Dry-type air-core reactor turn-to-turn short circuit fault detection method and system

Abstract

The invention discloses a dry-type air-core reactor turn-to-turn short circuit fault detection method and system. The method comprises the following steps: acquiring a first phase voltage signal and a first phase current signal of a to-be-detected dry-type air-core reactor in real time; the first phase voltage signal and the first phase current signal are preprocessed, the preprocessed first phase voltage signal and the preprocessed first phase current signal in a first specified number of windows are obtained through a sliding window, and a corresponding power factor real-time value is calculated according to the preprocessed first phase voltage signal and the preprocessed first phase current signal in each window; respectively calculating the change rate of each power factor real-time value compared with the power factor reference value; and if the real-time value of the power factor with the change rate greater than the preset threshold value reaches a second specified number, determining that the to-be-detected dry-type air-core reactor has the turn-to-turn short circuit fault. According to the turn-to-turn short-circuit fault detection method, the condition that the number of power factor change rates exceeds a normal range is adopted as a protection criterion, so that the sensitivity and reliability of turn-to-turn short-circuit fault detection are ensured.

Description

Technical Field

[0001] The present invention relates to the detection technology of dry-type air-core reactors, and particularly to a method and system for detecting turn-to-turn short-circuit faults of dry-type air-core reactors. Background Art

[0002] With the large-scale commissioning and long-term operation of dry-type air-core reactors, their failure rates are continuously increasing, and 70% of the failures are caused by turn-to-turn short-circuit faults. When a turn-to-turn short-circuit fault occurs in a dry reactor, the local temperature at the short-circuit position rises sharply, accelerating the insulation aging near the short-circuited turns, causing the continuous development of the short-circuit fault and then expanding into a multi-turn short-circuit fault. The reactor will catch fire in a short time. If the reactor is cut off from the power grid at this time, the reactor has been severely burned. Therefore, a fault judgment needs to be made in the early stage of the fault. However, in the early stage of a turn-to-turn short-circuit fault in a dry-type air-core reactor, although the current in the short-circuit ring will become very large, its phase current value hardly changes. Existing reactors only set over-current protection for inter-phase short-circuits of reactor leads, generally only installing instantaneous over-current protection and over-current protection, and will not detect the current value of the short-circuit ring. And the change value of the phase current does not reach the protection action value, so the protection cannot act in time to cut off the fault. Moreover, in the early stage of the fault, the electrical parameters such as the inductance and resistance of the reactor change very little, and it is less reliable to reflect fault information through these electrical parameter changes.

[0003] The power factor changes significantly before and after the reactor fault. Therefore, some solutions choose to use the power factor to judge the turn-to-turn short-circuit fault of the dry-type air-core reactor. The existing turn-to-turn short-circuit protection method for dry-type air-core reactors based on the power factor uses a single power factor value calculated in one cycle as the protection criterion, and the protection is prone to misoperation; because under ideal conditions, the power factor of the reactor during normal operation should be a fixed value, but due to factors such as frequency fluctuations and noise interference, the power factor will fluctuate greatly. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: aiming at the technical problems existing in the prior art, the present invention provides a method and system for detecting turn-to-turn short-circuit faults of dry-type air-core reactors, which uses the number of cases where the rate of change of the power factor exceeds the normal range as the protection criterion to ensure the sensitivity and reliability of the turn-to-turn short-circuit fault detection.

[0005] To solve the above technical problems, the technical solution proposed by the present invention is:

[0006] A method for detecting turn-to-turn short-circuit faults of dry-type air-core reactors includes the following steps:

[0007] S101) Obtain the first-phase voltage signal and the first-phase current signal of the dry-type air-core reactor to be detected in real time;

[0008] S102) Preprocess the first-phase voltage signal and the first-phase current signal, obtain the preprocessed first-phase voltage signal and the first-phase current signal in the first specified number of windows through a sliding window, calculate the corresponding real-time power factor value according to the preprocessed first-phase voltage signal and the first-phase current signal in each window, and calculate the change rate of each real-time power factor value compared to the power factor reference value respectively;

[0009] S103) If the number of real-time power factor values whose change rate is greater than the preset threshold reaches the second specified number, it is determined that the dry-type air-core reactor to be detected has a turn-to-turn short circuit fault.

