Power factor-based early warning method for dry-type air-core reactor turn-to-turn short circuit

Abstract

The application relates to a power factor-based early warning method for turn-to-turn short circuit of a dry-type air-core reactor. The method comprises the following steps: calculating power factor abnormality of the reactor according to the negative correlation between load state coefficients of each phase of the reactor and corresponding power factors; determining reactor analysis emphasis according to magnetic field peak degree uniformity of a coil of the reactor and the correlation between temperature change and current change of the coil of the reactor in a first historical period; determining reactor working condition risk degree according to the difference between equivalent capacitance values at an input end and an output end of the reactor and the reactor analysis emphasis; determining short circuit early warning coefficient of the reactor according to the target power factor abnormality and the reactor working condition risk degree; and determining short circuit early warning index of the reactor according to the difference between the short circuit early warning coefficient of the reactor and the average of short circuit early warning coefficients of all reactors in a power system to which the reactor belongs. The method can realize early warning of turn-to-turn short circuit and improve the operation safety of the reactor.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of fault early warning, in particular to a dry-type air-core reactor inter-turn short-circuit early warning method based on a power factor. BACKGROUND

[0002] The dry-type air-core reactor is an inductive device without oil and core in a power system, takes air as a magnetic path medium, is wound by multiple layers of parallel wires and is wrapped with insulation materials to form an encapsulation structure, and is mainly used for realizing functions such as reactive power compensation, harmonic suppression and short-circuit current limitation of the power system.

[0003] When the dry-type air-core reactor is used for reactive power compensation of the power system, long-term operation of the reactor may increase the probability of inter-turn short-circuit fault of the reactor, the inter-turn short-circuit refers to a fault phenomenon that adjacent wires in the coil of the reactor directly contact due to insulation damage to form a closed short-circuit loop, and the inter-turn short-circuit is one of the most common serious faults of the reactor and seriously threatens the safety of the power system and equipment.

[0004] The traditional early warning process for the inter-turn short-circuit of the dry-type air-core reactor usually relies on analysis of the power factor of the reactor, when the power factor of a certain phase of the running reactor exceeds a certain preset threshold, it is considered that there is a risk of inter-turn short-circuit fault in the internal three-phase circuit of the reactor, and in the actual scene, due to the difference in the actual operation load level of the reactor, the error of the judgment result obtained by the traditional method without auxiliary analysis of the load change is large, and the real-time working condition of the reactor changes complexly, and the inter-turn short-circuit will affect the changes of temperature, magnetic field and the like in the working condition, further leading to low accuracy of the judgment result obtained by the traditional method of only analyzing the numerical level of the power factor. SUMMARY

[0005] In order to solve the above technical problems, the purpose of the application is to provide a dry-type air-core reactor inter-turn short-circuit early warning method based on a power factor, and the technical solution is as follows:

[0006] In the first aspect, a dry-type air-core reactor inter-turn short-circuit early warning method based on a power factor is provided, and the method comprises the following steps:

[0007] According to the negative correlation degree between the load state coefficient of each phase of the reactor and the corresponding power factor, the power factor abnormality degree of the reactor is calculated, and the load state coefficient of each phase is obtained according to the ratio of the operating current of each phase to the corresponding rated current;

[0008] According to the magnetic field kurtosis uniformity of the coil of the reactor and the correlation degree between the temperature change and the current change of the coil of the reactor in the first historical period, the focusing degree of the reactor analysis is determined;

[0009] According to the difference between the equivalent capacitance value of the input end of the reactor and the equivalent capacitance value of the output end, and the analysis degree of the reactance, the risk degree of the reactance working condition is determined;

[0010] According to the target power factor abnormality and the risk degree of the reactance working condition, the short-circuit early warning coefficient of the reactor is determined; wherein, the target power factor abnormality is obtained by correcting the power factor abnormality according to the change of the power factor of each phase of the reactor in the first historical period;

[0011] According to the difference between the short-circuit early warning coefficient of the reactor and the average of the short-circuit early warning coefficients of all reactors in the power system to which the reactor belongs, the short-circuit early warning index of the reactor is determined, so as to perform short-circuit early warning according to the short-circuit early warning index.

[0012] Optionally, the power factor abnormality of the reactor is calculated according to the negative correlation degree between the load state coefficient of each phase of the reactor and the corresponding power factor, comprising:

[0013] According to the ratio of the operating current of each phase of the reactor to the corresponding rated current, the load state coefficient of the phase is determined;

[0014] The difference between the power factor of each phase of the reactor and the average power factor is calculated respectively to obtain the first power factor difference value of the phase; the average power factor indicates the average of the power factors of the three phases of the reactor;

[0015] The reciprocal of the sum of the power factor difference values of the three phases of the reactor is calculated to obtain the power factor consistency coefficient of the reactor; the power factor consistency coefficient indicates the consistency degree of the power factors between the three-phase circuits of the reactor;

[0016] The historical load coefficient of each phase in the second historical period is determined to be the same as the load state coefficient of the phase at a plurality of time points, and the average of the historical power factors of the phase at the plurality of time points is calculated to obtain the historical power factor average of the phase; wherein, the second historical period is greater than the first historical period;

[0017] The difference between the power factor of each phase and the historical power factor average of the phase is calculated to obtain the second power factor difference value of the phase, and the sum of the second power factor difference values of the three phases of the reactor is calculated to obtain the historical power factor difference value of the reactor;

[0018] According to the historical power factor difference value of the reactor, the power factor consistency coefficient of the reactor and the load state coefficient of each phase of the reactor, the power factor abnormality of the reactor is calculated; the power factor abnormality indicates the deviation degree of the power factor of the reactor relative to the historical power factor under the same load state.

[0019] Optionally, the power factor abnormality of the reactor is calculated according to the historical power factor difference value of the reactor, the power factor consistency coefficient of the reactor and the load state coefficient of each phase of the reactor, comprising:

[0020] determining the abnormal factor of the reactor according to a ratio of a historical power factor difference of the reactor to a power factor consistency coefficient of the reactor;

[0021] establishing a coordinate system with the historical load state coefficient of each phase in the first historical period as the ordinate and the multiple time points in the first historical period as the abscissa, and fitting each point in the coordinate system by the least square straight line fitting method to obtain the historical load state coefficient curve of the phase;

[0022] establishing a coordinate system with the historical power factor of each phase in the first historical period as the ordinate and the multiple time points in the first historical period as the abscissa, and fitting each point in the coordinate system by the least square straight line fitting method to obtain the historical power factor curve of the phase;

[0023] calculating the absolute value of the Pearson correlation coefficient of the historical load state coefficient curve of each phase and the historical power factor curve of the phase to obtain the negative correlation coincidence degree of the phase, and calculating the sum of the negative correlation coincidence degrees of the three phases of the reactor to obtain the negative correlation coincidence degree superposition value of the reactor;

[0024] determining the power factor abnormality of the reactor according to a ratio of the abnormal factor of the reactor to the negative correlation coincidence degree superposition value.

