Dry-type air-core reactor turn-to-turn short circuit fault detection method based on resonance wave peak average offset

Abstract

The invention discloses a dry-type air-core reactor turn-to-turn short circuit fault detection method based on the average offset of resonance wave crests, and the method comprises the steps: constructing a circuit model of a dry-type air-core reactor to simulate normal operation and turn-to-turn short circuits at different fault degrees and fault positions, and obtaining a corresponding impedance logarithmic amplitude spectrum; respectively calculating the resonance wave crest offset and the characteristic value of the impedance logarithmic amplitude spectrum corresponding to each turn-to-turn short circuit; obtaining an impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be detected, and calculating a resonance wave crest offset and a characteristic value; and if the resonance wave crest offset is greater than the preset threshold value, matching the resonance wave crest offset and the characteristic value with the resonance wave crest offset and the characteristic value of the impedance logarithmic amplitude spectrum corresponding to each turn-to-turn short circuit, and determining the turn-to-turn short circuit fault position and fault degree of the to-be-detected dry-type air-core reactor according to the matching result. According to the invention, the accuracy of turn-to-turn short circuit fault detection of the dry-type reactor is improved, and the safe operation of the dry-type air-core reactor is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of dry-type air-core reactors, and in particular to a method for detecting inter-turn short-circuit faults of dry-type air-core reactors based on an average offset of a resonance wave peak. Background Art

[0002] With the continuous advancement of domestic power infrastructure, UHV and EHV power grids have also continued to expand. High-quality, high-tech transmission equipment, including reactors, has become an indispensable and important component to support the development of power grids. At the same time, the level of my country's UHV power grid continues to improve, and the requirements for the safe and stable operation of reactors are getting higher and higher. With the large-scale commissioning and long-term operation of dry air-core reactors, their failure rate continues to increase, of which 70% are caused by turn-to-turn short-circuit faults. However, the existing monitoring methods cannot detect turn-to-turn short-circuit faults in time, which can easily lead to the burning of reactors and cause more serious ground short-circuit faults, threatening the safe and stable operation of the power system.

[0003] At present, the main online detection technologies for short-circuit faults between turns of reactors include: temperature field detection, magnetic field detection, electrical parameter detection, etc. For example, optical fiber temperature sensing technology, infrared temperature measurement technology, etc. Although the temperature measurement method is very convenient, the existing technology can only work for monitoring points within a specific range, and cannot sensitively detect the temperature changes of monitoring points beyond the measurement range. Regarding magnetic field detection, it is limited by the accuracy of the installed external sensor, and the magnetic field generated during the fault will weaken the original magnetic field, resulting in a certain error. For electrical parameter detection, in the early stage of the fault, the electrical parameters such as inductance and resistance of the reactor change very little, and the reliability of reflecting the fault information through the transformation of these electrical parameters is poor; it is technically feasible to use high-frequency pulse oscillation method to perform inter-turn insulation test of dry hollow shunt reactors, but this method needs to be carried out under the condition of power failure of the reactor, and the timeliness of winding insulation fault diagnosis is poor. Summary of the invention

[0004] The technical problem to be solved by the present invention is as follows: the fault characteristic quantities detected in the existing dry-type air-core reactor protection scheme are only applicable at low frequencies, but when the frequency increases to high frequencies, some characteristic quantities will not be able to detect and eliminate the inter-turn short-circuit fault of the dry-type air-core reactor, causing the fault to evolve into a ground short-circuit fault or a more serious fire accident, affecting the safe and stable operation of the power system.

[0005] In view of the above problems in the prior art, a method for detecting inter-turn short-circuit faults of dry-type air-core reactors based on the average offset of the resonant wave peak is proposed, which improves the accuracy of inter-turn short-circuit fault detection of dry-type reactors, avoids further expansion of accidents, ensures the safe operation of dry-type air-core reactors, and ensures the sensitivity and reliability of inter-turn short-circuit fault detection.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for detecting inter-turn short-circuit faults in dry-type air-core reactors based on the average offset of resonance peaks:

[0008] Constructing a circuit model of a dry-type air-core reactor, using the circuit model to simulate the normal operation of the dry-type air-core reactor and turn-to-turn short circuits with different fault degrees and fault locations, and obtaining corresponding impedance logarithmic amplitude spectra;

[0009] Calculate the resonance peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each turn-to-turn short circuit of the dry-type air-core reactor respectively, wherein the resonance peak offset specifically refers to the offset of the resonance peak of the impedance logarithmic amplitude spectrum compared with the resonance peak of the impedance logarithmic amplitude spectrum when the dry-type air-core reactor is operating normally;

[0010] Obtaining an impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested, and calculating a resonant peak offset and a characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested;

[0011] If the resonant peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested is greater than a preset threshold, the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested are matched with the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each turn-to-turn short circuit, and the turn-to-turn short circuit fault location and fault degree of the dry-type air-core reactor to be tested are determined according to the matching result.

[0012] Furthermore, constructing a circuit model of a dry-type air-core reactor specifically includes the following steps:

[0013] Establish the distributed equivalent circuit model of the reactor at high frequency, calculate the inter-turn capacitance, inter-layer capacitance and stray capacitance to the ground, coil self-inductance and mutual inductance;

[0014] For any node i in the distributed equivalent circuit model of the reactor, write the Kirchhoff current law equation, then write the voltage and current equations of the inductor and resistor branches adjacent to the node i, and organize them into the form of an admittance matrix, so that after the node voltage and current are obtained, the inverse of the admittance matrix is ​​calculated to obtain the impedance value.

