Creepage distance checking method for low-voltage power distribution system

Abstract

The invention belongs to the technical field of power systems, and discloses a creepage distance checking method for a low-voltage power distribution system. The method comprises the following steps: establishing a creepage distance rule knowledge base based on a creepage distance standard, identifying an electrified body, a grounding body and an insulated isolation surface between the electrified body and the grounding body in combination with a three-dimensional structure model of a low-voltage power distribution system, constructing an electrified body-insulated isolation surface-grounding body electrical topological relation, and calculating the shortest creepage path length of candidate discharge starting point and end point pairs; determining a target minimum creepage distance threshold from the rule knowledge base according to operation conditions such as pollution levels, altitudes and material characteristics; and parameters such as insulation part forming shrinkage, assembly tolerance and installation offset are introduced to correct the along-surface path length, an equivalent creepage distance is obtained and compared with a target minimum creepage distance threshold value, whether creepage is qualified or not and a creepage weak area is determined, and a basis is provided for design and checking of a low-voltage power distribution system.

Description

Technical Field

[0001] This invention belongs to the field of power system technology, specifically a method for verifying creepage distance in low-voltage power distribution systems. Background Technology

[0002] In low-voltage power distribution systems, the creepage distances between busbars, terminals, and switching devices must meet the requirements of relevant national and IEC standards. The minimum creepage distance is usually determined based on parameters such as rated insulation voltage, pollution degree, overvoltage category, and insulation material group or tracking index. In engineering design, two-dimensional layout diagrams are often used to estimate the phase-to-phase and phase-to-ground distances based on the projected dimensions. Alternatively, on a simplified geometric model, several key cross-sections are measured to determine whether the standard limits are met. For distribution cabinets and boxes with complex insulation structures such as creepage ribs, grooves, reinforcing ribs, and partitions, the actual surface creepage path often bypasses multiple insulation feature surfaces and is also affected by structures such as metal shielding, mounting holes, and ventilation holes. There is a deviation between the actual usable creepage path and the two-dimensional dimensions. Current practices usually only select some typical locations for inspection based on experience, and the creepage weakness areas formed by local three-dimensional layouts are not easily detected in the design stage.

[0003] The operating environment also has a significant impact on creepage distance. Changes in pollution level, altitude, temperature rise, and humidity can alter the electrical stress conditions on the surface of insulation components. Relevant standards provide correction rules for creepage distance under different environments. However, in engineering practice, to simplify calculations, many cases still use a single benchmark creepage distance for verification, rarely incorporating voltage level, material properties, and environmental corrections within a unified framework. On the other hand, manufacturing and assembly deviations such as insulation component forming shrinkage, busbar and terminal assembly tolerances, and isolator installation offsets are usually considered separately in process control documents, making it difficult to directly reflect these deviations in the creepage distance verification results in a quantitative manner. The combination of these factors makes the creepage distance verification work of complex low-voltage power distribution systems heavily reliant on manual experience. The level of detail in the verification process is greatly affected by individual judgment, and areas with insufficient creepage margin are not easily exposed at the drawing stage, potentially increasing the difficulty of later rectification and operational risks. Summary of the Invention

[0004] The purpose of this invention is to provide a method for verifying creepage distance in low-voltage power distribution systems, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for verifying creepage distance in a low-voltage power distribution system. This invention utilizes a three-dimensional structural model of the low-voltage power distribution system and relevant standard clauses regarding creepage distance to construct a complete quantitative verification process. First, clauses related to creepage distance are extracted from relevant national or industry standards. The clauses concerning rated insulation voltage, pollution level, overvoltage category, insulation material group, or tracking resistance index, along with corresponding correction rules, are organized into a unified data structure to establish a creepage distance rule knowledge base, used to determine the corresponding creepage distance requirements under different operating conditions. Combining the three-dimensional structural model of the low-voltage power distribution system to be verified, conductor components in the operating state are identified as live bodies in the model, and metal components electrically connected to the protective grounding terminal are identified as grounding bodies. The surfaces of solid insulating components located between live bodies and grounding bodies or between different live bodies are extracted to establish the electrical topology relationship between live body, insulating isolation surface, and grounding body. Based on this, the phase-to-phase live body pairs and live body-to-ground pairs that require creepage verification are determined. Based on this, the present invention introduces creepage propagation semantic annotation on the insulating surface. The area located on the outer surface of the creepage rib is marked as the creepage rib boundary, the bottom or side wall of the groove is marked as the groove boundary, the edge of the reinforcing rib is marked as the reinforcing rib boundary, the free edge of the partition is marked as the partition edge boundary, the insulating surface adjacent to the metal shield is marked as the shield boundary, and the area that is blocked by the metal part or directly connected to the outside air and does not form a surface creepage path is marked as the non-surface propagation boundary. The shield boundary and the non-surface propagation boundary are used as the limiting boundary of the surface path. According to the semantic annotation results, the insulating surface is discretized to generate surface nodes. A surface reachability graph is established according to whether the connection between adjacent nodes completely falls on the insulating surface and whether it crosses the limiting boundary. Each candidate discharge start point and end point pair is mapped to the start node and end node in the graph. A weighted shortest path search is performed according to the geometric distance between adjacent nodes to obtain the actual shortest surface creepage path and its path length between each candidate pair along the insulating surface, which is used to replace the verification method based only on straight distance or simple path assumption. After obtaining the surface path, this invention combines operating environment and condition parameters with a rule knowledge base to determine the corresponding creepage distance requirements. The operating environment and condition parameters include pollution level, altitude, temperature rise range, and humidity range. Using these parameters, along with the system's rated insulation voltage, overvoltage category, material group, or tracking resistance index, the invention retrieves rules that meet the conditions from the creepage distance rule knowledge base, determines the baseline creepage distance, and performs altitude correction, thermal and damp aging correction, and material tracking resistance attenuation correction in the order preset in the rules, thereby obtaining the minimum creepage distance threshold required under the target operating conditions. Simultaneously, based on the manufacturing and assembly parameters of each component in the structural model, the molding shrinkage of the insulation component, the assembly tolerance of the busbar or terminal, and the installation offset of the isolator are determined respectively. The above deviations are decomposed along the direction of the actual shortest surface creepage path, converted into a length compensation amount along the path direction, and algebraically summed with the actual shortest surface creepage path length in the direction unfavorable to the creepage distance to obtain the equivalent actual creepage distance after considering manufacturing and assembly deviations. This invention further compares the equivalent actual creepage distance with the target minimum creepage distance threshold one by one. Candidate discharge start and end point pairs with an equivalent actual creepage distance greater than or equal to the threshold are considered qualified creepage objects, while those with an equivalent actual creepage distance less than the threshold are considered unqualified creepage objects. The corresponding actual shortest surface creepage path is retained. For unqualified objects, the actual shortest surface creepage path is projected onto a three-dimensional structural model to obtain the insulating surface area traversed by the path. This area is recorded as a creepage weak zone, and the difference between the target minimum creepage distance threshold and the equivalent actual creepage distance is used as the basis for calculation. Identify the deficiencies in the weak area; based on the semantic category of the weak creepage area, select the structural adjustment scheme corresponding to the semantic category from the preset rectification strategy table to form targeted structural adjustment suggestions, such as adding creepage ribs or isolation ribs in specific areas, adjusting the phase-to-phase or phase-to-ground layout, adding insulation partitions, or upgrading the material group; combine the comparison results of each candidate discharge start point and end point pair, the actual shortest surface creepage path, the correction and compensation process, the location of the weak creepage area, and the corresponding structural adjustment suggestions to generate a report for creepage distance verification of the low-voltage power distribution system, providing a basis for subsequent design adjustments and defect rectification.

