A power distribution network fault location and impedance estimation method and system based on improved electromagnetic time reversal

Abstract

This invention provides a method and system for fault location and impedance estimation in distribution networks based on improved electromagnetic time reversal. The method includes: constructing an electromagnetic transient model of the distribution network under test; setting several potential fault locations and fault impedances in the distribution network under test; performing simulations using the electromagnetic transient model for each combination containing fault location and fault impedance to obtain the transfer function from the fault location to a preset measurement point; constructing a standardized matched filter signal library based on the transfer functions of all combinations; when a fault occurs in the distribution network under test, acquiring and differentiating the voltage response at the measurement point; obtaining the estimated time of the fault occurrence and the tolerance of the transient propagation time uncertainty in the distribution network under test to determine a time window; within the time window, calculating a score for each combination based on the differentiated signal and the standardized matched filter signal library, and taking the combination corresponding to the highest score as the fault location result.

Description

Technical Field

[0001] This invention relates to the field of power system relay protection and fault detection technology, and in particular to a method and system for fault location and impedance estimation in distribution networks based on improved electromagnetic time reversal. Background Technology

[0002] The power distribution network is a crucial component of the power system, responsible for transmitting electrical energy from the high-voltage grid to the user end. The reliability of the distribution network directly impacts the stability and security of the power supply. Distribution lines are widely distributed and operate in complex environments, making them susceptible to both natural and human factors, leading to frequent faults. Rapid and accurate fault location is key to reducing power outage time and improving power supply reliability.

[0003] Among existing technologies, fault location methods based on electromagnetic time reversal (EMTR) have shown great potential. The core of this method is to reverse the measured transient fault signal in time and re-inject it into the digital simulation model of the system. This typically involves a hypothetical fault, measuring the simulated signal at the hypothetical fault location, and determining the fault location by finding the energy focal point. Rapidly and accurately locating short-circuit faults in power systems, enabling timely fault removal and preventing further interruptions and losses, is crucial for the continuous and reliable supply of power. Summary of the Invention

[0004] To address the shortcomings of existing EMTR (Electromagnetic Time Reversal) technologies, such as inaccurate fault location for high impedance, sensitivity to transient arrival time errors, and poor adaptability to complex power grid topologies, this invention provides a method and system for distribution network fault location and impedance estimation based on improved electromagnetic time reversal. This method enhances robustness and estimation capabilities for fault impedance, as well as robustness to transient arrival time errors. This invention is applicable to distribution networks with complex topologies and a high proportion of distributed generation, enabling high-precision and robust fault location and impedance estimation.

[0005] In a first aspect, the present invention provides a method for fault location and impedance estimation in distribution networks based on improved electromagnetic time reversal, comprising: an offline preprocessing stage and an online location stage;

[0006] The offline preprocessing stage includes:

[0007] Construct an electromagnetic transient model of the distribution network under test, the electromagnetic transient model including the high-frequency characteristics of the transformer;

[0008] Several potential fault locations and fault impedances are set in the distribution network under test; for each combination containing fault location and fault impedance, the electromagnetic transient model is used for simulation to obtain the transfer function from the fault location to the preset measurement point; a standardized matched filter signal library is constructed based on the transfer functions of all combinations.

[0009] The online positioning phase includes:

[0010] When a fault occurs in the distribution network under test, the voltage response at the measurement point is acquired, and the voltage response is differentiated.

[0011] Tolerances for obtaining the estimated time T of a fault in the distribution network under test and the uncertainty of transient propagation time To determine the time window ;

[0012] In the time window Within this framework, a score is calculated for each combination based on the differentiated signal and the standardized matched filter signal library.

[0013] Find the highest score among all scores, and use the combination corresponding to the highest score as the fault location result.