[0015] Furthermore, the expression of the admittance matrix form is as follows:

[0016] [Y] · [ΔU + U'] = [I]

[0017] Where [Y] is the admittance matrix of the equivalent circuit model, ΔU represents the node voltage difference, and U' represents the mutual inductance voltage drop.

[0018] Further, when respectively calculating the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each inter-turn short circuit of the dry-type air-core reactor, the step of calculating the resonant peak offset of the impedance logarithmic amplitude spectrum includes:

[0019] Get the frequency f corresponding to the maximum value of the resonance peak in the impedance logarithmic amplitude spectrum of the dry-type air-core reactor during normal operation M The frequencies f1, f2, ... f corresponding to other resonance peaks n ;

[0020] Get the frequency f corresponding to the maximum value of the resonant peak in the impedance logarithmic amplitude spectrum corresponding to the current inter-turn short circuit M 'The frequencies corresponding to other resonance peaks are f1', f2'...f n ';

[0021] Calculate the frequency f corresponding to the maximum value of the resonant peak in the impedance logarithmic amplitude spectrum corresponding to the current inter-turn short circuit M 'Relative to frequency f M The offset Δf M , and calculate the frequencies f1', f2'...f corresponding to other resonant peaks in the impedance logarithmic amplitude spectrum corresponding to the current inter-turn short circuit n 'Relative to the frequencies f1, f2...f n The offset Δf1, Δf2...Δf n , calculate the offset Δf M , Δf1, Δf2...Δf n The average value of the resonance peak offset Δf corresponding to the current inter-turn short circuit is obtained.

[0022] Further, when respectively calculating the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each inter-turn short circuit of the dry-type air-core reactor, the step of calculating the characteristic value of the impedance logarithmic amplitude spectrum includes:

[0023] The absolute value of the impedance logarithmic amplitude spectrum waveform corresponding to the current turn-to-turn short circuit is integrated to obtain the corresponding characteristic waveform, and the change trend of the specified position of the characteristic waveform is calculated to obtain the characteristic value corresponding to the current turn-to-turn short circuit.

[0024] Further, when calculating the change trend of the specified position of the characteristic waveform, it includes:

[0025] Obtaining the inflection point value A1 of the first stage in the characteristic waveform, and the step stability values ​​A2 and A3 of the second stage and the third stage in the characteristic waveform;

[0026] The ratio of the stable value A2 at the step in the second stage to the inflection point value A1 in the first stage is calculated as the first eigenvalue K1 corresponding to the current turn-to-turn short circuit, and the ratio of the stable value A3 at the step in the third stage to the stable value A2 at the step in the second stage is calculated as the second eigenvalue K2 corresponding to the current turn-to-turn short circuit.

[0027] Further, after respectively calculating the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each inter-turn short circuit of the dry-type air-core reactor, the method includes: dividing the resonant peak offset intervals of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuits of different fault degrees according to the value of the resonant peak offset, and constructing a set of resonant peak offsets of the corresponding impedance logarithmic amplitude spectrum for the inter-turn short circuits of different fault positions under the same fault degree;

[0028] The characteristic values ​​of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuits with different fault degrees are fitted to obtain the characteristic value change trends of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuits with different fault degrees.

[0029] Further, when matching the resonance peak offset and characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested with the resonance peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each turn-to-turn short circuit, it includes:

[0030] The resonance peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested is matched with the resonance peak offset interval of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuit of different fault degrees, and the corresponding inter-turn short circuit fault degree is determined according to the matching result;

[0031] Compare the characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested with the characteristic value change trend of the impedance logarithmic amplitude spectrum corresponding to the determined inter-turn short-circuit fault degree; if the characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested matches the characteristic value change trend of the impedance logarithmic amplitude spectrum corresponding to the determined inter-turn short-circuit fault degree, then the inter-turn short-circuit fault degree of the dry-type air-core reactor to be tested is the determined inter-turn short-circuit fault degree;

[0032] The resonance peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested is matched with the set of resonance peak offsets of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuit at different fault positions in the determined inter-turn short circuit fault degree, and the corresponding inter-turn short circuit fault position is determined according to the matching result.

[0033] Furthermore, when obtaining the impedance logarithmic amplitude spectrum of the dry-type air-core inductor to be tested, it includes: real-time acquisition of the frequency parameter measurement value of the resonant point in the impedance logarithmic amplitude spectrum and preprocessing, and then comparing it with the corresponding frequency parameter simulation value in the circuit model to determine whether the frequency parameter measurement value belongs to an abnormal point, if so, discard the corresponding data, otherwise retain the corresponding data.

[0034] The present invention also proposes a dry-type air-core reactor turn-to-turn short-circuit fault detection system based on the average offset of the resonance wave peak, comprising a microprocessor and a computer-readable storage medium connected to each other, wherein the microprocessor is programmed or configured to execute any of the dry-type air-core reactor turn-to-turn short-circuit fault detection methods based on the average offset of the resonance wave peak.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] The present invention selects the average offset of the resonance peak in the impedance amplitude spectrum to determine the degree of the inter-turn short-circuit fault of the dry-type air-core reactor, and defines a characteristic value for auxiliary determination, thereby analyzing the high-frequency characteristics of the reactor and ensuring the sensitivity and reliability of the inter-turn short-circuit fault detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The following is a brief flowchart of a method according to an embodiment of the present invention.