[0006] Furthermore, to adapt to the creepage distance verification requirements under different operating conditions, a creepage distance rule knowledge base for low-voltage power distribution systems is pre-established. Specifically, clauses related to creepage distance are extracted from national or industry standards, and each rule is organized into a unified data structure. Each rule records fields such as rated insulation voltage range, pollution level, overvoltage category, insulation material group or tracking resistance index range, benchmark creepage distance, and correction item type corresponding to the benchmark creepage distance, so that creepage distance requirements from different standards can be queried and called in the same format. Based on this, an applicable object identifier is set for each rule in the data structure to indicate that the rule applies to phase-to-phase live pairs or live-to-ground pairs in low-voltage power distribution systems. An applicable condition field and a decision priority field are also set. The applicable condition field limits the combination range of the rated insulation voltage range, pollution level, overvoltage category, and material group or tracking resistance index range corresponding to the rule. The decision priority field is used to determine the benchmark creepage distance and corresponding correction items when multiple rules meet the applicable conditions at the same time. The creepage distance rule knowledge base established in the above manner can retrieve the rules that meet the conditions according to the operating environment and system parameters during the subsequent verification process, and determine the specific creepage distance requirements and correction order based on the decision priority field.

[0007] Furthermore, the structural information required for creepage distance verification comes from the three-dimensional design model of the low-voltage distribution cabinet or distribution box. Specifically, the geometric information and position information of the enclosure, switching devices, busbars, terminal blocks, and insulating supports in the three-dimensional coordinate system are read from the three-dimensional design model. In this model, conductors that are energized under rated operating conditions are marked as live bodies, metal components electrically connected to the protective grounding terminal are marked as grounding bodies, and the surfaces of solid insulating components located between live bodies and grounding bodies or between different live bodies are marked as insulating isolation surfaces. Through the above markings, conductors at different potentials and surfaces that bear the surface insulation function can be distinguished in the same three-dimensional model, providing a structural basis for subsequent calculation of surface paths. After marking is completed, based on the relative positional relationship between the charged body and the insulating isolation surface, and between the insulating isolation surface and the grounding body in three-dimensional space, an electrical topology relationship between the charged body, the insulating isolation surface, and the grounding body is established. In this topology relationship, pairs of charged bodies or pairs of charged bodies and grounding bodies that are isolated from each other by the same insulating isolation surface and have a potential difference under rated operating conditions are selected as candidate discharge start and end point pairs that need to be checked for creepage. The candidate discharge start and end point pairs obtained in this way correspond to the three-dimensional layout and potential distribution of the low-voltage power distribution system and can be used as the set of start and end objects when solving the surface creepage path.

[0008] Furthermore, to reflect the influence of different geometric features on creepage propagation in the surface path calculation, the aforementioned insulating surface is divided into regions and semantically labeled for creepage propagation. Specifically, the region located on the outer surface of the creepage rib is marked as the creepage rib boundary, the region at the bottom of the groove or the side wall of the groove is marked as the groove boundary, the region where the edge of the reinforcing rib is located is marked as the reinforcing rib boundary, and the region where the free edge of the partition is located is marked as the partition edge boundary; the insulating surface region adjacent to the metal shield is marked as the shield boundary, and the region that is blocked by the metal component or directly connected to the outside air and does not form a surface creepage path in the structural design is marked as a non-surface propagation boundary; through the above labeling, the regions suitable as surface creepage paths and the regions that need to restrict creepage propagation can be distinguished in the 3D model, providing basic data for the subsequent construction of the surface reachability map; When constructing a surface reachability map and searching for the actual shortest surface creepage path, the areas marked as shield boundaries and non-surface propagation boundaries are used as restricted areas for surface paths. Surface reachability edges are not established between these areas in the surface reachability map, and paths are not allowed to cross these areas. As a result, the surface reachability map only establishes connectivity within the surface-propagation areas of the insulating surface. The actual shortest surface creepage path is limited to physically possible surface paths, avoiding the inclusion of shielded areas, ventilation openings, and other areas that do not participate in creepage in the path length.

[0009] Furthermore, after completing the semantic annotation of creepage propagation on the insulating surface, the insulating surface is discretized and a surface reachability graph is constructed to calculate the actual shortest creepage path along the surface. Specifically, multiple surface nodes located on the insulating material are generated on the insulating surface at predetermined intervals, and the spatial position of each surface node in the three-dimensional coordinate system is recorded. Subsequently, based on whether the geometric connection between two adjacent surface nodes completely falls on the insulating surface and whether it crosses the shield boundary or the non-creeping boundary, the surface reachability edge that can be established between the adjacent nodes is determined. Only when the geometric connection is located on the insulating surface and does not cross the limiting boundary is a surface reachability edge established between the corresponding surface nodes. Thus, a surface reachability graph composed of surface nodes and surface reachability edges is obtained, which transforms the continuous insulating surface into a graph structure suitable for path search. After obtaining the surface reachability graph, the spatial positions of each candidate discharge start-point and end-point pair in the three-dimensional coordinate system are mapped to the surface nodes with the smallest Euclidean distance in the surface reachability graph, which serve as the start and end nodes of the candidate discharge start-point and end-point pair. In the surface reachability graph, the geometric distance between adjacent surface nodes is used as the edge weight, and the shortest path search algorithm is used to find the actual shortest surface creepage path between the start and end nodes along the insulating isolation surface. The sum of the geometric distances of all surface reachable edges on the shortest path is used as the actual shortest surface creepage path length of the candidate discharge start-point and end-point pair. Through the above steps, a unified graph model under semantic annotation and boundary constraints is formed, which can be used to quantitatively characterize surface creepage paths on complex insulating surfaces.

