A method and system for measuring impedance of a power distribution line

Abstract

This invention discloses a method and system for measuring the impedance of power distribution lines, relating to the field of low-voltage power distribution network technology. It effectively reduces impedance estimation errors and improves impedance measurement accuracy. The method includes: determining a reference meter for the power meter of the line under test; acquiring a first voltage of the reference meter and a second voltage of the power meter of the line under test; performing error correction processing on the second voltage to obtain an error-corrected second voltage, wherein the error correction processing includes at least one of phase deviation correction processing and neutral line voltage drop compensation processing; and acquiring the impedance information of the line under test based on the first voltage of the reference meter and the error-corrected second voltage. This invention is applicable to power distribution line impedance measurement scenarios.

Description

Technical Field

[0001] This invention relates to the field of low-voltage power distribution network technology, and in particular to a method and system for measuring the impedance of power distribution lines. Background Technology

[0002] Line impedance parameters of low-voltage distribution networks are fundamental data for line loss management and operational status assessment in distribution areas. Existing impedance measurement methods mainly fall into two categories. One type is based on high-precision synchronous measurement equipment, such as using two power quality analyzers with GPS installed at the beginning and end of the line respectively. The voltage and current vectors at both ends are measured synchronously via GPS to estimate the line impedance. However, the accuracy of this method is highly dependent on the availability and accuracy of the GPS signal. Furthermore, this method requires specialized measurement equipment, resulting in high hardware costs and complex deployment.

[0003] Another type is based on smart meter measurement data. Specifically, it utilizes the voltage amplitude and power data provided by the smart meters to estimate line impedance through regression analysis or data-driven methods. For example, a reference meter is selected within the same distribution area (usually a meter at the beginning of the line close to the transformer with negligible line impedance). Assuming the reference meter and the meter under test share the same ideal zero-potential reference point, the line impedance is calculated by comparing the voltage amplitude differences between the two and combining this with the current value of the meter under test. This method requires no additional hardware investment and can be implemented using only the conventional measurement data from existing smart meters. However, the measurable node data in low-voltage distribution networks is limited and has low accuracy, making it difficult to accurately estimate line impedance. Furthermore, in practical applications, three-phase imbalance is common in low-voltage distribution networks, which can easily lead to significant errors in the impedance estimation results. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide a method and system for measuring the impedance of power distribution lines, which can effectively reduce impedance estimation errors and improve impedance measurement accuracy.

[0005] In a first aspect, embodiments of the present invention provide a method for measuring the impedance of a power distribution line. The method includes: determining a reference meter for a power meter of a line under test; obtaining a first voltage of the reference meter and a second voltage of the power meter of the line under test; performing error correction processing on the second voltage to obtain an error-corrected second voltage, wherein the error correction processing includes at least one of phase deviation correction processing and neutral line voltage drop compensation processing; and obtaining impedance information of the line under test based on the first voltage of the reference meter and the error-corrected second voltage.

[0006] Optionally, the reference meter for determining the line meter under test includes: determining the reference meter for the line meter under test based on the distribution substation topology.

[0007] Optionally, the distribution area topology includes device nodes and edges, wherein the edges represent the line connection relationships between the device nodes, and each edge corresponds to an impedance estimate of the line represented by the edge; determining the reference meter for the line meter under test based on the distribution area topology includes: calculating the electrical distance between the line meter under test and the candidate reference meter based on the distribution area topology, wherein the electrical distance is equal to the sum of the impedance estimates corresponding to the edges between the device nodes corresponding to the line meter under test and the device nodes corresponding to the candidate reference meter in the distribution area topology; and determining the reference meter from the candidate reference meter based on the electrical distance between the line meter under test and the candidate reference meter.

[0008] Optionally, determining the reference meter from the candidate reference meters based on the electrical distance between the meter under test and the candidate reference meters includes: determining a predetermined number of candidate reference meters with the smallest electrical distance to the meter under test as reference meters; or, determining a predetermined number of candidate reference meters with the smallest electrical distance to the meter under test as initial target reference meters; calculating the average phase difference between the initial target reference meter and the meter under test; and determining the initial target reference meter with an average phase difference less than a preset threshold as a reference meter.

[0009] Optionally, the error correction process includes phase deviation correction processing; the step of performing error correction processing on the second voltage to obtain the second voltage after error correction processing includes: obtaining the phase difference between the first voltage and the second voltage; calculating the projection amplitude of the second voltage in the direction of the first voltage based on the phase difference between the first voltage and the second voltage, and using the projection amplitude as the amplitude of the second voltage after phase deviation correction processing.

[0010] Optionally, obtaining the phase difference between the first voltage and the second voltage includes: calculating the phase difference between the first voltage and the second voltage based on the measured phase of the first voltage and the measured phase of the second voltage; calculating the projection amplitude of the second voltage in the first voltage direction based on the phase difference between the first voltage and the second voltage includes: when the phase measurement accuracy reaches a first accuracy, calculating the projection amplitude of the second voltage in the first voltage direction based on the phase difference between the first voltage and the second voltage; or, when the phase measurement accuracy reaches a second accuracy, calculating the projection amplitude of the second voltage in the first voltage direction based on the phase difference between the first voltage and the second voltage when the phase difference is greater than a predetermined threshold.

[0011] Optionally, obtaining the phase difference between the first voltage and the second voltage includes estimating the phase difference between the first voltage and the second voltage by cross-correlation of the voltage sequences.

[0012] Optionally, the error correction process includes neutral line voltage drop compensation processing; the step of performing error correction processing on the second voltage to obtain the error-corrected second voltage includes: obtaining the neutral line current and the neutral line equivalent impedance; calculating the neutral line voltage drop based on the neutral line current and the neutral line equivalent impedance; and performing neutral line voltage drop compensation on the second voltage based on the neutral line voltage drop to obtain the second voltage after the neutral line voltage drop compensation processing, wherein the second voltage after the neutral line voltage drop compensation processing is equal to the difference between the second voltage and the neutral line voltage drop.