[0014] Furthermore, the standardized matched filter signal library constructed based on the transfer functions of all combinations specifically includes:

[0015] For each combination The transfer function of the normalized matched filter signal is calculated according to the following formula. :

[0016]

[0017] in, An indicator showing the location of the fault. The fault impedance is represented by t, and time is represented by t. Indicates from the fault location The transfer function to the preset measurement point m; This represents the transfer function after time reversal;

[0018] By integrating all the matched filter signals corresponding to the combinations, a standardized matched filter signal library is obtained.

[0019] Furthermore, in the electromagnetic transient model, the transformer adopts an equivalent circuit model that includes stray capacitance to ground, magnetizing inductance, iron loss resistance, and winding capacitance.

[0020] Furthermore, the formula for calculating the score is as follows:

[0021]

[0022] in, The voltage response at the preset measurement point m, Indicates to Perform differentiation, Indicate combination The rating.

[0023] Secondly, the present invention provides a distribution network fault location and impedance estimation system based on improved electromagnetic time reversal, comprising:

[0024] The power grid model construction module is used to construct an electromagnetic transient model of the distribution network under test, wherein the electromagnetic transient model includes the high-frequency characteristics of the transformer;

[0025] The signal library construction module is used to set several potential fault locations and fault impedances in the distribution network under test; for each combination containing fault location and fault impedance, the electromagnetic transient model is used for simulation to obtain the transfer function from the fault location to the preset measurement point; a standardized matched filter signal library is constructed based on the transfer functions of all combinations.

[0026] The fault combination scoring module is used to acquire the voltage response at the measurement point when a fault occurs in the distribution network under test, differentiate the voltage response, and acquire the estimated time T of the fault occurrence and the tolerance of the transient propagation time uncertainty. To determine the time window ; in the time window Within this framework, a score is calculated for each combination based on the differentiated signal and the standardized matched filter signal library.

[0027] The search module is used to find the highest score value among all scores and use the combination corresponding to the highest score value as the fault location result.

[0028] Thirdly, the present invention provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the program, implements the method as described in the first aspect.

[0029] Fourthly, the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the method described in the first aspect.

[0030] The beneficial effects of this invention are as follows:

[0031] 1. This invention realizes the principle of matched filter through signal differentiation and transfer function, and has extremely high normalized positioning accuracy and success rate. It exhibits a very high fault location success rate for high impedance faults and complex topology networks.

[0032] 2. This invention, by differentiating and normalizing the signal, is insensitive to the arrival time error of transient signals, does not require a complex transient start point detection algorithm, and has strong robustness.

[0033] 3. This invention can accurately estimate the fault impedance while locating the fault, providing more information for fault analysis and system recovery, and realizing synchronous impedance estimation.

[0034] 4. The present invention can still maintain superior performance under non-ideal conditions such as measurement noise, low sampling rate and load variation. Attached Figure Description

[0035] Figure 1 A flowchart illustrating a method for fault location and impedance estimation in a distribution network based on an improved electromagnetic time reversal, provided in an embodiment of the present invention.

[0036] Figure 2 The complex power distribution network topology provided in this embodiment of the invention; wherein, red dots represent measurement points and blue dots represent network centers;

[0037] Figure 3 A schematic diagram of a distribution network fault location and impedance estimation system based on improved electromagnetic time reversal provided in an embodiment of the present invention;

[0038] Figure 4 This is a structural block diagram of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0040] like Figure 1 As shown, this embodiment of the invention provides a method for fault location and impedance estimation in distribution networks based on improved electromagnetic time reversal. The method includes two stages: an offline preprocessing stage and an online location stage.

[0041] The offline preprocessing stage includes the following steps:

[0042] S101: Construct an electromagnetic transient model of the distribution network under test, wherein the electromagnetic transient model includes the high-frequency characteristics of the transformer;

[0043] Specifically, EMTP or similar electromagnetic transient simulation software can be used to construct the electromagnetic transient model of the distribution network under test. This invention aims to address complex topological distribution networks and high-impedance faults, overcoming the limitations of existing EMTR-based technologies. Therefore, when constructing the electromagnetic transient model of the distribution network under test, a frequency converter transformer model is used to replace the simple resistor used in previous models; this transformer employs an equivalent circuit model including stray capacitance to ground, magnetizing inductance, iron loss resistance, and winding capacitance.