[0010] Further, before step S101, there is also a step of calculating the power factor reference value, which specifically includes:

[0011] Obtain the second-phase voltage signal and the second-phase current signal of the dry-type air-core reactor under normal operation, preprocess the second-phase voltage signal and the second-phase current signal, and calculate the power factor reference value according to the preprocessed second-phase voltage signal and the second-phase current signal.

[0012] Further, when preprocessing the first-phase voltage signal and the first-phase current signal, and when preprocessing the second-phase voltage signal and the second-phase current signal, both include:

[0013] S201) Calculate the estimated value of each element in the data sequence;

[0014] S202) If the absolute value of the difference between the measured value of the current element in the data sequence and the estimated value of the current element is greater than the given first threshold, replace the measured value of the current element with the estimated value of the current element.

[0015] Further, when calculating the estimated value of each element in the data sequence in step S201, it includes:

[0016] S301) Traverse the data sequence x(n) through the first sliding window, select the median of the data in each window respectively, and obtain the data sequence x1(n);

[0017] S302) Traverse the data sequence x1(n) through the second sliding window, select the median of the data in each window respectively, and obtain the data sequence x2(n);

[0018] S303) Construct a smooth sequence x3(n) according to the elements in the data sequence x2(n), and the value of each element in the smooth sequence x3(n) is the estimated value of each element in the data sequence.

[0019] Further, the window size of the first sliding window is 5 elements, and the step size is 1 element. The window size of the second sliding window is 3 elements, and the step size is 1 element. The expression of the elements in the smoothing sequence x3(n) is as follows:

[0020] x3(i) = 0.25x2(i - 1) + 0.5x2(i) + 0.25x2(i + 1)

[0021] where x3(i) represents the i-th element in the smoothing sequence x3(n), x2(i - 1) represents the (i - 1)-th element in the data sequence x2(n), x2(i) represents the i-th element in the data sequence x2(n), and x2(i + 1) represents the (i + 1)-th element in the data sequence x2(n).

[0022] Further, when calculating the real-time value of the corresponding power factor according to the preprocessed first-phase voltage signal and first-phase current signal in each window, and when calculating the reference value of the power factor according to the preprocessed second-phase voltage signal and second-phase current signal, both include:

[0023] S401) Perform a discrete Fourier transform on the voltage signal to obtain the real part and imaginary part of the voltage signal, and perform a discrete Fourier transform on the current signal to obtain the real part and imaginary part of the current signal;

[0024] S402) Divide the imaginary part of the voltage signal by the real part to obtain a first quotient value, calculate the arctangent value of the first quotient value to obtain the phase of the voltage signal, divide the imaginary part of the current signal by the real part to obtain a second quotient value, and calculate the arctangent value of the second quotient value to obtain the phase of the current signal;

[0025] S403) Calculate the cosine value of the difference between the phase of the voltage signal and the phase of the current signal to obtain the power factor.

[0026] Further, when obtaining the second-phase voltage signal and second-phase current signal of the dry-type air-core reactor operating normally, it includes: simultaneously collecting the second-phase voltage signal and second-phase current signal of the dry-type air-core reactor operating normally within one period at a specified sampling rate; when obtaining the preprocessed first-phase voltage signal and first-phase current signal in the first specified number of windows through a sliding window, it includes: setting the window size of the sliding window to one period, setting the step size of the sliding window to a specified number of sampling points, moving the window from the starting position of the preprocessed first-phase voltage signal and first-phase current signal according to the step size, and obtaining the preprocessed first-phase voltage signal and first-phase current signal in the window at each position until the number of movements reaches the first specified number.

[0027] Further, in step S102, when calculating the change rate of each real-time power factor value compared with the power factor reference value, the expression of the change rate is as follows:

[0028]

[0029] wherein, represents the power factor reference value, represents the i-th real-time power factor value.