[0010] Furthermore, by combining the operating environment and operating condition parameters with the creepage distance rule knowledge base, the target minimum creepage distance threshold for verification is determined. Specifically, the operating environment and operating condition parameters of the low-voltage power distribution system to be verified are first collected. These parameters include pollution level, altitude, temperature rise range, and humidity range. The above parameters, along with the rated insulation voltage, overvoltage category, and material group or tracking resistance index range of the low-voltage power distribution system, are input into the creepage distance rule knowledge base as query conditions. In the creepage distance rule knowledge base, a set of rules that matches the rated insulation voltage, pollution level, overvoltage category, and material group or tracking resistance index range, and is applicable to the altitude, temperature rise range, and humidity range, is retrieved. Based on the pre-set decision priority field of each rule, a benchmark rule is selected from the rule set, and the benchmark creepage distance recorded in the benchmark rule is read as the benchmark creepage distance. Subsequently, based on the correction order field recorded in the benchmark rule, the altitude correction, heat and humidity aging correction, and material tracking resistance attenuation correction are calculated in sequence, and each correction is superimposed with the benchmark creepage distance to obtain the target minimum creepage distance threshold corresponding to the current operating environment and conditions, which is used for comparison with the equivalent actual creepage distance.

[0011] Furthermore, in order to reflect the impact of manufacturing and assembly deviations in the creepage distance verification, the actual shortest surface creepage path length is converted into an equivalent actual creepage distance. Specifically, based on the manufacturing and assembly parameters of each component in the low-voltage power distribution system structural model, the molding shrinkage of the insulation component, the assembly tolerance of the busbar or terminal, and the installation offset of the isolator are determined respectively to characterize the geometric deviation of the physical product relative to the design model. Subsequently, the molding shrinkage, assembly tolerance, and installation offset are decomposed along the path direction of the aforementioned actual shortest surface creepage path to obtain the length compensation amount along the actual shortest surface creepage path direction. After obtaining the length compensation, each length compensation is taken in the direction that is unfavorable to the surface creepage distance, and then algebraically summed with the actual shortest surface creepage path length. The result is used as the equivalent actual creepage distance of the corresponding candidate discharge start and end point pair. The equivalent actual creepage distance obtained in this way is based on the surface creepage path length under the ideal three-dimensional structure, and also incorporates the creepage distance reduction introduced by molding shrinkage, assembly tolerance and installation offset in numerical terms. This is used to more closely approximate the actual creepage margin of the finished equipment under the installation state in subsequent verification.

[0012] Furthermore, the comparison and verification results of the equivalent actual creepage distance and the target minimum creepage distance threshold are specifically output as follows: For each candidate discharge start point and end point pair, the calculated equivalent actual creepage distance is compared with the corresponding target minimum creepage distance threshold. When the equivalent actual creepage distance is greater than or equal to the target minimum creepage distance threshold, the candidate discharge start point and end point pair is recorded as a qualified creepage object; when the equivalent actual creepage distance is less than the target minimum creepage distance threshold, the candidate discharge start point and end point pair is recorded as a unqualified creepage object, and the actual shortest surface creepage path corresponding to the candidate pair is saved. For candidate discharge start-point and end-point pairs marked as non-compliant creepage, their actual shortest surface creepage path is projected onto a 3D structural model to obtain the insulation isolation surface area traversed by the path in the model, and this area is recorded as a creepage weak zone. The difference between the target minimum creepage distance threshold and the equivalent actual creepage distance is taken as the insufficient creepage distance of the creepage weak zone. According to the category of the creepage weak zone in the aforementioned semantic annotation, the structural adjustment scheme corresponding to the semantic category is retrieved from the preset rectification strategy table to form a structural adjustment suggestion for the creepage weak zone. Subsequently, the comparison results of each candidate discharge start-point and end-point pair, the corresponding actual shortest surface creepage path, the location of the creepage weak zone and its insufficient creepage distance, and the corresponding structural adjustment suggestions are compiled to generate a report for creepage distance verification of low-voltage power distribution systems.

[0013] The beneficial effects of this invention are as follows: 1. This invention establishes a well-structured creepage distance rule knowledge base by organizing the relevant standard clauses into fields based on factors such as rated insulation voltage, pollution level, overvoltage category, and material group or tracking resistance index. This allows voltage level, environmental conditions, material characteristics, and corresponding correction rules to be maintained in association under the same data structure. After inputting the operating environment and operating condition parameters, engineers can directly obtain the corresponding target minimum creepage distance threshold from the knowledge base. Furthermore, correction factors such as altitude, temperature rise, and humidity are considered simultaneously in the same calculation link, reducing the risk of misunderstanding and omissions caused by manual table lookups and multiple rounds of conversion. This makes it easier for the verification results of creepage distance in low-voltage power distribution systems to be consistent with current standard requirements.

[0014] 2. This invention identifies live conductors, grounded conductors, and insulating surfaces based on a three-dimensional structural model of a low-voltage power distribution system. It establishes the electrical topology relationship between live conductors, insulating surfaces, and grounded conductors, and performs creepage propagation semantic annotation on the insulating surfaces. On this basis, it constructs a surface reachability graph and calculates the actual shortest surface creepage path between candidate discharge start and end pairs. By distinguishing and constraining the surface propagation area from the shielded area and the non-surface propagation area, the calculated surface path can reflect the comprehensive influence of creepage ribs, grooves, reinforcing ribs, partitions, and metal shielding components on the creepage path. This overcomes the problem of insufficient attention to three-dimensional details when estimating only based on two-dimensional projection dimensions, and facilitates the identification of local creepage weak points during the design stage.

