetic properties of the material are degraded; When judging the secondary high stress state, when the thermal stress accumulation rate R thermal and the increase in core coercivity ΔH c When the preset threshold is exceeded at the same time, the system will judge that it has entered the secondary high stress state. The judgment conditions are: 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 processing.

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

5. A 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 thermal stress gradient is assumed to be G thermal , G thermal Represents the stress gradient caused by temperature change; 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 effects of thermal stress and magnetic property changes; The second dimension includes the thermal stress accumulation rate and the coercive force change rate; The proposed thermal stress accumulation rate is R thermal , the coercivity change rate is The fourth dimension of thermal stress accumulation information I thermal4 Expressed as: 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 dimension information of thermal stress accumulation information to generate a thermal stress information index.

6. A 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 The comprehensive evaluation index is jointly generated. The formula of 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. The comprehensive evaluation index is used to judge the current stress state. total Exceeds the system preset threshold I total,th When the system issues a level 2 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 secondary alarm is issued and manual processing is prompted.

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