[0030] Optionally, the first specified quantity is R / 2, where R represents the number of sampling points for simultaneously collecting the phase voltage signal and the phase current signal of the dry-type air-core reactor within one cycle at a specified sampling rate, and the second specified quantity is 5.

[0031] The present invention also provides a dry-type air-core reactor turn-to-turn short-circuit fault detection system, including a computer, which is programmed or configured to execute any one of the dry-type air-core reactor turn-to-turn short-circuit fault detection methods.

[0032] Compared with the prior art, the advantages of the present invention are as follows:

[0033] After the present invention obtains the phase voltage signal and the phase current signal of the dry-type air-core reactor to be detected in real time and performs preprocessing, it uses a sliding window to calculate the power factor values corresponding to the phase voltage signal and the phase current signal in multiple windows, and calculates the change rate of each power factor value. By judging the number of power factor change rates exceeding the normal range, it determines whether the reactor has a fault, avoiding the problem that the existing method is prone to misoperation by only calculating the power factor value in one cycle, and can achieve higher accuracy. Description of the Drawings

[0034] Figure 1 is a flowchart of an embodiment of the present invention.

[0035] Figure 2 are the phase voltage and the phase current of the dry-type air-core reactor within one cycle after denoising under normal conditions, where (a) represents the phase voltage and (b) represents the phase current.

[0036] Figure 3 are the phase voltage and the phase current of phase A of the reactor before and after denoising collected under normal conditions, where (a) represents the phase current before denoising, (b) represents the phase current after denoising, (c) represents the phase voltage before denoising, and (d) represents the phase voltage after denoising.

[0037] Figure 4 are the change rates of 20 power factor values calculated under normal conditions.

[0038] Figure 5The phase voltage and phase current of reactor phase A before and after denoising collected during a fault, where (a) represents the phase current before denoising, (b) represents the phase current after denoising, (c) represents the phase voltage before denoising, and (d) represents the phase voltage after denoising.

[0039] Figure 6 The change rates of 20 power factor values calculated during a fault. Specific implementation manners

[0040] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0041] In order to solve the problem of insufficient accuracy of the existing method for detecting inter-turn short-circuit faults of dry-type air-core reactors based on power factor, this embodiment proposes a method for detecting inter-turn short-circuit faults of dry-type air-core reactors, and judges faults through multiple power factor change rates. As Figure 1 shown, it includes the following steps:

[0042] In the pre-stage, calculate the power factor reference value through the voltage and current signals of one cycle after normal operation processing, specifically including:

[0043] S100) Obtain the phase voltage signal and phase current signal of the dry-type air-core reactor during normal operation, preprocess the phase voltage signal and phase current signal, and calculate the power factor reference value according to the preprocessed phase voltage signal and phase current signal.

[0044] In the real-time stage, when the reactor is running, collect voltage and current signals in real time, calculate multiple power factor values using a sliding window, calculate the change rates of these power factor values compared with the power factor reference value, and finally judge faults according to the number of change rates exceeding the normal range, specifically including:

[0045] S101) Obtain the phase voltage signal and phase current signal of the dry-type air-core reactor to be detected in real time;

[0046] S102) Preprocess the phase voltage signal and phase current signal, obtain the preprocessed phase voltage signal and phase current signal in the first specified number of windows through a sliding window, calculate the corresponding real-time power factor values according to the preprocessed phase voltage signal and phase current signal in each window, and calculate the change rates of each real-time power factor value compared with the power factor reference value;

[0047] S103) If the real-time value of the power factor with a change rate greater than the preset threshold reaches the second specified quantity, it is determined that the dry-type air-core reactor to be detected has a turn-to-turn short circuit fault. If the real-time value of the power factor with a change rate greater than the preset threshold does not reach the second specified quantity, it is determined that the dry-type air-core reactor to be detected does not currently have a turn-to-turn short circuit fault, and then jump to execute step S101 to continue obtaining the phase voltage signal and phase current signal of the dry-type air-core reactor to be detected.

