A substation secondary cable network path optimization system based on topology

Abstract

The application relates to the technical field of cable laying of a substation secondary system, and discloses a substation secondary cable network path optimization system based on a topological structure. The system comprises an attribute analysis unit, a stimulating analysis unit, an interference calculation unit, a subgraph generation unit and a path searching unit. The attribute analysis unit is used for constructing a physical grounding attribute graph; the stimulating analysis unit is used for respectively performing matrix operations on peak value parameters of transient electromagnetic interference working conditions and two types of attenuation coefficients to generate a multi-working-condition transient excitation matrix; the interference calculation unit is used for calculating spatial field interference components, conduction interference components and core line port interference voltages of each channel section, and splicing the interference components into a composite interference cost tensor; the subgraph generation unit is used for removing over-standard channel sections to generate a feasible interference safety subgraph; the path searching unit is used for screening to generate a non-dominated candidate path set; and the path decision unit is used for dynamically allocating weights to the non-dominated candidate path set and performing weighted summation to determine an optimal path. The application improves the adaptability and rationality of substation secondary cable network path optimization.

Description

Technical Field

[0001] This application relates to the field of cable laying technology for substation secondary systems, and in particular to a substation secondary cable network path optimization system based on topology. Background Technology

[0002] The planning of secondary cable routing in substations is a crucial aspect of substation design and expansion / renovation. In current engineering practice, secondary cable routing is primarily based on the principles of shortest distance and ease of construction, determined through manual experience or simple geometric shortest path algorithms, treating cable trenches and cable trays as merely geometric pathways. However, the substation interior is not a quiet electromagnetic environment. Transient events such as short-circuit faults, lightning strikes, and disconnector operation can generate high-amplitude, wide-spectrum electromagnetic interference within a very short time. This interference couples to the secondary core wires through both spatial radiation and grounding grid conduction. Existing methods have two shortcomings: first, they fail to incorporate the transient electromagnetic field distribution around the pathway and grounding grid potential fluctuations into the routing decision, potentially causing cables laid along the shortest path to unknowingly cross areas of strong interference; second, they do not consider the varying sensitivities of different signal circuits to interference, and a one-size-fits-all approach with fixed weights cannot simultaneously meet the differentiated needs of various circuits such as DC tripping circuits, analog sampling circuits, and communication circuits. Furthermore, after the shielding layer is grounded at both ends, it forms a closed loop through the main grounding grid. When a local potential rise occurs in the grounding grid, a circulating current amplification effect will be formed. The simple geometric distance cannot reflect this coupling risk at all. Summary of the Invention

[0003] To address the aforementioned technical issues, this application provides a substation secondary cable network path optimization system based on topology, which improves the adaptability and rationality of substation secondary cable network path optimization.

[0004] This application provides a substation secondary cable network path optimization system based on topology, the system comprising: The attribute analysis unit is used to obtain the location information of signal transceiver equipment nodes, laying channel sections, grounding network nodes and high-voltage electrical equipment, and to construct a physical grounding attribute map that integrates channel physical attributes and grounding adjacency attributes. The excitation analysis unit is used to calculate the electromagnetic field attenuation coefficient of each channel segment by taking the location of high-voltage electrical equipment as the coordinate of the interference source and combining the grounding network impedance. It then performs matrix operations on the peak parameters of transient electromagnetic interference conditions and the two types of attenuation coefficients to generate a multi-condition transient excitation matrix. The interference calculation unit is used to calculate the spatial field interference component, conducted interference component and core wire port interference voltage of each channel segment according to the physical grounding attribute diagram and the multi-condition transient excitation matrix, and splice them into a composite interference cost tensor. The subgraph generation unit is used to generate a feasible interference safety subgraph by eliminating out-of-standard channel segments based on the composite interference cost tensor, according to the port interference voltage threshold, shielding layer current threshold and volume ratio upper limit; The path search unit is used to search for paths in the feasible interference safety subgraph, add extreme condition interference penalty terms and ground loop amplification penalty terms in the label update, and generate a set of non-dominated candidate paths by filtering through Pareto dominance relations. The path decision unit is used to dynamically assign weights to the set of non-dominant candidate paths based on voltage level, circuit type, operating frequency, and protection priority, and then perform a weighted summation to determine the preferred path.

[0005] Compared with the prior art, the beneficial effects of the present invention are at least as follows: First, by integrating the physical attributes of the channel with the grounding adjacency attributes into a physical grounding attribute map, the physical geometric features of the laying channel and the electrical connection relationship between the shielding layer and the grounding grid are modeled in the same topology. This provides a data foundation containing complete electrical coupling information for subsequent interference assessment and path search, overcoming the limitation of existing methods that only treat the channel as a geometric path. Simultaneously, by generating multi-condition transient excitation matrices and composite interference cost tensors, spatial field interference and conducted interference under three extreme conditions—short-circuit faults, lightning intrusion, and switching operations—are uniformly quantified into a three-dimensional data structure that can be flexibly retrieved by channel segment and condition. This allows subsequent safety filtering and path search to complete batch assessments of all conditions in one go, avoiding the risk of omissions from separate scenario-by-scenario analysis. Then, by generating a feasible interference safety subgraph by eliminating out-of-limit channel segments based on three hard constraints, a safety baseline is established before path search, ensuring that no path in the search space crosses out-of-limit channel segments. At the same time, connectivity verification and threshold relaxation backoff mechanisms ensure that feasible paths can still be found under strict constraints. By adding extreme condition interference penalty terms and ground loop amplification penalty terms to the multi-target labeling search, the former ensures sufficient safety margin for the preferred path under extreme conditions through a three-interval nonlinear penalty function, while the latter actively avoids the ground loop amplification effect from the perspective of the physical coupling mechanism of the shielding layer closed loop. The synergy of the two ensures that path decision-making not only focuses on the average interference level but also takes into account extreme risks. Finally, through a four-parameter driven dynamic weighting mechanism, the same system can adaptively adjust the weights of each dimension according to the interval voltage level, operating frequency, loop type, and protection priority. Critical protection loops automatically favor high anti-interference paths, while ordinary signal loops take into account path length under the premise of safety, avoiding the applicability limitations of fixed weighting schemes. Attached Figure Description

[0006] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a schematic diagram of a substation secondary cable network path optimization system based on topology in an embodiment of this application; Figure 2 This is a schematic diagram of the convergence curve of the number of Pareto labels as the number of nodes expands, according to an embodiment of this application. Detailed Implementation

[0007] This application provides a substation secondary cable network path optimization system based on topology. The terms "first," "second," "third," "fourth," etc. (if present) in the specification, claims, and accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein. Furthermore, the terms "comprising" or "having" and any variations thereof are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0008] For ease of understanding, the specific process of the embodiments of this application is described below. Please refer to [link / reference]. Figure 1 One embodiment of a substation secondary cable network path optimization system based on topology in this application includes: The attribute analysis unit is used to obtain the location information of signal transceiver equipment nodes, laying channel sections, grounding network nodes and high-voltage electrical equipment, and to construct a physical grounding attribute map that integrates channel physical attributes and grounding adjacency attributes.

[0009] Furthermore, a physical grounding attribute diagram is constructed that integrates the physical attributes of the channel and the grounding adjacency attributes, including: The length, number of bends, and cable volume ratio of the laying channel section are obtained and mapped to channel physical attributes. The topological connection relationship between the shielding grounding point and the grounding network connection point in the grounding network node is extracted and matched to the spatial coordinates of the laying channel section to generate grounding adjacency attributes.

[0010] The physical attributes of the channel and the grounding adjacency attributes are integrated into a weighted undirected graph. The node set of the weighted undirected graph includes signal transceiver device nodes and grounding network nodes. The edge set of the weighted undirected graph includes the laying channel segment and virtual edges representing grounding connection relationships. Each edge carries an attribute vector. The attribute vector is arranged in a fixed order, including the length value, the number of bends, the volume ratio value, the corresponding shielding layer grounding impedance value, and the adjacent grounding point number. A physical grounding attribute graph is generated based on the weighted undirected graph.