[0025] Optionally, determining the electromagnetic field focusing degree of the reactor according to the magnetic field focusing degree uniformity of the coil of the reactor and the correlation degree of the temperature change and the current change of the coil of the reactor in the first historical period, including:

[0026] screening multiple groups of axisymmetric point positions on the coil of the reactor;

[0027] determining the magnetic field focusing degree ratio of the reactor according to the sum of the magnetic field focusing degrees of the multiple groups of axisymmetric point positions on the coil of the reactor, and the mean value of the sum of the magnetic field focusing degrees of the multiple groups of axisymmetric point positions at the multiple time points with the same mean value of the load state coefficients of the three phases in the second historical period;

[0028] for each group of axisymmetric point positions, calculating the absolute difference value of the magnetic field focusing degrees of two points in the group of axisymmetric point positions to obtain the magnetic field focusing degree deviation coefficient of the group of axisymmetric point positions;

[0029] calculating the mean value of the magnetic field focusing degree deviation coefficients of the multiple groups of axisymmetric point positions to obtain the mean value of the magnetic field focusing degree deviation coefficients;

[0030] obtaining the electromagnetic field uniformity of the reactor according to the product of the magnetic field focusing degree ratio of the reactor and the mean value of the magnetic field focusing degree deviation coefficients; the electromagnetic field uniformity indicates the uniformity of the spatial distribution of the magnetic field inside the reactor;

[0031] According to the electromagnetic field uniformity of the reactor and the correlation between the temperature change and the current change of the coil of the reactor in the first historical period, the degree of emphasis of the reactance analysis is determined.

[0032] Optionally, according to the electromagnetic field uniformity of the reactor and the correlation between the temperature change and the current change of the coil of the reactor in the first historical period, the degree of emphasis of the reactance analysis is determined, comprising:

[0033] A coordinate system is established with the sum of the three-phase currents of the reactor in the first historical period as the ordinate and a plurality of time points in the first historical period as the abscissa, and each point in the coordinate system is fitted by a least square straight line fitting method to obtain a historical current curve;

[0034] A coordinate system is established with the coil temperature of the reactor in the first historical period as the ordinate and a plurality of time points in the first historical period as the abscissa, and each point in the coordinate system is fitted by a least square straight line fitting method to obtain a historical temperature curve;

[0035] The Pearson correlation coefficient of the historical current curve and the historical temperature curve is calculated to obtain a current-temperature correlation coefficient;

[0036] The sum of the slope of the historical current curve and the slope of the historical temperature curve is calculated to obtain a slope sum value;

[0037] According to the current-temperature correlation coefficient, the slope sum value and the electromagnetic field uniformity, the degree of emphasis of the reactance analysis is determined.

[0038] Optionally, according to the difference between the input end equivalent capacitance and the output end equivalent capacitance value of the reactor, the degree of emphasis of the reactance analysis, the risk degree of the reactance working condition is determined, comprising:

[0039] According to the difference between the input end equivalent capacitance and the output end equivalent capacitance value of the reactor, the degree of emphasis of the reactance analysis, the risk degree of the reactance working condition is determined, comprising:

[0040] According to the ratio of the degree of emphasis of the reactance analysis and the degree of compensation of the reactive power, the risk degree of the reactance working condition is determined; the risk degree of the reactance working condition indicates the degree of abnormal working condition of the reactor caused by short-circuit fault.

[0041] Optionally, before determining the short-circuit early warning coefficient of the reactor according to the target power factor abnormality degree and the risk degree of the reactance working condition, further comprising:

[0042] A coordinate system is established with the historical power factor of each phase in the first historical period as the ordinate and a plurality of time points in the first historical period as the abscissa, and each point in the coordinate system is fitted by a least square straight line fitting method to obtain a historical power factor curve of the phase;

[0043] A coordinate system is established with the historical power factor of each phase within the target historical period as the vertical axis and multiple moments within the target historical period as the horizontal axis. The points in the coordinate system are fitted using the least squares linear fitting method to obtain the target historical power factor curve of that phase. The target historical period indicates the period within the second historical period that is at the same historical moment as the current moment and lasts for a preset duration.

[0044] The correction coefficient is obtained by calculating the ratio of the mean slope of the three-phase historical power factor curves to the mean slope of the three-phase target historical power factor curves.

[0045] The power factor anomaly is corrected based on the correction factor to obtain the target power factor anomaly.

[0046] Optionally, the short-circuit warning coefficient of the reactor is determined based on the anomaly of the target power factor and the risk of reactor operating conditions, including:

[0047] The short-circuit warning coefficient of the reactor is determined by multiplying the risk level of the reactor operating condition by the anomaly level of the target power factor.

[0048] Optionally, the short-circuit warning index of the reactor is determined based on the difference between the short-circuit warning factor of the reactor and the average short-circuit warning factor of all reactors in the power system to which the reactor belongs, including:

[0049] The short-circuit warning coefficient of the reactor is calculated by the difference between the short-circuit warning coefficient of the reactor and the mean of the short-circuit warning coefficients of all reactors in the power system to which the reactor belongs, and the short-circuit warning index of the reactor is determined.

[0050] Optionally, after determining the short-circuit warning index of the reactor based on the difference between the short-circuit warning factor of the reactor and the average short-circuit warning factor of all reactors in the power system to which the reactor belongs, the process further includes:

[0051] If the short-circuit warning index of the reactor is greater than the preset index, it is determined that there is a short-circuit risk in the reactor and a power disconnection warning is issued.

[0052] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of this application.

[0053] This application offers the following advantages: It obtains the load state coefficient by using the ratio of each phase's operating current to its rated current, and quantifies the negative correlation between the power factor of each phase and the load accordingly, calculating the power factor anomaly in real time. The anomaly is corrected using the short-term rise in power factor within the first historical period to form a target power factor anomaly. Simultaneously, the coil magnetic field kurtosis uniformity and the correlation between coil temperature and current changes within the same historical period are combined to determine the emphasis of reactance analysis. Based on the difference between the equivalent capacitance at the input and output ends and the emphasis of reactance analysis, the reactance operating condition risk is derived. A short-circuit warning coefficient is determined from the target power factor anomaly and the reactance operating condition risk. The difference between the short-circuit warning coefficient and the average short-circuit warning coefficient of all reactors in the power system is used as the short-circuit warning index, achieving early warning of inter-turn short circuits. Therefore, compared to the traditional single power factor threshold judgment, this significantly improves the operational safety of dry-type air-core reactors under complex operating conditions. Attached Figure Description

[0054] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a flowchart of an early alarm method for inter-turn short circuit of a dry air-core reactor based on power factor in one embodiment;

[0056] Figure 2 This is a schematic diagram of the structure of an early alarm system for inter-turn short circuit of a dry-type air-core reactor based on power factor in one embodiment;

[0057] Figure 3 This is a schematic diagram of the structure of an electronic device in one embodiment. Detailed Implementation

[0058] To further illustrate the technical means and effects adopted by this application to achieve the intended purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a power factor-based early alarm method for inter-turn short circuits in a dry-type air-core reactor proposed in this application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0060] The following, with reference to the accompanying drawings, details a specific scheme for an early alarm method for inter-turn short circuits in dry-type air-core reactors based on power factor, as provided in this application. For example... Figure 1 As shown,

[0061] S11. Calculate the power factor anomaly of the reactor based on the negative correlation between the load state coefficient of each phase of the reactor and the corresponding power factor.