[0048] Through the above steps, after the method of this embodiment obtains the phase voltage signal and phase current signal of the dry-type air-core reactor to be detected in real time and performs preprocessing, it uses a sliding window to calculate the power factor values corresponding to the phase voltage signal and phase current signal in multiple windows, and calculates the change rate of each power factor value. By judging the number of power factor change rates exceeding the normal range, it determines whether the reactor has a fault, avoiding the problem that the existing method is prone to false tripping by only calculating the power factor value in one cycle, and can achieve higher accuracy.

[0049] In this embodiment, the phase voltage signal and phase current signal of the dry-type air-core reactor to be detected are referred to as the first phase voltage signal and the first phase current signal, and the phase voltage signal and phase current signal of the dry-type air-core reactor operating normally are referred to as the second phase voltage signal and the second phase current signal for distinction.

[0050] In step S100, when obtaining the second phase voltage signal and the second phase current signal of the dry-type air-core reactor operating normally, it includes: simultaneously collecting the second phase voltage signal and the second phase current signal of the dry-type air-core reactor operating normally within one cycle at a specified sampling rate, sampling R points per cycle; in step S101, when obtaining the first phase voltage signal and the first phase current signal of the dry-type air-core reactor to be detected in real time, it includes: simultaneously collecting the first phase voltage signal and the first phase current signal of the dry-type air-core reactor to be detected in real time at a specified sampling rate, sampling R points per cycle.

[0051] In this embodiment, considering that in the actual working scenario, the collected phase voltage signal and phase current signal will contain noise, so it is necessary to preprocess the phase voltage signal and phase current signal to eliminate noise interference, and determine whether the measured value belongs to an abnormal point by comparing the measured value with the estimated value. If so, replace it with the estimated value, otherwise retain the original signal. Therefore, when preprocessing the first phase voltage signal and the first phase current signal of the dry-type air-core reactor operating normally, and when preprocessing the second phase voltage signal and the second phase current signal of the dry-type air-core reactor to be detected, compare the original data sequence and the new sequence obtained by filtering. If it is greater than the given threshold, replace the corresponding point in the new sequence to generate the finally filtered signal, otherwise retain the original sequence, including:

[0052] S201) Calculate the estimated value of each element in the data sequence;

[0053] S202) If the absolute value of the difference between the measured value and the estimated value of the current element in the data sequence is greater than a given first threshold, then replace the measured value of the current element with the estimated value of the current element.

[0054] When calculating the estimated value of each element in the data sequence in step S201, it includes:

[0055] S301) Traverse the data sequence x(n) through the first sliding window, and respectively select the median of the data in each window to obtain the data sequence x1(n); in this embodiment, the window size of the first sliding window is 5 elements, and the step size is 1 element. The expression of the elements in the data sequence x1(n) is as follows:

[0056] x1(i) = median[x(i - 2)~x(i + 2)] (1)

[0057] where, median[x(i - 2)~x(i + 2)] represents the median of the sequence x(i - 2)~x(i + 2), x(i - 2)~x(i + 2) represents the (i - 2)th to (i + 2)th elements in the data sequence x(n), and x1(i) represents the ith element in the data sequence x1(n);

[0058] S302) Traverse the data sequence x1(n) through the second sliding window, and respectively select the median of the data in each window to obtain the data sequence x2(n); in this embodiment, the window size of the second sliding window is 3 elements, and the step size is 1 element. The expression of the elements in the data sequence x2(n) is as follows:

[0059] x2(i) = median[x1(i - 1)~x1(i + 1)] (2)

[0060] where, median[x1(i - 1)~x1(i + 1)] represents the median of the sequence x1(i - 1)~x1(i + 1), x1(i - 1)~x1(i + 1) represents the (i - 1)th to (i + 1)th elements in the data sequence x1(n), and x2(i) represents the ith element in the data sequence x2(n);

[0061] S303) Construct a smoothed sequence x3(n) according to the elements in the data sequence x2(n). The value of each element in the smoothed sequence x3(n) is the estimated value of each element in the data sequence. The expression of the elements in the smoothed sequence x3(n) is as follows:

[0062] x3(i) = 0.25x2(i - 1) + 0.5x2(i) + 0.25x2(i + 1) (3)

[0063] Among them, x3(i) represents the i-th element in the smoothed sequence x3(n), x2(i - 1) represents the (i - 1)-th element in the data sequence x2(n), x2(i) represents the i-th element in the data sequence x2(n), and x2(i + 1) represents the (i + 1)-th element in the data sequence x2(n).

