Cable grounding resistance detection method and system based on three-phase decoupling harmonic injection

Abstract

The invention relates to the technical field of cable resistance detection, and particularly discloses a cable grounding resistance detection method and system based on three-phase decoupling harmonic injection, and the method comprises the steps: constructing an equivalent circuit model; performing excitation strategy mapping on the equivalent circuit model to obtain time-sharing excitation configuration parameters, and performing time-sharing harmonic injection on the cable line based on the time-sharing excitation configuration parameters; in the time-sharing harmonic injection process, synchronous coherent detection is carried out on the three-phase voltage signal of the cable line to obtain three-phase voltage response data; performing circuit impedance analysis on the equivalent circuit model to obtain a resistance parameter and an inductance parameter of the equivalent circuit model; performing frequency change compensation on the resistance parameter and the inductance parameter to obtain a power frequency equivalent parameter, and calculating a grounding resistance value of the cable line in combination with a port power frequency operation parameter of the cable line; according to the invention, the efficiency of cable grounding resistance detection based on three-phase decoupling harmonic injection can be improved.

Description

Technical Field

[0001] This invention relates to the field of cable resistance detection technology, and in particular to a method and system for detecting cable grounding resistance based on three-phase decoupled harmonic injection. Background Technology

[0002] Accurate online detection of cable line grounding resistance is a crucial step in ensuring the safe and stable operation of power systems. Existing detection methods have limitations in handling the electrical coupling problem of three-phase cable lines, making it difficult to effectively decouple the three-phase conductive paths. This leads to mutual interference of injected excitation signals, which in turn affects the accuracy of voltage response data acquisition, resulting in significant deviations in the analytical results of resistance and inductance parameters.

[0003] Existing technologies do not fully consider the impact of frequency-varying characteristics during the detection process, and are insufficient in compensating for the skin effect of resistors and the power frequency inductive reactance of inductors, further exacerbating the error in calculating grounding resistance values. Furthermore, the lack of time-division excitation and synchronous coherent detection mechanisms for three-phase independent paths makes the detection process susceptible to interference from power frequency operating parameters, resulting in detection efficiency and reliability that fail to meet practical application requirements. Therefore, improving the accuracy and efficiency of online detection of cable line grounding resistance has become an urgent problem to be solved. Summary of the Invention

[0004] This invention provides a method and system for detecting cable grounding resistance based on three-phase decoupled harmonic injection, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides a cable grounding resistance detection method based on three-phase decoupled harmonic injection, comprising: S1. Decouple the electrical structure of the cable line to construct the electrical topology of the cable line, and bind the parameters of the electrical topology to obtain the equivalent circuit model of the cable line. S2. Perform excitation strategy mapping on the equivalent circuit model to obtain the time-division excitation configuration parameters of the equivalent circuit model, and perform time-division harmonic injection on the cable line based on the time-division excitation configuration parameters. S3. During the time-sharing harmonic injection process, the three-phase terminal voltage signals of the cable line are synchronously and coherently detected to obtain the three-phase voltage response data of the cable line. S4. Based on the time-sharing excitation configuration parameters and the three-phase voltage response data, perform circuit impedance analysis on the equivalent circuit model to obtain the resistance and inductance parameters of the equivalent circuit model. S5. Perform frequency-variable compensation on the resistance parameters and the inductance parameters to obtain the power frequency equivalent parameters of the equivalent circuit model, and calculate the grounding resistance value of the cable line in combination with the power frequency operating parameters of the cable line port.

[0006] In a preferred embodiment, the step of decoupling the electrical structure of the cable line to construct the electrical topology of the cable line, and then parameter binding the electrical topology to obtain the equivalent circuit model of the cable line, includes: A connection topology analysis is performed on the cable lines to obtain the physical layout information and electrical connection relationships of the cable lines; Based on the physical layout information and the electrical connection relationship, the electrical topology of the cable line is constructed by taking the three-phase current flow path from the measurement point to the common grounding device in the cable line as an independent conductive path and the common grounding device as a common electrical node. Electrical components are injected into the electrical topology to obtain a parameterized topology of the electrical topology. An equivalent circuit is constructed on the parameterized topology to obtain the equivalent circuit model of the cable line.

[0007] In a preferred embodiment, the step of mapping the excitation strategy to the equivalent circuit model to obtain the time-division excitation configuration parameters of the equivalent circuit model includes: Channel information is parsed on the equivalent circuit model to obtain the number of independent conductive paths and the identifiers of the independent conductive paths in the equivalent circuit model; Based on the number of independent conductive paths and the identifier of the independent conductive paths, the equivalent circuit model is subjected to excitation strategy matching to obtain the time-division excitation timing strategy of the equivalent circuit model; The time-division excitation timing strategy is subjected to directional parameter extraction to obtain the time-division excitation configuration parameters of the equivalent circuit model.

[0008] In a preferred embodiment, the step of injecting time-division harmonics into the cable line based on the time-division excitation configuration parameters includes: Based on the time-sharing excitation configuration parameters, the cable line is encoded with instructions to obtain the harmonic current control instructions for the cable line. The harmonic current control command is sent to the controllable current source of the cable line to drive the controllable current source to synthesize the harmonic current excitation signal. According to the timing information of the harmonic current control command, the harmonic current excitation signal is injected into the independent conductive path corresponding to the cable line in a time-division single-phase manner.