[0015] 3. This invention further introduces manufacturing and assembly parameters such as insulation component molding shrinkage, busbar or terminal assembly tolerances, and isolator installation offset. Various deviations are converted into length compensation amounts along the path direction, and the creepage path length along the surface is corrected to obtain an equivalent actual creepage distance closer to the finished product state. This is then compared with the target minimum creepage distance threshold. When the creepage margin of a candidate discharge path is insufficient, the corresponding creepage weakness area is determined by the projection of that path into the structural model. A structural adjustment scheme is selected from a preset rectification strategy table based on semantic categories, ensuring that the verification results, weak point location, and structural adjustment suggestions maintain a corresponding relationship. This facilitates the formation of a clear rectification loop in the design and process stages. Attached Figure Description

[0016] Figure 1 A flowchart for establishing the creepage distance rule knowledge base of this invention; Figure 2 This is a flowchart illustrating the calculation of the actual shortest surface creepage path in this invention. Figure 3 This is a flowchart of the creepage distance verification and result output of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figures 1 to 3As shown, this embodiment of the invention provides a method for verifying the creepage distance of a low-voltage power distribution system. Based on the relevant standard clauses of creepage distance and the three-dimensional structural model of the low-voltage power distribution system, and combined with the operating environment conditions and manufacturing and assembly deviations, the method quantitatively verifies each candidate discharge path in the system and generates a verification result containing verification conclusions and structural adjustment suggestions. The method includes the following steps. First, obtain the relevant clauses on creepage distance from national or industry standards, and organize the contents of the clauses regarding rated insulation voltage, pollution level, overvoltage category, insulation material group or tracking resistance index, and corresponding correction rules into a unified field to establish a creepage distance rule knowledge base. In this knowledge base, the rated insulation voltage range, pollution level, overvoltage category, material group or tracking resistance index, and correction rules are used as basic fields so that creepage distance requirements from different standard sources can be called in a unified format in subsequent steps for determining the target minimum creepage distance threshold. Secondly, the three-dimensional structural model of the low-voltage power distribution system to be checked is retrieved. The geometric and positional information of components such as enclosures, switching devices, busbars, terminal blocks, and insulating supports are read from the model. In this structural model, conductors that are in a energized state are marked as live bodies, metal components that are electrically connected to the protective grounding terminal are marked as grounding bodies, and the surfaces of solid insulating components located between live bodies and grounding bodies or between different live bodies are marked as insulating isolation surfaces. Based on the above marking results, according to the spatial proximity relationship between live bodies and insulating isolation surfaces, and between insulating isolation surfaces and grounding bodies, the electrical topology relationship between live bodies, insulating isolation surfaces, and grounding bodies is established. Pairs of live bodies between phases that are isolated by the same insulating isolation surface and have a potential difference, as well as pairs of live bodies to ground bodies, are selected as candidate discharge start and end points for creepage verification. Then, the creepage propagation semantics of the insulating isolation surface are annotated. Specifically, the area on the outer surface of the creepage rib is marked as the creepage rib boundary, the area at the bottom of the groove or the side wall of the groove is marked as the groove boundary, the area on the edge of the reinforcing rib is marked as the reinforcing rib boundary, and the area on the free edge of the partition is marked as the partition edge boundary. The insulating isolation surface area adjacent to the metal shield is marked as the shield boundary, and the area that is blocked by the metal part or directly connected to the outside air and does not form a surface creepage path in the structural design is marked as the non-surface propagation boundary. The shield boundary and the non-surface propagation boundary are set as the limiting boundary of the surface path to constrain the search range of the subsequent surface path. Based on the semantic annotations described above, the insulating surface is discretized and a surface reachability graph is constructed. Multiple surface nodes located on the insulating material are generated on the insulating surface at predetermined intervals, and the spatial position of each surface node in the three-dimensional coordinate system is recorded. Based on whether the geometric connection between adjacent surface nodes falls completely on the insulating surface and whether it crosses the shielding boundary or the non-propagation boundary, the surface reachability edges that can be established between adjacent surface nodes are determined. Only when the geometric connection is located on the insulating surface and does not cross the aforementioned limiting boundary are surface reachability edges established between the corresponding surface nodes, thus obtaining a surface reachability graph composed of surface nodes and surface reachability edges. The spatial position of each candidate discharge start point and end point pair in the three-dimensional coordinate system is mapped to the surface node with the smallest Euclidean distance in the surface reachability graph, which is used as the start node and end node, respectively. The shortest path search is performed in the surface reachability graph with the geometric distance between adjacent surface nodes as the weight to obtain the actual shortest surface creepage path between the start node and the end node along the insulating surface. The actual shortest surface creepage path length of the corresponding candidate discharge start point and end point pair is determined by the sum of the geometric distances of each surface reachability edge on the shortest path. Subsequently, the operating environment and working condition parameters of the low-voltage power distribution system to be verified are input. These parameters include pollution level, altitude, temperature rise range, and humidity range. The above parameters, along with the system's rated insulation voltage, overvoltage category, and material group or tracking resistance index range, are input into the creepage distance rule knowledge base as query conditions. In the creepage distance rule knowledge base, a set of rules that match the rated insulation voltage, pollution level, overvoltage category, and material group or tracking resistance index range and are applicable to the altitude, temperature rise range, and humidity range are retrieved. A benchmark rule is selected according to the pre-set adjudication priority of each rule, and the benchmark creepage distance recorded therein is read as the benchmark value. Then, according to the correction order recorded in the benchmark rule, the altitude correction, thermal and damp aging correction, and material tracking resistance attenuation correction are calculated in sequence. Each correction is then superimposed with the benchmark creepage distance to obtain the target minimum creepage distance threshold corresponding to the current operating environment and working conditions. After obtaining the path length and threshold, the actual shortest surface creepage path is compensated for deviations by combining the manufacturing and assembly parameters of each component in the structural model. Based on the manufacturing and assembly information recorded in the structural model, the molding shrinkage of the insulating component, the assembly tolerance of the busbar or terminal, and the installation offset of the isolator are determined respectively. The molding shrinkage, assembly tolerance, and installation offset are decomposed along the path direction of the actual shortest surface creepage path to obtain the length compensation amount along the path direction. After obtaining the length compensation amount, each length compensation amount is taken in the direction unfavorable to the surface creepage distance, and algebraically summed with the actual shortest surface creepage path length. The result is used as the equivalent actual creepage distance of the corresponding candidate discharge start point and end point pair to reflect the surface creepage margin after considering manufacturing and assembly deviations. Finally, the equivalent actual creepage distance is compared with the target minimum creepage distance threshold. Candidate discharge start-point and end-point pairs with an equivalent actual creepage distance greater than or equal to the target minimum creepage distance threshold are recorded as qualified creepage objects, while candidate discharge start-point and end-point pairs with an equivalent actual creepage distance less than the target minimum creepage distance threshold are recorded as unqualified creepage objects. The corresponding actual shortest surface creepage path is saved. For unqualified creepage objects, their actual shortest surface creepage path is projected onto the 3D structural model to obtain the insulating isolation surface area traversed by the path, and this area is used as the creepage... Weak areas are recorded, and the difference between the target minimum creepage distance threshold and the equivalent actual creepage distance is used as the insufficient creepage distance of the weak area. Based on the category of the weak area in the aforementioned semantic annotation, the structural adjustment scheme corresponding to the semantic category is retrieved from the preset rectification strategy table to form a structural adjustment suggestion for the weak area. Based on the comparison results of each candidate discharge start point and end point pair, the corresponding actual shortest surface creepage path, the location and insufficient amount of the weak area, and the corresponding structural adjustment suggestion, a report for creepage distance verification of the low-voltage power distribution system is generated.