[0011] Specifically, signal transceiver nodes refer to the spatial locations of functional devices that transmit and receive electrical signals in the secondary system of a substation. These include terminal block access points of equipment such as protection and control devices, merging units, intelligent terminals, and remote communication cabinets. These nodes serve as the starting or ending points of cable laying during path optimization. A laying channel segment refers to an independent segment abstracted from the topology model of the physical path carrying secondary cables. Each channel segment corresponds to a continuous section in a cable trench, cable tunnel, cable tray, cable shaft, or conduit section, and is abstracted as an edge in the graph structure. Grounding network nodes include shielding grounding points, grounding flat iron connection points in cable trenches, equipment casing grounding terminals, and equipotential bonding points of the main grounding network. These nodes constitute the electrical connection interface between the cable shielding layer and the substation grounding system. The location information of high-voltage electrical equipment includes the spatial coordinates and orientations of primary equipment such as circuit breakers, disconnectors, voltage transformers, current transformers, main transformers, and busbars. These devices participate in interference assessment as sources of transient electromagnetic interference in subsequent steps.

[0012] Based on the aforementioned location information, the attribute analysis unit determines the channel's physical attributes and grounding adjacency attributes. The process for determining the channel's physical attributes is as follows: The length of each laying channel segment is measured using the station's 3D digital model or design drawings. The number of times each laying channel segment changes direction in the horizontal or vertical plane is counted as the number of bends. The ratio of the sum of the cross-sectional areas of currently laid cables in each channel segment to the effective cross-sectional area of ​​the channel is collected as the cable volume ratio. These three types of data are mapped to attributes attached to the corresponding channel segments, thus constituting the channel's physical attributes. The number of bends directly affects the cable's bending radius constraints and construction difficulty assessment, while the cable volume ratio reflects the remaining laying capacity of the channel.

[0013] The shielding layer of secondary cables is typically grounded at both ends. One end is connected to the equipotential copper busbar in the protection room, and the other end is connected to the grounding copper busbar in the local terminal box of the switchyard. These two grounding points are electrically connected through the main grounding grid. During topology extraction, each shielding layer grounding point is numbered and identified, and its connection path to the nearest grounding grid connection point is recorded. This connection path includes the cross-sectional area, material, and estimated power frequency impedance of the connecting conductor. Subsequently, the two ends of each laying channel segment are associated with the nearest grounding grid node to establish the affiliation relationship between the channel segment and the grounding loop, thereby generating the grounding adjacency attribute. The purpose of the grounding adjacency attribute is to locate the corresponding grounding branch based on the channel segment when calculating interference coupling, thereby assessing the contribution of shielding layer common impedance coupling to core wire interference.

[0014] Virtual edges are graph-theoretic edges that do not correspond to actual physical channels but reflect the electrical connection between two nodes in a grounding grid. Their function is to incorporate the topology of the grounding grid into the graph model, allowing the path search process to trace the closed loop formed by the shielding layer through the grounding grid. Each edge carries an attribute vector, which contains the length value, number of bends, volume ratio value, corresponding shielding layer grounding impedance value, and adjacent grounding point number in a fixed order. This fixed order of attribute vectors allows subsequent steps to directly read the required data by location index when accessing edge attributes, without needing to search by name. The shielding layer grounding impedance value is obtained from the grounding adjacency attribute, representing the impedance between the shielding layer grounding point corresponding to the channel segment and the grounding grid. This parameter is used as input when calculating the conducted interference component and the grounding loop amplification penalty term. The adjacent grounding point number is used to identify the nearest grounding grid nodes on both sides of the channel segment, providing spatial location information when analyzing the ground potential difference distribution of the shielding layer closed loop. Based on the complete definitions of the node set, edge set, and attribute vector, the weighted undirected graph is output as the physical grounding attribute graph.

[0015] The excitation analysis unit is used to calculate the spatial radiation attenuation coefficient and ground grid conduction attenuation coefficient of each channel segment by taking the location of high-voltage electrical equipment as the coordinate of the interference source and combining the grounding network impedance. The peak parameters of transient electromagnetic interference conditions and the two types of attenuation coefficients are then matrix-operated to generate a multi-condition transient excitation matrix.

[0016] Furthermore, the multi-condition transient excitation matrix is ​​generated, including: Short-circuit fault condition, lightning intrusion condition, and switch operation transient condition are identified as transient electromagnetic interference conditions. The peak parameters of the short-circuit fault condition are derived from short-circuit calculation software or relay protection setting calculation results. The peak parameters of the lightning intrusion condition are obtained from lightning protection calculations or statistical models based on daily thunderstorm data at the site. The peak parameters of the switch operation transient condition are derived from transient simulation of the opening and closing of the disconnecting switch or on-site measurements.

[0017] Based on the coordinates of the interference source and the impedance information of the grounding network nodes, the spatial radiation attenuation coefficient is calculated using the inverse square law of the near-field distance in free space. The grounding network conduction attenuation coefficient is calculated using the grounding network grid density, soil resistivity, and grounding conductor impedance. The spatial radiation excitation sub-matrix is ​​generated by multiplying the peak current parameters of each operating condition with the spatial radiation attenuation coefficient, and then correcting for the distance parameters from the interference source to each channel segment and the conductor geometry. The elements of the spatial radiation excitation sub-matrix are the transient magnetic field strengths of each channel segment under each operating condition. The grounding network conduction excitation sub-matrix is ​​generated by multiplying the peak current parameters of each operating condition with the grounding network conduction attenuation coefficient, and then correcting for the impedance distribution from the grounding network injection point to the corresponding grounding node of each channel segment. The elements of the grounding network conduction excitation sub-matrix are the ground potential differences of each channel segment under each operating condition. The spatial radiation excitation sub-matrix and the grounding network conduction excitation sub-matrix together constitute the multi-operating-condition transient excitation matrix.

[0018] Specifically, the coordinates of the interference source refer to the spatial location of primary equipment within the substation that may generate strong transient electromagnetic fields under abnormal operating conditions. These include circuit breakers, disconnect switches, voltage transformers, current transformers, main transformer bushings, and busbars. These devices generate high-amplitude, wide-spectrum transient currents during short-circuit faults, lightning strikes, or switching operations, becoming the primary source of electromagnetic interference for secondary cables. The reason the excitation analysis unit calculates these two types of attenuation coefficients separately rather than combining them into a single coefficient is that the physical mechanisms of spatial radiation attenuation and ground grid conduction attenuation are completely different. The former is the attenuation of electromagnetic fields propagating in air and soil, while the latter is the potential attenuation during the conduction of interference current along the ground grid conductor. Their attenuation laws and determining factors are entirely different. If they were combined into a single value during the matrix generation stage, the subsequent interference calculation unit would be unable to distinguish the contributions of spatial field interference and conducted interference, and therefore would be unable to calculate the two types of interference components separately.

[0019] The excitation analysis unit first identifies three transient electromagnetic interference (EMI) conditions as input scenarios for interference assessment. The short-circuit fault condition simulates the large current flowing through primary equipment when a three-phase short circuit or single-phase ground fault occurs inside the substation. Its peak parameters are derived from short-circuit calculation software or relay protection setting calculations, characterizing the maximum expected value of the short-circuit current and its decay time constant. The lightning intrusion condition simulates the situation where lightning strikes the substation's incoming line section or the lightning arrester trips, causing lightning surges to intrude into the substation. Its peak parameters are obtained from lightning protection calculations or statistical models based on daily thunderstorm data at the site, characterizing the current amplitude and waveform parameters of the intruding lightning surge. The switch operation transient condition simulates the high-frequency transient current generated by the repeated extinguishing of the arc between contacts during the opening and closing of the disconnector switch. Its peak parameters are derived from transient simulations of the disconnector switch opening and closing or actual field measurement data. The reason for including the three operating conditions in the evaluation framework is that the interference mechanisms and magnitudes of the different operating conditions are significantly different. Short circuit faults are mainly caused by the spatial magnetic field generated by the high-frequency current, lightning intrusion is mainly caused by the spatial radiation and ground potential rise generated by the high-frequency impulse current, and switching operation is mainly caused by ultra-fast transient pulses. If only a single operating condition is evaluated, high-risk channel segments in specific scenarios may be missed.

