CN108318791B - Air-core reactor turn-to-turn insulation fault discrimination method based on frequency domain characteristic analysis - Google Patents
Air-core reactor turn-to-turn insulation fault discrimination method based on frequency domain characteristic analysis Download PDFInfo
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Abstract
The method adopts a method based on frequency domain analysis to diagnose the turn-to-turn insulation fault of the air reactor. At present, time domain waveforms are generally adopted to judge whether faults occur, the oscillation period and the attenuation coefficient need to be further compared, and normal waveforms and fault waveforms are difficult to distinguish. The purpose of accurately and conveniently judging the turn-to-turn insulation fault is achieved, and the safe and stable operation of the air reactor is guaranteed.
Description
Technical Field
power equipment fault diagnosis
background
At present, the following methods are mainly used for detecting turn-to-turn insulation of a reactor: (1) and (4) a leakage magnetic field detection method. According to the method, the Hall sensor is used for measuring the magnetic leakage field diagram, so that the turn-to-turn fault of the iron core type winding can be measured, and the position of the short circuit can be judged. However, the method is only suitable for direct short circuit faults and cannot detect invisible turn-to-turn faults. (2) High frequency oscillation energy absorption method. The principle of the method is that when a coil which is electrified with high-frequency current is close to a coil which generates turn-to-turn short circuit, the phenomenon that energy is absorbed can be generated, and if the energy is absorbed, the coil has the turn-to-turn short circuit. But this method is costly. (3) Lightning impulse test method. The traditional lightning impulse test examines the electrical strength of longitudinal insulation of the winding, namely turn-to-turn insulation, interlayer insulation, section-to-section insulation and the like. The application time of the lightning impulse voltage is short, so the detection effect is not satisfactory. (4) High frequency pulse oscillation voltage method. The pulse voltage method is to utilize the charged capacitor to form an oscillating circuit with the tested coil through a switch, the oscillating frequency is a function of the inductance and the capacitance, and the testing frequency can be determined within the range required by the test by selecting the determined charging capacitance. The test judges the turn-to-turn insulation condition of the reactor by detecting and comparing the waveforms of the high-frequency pulse oscillation voltage under the applied lower voltage and the applied full voltage. The method can generate higher test voltage, thereby being beneficial to finding out turn-to-turn insulation defects. Thus, the pulsed voltage method is a common method in detecting inter-turn insulation.
the pulse voltage method is characterized in that half voltage and full voltage are applied to two ends of the reactor, and high-frequency pulse oscillation voltage waveforms under the two conditions are compared, so that whether the reactor has turn-to-turn insulation defects or not is judged. The basic principle is shown in fig. 1.
During the experiment, the power supply after half-wave or full-wave rectification charges the high-voltage pulse capacitor, and when the charging voltage reaches the specified requirement. The discharge ball gap is conducted, and the pulse capacitor and the test winding form a damped oscillation circuit with a certain frequency
The discharge voltage gradually decays until the discharge voltage does not sufficiently decay to sustain the arc, so that the arc is extinguished, and after the arc is extinguished, the pulse capacitor starts to be charged again to prepare for the next impact. After thousands of impacts, the test winding is not burnt out, and the full-voltage waveform frequency and the half-voltage waveform frequency are equal, the winding can be considered to be intact.
When the inter-turn insulation detection is performed by using the pulse voltage method, time domain response waveforms of voltages are obtained, as shown in fig. 2.
As can be seen from fig. 2, the time domain waveform with or without the inter-turn insulation fault has no obvious variation characteristic, and the inter-turn insulation fault cannot be determined only from the time domain waveform of the response voltage, and the waveform needs to be further processed. Only by further analyzing the periodic characteristic and the attenuation characteristic of the time domain waveform, and comparing the voltage or current waveform frequency and the zero crossing point change of the two ends of the reactor sample under the rated voltage of the system and the oscillating wave test voltage, whether the turn-to-turn insulation fault exists in the coil of the air reactor can be inferred.
disclosure of Invention
aiming at the problem that the waveform change is not obvious when the turn-to-turn insulation fault is judged by the existing time domain waveform, the method for judging the fault is improved on the basis of the original hardware, and the method for judging the turn-to-turn insulation fault of the air-core reactor based on frequency domain characteristic analysis is provided.