[0013] Optionally, the error correction processing includes phase deviation correction processing and neutral line voltage drop compensation processing; the step of performing error correction processing on the second voltage to obtain the error-corrected second voltage includes: performing phase deviation correction processing on the second voltage, performing neutral line voltage drop compensation processing on the second voltage after phase deviation correction processing, and using the second voltage after phase deviation correction processing and neutral line voltage drop compensation processing as the error-corrected second voltage; or, performing neutral line voltage drop compensation processing on the second voltage, performing phase deviation correction processing on the second voltage after neutral line voltage drop compensation processing, and using the second voltage after neutral line voltage drop compensation processing and phase deviation correction processing as the error-corrected second voltage.

[0014] Optionally, the reference meters include at least two; obtaining the impedance information of the circuit under test based on the first voltage of the reference meters and the second voltage after error correction includes: calculating the impedance information of the circuit under test corresponding to the reference meters using the reference meter voltage difference method based on the first voltage of the reference meters and the second voltage after error correction; and performing a weighted average processing on the impedance information of the circuit under test corresponding to the reference meters based on the weight information corresponding to the reference meters to obtain the impedance information of the circuit under test.

[0015] Secondly, embodiments of the present invention also provide a power distribution line impedance measurement system, the system comprising: a first determining module for determining a reference meter for a power meter of a line under test; a first acquiring module for acquiring a first voltage of the reference meter and a second voltage of the power meter of the line under test; an error correction module for performing error correction processing on the second voltage to obtain an error-corrected second voltage, wherein the error correction processing includes at least one of phase deviation correction processing and neutral line voltage drop compensation processing; and an impedance acquisition module for acquiring impedance information of the line under test based on the first voltage of the reference meter and the error-corrected second voltage.

[0016] Optionally, the first determining module includes a first determining submodule, used to determine the reference meter of the line meter under test based on the distribution area topology.

[0017] Optionally, the distribution area topology includes device nodes and edges, wherein the edges represent the line connection relationships between the device nodes, and each edge corresponds to an impedance estimate of the line represented by the edge;

[0018] The first determining submodule is specifically used to calculate the electrical distance between the line meter under test and the candidate reference meter based on the distribution transformer area topology. The electrical distance is equal to the sum of the impedance estimates of the edges between the device nodes corresponding to the line meter under test and the device nodes corresponding to the candidate reference meters in the distribution transformer area topology.

[0019] The reference meter is determined from the candidate reference meters based on the electrical distance between the meter under test and the candidate reference meter.

[0020] Optionally, the first determining submodule is specifically used to determine a predetermined number of candidate reference meters that have the smallest electrical distance from the meter under test as reference meters;

[0021] or,

[0022] A predetermined number of candidate reference meters with the smallest electrical distance from the meter under test are determined as the initial target reference meters.

[0023] Calculate the average phase difference between the initial target reference meter and the meter of the circuit under test;

[0024] The initial target reference meter whose average phase difference is less than a preset threshold is determined as the reference meter.

[0025] Optionally, the error correction process includes phase deviation correction processing;

[0026] The error correction module includes:

[0027] A phase acquisition submodule is used to acquire the phase difference between the first voltage and the second voltage;

[0028] The calculation submodule is used to calculate the projection amplitude of the second voltage in the direction of the first voltage based on the phase difference between the first voltage and the second voltage, and use the projection amplitude as the second voltage amplitude after the phase deviation correction processing.

[0029] Optionally, the phase acquisition submodule is specifically used to calculate the phase difference between the first voltage and the second voltage based on the measured phase of the first voltage and the measured phase of the second voltage;

[0030] The calculation submodule is specifically used to calculate the projection amplitude of the second voltage in the direction of the first voltage based on the phase difference between the first voltage and the second voltage, when the phase measurement accuracy reaches the first accuracy.

[0031] or,

[0032] When the phase measurement accuracy reaches the second accuracy, and the phase difference is greater than a predetermined threshold, the projection amplitude of the second voltage in the direction of the first voltage is calculated based on the phase difference between the first voltage and the second voltage.

[0033] Optionally, the phase acquisition submodule is specifically used to estimate the phase difference between the first voltage and the second voltage through cross-correlation of voltage sequences.

[0034] Optionally, the error correction process includes neutral line voltage drop compensation processing;

[0035] The error correction module includes:

[0036] The acquisition submodule is used to acquire the neutral current and the neutral equivalent impedance;

[0037] The calculation submodule is used to calculate the neutral line voltage drop based on the neutral line current and the neutral line equivalent impedance;

[0038] The correction submodule is used to perform neutral line voltage drop compensation on the second voltage based on the neutral line voltage drop to obtain the second voltage after the neutral line voltage drop compensation process. The second voltage after the neutral line voltage drop compensation process is equal to the difference between the second voltage and the neutral line voltage drop.

[0039] Optionally, the error correction process includes phase deviation correction and neutral line voltage drop compensation.

[0040] The error correction module is specifically used to perform phase deviation correction processing on the second voltage, perform neutral line voltage drop compensation processing on the second voltage after phase deviation correction processing, and use the second voltage after phase deviation correction processing and neutral line voltage drop compensation processing as the second voltage after error correction processing.

[0041] or,

[0042] The second voltage is subjected to neutral line voltage drop compensation processing, and the second voltage after neutral line voltage drop compensation processing is subjected to phase deviation correction processing. The second voltage after neutral line voltage drop compensation processing and phase deviation correction processing is used as the second voltage after error correction processing.

[0043] Optionally, the reference meters may include at least two;

[0044] The impedance acquisition module is specifically used to calculate the impedance information of the circuit under test corresponding to the reference meter based on the first voltage of the reference meter and the second voltage after error correction, using the reference meter voltage difference method.

[0045] Based on the weight information corresponding to the reference meter, the impedance information of the circuit under test corresponding to the reference meter is weighted and averaged to obtain the impedance information of the circuit under test.

[0046] The power distribution line impedance measurement method and system provided in this invention determines a reference meter for the line under test, obtains a first voltage from the reference meter and a second voltage from the meter on the line under test, and performs phase deviation correction and / or neutral line voltage drop compensation on the second voltage to obtain an error-corrected second voltage. Based on the first voltage from the reference meter and the error-corrected second voltage, the impedance information of the line under test is obtained. Thus, by correcting the voltage of the meter on the line under test before impedance calculation, phase deviation and / or neutral line potential offset are eliminated, reducing impedance estimation errors and improving impedance measurement accuracy. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic flowchart of a power distribution line impedance measurement method according to an embodiment of the present invention;

[0049] Figure 2This is an exemplary schematic diagram of a distribution radio station topology according to an embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of the power distribution line impedance measurement system architecture provided in an embodiment of the present invention. Detailed Implementation

[0051] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0052] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0053] See Figure 1 This application provides a method for measuring the impedance of a power distribution line, including the following steps:

[0054] S110. Determine the reference meter for the circuit meter under test.