[0020] After determining the coordinates of the interference source and the peak parameters for the three operating conditions, the excitation analysis unit calculates the spatial radiation attenuation coefficient and the ground grid conduction attenuation coefficient, respectively. The spatial radiation attenuation coefficient is calculated based on the inverse square law of near-field distance in free space. This law states that the transient magnetic field strength generated by the interference source attenuates with the square of the propagation distance; the farther the channel segment is from the interference source, the weaker the direct magnetic field coupling it experiences. The excitation analysis unit measures the spatial distance from the midpoint of each channel segment to the coordinates of each interference source, takes the reciprocal of the square of this distance, and multiplies it by the near-field coefficient determined by the equivalent radius of the interference source conductor. This yields the spatial radiation attenuation coefficient for each channel segment corresponding to each interference source. This coefficient is a dimensionless proportional value, ranging from 0 to 1; a smaller value indicates greater attenuation of spatial radiation interference experienced by the channel segment. The ground grid conduction attenuation coefficient is calculated based on the grid density of the grounding grid, soil resistivity, and grounding conductor impedance. During short-circuit faults or lightning strikes, a large current injected into the grounding grid will generate a significant local ground potential rise near the injection point. This potential rise is conducted along the grounding grid conductor and gradually attenuates. The denser the grounding grid, the lower the soil resistivity, and the larger the cross-sectional area of ​​the grounding conductor, the faster the ground potential rise attenuates during conduction. Based on the location of each grounding network node in the physical grounding attribute diagram, the excitation analysis unit calculates the conduction path length and equivalent impedance from the grounding grid injection point corresponding to each interference source to the corresponding grounding node in each channel segment. Using an exponential decay model, it estimates the attenuation ratio of the ground potential rise along the conduction path, thus obtaining the grounding grid conduction attenuation coefficient.

[0021] After obtaining the two types of attenuation coefficients, the excitation analysis unit calculates the peak current parameters for each operating condition with the two types of attenuation coefficients, generating two independent sub-matrices. In the spatial radiation channel, the excitation analysis unit multiplies the peak current parameters for each operating condition with the spatial radiation attenuation coefficient of the corresponding channel segment to obtain the pre-attenuated current value. This current value is then multiplied by the distance parameters from the interference source to each channel segment and the magnetic field conversion coefficient determined by the conductor geometry. The magnetic field conversion coefficient is a physical coefficient that converts the current value into the magnetic field strength at the observation point, determined according to the Biot-Savart law. This coefficient depends on the geometry of the interference source conductor (such as the length of the busbar and its height above the ground) and the azimuth and distance of the observation point relative to the conductor. After this correction, the physical meaning of each element is transformed from the current value to the transient magnetic field strength experienced by each channel segment under each operating condition, measured in Tesla, thus generating the spatial radiation excitation sub-matrix. The rows of this sub-matrix correspond to the laying channel segments, and the columns correspond to each transient electromagnetic interference operating condition. Each element is a time-domain discrete sequence, representing the waveform of the magnetic field strength of the corresponding channel segment changing with time under the corresponding operating condition.

[0022] In the grounding grid conduction channel, the excitation analysis unit multiplies the peak current parameter of each operating condition with the grounding grid conduction attenuation coefficient of the corresponding channel segment to obtain the residual current value conducted to the corresponding grounding node of each channel segment after injection into the grounding grid. This residual current value is then multiplied by the equivalent impedance of the grounding grid from the injection point to the corresponding grounding node of each channel segment. Based on Ohm's law, multiplying the residual current by the impedance yields the ground potential rise at that grounding node. The difference in ground potential rise between two adjacent grounding nodes is the ground potential difference at both ends of the channel segment, expressed in volts. This generates the grounding grid conduction excitation sub-matrix. The rows of this sub-matrix correspond to the laying channel segments, and the columns correspond to each transient electromagnetic interference operating condition. Each element is also a time-domain discrete sequence, representing the waveform of the ground potential difference changing with time under the corresponding operating condition for the corresponding channel segment.

[0023] The space radiation excitation sub-matrix and the ground grid conduction excitation sub-matrix together constitute the multi-condition transient excitation matrix. This multi-condition transient excitation matrix is ​​no longer a single numerical matrix, but a dual-channel data structure composed of two sub-matrices with clearly defined physical meanings. The subsequent interference calculation unit extracts transient magnetic field strength data from the space radiation excitation sub-matrix and inputs it into the space field coupling model to calculate the space field interference component. It also extracts ground potential difference data from the ground grid conduction excitation sub-matrix and inputs it into the conduction coupling model to calculate the conducted interference component. The data sources and physical meanings of the two channels are mutually exclusive, enabling interference assessment to accurately distinguish between the two independent coupling paths: space radiation and ground grid conduction.

[0024] The interference calculation unit is used to calculate the spatial field interference component, conducted interference component, and core wire port interference voltage of each channel segment based on the physical grounding attribute diagram and the multi-condition transient excitation matrix, and splice them into a composite interference cost tensor.

[0025] Furthermore, the concatenation is performed into a composite interference cost tensor, which includes: The transient magnetic field strength of each channel segment is extracted from the spatial radiation excitation submatrix. The transient magnetic field strength is numerically differentiated to obtain the time change rate of magnetic field strength. The spatial field interference component is obtained by calculating the time change rate of magnetic field strength, the equivalent loop area of ​​the cable, and the shielding attenuation coefficient using the spatial field coupling model. The ground potential difference of each channel segment is extracted from the ground grid conduction excitation submatrix. The conduction interference component is obtained by calculating the amplitude of the ground potential difference, the grounding impedance of the shielding layer, and the transfer impedance using the conduction coupling model. The two interference components are superimposed in the time domain and corrected by common-mode to differential-mode conversion to obtain the core wire port interference voltage. The three types of interference quantities are organized into a composite interference cost tensor in three dimensions along the channel segment, operating condition, and component type according to the edge relationship of the physical grounding attribute diagram.

[0026] Specifically, the interference calculation unit calculates the spatial interference component, conducted interference component, and core wire port interference voltage of each channel segment based on the physical grounding attribute map constructed by the aforementioned attribute analysis unit and the multi-condition transient excitation matrix generated by the excitation analysis unit. It then organizes these three types of interference quantities into a composite interference cost tensor. The physical grounding attribute map is a weighted undirected graph with substation secondary cable channel segments as edges and equipment nodes as nodes. Its edge relationships record the topological connection structure between channel segments, and the attribute vectors attached to each edge include geometric and material parameters related to electromagnetic coupling, such as the cable equivalent loop area, shielding attenuation coefficient, shielding layer grounding impedance, and transfer impedance. The multi-condition transient excitation matrix is ​​generated by the excitation analysis unit and adopts a dual-channel structure, consisting of a spatial radiation excitation sub-matrix and a ground grid conducted excitation sub-matrix. Each element of the spatial radiation excitation sub-matrix represents the transient magnetic field strength of the corresponding channel segment under a specific operating condition, while each element of the ground grid conducted excitation sub-matrix represents the ground potential difference of the corresponding channel segment under the same operating condition.