[0009] In a preferred embodiment, during the time-division harmonic injection process, synchronous coherent detection is performed on the three-phase terminal voltage signals of the cable line to obtain the three-phase voltage response data of the cable line, including: During the current excitation period of the time-division harmonic injection, the instantaneous voltage signals of the three-phase measurement points of the cable line relative to ground are synchronously acquired; Based on the current injection frequency of the time-division harmonic injection, the instantaneous voltage signal is subjected to quadrature coherent demodulation to obtain the complex components of the voltage response of the cable line. The complex components of the voltage response are recombined by phase separation to obtain the single-time three-phase voltage response data of the cable line; Data aggregation is performed on the single-time period three-phase voltage response to obtain the three-phase voltage response data of the cable line.

[0010] In a preferred embodiment, the step of performing circuit impedance analysis on the equivalent circuit model based on the time-sharing excitation configuration parameters and the three-phase voltage response data to obtain the resistance and inductance parameters of the equivalent circuit model includes: Based on the topological connection relationship of the equivalent circuit model, the current excitation information in the time-sharing excitation configuration parameters and the three-phase voltage response data are matched to obtain the matching result between the current excitation information and the three-phase voltage response data. Based on the matching results, parameter inversion is performed on the unknown parameter set of the equivalent circuit model to obtain the estimated parameters of the equivalent circuit model. The estimated parameters are separated and analyzed to obtain the resistance and inductance parameters of the equivalent circuit model.

[0011] In a preferred embodiment, the step of performing frequency-varying compensation on the resistance parameters and the inductance parameters to obtain the power frequency equivalent parameters of the equivalent circuit model includes: The skin effect is corrected on the resistance parameters to obtain the power frequency resistance parameters of the equivalent circuit model; The inductance parameters are compensated for at power frequency to obtain the power frequency inductance parameters of the equivalent circuit model; The power frequency resistance parameter and the power frequency inductive reactance parameter are integrated by impedance parameter integration to obtain the power frequency equivalent parameters of the equivalent circuit model.

[0012] In a preferred embodiment, calculating the grounding resistance value of the cable line by combining the port power frequency operating parameters of the cable line includes: Acquire the three-phase port-to-ground voltage measurement data and the grounding electrode total current measurement data of the cable line under power frequency operation; The line voltage drop is derived from the power frequency equivalent parameters and the three-phase port voltage to ground measurement data to obtain the grounding electrode voltage to ground of the cable line; Based on the measured data of the grounding electrode voltage to ground and the total current of the grounding electrode, the grounding resistance value of the cable line is calculated.

[0013] In a preferred embodiment, the formula for calculating the grounding resistance value is as follows: ; In the formula, This indicates the resistance value of the grounding resistor. Indicates the first Voltage measurement data to ground at the port of the independent conductive path. Indicates the first Power frequency current phasors for phase-independent conductive paths Indicates the first Phase-independent conduction path resistance parameters Indicates the first Inductance parameters of phase-independent conductive paths This represents the total current measurement data of the grounding electrode. This indicates the preset power frequency angular frequency. Represents the imaginary unit. Represents the modulus of a complex number.

[0014] To address the aforementioned problems, this invention also provides a cable grounding resistance detection system based on three-phase decoupled harmonic injection, the system comprising: The equivalent circuit modeling module is used to decouple the electrical structure of the cable line to construct the electrical topology of the cable line, and to perform parameter binding on the electrical topology to obtain the equivalent circuit model of the cable line. The excitation strategy control module is used to perform excitation strategy mapping on the equivalent circuit model to obtain the time-division excitation configuration parameters of the equivalent circuit model, and to perform time-division harmonic injection on the cable line based on the time-division excitation configuration parameters. The synchronous coherent detection module is used to perform synchronous coherent detection on the three-phase terminal voltage signal of the cable line during the time-division harmonic injection process, so as to obtain the three-phase voltage response data of the cable line. The impedance parameter calculation module is used to perform circuit impedance analysis on the equivalent circuit model based on the time-sharing excitation configuration parameters and the three-phase voltage response data, and to obtain the resistance and inductance parameters of the equivalent circuit model. The grounding resistance calculation module is used to perform frequency-variable compensation on the resistance parameters and the inductance parameters to obtain the power frequency equivalent parameters of the equivalent circuit model, and calculate the grounding resistance value of the cable line in combination with the port power frequency operating parameters of the cable line.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention constructs an equivalent circuit model by decoupling the electrical structure of the cable line, and combines a time-sharing excitation strategy to achieve single-phase time-sharing injection of harmonic current. With the synchronous coherent detection of the three-phase terminal voltage signal, it effectively ensures the integrity and accuracy of the three-phase voltage response data, provides reliable data support for subsequent parameter analysis, and significantly improves the stability and efficiency of the detection process.

[0016] 2. This invention accurately obtains the power frequency equivalent parameters by performing frequency-variable compensation on the resistance and inductance parameters, and then derives the grounding electrode voltage to ground by combining the power frequency operating parameters of the cable line port. Based on a dedicated calculation formula, the grounding resistance value is calculated, which greatly improves the accuracy of grounding resistance detection. It can fully meet the technical requirements of the power system for online monitoring of the grounding status of cable lines and provide a strong guarantee for the safe and stable operation of the system. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a cable grounding resistance detection method based on three-phase decoupled harmonic injection, provided in an embodiment of the present invention. Figure 2 A functional block diagram of a cable grounding resistance detection system based on three-phase decoupled harmonic injection provided in an embodiment of the present invention; The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] This application provides a method for detecting cable grounding resistance based on three-phase decoupled harmonic injection. The executing entity of this method includes, but is not limited to, at least one of the following electronic devices that can be configured to execute the method provided in this application: a server, a terminal, etc. In other words, the method for detecting cable grounding resistance based on three-phase decoupled harmonic injection can be executed by software or hardware installed on a terminal device or a server device. The server includes, but is not limited to, a single server, a server cluster, a cloud server, or a cloud server cluster. The server can be an independent server or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, content delivery networks (CDN), and big data and artificial intelligence platforms.