[0019] In one specific embodiment of the present invention, the creepage distance rule knowledge base is established by extracting standard clauses and performing structured modeling. Specifically, from national or industry standards related to creepage distance, the creepage distance requirements given for different rated insulation voltages, pollution levels, overvoltage categories, and insulation material groups or tracking indices are identified one by one. Each clause is extracted as a rule record and uniformly mapped to a preset data structure. The data structure includes at least: a rated insulation voltage range field, a pollution level field, an overvoltage category field, an insulation material group field or a tracking index range field, a baseline creepage distance value field, and a correction item type field associated with the baseline creepage distance. These fields are used to record the voltage range, environmental level, overvoltage category, material characteristics, creepage distance under uncorrected conditions, and whether subsequent altitude correction, thermal and damp aging correction, and material tracking attenuation correction are required. In the above rule records, to distinguish different types of creepage objects, each rule is set with an applicable object identifier field, which indicates that the rule applies to phase-to-phase live conductor pairs or live conductor-to-ground conductor pairs in low-voltage power distribution systems. For example, the applicable object identifier can be PH-PH to indicate that it applies to the creepage distance requirements between any two phase live conductors, or PH-PE to indicate that it applies to the creepage distance requirements between a phase conductor and a protective grounding conductor. During verification, the system considers the applicable object identifier when retrieving rules, so that rules for phase-to-phase creepage distance will not be mistakenly used for verification of creepage distance to ground, and vice versa. To obtain a definite verification basis when the operating conditions are complex and the standard clauses may overlap, each rule record is also equipped with an applicable conditions field and an adjudication priority field. The applicable conditions field is used to record in a structured form the combination range of the rated insulation voltage range, pollution level, overvoltage category, and material group or tracking resistance index range corresponding to the rule. After receiving the operating environment and operating condition parameters, the verification system matches the actual conditions with the applicable conditions field and filters out the set of rules that meet the conditions. The adjudication priority field is used to sort the rule set and select the one with the highest priority as the benchmark rule when multiple rules meet the applicable conditions at the same time. This determines the benchmark creepage distance value and correction item type used for subsequent calculations. In practical implementation, the creepage distance rule knowledge base can use a database table or other data structure that supports access to record fields to store the above rule records. Optionally, rule number and rule source fields can be set and associated with the corresponding standard clause number or table row number to trace the rule source. When operating environment and working condition parameters are input, the verification system uses information related to rated insulation voltage, pollution level, overvoltage category, material group or tracking resistance index range, and factors such as altitude to match the applicable condition field, obtaining a set of rules that meet the conditions. Then, based on the adjudication priority field, a benchmark rule is selected, and the benchmark creepage distance value and correction item type field of that rule are read. In subsequent steps, altitude correction, thermal and damp aging correction, and material tracking resistance attenuation correction are performed according to the items and order indicated by the correction item type field.

[0020] In one specific embodiment of the present invention, the process of retrieving the structural model of the low-voltage power distribution system to be verified and generating candidate discharge start-point and end-point pairs includes: First, reading the geometric information and position information of the enclosure, switching devices, busbars, terminal blocks and insulating support components in a unified coordinate system from the three-dimensional design model of the low-voltage distribution cabinet or distribution box. Combining the wiring relationships and working states recorded in the electrical design data, conductor components connected to the phase line or neutral line and in a live state under rated operating conditions are marked as live bodies, and metal components electrically connected to the protective grounding terminal or grounding busbar through protective conductors are marked as grounding bodies. For solid insulating components used to support or isolate busbars and switching devices, the portion of their outer surface located between live bodies and grounding bodies or between different live bodies is extracted and marked as insulating isolation surface. After completing the above annotations, an electrical topology relationship between the charged body, the insulating surface, and the grounding body is established based on their relative positions in three-dimensional space. Specifically, in the three-dimensional coordinate system, each charged body and grounding body is used as a topology node, and each insulating surface is used as an intermediate node. When the shortest distance between the charged body and the insulating surface, and between the insulating surface and the grounding body, is less than a preset threshold, a connection edge is established between the corresponding nodes, thereby forming a topology structure of charged body-insulating surface-grounding body. For insulating surfaces located between different charged bodies, the same method is used to establish a topology structure of charged body-insulating surface-charged body. Based on the above electrical topology, and combined with the voltage level or potential identifier recorded in the electrical design data, each live node is assigned a potential attribute. Node pairs between two live bodies with different potentials that are connected topologically through the same insulating surface, or between a live body and a grounding body, are selected as candidate discharge start and end point pairs for creepage verification. Node pairs with the same potential or belonging to the same equipotential bonding group are not included in the candidate discharge start and end point pairs. Through the above steps, the three-dimensional design model obtains a set of candidate discharge start and end points corresponding to the actual three-dimensional layout and potential distribution, providing an object basis for subsequent surface creepage path calculation and creepage distance verification.