[0055] The impedance measurement method provided in this embodiment of the invention uses the reference meter differential pressure method. Therefore, in this step, it is first necessary to determine the reference meter of the circuit meter under test.

[0056] The embodiments of the present invention do not limit how to determine or select the reference meter. A meter with a clear electrical location can be selected as the reference meter within the same transformer area, such as the first-end meter that is close to the transformer and whose line impedance is negligible.

[0057] In one embodiment of the present invention, a dynamic optimization mechanism can be used to determine the reference meter in this step. During impedance measurement, the dynamic optimization mechanism enables intelligent selection and fault tolerance of the reference meter, laying the foundation for subsequent calculations and avoiding the limitations of traditional manual selection of fixed reference meters, thereby further improving the accuracy of impedance measurement. Specifically, as an example of dynamic optimization, the reference meter for determining the meter of the circuit under test includes:

[0058] The reference meter for the circuit meter under test is determined based on the distribution area topology.

[0059] For example, Figure 2 This is a schematic diagram of the topology of a distribution radio station. (See attached diagram) Figure 2As shown, the distribution transformer area topology includes equipment nodes and edges. Equipment nodes represent power supply equipment within the distribution transformer area, including distribution transformers, branch switches, meters, and electricity meters, etc. Edges represent the line connection relationships between equipment nodes, and each edge corresponds to the impedance estimate of the line it represents. For example, the impedance estimate of the line between the distribution transformer and branch switch B is Z_(L2), and the impedance estimate of the line between electricity meter M14 and metering box 5 is Z_(M14).

[0060] The reference meter for determining the meter of the line under test based on the distribution area topology may specifically include:

[0061] Based on the distribution area topology, the electrical distance between the line meter under test and the candidate reference meter is calculated. The electrical distance is equal to the sum of the impedance estimates of the edges between the device nodes corresponding to the line meter under test and the device nodes corresponding to the candidate reference meters in the distribution area topology. Based on the electrical distance between the line meter under test and the candidate reference meter, the reference meter is determined from the candidate reference meters.

[0062] See Figure 2In this embodiment, the topology data of the distribution substation can be obtained in advance. Specifically, it can include the first-end power supply equipment, the first-level branch equipment (branch node), the second-level home access equipment (user home access node), and the end acquisition equipment and their connection relationship, as well as the impedance estimation data of the lines between the equipment nodes. Specifically, the first-end power supply equipment (first level) can be a transformer, the first-level branch equipment (second level) is a branch switch, the second-level home access equipment (third level) is a metering box, and the end acquisition equipment (fourth level) is an electricity meter. In this embodiment of the invention, the method for obtaining the impedance estimate of the line is not limited. For example, it can be estimated based on parameters such as the material, cross-sectional area, length, and number of joints of the line. Impedance estimation can also be based on historical operating data, such as direct calculation based on voltage difference and current: obtaining voltage phasor data and current data of the nodes at both ends of the line at multiple time sections; calculating the line impedance value at each time section based on Ohm's law; statistically processing the line impedance values ​​at multiple time sections (such as taking the average or median) to obtain the impedance estimate Z_i; or, based on regression analysis using the least squares method: addressing the problem of limited measurement data, establishing a linear regression model and using the least squares method to solve for the impedance value to finally obtain the impedance estimate. Impedance estimation can also be based on the characteristic signal injection method, including: injecting a voltage or current signal with known characteristics into one end of the line; acquiring a response signal at the other end or the same end of the line; and calculating the line impedance value based on the injected signal and the response signal. Among them, the historical operation data method is suitable for transformer substations equipped with measuring equipment such as smart meters, and is low-cost and can be deployed in batches; the feature signal injection method is suitable for scenarios that require precise measurement of specific lines or where historical data is insufficient, and is highly accurate and has strong anti-interference capabilities. In practical applications, the two methods can be flexibly selected or combined according to the equipment configuration and accuracy requirements of the transformer substation.

[0063] Then, based on these data, a topology graph G(V,E) representing the topology of the transformer area is constructed. The topology graph includes a set of device nodes V and a set of edges E. The device nodes include at least the first-end power supply device node, the first-level branch device node, the second-level household access device node, and the last-end acquisition device node. The edges in the edge set are used to represent the line connection relationship between the device nodes. Each edge corresponds to the impedance estimate of the line represented by that edge.

[0064] Subsequently, when impedance measurement is required, the electrical distance between the meter under test and all candidate reference meters within the distribution area can be calculated based on the pre-constructed distribution area topology diagram. The electrical distance is equal to the sum of the estimated impedance values ​​D(M,R) of the edges between the device nodes corresponding to the meter under test and the device nodes corresponding to the candidate reference meters in the distribution area topology.

[0065] In the formula, D(M,R) represents the electrical distance between the meter under test M and the candidate reference meter R, and Z_i is the estimated line impedance of the i-th segment of the topological path between M and R. The smaller the electrical distance, the closer the two meters are electrically, the more similar their voltage levels are, and the better the applicability as a reference meter.

[0066] It is understandable that the reference meter determined in this step can be one or more. When there are multiple reference meters, the impedance value of the circuit under test can be obtained for each reference meter using the reference meter differential voltage method. Then, the impedance values ​​obtained from multiple reference meters can be weighted and averaged to further improve the accuracy of the measurement results.

[0067] In some embodiments, determining the reference meter from the candidate reference meter based on the electrical distance between the line meter under test and the candidate reference meter includes:

[0068] A predetermined number of candidate reference meters with the smallest electrical distance from the meter under test are selected as reference meters;

[0069] or,

[0070] A predetermined number of candidate reference meters with the smallest electrical distance from the meter under test are determined as the initial target reference meters.

[0071] Calculate the average phase difference between the initial target reference meter and the meter of the circuit under test;

[0072] The initial target reference meter whose average phase difference is less than a preset threshold is determined as the reference meter.