[0038] Figure 2 The following is a detailed flow chart of a method according to an embodiment of the present invention.

[0039] Figure 3 It is a simulation model established in the embodiment of the present invention.

[0040] Figure 4 It is the logarithmic amplitude spectrum of the reactor impedance under normal operating conditions.

[0041] Figure 5 It is the logarithmic amplitude spectrum of the inter-turn short-circuit impedance of different degrees at the head end.

[0042] Figure 6 It is the logarithmic amplitude spectrum of the inter-turn short-circuit impedance of different degrees at the middle end.

[0043] Figure 7 It is the logarithmic amplitude spectrum of the inter-turn short-circuit impedance at different degrees at the end.

[0044] Figure 8 Impedance log magnitude spectrum for 10% inductance reduction at different locations.

[0045] Fig. 9 It is a schematic diagram of features A1, A2, and A3 in the characteristic waveform of the impedance logarithmic amplitude spectrum.

[0046] Fig.10 It is the characteristic waveform of the impedance logarithmic amplitude spectrum with different degrees of inter-turn short circuit at the head end.

[0047] Fig.11 The waveform characteristic value changes with the severity of the inter-turn short circuit. DETAILED DESCRIPTION

[0048] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0049] Embodiment 1

[0050] In order to solve the problems existing in the existing reactor inter-turn short-circuit detection technology, this embodiment proposes a dry-type air-core reactor inter-turn short-circuit fault detection method based on the average offset of the resonant wave peak, establishes a high-frequency distributed parameter equivalent model of the reactor based on the multi-conductor transmission line theory, and builds a simulink circuit model to simulate the reactor when inter-turn short-circuit faults of different degrees occur at high frequency. According to the simulation results, the resonant wave peak offset and characteristic value of the impedance logarithmic amplitude spectrum of the inter-turn short circuit with different fault degrees and fault locations are statistically analyzed. Subsequently, the resonant wave peak offset and characteristic value of the impedance logarithmic amplitude spectrum of the measured data of the dry-type air-core reactor are matched with the statistical results to determine whether the dry-type air-core reactor has inter-turn short-circuit faults of different degrees.

[0051] like Figure 1 As shown, the method of this embodiment includes the following steps:

[0052] S1) constructing a circuit model of a dry-type air-core reactor;

[0053] S2) using the circuit model to simulate the normal operation of the dry-type air-core reactor and the turn-to-turn short circuits with different fault degrees and fault locations, and obtaining the corresponding impedance logarithmic amplitude spectrum, respectively calculating the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each turn-to-turn short circuit of the dry-type air-core reactor. In this embodiment, the resonant peak offset specifically refers to the offset of the resonant peak of the impedance logarithmic amplitude spectrum compared to the resonant peak of the impedance logarithmic amplitude spectrum when the dry-type air-core reactor is operating normally, and the characteristic value specifically refers to the change trend of a specified position in a characteristic waveform obtained by integrating the impedance logarithmic amplitude spectrum;

[0054] S3) obtaining an impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested, and calculating a resonant peak offset and a characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested;

[0055] S4) if the resonance peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested is less than a preset threshold value, it indicates that no turn-to-turn short-circuit fault occurs;

[0056] If the resonant peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested is greater than a preset threshold, it indicates that a turn-to-turn short-circuit fault has occurred. The resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested are matched with the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each turn-to-turn short circuit. The turn-to-turn short-circuit fault location and fault degree of the dry-type air-core reactor to be tested are determined according to the matching result.

[0057] Combine the following Figure 2 Each step is described in detail.

[0058] Step S1 of this embodiment establishes a high-frequency distributed parameter equivalent model of the reactor based on the multi-conductor transmission line theory and builds a simulink circuit model to simulate the reactor when inter-turn short-circuit faults of different degrees occur at high frequencies, specifically including the following steps:

[0059] Firstly, based on the multi-conductor transmission line theory, the distributed equivalent circuit model of the reactor at high frequency is established. To simplify the analysis, the number of coil layers of the dry-type air-core reactor is set to x, and each coil layer is divided into y parts along the height direction. The values ​​of the inter-turn capacitance, the capacitance between each layer and the stray capacitance to the ground are calculated theoretically, and the self-inductance and mutual inductance of the coil are calculated according to the inductance calculation model of the coaxial thin-walled solenoid.

[0060] Then, write the Kirchhoff current law equation for any node i in the reactor distribution equivalent circuit model, and write the voltage and current equation of the inductor resistance branch adjacent to the node i, which is organized into the form of an admittance matrix as shown below:

[0061] [Y] · [ΔU + U'] = [I]

[0062] Among them, ΔU represents the node voltage difference, U' represents the mutual inductance voltage drop, and [Y] is the admittance matrix of (R+jωL). Its inductance value is related to the change of frequency. With the increase of frequency, the change of mutual inductance coefficient is much greater than that of self-inductance. When a turn-to-turn short circuit fault occurs, the inductance value drops significantly, and the impedance value changes significantly.