[0064] Furthermore, in step S202, there is:

[0065] Traverse each element in the data sequence x(n). For the i-th element x(i) among them, if |x(i) - x3(i)| > k, then replace x(i) with x3(i), where k is a number set in advance. After the traversal, it is the preprocessed data sequence, denoted as x4(n).

[0066] In step S102, when obtaining the preprocessed first-phase voltage signal and first-phase current signal in the first specified number of windows through a sliding window, it includes:

[0067] Set the window size of the sliding window to one period, and set the step size of the sliding window to a specified number of sampling points;

[0068] Move the window from the starting position of the preprocessed first-phase voltage signal and first-phase current signal according to the step size, and obtain the preprocessed first-phase voltage signal and first-phase current signal in the window at each position until the number of movements reaches the first specified number.

[0069] In this embodiment, the first specified number is R / 2, where R represents the number of sampling points for simultaneously collecting the phase voltage signal and phase current signal of the dry-type air-core reactor within one period at a specified sampling rate. The step size of the sliding window is 5. Therefore, in step S102, after preprocessing the sampled first-phase voltage signal and first-phase current signal, obtain the first R preprocessed first-phase voltage signals and first-phase current signals as the preprocessed first-phase voltage signal and first-phase current signal in the first window, obtain the preprocessed first-phase voltage signals and first-phase current signals from the 5th to the R + 5th as the preprocessed first-phase voltage signal and first-phase current signal in the second window, obtain the preprocessed first-phase voltage signals and first-phase current signals from the 10th to the R + 10th as the preprocessed first-phase voltage signal and first-phase current signal in the third window, and so on to obtain the preprocessed first-phase voltage signal and first-phase current signal in R / 2 windows.

[0070] In this embodiment, when calculating the corresponding real-time value of the power factor according to the preprocessed first-phase voltage signal and first-phase current signal in each window, and when calculating the reference value of the power factor according to the preprocessed second-phase voltage signal and second-phase current signal, both include:

[0071] S401) Perform a discrete Fourier transform on the voltage signal to obtain the real and imaginary parts of the voltage signal, and perform a discrete Fourier transform on the current signal to obtain the real and imaginary parts of the current signal;

[0072] S402) Divide the imaginary part of the voltage signal by the real part to obtain a first quotient value, calculate the arctangent value of the first quotient value to obtain the phase of the voltage signal, divide the imaginary part of the current signal by the real part to obtain a second quotient value, and calculate the arctangent value of the second quotient value to obtain the phase of the current signal;

[0073] S403) Calculate the cosine value of the difference between the phase of the voltage signal and the phase of the current signal to obtain the power factor.

[0074] Taking the voltage signal as an example, the expression for performing the discrete Fourier transform is as follows:

[0075]

[0076] Among them, N represents the number of sampling points, k represents the order of the sampling points, X(k) represents the value obtained after the discrete Fourier transform, and x(n) represents the original sequence

[0077] From the above formula, the expressions for the real and imaginary parts of the voltage signal are as follows:

[0078]

[0079]

[0080] Where X Re (k) is the real part of the voltage signal, X Im (k) is the imaginary part of the voltage signal;

[0081] The phase of the voltage signal calculated through the real and imaginary parts of the voltage information is:

[0082]

[0083] Similarly, the phase of the current signal can be calculated Then the power factor cosθ of the reactor is:

[0084]

[0085] In step S102 of this embodiment, when calculating the change rate of each real-time value of the power factor compared with the power factor reference value, the change rate expression is as follows:

[0086]

[0087] Among them, represents the power factor reference value, It represents the real-time value of the i-th power factor.