[0027] The interference calculation unit first extracts the transient magnetic field strength B(t) of each channel segment under various operating conditions from the spatial radiation excitation sub-matrix. The transient magnetic field strength refers to the physical quantity directly output by the excitation analysis unit after matrix operations on the spatial radiation excitation sub-matrix during the duration of transient electromagnetic interference conditions such as lightning strikes and switching operations. Its dimension is Tesla (T), reflecting the change in magnetic field strength at the spatial location of the channel segment over time. Since the input to the subsequent spatial field coupling model is not the magnetic field strength itself, but rather the rate of change of the magnetic field strength over time, numerical differentiation is required on the extracted transient magnetic field strength. Numerical differentiation involves using discretization methods such as forward difference and central difference to divide the difference in magnetic field strength between two adjacent sampling moments in the discrete time series by the sampling time interval, calculating the time change rate of magnetic field strength dB / dt point by point. This conversion is necessary because Faraday's law of electromagnetic induction states that the induced electromotive force generated in a loop by a changing magnetic field depends on the time change rate of the magnetic flux, not the magnetic flux itself. Therefore, dB / dt is the direct driving force determining the magnitude of spatial radiation coupling interference.

[0028] After obtaining the time-varying rate of magnetic field strength, the interference calculation unit uses it as one of the input data for the spatial field coupling model. The spatial field coupling model is a physical calculation model describing the induced interference generated in the cable loop by transient magnetic fields through spatial radiation. Its input data includes three parameters: first, the time-varying rate of magnetic field strength (dB / dt) obtained through numerical differentiation; second, the equivalent loop area A of the cable read from the attribute vectors of each channel segment in the physical grounding attribute diagram; and third, the shielding attenuation coefficient S, also read from the attribute vectors. The equivalent loop area of ​​the cable refers to the equivalent loop area enclosed by the signal line and the return path of the secondary cable. The larger this area, the more magnetic flux passes through the loop, and the stronger the induced electromotive force. The shielding attenuation coefficient characterizes the attenuation capability of the cable shielding layer against spatially radiated magnetic fields; its value depends on the material, braiding density, and thickness of the shielding layer. The working principle of the spatial field coupling model is based on Faraday's law of electromagnetic induction. The calculation process of the spatial field interference component Vs is as follows: multiply the magnetic field strength time change rate dB / dt with the equivalent loop area A of the cable to obtain the unattenuated induced electromotive force, and then multiply it by the attenuation factor corresponding to the shielding attenuation coefficient S to obtain the spatial field interference component after shielding attenuation. The physical meaning of this component is the induced voltage generated on the cable core due to the radiation coupling of the spatial magnetic field.

[0029] While calculating the spatial field interference components, the interference calculation unit extracts the ground potential difference of each channel segment under various operating conditions from the ground grid conducted excitation submatrix in parallel. The ground potential difference refers to the potential difference between different grounding points on the substation grounding grid during transient operating conditions due to ground grid current dissipation. Its dimension is volts (V), reflecting the intensity of conducted electromagnetic interference in the grounding system. The extracted ground potential difference is then used as input data for the conducted coupling model. The conducted coupling model is a physical calculation model describing the conduction interference from the ground grid entering the cable core through the grounding wire and shielding layer. Its input data also includes three parameters: the aforementioned ground potential difference amplitude ΔVg, the shielding layer grounding impedance Zg read from the attribute vector, and the transfer impedance Zt in the attribute vector. The shielding layer grounding impedance refers to the connection impedance between the cable shielding layer and the grounding grid. The lower this impedance, the easier it is for the interference current on the ground grid to be discharged through the shielding layer. The transfer impedance is the proportionality coefficient of the induced voltage per unit length generated by the interference current flowing through the shielding layer in the internal core of the cable, characterizing the shielding layer's isolation capability against conducted interference. The working principle of the conducted coupling model is based on the circuit transmission line theory. The calculation process of the conducted interference component Vc is as follows: Under the combined action of the shielding layer grounding impedance and transfer impedance, the ground potential difference couples the interference current to the core wire through the grounding loop. Specifically, the amplitude of the ground potential difference is multiplied by the conducted coupling coefficient determined by the shielding layer grounding impedance and transfer impedance to obtain the conducted interference component. The physical meaning of this component is the interference voltage generated on the cable core wire due to the conducted coupling of the grounding grid.

[0030] After calculating the spatial interference component and the conducted interference component separately, the interference calculation unit performs time-domain superposition of the two interference components. Time-domain superposition refers to directly adding the spatial interference component and the conducted interference component at the same instant within the transient time window of each operating condition, obtaining the time-domain waveform of the total interference voltage of that channel segment under that operating condition. However, this total interference voltage exists in common-mode form between the core wire and ground, while the interference limit of concern to the secondary equipment port is defined in differential-mode form. Therefore, further common-mode to differential-mode conversion correction is required. Common-mode to differential-mode conversion correction refers to multiplying the common-mode interference voltage by the corresponding common-mode to differential-mode conversion coefficient according to the symmetry parameters and balance index of the cable, converting it into the differential-mode interference voltage actually experienced at the core wire port, i.e., the core wire port interference voltage. The physical basis of this conversion is that the actual cable loop is not ideally symmetrical, and common-mode interference will be partially converted into differential-mode interference under asymmetrical impedance distribution. The conversion ratio is determined by the balance characteristics of the cable.

[0031] Finally, the interference calculation unit organizes the three types of interference quantities—spatial field interference components, conducted interference components, and core wire port interference voltage—along three dimensions according to the edge relationships in the physical grounding attribute diagram: the first dimension is the channel segment dimension, corresponding to the labels of each edge in the physical grounding attribute diagram, reflecting the spatial distribution of interference quantities at different topological locations; the second dimension is the operating condition dimension, corresponding to the labels of each transient operating condition in the multi-operating condition transient excitation matrix, reflecting the temporal characteristics of interference quantities under different operating scenarios; the third dimension is the component type dimension, corresponding to three interference indicators with different physical meanings: spatial field interference, conducted interference, and port interference. The combination of these three dimensions forms a composite interference cost tensor. Each element of this tensor corresponds to the interference quantity value of a specific component type for a specific channel segment under a specific operating condition. Subsequent subgraph generation units and path search units will use this tensor to determine safety thresholds and calculate path costs.

[0032] The subgraph generation unit is used to generate a feasible interference safety subgraph by eliminating out-of-standard channel segments based on the composite interference cost tensor, according to the port interference voltage threshold, shielding current threshold, and volume ratio upper limit.

[0033] Furthermore, the process of eliminating out-of-standard channel segments based on the composite interference cost tensor includes: Iterate through the composite interference cost tensor, read the interference voltage values ​​under all operating conditions from the port interference voltage dimension for each channel segment, and take the maximum value as the predicted port interference voltage. Calculate the predicted shielding layer interference current from the conducted interference component dimension combined with the shielding layer grounding impedance. Obtain the sum of the current occupied volume ratio and the volume ratio of the cable to be laid for each channel segment as the predicted channel volume ratio.

[0034] The predicted port interference voltage is compared with the allowable port interference voltage threshold of the target signal loop, the predicted shielding layer interference current is compared with the allowable shielding layer interference current threshold, and the predicted channel volume ratio is compared with the upper limit of the channel volume ratio. If any one of these conditions is not met, a prohibition mark is set for the channel segment and it is removed from the physical grounding attribute diagram. After removal, it is checked whether there is a connected path between the source node and the target node. If not, the threshold relaxation mechanism is triggered. Under the premise of ensuring device safety, the allowable port interference voltage threshold is temporarily increased by a preset ratio or the prohibition channel segment is marked and shielding measures are added before re-evaluating its interference level until the connection between the source node and the target node is restored, and a feasible interference safety sub-graph is generated.