[0073] In this embodiment, when selecting reference meters, one approach is to sort them by electrical distance from smallest to largest, and determine a predetermined number of candidate reference meters with the smallest electrical distance to the meter on the line under test as reference meters; for example, select the k closest meters as reference meters, where k is recommended to be 3 to 5; prioritize meters that belong to the same metering box as the meter under test and meters that belong to the same branch line, and exclude meters with recent data quality problems and meters with too small load current.

[0074] Another approach to selecting reference meters is to sort them by electrical distance from smallest to largest. A predetermined number of candidate reference meters with the smallest electrical distance to the meter under test are selected as initial target reference meters. The average phase difference between the initial target reference meters and the meter under test is calculated, and the initial target reference meters with an average phase difference less than a preset threshold are designated as reference meters. For example, the m closest meters can be selected as reference meters, where m is recommended to be 3 to 5. Meters belonging to the same metering box and the same branch line as the meter under test are given priority, while meters with recent data quality issues and those with excessively low load current are excluded. For each reference meter R in the initial target reference meters, its average phase difference with the meter under test M within a preset time period (e.g., the last 7 days) is calculated. In the formula, This represents the average phase difference between the initial target reference meter R and the meter under test M within a preset time period. Indicates the phase of the meter under test. Indicates the phase of the reference meter.

[0075] If the average phase difference exceeds a preset threshold (e.g., 10°), the reference meter is removed from the initial target reference meter, and the initial target reference meter with an average phase difference less than the preset threshold is determined as the reference meter.

[0076] In some embodiments, when there are multiple reference meters, dynamic weights can be assigned and normalized for each reference meter based on the electrical distance between the reference meter and the meter on the line under test. Where D_i is the electrical distance, Q_i is the data quality factor, C_i is the phase consistency factor, and Σ = 1. Generally, the closer the electrical distance, the greater the weight. By assigning weights to the reference tables based on electrical distance, the impedance measurements corresponding to each reference table can be weighted and averaged based on their respective weights. This further highlights the data contribution of key nodes, weakens the influence of interference data, and further improves the accuracy of the measured impedance data.

[0077] This topology-driven dynamic reference table optimization mechanism effectively overcomes the limitations of traditional methods that rely on fixed reference tables. When the topology of the transformer area changes or the original reference table shows data anomalies, the system can automatically re-optimize the reference table and adjust the weight allocation, avoiding the collapse of all calculation results due to the failure of a single reference table.

[0078] S120. Obtain the first voltage of the reference meter and the second voltage of the circuit meter under test.

[0079] In this embodiment, the first voltage of the reference meter and the second voltage of the meter of the line under test are obtained respectively, that is, the voltages measured by the reference meter and the meter of the line under test are obtained respectively.

[0080] It is understood that voltage typically includes voltage amplitude and phase angle. Unless otherwise specified, the first voltage mentioned in the steps of the embodiments of the present invention refers to the first voltage value, i.e., the first voltage amplitude |U_ref(t)|, and the second voltage obtained refers to the second voltage value, i.e., the second voltage amplitude |U_meas(t)|.

[0081] It is also understandable that, based on the measurement function of the meter, some meters can only measure the voltage amplitude, while others can measure both the voltage amplitude and the phase angle simultaneously. Therefore, in this step, in addition to obtaining the voltage amplitude |U_ref(t)| of the first voltage of the reference meter, we can also obtain the phase angle θ_ref(t) of the first voltage. In addition to obtaining the voltage amplitude |U_meas(t)| of the second voltage of the meter of the circuit under test, we can also obtain the phase angle θ_meas(t) of the second voltage.

[0082] S130. Perform error correction processing on the second voltage to obtain the second voltage after error correction processing, wherein the error correction processing includes at least one of phase deviation correction processing and neutral line voltage drop compensation processing.

[0083] Because voltage phase deviations or voltage drops caused by neutral current may disrupt the equipotential assumption when measuring the impedance of power distribution lines, leading to significant errors in impedance calculations, this embodiment reduces calculation errors by performing error correction processing on the second voltage (i.e., the second voltage amplitude) of the meter in the circuit under test. This error correction processing includes at least one of phase deviation correction and neutral voltage drop compensation. In practical applications, different error correction methods can be selected based on the dominant factors of the error source.

[0084] For example, when the three-phase balance of the transformer area is good (e.g., unbalance <10%) and the neutral current is very small (e.g., <3A), only phase deviation correction is used.

[0085] Specifically, in one embodiment, the error correction process includes a phase deviation correction process. Therefore, S130, performing error correction processing on the second voltage to obtain the error-corrected second voltage includes:

[0086] First, the phase difference between the first voltage and the second voltage is obtained.

[0087] The phase of the first voltage and the second voltage can be obtained in advance by measurement. In this step, when obtaining the phase difference between the first voltage and the second voltage, the phase difference between the first voltage and the second voltage is calculated based on the measured phase of the first voltage and the measured phase of the second voltage.

[0088] Specifically, for example, the phase angles (i.e., phases) of the first voltage and the second voltage can be measured using a reference meter and a meter for the circuit under test, respectively. Based on the obtained phase angles θ_ref(t) of the first voltage from the reference meter and θ_meas(t) of the second voltage from the meter for the circuit under test, the instantaneous phase difference between the two voltage values ​​can be calculated. Where θ_ref(t) is the first voltage phase angle of the reference meter. This is the second voltage phase angle of the meter in the circuit under test.

[0089] Then, based on the phase difference between the first voltage and the second voltage, the projection amplitude of the second voltage in the direction of the first voltage is calculated, and the projection amplitude is used as the second voltage after the phase deviation correction process, i.e., the second voltage amplitude.

[0090] In this step, based on the principle of vector projection, the second voltage of the circuit meter under test is projected onto the phase direction of the first voltage of the reference meter to obtain the equivalent second voltage amplitude after phase correction.

[0091] Specifically, taking the first voltage phase angle θ_ref(t) of the reference meter as the benchmark, the projection amplitude of the meter in the line under test in the direction of the reference meter is:

[0092] U_meas_corrected(t)=|U_meas(t)|Xcos( In the formula, U_meas_corrected(t) is the second voltage amplitude after phase deviation correction. This represents the phase difference between the first and second voltages. The projected amplitude reflects the true effective component of the voltage of the meter under test under the phase reference of the reference table.