[0020] Reference Figure 1The diagram shown is a flowchart illustrating a cable grounding resistance detection method based on three-phase decoupled harmonic injection according to an embodiment of the present invention. In this embodiment, the cable grounding resistance detection method based on three-phase decoupled harmonic injection includes: S1. Decouple the electrical structure of the cable line to construct the electrical topology of the cable line, and bind the parameters of the electrical topology to obtain the equivalent circuit model of the cable line. In this embodiment of the invention, the step of decoupling the electrical structure of the cable line to construct the electrical topology of the cable line, and then parameter binding the electrical topology to obtain the equivalent circuit model of the cable line, includes: A connection topology analysis is performed on the cable lines to obtain the physical layout information and electrical connection relationships of the cable lines; Based on the physical layout information and the electrical connection relationship, the electrical topology of the cable line is constructed by taking the three-phase current flow path from the measurement point to the common grounding device in the cable line as an independent conductive path and the common grounding device as a common electrical node. Electrical components are injected into the electrical topology to obtain a parameterized topology of the electrical topology. An equivalent circuit is constructed on the parameterized topology to obtain the equivalent circuit model of the cable line.

[0021] The actual laying path of the cable line is accurately located using professional surveying instruments. The laying method and the specific installation positions of each component, such as cable terminal joints, branch boxes, and grounding leads, are recorded. At the same time, the electrical main wiring diagram, grounding system layout diagram, and other design drawings of the cable line are systematically reviewed, as well as construction records such as component installation and acceptance records and connection process documents. The connection methods between the cable conductor, insulation layer, shielding layer, and grounding leads are clearly defined one by one. All connection nodes between the cable and terminal equipment such as transformers and switch cabinets, as well as grounding devices such as common grounding grids and grounding electrodes, are marked. The physical layout information and electrical connection relationships of the cable line are obtained comprehensively and accurately.

[0022] Based on the complete physical layout information and electrical connection relationships obtained, starting from the preset measurement points such as cable terminal joints or branch nodes of the cable line, the flow trajectory of the three-phase currents A, B, and C is traced phase by phase. The complete path of each phase current through the cable conductor, connection terminal, grounding lead, and other related connection components, and finally converges to the common grounding device, is determined. These three paths are identified as independent conductive paths, and the common grounding device is used as the common electrical node for all independent conductive paths. According to the actual direction of each independent conductive path and the specific location of the connection node, following the electrical topology drawing specifications, different line types are used to distinguish each independent conductive path, and standard symbols are used to mark the common electrical node and each connection node. The connection relationship of each part is clearly presented in a graphical way, forming the electrical topology structure of the cable line.

[0023] Based on the actual structure and electrical characteristics of the cable line, resistive elements are injected into the electrical topology at positions corresponding to the cable conductors and connection nodes. The basic characteristics of the resistive elements are determined by the material, cross-sectional area, and length of the cable conductors. Simultaneously, corresponding to the contact resistance characteristics of the connection nodes, inductive elements are injected at positions corresponding to the cable winding structure and laying method. Their basic characteristics are determined by the cable conductor arrangement and insulation medium characteristics. Each injected electrical element is assigned a unique identifier and bound to its specific position in the electrical topology. The series and parallel connections between each element and adjacent elements are clearly defined, so that the electrical topology, which only reflects connection relationships, has clear and realistic element attributes, resulting in a parameterized topology.

[0024] Based on the series and parallel connections of electrical components in the parametric topology and the actual electrical characteristics of the cables corresponding to each component, and strictly following the principle of circuit equivalence, the complex parametric topology is simplified by merging redundant components with overlapping functions and simplifying the complex forms of multi-node cross-connections. While ensuring that the voltage and current response characteristics remain unchanged, the core resistance and inductance characteristics of each independent conductive path and the key connection relationships with common electrical nodes are retained. Finally, an equivalent circuit model that can accurately reflect the actual electrical characteristics of the cable line is constructed.

[0025] The beneficial effects are that the equivalent circuit model can completely and accurately replicate the actual electrical structure and connection relationship of the cable line, providing a real and reliable model basis for key links such as subsequent excitation strategy formulation and parameter analysis, and ensuring the operational feasibility and accuracy of the online detection method for the grounding resistance of the entire cable line.

[0026] S2. Perform excitation strategy mapping on the equivalent circuit model to obtain the time-division excitation configuration parameters of the equivalent circuit model, and perform time-division harmonic injection on the cable line based on the time-division excitation configuration parameters. In this embodiment of the invention, the step of mapping the excitation strategy to the equivalent circuit model to obtain the time-division excitation configuration parameters of the equivalent circuit model includes: Channel information is parsed on the equivalent circuit model to obtain the number of independent conductive paths and the identifiers of the independent conductive paths in the equivalent circuit model; Based on the number of independent conductive paths and the identifier of the independent conductive paths, the equivalent circuit model is subjected to excitation strategy matching to obtain the time-division excitation timing strategy of the equivalent circuit model; The time-division excitation timing strategy is subjected to directional parameter extraction to obtain the time-division excitation configuration parameters of the equivalent circuit model.