[0063] Based on the above content, after obtaining the voltage of each node, because the voltage drop of the reactor is distributed according to the capacitance at high frequency, its current will increase numerically due to the decrease of the capacitive reactance. After the node voltage and current are obtained, the impedance value can be obtained, that is, the inverse of the admittance matrix. Further taking the logarithm of the impedance value makes the conclusion easy to observe. Plotting the curve of the impedance value changing with frequency under the circuit model of the dry air-core reactor obtains the characteristic curve of the impedance logarithmic amplitude spectrum with respect to frequency. This curve can be obtained by simulink simulation calculation. The simulink circuit model of the high-frequency distributed parameter equivalent model of the reactor is as follows Figure 3 shown.

[0064] like Figure 2As shown, step S2 of this embodiment is mainly divided into two stages, namely, pre-processing and real-time processing. The pre-processing stage is to obtain the frequency parameters of the resonance point of the standard impedance logarithmic amplitude spectrum of the dry-type reactor in the normal operating state in the set frequency range; in the real-time stage, when the reactor is running, the frequency parameters of the resonance point of the impedance logarithmic amplitude spectrum under different fault degrees when the inductance value decreases by 5%, the inductance value decreases by 10%, the inductance value decreases by 15%, and the inductance value decreases by 20% are obtained in real time, and the average offset of the resonance wave peak under different fault degrees is calculated, and the fault is judged by comparing with the set value.

[0065] In step S2 of this embodiment, when respectively calculating the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each turn-to-turn short circuit of the dry-type air-core reactor, the step of calculating the resonant peak offset of the impedance logarithmic amplitude spectrum includes:

[0066] S21) Obtain the frequency f corresponding to the maximum value of the resonance peak in the impedance logarithmic amplitude spectrum when the dry-type air-core reactor is operating normally M The frequencies f1, f2, ... f corresponding to other resonance peaks n ;

[0067] In this embodiment, the logarithmic amplitude spectrum of the impedance of the normal operating reactor under simulation is obtained as follows: Figure 4 As shown. As the frequency increases, the inductive reactance increases and the capacitive reactance decreases, and the internal circuit of the reactor resonates in series and parallel. In the frequency band where the equivalent circuit resonates, the inductive reactance and the capacitive reactance counteract each other and are very sensitive to parameter changes. Therefore, the frequency band of 100HZ~100MHZ when the overall circuit resonates should be selected as the starting range of the frequency sweep. The impedance logarithmic amplitude spectrum has a rapid change. Figure 4 In the figure, the frequency of 21.38 MHZ is the maximum value of the resonance peak. When the frequency of the sweep frequency continues to increase, it shows a downward trend. The frequency of the maximum value of the resonance peak of the normal impedance spectrum is taken as f M , take the frequencies corresponding to other resonance peaks as f1, f2...f n It can be seen that the resonant point frequency in the amplitude spectrum is very sensitive to the change of electrical parameters. Therefore, the impedance logarithmic amplitude spectrum can be used to analyze the operating state of the reactor.

[0068] S22) Obtain the frequency f corresponding to the maximum value of the resonance peak in the impedance logarithmic amplitude spectrum corresponding to the current inter-turn short circuit M 'The frequencies corresponding to other resonance peaks are f1', f2'...f n ';

[0069] S23) Calculate the frequency f corresponding to the maximum value of the resonance peak in the impedance logarithmic amplitude spectrum corresponding to the current inter-turn short circuit M 'Relative to frequency f M The offset Δf M, and calculate the frequencies f1', f2'...f corresponding to other resonant peaks in the impedance logarithmic amplitude spectrum corresponding to the current inter-turn short circuit n 'Relative to the frequencies f1, f2...f n The offset Δf1, Δf2...Δf n , calculate the offset Δf M , Δf1, Δf2...Δf n The average value of the resonance peak offset Δf corresponding to the current inter-turn short circuit is obtained.

[0070] In this embodiment, when simulating the inter-turn short circuit of the dry-type air-core reactor with different fault degrees and fault locations, the head end is first set to have an inter-turn short circuit, and the impedance logarithmic amplitude spectrum is obtained when the inductance value decreases by 5%, 10%, 15%, and 20%, as shown in FIG. Figure 5 As shown in the figure, the frequency f corresponding to the new resonance peak when the inductance value of the reactor turns short-circuit fault decreases is measured. M ', f1', f2'...f n ', calculate the offset Δf of the peak maximum value at the resonance point M , and then arbitrarily calculate the peak offset of other resonant point frequencies Δf1, Δf2...Δf n , take the average value of two or more corresponding frequency offsets as the characteristic quantity to measure the inter-turn short-circuit fault of the reactor; when the first-end inter-turn short-circuit occurs in the reactor, the peak values ​​of the resonance point will shift to the right, and the more serious the fault is, the greater the offset will be.

[0071] In this embodiment, taking into account that when an inter-turn short circuit actually occurs, the amount of inductance decrease may not be exactly equal to the decrease set during simulation, therefore, after calculating the value of the resonant peak offset of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuits of different fault degrees, the resonant peak offset intervals of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuits of different fault degrees are divided.

[0072] The following Table 1 shows the statistical value of the average offset of the resonance point of the inter-turn fault at the head end of the reactor, and then gives the setting value of the resonance peak offset interval corresponding to the inter-turn short circuit of different fault degrees. When the average change rate of the offset of the resonance peak is measured as 0<Δf<2MHZ, it is determined that a slight inter-turn short circuit fault occurs in the dry-type reactor to be tested (the inductance value decreases by 0-5%); when the average change rate of the offset of the resonance peak is measured as 2<Δf<20MHZ, it is determined that a relatively serious inter-turn short circuit fault occurs in the dry-type reactor to be tested (the inductance value decreases by 5%-15%); when the average change rate of the offset of the resonance peak is measured as Δf>20MHZ, it is determined that a serious inter-turn short circuit fault occurs in the dry-type reactor to be tested (the inductance value decreases by more than 15%).

