Distribution network traveling wave fault positioning precision improving method

Abstract

The invention relates to a distribution network traveling wave fault positioning precision improving method. The method comprises the steps that traveling wave current data are collected in real time through a terminal FTU; through a VMD-SDEO algorithm, the wave-front arrival time and the traveling wave propagation speed of the traveling wave are determined; adopting RTK to measure the actual length # imgabs0 # of a sample line to initialize a double-end traveling wave positioning formula; calculating error amounts, wherein the types of the error amounts comprise a sampling frequency effect error # imgabs 1 #, a synchronization time error epsilon t, a wave velocity error # imgabs 2 # and a line length error epsilon L; the error amount is introduced into the initialized double-end traveling wave positioning formula, and a final double-end traveling wave positioning formula is formed and used for traveling wave fault positioning. According to the method, sampling frequency effect errors are fully considered, synchronization time errors, wave velocity errors and line length errors are determined through corresponding specifications and operation and maintenance requirements and substituted into the initialized double-end traveling wave positioning formula to obtain a final equation, the error amount of related types is fully considered, and the fault positioning precision is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a method for improving the accuracy of locating traveling wave faults in a distribution network. Background Art

[0002] The modern power distribution system is a complex network topology. A complete power distribution network is often responsible for the transmission of power in multiple regions. When a permanent fault occurs in a distribution line, if it is not handled in time, it will impact the associated system, causing large-scale power outages and affecting normal social production and life. Therefore, it is of great significance to accurately and reliably locate the faults of the distribution network with complex topology, quickly troubleshoot and eliminate the faults, and restore the normal operation of the line to ensure the safe and stable operation of the power grid.

[0003] Traveling wave positioning technology plays an important role in distribution network fault detection due to its high precision and fast response. By capturing and analyzing the traveling wave signal generated when a fault occurs, the fault point can be accurately located in a short time, significantly improving the speed of fault handling. However, the fault location method based on two-end traveling waves is susceptible to various errors, including the uncertainty of the traveling wave velocity caused by the influence of line electrical parameters, the inaccurate estimated line length, the wavefront arrival time error caused by the low amplitude of the traveling wave, and the Beidou time synchronization error. There is still much room for improvement in its positioning accuracy.

[0004] Specifically, the current fault location technology still has the following defects: (1) The establishment of the traveling wave front time and wave speed is still mainly based on manual calibration and empirical values, which has large errors; (2) The various parameters of the current two-end traveling wave location method do not fully consider the error impact, and do not consider the sampling frequency information, so there is much room for improvement in accuracy. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for improving the accuracy of locating traveling wave faults in a distribution network to overcome the deficiencies in the above-mentioned prior art.

[0006] The technical solution of the present invention to solve the above technical problem is as follows: A method for improving the accuracy of locating traveling wave faults in a distribution network comprises the following steps:

[0007] Step S01: collecting traveling wave current data in real time through the terminal FTU;

[0008] Step S02: Determine the wavefront arrival time and the propagation speed of the traveling wave by using the VMD-SDEO algorithm; measure the actual length of the sample line by using RTK

[0009] Step S03: Initialize the two-terminal traveling wave positioning formula based on the traveling wave front arrival time, the traveling wave propagation speed and the actual length of the sample line;

[0010] Step S04: Calculate the error amount, the error amount type includes sampling frequency effect error Synchronization time error ε t , wave velocity error and line length error ε L ;

[0011] Step S05: Introduce the error amount into the initialized two-terminal traveling wave positioning formula, and form a final two-terminal traveling wave positioning formula for traveling wave fault positioning.

[0012] The beneficial effects of the present invention are as follows: the VMD-SDEO algorithm is used to calibrate the traveling wavefront arrival time and the traveling wave propagation speed, thereby avoiding the errors existing in the traditional manual calibration and empirical value methods; RTK is then used to measure the actual length of the sample line to establish the initial two-end traveling wave positioning formula; finally, the sampling frequency effect error is fully considered, and the synchronization time error, wave speed error and line length error are established through corresponding specifications and operation and maintenance requirements, and are substituted into the initialized two-end traveling wave positioning formula to obtain the final equation, which fully considers the error amount of related types and greatly improves the accuracy of fault location.

[0013] Based on the above technical solution, the present invention can also be improved as follows.