[0062] The load state factor for each phase is obtained by the ratio of the operating current of each phase to the corresponding rated current. The load state factor indicates the proportion of the actual operating load level of the current analyzed phase of the reactor to its rated load.

[0063] Among them, the power factor anomaly indicates the degree of deviation of the reactor's power factor from the power factor under historical load conditions.

[0064] Dry-type air-core reactors are important inductive components in power systems. They rely on the inductive characteristics of the equipment to compensate for the capacitive charging current of the line, limit the rise of system voltage and operating overvoltage, reduce the system insulation level, and ensure the reliable operation of the line, thereby realizing the function of reactive power compensation in the power system.

[0065] The reactor mainly consists of coil windings and encapsulation structure. The coil windings are encapsulated and bonded together in multiple layers to provide electrical isolation. Its overall appearance structure presents a multi-layered encapsulation structure.

[0066] Inter-turn short circuit in a dry-type air-core reactor refers to a fault in which the insulation layer between adjacent coil windings in the reactor coil is damaged due to long-term operation, causing the originally insulated wires to make electrical contact and forming a partially closed circuit. Inter-turn short circuits in reactors can shorten the life of electrical components and increase the risk of accidents.

[0067] Firstly, when performing reactive power compensation on three-phase power in a power system, three-phase dry-type air-core reactors are often used. Therefore, the power factor and operating current information of each phase circuit of the reactor are read through the power system's electrical parameter storage module, the rated current information of the reactor during operation is read through the power system's equipment parameter storage module, the magnetic field kurtosis information of the reactor's three-phase current passing through each encapsulation coil layer is read through the power system's electromagnetic induction module, the temperature information of each encapsulation coil layer is read through an infrared detector, and the equivalent capacitance value of the reactor's input and output circuits is read through the power system's circuit capacitive monitoring module. Finally, the read data is uploaded to the data acquisition system for subsequent analysis.

[0068] In one embodiment, the power factor anomaly of the reactor is calculated based on the negative correlation between the load state coefficient of each phase of the reactor and the corresponding power factor, including:

[0069] The load state factor of each phase is determined by the ratio of the operating current of each phase of the reactor to the corresponding rated current.

[0070] Calculate the difference between the power factor and the mean power factor for each phase of the reactor to obtain the first power factor difference for that phase; the mean power factor indicates the mean power factor of the three phases of the reactor.

[0071] The power factor consistency coefficient of the reactor is obtained by calculating the reciprocal of the sum of the power factor differences of the three phases of the reactor; the power factor consistency coefficient indicates the degree of consistency of the power factor among the three phases of the reactor.

[0072] Within the second historical period, determine multiple moments when the historical load factor of each phase is the same as the load state factor of that phase, and calculate the average historical power factor of that phase at multiple moments to obtain the average historical power factor of that phase; wherein, the second historical period is longer than the first historical period;

[0073] Calculate the difference between the power factor of each phase and the historical average power factor of that phase to obtain the second power factor difference value of that phase, and calculate the sum of the second power factor differences of the three phases of the reactor to obtain the historical power factor difference value of the reactor;

[0074] The power factor anomaly of the reactor is calculated based on the historical power factor difference, the power factor consistency coefficient, and the load state coefficient of each phase of the reactor. The power factor anomaly indicates the degree of deviation of the reactor's power factor from the power factor under the same historical load conditions.

[0075] The second historical period can be set according to the actual situation. For example, it can be 20 days, that is, the second historical period indicates the period within 20 days before the current time.

[0076] Considering that the power factor of the reactor is affected not only by the inter-turn short circuit phenomenon, but also by the real-time load level of the circuit, this step first analyzes the load state coefficient of the reactor based on the operating current level, and then obtains the negative phase case based on the matching relationship between the power factor of a single phase and the load state coefficient.

[0077] When the reactor is operating normally, the electrical parameters of each phase should be at a relatively consistent level. However, inter-turn short circuits will disrupt the consistency of the electrical parameters. Therefore, based on the positive correlation conformity, the real-time power factor anomaly of the reactor is obtained by combining the uniform convergence of the power factors of each phase.

[0078] Power systems are affected by fluctuations in power demand, and their load status varies at different times. The load status affects the electrical parameters of reactors. Therefore, it is necessary to first assess the load status of reactors. For single-phase power in a three-phase reactor, the real-time operating current level can reflect the current load status.

[0079] For the single-phase power currently being analyzed in the reactor, obtain the single-phase operating current. Meanwhile, the rated operating current is recorded as Calculate the load state factor of the current analysis phase of the reactor. : The higher the proportion of the single-phase real-time operating current of the reactor to the rated current, the higher the load level of that phase. When the load is low, the excess capacitive reactive power in the power system is more significant (such as during off-peak hours at night), and the compensation effect of the reactor should be more obvious. At this time, the power factor will increase significantly, so there should be a certain negative correlation between the load state factor and the power factor.

[0080] During normal operation of a power system, due to the symmetry of the three-phase power structure, the load levels of the three phases are relatively consistent. This means that under normal conditions, the power factor variation of the three phases should be relatively small. However, if a short circuit occurs between turns in a phase, the power factor of that phase will increase abnormally, thereby disrupting the convergence of the power factors among the three phases at the same time.

[0081] Therefore, the power factor of the i-th phase in the current analysis reactor is calculated as follows: Simultaneously calculate the average three-phase power factor of the reactor. Then, the power factor consistency coefficient of the current analysis reactor is calculated. :

[0082] ;

[0083] in, This is the power factor consistency coefficient for the current analysis reactor. Let be the power factor of the i-th phase. The power factor average indicates the average power factor of the three phases of the reactor. This indicates the first power factor difference of the i-th phase. The worse the convergence of the real-time power factors of the three phases of the reactor being analyzed, that is, the smaller the power factor consistency coefficient, and the greater the difference between the power factor and the historical power factor at the same load condition level, the more abnormal the real-time power factor of the reactor is.

[0084] An abnormal increase in the power factor caused by an inter-turn short circuit will result in a significant difference between the power factor of that phase circuit and its historical power factor under the same load condition. Therefore, the time points within the historical 20 days of the same load condition coefficient for each phase circuit are extracted, and the average power factor of that phase at multiple time points is calculated to obtain the historical average power factor of that phase. Then, the difference between the real-time power factor of that phase and its historical average power factor is calculated to obtain the second power factor difference of that phase. Finally, the second power factor differences of the three phases of the reactor currently being analyzed are summed to obtain the historical power factor difference of the reactor. .