[0073] Table 1 Statistical values ​​of average offset of inter-turn fault resonance point at the first end of the reactor

[0074]

[0075] Similarly, the resonance point frequency characteristic curves in the impedance logarithmic amplitude spectrum of different fault degrees at the fault location in the middle of the reactor and at the end of the reactor can be measured, as shown in Figure 2. Figure 6 and Figure 7 To further explore the relationship between the fault location and the operating state of the reactor, this embodiment also establishes a set of offsets of the resonant peaks of the impedance logarithmic amplitude spectrum for turn-to-turn short circuits at different fault locations under the same fault degree, that is, the fault locations are respectively set at the first layer of the reactor (the beginning of the reactor), the second layer of the reactor (the middle of the reactor), and the fourth layer of the reactor (the end of the reactor), and the offsets of the resonant point peaks in the impedance logarithmic amplitude spectrum at different positions under the same fault degree are obtained, for example Figure 8 To explore the impedance logarithmic amplitude spectrum when the inductance is reduced by 10% at different positions.

[0076] Since the actual measurement may be affected by external noise and other interference factors and measurement errors, the average offset of the fault resonance point measured above may change slightly. For example, when the number of short-circuit turns is small, the slight difference between the resonance peaks in the impedance logarithmic amplitude spectrum may also cause misjudgment due to on-site interference in actual detection, and it is necessary to combine the set auxiliary criteria. Therefore, this embodiment also constructs a characteristic waveform by integrating the absolute value of the impedance logarithmic amplitude spectrum waveform, thereby improving the identifiability of the inter-turn short circuit. In step S2, when respectively calculating the resonance peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each inter-turn short circuit of the dry-type air-core reactor, it includes the step of calculating the characteristic value of the impedance logarithmic amplitude spectrum, specifically including:

[0077] The absolute value of the impedance logarithmic amplitude spectrum waveform corresponding to the current turn-to-turn short circuit is integrated to obtain the corresponding characteristic waveform, and the change trend of the specified position of the characteristic waveform is calculated to obtain the characteristic value corresponding to the current turn-to-turn short circuit.

[0078] The characteristic waveform obtained by integrating the absolute value of the impedance logarithmic amplitude spectrum waveform is as follows: Fig. 9 As shown in the figure, the first stage shows an upward trend. Due to the similarity of the characteristic waveforms of normal situation and the inter-turn short circuit of different fault degrees at the same fault location (such as Fig.10As shown), if the change of the characteristic waveform amplitude is directly used to determine whether a turn-to-turn short-circuit fault occurs in the dry-type air-core reactor, it may lead to misjudgment. It is necessary to extract characteristic values ​​from it to highlight the difference in the detection results under different insulation states. In this embodiment, the characteristic value is obtained by calculating the change trend of the specified position of the characteristic waveform, that is, the two characteristic values ​​K1 and K2 of the characteristic waveform are defined as follows, wherein A1 is defined as the inflection point value of the first stage, A2 and A3 are respectively the stable values ​​of the characteristic waveform at the steps of the second and third stages, and the characteristic values ​​K1 and K2 of the characteristic waveform are calculated, and the expression is as follows:

[0079] K1=A2 / A1

[0080] K2=A3 / A2

[0081] In this embodiment, after calculating the characteristic values ​​of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuit with different fault degrees and different fault positions, the characteristic values ​​of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuit with different fault degrees are fitted to analyze its change trend, such as Fig.11 shown.

[0082] Depend on Fig.11 It can be seen that when the reactor has different degrees of inter-turn short-circuit faults, its characteristic waveforms K1 and K2 will show a trend of first increasing and then decreasing, and a peak value appears when the inductance value decreases by 10%, and it has a rapid change. The slope of the characteristic waveform curve is steep, indicating that the characteristic value change trend can be used to assist in the diagnosis of the degree of inter-turn short-circuit faults of the reactor.

[0083] Therefore, in order to more accurately detect the insulation level and operating status of the reactor, this embodiment uses the change trend of the characteristic value waveform for auxiliary judgment. The change of the waveform characteristic value K1 and K2 with the severity of the short circuit is as follows: Fig.11 As shown, the fault degree is determined as a slight turn-to-turn short-circuit fault, a relatively serious turn-to-turn short-circuit fault, or a severe turn-to-turn short-circuit fault according to the average change rate of the resonant wave peak offset of the reactor to be tested, and a warning / removal signal can be issued only when the distribution change law of the K1 and K2 characteristic values ​​under the corresponding fault degree is met.