In the data processing process of judging whether the fault exists, the time domain analysis of the traditional method is easy to generate amplitude and phase deviation, so that the deviation of the waveform contrast effect is caused, and the judgment of the turn-to-turn fault of the reactor is not facilitated. When the turn-to-turn insulation of the air reactor fails, the short-circuit ring with the short-circuit failure can generate a demagnetization effect, and the electromagnetic field theory shows that the coil generates induced electromotive force in an alternating magnetic field, and the short-circuit turns of the reactor winding reduce the integral turns of the winding, so that the equivalent inductance parameter of the reactor changes, and further the frequency response changes obviously. And performing data fitting on the original time domain waveform to obtain a change function of the voltage at two ends of the reactor along with time, performing Fourier transform on the function to obtain a frequency spectrum function, and analyzing in a frequency domain. The detection based on the frequency domain characteristic analysis can judge the existence of the fault more accurately, so that the result has lower error, and higher accuracy and stability are achieved. The invention provides a method for detecting turn-to-turn insulation faults of an air reactor based on frequency domain characteristic comparison, which is used for accurately finding the turn-to-turn insulation faults of the air reactor, ensuring the reliable operation of the air reactor and improving the operation safety of a power grid.
1, a method for judging turn-to-turn insulation faults of the air-core reactor based on frequency domain characteristics:
(1) Detecting the turn-to-turn insulation of the reactor by using a pulse current method reactor turn-to-turn insulation detection device to obtain a time domain waveform of voltage changing along with time, wherein the formula is as follows (1):
Where ω 1 is the actual oscillation frequency, ω 0 is the natural oscillation frequency, and δ is the damping coefficient.
δ ═ R/2L, β ═ arctan (ω 1/δ) is the initial phase angle.
values of parameters such as omega 1, omega 0, delta, beta and the like can be obtained by a Matlab software curve fitting method.
(2) fourier transforming the time domain formula of equation (1):
And obtaining the function relation of the voltage at the two ends of the air-core reactor along with the frequency, as shown in a formula (2):
where ω 1 is the actual oscillation frequency, ω 0 is the natural oscillation frequency, and δ is the damping coefficient. (same formula (1))
Analyzing the frequency domain formula (2) to obtain a magnitude spectrum function of the spectrum function: amplitude of frequency domain
The amplitude spectrum function obtained by calculation is shown as formula (3):
In the formula, ω 1 is an actual oscillation frequency, and ω 0 is a natural oscillation frequency.
β ═ arctan (ω 1/δ) is the initial phase angle.
According to the characteristic analysis of the amplitude spectrum, a characteristic analysis method based on a frequency domain can be obtained.
typical values are taken for the parameters of equation (3) (taking a 35kV air reactor as an example): r ═ 5 Ω; c ═ 3 nF; uc is charged to 180 kV; when L is 60mH, 100mH and 140mH, respectively, the variation curve of the voltage amplitude U with the frequency ω is obtained as shown in fig. 3: the function shown in equation (3) is an even function, so that the given amplitude spectrum only needs to display the range of [0, + ∞).
as can be seen from FIG. 3, the waveform of the amplitude spectrum is simpler than that of a time domain, and whether the inter-hybrid insulation of the air-core reactor fails or not is more easily judged according to the characteristics of the waveform of the amplitude spectrum.
(3) Criterion
Whether the turn-to-turn insulation of the air-core reactor has a fault or not is finally judged according to whether the change range of the inductance value of the air-core reactor exceeds the permission or not. Namely, a critical inductance value L 'needs to be found out, and when the equivalent inductance value L of the air reactor is less than L', the turn-to-turn insulation fault of the air reactor can be judged. However, the equivalent inductance of the air core reactor cannot be directly measured by judging the turn-to-turn insulation fault by the pulse current method, and whether the fault occurs or not needs to be judged according to the waveform characteristics.
the method for judging whether the turn-to-turn insulation of the reactor has faults or not by utilizing the periodic change rate and the attenuation coefficient change rate (time domain criterion), and the obtained critical inductance value L' is determined by the following criterion:
The periodic change rate is less than or equal to 5 percent
The frequency is calculated through a formula, so that the periodic change rate is obtained, and the inductance temporary fault during the fault is further calculated
The cutoff values, namely:
wherein
② the attenuation change rate is less than or equal to 10 percent
calculating formula by attenuation coefficient:
the resulting fault inductance threshold is thus:
Respectively obtaining L1' and L2' from the first step and the second step, and taking the larger value as the critical inductance value L '.