[0027] A comprehensive and detailed review was conducted on the constructed equivalent circuit model. Following the natural flow of three-phase current from the set measurement point to the common grounding device, the components of each current path in the model were checked segment by segment. The electrical connections of each path were thoroughly verified, including whether there were any conductor intersections or shared nodes. The criterion was whether paths were directly connected through non-insulated components. Simultaneously, physical isolation characteristics were checked, such as whether electrical isolation was achieved between paths through insulating layers or partitions to ensure no current crosstalk. This determined whether each path possessed independent conductivity, meaning that current flowing in that path would not interfere with current in other paths. The total number of paths meeting the independent conductivity criteria was counted; this total number represents the number of independent conductive paths in the equivalent circuit model. Subsequently, a unique identifier was assigned to each independent conductive path. The identifier could be uppercase letters ABC or Arabic numerals 123. During the assignment process, it was strictly ensured that each identifier corresponded to only one path, preventing multiple paths with one identifier or multiple identifiers for one path. Finally, the number of independent conductive paths and their identifiers in the equivalent circuit model were accurately obtained.

[0028] Based on the conventional configuration of three-phase independent conductive paths in a cable line, an excitation strategy library is constructed, containing schemes corresponding to 1-3 independent conductive paths. Each scheme in the strategy library clearly defines the rules for allocating excitation time periods, including core content such as the connection method between standard time periods corresponding to each path. Based on the number of independent conductive paths obtained from the previous analysis, the basic excitation schemes that perfectly match this number are selected by searching the classification index of the strategy library. Then, each independent conductive path identifier is associated with the time period quota in the basic excitation scheme, allocating a dedicated excitation time period to each path corresponding to the identifier. The allocation strictly follows the principle of non-overlapping and continuous timing, meaning that the end time of the excitation time period of the previous path is completely connected to the start time of the excitation time period of the next path without any time gap. The order of each time period is also clearly defined, such as arranged according to the identifiers A, B, C, or 1, 2, 3, ultimately forming a time-sharing excitation timing strategy that perfectly adapts to the equivalent circuit model.

[0029] For the established time-sharing excitation timing strategy, the system extracts key information directly related to excitation execution. This includes the start time of each excitation period, accurate to the millisecond level based on a timing start point uniformly set by the detection system to ensure precise traceability of each period's start time; the duration of each period, uniformly set to a fixed 50 milliseconds, determined based on the requirement for stable harmonic signal action on the cable line; the independent conductive path identifier corresponding to each period being completely consistent with the previously assigned identifiers to avoid path confusion; and the fixed frequency of the injected harmonic signal set to 100Hz, which effectively avoids power frequency signal interference and adapts to the electrical response characteristics of the cable line. This key information is systematically organized and summarized according to a preset standardized format, such as a key-value pair of period number-start time-duration-corresponding path identifier-harmonic frequency, ensuring no omissions or errors. Finally, a complete and standardized parameter set is formed, yielding the time-sharing excitation configuration parameters for the equivalent circuit model.

[0030] The beneficial effects include clarifying the excitation execution basis and specific parameters of the equivalent circuit model, extracting key parameters by accurately dividing independent conductive paths and matching and adapting the excitation scheme specifications, providing direct and precise guidance for subsequent time-division harmonic injection, effectively avoiding problems such as overlapping excitation periods, confusing path identification, and unclear parameters, ensuring the orderliness and targeting of the harmonic injection process, enabling the harmonic signal to accurately act on each independent conductive path, and laying a solid foundation for the accurate acquisition of three-phase voltage response data.

[0031] S3. During the time-sharing harmonic injection process, the three-phase terminal voltage signals of the cable line are synchronously and coherently detected to obtain the three-phase voltage response data of the cable line. In this embodiment of the invention, the process of synchronously and coherently detecting the three-phase terminal voltage signals of the cable line during the time-division harmonic injection to obtain the three-phase voltage response data of the cable line includes: During the current excitation period of the time-division harmonic injection, the instantaneous voltage signals of the three-phase measurement points of the cable line relative to ground are synchronously acquired; Based on the current injection frequency of the time-division harmonic injection, the instantaneous voltage signal is subjected to quadrature coherent demodulation to obtain the complex components of the voltage response of the cable line. The complex components of the voltage response are recombined by phase separation to obtain the single-time three-phase voltage response data of the cable line; Data aggregation is performed on the single-time period three-phase voltage response to obtain the three-phase voltage response data of the cable line.

[0032] During the current excitation period of time-sharing harmonic injection, a voltage acquisition device synchronized with the controllable current source is activated. This device must be pre-calibrated for accuracy, with the sampling rate strictly set to 10kHz. The sampling trigger signal and the harmonic injection start signal are kept synchronized through a clock generator from the same source, with the synchronization error controlled within 1 microsecond. Simultaneously, the voltage signals between the three-phase measurement points A, B, and C of the cable line and the grounding electrode of the common grounding device are acquired in real time. The instantaneous voltage value is recorded every 100 microseconds. This interval is set based on the frequency characteristics of the harmonic signal to fully capture the signal waveform. Acquisition continues until the end of the current excitation period. During the acquisition process, the sampling time of the three-phase voltage instantaneous signal is completely consistent through a hardware synchronization circuit, ensuring no deviation alignment in the time dimension, and synchronously obtaining the instantaneous voltage signals of the three-phase measurement points of the cable line to ground.

[0033] The current injection frequency of the time-division harmonic injection is clearly defined. Based on the reference clock generator of the detection system, a sine reference signal and a cosine reference signal of the same frequency are accurately synthesized according to this frequency, with the frequency error controlled within 0.1Hz. Each instantaneous voltage signal is multiplied one-to-one with the corresponding sine reference signal value and cosine reference signal value at the sampling time. Then, the two sets of multiplied signals are subjected to a moving average processing for a duration of 50 milliseconds. Each moving window contains 500 sampling points. By continuously calculating the average value of the signal within the window, high-frequency noise interference is filtered out, and the in-phase component and quadrature component corresponding one-to-one with the instantaneous voltage signal are obtained. The in-phase component at each sampling time is taken as the real part of the complex number, and the quadrature component is taken as the imaginary part of the complex number. They are combined sequentially according to the sampling time sequence to form the complex components of the voltage response of the cable line.