[0084] Steps S3 and S4 of this embodiment are based on steps S1 and S2, and turn-to-turn short-circuit fault detection is performed on the measured data of the dry-type air-core reactor to be tested. Specifically, step S3 of this embodiment includes the following steps:

[0085] S31) Obtaining the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested: After the dry-type air-core reactor to be tested is put into operation, the frequency parameter measurement value of the resonance point of the impedance logarithmic amplitude spectrum is collected in real time, and the collected frequency parameter measurement value is preprocessed, and then the frequency parameter measurement value is compared with the frequency parameter simulation value of the resonance point of the impedance logarithmic amplitude spectrum in the circuit model constructed in step S1 to determine whether the frequency parameter measurement value belongs to an abnormal point, if so, the frequency parameter measurement value is discarded, otherwise the frequency parameter measurement value can be retained;

[0086] S32) Calculate the resonance peak offset and characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested:

[0087] Similar to the calculation of the resonance peak offset of the impedance logarithmic amplitude spectrum in step S2, in the present embodiment, when calculating the resonance peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested, the frequency of the resonance peak maximum value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested and the frequencies corresponding to other resonance peaks are obtained, and then the frequency of the resonance peak maximum value and the frequencies corresponding to other resonance peaks in the impedance logarithmic amplitude spectrum of the normal operation of the dry-type air-core reactor are simulated according to the circuit model, and the frequency offset of the resonance peak maximum value and other resonance peaks of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested is obtained, and then the average value of two or more frequency offsets is calculated to obtain the resonance peak offset;

[0088] Similar to the calculation of the characteristic value of the impedance logarithmic amplitude spectrum in step S2, when calculating the characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested in this embodiment, the absolute value of the impedance logarithmic amplitude spectrum waveform of the current dry-type air-core reactor to be tested is also integrated to obtain the corresponding characteristic waveform, and then the inflection point value A1 of the first stage and the stable values ​​A2 and A3 at the steps of the second and third stages in the characteristic waveform are obtained. Finally, the ratio of the stable value A2 at the step of the second stage to the inflection point value A1 of the first stage is calculated as the first characteristic value K1, and the ratio of the stable value A3 at the step of the third stage to the stable value A2 at the step of the second stage is calculated as the second characteristic value K2.

[0089] Step S4 of this embodiment includes the following steps:

[0090] S41) if the resonance peak offset is 0, it means that the dry-type air-core reactor to be tested is in a normal state; if the resonance peak offset is greater than 0, it means that the dry-type air-core reactor to be tested may have a turn-to-turn short-circuit fault, and the process jumps to step S42);

[0091] S42) matching the resonance peak offset and characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested with the resonance peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each turn-to-turn short circuit, specifically including:

[0092] S421) matching the resonance peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested with the resonance peak offset interval of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuit of different fault degrees, and determining the corresponding inter-turn short circuit fault degree according to the matching result;

[0093] Specifically, when the offset of the resonance wave peak satisfies 0<Δf<2MHZ, it is determined that a slight turn-to-turn short circuit fault occurs in the dry-type reactor to be tested;

[0094] When the offset of the resonance wave peak satisfies 2<Δf<20MHZ, it is determined that a relatively serious turn-to-turn short circuit fault occurs in the dry-type reactor to be tested;

[0095] When the offset of the resonance wave peak satisfies Δf>20 MHZ, it is determined that a serious turn-to-turn short circuit fault occurs in the dry-type reactor to be tested;

[0096] S421) comparing the characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested with the characteristic value change trend of the impedance logarithmic amplitude spectrum corresponding to the determined turn-to-turn short-circuit fault degree; if the characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested matches the characteristic value change trend of the impedance logarithmic amplitude spectrum corresponding to the determined turn-to-turn short-circuit fault degree, the turn-to-turn short-circuit fault degree of the dry-type air-core reactor to be tested is the determined turn-to-turn short-circuit fault degree;

[0097] Specifically, when a slight inter-turn short-circuit fault occurs and the number of short-circuit turns is small, the slight difference between the peaks may also cause misjudgment in actual detection due to field interference and measurement errors, so that the average offset of the fault resonance point may change slightly. In order to more accurately detect the insulation level and operating status of the reactor, in this embodiment, the absolute value of the waveform is integrated to construct a characteristic waveform, and the characteristic value is extracted from it to highlight the difference in the detection results under different insulation states, forming an auxiliary criterion. The setting of the auxiliary criterion verifies the accuracy of the operating status of the reactor, and plays a role in taking necessary measures in time to ensure the safe and stable operation of the system.

[0098] Therefore, if it is determined that a slight turn-to-turn short circuit fault occurs in the dry-type reactor to be tested, Fig.11 The trend line corresponding to the first eigenvalue K1 and the second eigenvalue K2 whose inductance value decreases by 0-5% is found, and it is determined whether the first eigenvalue K1 and the second eigenvalue K2 of the dry-type air-core reactor to be tested match the corresponding trend line. Specifically, it is determined whether the first eigenvalue K1 and the second eigenvalue K2 of the dry-type air-core reactor to be tested are both on the corresponding trend line and have the same horizontal coordinates. If so, it is confirmed that a slight turn-to-turn short circuit fault occurs in the dry-type reactor to be tested. Otherwise, it is considered that a misjudgment may occur, such as Figure 2As shown, return to step S3 to obtain the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested again for re-detection;

[0099] By analogy, if step S421 determines that a relatively serious turn-to-turn short circuit fault occurs in the dry-type reactor to be tested, and after determining that a serious turn-to-turn short circuit fault occurs in the dry-type reactor to be tested, the judgment result of step S421 can be confirmed by searching for the corresponding characteristic value trend line and determining whether the characteristic value of the dry-type air-core reactor to be tested matches the characteristic value trend line;

[0100] S423) matching the resonance peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested with the resonance peak offset interval of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuit at different fault positions in the determined inter-turn short circuit fault degree, and determining the corresponding inter-turn short circuit fault position according to the matching result.