[0035] Specifically, the feasible interference safety subgraph refers to the substructure retained after removing the excessive channel segments from the original physical grounding attribute graph. This subgraph only includes channel segments that meet the interference safety constraints and channel capacity constraints under all evaluation conditions. Subsequent path searches are only performed on this subgraph, thus ensuring that no feasible path in the search space will traverse channel segments that do not meet the safety standards. The physical meanings of the three hard constraints are different: the port interference voltage threshold is the maximum common-mode interference voltage that the port of the protection device or measuring equipment connected to the target signal loop can withstand. Exceeding this threshold may cause device malfunction or sampling distortion; the shielding current threshold is the maximum safe current that the shielding conductor is allowed to flow through for a long time. Exceeding this threshold will cause the shielding layer to overheat or even be damaged; the channel volume ratio limit is the maximum percentage of the cable cross-sectional area in the channel segment to the effective cross-sectional area of ​​the channel. Exceeding this limit means that the channel segment cannot accommodate any more cables.

[0036] The subgraph generation unit first traverses the composite interference cost tensor, extracting the predicted interference level from three dimensions for each channel segment. When extracting the predicted port interference voltage, the subgraph generation unit reads the port interference voltage values ​​under all operating conditions in the corresponding slice of the channel segment along the tensor's operating condition dimension, taking the maximum value as the predicted port interference voltage. The reason for taking the maximum value instead of the average is that the substation secondary system must remain safe throughout the entire operating cycle. Even if a certain extreme operating condition only occurs sporadically under specific conditions, as long as the interference voltage under that condition exceeds the threshold, there is an unacceptable risk to the cable laying along that channel segment. Therefore, the interference value under the most unfavorable operating condition must be used as the evaluation criterion. When extracting the predicted shielding layer interference current, the subgraph generation unit reads the conducted interference voltage data of the channel segment along the tensor's conducted interference component dimension. Combining this with the shielding layer grounding impedance recorded in the physical grounding attribute vector of the channel segment, the conducted interference voltage is divided by the total impedance of the shielding layer grounding loop using Ohm's law to convert it into the interference current flowing through the shielding layer, i.e., the predicted shielding layer interference current. When extracting the predicted channel volume ratio, the sub-graph generation unit obtains the current occupied volume ratio of the channel segment from the physical grounding attribute graph, and adds the ratio of the cross-sectional area of ​​the cable to be laid to the effective cross-sectional area of ​​the channel as the volume ratio of the cable to be laid. The sum of the two is the predicted channel volume ratio, which represents the total volume ratio level of the channel segment after accommodating the new cable.

[0037] After extracting the three types of predicted values, the subgraph generation unit compares the predicted port interference voltage with the allowable port interference voltage threshold of the target signal loop, the predicted shielding layer interference current with the allowable shielding layer interference current threshold, and the predicted channel volume ratio with the upper limit of the channel volume ratio. The three comparisons are performed one by one. If any one of them fails to meet the corresponding threshold condition, a prohibition mark is set for the channel segment, and it is removed from the physical grounding attribute graph. Setting a prohibition mark means writing a Boolean prohibition flag into the attribute vector of the channel segment. When the subsequent path search module detects this flag during node expansion, it skips the channel segment and does not include it in the candidate expansion edges. Removing it from the physical grounding attribute graph means removing the edge corresponding to the prohibited channel segment from the edge set of the graph, so that the generated new subgraph no longer contains the channel segment. The reason for using three independent judgments instead of a comprehensive weighted judgment is that excessive interference voltage, excessive shielding current, and insufficient channel capacity belong to two different types of constraints: electrical safety and physical space. There is no mutual compensation relationship between them. Even if the interference voltage just meets the threshold, if the channel volume ratio is full, the channel segment still cannot accommodate new cables and must be eliminated.

[0038] After completing the three comparisons and elimination operations for all channel segments, the subgraph generation unit checks whether a connected path exists between the source node and the target node in the feasible interference safety subgraph. The source node is the graph node corresponding to the starting point of the cable to be laid, i.e., the device access point of the signal transmitting end; the target node is the graph node corresponding to the ending point of the cable, i.e., the device access point of the signal receiving end. The connected path detection uses a breadth-first search or depth-first search algorithm, traversing all reachable nodes in the subgraph starting from the source node, and determining whether the target node is in the set of reachable nodes. If the target node is reachable, it means that after eliminating the out-of-limit channel segments, there is still at least one physical path from the source to the target, and the feasible interference safety subgraph is completed.

[0039] If the target node is unreachable, it indicates that the elimination operation was too strict, causing a loss of physical connectivity between the source and target nodes. In this case, the subgraph generation unit triggers a threshold relaxation mechanism to restore connectivity. The premise of the threshold relaxation mechanism is that, in engineering practice, the value of the interference threshold itself contains a certain safety margin. When all channel segments are eliminated due to excessive interference, the interference constraints can be appropriately relaxed while ensuring the basic safety of the device, allowing some channel segments that are close to the threshold but have not yet seriously exceeded it to return to the search space. The mechanism includes two operational paths: The first is to temporarily increase the permissible port interference voltage threshold by a preset ratio. That is, without exceeding the device damage limit, the threshold is multiplied by a relaxation factor greater than 1. The comparison process is then re-executed using this relaxed threshold, allowing passageways that were previously restricted due to slightly excessive interference voltage to be allowed again. The second is to mark and install shielding measures on the restricted passageways, such as adding a copper strip shielding layer within the passageway or changing the original shielding layer grounding point from single-end grounding to double-end grounding, to reduce the actual interference level of the passageway. After installation, the interference calculation unit is called back to evaluate the interference cost tensor slice of the passageway. If the evaluation result meets the relaxed threshold condition, the restriction mark is removed. These two operational paths can be used individually or in combination. The subgraph generation unit repeatedly performs relaxation and re-evaluation until connectivity between the source node and the target node is restored, thereby generating the final feasible interference safety subgraph and outputting it to the path search unit.

[0040] The path search unit is used to search for paths in the feasible interference safety subgraph, and to add extreme condition interference penalty terms and ground loop amplification penalty terms in the label update, and to generate a set of non-dominated candidate paths by filtering through Pareto dominance relations.

[0041] Further, a set of non-dominated candidate paths is generated through filtering, including: On the feasible interference safety subgraph, the path search labels are initialized with three-dimensional labels based on the cumulative values ​​of path length, interference voltage, and interference current. During the node expansion process, the extreme condition interference penalty term is calculated from the composite interference cost tensor, and the grounding loop amplification penalty term is calculated from the physical grounding attribute map and the multi-condition transient excitation matrix. The two penalty terms are added to the label update function, and the labels that are not fully dominated are retained by the Pareto dominance relation comparison to generate a set of non-dominated candidate paths.

[0042] Furthermore, the path search unit calculates the extreme condition disturbance penalty term as follows: For each extended path, the maximum port interference voltage of all channel segments on that path under all operating conditions is extracted from the composite interference cost tensor. The ratio of the maximum port interference voltage to the allowable port interference voltage threshold of the target signal loop is divided into three intervals. When the ratio is lower than the first preset ratio, the penalty weight is zero. When the ratio is between the first preset ratio and the second preset ratio, the penalty weight increases linearly. When the ratio exceeds the second preset ratio, the penalty weight increases sharply according to an exponential law. The first preset ratio is less than the second preset ratio and the second preset ratio is less than 1.

[0043] Furthermore, the path search unit calculates the ground loop amplification penalty term as follows: For the grounding point pair at both ends of the shielding layer on the extended path, the equivalent impedance of the closed loop formed by the grounding grid conductor between the grounding point pair is obtained from the physical grounding attribute diagram. The shielding layer circulating current is estimated by the ratio of the ground potential difference to the equivalent impedance. The product of the shielding layer circulating current and the transfer impedance from the shielding layer to the core wire is used as the grounding loop amplification penalty term.

[0044] Furthermore, during the update process of the path search labels, the number of non-dominated labels retained by each node is capped. When the number of non-dominated labels on a certain node exceeds the cap, edge labels are eliminated according to their distance from the allowable port interference voltage threshold in the dimension of extreme operating condition interference penalty term. Labels closer to the threshold are retained with priority.