[0044] S102: Set several potential fault locations and fault impedances in the distribution network under test; for each combination containing fault location and fault impedance, use the electromagnetic transient model to perform simulation to obtain the transfer function from the fault location to the preset measurement point; construct a standardized matched filter signal library based on the transfer functions of all combinations.

[0045] Specifically, this step aims to simulate various fault scenarios that may occur in the distribution network under test using the constructed electromagnetic transient model, thereby constructing matched filter signals under various fault scenarios. This provides a reference for fault location and impedance location during the online fault location phase. This step does not limit the number of preset measurement points; it can be one or more.

[0046] For example, for a potential fault location And the fault impedance Z, in the simulation, at the fault location A pulsed current source is applied, and the voltage response is recorded at a fixed measurement point m in the substation using a voltage sensor. Based on the input pulsed current source and the recorded voltage response, the voltage from the fault location can be calculated using the transfer function formula. Transfer function to a certain measurement point m t represents time; when the input current source is a unit pulse current excitation, the voltage response measured at the measurement point m is the transfer function; the fault impedance Z refers to the fault location. The impedance at the fault location. Generally speaking, the type of fault in the distribution network can be basically deduced by combining the fault location and the fault impedance.

[0047] In this embodiment, the construction process of the standardized matched filter signal library includes:

[0048] For each combination The transfer function of the normalized matched filter signal is calculated according to the following formula. :

[0049]

[0050] in, An indicator showing the location of the fault. The fault impedance is represented by t, and time is represented by t. Indicates from the fault location The transfer function to the preset measurement point m; This represents the transfer function after time reversal;

[0051] By integrating all the matched filter signals corresponding to the combinations, a standardized matched filter signal library is obtained.

[0052] The online positioning phase includes the following steps:

[0053] S103: When a fault occurs in the distribution network under test, a high sampling rate voltage sensor in the kHz to MHz range is preferentially selected to record the voltage response at the preset measurement point. , in response to the voltage Perform differentiation;

[0054] Specifically, the differential processing in this step involves calculating the numerical difference between the measured point signals. This step aims to convert the voltage step caused by the fault into a pulse, highlighting the high-frequency transient characteristics and suppressing steady-state component interference.

[0055] S104: Obtain the estimated time T of the fault occurrence and the tolerance of the transient propagation time uncertainty in the distribution network under test. To determine the time window ;

[0056] S105: In the time window Internally, based on the differentiated signal The score for each combination is calculated using the standardized matched filter signal library; the scoring formula is as follows:

[0057]

[0058] in, Indicate combination The rating;

[0059] The scoring formula represents: the differentiated signal With each signal in the standardized matched filter signal library Perform convolution operations and within the time window Find the convolution result with the largest value as the combination. The rating.

[0060] Traditional EMTR methods use fault current signal energy (FCSE) or maximum value (L-Max) as the scoring criterion, but these methods degrade in high-impedance faults or complex networks. The Time Offset Maximum Derivative (TOMD) method proposed in this invention does not directly use the measured voltage. Instead, first measure the voltage. Differentiation converts the step changes caused by the fault into pulse signals, thus enabling better extraction of high-frequency transient information. Furthermore, by defining a time window, scoring over longer periods is unnecessary, thereby reducing computational load.

[0061] S106: Find the highest score value among all scores, and use the combination corresponding to the highest score value as the fault location result.

[0062] Specifically, compare the scores under all fault locations and fault impedance combinations. The fault location corresponding to the highest-scoring combination. The final actual fault location is determined. Simultaneously, the fault impedance Z corresponding to the highest-scoring combination is determined as the estimated fault impedance.

[0063] To verify the effectiveness of the present invention, the present invention also provides the following experiments.