[0093] By correcting the phase deviation of the second voltage, the amplitude calculation error caused by the phase deviation can be effectively eliminated, thus improving the accuracy of impedance measurement.

[0094] In one embodiment of the present invention, a three-level gradient phase deviation correction processing method can be provided during phase deviation correction processing to adapt to different phase measurement hardware conditions. Wherein:

[0095] First tier: Possesses high-precision phase measurement conditions, with phase measurement accuracy reaching the first level of precision.

[0096] In this case, the phase difference between the first voltage and the second voltage can be calculated directly, and the projection amplitude of the second voltage in the direction of the first voltage can be calculated based on the phase difference between the first voltage and the second voltage.

[0097] Specifically, when performing phase deviation correction processing, it can be measured whether the phase measurement device has high-precision phase phasor measurement capability. In some embodiments, when it has a phase measurement accuracy of 1°, for example, by using a PMU (Phasor Measurement Unit) or an IoT meter for high-frequency sampling, it can be determined that it has high-precision phase measurement capability. Then, the measured first voltage phase angle and the second voltage phase angle can be directly used to calculate the projection amplitude of the second voltage in the first voltage direction according to the above projection amplitude calculation formula.

[0098] It is understandable that the phase angle can be directly measured by the reference meter and the meter of the line under test. For example, the phase angle measured by the reference meter and the meter of the line under test can be directly read in step S120, or it can be measured by other dedicated phase measurement equipment.

[0099] Second gradient: Possessing finite-precision phase measurement conditions, the phase measurement accuracy reaches the second precision.

[0100] Understandably, the second precision is lower than the first precision.

[0101] In this case, the phase difference between the first voltage and the second voltage can be calculated first, and then it can be determined whether the phase difference is greater than a predetermined threshold. When the phase difference is greater than the predetermined threshold, the projection amplitude of the second voltage in the direction of the first voltage can be calculated based on the phase difference between the first voltage and the second voltage.

[0102] Specifically, during phase deviation correction, it can be assessed whether the phase measuring device has limited phase measurement capability. In some embodiments, if the phase measurement accuracy is 5° or approximately 5°, and the phase measurement capability is determined to be limited, the phase difference between the first voltage and the second voltage is first calculated. If the phase difference is greater than a preset value, for example, a phase difference ≥ 2°, the projection amplitude of the second voltage in the first voltage direction is calculated based on the phase difference between the two voltages according to the aforementioned projection amplitude calculation formula. If the phase difference is not greater than the preset value, phase deviation correction can be skipped.

[0103] Third gradient: lacks phase measurement capability

[0104] Since the phase measurement capability is not available, the phase difference between the first voltage and the second voltage can be obtained through other means. Specifically, the phase difference between the first voltage and the second voltage can be estimated by cross-correlation of the voltage sequences. Based on the estimated phase difference, the projection amplitude of the second voltage in the first voltage direction can be calculated using the above projection amplitude calculation formula.

[0105] In this embodiment, by setting up a three-level gradient phase measurement, this application can adapt to different hardware conditions, from high-precision IoT meters to old electricity meters. Even in scenarios where phase measurement capabilities are limited or even absent, usable computational performance can still be maintained through voltage sequence cross-correlation analysis, significantly improving the adaptability to complex on-site environments.

[0106] It is understood that the values ​​of 1° and 5° mentioned above are merely illustrative examples, and the specific values ​​can be set according to the actual application scenario and accuracy requirements. For example, in other embodiments, the accuracy of the first gradient phase measurement can be set to 0.5° or 2°, and the accuracy of the second gradient phase measurement can be set to 3° or 10°, all of which do not depart from the protection scope of this application.

[0107] For example, in some embodiments, when the voltage phase between the reference meter and the meter under test is basically consistent (e.g., phase difference < 2°) and the transformer area topology is symmetrical, in S130, only neutral line voltage drop compensation can be used.

[0108] Specifically, in one embodiment, the error correction process includes a phase deviation correction process. Therefore, in S130, performing error correction processing on the second voltage to obtain the error-corrected second voltage includes:

[0109] First, obtain the neutral current and the neutral equivalent impedance.

[0110] In this step, in this embodiment, when obtaining the neutral current, the neutral current can be calculated by the vector sum of the three-phase currents according to Kirchhoff's Current Law. The specific formula is as follows:

[0111] I_N(t) = I_A(t) + I_B(t) + I_C(t); where I_A(t), I_B(t), and I_C(t) are the current vectors of phases A, B, and C, respectively, and I_N(t) is the neutral line current.

[0112] When obtaining the equivalent impedance of the neutral line, an appropriate method can be selected based on the actual operating conditions. Methods for obtaining the equivalent impedance of the neutral line include:

[0113] System identification method: During periods when the load in the transformer area is relatively stable, the neutral line current and zero-sequence voltage measurements under different load conditions are used to identify the neutral line equivalent impedance Z_N using the least squares method.

[0114] Typical value method: Estimate the equivalent impedance Z_N of the neutral line based on the line parameters; specifically, the estimation formula is:

[0115] Z_N ≈ r_0 × L; where L represents the line length and r_0 represents the resistance per unit length.

[0116] Adaptive estimation method: The equivalent impedance Z_N of the neutral line is continuously updated using the recursive least squares method.

[0117] Next, the neutral line voltage drop is calculated based on the neutral line current and the neutral line equivalent impedance.

[0118] In this step, for simplified engineering applications, only the resistive component can be considered. The neutral line voltage drop U_N(t) is calculated by multiplying the neutral line current amplitude by the equivalent neutral line resistance R_N; the specific formula is as follows:

[0119] U_N(t)≈|I_N(t)|×R_N; where I_N(t) is the neutral current, R_N is the equivalent resistance of the neutral line, and U_N(t) is the neutral voltage drop.

[0120] Then, based on the neutral line voltage drop, the second voltage is compensated for to obtain the second voltage after the neutral line voltage drop compensation process. The second voltage after the neutral line voltage drop compensation process is equal to the difference between the second voltage and the neutral line voltage drop.