[0045] Specifically, the path search label refers to a data structure attached to each extended node during the path search process, used to record the multi-dimensional cumulative cost of the extended path from the source node to the current node. The path search label in this invention includes three-dimensional cumulative values: path length cumulative value, interference voltage cumulative value, and interference current cumulative value. The path length cumulative value is the sum of the lengths of all traversed channel segments from the source node to the current node, reflecting the physical length cost of the path. The interference voltage cumulative value is the sum of the core wire port interference voltages of all channel segments from the source node to the current node, reflecting the overall level of electromagnetic interference experienced by the path. The interference current cumulative value is the sum of the shielding layer interference currents of all channel segments from the source node to the current node, reflecting the cumulative conducted interference experienced by the shielding layer along the path. The starting point of the path search is the source node; during initialization, all three-dimensional labels of this node are set to zero, indicating that no channel segments have been traversed yet.

[0046] The path search unit employs a multi-label shortest path search strategy. During node expansion, it starts from the current node and expands sequentially along the edges adjacent to that node in the feasible interference safety subgraph to the next node. During each expansion, the three-dimensional cost (length, port interference voltage, and shielding layer interference current) of the channel segment to be expanded is read from the composite interference cost tensor and superimposed on the current label. Simultaneously, two penalty terms are calculated and added to the label update function to form the updated label. The multi-label strategy means that, unlike conventional shortest path algorithms where each node retains only one optimal label, this invention allows each node to retain multiple non-dominant labels, each corresponding to a different path from the source node to that node. The purpose of this is to preserve diverse candidate paths under target conflict and avoid losing better-performing solutions in other dimensions due to optimization in a single dimension.

[0047] During node expansion, the path search unit calculates the extreme condition interference penalty and the ground loop amplification penalty. The extreme condition interference penalty is designed so that the cumulative interference voltage in the three-dimensional label reflects the sum of interference voltages of all channel segments on the path. However, the fact that the sum meets the standard does not mean that there are no individual channel segments on the path whose interference voltage is close to the threshold limit under specific operating conditions. The average interference level of a path may be very low, but if the interference voltage of a certain channel segment under the worst operating condition is close to the threshold, then the safety margin of that path under extreme events is extremely low. Therefore, the extreme condition interference penalty takes the maximum value of the port interference voltage of all channel segments on the expanded path under all operating conditions, and divides the ratio of the maximum port interference voltage to the allowable port interference voltage threshold of the target signal loop into three intervals to apply nonlinear penalties. When this ratio is lower than the first preset ratio, it means that the interference voltage under the worst operating condition is far below the threshold, the safety margin is sufficient, the penalty weight is zero, and no additional cost is incurred. When the ratio falls between the first and second preset ratios, the safety margin begins to decrease but still has some leeway. The penalty weight increases linearly, with the growth rate proportional to the ratio. When the ratio exceeds the second preset ratio, the safety margin becomes very limited, and the penalty weight increases sharply exponentially. This means that even if the interference voltage has not yet reached the threshold, the algorithm will exclude such paths from the preferred selection range at a very high penalty cost. The first preset ratio is less than the second preset ratio, and the second preset ratio is less than 1. These three intervals form a progressive gradient from "no penalty" to "linear warning" to "exponential exclusion," allowing path selection to achieve a reasonable trade-off between safety margin and other objectives such as path length.

[0048] The design intent of the ground loop amplification penalty term is that when the grounding points at both ends of the shielding layer on the path cross areas with large potential differences in the grounding grid, a significant circulating current will form in the closed loop formed by the shielding layer through the main grounding grid. This circulating current generates additional conducted interference on the core wire through the transfer impedance. This effect cannot be directly reflected in the conventional accumulation of three-dimensional labels because the accumulated interference current value of the labels only reflects the arithmetic superposition of the shielding layer currents in each channel segment, without considering the overall amplification effect of the shielding layer closed loop. Therefore, the ground loop amplification penalty term, for the grounding point pair at both ends of the shielding layer on the extended path, obtains the equivalent impedance of the closed loop formed between the grounding point pair through the grounding grid conductor from the physical grounding attribute diagram, and obtains the ground potential difference of the grounding point pair under each operating condition from the ground grid conducted excitation sub-matrix of the multi-condition transient excitation matrix. The shielding layer circulating current is estimated by the ratio of the ground potential difference to the equivalent impedance. This ratio is actually a direct application of Ohm's law: the larger the potential difference, the stronger the ability to drive the circulating current; the smaller the equivalent impedance, the lower the path resistance of the circulating current. The two together determine the amplitude of the circulating current. The product of the circulating current in the shielding layer and the transfer impedance from the shielding layer to the core wire is used as a ground loop amplification penalty term. Its physical meaning is the longitudinal interference voltage generated on the core wire by the circulating current through the transfer impedance. The higher the value of this penalty term, the more severe the ground loop amplification effect of this path. The algorithm will tend to avoid such paths in the label comparison.

[0049] The path search unit adds the two penalty terms mentioned above to the label update function. The label update function is defined as follows: each time a node is expanded, the three-dimensional cost of the new channel segment is superimposed onto the current label, and the extreme condition interference penalty and ground loop amplification penalty are added as additional penalty costs to the corresponding dimension of the label. The updated label reflects not only the conventional costs of the path (length, voltage, current) but also the additional risks of the path in the two dimensions of extreme condition safety margin and ground coupling amplification effect. The path search unit uses Pareto dominance comparison to screen labels. Pareto dominance means that in a multi-dimensional target space, if label A is not inferior to label B in all dimensions and is strictly superior to label B in at least one dimension, then label A is said to dominate label B. After each node expansion generates a new label, the path search unit compares the new label with each of the existing labels on that node using Pareto dominance: if the new label is completely dominated by one of the existing labels, it is discarded; if the new label dominates an existing label, the dominated existing label is removed; if the new label is not dominant to any of the existing labels, it is retained in the label set of that node. This full retention strategy ensures that diverse candidate paths under target conflict are not prematurely eliminated due to optimization in a single dimension. After all nodes have been expanded, the set of paths corresponding to all retained labels on the target node constitutes the set of non-dominated candidate paths.

[0050] During the update process of path search labels, the path search unit sets an upper limit on the number of non-dominated labels retained at each node. This upper limit is set because, in large substation scenarios, the feasible interference safety subgraph may contain hundreds of nodes and thousands of edges. A full Pareto label retention strategy, when the number of nodes is large, can lead to the accumulation of a large number of non-dominated labels on each node, resulting in combinatorial explosion and a sharp increase in the computational load for subsequent label comparisons. To control the computational scale, the path search unit performs a truncation operation when the number of non-dominated labels on a node exceeds the preset upper limit. The truncation strategy is as follows: labels are sorted according to their proximity to the allowable port interference voltage threshold in the dimension of the extreme operating condition interference penalty term. Labels closer to the threshold indicate that their interference voltage under the worst operating condition is closer to the safety limit, representing the candidate scheme with the thinnest safety margin. During truncation, these labels are retained first, while edge labels far from the threshold are discarded. The reason for this design is that although the paths represented by the labels close to the threshold have a high level of interference at present, there may be a better trade-off between the costs of each dimension. If they are eliminated too early, candidate solutions with engineering value will be lost. On the other hand, although the labels far from the threshold have sufficient safety margin, their length or other dimension costs may be poor, and they are unlikely to be selected in the weighted summation stage of the subsequent path decision module. Therefore, they are eliminated first when computing resources are limited.

[0051] For example, Figure 2 This diagram illustrates the convergence curve of the number of Pareto labels as the number of nodes expands. As can be seen from the curve, in the early stages of the search (when the number of node expansion steps is less than 40), the number of non-dominated labels increases approximately linearly with node expansion, reflecting a rapid increase in the diversity of the solution space. Once the number of labels reaches its upper limit, the actual number of retained labels stabilizes near this limit due to the truncation strategy, while the theoretically unlimited number of labels continues to grow to an even higher level (approximately 48).