[0064] (1) Offline preprocessing

[0065] This experiment uses a complex power distribution network with a total length of 83.3 kilometers and 101 branches (such as...). Figure 2 Taking the example shown, an accurate electromagnetic transient model of this complex power distribution network is established using EMTP or similar electromagnetic transient simulation software. The transformers include stray capacitance to ground. Magnetizing inductor Iron loss resistance and winding capacitor The equivalent circuit model is obtained. A potential fault location is set every 100 meters on all line branches, thus obtaining a set of potential fault locations; and a set of fault impedances is also established. Assuming there are N fault locations and M fault impedances, then N*M fault locations can be obtained. The combination of fault impedance Z; for each fault location In the simulation, the combination of the fault impedance Z and the voltage response is recorded by a voltage sensor at a fixed measurement point m in the substation. The transfer function is then obtained according to the formula. Following the steps in the above embodiments, time reversal and L2 norm normalization are performed to construct a large, standardized matched filter signal library, which is then stored in the positioning server.

[0066] (2) Online positioning

[0067] When a ground fault occurs in the distribution network, the voltage sensors in the substation record transient data of the fault. The data is then uploaded to the location server via a communication network. The location server automatically performs [the necessary actions]. Perform numerical differentiation, and compare the differentiated signal with all signals in the signal library. Perform convolution to obtain the TOMD score matrix; Find the maximum value within the window, search for the global maximum value of the score matrix, assuming its corresponding index is ( =Branch L45, 850m from the beginning, Z=500 The server outputs the final location result as, "The fault is located on branch L45, 850 meters from the beginning, with a fault impedance of approximately 500 ohms." This result is then sent to the maintenance personnel.

[0068] Based on the same inventive concept, such as Figure 3 As shown in the figure, the present invention also provides a distribution network fault location and impedance estimation system based on improved electromagnetic time reversal, including a power grid model construction module, a signal library construction module, a fault combination scoring module and a search module.

[0069] The system includes several modules: a power grid model construction module for building an electromagnetic transient model of the distribution network under test, including the high-frequency characteristics of transformers; a signal library construction module for setting several potential fault locations and fault impedances in the distribution network under test; for each combination containing fault location and fault impedance, simulation is performed using the electromagnetic transient model to obtain the transfer function from the fault location to a preset measurement point; a standardized matched filter signal library is constructed based on the transfer functions of all combinations; and a fault combination scoring module for obtaining the voltage response at the measurement point when a fault occurs in the distribution network under test, differentiating the voltage response, and obtaining the estimated time T of the fault occurrence and the tolerance of the transient propagation time uncertainty. To determine the time window ; in the time window Within the system, a score is calculated for each combination based on the differentiated signal and the standardized matched filter signal library; the search module is used to find the maximum score value from all scores, and the combination corresponding to the maximum score value is used as the fault location result.

[0070] It should be noted that the distribution network fault location and impedance estimation system based on improved electromagnetic time reversal provided in this embodiment of the invention is for implementing the above method. Its specific functions can be referred to the above method embodiment, and will not be repeated here.

[0071] Figure 4 An example is a schematic diagram of the physical structure of an electronic device, such as... Figure 4 As shown, the electronic device may include: a processor 401, a communication interface 402, a memory 403, and a communication bus 404, wherein the processor 401, the communication interface 402, and the memory 403 communicate with each other through the communication bus 404. Processor 401 can call logic instructions in memory 403 to execute a distribution network fault location and impedance estimation method based on improved electromagnetic time reversal. This method includes an offline preprocessing stage and an online location stage. The offline preprocessing stage includes: constructing an electromagnetic transient model of the distribution network under test, the electromagnetic transient model including the high-frequency characteristics of transformers; setting several potential fault locations and fault impedances in the distribution network under test; performing simulation using the electromagnetic transient model for each combination containing fault location and fault impedance to obtain the transfer function from the fault location to a preset measurement point; and constructing a standardized matched filter signal library based on the transfer functions of all combinations. The online location stage includes: when a fault occurs in the distribution network under test, obtaining the voltage response at the measurement point and differentiating the voltage response; obtaining the estimated time T of the fault occurrence in the distribution network under test and the tolerance of the transient propagation time uncertainty. To determine the time window ; in the time window Within the system, a score is calculated for each combination based on the differentiated signal and the standardized matched filter signal library; the maximum score value is found among all scores, and the combination corresponding to the maximum score value is taken as the fault location result.