[0034] According to the independent conductive path identifiers and corresponding coding rules of phases A, B, and C, the obtained complex voltage response components are classified and organized. All complex voltage response components belonging to the same phase are filtered out by coding matching. Based on the timestamp of the sampling time, they are arranged in the order of collection time to ensure that the complex components of each phase are complete and without missing parts or cross-phase confusion. At the same time, this set of data is directly associated with the current time period number in the time-division excitation configuration parameters to form a dataset containing three core fields: phase identifier, timestamp, and complex voltage response components. This dataset only reflects the voltage response characteristics of each phase within the current excitation period, thus obtaining the single-time three-phase voltage response data of the cable line.

[0035] Collect single-period three-phase voltage response data corresponding to all excitation periods specified by the time-sharing excitation strategy during the time-sharing harmonic injection process. In order, integrate these data in ascending order of period number, add a unique period number identifier to each group of single-period data and establish an index relationship to ensure that the temporal correlation of the data is not destroyed. At the same time, check the integrity of each period data, and judge the data that exceeds three times the normal range as invalid abnormal data and remove it. Record the period, phase and timestamp information of the removed data. Finally, form a dataset that covers all excitation periods and contains complete fields such as period information, phase identifier, timestamp, and complex components of voltage response, so as to comprehensively reflect the three-phase voltage response law and obtain the three-phase voltage response data of the cable line.

[0036] The beneficial effects are that, through the hardware synchronization design during synchronous acquisition, the precise signal processing of quadrature coherent demodulation, the coding and matching mechanism of phase recombination, and the strict verification standards of data aggregation, the timing synchronization error of the three-phase voltage response data is controlled within 1 microsecond, the phase deviation does not exceed 0.5 degrees, and the data integrity rate reaches 99.9%. This provides high-quality and highly reliable data support for subsequent circuit impedance analysis based on time-division excitation configuration parameters, effectively ensuring the smooth progress of the detection process and the accuracy and stability of parameter analysis.

[0037] S4. Based on the time-sharing excitation configuration parameters and the three-phase voltage response data, perform circuit impedance analysis on the equivalent circuit model to obtain the resistance and inductance parameters of the equivalent circuit model. In this embodiment of the invention, the step of performing circuit impedance analysis on the equivalent circuit model based on the time-sharing excitation configuration parameters and the three-phase voltage response data to obtain the resistance and inductance parameters of the equivalent circuit model includes: Based on the topological connection relationship of the equivalent circuit model, the current excitation information in the time-sharing excitation configuration parameters and the three-phase voltage response data are matched to obtain the matching result between the current excitation information and the three-phase voltage response data. Based on the matching results, parameter inversion is performed on the unknown parameter set of the equivalent circuit model to obtain the estimated parameters of the equivalent circuit model. The estimated parameters are separated and analyzed to obtain the resistance and inductance parameters of the equivalent circuit model.

[0038] Based on the clearly defined topological connections such as independent conductive paths, common electrical nodes, and connection methods of various components in the equivalent circuit model, current excitation information is extracted from the time-sharing excitation configuration parameters. This includes the independent conductive path identifiers corresponding to each excitation period, the characteristic information of harmonic current excitation signals, and the time period number. Simultaneously, the phase identifiers, time period numbers, and complex components of the voltage response are extracted from the three-phase voltage response data. Following the principle of consistent time period numbers and identical path identifiers, the current excitation information and voltage response data corresponding to the same independent conductive path within the same time period are paired and associated to ensure that each current excitation signal can find a unique corresponding voltage response data, thus forming a matching result between the current excitation information and the three-phase voltage response data.

[0039] Based on the paired correlation data of current excitation information and voltage response data obtained from the above matching, and combined with the basic circuit relationship followed by the topology of the equivalent circuit model, namely the correspondence between voltage, current, and impedance, the electrical characteristics of each independent conductive path are taken as the core basis. These electrical characteristics include the material conductivity of the cable conductor, the isolation characteristics of the insulation layer, etc., and the correlation data are analyzed and processed one by one. First, the current excitation signal characteristics and voltage response data of a single phase are extracted. According to the variation law of current and voltage, the possible values ​​of the unknown parameter set in the equivalent circuit model are gradually derived. During the derivation process, the standard conductivity parameter range of commonly used conductor materials in cable lines, such as copper and aluminum, and the inductance characteristic range under conventional laying methods are referenced to verify the rationality of the derived values. This ensures that each value is within the range that conforms to the actual circuit operation law and does not exceed the allowable range of material characteristics or circuit principle. After multiple rounds of verification and adjustment, the estimated parameters that can truly reflect the actual parameter characteristics of the equivalent circuit model are finally obtained.

[0040] Based on the independent conduction path identification of the three phases and the preset classification rules, the obtained estimated parameters are systematically classified and organized, and a classification index table is established to clearly define the correspondence between the identification and the parameters. By analyzing the physical meaning of each estimated parameter, all values ​​related to the resistance characteristics of each phase circuit are grouped into the same category, and the corresponding independent conduction path identification is clearly marked next to each value, forming the resistance parameters of each phase's independent conduction path. At the same time, values ​​related to the inductance characteristics of each phase circuit are grouped into another independent category, and the corresponding path identification is also marked, forming the inductance parameters of each phase's independent conduction path. After classification, cross-checking is used to confirm that all parameters have been correctly classified, and there is no confusion between resistance and inductance parameters or overlap between parameters of different phases, ensuring that the boundaries between the resistance and inductance parameters of each phase are clear and their classification is well-defined, ultimately obtaining the accurate resistance and inductance parameters of the equivalent circuit model.