[0088] Furthermore, in step S103, the second specified quantity is 5, and the preset threshold is 10%. Therefore, if there are 5 it is determined that the dry-type air-core reactor has suffered an inter-turn short-circuit fault, and a corresponding alarm signal / cut-off signal is issued. If less than 5 step S101 is repeated.

[0089] This embodiment also proposes a dry-type air-core reactor inter-turn short-circuit fault detection system, including a computer, which is programmed or configured to execute the dry-type air-core reactor inter-turn short-circuit fault detection method described in this embodiment. Specifically, in this embodiment, the computer is programmed or configured to execute the following steps:

[0090] Step 1, after the dry-type air-core reactor is put into operation, the phase voltage and phase current of the dry-type air-core reactor are simultaneously collected within one cycle. R points are sampled per cycle, and the collected signals are preprocessed. By comparing the measured value with the estimated value, it is determined whether the measured value belongs to an abnormal point. If so, the estimated value is used to replace it; otherwise, the original signal is retained;

[0091] Step 2, the discrete Fourier transform is respectively performed on the processed voltage and current signal sequences to obtain the normal power factor value reference

[0092] Step 3, during the operation of the reactor, the phase voltage and phase current of the reactor are collected. R points are sampled per cycle. After the sampled data is processed, the first power factor value is calculated through the first R data The second power factor value is calculated through the 5th to the R + 5th The third power factor value is calculated through the 10th to the R + 10th By analogy, R / 2 power factor values are calculated, and their change rates compared with the normal power factor value reference are calculated.

[0093] Step 4, the change rates of the R / 2 power factor values calculated compared with the normal power factor value reference are calculated. If there are no less than 5 it is determined that the dry-type air-core reactor has suffered an inter-turn short-circuit fault, and a corresponding alarm signal / cut-off signal is issued. If less than 5 step 3 is repeated.

[0094] The feasibility of the method in this embodiment is verified through experiments. Taking the outdoor dry-type air-core series reactor with the model number CKGKL-10-31.5A-38.5mH as an example, its main parameters are shown in the following table. Based on the parameters under normal conditions and fault conditions obtained from the finite element simulation model, a Simulink circuit model is built, and the simulation is carried out for the reactor under normal conditions and when the fault manifestation is the weakest.

[0095] Table 1 Main parameters of dry-type air-core series reactor

[0096] Parameter Value Parameter Value Rated Voltage / kV 10 Frequency / Hz 50 Rated Current / A 31.5 Inner Diameter / mm 750 Number of Phases 1 Outer Diameter / mm 900 Inductance Value / mH 38.5 Number of Encapsulations 3

[0097] First, set the parameters of the reactor to the normal values and simulate the normal situation. After the dry-type air-core reactor is put into operation, collect the phase voltage and phase current of the dry-type air-core reactor within one cycle at the same time, perform denoising processing on the signals, and calculate the normal power factor value reference

[0098] Specifically, use the voltage transformer and the current transformers installed in the three phases A, B, and C to sample the reactor, sample 40 times per cycle, obtain the phase voltage and phase current of the reactor in real time, and then perform preprocessing on the signals. Determine whether the measured value belongs to an abnormal point by comparing the measured value with the estimated value. If so, replace it with the estimated value; otherwise, retain the original signal. The denoised phase voltage and phase current are as Figure 2 shown. Perform discrete Fourier transform calculations on the preprocessed voltage and current signal sequences respectively to obtain the normal power factor value reference

[0099] Then, use the method in this embodiment to detect faults for the dry-type air-core reactor under normal conditions and fault conditions respectively.

[0100] During the operation of the dry-type air-core reactor under normal operating conditions, collect the phase voltage and phase current in real time, sample 40 times per cycle, and perform denoising processing on the signals. The phase current and phase voltage of phase A collected are as Figure 3 (a) and Figure 3 (b) shown, and the denoised phase current and phase voltage of phase A are as Figure 3 (c) and Figure 3 (d) shown.