[0101] Specifically, in step S423 of this embodiment, based on the judgment results of step S421 and step S422, the approximate decrease range of the inductance of the dry-type air-core reactor to be tested can be obtained. For example, if it is confirmed that a serious turn-to-turn short circuit fault occurs in the dry-type reactor to be tested, the approximate decrease range of the inductance is 5-15%.

[0102] Therefore, the set of resonance peak offsets of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuit at different fault locations in the corresponding inductance drop range collected in step S2 can be selected to match the resonance peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested, and the fault location corresponding to the closest resonance peak offset is selected as the possible fault location. For example, select Figure 8 The set of resonance peak offsets of the impedance logarithmic amplitude spectrum at different positions where the inductance drops by 10% shown can determine the position where the inter-turn fault of the dry-type air-core inductor to be tested occurs based on the position corresponding to the resonance peak offset that is closest to the resonance peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core inductor to be tested.

[0103] Embodiment 2

[0104] This embodiment proposes a dry-type air-core reactor turn-to-turn short-circuit fault detection system based on the average offset of the resonance wave peak, including a microprocessor and a computer-readable storage medium connected to each other, and the microprocessor is programmed or configured to execute the dry-type air-core reactor turn-to-turn short-circuit fault detection method based on the average offset of the resonance wave peak described in Example 1.

[0105] In summary, the present invention finds that as the frequency increases, the inductive reactance increases and the capacitive reactance decreases, series-parallel resonance occurs in the internal circuit of the reactor, and at high frequencies, the voltage drop of the reactor is distributed according to the capacitance, and when its impedance logarithmic amplitude spectrum is measured, the resonance point frequency in the amplitude spectrum is very sensitive to changes in electrical parameters. Therefore, the impedance logarithmic amplitude spectrum can be used to analyze the operating state of the reactor. Therefore, a dry-type air-core reactor turn-to-turn short-circuit fault detection method based on the average offset of the resonance peak is proposed, and different peak values ​​generated by resonance are obtained. When the average values ​​of two or more resonance peak offsets under different fault degrees are greater than the set value, and the distribution change law of the K1 and K2 characteristic values ​​is met, it is determined whether the dry-type air-core reactor has different degrees of turn-to-turn short-circuit faults.

[0106] When the present invention measures data, when it is found that the offset of the resonance point peak value collectively shifts to the right, the average value of the resonance wave peak offset calculated twice or more is in which set value interval, and when the change trend of the above-mentioned auxiliary criteria K1 and K2 is met, it is determined that the degree of the dry-type air-core reactor fault is one of a slight inter-turn short circuit fault, a relatively serious inter-turn short circuit fault, and a serious inter-turn short circuit fault. Then the general range of the inductance value drop is inferred, and according to the average offset of the resonance point and the frequency change curve of the fault position, it can be determined at which layer of the reactor the inter-turn short circuit occurs, that is, the fault position is determined, and an alarm / removal signal can be issued in time, and the real-time state of the reactor can be diagnosed in time, thereby improving the sensitivity.

[0107] The simulation results show that the method of the present invention is correct in judgment and has high accuracy, effectiveness and reliability.

[0108] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for detecting inter-turn short-circuit faults of dry-type air-core reactors based on average offset of resonance peaks, characterized in that: The following steps are involved: Constructing a circuit model of a dry-type air-core reactor, using the circuit model to simulate the normal operation of the dry-type air-core reactor and turn-to-turn short circuits with different fault degrees and fault locations, and obtaining corresponding impedance logarithmic amplitude spectra; Calculate the resonance peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each turn-to-turn short circuit of the dry-type air-core reactor respectively, wherein the resonance peak offset specifically refers to the offset of the resonance peak of the impedance logarithmic amplitude spectrum compared with the resonance peak of the impedance logarithmic amplitude spectrum when the dry-type air-core reactor is operating normally; Obtaining an impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested, and calculating a resonant peak offset and a characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested; If the resonant peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested is greater than a preset threshold, the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested are matched with the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each turn-to-turn short circuit, and the turn-to-turn short circuit fault location and fault degree of the dry-type air-core reactor to be tested are determined according to the matching result.

2. The method for detecting inter-turn short-circuit fault of dry-type air-core reactor based on average offset of resonance wave peak according to claim 1 is characterized in that: Constructing the circuit model of dry-type air-core reactor specifically includes the following steps: Establish the distributed equivalent circuit model of the reactor at high frequency, calculate the inter-turn capacitance, inter-layer capacitance and stray capacitance to the ground, coil self-inductance and mutual inductance; For any node i in the distributed equivalent circuit model of the reactor, write the Kirchhoff current law equation, then write the voltage and current equations of the inductor and resistor branches adjacent to the node i, and organize them into the form of an admittance matrix, so that after the node voltage and current are obtained, the inverse of the admittance matrix is ​​calculated to obtain the impedance value.

3. The method for detecting inter-turn short-circuit fault of dry-type air-core reactor based on average offset of resonance wave peak according to claim 2, characterized in that: The expression in admittance matrix form is as follows: [Y] · [ΔU + U'] = [I] Where [Y] is the admittance matrix of the equivalent circuit model, ΔU represents the node voltage difference, and U' represents the mutual inductance voltage drop.