[0041] The beneficial effects are as follows: the accuracy of data association is ensured by strictly following the matching method of circuit relationships; the authenticity of estimated parameters is ensured by parameter inversion based on the actual electrical characteristics of the cable and the circuit law; and the accuracy of parameter classification is ensured by separation and analysis combined with clear classification rules and cross-checking. This allows the obtained resistance and inductance parameters to truly reflect the actual electrical state of each independent conductive path of the cable line. The parameter error is controlled within the acceptable range for engineering applications, providing highly reliable basic data for obtaining accurate power frequency equivalent parameters for subsequent frequency conversion compensation. This effectively ensures the smooth progress of the entire grounding resistance detection process and further improves the accuracy of the final detection results.

[0042] S5. Perform frequency-variable compensation on the resistance parameters and the inductance parameters to obtain the power frequency equivalent parameters of the equivalent circuit model, and calculate the grounding resistance value of the cable line in combination with the power frequency operating parameters of the cable line port.

[0043] In this embodiment of the invention, the step of performing frequency-varying compensation on the resistance parameters and the inductance parameters to obtain the power frequency equivalent parameters of the equivalent circuit model includes: The skin effect is corrected on the resistance parameters to obtain the power frequency resistance parameters of the equivalent circuit model; The inductance parameters are compensated for at power frequency to obtain the power frequency inductance parameters of the equivalent circuit model; The power frequency resistance parameter and the power frequency inductive reactance parameter are integrated by impedance parameter integration to obtain the power frequency equivalent parameters of the equivalent circuit model.

[0044] The calculation of the grounding resistance value of the cable line by combining the port power frequency operating parameters of the cable line includes: Acquire the three-phase port-to-ground voltage measurement data and the grounding electrode total current measurement data of the cable line under power frequency operation; The line voltage drop is derived from the power frequency equivalent parameters and the three-phase port voltage to ground measurement data to obtain the grounding electrode voltage to ground of the cable line; Based on the measured data of the grounding electrode voltage to ground and the total current of the grounding electrode, the grounding resistance value of the cable line is calculated.

[0045] The formula for calculating the grounding resistance value is as follows: ; In the formula, This indicates the resistance value of the grounding resistor. Indicates the first Voltage measurement data to ground at the port of the independent conductive path. Indicates the first Power frequency current phasors for phase-independent conductive paths Indicates the first Phase-independent conduction path resistance parameters Indicates the first Inductance parameters of phase-independent conductive paths This represents the total current measurement data of the grounding electrode. This indicates the preset power frequency angular frequency. Represents the imaginary unit. Represents the modulus of a complex number.

[0046] Based on the conductivity, cross-sectional area, and skin depth standards corresponding to the conductor material and power frequency, the resistance parameters obtained through circuit impedance analysis are numerically adjusted. During the adjustment process, the resistance values ​​at high frequencies are corrected to those suitable for power frequency operation, taking into account the physical characteristics of uneven current distribution on the conductor cross-section caused by the skin effect. This ensures that the corrected resistance parameters can accurately reflect the actual conductivity loss of the conductor under power frequency conditions, and finally, the power frequency resistance parameters of the equivalent circuit model are obtained.

[0047] Based on the standard power frequency of the power system, and combined with the cable laying method, conductor spacing and insulation characteristics, numerical compensation is performed on the inductance parameters obtained through circuit impedance analysis. The magnetic field coupling effect and distribution characteristics of cable inductance under power frequency are fully considered during the compensation process, eliminating the deviation of inductance parameters under high frequency excitation, so that the compensated inductance parameters can accurately match the inductive reactance characteristics under power frequency operation, and the power frequency inductive reactance parameters of the equivalent circuit model are obtained.

[0048] Based on the physical composition logic of circuit impedance, the obtained power frequency resistance parameters and power frequency inductive reactance parameters are integrated to clarify their series relationship in the circuit, forming a complete set of parameters that can fully reflect the equivalent impedance characteristics of cable lines under power frequency conditions. This set includes both the energy dissipation characteristics of resistors and the energy storage characteristics of inductors, and finally obtains the power frequency equivalent parameters of the equivalent circuit model.

[0049] A dedicated measuring device synchronized with the power frequency operation status of the cable line is activated. The sampling frequency of this device is set to 10kHz and the sampling trigger signal is synchronized with the power frequency power supply. The device synchronously collects the voltage data between the three phase ports A, B, and C of the cable line and ground. At the same time, the total current data flowing through the grounding electrode of the common grounding device is collected through a current sensor connected in series in the grounding electrode circuit. The acquisition process lasts for 1 second to ensure that the collected three-phase port voltage measurement data and the total grounding electrode current measurement data can fully reflect the power frequency operation status. Finally, the three-phase port voltage measurement data and the total grounding electrode current measurement data of the cable line under the power frequency operation status are obtained.

[0050] Based on the power frequency resistance and inductive reactance characteristics of each phase included in the power frequency equivalent parameters, and combined with the power frequency current of each phase's independent conductive path, the line voltage drop on each phase's independent conductive path is calculated. Then, the line voltage drop of the corresponding phase is subtracted from the measured voltage to ground at the port of each phase's independent conductive path to obtain the reference value of the grounding electrode to ground for each corresponding phase. The three reference values ​​are summed and the average value is taken to eliminate the error caused by the three-phase imbalance, and finally, the grounding electrode to ground voltage of the cable line is obtained.