[0121] In this step, neutral line voltage drop compensation is performed on the second voltage of the meter in the line under test to obtain the processed second voltage after eliminating the influence of neutral line voltage drop. The specific formula is as follows:

[0122] U_meas_corrected1(t) = U_meas(t) - U_N(t); where U_meas(t) is the second voltage obtained from the meter of the circuit under test, U_N(t) is the neutral line voltage drop, and U_meas_corrected1(t) is the second voltage after neutral line voltage drop compensation.

[0123] In many practical power distribution scenarios, impedance measurement often involves both voltage phase deviation and neutral voltage drop, which can disrupt the equipotential assumption. To address this, error correction processing can simultaneously perform phase deviation correction and neutral voltage drop compensation. In one embodiment of the invention, the error correction process includes phase deviation correction and neutral voltage drop compensation. Therefore, step S130 performs error correction processing on the second voltage to obtain the error-corrected second voltage, which includes:

[0124] The second voltage is subjected to phase deviation correction processing, and the second voltage after phase deviation correction processing is subjected to neutral line voltage drop compensation processing. The second voltage after phase deviation correction processing and neutral line voltage drop compensation processing is used as the second voltage after error correction processing.

[0125] or,

[0126] The second voltage is subjected to neutral line voltage drop compensation processing, and the second voltage after neutral line voltage drop compensation processing is subjected to phase deviation correction processing. The second voltage after neutral line voltage drop compensation processing and phase deviation correction processing is used as the second voltage after error correction processing.

[0127] Understandably, when performing error correction on the second voltage, the order of the two error correction methods can be adjusted according to the actual operating conditions. The output of the first correction method is used as the input of the other correction method. In a typical three-phase unbalanced distribution area, it is preferable to perform phase deviation correction first and then neutral line voltage drop compensation.

[0128] Specifically, let's take the sequence of first performing phase deviation correction and then neutral line voltage drop compensation as an example:

[0129] Based on the obtained phase angle θ_ref(t) of the first voltage and the phase angle θ_meas(t) of the second voltage, calculate the instantaneous phase difference between the two voltages: .

[0130] According to the principle of vector projection, the second voltage is projected onto the phase direction of the first voltage to obtain the equivalent second voltage amplitude after phase correction. Specifically, taking the phase angle θ_ref(t) of the first voltage as a reference, the projection amplitude of the second voltage in the direction of the reference meter is:

[0131] U_meas_corrected(t)=|U_meas(t)|×cos( ); where U_meas_corrected(t) is the second voltage amplitude after phase deviation correction.

[0132] The neutral line voltage drop is compensated for the second voltage amplitude after phase deviation correction to obtain the second voltage after eliminating the influence of the neutral line voltage drop. The specific formula is as follows:

[0133] U_meas_final(t) = U_meas_corrected(t) - U_N(t); where U_meas(t) is the second voltage obtained from the circuit under test, U_N(t) is the neutral voltage drop, and U_meas_final(t) is the second voltage after neutral voltage drop compensation. The neutral voltage drop can be obtained in the following way:

[0134] According to Kirchhoff's Current Law, the neutral current can be calculated by the vector sum of the three-phase currents, using the following formula:

[0135] I_N(t) = I_A(t) + I_B(t) + I_C(t); where I_A(t), I_B(t), and I_C(t) are the current vectors of phases A, B, and C, respectively, and I_N(t) is the neutral line current.

[0136] Obtain the equivalent impedance of the neutral line:

[0137] During periods when the load in the transformer area is relatively stable, the neutral line equivalent impedance Z_N is identified by using the measured values ​​of neutral line current and zero-sequence voltage under different load conditions and the least squares method.

[0138] Based on the neutral current and the equivalent impedance of the neutral line, the neutral voltage drop is calculated using the following formula:

[0139] U_N(t)≈|I_N(t)|×R_N; where I_N(t) is the neutral current, R_N is the equivalent resistance of the neutral line, and U_N(t) is the neutral voltage drop.

[0140] In this embodiment, by simultaneously employing phase deviation correction and neutral line voltage drop compensation for dual error suppression, the impedance calculation deviation under three-phase unbalanced scenarios can be significantly reduced, and the calculation accuracy can be greatly improved.

[0141] Furthermore, phase deviation correction and neutral voltage drop compensation form a synergistic mechanism of mutual feedback coupling and iterative optimization. The high-precision phase reference output by phase correction makes the calculation of neutral compensation more accurate, avoiding compensation errors caused by phase deviation. The accurate voltage amplitude after compensation can be fed back to the phase correction stage to correct the projection reference of the next measurement, forming a positive cycle.

[0142] S140. Based on the first voltage of the reference meter and the second voltage after error correction, obtain the impedance information of the circuit under test.

[0143] In this step, based on the first voltage from the reference meter and the second voltage after error correction, the impedance information Z of the circuit under test is calculated using the traditional reference meter voltage difference method. The specific formula is as follows:

[0144] Z = (U_ref - U_meas_final) / I_meas; where U_ref is the first voltage of the reference meter, U_meas_final is the second voltage after error correction, and I_meas is the second current of the circuit under test.

[0145] In some embodiments, the reference meter includes at least two;

[0146] The process of obtaining the impedance information of the circuit under test based on the first voltage from the reference meter and the second voltage after error correction includes:

[0147] Based on the first voltage of the reference meter and the second voltage after error correction, the impedance information of the circuit under test corresponding to the reference meter is calculated using the reference meter voltage difference method.

[0148] Based on the weight information corresponding to the reference meter, the impedance information of the circuit under test corresponding to the reference meter is weighted and averaged to obtain the impedance information of the circuit under test.

[0149] In this embodiment, when multiple reference tables are selected, for each reference table, after calculating the impedance of the circuit under test corresponding to each reference table according to the aforementioned steps S120 to S130, the impedance information corresponding to all reference tables is weighted and averaged to obtain the final impedance information of the circuit under test. Specifically, the final impedance information Z_final of the circuit under test is:

[0150] Where Z_final represents the final impedance information of the circuit under test. The dynamic weights of each reference meter, This provides the impedance information for the circuit under test corresponding to each reference meter.