[0085] In one embodiment, the power factor anomaly of the reactor is calculated based on the historical power factor difference of the reactor, the power factor consistency coefficient of the reactor, and the load state coefficient of each phase of the reactor, including:

[0086] The anomalous factor of the reactor is determined by the ratio of the historical power factor difference of the reactor to the power factor consistency coefficient of the reactor.

[0087] A coordinate system is established with the historical load state coefficient of each phase in the first historical period as the vertical axis and multiple moments in the first historical period as the horizontal axis. The points in the coordinate system are then fitted using the least squares straight line fitting method to obtain the historical load state coefficient curve of that phase.

[0088] A coordinate system is established with the historical power factor of each phase in the first historical period as the vertical axis and multiple moments in the first historical period as the horizontal axis. The points in the coordinate system are fitted using the least squares linear fitting method to obtain the historical power factor curve of that phase.

[0089] Calculate the absolute value of the Pearson correlation coefficient between the historical load state coefficient curve and the historical power factor curve of each phase to obtain the negative correlation compliance degree of that phase. Then calculate the sum of the negative correlation compliance degrees of the three phases of the reactor to obtain the superimposed value of the negative correlation compliance degree of the reactor.

[0090] The power factor anomaly of the reactor is determined by the ratio of the anomalous factor of the reactor to the superimposed value of the negative correlation conformity.

[0091] The first historical time period can be set according to the actual situation, for example, 3 seconds. That is, the second historical time period indicates the time period within 3 seconds before the current time.

[0092] By comparing the real-time power factor with the historical state factor power factor under the same load, and combining this with the power factor convergence, the anomalous factor of the currently analyzed reactor is obtained. Anomalous factors The calculation formula is: .in, To analyze the anomalous factors of the reactor, This represents the historical power factor difference of the reactor. The power factor consistency coefficient is used to analyze the reactor. The larger the value of the anomalous factor, the more the power factor behavior deviates from the normal mode, and the higher the risk of inter-turn short circuit.

[0093] For the current analysis of single-phase power in the reactor, within the first historical time period (i.e., the first 3 seconds of the current moment), a coordinate system is established with multiple moments within the first historical time period as the x-axis and the load state factor at each moment as the y-axis. The points in this coordinate system are then fitted using the least squares linear fitting method to obtain the historical load state factor curve for that phase. Similarly, a coordinate system is established with the historical power factor of each phase within the first historical time period as the y-axis and multiple moments within the first historical time period as the x-axis. The points in this coordinate system are then fitted using the least squares linear fitting method to obtain the historical power factor curve for that phase. The absolute value of the Pearson correlation coefficient between the historical load state factor curve and the historical power factor curve for each phase is calculated. The negative correlation coefficient for that phase is obtained, indicating the degree of agreement between the reactor's single-phase power factor and the load condition. A smaller Pearson correlation coefficient for that phase reflects a more negative correlation between the reactor's power factor change and the load condition, indicating a better operating condition for that phase of the reactor.

[0094] Calculate the sum of the negative correlation compliance degrees of the three phases of the reactor to obtain the superposition value of the negative correlation compliance degrees of the reactor. If the negative correlation coefficient is summed... The smaller the value, the worse the negative correlation between the power factor and load changes. Additionally, if the anomalous factor... The larger the value, the stronger the power factor anomaly of the reactor being analyzed. Therefore, the real-time power factor anomaly of the reactor being analyzed is calculated. : .in, To analyze the real-time power factor anomaly of the reactor, To analyze the anomalous factors of the reactor, is the superposition value of the negative correlation conformity of the reactor, and norm() is the normalization function.

[0095] Calculate and record the real-time power factor anomaly of each reactor in the power system.

[0096] S12. Determine the focus of the reactance analysis based on the uniformity of the magnetic field kurtosis of the reactor coil and the correlation between the temperature change and current change of the reactor coil during the first historical period.

[0097] The intensity of reactance analysis indicates the degree of superposition of multiple thermal, electrical, and magnetic anomalies caused by inter-turn short circuits in the reactor. The greater the intensity of numerical reactance analysis, the steeper the synchronous rise of current and temperature and the more significant the disruption of the axisymmetry of the magnetic field.

[0098] Considering that an inter-turn short circuit will cause the ultra-large current in the short-circuit loop to generate a large amount of Joule heat in the resistor, which will lead to a surge in active power loss, reflected in the high power factor, and at the same time, the ultra-large circulating current formed at the inter-turn short circuit will generate a high-intensity, concentrated magnetic field and a strong high temperature around the fault point, this step focuses on the reactive power analysis based on the destructive behavior of the magnetic field and temperature of the coil layer.

[0099] Furthermore, the main function of dry-type air-core reactors in power systems is to perform inductive compensation of redundant capacitive circuits, that is, reactive power compensation. However, when an inter-turn short circuit occurs in the reactor, the reactive power compensation capability of the reactor to the power system decreases significantly due to changes in reactance parameters and increased energy loss. Therefore, based on the focus of reactance analysis, the reactive power compensation performance is analyzed to obtain the real-time short-circuit warning coefficient of the reactor.

[0100] In one embodiment, the emphasis of reactance analysis is determined based on the uniformity of the magnetic field kurtosis of the reactor coil and the correlation between temperature and current changes in the reactor coil during a first historical period, including:

[0101] Screening multiple sets of axisymmetric points on the coil of the reactor;

[0102] The magnetic field kurtosis ratio of the reactor is determined by the sum of the magnetic field kurtosis of multiple axisymmetric points on the reactor coil and the mean of the sum of the magnetic field kurtosis of multiple axisymmetric points at multiple moments during the second historical period that are the same as the mean of the load state coefficient of the three phases.

[0103] For each group of axisymmetric points, calculate the absolute difference in magnetic field kurtosis between the two points in that group of axisymmetric points to obtain the magnetic field kurtosis deviation coefficient of that group of axisymmetric points.

[0104] Calculate the mean value of the magnetic field kurtosis deviation coefficient for multiple sets of axisymmetric points to obtain the mean value of the magnetic field kurtosis deviation coefficient;

[0105] The electromagnetic field uniformity of a reactor is obtained by multiplying the kurtosis ratio of its magnetic field by the mean value of its magnetic field kurtosis deviation coefficient. The electromagnetic field uniformity indicates the degree of uniformity of the spatial distribution of the magnetic field inside the reactor.

[0106] The focus of the reactance analysis is determined based on the electromagnetic field uniformity of the reactor and the correlation between the temperature and current changes of the reactor coil during the first historical period.

[0107] The working principle of a reactor is essentially that of an inductor coil. When the reactor is running, each layer of the encapsulated coil will induce a magnetic field. The kurtosis parameter of the magnetic field reflects the degree of concentration of the magnetic field intensity in space. When the reactor exhibits inter-turn short circuit, the coil near the fault point will form a closed short-circuit loop due to electromagnetic induction. Since the resistance of the short-circuit loop is much smaller than that of the normal winding, a super-large circulating current hundreds or even thousands of times larger than the normal current will be generated in the short-circuit loop. These circulating currents will generate a high-intensity, concentrated magnetic field around the fault point, which will be reflected in a significant increase in the overall magnetic field kurtosis of the reactor coil. At the same time, the magnetic field of the reactor itself is axially symmetrically distributed. That is, when the reactor is running normally, the magnetic field kurtosis corresponding to the axially symmetrically distributed points on its coil should show a consistent uniformity. However, due to the increase in the magnetic field at the local fault point in an inter-turn short circuit, the uniformity of the magnetic field kurtosis corresponding to the axially symmetrically distributed points on the reactor becomes worse.