[0014] Further, step S02 specifically includes the following steps:

[0015] Step S21: Decomposing the traveling wave current data of the i side collected in step S01 by VMD algorithm to obtain the modal function IMFn;

[0016] Step S22: determining the most suitable intrinsic modal function for determining the arrival time of the fault traveling wave according to the envelope entropy of each modal function;

[0017] Step S23: Use the SDEO operator to calculate the energy spectrum of the intrinsic mode function to calibrate the arrival time t of the fault traveling wave Fi ;

[0018] Step S24: According to the relationship between frequency and wave velocity, the traveling wave propagation velocity used for fault location is adjusted according to the center frequency of the modal function with the largest envelope entropy; the corresponding line mode traveling wave propagation velocity is obtained by combining the line parameters and the wave velocity results of the distribution line.

[0019] Step S25: Based on the above steps, the arrival time t of the fault traveling wave at the monitoring terminal j can be obtained in the same way. Fj and the corresponding line mode traveling wave propagation velocity The total line wave propagation velocity is:

[0020]

[0021] Step S26: Use RTK to measure the actual length of the sample line

[0022] Further, the two-terminal traveling wave positioning formula after initialization in step S03 is:

[0023]

[0024] Furthermore, the sampling frequency effect error in step S04 The specific calculation method is:

[0025] At terminal i, the traveling current is s The related discrete fault start time is The discrete fault start time used as a reference is:

[0026]

[0027] where k F / f s ≤t F <(k F +1) / f s , is the maximum integer value not greater than *; the fault start time error related to the sampling frequency is obtained as follows:

[0028]

[0029] in

[0030] The first effective wavefront arrival time k at terminal i in the discrete time domain Fi / f s for:

[0031]

[0032] Where (k Fi -1) / f s <t Fi ≤k Fi / f s ; The fault start time error related to the sampling frequency is obtained as:

[0033]

[0034] Due to t Fi =t F +d Fi / v, then:

[0035]

[0036] By the same logic as above, we can calculate The total sampling frequency effect error is then for:

[0037]

[0038] Knowable The approximate calculation

[0039] Furthermore, the synchronization time error ε in step S04 t The calculation methods include:

[0040] Insert the influence of Beidou into the time particle and take ε approximately when calculating. t =2μs.

[0041] Furthermore, the wave velocity error in step S04 The calculation method includes: using the maximum percentage P v To cover the uncertainty in the velocity estimate, instead of epsilon v , when calculating, take P v <3%.

[0042] Furthermore, the line length error ε in step S04 L The calculation method includes: introducing the line length error ε L , ε is taken approximately when calculating L <0.3.

[0043] Further, the final two-terminal traveling wave positioning formula in step S05 is specifically:

[0044] BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is the overall flow chart of the present invention;

[0046] Figure 2 This is a schematic diagram of the device installation method;

[0047] Figure 3 The traveling wave current data measured by the monitoring terminal i of the present invention;

[0048] Figure 4 is the IMFn component diagram of the present invention;

[0049] Figure 5 is the SDEO energy spectrum of the modal function IMF2 of the present invention;

[0050] Figure 6 It is a spectrum diagram of the modal function IMF2 of the present invention;

[0051] Figure 7This is a line wave speed relationship diagram of the present invention. DETAILED DESCRIPTION

[0052] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0053] like Figure 1 to Figure 7 As shown, in embodiment 1, a method for improving the accuracy of locating traveling wave faults in a distribution network comprises the following steps:

[0054] Step S01: collecting traveling wave current data in real time through the terminal FTU;

[0055] Step S02: Determine the wavefront arrival time and the propagation speed of the traveling wave by using the VMD-SDEO algorithm; measure the actual length of the sample line by using RTK

[0056] Step S03: Initialize the two-terminal traveling wave positioning formula based on the traveling wave front arrival time, the traveling wave propagation speed and the actual length of the sample line;

[0057] Step S04: Calculate the error amount, the error amount type includes sampling frequency effect error Synchronization time error ε t , wave velocity error and line length error ε L ;

[0058] Step S05: Introduce the error amount into the initialized two-terminal traveling wave positioning formula, and form a final two-terminal traveling wave positioning formula for traveling wave fault positioning.

[0059] The VMD-SDE0 algorithm is used to calibrate the traveling wavefront arrival time and traveling wave propagation speed, avoiding the errors existing in traditional manual calibration and empirical value methods. RTK is then used to measure the actual length of the sample line to establish the initial two-end traveling wave positioning formula. Finally, the sampling frequency effect error is fully considered, and the synchronization time error, wave speed error and line length error are established through corresponding specifications and operation and maintenance requirements. These are substituted into the initialized two-end traveling wave positioning formula to obtain the final equation, which fully considers the error amount of related types and greatly improves the accuracy of fault location.