[0151] In summary, the power distribution line impedance measurement method provided in this application employs multiple error suppression and dynamic optimization mechanisms during impedance measurement, ensuring the comprehensiveness and reliability of the measurement. Firstly, a dynamic optimization mechanism for reference meters driven by the distribution substation topology, based on four-level topological electrical distance, phase consistency verification, and dynamic weight allocation, enables intelligent selection and fault tolerance of reference meters, laying the foundation for subsequent calculations. Secondly, systematic errors caused by voltage phase deviation are eliminated through vector projection phase correction, and the neutral line voltage drop compensation restores the equipotential assumption, resolving the neutral line potential offset problem. Compared with the traditional scalar voltage difference method, this invention fundamentally eliminates the two major error sources: phase deviation and neutral line potential offset, making the impedance calculation results closer to the true value.

[0152] Specifically, taking a typical low-voltage distribution substation (transformer capacity 400kVA, connected to 156 users, three-phase imbalance approximately 25%) as an example, the impedance calculation was performed using the distribution line impedance measurement method provided in this application. Verification was conducted using 15 meters under test. Through 45 sets of data (15 meters × 3 time periods), the traditional method (without error processing, directly using the differential pressure method) had an average error of 20.12% and a maximum single-point error of 25.07%. With phase correction alone, the average error decreased to 12.60% (a reduction of 37.4%), and with neutral line compensation alone, the average error decreased to 11.46% (a reduction of 43.0%). After double correction, the error decreased to 0.42%, a reduction of 97.9%, significantly improving accuracy. Some data are shown in Table 1 below.

[0153] See Figure 3 This embodiment also provides a power distribution line impedance measurement system, the system comprising:

[0154] The first determining module 31 is used to determine the reference meter for the circuit meter under test;

[0155] The first acquisition module 32 is used to acquire the first voltage of the reference meter and the second voltage of the circuit meter under test.

[0156] Error correction module 33 is used to perform error correction processing on the second voltage to obtain the second voltage after error correction processing, wherein the error correction processing includes at least one of phase deviation correction processing and neutral line voltage drop compensation processing;

[0157] The impedance acquisition module 34 is used to acquire the impedance information of the circuit under test based on the first voltage of the reference meter and the second voltage after error correction.

[0158] The power distribution line impedance measurement system provided in this embodiment determines a reference meter for the circuit under test; obtains a first voltage from the reference meter and a second voltage from the circuit under test; and performs phase deviation correction and / or neutral line voltage drop compensation on the second voltage to obtain an error-corrected second voltage. Based on the first voltage from the reference meter and the error-corrected second voltage, the impedance information of the circuit under test is obtained. Thus, by correcting the voltage of the circuit under test meter before impedance calculation, phase deviation and / or neutral line potential offset are eliminated, improving the accuracy of impedance calculation.

[0159] In some embodiments, the first determining module includes a first determining submodule, used to determine a reference meter for the line meter under test based on the distribution area topology.

[0160] In some embodiments, the distribution area topology includes device nodes and edges, wherein the edges represent the line connection relationships between the device nodes, and each edge corresponds to an impedance estimate of the line represented by the edge.

[0161] The first determining submodule is specifically used to calculate the electrical distance between the line meter under test and the candidate reference meter based on the distribution transformer area topology. The electrical distance is equal to the sum of the impedance estimates of the edges between the device nodes corresponding to the line meter under test and the device nodes corresponding to the candidate reference meters in the distribution transformer area topology.

[0162] The reference meter is determined from the candidate reference meters based on the electrical distance between the meter under test and the candidate reference meter.

[0163] In some embodiments, the first determining submodule is specifically used to determine a predetermined number of candidate reference meters that have the smallest electrical distance from the line meter under test as reference meters.

[0164] or,

[0165] A predetermined number of candidate reference meters with the smallest electrical distance from the meter under test are determined as the initial target reference meters.

[0166] Calculate the average phase difference between the initial target reference meter and the meter of the circuit under test;

[0167] The initial target reference meter whose average phase difference is less than a preset threshold is determined as the reference meter.

[0168] In some embodiments, the error correction process includes a phase deviation correction process;

[0169] The error correction module includes:

[0170] A phase acquisition submodule is used to acquire the phase difference between the first voltage and the second voltage;

[0171] The calculation submodule is used to calculate the projection amplitude of the second voltage in the direction of the first voltage based on the phase difference between the first voltage and the second voltage, and use the projection amplitude as the second voltage amplitude after the phase deviation correction processing.

[0172] In some embodiments, the phase acquisition submodule is specifically used to calculate the phase difference between the first voltage and the second voltage based on the phase of the measured first voltage and the phase of the measured second voltage;

[0173] The calculation submodule is specifically used to calculate the projection amplitude of the second voltage in the direction of the first voltage based on the phase difference between the first voltage and the second voltage, when the phase measurement accuracy reaches the first accuracy.

[0174] or,

[0175] When the phase measurement accuracy reaches the second accuracy, and the phase difference is greater than a predetermined threshold, the projection amplitude of the second voltage in the direction of the first voltage is calculated based on the phase difference between the first voltage and the second voltage.

[0176] In some embodiments, the phase acquisition submodule is further configured to estimate the phase difference between the first voltage and the second voltage by cross-correlation of voltage sequences.

[0177] In some embodiments, the error correction process includes neutral line voltage drop compensation processing;

[0178] The error correction module further includes:

[0179] The acquisition submodule is used to acquire the neutral current and the neutral equivalent impedance;

[0180] The calculation submodule is used to calculate the neutral line voltage drop based on the neutral line current and the neutral line equivalent impedance;

[0181] The correction submodule is used to perform neutral line voltage drop compensation on the second voltage based on the neutral line voltage drop to obtain the second voltage after the neutral line voltage drop compensation process. The second voltage after the neutral line voltage drop compensation process is equal to the difference between the second voltage and the neutral line voltage drop.

[0182] In some embodiments, the error correction process includes phase deviation correction process and neutral line voltage drop compensation process;

[0183] The error correction module is specifically used to perform phase deviation correction processing on the second voltage, perform neutral line voltage drop compensation processing on the second voltage after phase deviation correction processing, and use the second voltage after phase deviation correction processing and neutral line voltage drop compensation processing as the second voltage after error correction processing.

[0184] or,

[0185] The second voltage is subjected to neutral line voltage drop compensation processing, and the second voltage after neutral line voltage drop compensation processing is subjected to phase deviation correction processing. The second voltage after neutral line voltage drop compensation processing and phase deviation correction processing is used as the second voltage after error correction processing.