[0108] Any preset selection on the current analysis reactor coil A set of axisymmetrically distributed points, each set containing two points, is given by the sum of the kurtosis of the magnetic field at multiple sets of axisymmetric points on the reactor. Then, calculate the total kurtosis of the magnetic field at multiple points within the past 20 days that are at the same time as the average load state coefficient of the three phases. Then, divide the total kurtosis by the number of times to obtain the historical average kurtosis of the multiple sets of axisymmetric points. Then calculate the sum of the kurtosis of the magnetic field at multiple axisymmetric points on the reactor. Historical average magnetic field kurtosis of multiple axisymmetric points The ratio of the magnetic field kurtosis of the reactor is obtained by comparing the ratio of the two values.

[0109] For a single group of axisymmetric distribution points, calculate the absolute difference in real-time magnetic field kurtosis between two points within the group, denoted as the magnetic field kurtosis deviation coefficient for that group of axisymmetric points. Then, average the magnetic field kurtosis deviation coefficients corresponding to all groups of axisymmetric distribution points to obtain the mean magnetic field kurtosis deviation coefficient. Calculate the electromagnetic field uniformity of the current analysis reactor. electromagnetic field uniformity The calculation formula is: .

[0110] like The larger the value, the higher the real-time magnetic field kurtosis of the reactor coil compared to the historical magnetic field kurtosis level under the same load conditions, and the stronger the inter-turn short circuit performance. Simultaneously, if... The larger the value, the worse the uniformity of the magnetic field between the axisymmetrically distributed points of the real-time reactor coil, which further indicates that the inter-turn short circuit tends to increase.

[0111] In one embodiment, the emphasis of reactance analysis is determined based on the electromagnetic field uniformity of the reactor and the correlation between the temperature change and current change of the reactor coil during the first historical period, including:

[0112] A coordinate system is established with the sum of the three-phase currents of the reactor in the first historical period as the vertical axis and multiple moments in the first historical period as the horizontal axis. The points in the coordinate system are fitted using the least squares linear fitting method to obtain the historical current curve.

[0113] A coordinate system is established with the coil temperature of the reactor in the first historical period as the vertical axis and multiple moments in the first historical period as the horizontal axis. The points in the coordinate system are then fitted using the least squares linear fitting method to obtain the historical temperature curve.

[0114] Calculate the Pearson correlation coefficient between the historical current curve and the historical temperature curve to obtain the current-temperature correlation coefficient;

[0115] Calculate the sum of the slopes of the historical current curve and the historical temperature curve to obtain the slope sum value;

[0116] The emphasis of reactance analysis is determined based on the current-temperature correlation coefficient, slope and value, and electromagnetic field uniformity.

[0117] When the insulation at the short circuit point between the turns of the reactor is compromised, the magnetic fields between adjacent coils converge, causing the current to merge and short-circuit. Specifically, this is reflected in the rapid increase of the current flowing through the reactor circuit due to the short circuit. At the same time, the heat of the coil accumulates at the short circuit point, resulting in an abnormally high temperature. Therefore, there is a certain positive correlation between the change in current and the change in coil temperature.

[0118] Therefore, a coordinate system can be established with the sum of the three-phase currents of the reactor within the first historical period as the ordinate and multiple moments within the first historical period as the abscissa. The points in this coordinate system can then be fitted using the least squares linear fitting method to obtain the historical current curve. Similarly, a coordinate system can be established with the coil temperature of the reactor within the first historical period as the ordinate and multiple moments within the first historical period as the abscissa. The points in this coordinate system can then be fitted using the least squares linear fitting method to obtain the historical temperature curve.

[0119] Calculate the Pearson correlation coefficient between historical current curves and historical temperature curves to obtain the current-temperature correlation coefficient. Calculate the sum of the slopes of the historical current curve and the historical temperature curve to obtain the slope sum value. Calculate the reactance analysis focus of the current analysis reactor. :

[0120] ;

[0121] If the temperature rise of the current-temperature coil in the reactor is significant in the short term, and the positive correlation between the two curves is strong (i.e., the current-temperature correlation coefficient is high), then the analysis shows a strong trend towards higher current and temperature. The larger the value, the more attention and early warning are needed regarding the real-time status of the reactor.

[0122] S13. Determine the risk level of reactor operating conditions based on the difference between the equivalent capacitance at the input terminal and the equivalent capacitance at the output terminal of the reactor, and the emphasis of the reactor analysis.

[0123] Among them, the reactor operating condition risk level indicates the degree of abnormality in the operating condition of the reactor caused by a short circuit fault.

[0124] In one embodiment, the risk level of the reactor operating condition is determined based on the difference between the equivalent capacitance at the reactor's input and output terminals, and the emphasis of the reactor analysis, including:

[0125] The reactive power compensation performance of the reactor is determined by the difference between the equivalent capacitance at the input terminal and the equivalent capacitance at the output terminal.

[0126] The reactor operating condition risk level is determined by the ratio of the emphasis of reactance analysis to the performance of reactive power compensation; the reactor operating condition risk level indicates the degree of abnormality in the reactor's operating condition caused by short-circuit faults.

[0127] The reactive power compensation performance indicates the actual compensation effect of the reactor on the system's redundant capacitive reactive power. The smaller the reactive power compensation performance, the weaker the compensation capability, and the higher the risk of reactive power imbalance caused by inter-turn short circuits.

[0128] Because reactors are inductive elements, their main function in power systems is to compensate for the redundant capacitive circuit portion of the circuit. However, inter-turn short circuits can reduce the reactive power compensation efficiency of reactors for capacitive circuits.

[0129] Obtain the equivalent circuit capacitance of the current analysis reactor at the input terminal of the power system. and the equivalent circuit capacitance at the output terminal. Calculate the real-time reactive power compensation performance of the current analysis reactor. reactive power compensation performance The calculation formula is: If the current analysis focuses on the real-time reactance of the reactor... The higher the level, the better the reactive power compensation performance of the redundant capacitive portion of the power system. The worse the condition, the higher the risk of short-circuit operation. Therefore, the reactance risk level of the reactor in the current analysis is calculated. : .

[0130] S14. Determine the short-circuit warning coefficient of the reactor based on the anomaly of the target power factor and the risk of reactor operating conditions.

[0131] The target power factor anomaly is obtained by correcting the power factor anomaly based on the changes in the power factor of each phase of the reactor during the first historical period.

[0132] The short-circuit warning coefficient is used to quantify the overall risk level of an inter-turn short circuit occurring in a reactor.