[0060] Embodiment 2: This embodiment is a further improvement on the basis of embodiment 1, and its details are as follows:

[0061] Step S02 specifically includes the following steps:

[0062] Step S21: Using VMD algorithm (variational mode decomposition algorithm) to process the traveling wave current data (such as Figure 3) is decomposed to obtain the modal function IMFn, such as Figure 4 As shown;

[0063] Step S22: Determine the most suitable intrinsic modal function for determining the arrival time of the fault traveling wave according to the envelope entropy of each modal function; As shown in Table 1, the second intrinsic modal function I MF2 is determined as the most suitable intrinsic modal function for determining the arrival time of the fault traveling wave according to the envelope entropy of each modal function:

[0064] Table 1 Envelope entropy of each mode function

[0065] Modal Function IMF1 IMF2 IMF3 Envelope Entropy 6.5228 6.5654 6.2856

[0066] Step S23: Use the SDE0 operator to calculate the energy spectrum of the intrinsic mode function IMF2 to calibrate the arrival time t of the fault traveling wave Fi The processing results are as follows Figure 5 As shown;

[0067] Step S24: According to the relationship between frequency and wave speed, the traveling wave propagation speed used for fault location is adjusted according to the center frequency of the modal function with the largest envelope entropy; the center frequency result of IMF2 is as follows: Figure 6 As shown, combined with the line parameters and the wave velocity results of the distribution line (such as Figure 7 As shown), the corresponding line mode traveling wave propagation speed is

[0068] Step S25: Based on the above steps, the arrival time t of the fault traveling wave at the monitoring terminal j can be obtained in the same way. Fj and the corresponding line mode traveling wave propagation velocity The total line wave propagation velocity is:

[0069]

[0070] Step S26: Use RTK to measure the actual length of the sample line

[0071] Embodiment 3, this embodiment is a further improvement on the basis of embodiment 2, and its details are as follows:

[0072] The double-terminal traveling wave positioning formula after initialization in step S03 is:

[0073]

[0074] Embodiment 4: This embodiment is a further improvement on the basis of embodiment 1, and its details are as follows:

[0075] Sampling frequency effect error in step S04 The specific calculation method is:

[0076] like Figure 2 As shown, considering the sampling frequency f s The sampled discrete-time traveling wave current has an effective wavefront arrival time greater than the wavefront arrival time, i.e. k Fi / f s ≥t Fi and k Fj / f s ≥t Fj , which will inevitably affect the accuracy of the fault location estimation method; in order to establish the final fault location equation in continuous time, the reference time t F and discrete fault onset time k F / f s Essential; k F is the fault starting sampling point, k Fi and k Fj are the i-th and j-th samples of the discrete first effective wavefront arrival time, respectively;

[0077] Reference time t F is a continuous value; at terminal i, the traveling current is at f s The related discrete fault start time is Therefore, the discrete fault onset time used as a reference is:

[0078]

[0079] where k F / f s ≤t F <(k F +1) / f s , is the largest integer value not greater than * (floor operator); the error in the fault initiation time associated with the sampling frequency is obtained as:

[0080]

[0081] in

[0082] The first effective wavefront arrival time k at terminal i in the discrete time domain Fi / f s for:

[0083]

[0084] Where (k Fi -1) / f s <t Fi ≤k Fi / f s ; The fault start time error related to the sampling frequency is obtained as:

[0085]

[0086] Due to t Fi =t F +d Fi / v, then:

[0087]

[0088] By the same logic as above, we can calculate The total sampling frequency effect error is then for:

[0089]

[0090] Knowable The approximate calculation

[0091] Embodiment 5, this embodiment is a further improvement on the basis of embodiment 1, and its details are as follows:

[0092] The synchronization time error ε in step S04 t The calculation methods include:

[0093] The BeiDou satellite navigation system can provide time information with an accuracy of more than 1 μs anywhere in the world. In conventional fault location estimation, the synchronization time error ε is increased. t , insert the influence of Beidou into the time particle, and take ε approximately when calculating t =2μs.

[0094] Embodiment 6: This embodiment is a further improvement on the basis of embodiment 1, and its details are as follows:

[0095] Wave velocity error in step S04 The calculation methods include:

[0096] Taking into account the uncertainty in the propagation velocity estimate, the unknown actual velocity v is given by the estimated velocity and error ε v Given, that is But the speed deviation is a percentage of the actual speed, which is also unknown. Therefore, the maximum percentage P can be used v To cover the uncertainty in the velocity estimate, instead of epsilon v , when calculating, take P v <3%.