[0101] For the processed phase voltage and phase current, calculate the first power factor value through the first 40 data Calculate the second power factor value through the 5th to 45th data Calculate the third power factor value through the 10th to 50th data And so on, calculate 20 power factor values, and calculate their comparison with the power factor value reference Rate of change The calculation results are as Figure 4 shown If the number of points of is less than 5, it is judged that the current is in normal operation, and real-time sampling continues.

[0102] In the case of a fault, a turn-to-turn short circuit fault model of the reactor is established according to the parameters when the fault manifestation is the weakest obtained from the finite element simulation data (set the fault phase as phase A). During the operation of the reactor, the phase voltage and phase current of the reactor are collected in real time, sampled 40 times per cycle, 4 cycles are collected, and the signal is denoised. The phase current and phase voltage of the fault phase A Figure 5 (a) and Figure 5 (b) are shown. The denoised phase current and phase voltage of phase A are as Figure 5 (c) and Figure 5 (d) are shown;

[0103] For the processed phase voltage and phase current, the first power factor value is calculated through the first 40 data The second power factor value is calculated through the 5th to 45th data The third power factor value is calculated through the 10th to 50th data And so on, 20 power factor values are calculated, and their change rate compared with the normal power factor value reference Rate of change The calculation results are as Figure 6 shown If the number of points of is not less than 5, it is judged that the reactor has a turn-to-turn short circuit fault, and an alarm / trip signal is issued;

[0104] The simulation results show that the method of this embodiment is judged correctly and has high accuracy, effectiveness and reliability.

[0105] In summary, the present invention first collects the phase voltage and phase current of the dry-type air-core reactor under normal operation within one cycle, performs smoothing estimation processing on the sampling data, and calculates the normal power factor value reference by using the discrete Fourier transform method; then during the operation of the reactor, the phase voltage and phase current of the reactor are collected in real time. After processing the sampling data, multiple power factor values are calculated by using the sliding window method, and their change rate compared with the normal power factor value reference is calculated; according to the change rate situation, it is judged whether the dry-type air-core reactor has a turn-to-turn short circuit fault. The present invention improves the accuracy of the criterion, and at the same time has high sensitivity and reliability, can act timely and accurately during a fault, avoids the further expansion of the accident, and ensures the safe operation of the dry-type air-core reactor.

[0106] The above are only the preferred embodiments of the present invention and do not impose any formal restrictions on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for detecting inter-turn short circuit faults of a dry-type air-core reactor, characterized in that, It includes the following steps: S101) Obtain the first-phase voltage signal and the first-phase current signal of the dry-type air-core reactor to be detected in real time; S102) Preprocess the first-phase voltage signal and the first-phase current signal. Obtain the preprocessed first-phase voltage signal and the first-phase current signal in the first specified number of windows through a sliding window. Calculate the corresponding real-time power factor value according to the preprocessed first-phase voltage signal and the first-phase current signal in each window, and calculate the change rate of each real-time power factor value compared with the power factor reference value respectively; S103) If the number of real-time power factor values whose change rate is greater than the preset threshold reaches the second specified number, it is determined that the dry-type air-core reactor to be detected has a turn-to-turn short-circuit fault.

2. The method for detecting the turn-to-turn short circuit fault of the dry-type air-core reactor according to claim 1, characterized in that, Before step S101, there is also a step of calculating the power factor reference value, which specifically includes: Obtain the second-phase voltage signal and the second-phase current signal of the dry-type air-core reactor operating normally. Preprocess the second-phase voltage signal and the second-phase current signal, and calculate the power factor reference value according to the preprocessed second-phase voltage signal and the second-phase current signal.

3. The method for detecting the turn-to-turn short circuit fault of the dry-type air-core reactor according to claim 2, characterized in that, When preprocessing the first-phase voltage signal and the first-phase current signal, and when preprocessing the second-phase voltage signal and the second-phase current signal, both include: S201) Calculate the estimated value of each element in the data sequence; S202) If the absolute value of the difference between the measured value of the current element in the data sequence and the estimated value of the current element is greater than the given first threshold, replace the measured value of the current element with the estimated value of the current element.