[0133] Specifically, before determining the short-circuit warning factor of the reactor based on the anomaly of the target power factor and the risk of reactor operating conditions, the following steps are also included:

[0134] A coordinate system is established with the historical power factor of each phase in the first historical period as the vertical axis and multiple moments in the first historical period as the horizontal axis. The points in the coordinate system are fitted using the least squares linear fitting method to obtain the historical power factor curve of that phase.

[0135] A coordinate system is established with the historical power factor of each phase within the target historical period as the vertical axis and multiple moments within the target historical period as the horizontal axis. The points in the coordinate system are fitted using the least squares linear fitting method to obtain the target historical power factor curve of that phase. The target historical period indicates the period within the second historical period that is at the same historical moment as the current moment and lasts for a preset duration.

[0136] The correction coefficient is obtained by calculating the ratio of the mean slope of the three-phase historical power factor curves to the mean slope of the three-phase target historical power factor curves.

[0137] The power factor anomaly is corrected based on the correction factor to obtain the target power factor anomaly.

[0138] The target historical time period can be set according to the actual situation. For example, it can be a period within the second historical time period that is at the same historical moment as the current moment and lasts for 3 seconds. Specifically, if the current moment is 18:07:10, then the target historical time period is the period from 18:07:07 to 18:07:09 on any day within the previous 20 days.

[0139] Power systems exhibit strong stability during operation, which is reflected in the fact that load levels do not fluctuate excessively in the short term. However, inter-turn short circuits in reactors can cause the power factor to rise sharply in the short term. Therefore, by observing the changes in the power factor in the short term, we can further distinguish the abnormal short-circuit behavior of reactors and correct the power factor anomaly.

[0140] A coordinate system is established with the historical power factor of each phase within the first historical period as the ordinate and multiple moments within the first historical period as the abscissa. The points in the coordinate system are then fitted using the least squares linear fitting method to obtain the historical power factor curve for that phase. Similarly, a coordinate system is established with the historical power factor of each phase within the target historical period as the ordinate and multiple moments within the target historical period as the abscissa. The points in the coordinate system are then fitted using the least squares linear fitting method to obtain the target historical power factor curve for that phase.

[0141] Calculate the mean slope of the historical power factor curves for the three phases. Then calculate the mean slope of the target historical power factor curves for the three phases. Finally, the mean slope of the historical power factor curves for the three phases is calculated. The mean slope of the target historical power factor curve for the three phases The ratio is used to obtain the correction factor. Based on the correction factor, the power factor anomaly After correction, the anomaly of the target power factor is obtained. Target power factor anomaly The calculation formula is: If the current analysis shows that the rise in the power factor of the reactor in the short-term real-time period is higher than the historical level, it indicates that the power factor anomaly is being underestimated more, and a higher adjustment is needed.

[0142] In one embodiment, the short-circuit warning coefficient of the reactor is determined based on the target power factor anomaly and the reactor operating condition risk, including:

[0143] The short-circuit warning coefficient of the reactor is determined by multiplying the risk level of the reactor operating condition by the anomaly level of the target power factor.

[0144] If the real-time reactor operating condition risk level of the reactor The larger the target power factor anomaly, the greater the anomaly. The higher the value, the greater the warning level should be for the inter-turn short circuit phenomenon of the reactor. Therefore, the short circuit warning coefficient of the reactor being analyzed is calculated. :

[0145] ;

[0146] Calculate and record the short-circuit warning coefficients of each dry-type air-core reactor in the power system.

[0147] S15. Based on the difference between the short-circuit warning coefficient of the reactor and the average short-circuit warning coefficient of all reactors in the power system to which the reactor belongs, determine the short-circuit warning index of the reactor, so as to carry out short-circuit warning based on the short-circuit warning index.

[0148] In one embodiment, the short-circuit warning index of the reactor is determined based on the difference between the short-circuit warning factor of the reactor and the average short-circuit warning factor of all reactors in the power system to which the reactor belongs, including:

[0149] The short-circuit warning coefficient of the reactor is calculated by the difference between the short-circuit warning coefficient of the reactor and the mean of the short-circuit warning coefficients of all reactors in the power system to which the reactor belongs, and the short-circuit warning index of the reactor is determined.

[0150] Based on the above steps, the real-time short-circuit warning coefficient of each reactor in the power system can be obtained. Since inter-turn short circuits have a low probability of sudden occurrence, the short-circuit warning coefficient level of the currently analyzed reactor can be compared with that of the reactors in the power system to obtain the short-circuit warning index of the reactor.

[0151] Calculate the mean short-circuit warning coefficient of all reactors in the power system to which the currently analyzed reactor belongs. Short circuit warning index of reactor The calculation formula is: .

[0152] If the short-circuit warning index of the currently analyzed reactor is higher than the overall short-circuit warning index of all reactors in the power system, it indicates that the reactor is more likely to have an inter-turn short-circuit risk, and therefore a risk warning is more necessary. Calculate and record the real-time short-circuit warning index of each dry-type air-core reactor in the power system.

[0153] In one embodiment, after determining the short-circuit warning index of the reactor based on the difference between the short-circuit warning factor of the reactor and the average short-circuit warning factor of all reactors in the power system to which the reactor belongs, the method further includes:

[0154] If the short-circuit warning index of the reactor is greater than the preset index, it is determined that there is a short-circuit risk in the reactor and a power disconnection warning is issued.

[0155] The preset index can be set according to the actual situation, for example, it can be 0.78.

[0156] This application sets preset thresholds of 0.45 and 0.78, and divides the normalized short-circuit warning index of each reactor into multiple numerical ranges using the preset thresholds.

[0157] When the short-circuit warning index is below 0.45, the reactor is considered to have a low risk of inter-turn short circuit and no additional intervention is required.

[0158] When the short-circuit warning index is in the range of 0.45 to 0.78, the value in this range is normalized and then divided into ten equal parts, and then ten alarm levels are set. The corresponding alarm level is applied to the reactor according to the ten equal parts range to which the short-circuit warning index belongs.

[0159] When the alarm index is higher than 0.78, the reactor is considered to have a high risk of inter-turn short circuit. The reactor power switch (such as the circuit breaker) should be disconnected. Therefore, a power disconnection warning can be issued to prompt the disconnecting switch to be opened to ensure that the faulty equipment is completely isolated from the system. At the same time, a maintenance team should be dispatched for inspection and repair, and the reactor should be replaced as appropriate.

[0160] This application obtains the load state coefficient by the ratio of the operating current to the rated current of each phase, and quantifies the negative correlation between the power factor of each phase and the load accordingly, calculating the power factor anomaly in real time. The anomaly is corrected using the short-term rise in power factor within the first historical period to form the target power factor anomaly. Simultaneously, the coil magnetic field kurtosis uniformity and the correlation between coil temperature and current changes within the same historical period are combined to determine the emphasis of reactance analysis. Based on the difference between the equivalent capacitance at the input and output ends and the emphasis of reactance analysis, the reactance operating condition risk is derived. A short-circuit warning coefficient is determined from the target power factor anomaly and the reactance operating condition risk. The difference between the short-circuit warning coefficient and the average short-circuit warning coefficient of all reactors in the power system is then used as the short-circuit warning index, achieving early warning of inter-turn short circuits. This significantly improves the operational safety of dry-type air-core reactors under complex operating conditions compared to traditional single power factor threshold judgment.