[0097] Embodiment 7, this embodiment is a further improvement on the basis of embodiment 1, and its details are as follows:

[0098] The line length error ε in step S04 L The calculation methods include:

[0099] The line length of RTK measurement is greatly affected by the environment, and this parameter also provides uncertainty for fault location. In the conventional fault location estimation defined, the uncertainty of line length needs to introduce the line length error ε L , approximate ε in calculation L <0.3%.

[0100] Embodiment 8: This embodiment is a further improvement on the basis of embodiment 3, and its details are as follows:

[0101] The final two-terminal traveling wave positioning formula in step S05 is specifically:

[0102]

[0103] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for improving the accuracy of locating traveling wave faults in a distribution network, characterized in that: The steps include: Step S01: collecting traveling wave current data in real time through the terminal FTU; Step S02: Determine the wavefront arrival time and the propagation speed of the traveling wave by using the VMD-SDEO algorithm; measure the actual length of the sample line by using RTK Step S03: initializing a two-terminal traveling wave positioning formula based on the traveling wave front arrival time, the traveling wave propagation speed and the actual length of the sample line; Step S04: Calculate the error amount, the type of error amount includes sampling frequency effect error Synchronization time error ε t , wave velocity error and line length error ε L ; Step S05: Introducing the error amount into the initialized two-terminal traveling wave positioning formula, and forming a final two-terminal traveling wave positioning formula for traveling wave fault positioning.

2. A method for improving the accuracy of locating traveling wave faults in a distribution network according to claim 1, characterized in that: The step S02 specifically includes the following steps: Step S21: Decomposing the traveling wave current data of the i side collected in step S01 by VMD algorithm to obtain a modal function IMFn; Step S22: determining the most suitable intrinsic modal function for determining the arrival time of the fault traveling wave according to the envelope entropy of each modal function; Step S23: Calculate the energy spectrum of the intrinsic mode function using the SDEO operator to calibrate the arrival time t of the fault traveling wave Fi ; Step S24: According to the relationship between frequency and wave velocity, the traveling wave propagation velocity used for fault location is adjusted according to the center frequency of the modal function with the largest envelope entropy; the corresponding line mode traveling wave propagation velocity is obtained by combining the line parameters and the wave velocity results of the distribution line. Step S25: Based on the above steps, the arrival time t of the fault traveling wave at the monitoring terminal j can be obtained in the same way. Fj and the corresponding line mode traveling wave propagation velocity The total line wave propagation velocity is: Step S26: Using RTK to measure the actual length of the sample route 3. A method for improving the accuracy of locating traveling wave faults in a distribution network according to claim 2, characterized in that: The two-terminal traveling wave positioning formula after initialization in step S03 is:

4. A method for improving the accuracy of locating traveling wave faults in a distribution network according to claim 1, characterized in that: The sampling frequency effect error in step S04 The specific calculation method is: At terminal i, the traveling current is s The related discrete fault start time is The discrete fault start time used as a reference is: where k F / f s ≤t F <(k F +1) / f s , is the maximum integer value not greater than *; the fault start time error related to the sampling frequency is obtained as follows: in The first effective wavefront arrival time k at terminal i in the discrete time domain Fi / f s for: Where (k Fi -1) / f s <t Fi ≤k Fi / f s ; The fault start time error related to the sampling frequency is obtained as: Due to t Fi =t F +d Fi / v, then: By the same logic as above, we can calculate The total sampling frequency effect error is then for: Knowable The approximate calculation 5. A method for improving the accuracy of locating traveling wave faults in a distribution network according to claim 1, characterized in that: The synchronization time error ε in step S04 t The calculation methods include: Insert the influence of Beidou into the time particle and take ε approximately when calculating. t =2μs.

6. A method for improving the accuracy of locating traveling wave faults in a distribution network according to claim 1, characterized in that: The wave speed error in step S04 The calculation method includes: using the maximum percentage P v To cover the uncertainty in the velocity estimate, use instead of epsilon v , when calculating, take P v <3%.

7. A method for improving the accuracy of locating traveling wave faults in a distribution network according to claim 1, characterized in that: The line length error ε in step S04 L Calculation method Including: Introducing line length error ε L , approximate ε in calculation L <0.3%.

8. A method for improving the accuracy of locating traveling wave faults in a distribution network according to claim 3, characterized in that: The final two-terminal traveling wave positioning formula in step S05 is specifically:

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