4. The method for detecting inter-turn short-circuit fault of dry-type air-core reactor based on average offset of resonance wave peak according to claim 1, characterized in that: When respectively calculating the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each inter-turn short circuit of the dry-type air-core reactor, the step of calculating the resonant peak offset of the impedance logarithmic amplitude spectrum includes: Get the frequency f corresponding to the maximum value of the resonance peak in the impedance logarithmic amplitude spectrum of the dry-type air-core reactor during normal operation M The frequencies f1, f2, ... f corresponding to other resonance peaks n ; Get the frequency f corresponding to the maximum value of the resonant peak in the impedance logarithmic amplitude spectrum corresponding to the current inter-turn short circuit M 'The frequencies corresponding to other resonance peaks are f1', f2'...f n '; Calculate the frequency f corresponding to the maximum value of the resonant peak in the impedance logarithmic amplitude spectrum corresponding to the current inter-turn short circuit M 'Relative to frequency f M The offset Δf M , and calculate the frequencies f1', f2'...f corresponding to other resonant peaks in the impedance logarithmic amplitude spectrum corresponding to the current inter-turn short circuit n 'With respect to frequencies f1, f2...f n The offset Δf1, Δf2...Δf n , calculate the offset Δf M , Δf1, Δf2...Δf n The average value of the resonance peak offset Δf corresponding to the current inter-turn short circuit is obtained.

5. The method for detecting inter-turn short-circuit fault of dry-type air-core reactor based on average offset of resonance wave peak according to claim 1, characterized in that: When respectively calculating the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each inter-turn short circuit of the dry-type air-core reactor, the step of calculating the characteristic value of the impedance logarithmic amplitude spectrum includes: The absolute value of the impedance logarithmic amplitude spectrum waveform corresponding to the current turn-to-turn short circuit is integrated to obtain the corresponding characteristic waveform, and the change trend of the specified position of the characteristic waveform is calculated to obtain the characteristic value corresponding to the current turn-to-turn short circuit.

6. The method for detecting inter-turn short-circuit fault of dry-type air-core reactor based on average offset of resonance wave peak according to claim 5, characterized in that: When calculating the change trend of a specified position of a characteristic waveform, it includes: Obtaining the inflection point value A1 of the first stage in the characteristic waveform, and the step stability values ​​A2 and A3 of the second stage and the third stage in the characteristic waveform; The ratio of the stable value A2 at the step in the second stage to the inflection point value A1 in the first stage is calculated as the first eigenvalue K1 corresponding to the current turn-to-turn short circuit, and the ratio of the stable value A3 at the step in the third stage to the stable value A2 at the step in the second stage is calculated as the second eigenvalue K2 corresponding to the current turn-to-turn short circuit.

7. The method for detecting inter-turn short-circuit fault of dry-type air-core reactor based on average offset of resonance wave peak according to claim 1, characterized in that: After respectively calculating the resonant peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each inter-turn short circuit of the dry-type air-core reactor, the method includes: dividing the resonant peak offset intervals of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuits of different fault degrees according to the value of the resonant peak offset, and constructing a set of resonant peak offsets of the corresponding impedance logarithmic amplitude spectrum for the inter-turn short circuits of different fault positions under the same fault degree; The characteristic values ​​of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuits with different fault degrees are fitted to obtain the characteristic value change trends of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuits with different fault degrees.

8. The method for detecting inter-turn short-circuit fault of dry-type air-core reactor based on average offset of resonance wave peak according to claim 7, characterized in that: When matching the resonance peak offset and characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested with the resonance peak offset and characteristic value of the impedance logarithmic amplitude spectrum corresponding to each turn-to-turn short circuit, including: The resonance peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested is matched with the resonance peak offset interval of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuit of different fault degrees, and the corresponding inter-turn short circuit fault degree is determined according to the matching result; Compare the characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested with the characteristic value change trend of the impedance logarithmic amplitude spectrum corresponding to the determined inter-turn short-circuit fault degree; if the characteristic value of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested matches the characteristic value change trend of the impedance logarithmic amplitude spectrum corresponding to the determined inter-turn short-circuit fault degree, then the inter-turn short-circuit fault degree of the dry-type air-core reactor to be tested is the determined inter-turn short-circuit fault degree; The resonance peak offset of the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested is matched with the set of resonance peak offsets of the impedance logarithmic amplitude spectrum corresponding to the inter-turn short circuit at different fault positions in the determined inter-turn short circuit fault degree, and the corresponding inter-turn short circuit fault position is determined according to the matching result.

9. The method for detecting inter-turn short-circuit fault of dry-type air-core reactor based on average offset of resonance wave peak according to claim 1, characterized in that: When obtaining the impedance logarithmic amplitude spectrum of the dry-type air-core reactor to be tested, it includes: real-time acquisition of the frequency parameter measurement value of the resonance point in the impedance logarithmic amplitude spectrum and preprocessing, and then comparing it with the corresponding frequency parameter simulation value in the circuit model to determine whether the frequency parameter measurement value belongs to an abnormal point, if so, discard the corresponding data, otherwise retain the corresponding data.

10. A dry-type air-core reactor turn-to-turn short-circuit fault detection system based on the average offset of the resonance peak, characterized in that: The invention comprises a microprocessor and a computer-readable storage medium connected to each other, wherein the microprocessor is programmed or configured to execute the dry-type air-core reactor turn-to-turn short-circuit fault detection method based on the average offset of the resonance wave peak as claimed in any one of claims 1 to 9.

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