[0072] Furthermore, when the logical instructions in the aforementioned memory 403 are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0073] This invention also provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, and when the program instructions are executed by a computer, the computer can execute the distribution network fault location and impedance estimation method based on improved electromagnetic time reversal provided in the above-described method embodiments.

[0074] This invention also provides a non-transitory computer-readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it implements the method for fault location and impedance estimation of distribution networks based on improved electromagnetic time reversal provided in the above-described method embodiments.

[0075] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fault location and impedance estimation in distribution networks based on improved electromagnetic time reversal, characterized in that, include: Offline preprocessing stage and online positioning stage; The offline preprocessing stage includes: Construct an electromagnetic transient model of the distribution network under test, the electromagnetic transient model including the high-frequency characteristics of the transformer; Several potential fault locations and fault impedances are set in the distribution network under test; for each combination containing fault location and fault impedance, the electromagnetic transient model is used for simulation to obtain the transfer function from the fault location to the preset measurement point; a standardized matched filter signal library is constructed based on the transfer functions of all combinations. The online positioning phase includes: When a fault occurs in the distribution network under test, the voltage response at the measurement point is acquired, and the voltage response is differentiated. Tolerances for obtaining the estimated time T of a fault in the distribution network under test and the uncertainty of transient propagation time To determine the time window ; In the time window Within this framework, a score is calculated for each combination based on the differentiated signal and the standardized matched filter signal library. Find the highest score among all scores, and use the combination corresponding to the highest score as the fault location result.

2. The method for fault location and impedance estimation in distribution networks based on improved electromagnetic time reversal as described in claim 1, characterized in that, The standardized matched filter signal library constructed based on the transfer functions of all combinations specifically includes: For each combination The transfer function of the normalized matched filter signal is calculated according to the following formula. : in, An indicator showing the location of the fault. The fault impedance is represented by t, and time is represented by t. Indicates from the fault location The transfer function to the preset measurement point m; This represents the transfer function after time reversal; By integrating all the matched filter signals corresponding to the combinations, a standardized matched filter signal library is obtained.

3. The method for distribution network fault location and impedance estimation based on improved electromagnetic time reversal as described in claim 1, characterized in that, In the electromagnetic transient model, the transformer adopts an equivalent circuit model that includes stray capacitance to ground, magnetizing inductance, iron loss resistance, and winding capacitance.

4. The method for fault location and impedance estimation in distribution networks based on improved electromagnetic time reversal as described in claim 2, characterized in that, The formula for calculating the score is: in, The voltage response at the preset measurement point m, Indicates to Perform differentiation, Indicate combination The rating.

5. A distribution network fault location and impedance estimation system based on improved electromagnetic time reversal, characterized in that, include: The power grid model construction module is used to construct an electromagnetic transient model of the distribution network under test, wherein the electromagnetic transient model includes the high-frequency characteristics of the transformer; The signal library construction module is used to set several potential fault locations and fault impedances in the distribution network under test; For each combination containing fault location and fault impedance, the electromagnetic transient model is used for simulation to obtain the transfer function from the fault location to the preset measurement point; a standardized matched filter signal library is constructed based on the transfer functions of all combinations. The fault combination scoring module is used to acquire the voltage response at the measurement point when a fault occurs in the distribution network under test, differentiate the voltage response, and acquire the estimated time T of the fault occurrence and the tolerance of the transient propagation time uncertainty. To determine the time window ; in the time window Within this framework, a score is calculated for each combination based on the differentiated signal and the standardized matched filter signal library. The search module is used to find the highest score value among all scores and use the combination corresponding to the highest score value as the fault location result.

6. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the method as described in any one of claims 1 to 4.

7. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1 to 4.

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