4. The method for detecting the turn-to-turn short circuit fault of the dry-type air-core reactor according to claim 3, characterized in that, When calculating the estimated value of each element in the data sequence in step S201, it includes: S301) Traverse the data sequence x(n) through the first sliding window, and select the median of the data in each window respectively to obtain the data sequence x1(n); S302) Traverse the data sequence x1(n) through the second sliding window, and select the median of the data in each window respectively to obtain the data sequence x3(n); S303) Construct a smooth sequence x3(n) according to the elements in the data sequence x2(n). The value of each element in the smooth sequence x3(n) is the estimated value of each element in the data sequence.

5. The method for detecting the turn-to-turn short circuit fault of the dry-type air-core reactor according to claim 4, wherein, The window size of the first sliding window is 5 elements, and the step size is 1 element. The window size of the second sliding window is 3 elements, and the step size is 1 element. The expression of the elements in the smooth sequence x3(n) is as follows: x3(i) = 0.25x2(i - 1) + 0.5x2(i) + 0.25x2(i + 1) Where, x3(i) represents the i-th element in the smooth sequence x3(n), x2(i - 1) represents the (i - 1)-th element in the data sequence x2(n), x2(i) represents the i-th element in the data sequence x2(n), and x2(i + 1) represents the (i + 1)-th element in the data sequence x2(n).

6. The method for detecting the turn-to-turn short circuit fault of the dry-type air-core reactor according to claim 2, wherein When calculating the corresponding real-time power factor value according to the preprocessed first-phase voltage signal and the first-phase current signal in each window, and when calculating the power factor reference value according to the preprocessed second-phase voltage signal and the second-phase current signal, both include: S401) Perform a discrete Fourier transform on the voltage signal to obtain the real and imaginary parts of the voltage signal, and perform a discrete Fourier transform on the current signal to obtain the real and imaginary parts of the current signal; S402) Divide the imaginary part of the voltage signal by the real part to obtain a first quotient value, calculate the arctangent value of the first quotient value to obtain the phase of the voltage signal, divide the imaginary part of the current signal by the real part to obtain a second quotient value, and calculate the arctangent value of the second quotient value to obtain the phase of the current signal; S403) Calculate the cosine value of the difference between the phase of the voltage signal and the phase of the current signal to obtain the power factor.

7. The method for detecting the turn-to-turn short circuit fault of the dry-type air-core reactor according to claim 2, wherein When obtaining the second-phase voltage signal and the second-phase current signal of the dry-type air-core reactor operating normally, it includes: simultaneously collecting the second-phase voltage signal and the second-phase current signal of the dry-type air-core reactor operating normally within one cycle at a specified sampling rate; when obtaining the preprocessed first-phase voltage signal and the first-phase current signal in the first specified number of windows through a sliding window, it includes: setting the window size of the sliding window to one cycle, setting the step size of the sliding window to a specified number of sampling points, moving the window from the starting position of the preprocessed first-phase voltage signal and the first-phase current signal according to the step size, and obtaining the preprocessed first-phase voltage signal and the first-phase current signal in the window at each position until the number of movements reaches the first specified number.

8. The method for detecting the turn-to-turn short circuit fault of the dry-type air-core reactor according to claim 1, wherein, In step S102, when calculating the change rate of each real-time power factor value compared to the power factor reference value respectively, the change rate expression is as follows: Among them, represents the reference value of the power factor, represents the real-time value of the i-th power factor.

9. The method for detecting the inter-turn short circuit fault of the dry-type air-core reactor according to claim 1, characterized in that, The first specified number is R / 2, where R represents the number of sampling points for simultaneously collecting the phase voltage signal and the phase current signal of the dry-type air-core reactor within one cycle at a specified sampling rate, and the second specified number is 5.

10. A dry-type air-core reactor turn-to-turn short-circuit fault detection system, characterized in that, It includes a computer, and the computer is programmed or configured to execute the dry-type air-core reactor turn-to-turn short-circuit fault detection method according to any one of claims 1 to 9.

Images