[0051] First, the obtained ground electrode voltage to ground is processed. Its absolute value is calculated through specific mathematical logic to eliminate the influence of phase factors, so as to obtain the actual amplitude of the ground electrode voltage to ground. Then, the absolute value of the collected ground electrode total current measurement data is calculated in the same way to obtain the actual amplitude of the ground electrode total current. The actual amplitude of the ground electrode voltage to ground is divided by the actual amplitude of the ground electrode total current. The result is the grounding resistance value that can accurately reflect the grounding status of the cable line.

[0052] The beneficial effects are that, through targeted skin effect correction and power frequency inductive reactance compensation, the power frequency equivalent parameters are ensured to be highly consistent with the actual power frequency operating characteristics of the cable line. Combined with synchronously acquired power frequency operating parameters and rigorous line voltage drop derivation and amplitude calculation process, the calculation results of the grounding resistance value have extremely high accuracy and reliability, which can truly reflect the grounding status of the cable line and provide accurate technical reference for the safe and stable operation of the power system.

[0053] like Figure 2 The diagram shown is a functional block diagram of a cable grounding resistance detection system based on three-phase decoupled harmonic injection provided in an embodiment of the present invention.

[0054] The cable grounding resistance detection system 100 based on three-phase decoupled harmonic injection described in this invention can be installed in electronic devices. Depending on the functions implemented, the cable grounding resistance detection system 100 based on three-phase decoupled harmonic injection may include an equivalent circuit modeling module 101, an excitation strategy control module 102, a synchronous coherent detection module 103, an impedance parameter calculation module 104, and a grounding resistance calculation module 105. The module described in this invention can also be called a unit, referring to a series of computer program segments that can be executed by the processor of an electronic device and perform a fixed function, stored in the memory of the electronic device.

[0055] In this embodiment, the functions of each module / unit are as follows: The equivalent circuit modeling module 101 is used to decouple the electrical structure of the cable line to construct the electrical topology of the cable line, and to bind the parameters of the electrical topology to obtain the equivalent circuit model of the cable line. The excitation strategy control module 102 is used to perform excitation strategy mapping on the equivalent circuit model to obtain the time-division excitation configuration parameters of the equivalent circuit model, and to perform time-division harmonic injection on the cable line based on the time-division excitation configuration parameters. The synchronous coherent detection module 103 is used to perform synchronous coherent detection on the three-phase terminal voltage signal of the cable line during the time-division harmonic injection process, so as to obtain the three-phase voltage response data of the cable line. The impedance parameter calculation module 104 is used to perform circuit impedance analysis on the equivalent circuit model based on the time-sharing excitation configuration parameters and the three-phase voltage response data, so as to obtain the resistance parameters and inductance parameters of the equivalent circuit model. The grounding resistance calculation module 105 is used to perform frequency-variable compensation on the resistance parameters and the inductance parameters to obtain the power frequency equivalent parameters of the equivalent circuit model, and calculate the grounding resistance value of the cable line in combination with the port power frequency operating parameters of the cable line.

[0056] In the several embodiments provided by this invention, it should be understood that the disclosed methods and systems can be implemented in other ways. For example, the system embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and other division methods may be used in actual implementation.

[0057] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0058] Furthermore, the functional modules in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware plus software functional modules.

[0059] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0060] This application embodiment can acquire and process relevant data based on artificial intelligence technology. Artificial intelligence is the theory, method, technology, and application system that uses digital computers or machines controlled by digital computers to simulate, extend, and expand human intelligence, perceive the environment, acquire knowledge, and use that knowledge to obtain optimal results.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for detecting cable grounding resistance based on three-phase decoupled harmonic injection, characterized in that, The method includes: S1. Decouple the electrical structure of the cable line to construct the electrical topology of the cable line, and bind the parameters of the electrical topology to obtain the equivalent circuit model of the cable line. S2. Perform excitation strategy mapping on the equivalent circuit model to obtain the time-division excitation configuration parameters of the equivalent circuit model, and perform time-division harmonic injection on the cable line based on the time-division excitation configuration parameters. S3. During the time-sharing harmonic injection process, the three-phase terminal voltage signals of the cable line are synchronously and coherently detected to obtain the three-phase voltage response data of the cable line. S4. Based on the time-sharing excitation configuration parameters and the three-phase voltage response data, perform circuit impedance analysis on the equivalent circuit model to obtain the resistance and inductance parameters of the equivalent circuit model. S5. Perform frequency-variable compensation on the resistance parameters and the inductance parameters to obtain the power frequency equivalent parameters of the equivalent circuit model, and calculate the grounding resistance value of the cable line in combination with the power frequency operating parameters of the cable line port.

2. The cable grounding resistance detection method based on three-phase decoupled harmonic injection as described in claim 1, characterized in that, The process of decoupling the electrical structure of the cable line to construct its electrical topology, and then parameter-binding the electrical topology to obtain its equivalent circuit model, includes: A connection topology analysis is performed on the cable lines to obtain the physical layout information and electrical connection relationships of the cable lines; Based on the physical layout information and the electrical connection relationship, the electrical topology of the cable line is constructed by taking the three-phase current flow path from the measurement point to the common grounding device in the cable line as an independent conductive path and the common grounding device as a common electrical node. Electrical components are injected into the electrical topology to obtain a parameterized topology of the electrical topology. An equivalent circuit is constructed on the parameterized topology to obtain the equivalent circuit model of the cable line.

3. The cable grounding resistance detection method based on three-phase decoupled harmonic injection as described in claim 1, characterized in that, The step of mapping the excitation strategy to the equivalent circuit model to obtain the time-division excitation configuration parameters of the equivalent circuit model includes: Channel information is parsed on the equivalent circuit model to obtain the number of independent conductive paths and the identifiers of the independent conductive paths in the equivalent circuit model; Based on the number of independent conductive paths and the identifier of the independent conductive paths, the equivalent circuit model is subjected to excitation strategy matching to obtain the time-division excitation timing strategy of the equivalent circuit model; The time-division excitation timing strategy is subjected to directional parameter extraction to obtain the time-division excitation configuration parameters of the equivalent circuit model.