[0186] In some embodiments, the reference meter includes at least two;

[0187] The impedance acquisition module is specifically used to calculate the impedance information of the circuit under test corresponding to the reference meter based on the first voltage of the reference meter and the second voltage after error correction, using the reference meter voltage difference method.

[0188] Based on the weight information corresponding to the reference meter, the impedance information of the circuit under test corresponding to the reference meter is weighted and averaged to obtain the impedance information of the circuit under test.

[0189] The power distribution line impedance measurement system of this embodiment can be used to implement the technical solution of the power distribution line impedance measurement method shown in the foregoing embodiment. Its implementation principle and technical effect are similar. For details not described in detail, please refer to each other. It will not be repeated here.

[0190] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0191] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0192] For ease of description, if systems, servers, etc. are involved, they may be described separately as various units / modules based on their functions. Of course, in implementing this invention, the functions of each unit / module can be implemented in one or more software and / or hardware.

[0193] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for measuring the impedance of a power distribution line, characterized in that, The method includes: Determine the reference meter for the circuit under test; Obtain the first voltage of the reference meter and the second voltage of the meter on the circuit under test; The second voltage is subjected to error correction processing to obtain the second voltage after error correction processing, wherein the error correction processing includes at least one of phase deviation correction processing and neutral line voltage drop compensation processing; The impedance information of the circuit under test is obtained based on the first voltage of the reference meter and the second voltage after error correction.

2. The method for measuring the impedance of a power distribution line according to claim 1, characterized in that, The reference meters for determining the electricity meter of the circuit under test include: The reference meter for the circuit meter under test is determined based on the distribution area topology.

3. The method for measuring the impedance of a power distribution line according to claim 2, characterized in that, The distribution area topology includes device nodes and edges, wherein the edges represent the line connection relationships between the device nodes, and each edge corresponds to an impedance estimate of the line represented by the edge. The reference meters for determining the electricity meter of the line under test based on the distribution area topology include: Based on the distribution area topology, the electrical distance between the line meter under test and the candidate reference meter is calculated. The electrical distance is equal to the sum of the impedance estimates of the edges between the device nodes corresponding to the line meter under test and the device nodes corresponding to the candidate reference meters in the distribution area topology. The reference meter is determined from the candidate reference meters based on the electrical distance between the meter under test and the candidate reference meter.

4. The method for measuring the impedance of a power distribution line according to claim 1, characterized in that, The step of determining the reference meter from the candidate reference meter based on the electrical distance between the meter under test and the candidate reference meter includes: A predetermined number of candidate reference meters with the smallest electrical distance from the meter under test are selected as reference meters; or, A predetermined number of candidate reference meters with the smallest electrical distance from the meter under test are determined as the initial target reference meters. Calculate the average phase difference between the initial target reference meter and the meter of the circuit under test; The initial target reference meter whose average phase difference is less than a preset threshold is determined as the reference meter.

5. The method for measuring the impedance of a power distribution line according to claim 1, characterized in that, The error correction process includes phase deviation correction processing; The step of performing error correction processing on the second voltage to obtain the error-corrected second voltage includes: Obtain the phase difference between the first voltage and the second voltage; Based on the phase difference between the first voltage and the second voltage, the projection amplitude of the second voltage in the direction of the first voltage is calculated, and the projection amplitude is used as the second voltage after the phase deviation correction process.

6. The method for measuring the impedance of a power distribution line according to claim 5, characterized in that, The step of obtaining the phase difference between the first voltage and the second voltage includes: Based on the measured phase of the first voltage and the measured phase of the second voltage, calculate the phase difference between the first voltage and the second voltage; The step of calculating the projection amplitude of the second voltage in the direction of the first voltage based on the phase difference between the first voltage and the second voltage includes: When the phase measurement accuracy reaches the first accuracy, the projection amplitude of the second voltage in the direction of the first voltage is calculated based on the phase difference between the first voltage and the second voltage. or, When the phase measurement accuracy reaches the second accuracy, and the phase difference is greater than a predetermined threshold, the projection amplitude of the second voltage in the direction of the first voltage is calculated based on the phase difference between the first voltage and the second voltage.

7. The method for measuring the impedance of a power distribution line according to claim 5, characterized in that, The step of obtaining the phase difference between the first voltage and the second voltage includes: The phase difference between the first voltage and the second voltage is estimated by cross-correlation of the voltage sequences.

8. The method for measuring the impedance of a power distribution line according to claim 1, characterized in that, The error correction process includes neutral line voltage drop compensation processing; The step of performing error correction processing on the second voltage to obtain the error-corrected second voltage includes: Obtain the neutral current and the neutral equivalent impedance; Calculate the neutral line voltage drop based on the neutral line current and the neutral line equivalent impedance; Based on the neutral line voltage drop, the second voltage is compensated for to obtain the second voltage after the neutral line voltage drop compensation process. The second voltage after the neutral line voltage drop compensation process is equal to the difference between the second voltage and the neutral line voltage drop.

9. The method for measuring the impedance of a power distribution line according to claim 1, characterized in that, The error correction process includes phase deviation correction and neutral line voltage drop compensation. The step of performing error correction processing on the second voltage to obtain the error-corrected second voltage includes: The second voltage is subjected to phase deviation correction processing, and the second voltage after phase deviation correction processing is subjected to neutral line voltage drop compensation processing. The second voltage after phase deviation correction processing and neutral line voltage drop compensation processing is used as the second voltage after error correction processing. or, The second voltage is subjected to neutral line voltage drop compensation processing, and the second voltage after neutral line voltage drop compensation processing is subjected to phase deviation correction processing. The second voltage after neutral line voltage drop compensation processing and phase deviation correction processing is used as the second voltage after error correction processing.

10. The method for measuring the impedance of a power distribution line according to claim 1, characterized in that, The reference electricity meter includes at least two; The process of obtaining the impedance information of the circuit under test based on the first voltage from the reference meter and the second voltage after error correction includes: Based on the first voltage of the reference meter and the second voltage after error correction, the impedance information of the circuit under test corresponding to the reference meter is calculated using the reference meter voltage difference method. Based on the weight information corresponding to the reference meter, the impedance information of the circuit under test corresponding to the reference meter is weighted and averaged to obtain the impedance information of the circuit under test.

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