As can be seen from fig. 3, in the range of ω ∈ [0, 1000], as the value of L increases, the corresponding amplitude spectrum curve increases at a faster rate with increasing frequency, and the reaction is graphically characterized as: the curve upwarps more obviously. Namely: (1) the amplitude spectrum curve corresponding to the air reactor with the turn-to-turn insulation fault is below the amplitude spectrum curve corresponding to the critical fault; (2) when the amplitude spectrum curve is positioned between the amplitude spectrum curves corresponding to the critical fault and the normal value respectively, the turn-to-turn insulation state of the air-core reactor can be judged according to the degree of deviation from the normal curve.
Therefore, whether the turn-to-turn insulation of the air-core reactor corresponding to the amplitude spectrum curve has a fault or not can be accurately and conveniently judged according to the characteristics.
(4) The air-core reactor turn-to-turn insulation fault distinguishing method based on frequency domain characteristic analysis comprises the following steps:
and (3) evaluating the insulation state between turns of the dry-type air-core reactor by using a frequency domain spectrogram of voltage at two ends of the reactor corresponding to the inductance value. The criterion is roughly divided into two parts: a data calculation section and a judgment processing section. The specific judgment process is as follows:
1) A data calculation section:
(1) For the air reactor with normal turn-to-turn insulation, each parameter value can be obtained by utilizing the time domain waveform obtained by the detection of the device, and the equivalent inductance value L of the air reactor in normal state is further obtained by calculation;
(2) Obtaining a determined critical inductance value L' from the formulas (4) and (5);
(3) and (3) selecting L in normal and L 'in critical fault according to the values of parameters selected by an actual test device for the parameters such as the resistor, the capacitor, the power supply voltage and the like, substituting the L' in normal and L 'in critical fault into the formula (3), and drawing out the waveforms of the formula in the range of [0, + ∞) to obtain 2 frequency domain curves in normal and critical fault, which are respectively marked as curves R and R'.
2) A judging section:
(1) Detecting any air reactor by using the existing device to obtain a time domain waveform of voltage changing along with time;
(2) and (3) obtaining parameter values such as omega 1, omega 0, delta, beta and the like through curve fitting, substituting the formula (3), obtaining an amplitude spectrogram of the voltage of the detected air-core reactor along with the frequency change, and recording the amplitude spectrogram as a curve R1.
(3) In the range of ω ∈ [0, 1000], when the curve R1 is below the amplitude spectrum curve R' corresponding to the critical fault; the turn-to-turn insulation fault of the R1 air-core reactor can be judged; when the amplitude spectrum curve R1 is positioned between the amplitude spectrum curves R and R' respectively corresponding to the critical fault and the normal value, the turn-to-turn insulation state of the air-core reactor can be judged according to the degree of deviation from the normal curve.
Drawings
FIG. 1 is a basic schematic diagram of the pulse voltage method of the present invention
FIG. 2 is a diagram of the voltage time domain waveform of the pulse voltage method according to the present invention
FIG. 3 is a diagram showing the amplitude spectrum waveform of the two ends of the oscillation loop air reactor varying with the frequency
FIG. 4 is a graph showing the magnitude spectra of 4 sets of air core reactors with different inductance values according to the present invention
FIG. 5 is a flow chart of the software implementation proposed by the present invention
Detailed Description
the invention will be described in further detail below with reference to the drawings and specific examples.
(1) And (3) detecting and distinguishing turn-to-turn insulation of the 35kV air-core reactor: the standard requires that the pulse oscillation frequency is about 100kHz, and according to related parameters and analysis of theoretical calculation, the following are taken: r5 Ω, C3 nF, Uc charged to 180 kV. Under normal conditions, the equivalent inductance value of the air core reactor is L100 mH.
According to the criterion formula of the periodic change rate and the attenuation change rate, the critical fault inductance value L' is 90mH when L is 100mH, and is calculated by the formulas (4) and (5)
(2) and (4) randomly selecting four groups of reactors with different inductance values of L1, L2, L3 and L4, and judging whether the method for analyzing the fault based on the frequency domain is reasonable.
1) And (3) calculating whether four groups of inductance values have faults according to a time domain criterion formula:
Table 1 selected 4 sets of reactors with different inductance values
2) drawing four voltage spectrum amplitude curves and criterion curve by using frequency domain amplitude formula
As shown in FIG. 4, in the range of ω ∈ [0, 1000], the magnitude of the voltage amplitude in the frequency domain increases with the increase of the frequency all the time, that is, the voltage amplitude at both ends of the reactor has a monotonically increasing relationship with the frequency. As the inductance value changes, the rate of increase of the voltage amplitude will also change accordingly. Therefore, whether the inter-turn insulation has faults can be judged by utilizing curve range sections corresponding to different inductance values in a frequency domain.