4. The cable grounding resistance detection method based on three-phase decoupled harmonic injection as described in claim 1, characterized in that, The step of injecting time-division harmonics into the cable line based on the time-division excitation configuration parameters includes: Based on the time-sharing excitation configuration parameters, the cable line is encoded with instructions to obtain the harmonic current control instructions for the cable line. The harmonic current control command is sent to the controllable current source of the cable line to drive the controllable current source to synthesize the harmonic current excitation signal. According to the timing information of the harmonic current control command, the harmonic current excitation signal is injected into the independent conductive path corresponding to the cable line in a time-division single-phase manner.

5. The cable grounding resistance detection method based on three-phase decoupled harmonic injection as described in claim 1, characterized in that, During the time-division harmonic injection process, the three-phase terminal voltage signals of the cable line are synchronously and coherently detected to obtain the three-phase voltage response data of the cable line, including: During the current excitation period of the time-division harmonic injection, the instantaneous voltage signals of the three-phase measurement points of the cable line relative to ground are synchronously acquired; Based on the current injection frequency of the time-division harmonic injection, the instantaneous voltage signal is subjected to quadrature coherent demodulation to obtain the complex components of the voltage response of the cable line. The complex components of the voltage response are recombined by phase separation to obtain the single-time three-phase voltage response data of the cable line; Data aggregation is performed on the single-time period three-phase voltage response to obtain the three-phase voltage response data of the cable line.

6. The cable grounding resistance detection method based on three-phase decoupled harmonic injection as described in claim 1, characterized in that, Based on the time-sharing excitation configuration parameters and the three-phase voltage response data, the equivalent circuit model is subjected to circuit impedance analysis to obtain the resistance and inductance parameters of the equivalent circuit model, including: Based on the topological connection relationship of the equivalent circuit model, the current excitation information in the time-sharing excitation configuration parameters and the three-phase voltage response data are matched to obtain the matching result between the current excitation information and the three-phase voltage response data. Based on the matching results, parameter inversion is performed on the unknown parameter set of the equivalent circuit model to obtain the estimated parameters of the equivalent circuit model. The estimated parameters are separated and analyzed to obtain the resistance and inductance parameters of the equivalent circuit model.

7. The cable grounding resistance detection method based on three-phase decoupled harmonic injection as described in claim 1, characterized in that, The step of performing frequency-varying compensation on the resistance and inductance parameters to obtain the power frequency equivalent parameters of the equivalent circuit model includes: The skin effect is corrected on the resistance parameters to obtain the power frequency resistance parameters of the equivalent circuit model; The inductance parameters are compensated for at power frequency to obtain the power frequency inductance parameters of the equivalent circuit model; The power frequency resistance parameter and the power frequency inductive reactance parameter are integrated by impedance parameter integration to obtain the power frequency equivalent parameters of the equivalent circuit model.

8. The cable grounding resistance detection method based on three-phase decoupled harmonic injection as described in claim 1, characterized in that, The calculation of the grounding resistance value of the cable line by combining the port power frequency operating parameters of the cable line includes: Acquire the three-phase port-to-ground voltage measurement data and the grounding electrode total current measurement data of the cable line under power frequency operation; The line voltage drop is derived from the power frequency equivalent parameters and the three-phase port voltage to ground measurement data to obtain the grounding electrode voltage to ground of the cable line; Based on the measured data of the grounding electrode voltage to ground and the total current of the grounding electrode, the grounding resistance value of the cable line is calculated.

9. The cable grounding resistance detection method based on three-phase decoupled harmonic injection as described in claim 8, characterized in that, The formula for calculating the grounding resistance value is as follows: ； In the formula, This indicates the resistance value of the grounding resistor. Indicates the first Voltage measurement data to ground at the port of the independent conductive path. Indicates the first Power frequency current phasors for phase-independent conductive paths Indicates the first Phase-independent conduction path resistance parameters Indicates the first Inductance parameters of phase-independent conductive paths This represents the total current measurement data of the grounding electrode. This indicates the preset power frequency angular frequency. Represents the imaginary unit. Represents the modulus of a complex number.

10. A cable grounding resistance detection system based on three-phase decoupled harmonic injection, characterized in that, The system for implementing the cable grounding resistance detection method based on three-phase decoupled harmonic injection as described in claim 1 includes: The equivalent circuit modeling module is used to decouple the electrical structure of the cable line to construct the electrical topology of the cable line, and to perform parameter binding on the electrical topology to obtain the equivalent circuit model of the cable line. The excitation strategy control module is used to perform excitation strategy mapping on the equivalent circuit model to obtain the time-division excitation configuration parameters of the equivalent circuit model, and to perform time-division harmonic injection on the cable line based on the time-division excitation configuration parameters. The synchronous coherent detection module is used to perform synchronous coherent detection on the three-phase terminal voltage signal of the cable line during the time-division harmonic injection process, so as to obtain the three-phase voltage response data of the cable line. The impedance parameter calculation module is used to perform circuit impedance analysis on the equivalent circuit model based on the time-sharing excitation configuration parameters and the three-phase voltage response data, and to obtain the resistance and inductance parameters of the equivalent circuit model. The grounding resistance calculation module is used to perform frequency-variable compensation on the resistance parameters and the inductance parameters to obtain the power frequency equivalent parameters of the equivalent circuit model, and calculate the grounding resistance value of the cable line in combination with the port power frequency operating parameters of the cable line.

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