[0052] The path decision unit is used to dynamically assign weights to the set of non-dominant candidate paths based on voltage level, circuit type, operating frequency, and protection priority, and then perform a weighted summation to determine the preferred path.

[0053] Furthermore, the process by which the path decision unit determines the optimal path includes: The target interval voltage level is multiplied by the operating frequency of adjacent switching equipment and mapped to the base value of the spatial field interference weight according to the preset normalization interval. The adjustment coefficients of the conducted interference weight and length weight are obtained by querying the preset weight mapping table according to the signal circuit type and protection priority. The weight mapping table uses the signal circuit type as the row index and the protection priority level as the column index. The higher the protection priority, the larger the adjustment coefficient of the conducted interference weight and the smaller the adjustment coefficient of the length weight. The spatial field interference weight, conducted interference weight and length weight are normalized so that their sum is 1. The total length, cumulative port interference voltage and cumulative shielding layer interference current of each path in the non-dominant candidate path set are weighted and summed with the corresponding normalized weights. The path with the minimum comprehensive cost is selected as the preferred path.

[0054] Specifically, the path decision unit takes the set of non-dominated candidate paths output by the path search unit as input. Based on four engineering parameters—target interval voltage level, signal loop type, frequency of operation of nearby switching equipment, and protection priority—it dynamically assigns weights to the candidate paths and performs a weighted summation. The path with the lowest overall cost is then selected as the preferred path. Dynamic weight assignment means that the weight values ​​are not fixed constants but are calculated in real-time based on the interval and loop characteristics served by the cable to be laid. This allows the same optimization system to adapt to the varying requirements of different intervals and loop types regarding path length and anti-interference capabilities. Each path in the non-dominated candidate path set is a non-dominated scheme retained by the path search unit after Pareto filtering. They each have advantages and disadvantages in length, interference voltage, and interference current. Their merits cannot be determined solely by a single dimension; therefore, a weighted summation is needed to merge the three-dimensional costs into a one-dimensional comprehensive cost for final ranking.

[0055] The path decision unit first determines the base value of the spatial interference weight. The spatial interference weight reflects the importance of the spatial interference level of the path in the comprehensive decision-making process. A higher weight indicates that the algorithm is more inclined to select paths with lower spatial interference, even if the path is not advantageous in length. The base value is determined by multiplying the target bay voltage level by the operating frequency of nearby switchgear, and then mapping this value to a preset normalized interval. The target bay voltage level refers to the rated voltage level of the primary bay served by the secondary equipment to which the cable to be laid is connected. A higher voltage level results in a larger primary current flowing through the bay during a fault, a stronger transient magnetic field, and a more severe threat of spatial interference to the secondary cable. Therefore, cables in high-voltage bays should be assigned a higher spatial interference weight. The operating frequency of nearby switchgear refers to the average annual number of operations of disconnectors and circuit breakers near the target bay. A higher operating frequency increases the probability of transient operating conditions during switchgear operation and increases the long-term cumulative risk of spatial interference. The reason for multiplying voltage level and operating frequency is that their contributions to the risk of spatial interference are multiplicative rather than additive. A high-voltage interval adjacent to a low-operation-frequency switching device may not necessarily have a higher risk of spatial interference than a medium-voltage interval with frequent operation. Multiplication can reasonably reflect this cross-influence. Mapping the product to a preset normalization interval linearly transforms the product value from its original numerical range to a preset weighted interval, ensuring that the base value falls within a reasonable range that facilitates subsequent normalization processing.

[0056] After determining the base value for spatial interference weight, the path decision unit queries a preset weight mapping table based on the signal loop type and protection priority to obtain the adjustment coefficients for conducted interference weight and length weight. Signal loop type refers to the classification of the electrical characteristics of the signals transmitted by the cable to be laid, including DC tripping loops, AC analog sampling loops, digital input loops, Ethernet communication loops, and time synchronization loops. Different loop types have different sensitivities to interference. DC tripping loops, when subjected to conducted interference, may cause the protection device to trip erroneously, with the most serious consequences; therefore, they should be assigned a higher conducted interference weight. Ethernet communication loops use digital transmission and differential signals, have strong anti-interference capabilities, but are more sensitive to path length; therefore, they should be assigned a higher length weight. Protection priority refers to the importance level of the loop in the substation protection system, usually divided into four levels: extremely high, high, medium, and low. Tripping loops and protection sampling loops have the highest priority, while ordinary measurement loops and auxiliary signal loops have lower priority. The weight mapping table uses signal loop type as the row index and protection priority level as the column index. Each cell in the table stores a set of conducted interference weight adjustment coefficients and length weight adjustment coefficients. The higher the protection priority, the larger the adjustment coefficient for conducted interference weight, because interference to high-priority circuits directly affects power grid security, and their anti-interference performance must be prioritized. Conversely, the higher the protection priority, the smaller the adjustment coefficient for length weight, because the laying path of critical circuits should not sacrifice anti-interference capability in pursuit of shorter distances. The design of obtaining adjustment coefficients through table lookup rather than directly assigning absolute weight values ​​makes the weighting system scalable. When adding new circuit types or adjusting priority divisions, only the mapping table needs to be updated without modifying the algorithm logic.

[0057] After obtaining the values ​​of the three types of weights, the path decision unit normalizes the spatial field interference weight, the conducted interference weight, and the length weight so that their sum is 1. The purpose of normalization is to eliminate the imbalance in magnitude caused by the different dimensions and numerical ranges of the three types of weights, ensuring that the proportion of the three types of costs in the overall score during weighted summation is consistent with the physical meaning of the weights themselves. The normalization operation involves dividing each weight value by the sum of the three types of weights; after normalization, the sum of the three values ​​is exactly equal to 1.

[0058] After normalization, the path decision unit calculates the comprehensive cost for each path in the non-dominated candidate path set. The comprehensive cost of each path equals the total length of the path multiplied by the normalized length weight, plus the accumulated port interference voltage multiplied by the normalized spatial field interference weight, plus the accumulated shielding layer interference current multiplied by the normalized conducted interference weight. The sum of these three weighted values ​​is the comprehensive cost of the path. The smaller the comprehensive cost, the better the overall performance of the path under the current weight configuration. The path decision unit traverses all paths in the non-dominated candidate path set, calculates the comprehensive cost for each path, and selects the path with the smallest comprehensive cost as the preferred path output. Thus, a complete technical link closed loop is formed, from attribute graph construction, excitation matrix generation, interference cost calculation, safety subgraph filtering, multi-objective path search to dynamic weight decision. The final output preferred path is the optimal laying path determined by adaptively balancing length and anti-interference performance based on the characteristics of the target signal loop, under the premise of meeting electromagnetic interference safety constraints.