[0161] It should be understood that, although Figure 1 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 1 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0162] This application also provides an early alarm system for inter-turn short circuits in dry-type air-core reactors based on power factor, such as... Figure 2 As shown, the system includes:

[0163] The calculation module 21 is used to calculate the power factor anomaly of the reactor based on the negative correlation between the load state coefficient of each phase and the corresponding power factor; the load state coefficient of each phase is obtained based on the ratio of the operating current of each phase to the corresponding rated current.

[0164] The first determining module 22 is used to determine the focus of the reactance analysis based on the uniformity of the magnetic field kurtosis of the reactor coil and the correlation between the temperature change and the current change of the reactor coil during the first historical period.

[0165] The second determining module 23 is used to determine the risk level of the reactor operating condition based on the difference between the equivalent capacitance at the input end and the equivalent capacitance at the output end of the reactor and the emphasis of the reactor analysis.

[0166] The third determining module 24 is used to determine the short-circuit warning coefficient of the reactor based on the target power factor anomaly and the reactor operating condition risk; wherein, the target power factor anomaly is obtained by correcting the power factor anomaly based on the change of the power factor of each phase of the reactor during the first historical period;

[0167] The fourth determining module 25 is used to determine the short-circuit warning index of the reactor based on the difference between the short-circuit warning coefficient of the reactor and the average short-circuit warning coefficient of all reactors in the power system to which the reactor belongs, so as to perform short-circuit warning based on the short-circuit warning index.

[0168] For the system embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this application according to actual needs.

[0169] Figure 3 This is a schematic diagram of the structure of an electronic device according to an example embodiment of this application. The electronic device includes a memory, a processor, and a computer program stored in the memory and used to run on the processor. When the processor executes the computer program, it implements the method described in any of the above embodiments. Figure 3 The electronic device 30 shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of this application.

[0170] like Figure 3 As shown, the electronic device 30 can be manifested as a general-purpose computing device, such as a server device. The components of the electronic device 30 may include, but are not limited to: at least one processor 31, at least one memory 32, and a bus 33 connecting different system components (including memory 32 and processor 31).

[0171] Bus 33 includes a data bus, an address bus, and a control bus.

[0172] The memory 32 may include volatile memory, such as random access memory (RAM) 321 and / or cache memory 322, and may further include read-only memory (ROM) 323.

[0173] The memory 32 may also include a program tool 325 (or utility) having a set (at least one) program module 324, such program module 324 including but not limited to: an operating system, one or more application programs, other program modules and program data, each or some combination of these examples may include an implementation of a network environment.

[0174] The processor 31 executes various functional applications and data processing, such as the methods provided in any of the above embodiments, by running computer programs stored in the memory 32.

[0175] Electronic device 30 can also communicate with one or more external devices 34 (e.g., keyboard, pointing device, etc.). This communication can be performed via input / output (I / O) interface 35. Furthermore, electronic device 30 can also communicate with one or more networks (e.g., local area network (LAN), wide area network (WAN), and / or public network, such as the Internet) via network adapter 36. As shown, network adapter 36 communicates with other modules of electronic device 30 via bus 33. It should be understood that, although not shown in the figure, other hardware and / or software modules can be used in conjunction with electronic device 30, including but not limited to: microcode, device drivers, redundant processors, external disk drive arrays, RAID (disk array) systems, tape drives, and data backup storage systems.

[0176] It should be noted that although several units / modules or sub-units / modules of the electronic device have been mentioned in the detailed description above, this division is merely exemplary and not mandatory. In fact, according to the embodiments of this application, the features and functions of two or more units / modules described above can be embodied in one unit / module. Conversely, the features and functions of one unit / module described above can be further divided and embodied by multiple units / modules.

[0177] This application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method provided in any of the above embodiments.

[0178] The readable storage medium may be more specifically adopted, including but not limited to: portable disk, hard disk, random access memory, read-only memory, erasable programmable read-only memory, optical storage device, magnetic storage device, or any suitable combination thereof.

[0179] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0180] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the method described in any of the above embodiments.

[0181] The program code for executing the computer program product of this application can be written in any combination of one or more programming languages. The program code can be executed entirely on the user device, partially on the user device, as a standalone software package, partially on the user device and partially on a remote device, or entirely on a remote device.

[0182] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0183] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application.

[0184] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for early alarm of inter-turn short circuit in a dry-type air-core reactor based on power factor, characterized in that, The method includes: The power factor anomaly of the reactor is calculated based on the negative correlation between the load state factor of each phase and the corresponding power factor; the load state factor of each phase is obtained based on the ratio of the operating current of each phase to the corresponding rated current. The focus of the reactance analysis is determined based on the uniformity of the magnetic field kurtosis of the reactor coil and the correlation between the temperature change and current change of the reactor coil during the first historical period. The risk level of reactor operating conditions is determined based on the difference between the equivalent capacitance at the input end and the equivalent capacitance at the output end of the reactor, and the emphasis of the reactor analysis. The short-circuit warning coefficient of the reactor is determined based on the target power factor anomaly and the reactor operating condition risk. The target power factor anomaly is obtained by correcting the power factor anomaly based on the changes in the power factor of each phase of the reactor during the first historical period. The short-circuit warning index of the reactor is determined based on the difference between the short-circuit warning coefficient of the reactor and the mean of the short-circuit warning coefficients of all reactors in the power system to which the reactor belongs, so as to carry out short-circuit warning based on the short-circuit warning index; The emphasis of reactance analysis is determined based on the uniformity of the magnetic field kurtosis of the reactor coil and the correlation between temperature and current changes in the reactor coil during the first historical period, including: Screening multiple sets of axisymmetric points on the coil of the reactor; The magnetic field kurtosis ratio of the reactor is determined by the sum of the magnetic field kurtosis of multiple axisymmetric points on the reactor coil and the mean of the sum of the magnetic field kurtosis of multiple axisymmetric points at multiple moments during the second historical period that are the same as the mean of the load state coefficient of the three phases. For each group of axisymmetric points, calculate the absolute difference in magnetic field kurtosis between the two points in that group of axisymmetric points to obtain the magnetic field kurtosis deviation coefficient of that group of axisymmetric points. Calculate the mean value of the magnetic field kurtosis deviation coefficient for multiple sets of axisymmetric points to obtain the mean value of the magnetic field kurtosis deviation coefficient; The electromagnetic field uniformity of a reactor is obtained by multiplying the kurtosis ratio of its magnetic field by the mean value of its magnetic field kurtosis deviation coefficient. The electromagnetic field uniformity indicates the degree of uniformity of the spatial distribution of the magnetic field inside the reactor. The focus of the reactance analysis is determined based on the electromagnetic field uniformity of the reactor and the correlation between the temperature and current changes of the reactor coil during the first historical period.