[0021] In one specific embodiment of the present invention, the creepage propagation semantic annotation of the insulating isolation surface includes region division and boundary attribute setting. Specifically, for the aforementioned three-dimensional surface segments already marked as insulating isolation surfaces, according to their geometric features and positional relationships in the three-dimensional model, the region located on the outer surface of the creepage rib is marked as the creepage rib boundary, the region located at the bottom of the groove or the side wall of the groove is marked as the groove boundary, the region located on the edge of the reinforcing rib is marked as the reinforcing rib boundary, and the region located at the free edge of the partition is marked as the partition edge boundary. The creepage rib, groove, reinforcing rib, and free edge of the partition can be identified by the shape, normal, and topological relationship with adjacent entities of the corresponding feature surface in the three-dimensional model, and the identification results are recorded as boundary type labels on the corresponding insulating isolation surface. For the insulating surface area adjacent to the metal shield, the contact or close proximity relationship between the insulating surface and the metal shield is detected in the 3D model, and this part of the insulating surface is marked as the shield boundary; for the insulating surface area that is blocked by the metal part or directly connected to the outside air through ventilation holes, mounting holes or other structures and does not serve the function of surface creepage path in the structural design, it is marked as the non-surface propagation boundary. The shield boundary and the non-surface propagation boundary are recorded as specific semantic categories when annotating, and are used to identify the areas that need to be restricted from surface creepage propagation in subsequent path calculations; When constructing the surface reachability graph and calculating the actual shortest surface creepage path, regions marked as shield boundaries and regions marked as non-surface propagation boundaries are uniformly treated as restricted boundaries for surface paths. In the process of discretizing the insulating surface to generate surface nodes and determining whether a surface reachable edge is established between adjacent surface nodes, when the geometric connection between adjacent nodes falls into the aforementioned restricted boundary region, or when the connection crosses such a region, a surface reachable edge is not established between the corresponding nodes. A surface reachable edge is established between two nodes only when the geometric connection is completely located within the insulating surface region that is not marked as a shield boundary or non-surface propagation boundary, so that the connectivity in the surface reachability graph is limited to the insulating region where surface creepage propagation may actually occur.

[0022] In one specific embodiment of the present invention, after completing the semantic annotation of creepage propagation on the insulating surface, the insulating surface is discretized and a surface reachability graph is constructed to calculate the actual shortest creepage path along the surface. Specifically, for a three-dimensional surface segment marked as an insulating surface, multiple surface nodes located on the insulating material are generated on the surface at predetermined intervals, and the spatial coordinates of each surface node in a unified three-dimensional coordinate system and the identification information of the insulating surface to which it belongs are recorded. The predetermined interval is set according to the characteristic dimensions and calculation accuracy requirements of the power distribution equipment to be checked, so that the distance between adjacent surface nodes can reflect the geometric changes of the insulating surface. After generating surface nodes, based on the markings of shielding boundaries and non-surface propagation boundaries in the semantic annotation results, the aforementioned regions are used as the restricted boundaries for surface paths. When determining whether to establish a surface reachable edge between adjacent surface nodes, the three-dimensional geometric connection between the two surface nodes is calculated. When the geometric connection falls entirely on the insulating isolation surface and does not fall into or cross the region marked as a shielding boundary or non-surface propagation boundary, a surface reachable edge is established between the corresponding surface nodes, and the geometric distance between the two nodes is used as the edge weight of the surface reachable edge. When the geometric connection is not entirely located on the insulating isolation surface, or intersects with the aforementioned restricted boundary region, a surface reachable edge is not established between the corresponding surface nodes. Thus, surface nodes and surface reachable edges constitute a surface reachability graph, and the connectivity of the surface reachability graph is limited to the insulating region where surface creepage propagation may actually occur. After obtaining the surface reachability graph, the spatial positions of each candidate discharge start-point and end-point pair in the three-dimensional coordinate system are mapped to surface nodes in the surface reachability graph: For each candidate discharge start-point or end-point, the surface node with the smallest Euclidean distance located on the corresponding insulating surface is searched, and this surface node is used as the start node and end node of the candidate discharge start-point and end-point pair in the surface reachability graph, respectively. In the surface reachability graph, the shortest path between the start node and the end node is solved using the geometric distance between adjacent surface nodes as the edge weight, obtaining the actual shortest surface creepage path extending along the insulating surface, and the sum of the geometric distances of each surface reachable edge on this shortest path is taken as the actual shortest surface creepage path length of the candidate discharge start-point and end-point pair.

[0023] In one specific embodiment of the present invention, the process of determining the target minimum creepage distance threshold based on the operating environment and operating parameters includes: collecting the operating environment and operating parameters of the low-voltage power distribution system to be verified, wherein the operating environment and operating parameters include at least pollution level, altitude, temperature rise range, and humidity range; and obtaining the rated insulation voltage, overvoltage category, and material group or tracking resistance index range of the low-voltage power distribution system from the design data, and inputting the above-mentioned operating environment and operating parameters, together with the rated insulation voltage, overvoltage category, and material group or tracking resistance index range, as query conditions into the aforementioned creepage distance rule knowledge base; In the creepage distance rule knowledge base, the applicable condition fields of each rule record are matched to retrieve the rule set that matches the rated insulation voltage, pollution level, overvoltage category, material group or tracking resistance index range, and is applicable to the current altitude, temperature rise range and humidity range. The rule set is sorted according to the pre-set adjudication priority field of each rule, and the rule with the highest priority is selected as the benchmark rule. The benchmark creepage distance value recorded by the benchmark rule is read as the benchmark creepage distance before environmental and material corrections are made. After determining the baseline creepage distance, the altitude correction, thermal and damp aging correction, and material tracking resistance attenuation correction are calculated sequentially according to the correction order field recorded in the baseline rules. The correction amounts are determined according to the relevant standard clauses or agreed calculation formulas, and are used to reflect the correction effects of altitude, temperature rise and humidity range, and material group or tracking resistance index range on the creepage distance requirements. The baseline creepage distance is algebraically added to the altitude correction, thermal and damp aging correction, and material tracking resistance attenuation correction to obtain the target minimum creepage distance threshold corresponding to the current operating environment and conditions, which is used for subsequent comparison with the equivalent actual creepage distance.