[0059] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0060] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0061] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A substation secondary cable network path optimization system based on topology, characterized in that, The system includes: The attribute analysis unit is used to obtain the location information of signal transceiver equipment nodes, laying channel sections, grounding network nodes and high-voltage electrical equipment, and to construct a physical grounding attribute map that integrates channel physical attributes and grounding adjacency attributes. The excitation analysis unit is used to calculate the spatial radiation attenuation coefficient and ground grid conduction attenuation coefficient of each channel segment by taking the location of high-voltage electrical equipment as the coordinate of the interference source and combining the grounding network impedance. The peak parameters of transient electromagnetic interference conditions and the two types of attenuation coefficients are matrix-operated to generate a multi-condition transient excitation matrix. The generation of multi-condition transient excitation matrices includes: The short-circuit fault condition, lightning intrusion condition, and switch operation transient condition are identified as the transient electromagnetic interference condition. Based on the coordinates of the interference source and the impedance information of the grounding network nodes, the spatial radiation attenuation coefficient is calculated using the inverse square law of near-field distance in free space. The grounding network conduction attenuation coefficient is calculated using the grounding network grid density, soil resistivity, and grounding conductor impedance. A spatial radiation excitation sub-matrix is ​​generated by multiplying the peak current parameters of each operating condition with the spatial radiation attenuation coefficient, and then correcting for the distance parameters from the interference source to each channel segment and the conductor geometry. The elements of the spatial radiation excitation sub-matrix are the transient magnetic field strengths of each channel segment under each operating condition. A grounding network conduction excitation sub-matrix is ​​generated by multiplying the peak current parameters of each operating condition with the grounding network conduction attenuation coefficient, and then correcting for the impedance distribution from the grounding network injection point to the corresponding grounding node of each channel segment. The elements of the grounding network conduction excitation sub-matrix are the ground potential differences of each channel segment under each operating condition. The spatial radiation excitation sub-matrix and the grounding network conduction excitation sub-matrix together constitute the multi-operating-condition transient excitation matrix. The interference calculation unit is used to calculate the spatial field interference component, conducted interference component and core wire port interference voltage of each channel segment according to the physical grounding attribute diagram and the multi-condition transient excitation matrix, and splice them into a composite interference cost tensor. The subgraph generation unit is used to generate a feasible interference safety subgraph by eliminating excessive channel segments based on the composite interference cost tensor, according to the port interference voltage threshold, shielding layer current threshold and volume ratio upper limit. The path search unit is used to search for paths in the feasible interference safety subgraph, add extreme condition interference penalty terms and ground loop amplification penalty terms in the label update, and generate a set of non-dominated candidate paths by filtering through Pareto dominance relations. The path search unit calculates the extreme condition interference penalty term as follows: for each extended path, it extracts the maximum port interference voltage of all channel segments under all conditions from the composite interference cost tensor, divides the ratio of the maximum port interference voltage to the allowable port interference voltage threshold of the target signal loop into three intervals, and when the ratio is lower than the first preset ratio, the penalty weight is zero; when the ratio is between the first preset ratio and the second preset ratio, the penalty weight increases linearly; when the ratio exceeds the second preset ratio, the penalty weight increases sharply according to an exponential law, wherein the first preset ratio is less than the second preset ratio and the second preset ratio is less than 1; The path search unit calculates the ground loop amplification penalty term as follows: for the grounding point pair at both ends of the shielding layer on the extended path, the equivalent impedance of the closed loop formed by the grounding grid conductor between the grounding point pair is obtained from the physical grounding attribute diagram. The shielding layer circulating current is estimated by the ratio of the ground potential difference to the equivalent impedance. The product of the shielding layer circulating current and the transfer impedance from the shielding layer to the core wire is used as the ground loop amplification penalty term. The set of non-dominated candidate paths is generated through filtering, including: On the feasible interference safety subgraph, the path search labels are initialized with three-dimensional labels based on the cumulative values ​​of path length, interference voltage, and interference current. During the node expansion process, the extreme condition interference penalty term is calculated from the composite interference cost tensor, and the grounding loop amplification penalty term is calculated based on the physical grounding attribute graph and the multi-condition transient excitation matrix. The two penalty terms are appended to the label update function, and the labels that are not fully dominated are retained by the Pareto dominance relation comparison to generate the non-dominated candidate path set. The path decision unit is used to dynamically assign weights to the set of non-dominant candidate paths based on voltage level, circuit type, operating frequency, and protection priority, and then perform a weighted summation to determine the preferred path.

2. The system according to claim 1, characterized in that, The attribute analysis unit is used to construct a physical grounding attribute map that integrates the physical attributes of the fusion channel and the grounding adjacency attributes, including: The length data, number of bends data, and cable volume ratio data of the laying channel section are obtained and mapped to the physical attributes of the channel. The topological connection relationship between the shielding grounding point and the grounding network connection point in the grounding network node is extracted, and the topological connection relationship is matched to the spatial coordinates of the laying channel section to generate the grounding adjacency attribute. The physical attributes of the channel and the grounding adjacency attributes are fused into a weighted undirected graph. The node set of the weighted undirected graph includes the signal transceiver device nodes and the grounding network nodes. The edge set of the weighted undirected graph includes the laying channel segment and virtual edges representing grounding connection relationships. Each edge carries an attribute vector. The attribute vector is arranged in a fixed order, including length value, number of bends value, volume ratio value, corresponding shielding layer grounding impedance value, and adjacent grounding point number. The physical grounding attribute graph is generated based on the weighted undirected graph.

3. The system according to claim 1, characterized in that, The interference calculation unit, used to concatenate the data into a composite interference cost tensor, includes: The transient magnetic field strength of each channel segment is extracted from the spatial radiation excitation sub-matrix. The transient magnetic field strength is numerically differentiated to obtain the magnetic field strength time change rate. The spatial field interference component is obtained by calculating the magnetic field strength time change rate, the cable equivalent loop area, and the shielding attenuation coefficient using a spatial field coupling model. The ground potential difference of each channel segment is extracted from the ground grid conduction excitation sub-matrix. The conduction interference component is obtained by calculating the ground potential difference amplitude, the shielding layer grounding impedance, and the transfer impedance using a conduction coupling model. The two interference components are superimposed in the time domain and corrected by common-mode to differential-mode conversion to obtain the core wire port interference voltage. The three types of interference quantities are three-dimensionally organized into the composite interference cost tensor along the channel segment, operating condition, and component type according to the edge relationship of the physical grounding attribute diagram.

4. The system according to claim 1, characterized in that, The subgraph generation unit, based on the composite interference cost tensor, removes out-of-range channel segments as follows: Iterate through the composite interference cost tensor, read the interference voltage values ​​under all operating conditions from the port interference voltage dimension for each channel segment and take the maximum value as the predicted port interference voltage. Calculate the predicted shielding layer interference current from the conducted interference component dimension combined with the shielding layer grounding impedance. Obtain the sum of the current occupied volume ratio and the volume ratio of the cable to be laid for each channel segment as the predicted channel volume ratio. The predicted port interference voltage is compared with the allowable port interference voltage threshold of the target signal loop, the predicted shielding layer interference current is compared with the allowable shielding layer interference current threshold, and the predicted channel volume ratio is compared with the upper limit of the channel volume ratio. If any one of these conditions is not met, a prohibition mark is set for the channel segment and it is removed from the physical grounding attribute diagram. After removal, it is checked whether there is a connection path between the source node and the target node. If not, a threshold relaxation mechanism is triggered. Under the premise of ensuring device safety, the allowable port interference voltage threshold is temporarily increased by a preset ratio or the prohibition channel segment is marked and shielding measures are added before re-evaluating its interference level until the connection between the source node and the target node is restored, and the feasible interference safety sub-graph is generated.

5. The system according to claim 1, characterized in that, During the update process of the path search labels, the number of non-dominated labels retained by each node is capped. When the number of non-dominated labels on a certain node exceeds the cap, edge labels are removed according to their distance from the allowable port interference voltage threshold in the dimension of the extreme operating condition interference penalty item. Labels closer to the threshold are retained with priority.

6. The system according to claim 1, characterized in that, The process by which the path decision unit determines the optimal path includes: The target interval voltage level is multiplied by the operating frequency of the adjacent switching equipment and mapped to the basic value of the spatial field interference weight according to the preset normalization interval. The adjustment coefficients of the conducted interference weight and length weight are obtained by querying the preset weight mapping table according to the signal circuit type and protection priority. The spatial field interference weight, the conducted interference weight, and the length weight are normalized so that their corresponding sums are 1. The total length, cumulative port interference voltage, and cumulative shielding layer interference current of each path in the non-dominated candidate path set are weighted and summed with their corresponding normalized weights. The path with the minimum overall cost is selected as the preferred path.

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