2. The method for early alarm of inter-turn short circuit in dry-type air-core reactors based on power factor as described in claim 1, characterized in that, The calculation of the power factor anomaly of the reactor based on the negative correlation between the load state coefficient of each phase of the reactor and the corresponding power factor includes: The load state factor of each phase is determined by the ratio of the operating current of each phase of the reactor to the corresponding rated current. Calculate the difference between the power factor and the mean power factor for each phase of the reactor to obtain the first power factor difference for that phase; the mean power factor indicates the mean power factor of the three phases of the reactor. The power factor consistency coefficient of the reactor is obtained by calculating the reciprocal of the sum of the power factor differences of the three phases of the reactor; the power factor consistency coefficient indicates the degree of consistency of the power factor among the three phases of the reactor. Within the second historical period, determine multiple moments when the historical load factor of each phase is the same as the load state factor of that phase, and calculate the average historical power factor of that phase at multiple moments to obtain the average historical power factor of that phase; wherein, the second historical period is longer than the first historical period; Calculate the difference between the power factor of each phase and the historical average power factor of that phase to obtain the second power factor difference value of that phase, and calculate the sum of the second power factor differences of the three phases of the reactor to obtain the historical power factor difference value of the reactor; The power factor anomaly of the reactor is calculated based on the historical power factor difference, the power factor consistency coefficient, and the load state coefficient of each phase of the reactor. The power factor anomaly indicates the degree of deviation of the reactor's power factor from the power factor under the same historical load conditions.

3. The method for early alarm of inter-turn short circuit in dry-type air-core reactors based on power factor as described in claim 2, characterized in that, The calculation of the power factor anomaly of the reactor based on the historical power factor difference, the power factor consistency coefficient, and the load state coefficient of each phase of the reactor includes: The anomalous factor of the reactor is determined by the ratio of the historical power factor difference of the reactor to the power factor consistency coefficient of the reactor. A coordinate system is established with the historical load state coefficient of each phase in the first historical period as the vertical axis and multiple moments in the first historical period as the horizontal axis. The points in the coordinate system are then fitted using the least squares straight line fitting method to obtain the historical load state coefficient curve of that phase. A coordinate system is established with the historical power factor of each phase in the first historical period as the vertical axis and multiple moments in the first historical period as the horizontal axis. The points in the coordinate system are fitted using the least squares linear fitting method to obtain the historical power factor curve of that phase. Calculate the absolute value of the Pearson correlation coefficient between the historical load state coefficient curve and the historical power factor curve of each phase to obtain the negative correlation of that phase. Then calculate the sum of the negative correlations of the three phases of the reactor to obtain the superimposed value of the negative correlation of the reactor. The power factor anomaly of the reactor is determined by the ratio of the anomaly factor of the reactor to the superimposed value of the negative correlation.

4. The method for early alarm of inter-turn short circuit in dry-type air-core reactors based on power factor as described in claim 1, characterized in that, The emphasis of reactance analysis is determined based on the electromagnetic field uniformity of the reactor and the correlation between the temperature and current changes of the reactor coil during the first historical period, including: A coordinate system is established with the sum of the three-phase currents of the reactor in the first historical period as the vertical axis and multiple moments in the first historical period as the horizontal axis. The points in the coordinate system are fitted using the least squares linear fitting method to obtain the historical current curve. A coordinate system is established with the coil temperature of the reactor in the first historical period as the vertical axis and multiple moments in the first historical period as the horizontal axis. The points in the coordinate system are then fitted using the least squares linear fitting method to obtain the historical temperature curve. Calculate the Pearson correlation coefficient between the historical current curve and the historical temperature curve to obtain the current-temperature correlation coefficient; Calculate the sum of the slopes of the historical current curve and the historical temperature curve to obtain the slope sum value; The emphasis of reactance analysis is determined based on the current-temperature correlation coefficient, slope and value, and electromagnetic field uniformity.

5. The method for early alarm of inter-turn short circuit in dry-type air-core reactors based on power factor as described in claim 1, characterized in that, The determination of the reactor operating condition risk level based on the difference between the equivalent capacitance at the reactor's input and output terminals, and the emphasis of the reactor analysis, includes: The reactive power compensation performance of the reactor is determined by the difference between the equivalent capacitance at the input terminal and the equivalent capacitance at the output terminal. The reactor operating condition risk level is determined by the ratio of the emphasis of reactance analysis to the performance of reactive power compensation; the reactor operating condition risk level indicates the degree of abnormality in the reactor's operating condition caused by short-circuit faults.

6. The method for early alarm of inter-turn short circuit in a dry-type air-core reactor based on power factor as described in claim 1, characterized in that, Before determining the short-circuit warning coefficient of the reactor based on the target power factor anomaly and the reactor operating condition risk, the following steps are also included: A coordinate system is established with the historical power factor of each phase in the first historical period as the vertical axis and multiple moments in the first historical period as the horizontal axis. The points in the coordinate system are fitted using the least squares linear fitting method to obtain the historical power factor curve of that phase. A coordinate system is established with the historical power factor of each phase within the target historical period as the vertical axis and multiple moments within the target historical period as the horizontal axis. The points in the coordinate system are fitted using the least squares linear fitting method to obtain the target historical power factor curve of that phase. The target historical period indicates the period within the second historical period that is at the same historical moment as the current moment and lasts for a preset duration. The correction coefficient is obtained by calculating the ratio of the mean slope of the three-phase historical power factor curves to the mean slope of the three-phase target historical power factor curves. The power factor anomaly is corrected based on the correction factor to obtain the target power factor anomaly.

7. The method for early alarm of inter-turn short circuit in a dry-type air-core reactor based on power factor as described in claim 6, characterized in that, The determination of the short-circuit warning coefficient of the reactor based on the anomaly of the target power factor and the risk of reactor operating conditions includes: The short-circuit warning coefficient of the reactor is determined by multiplying the risk level of the reactor operating condition by the anomaly level of the target power factor.

8. The method for early alarm of inter-turn short circuit in a dry-type air-core reactor based on power factor as described in claim 1, characterized in that, The determination of the short-circuit warning index of the reactor based on the difference between the short-circuit warning coefficient of the reactor and the average short-circuit warning coefficient of all reactors in the power system to which the reactor belongs includes: The short-circuit warning coefficient of the reactor is calculated by the difference between the short-circuit warning coefficient of the reactor and the mean of the short-circuit warning coefficients of all reactors in the power system to which the reactor belongs, and the short-circuit warning index of the reactor is determined.

9. The method for early alarm of inter-turn short circuit in a dry-type air-core reactor based on power factor as described in claim 1, characterized in that, After determining the short-circuit warning index of the reactor based on the difference between the short-circuit warning coefficient of the reactor and the average short-circuit warning coefficient of all reactors in the power system to which the reactor belongs, the method further includes: If the short-circuit warning index of the reactor is greater than the preset index, it is determined that there is a short-circuit risk in the reactor and a power disconnection warning is issued.

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