[0024] In one specific embodiment of the present invention, converting the actual shortest surface creepage path length into an equivalent actual creepage distance includes: determining the molding shrinkage of the insulating component, the assembly tolerance of the busbar or terminal, and the installation offset of the isolator based on the manufacturing and assembly parameters of each component in the low-voltage power distribution system structural model. The molding shrinkage is determined based on the shrinkage coefficient of the material used in the insulating component and the molding process, as well as the mold cavity size, and is used to characterize the reduction in size of the insulating component after molding relative to the design size. The assembly tolerance is determined based on the dimensional tolerances, hole position tolerances, and fit tolerances given in the assembly drawings for the busbar or terminal, and is used to characterize the deviation range of the actual installation position of the conductor relative to the design position. The installation offset is determined based on parameters such as the mounting hole position tolerance of the isolator and the positioning accuracy of the mounting tooling, and is used to characterize the overall displacement deviation of the isolator relative to the enclosure or mounting reference surface. After obtaining the above three types of deviation parameters, the molding shrinkage, assembly tolerance, and installation offset are decomposed along the path direction of the actual shortest surface creepage path to obtain the length compensation amount along this path direction. Specifically, taking the tangent direction of the actual shortest surface creepage path as the reference direction, the components of the dimensional changes caused by the molding shrinkage of the insulating part, the installation offset of the busbar or terminal, and the overall displacement of the isolator in this direction are calculated and used as the corresponding length compensation amounts. For each candidate discharge start point and end point pair, the corresponding length compensation amounts are taken in the direction that is unfavorable to the surface creepage distance. When a certain deviation may lead to a reduction in the surface distance between the charged body and the grounded body, the reduction component of the deviation in the path direction is taken. Finally, the above length compensation amounts are algebraically summed with the actual shortest surface creepage path length of the candidate discharge start and end point pair. The result is taken as the equivalent actual creepage distance of the candidate discharge start and end point pair, so that the equivalent actual creepage distance reflects the surface creepage margin after considering the shrinkage of the insulation component forming, the conductor assembly tolerance, and the insulator installation offset.

[0025] In one specific embodiment of the present invention, the creepage distance verification for each candidate discharge start-point and end-point pair includes: calling the equivalent actual creepage distance and the target minimum creepage distance threshold obtained above, and performing a numerical comparison on each candidate discharge start-point and end-point pair; when the equivalent actual creepage distance is greater than or equal to the target minimum creepage distance threshold, the candidate discharge start-point and end-point pair is marked as a qualified creepage object; when the equivalent actual creepage distance is less than the target minimum creepage distance threshold, the candidate discharge start-point and end-point pair is marked as a unqualified creepage object, and the actual shortest surface creepage path corresponding to the candidate pair is recorded; For candidate discharge start-point and end-point pairs marked as non-compliant creepage objects, their corresponding actual shortest surface creepage paths are projected onto the 3D structural model to obtain the insulation isolation surface area traversed by the path in the structural model, and this area is identified as the creepage weak area corresponding to the candidate pair. The creepage distance deficiency of the creepage weak area is determined by subtracting the equivalent actual creepage distance from the target minimum creepage distance threshold. Based on the aforementioned creepage propagation semantic annotation results of the insulation isolation surface, the semantic category to which the creepage weak area belongs is read, and it is classified as at least one of creepage rib boundary, groove boundary, reinforcing rib boundary, or partition edge boundary. Then, according to the preset rectification strategy table, the structural adjustment scheme corresponding to the semantic category is selected in the table to form a structural adjustment suggestion for the creepage weak area. After completing the comparison of all candidate discharge start and end point pairs and the identification of creepage weak areas, the comparison results of each candidate pair, the corresponding actual shortest creepage path along the surface, the location of each creepage weak area in the structural model and its insufficient creepage distance are summarized, and structural adjustment suggestions based on the rectification strategy table are attached. A creepage distance verification report is generated to characterize the creepage verification conclusions of the current low-voltage power distribution system on each candidate discharge path and the corresponding structural adjustment scheme.

[0026] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0027] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for checking the creepage distance of a low-voltage power distribution system, characterized in that: The method comprises: acquiring a standard clause related to the creepage distance, structurally sorting the standard clause based on a rated insulation voltage, a pollution level, an overvoltage category and insulation material characteristics, establishing a creepage distance rule knowledge base, and using the creepage distance rule knowledge base to determine a target minimum creepage distance threshold under different operating conditions; calling a three-dimensional structure model of a low-voltage distribution system to be checked, identifying live bodies, grounded bodies and insulation isolation surfaces therebetween in the structure model, establishing an electrical topology relationship of live bodies-insulation isolation surfaces-grounded bodies based on the spatial proximity relationship between the live bodies and the insulation isolation surfaces and between the insulation isolation surfaces and the grounded bodies, and determining candidate discharge starting and ending points requiring creepage checking from the electrical topology relationship; performing creepage propagation semantic labeling on the insulation isolation surfaces, and distinguishing and marking regions for surface creepage propagation and regions as surface path limit boundary; based on the semantic labeling, performing discretization processing on the insulation isolation surfaces, constructing a surface reachability graph, mapping the candidate discharge starting and ending points to starting nodes and terminating nodes in the surface reachability graph, and calculating actual shortest surface creepage paths and path lengths between the candidate discharge starting and ending points under limit boundary constraints; collecting operating environment and working condition parameters of the low-voltage distribution system to be checked, inputting the operating environment and working condition parameters together with the rated insulation voltage, the overvoltage category and the material characteristics into the creepage distance rule knowledge base, and determining target minimum creepage distance thresholds corresponding to each candidate discharge starting and ending point pair according to the creepage distance rule knowledge base; combining manufacturing and assembly parameters of components in the structure model to correct the actual shortest surface creepage path lengths of each candidate discharge starting and ending point pair to obtain corresponding equivalent actual creepage distances; comparing the equivalent actual creepage distances of each candidate discharge starting and ending point pair with the corresponding target minimum creepage distance thresholds, outputting creepage checking conclusions for each candidate discharge starting and ending point pair, and identifying creepage weak areas in the structure model and giving structure adjustment suggestions when the structure is determined to be unqualified.

2. The creepage distance checking method of a low-voltage distribution system according to claim 1, characterized in that: The establishment of the creepage distance rule knowledge base comprises: extracting rule clauses related to the creepage distance in national standards or industry standards into a unified data structure, and recording corresponding rated insulation voltage intervals, pollution levels, overvoltage categories, insulation material groups or electrical tracking resistance index intervals, baseline creepage distance values and correction item types associated with the baseline creepage distance in each rule; setting an applicable object identifier for each rule, which is used to indicate that the rule is applicable to a pair of phase-to-phase live bodies or a pair of live bodies-to-grounded bodies in a low-voltage distribution system, and setting an applicable condition field and a ruling priority field for each rule, wherein the applicable condition field limits the combination range of the rated insulation voltage interval, the pollution level, the overvoltage category and the material group or the electrical tracking resistance index interval corresponding to the rule, and the ruling priority field is used to determine the calling order of the baseline creepage distance and the correction item when multiple rules meet the applicable conditions at the same time.