Drawing a voltage amplitude curve corresponding to the inductance values of the normal condition and the fault critical value through a frequency domain voltage amplitude formula of time domain and Fourier transform, and if the voltage amplitudes at two ends of the reactor to be detected belong to the results obtained by the frequency domain formula and the criterion calculation results, the reactor to be detected is indicated to work normally because the frequency and the voltage amplitude are in a monotonous relation; and if the range is exceeded, indicating the turn-to-turn insulation fault of the reactor. As can be seen from fig. 4, the amplitude spectrum curve of the inductance value L2 of the non-fault air reactor is within the voltage amplitude range of the normal value (L1) and the threshold value (L3), and the amplitude spectrum curve corresponding to the fault value L4 is not within the voltage amplitude range of the normal value (L1) and the threshold value (L3), so that it can be determined as a fault. The method for judging the turn-to-turn insulation fault of the air-core reactor based on the frequency domain characteristics is proved to be capable of accurately and conveniently judging the turn-to-turn insulation fault of the air-core reactor.
Claims (1)
1. A method for judging turn-to-turn insulation fault of an air-core reactor based on frequency domain characteristic analysis is used for converting an analysis method for judging and comparing turn-to-turn insulation fault diagnosis criterion of the air-core reactor based on time domain waveform into a method based on frequency domain characteristic comparison, and comprises a data calculation part and a judgment processing part:
a data calculation section including:
s1: for an air reactor with normal turn-to-turn insulation, detecting by using a device to obtain a time domain waveform of voltage changing along with time, calculating according to a formula (1) to obtain values of all parameters, and further calculating to obtain an equivalent inductance value L of the air reactor when the air reactor is normal;
Wherein the formula (1) is:
Wherein, ω 1 is an actual oscillation frequency, ω 0 is a natural oscillation frequency, δ is an attenuation coefficient, δ is R/2L, and β is arctan (ω 1/δ) is an initial phase angle;
S2: the critical inductance value L' determined from equations (4) and (5) includes:
when the periodic variation rate is less than or equal to 5 percent,
calculating the frequency through a formula, so as to obtain a periodic change rate, and further calculating an inductance critical value L' during fault, namely:
wherein
② when the attenuation change rate is less than or equal to 10 percent,
Calculating formula by attenuation coefficient: the resulting fault inductance threshold is thus:
respectively obtaining L1' and L2' from the first step and the second step, and taking the larger value as a critical inductance value L ';
S3: respectively selecting L in normal state and L' in critical fault state to substitute into formula (3):
drawing the waveform of the fault in the range of [0, + ∞ ]), obtaining 2 frequency domain curves at normal and critical faults, and respectively marking as curves R and R';
And a judgment processing section including:
s4: detecting any air-core reactor to obtain a time domain waveform of voltage changing along with time;
s5: obtaining parameter values such as omega 1, omega 0, delta, beta and the like through curve fitting, substituting formula (3), obtaining an amplitude spectrogram of the voltage of the detected air-core reactor along with the frequency change, and marking as a curve R1;
S6: the following judgment is made:
In the range of ω ∈ [0, 1000], when the curve R1 is below the amplitude spectrum curve R' corresponding to the critical fault; judging the turn-to-turn insulation fault of the R1 air-core reactor;
and when the amplitude spectrum curve R1 is positioned between the amplitude spectrum curves R and R' respectively corresponding to the critical fault and the normal value, judging the turn-to-turn insulation state of the air-core reactor according to the degree of deviation from the normal curve.
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| CN110456241B (en) * | 2019-08-30 | 2022-02-11 | 国家电网有限公司 | Coil turn-to-turn fault detection method |
| CN111190125A (en) * | 2020-01-06 | 2020-05-22 | 长沙理工大学 | Discrimination method for detecting turn-to-turn insulation fault of air-core reactor by pulse voltage method based on FFT transform domain characteristics |
| CN112731220A (en) * | 2020-12-01 | 2021-04-30 | 三峡大学 | Current transformer iron core coil fault diagnosis method based on frequency spectrum analysis |
| CN113852046B (en) * | 2021-09-29 | 2024-02-13 | 南京国电南自电网自动化有限公司 | Method and system for preventing turn-to-turn protection misoperation when line reactor adopts bus PT |
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| JP3499844B2 (en) * | 2001-08-27 | 2004-02-23 | 株式会社前川製作所 | Displacement detection method and its displacement sensor |
| CN105203936A (en) * | 2015-10-26 | 2015-12-30 | 云南电网有限责任公司电力科学研究院 | Method for determining power cable partial discharge defect type based on spectral analysis |
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