3. The creepage distance checking method of a low-voltage distribution system according to claim 2, characterized in that: The structure model of the low-voltage power distribution system to be checked comprises: reading geometric information and position information of a cabinet, switch devices, busbars, terminal blocks and insulation support components from a three-dimensional design model of a low-voltage power distribution cabinet or a distribution box; in the three-dimensional design model, marking a conductor component in a live state as a live body, marking a metal component connected to a protective ground as a ground body, and marking a surface of a solid insulation component located between the live body and the ground body or between different live bodies as an insulation isolation surface; based on the marking results, establishing an electrical topology relationship of the live body-insulation isolation surface-ground body according to the spatial proximity relationship between the live body and the insulation isolation surface and the insulation isolation surface and the ground body, and selecting a pair of live bodies or a pair of a live body and a ground body isolated from each other by the same insulation isolation surface and having a potential difference in the electrical topology relationship as a candidate discharge starting point and ending point pair to be checked.

4. The creepage distance checking method of a low-voltage distribution system according to claim 3, characterized in that: The semantic labeling of the creepage propagation on the insulation isolation surface comprises: regionally dividing the insulation isolation surface, marking a region located on the outer surface of the creepage rib as a creepage rib boundary, marking a region located on the bottom of the groove or the side wall of the groove as a groove boundary, marking a region located on the edge of the reinforcing rib as a reinforcing rib boundary, marking a region located on the free edge of the partition plate as a partition plate edge boundary, marking a region adjacent to the metal shielding member as a shielding boundary, and marking a region blocked by the metal member or directly connected to the outside air and not forming a surface creepage path in the structural design as an unpropagatable boundary; when constructing the surface accessibility graph and calculating the actual shortest surface creepage path, marking the regions marked as the shielding boundary and the unpropagatable boundary as the line-limiting boundaries of the surface path, and not establishing a surface accessible edge between the regions in the surface accessibility graph.

5. The creepage distance checking method of a low-voltage distribution system according to claim 4, characterized in that: The construction of the surface accessibility graph and the calculation of the actual shortest surface creepage path on the insulation isolation surface on the basis of the semantic labeling comprises: discretizing the insulation isolation surface that has been semantically labeled, generating a plurality of surface nodes on the insulation material on the insulation isolation surface according to a predetermined interval, and recording the spatial positions of the surface nodes in the three-dimensional coordinate system; determining the surface accessible edges that can be established between adjacent surface nodes according to whether the geometric connection line between the adjacent surface nodes falls completely on the insulation isolation surface and whether the geometric connection line crosses the shielding boundary or the unpropagatable boundary, and establishing a surface accessible edge between the corresponding surface nodes only when the geometric connection line is located on the insulation isolation surface and does not cross the line-limiting boundary, so that the surface accessibility graph is constructed by the surface nodes and the surface accessible edges; The space positions of each candidate discharge starting point and ending point pair in a three-dimensional coordinate system are respectively mapped to the surface nodes with minimum Euclidean distance in the surface reachable graph, as the corresponding starting node and terminating node, a shortest path search is performed in the surface reachable graph with the geometric distance between adjacent surface nodes as the weight, to obtain the actual shortest surface creepage path along the insulating isolation surface between the starting node and the terminating node, and the length of the actual shortest surface creepage path of the candidate discharge starting point and ending point pair is determined by the sum of the geometric distances of each surface reachable edge on the shortest path.

6. The creepage distance checking method of a low-voltage distribution system according to claim 5, characterized in that: The target minimum creepage distance threshold value determined according to the operating environment and working condition parameters includes: collecting the operating environment and working condition parameters of the low-voltage power distribution system to be checked, the operating environment and working condition parameters including pollution level, altitude, temperature rise range and humidity range, and inputting the operating environment and working condition parameters together with the rated insulation voltage of the low-voltage power distribution system, the overvoltage category and the material group or the electrical tracking resistance index interval as a query condition into the creepage distance rule knowledge base; In the creepage distance rule knowledge base, a rule set that matches the rated insulation voltage, pollution level, overvoltage category and material group or electrical tracking resistance index interval and is applicable to the altitude, temperature rise range and humidity range is searched, and a reference rule is determined from the rule set according to the decision priority field set in advance for each rule, and the reference creepage distance is determined according to the reference creepage distance value recorded in the reference rule; according to the correction sequence field recorded in the reference rule, the altitude correction amount, the thermal and humidification aging correction amount and the material electrical tracking resistance decay correction amount are calculated in turn, and each correction amount is added to the reference creepage distance to obtain the target minimum creepage distance threshold value.

7. The method for creepage distance verification of a low-voltage distribution system according to claim 6, characterized in that: The actual shortest surface creepage path length is converted into an equivalent actual creepage distance, which includes: based on the manufacturing and assembly parameters of each component in the low-voltage power distribution system structure model, the forming shrinkage of the insulating part, the assembly tolerance of the busbar or terminal and the installation offset of the isolation body are determined respectively; The forming shrinkage, assembly tolerance and installation offset are decomposed along the path direction of the actual shortest surface creepage path to obtain the length compensation along the direction of the actual shortest surface creepage path; Each length compensation is valued in the direction unfavorable to the surface creepage distance, and is algebraically summed with the actual shortest surface creepage path length, and the result is taken as the equivalent actual creepage distance of the corresponding candidate discharge starting point and ending point pair.

8. The creepage distance checking method of a low-voltage distribution system according to claim 7, characterized in that: For each candidate discharge starting point and ending point pair, the corresponding equivalent actual creepage distance is compared with the target minimum creepage distance threshold value to determine whether the creepage of the candidate discharge starting point and ending point pair is qualified, and the corresponding actual shortest surface creepage path is recorded when it is determined to be unqualified. The actual shortest surface creeping path is projected in the structure model to obtain an insulating isolation surface region passed by the path, and the region is determined as a creeping weak region, and an insufficient amount of the creeping weak region is determined by subtracting the equivalent actual creeping distance from the target minimum creeping distance threshold; according to a semantic category to which the creeping weak region belongs, a structure adjustment scheme corresponding to the semantic category is selected in a preset rectification strategy table to form a structure adjustment suggestion for the creeping weak region, and a creeping distance checking report is generated based on a comparison result of each candidate discharge starting point and ending point pair, the actual shortest surface creeping path, the creeping weak region and the structure adjustment suggestion for the creeping weak region.

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