A municipal power engineering underground cable pipe distribution design method

Abstract

The application belongs to the technical field of power aided design, and relates to a municipal power engineering underground cable pipe distribution design method. The application obtains deep unrecovered areas, false thermal recovery time windows, cable loop load values, and combinations of cable loops, candidate paths and candidate hole positions, respectively calculates conductor temperatures according to measured soil moisture contents, measured soil temperatures, and recovery moisture contents and recovery temperatures, and generates candidate additional temperature rise sequences; divides thermal coupling loop groups according to outage cable loop numbers, cable loop numbers to be connected, temperature rise time period overlap relationships and deep unrecovered area influences, eliminates combinations of multiple cable loops in the same group passing through the same deep unrecovered area or occupying corresponding candidate hole positions, and determines pipe paths and hole positions of each cable loop. The application can reduce temperature underestimation caused by false thermal recovery, reduce conductor temperature overrun risks during load transfer, and improve the accuracy of underground cable pipe distribution design.

Description

Technical Field

[0001] This invention relates to the field of power auxiliary design technology, and in particular to a method for designing the distribution of underground cable ducts in municipal power engineering. Background Technology

[0002] In the design of underground cable duct distribution in municipal power engineering, existing methods typically obtain cable load, duct structure, hole location, soil thermal resistivity, and ambient temperature to establish a temperature field simulation model to determine the duct path and hole location of the cable loop. To reduce the computational load, some methods treat the soil around the duct as undergoing synchronous recovery and determine whether the entire duct section has completed thermal recovery based on the moisture content and temperature of the soil at the top of the duct.

[0003] However, long-term high-load operation of cables can cause the soil around the ducts to lose water due to heat. After rainfall, rainwater infiltrates from the surface to deeper layers of the soil, and the soil at the top of the duct usually recovers before the soil on the sides and bottom of the duct. When the soil at the top of the duct has become wet and cooled down, the soil on the sides or bottom of the duct may still be in a state of high temperature and high thermal resistance, forming a false thermal recovery where the top appears to have recovered but the deeper layers have not actually recovered.

[0004] During pseudo-thermal recovery, when multiple cable loops with transfer relationships are arranged at boreholes affected by the same deep unrecovered area, their additional temperature rises may overlap within the same time period. Existing methods do not compare the borehole temperature difference corresponding to measured soil parameters and restored soil parameters, nor do they identify the temperature rise correlation between cable loops. This easily leads to multiple cable loops with transfer relationships being concentrated near the same deep unrecovered area, causing the conductor temperature to exceed the allowable temperature during transfer, accelerating cable insulation aging, and reducing the reliability of underground cable transfer. Summary of the Invention

[0005] The purpose of this invention is to solve the problem that existing underground cable duct distribution design methods cannot accurately identify the deep unrecovered areas and the temperature rise superposition between transfer cable circuits during the pseudo-thermal recovery period, which easily leads to multiple cable circuits with transfer relationships being concentrated near the same deep unrecovered area. Therefore, this invention proposes an underground cable duct distribution design method for municipal power engineering.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for designing the distribution of underground cable ducts in municipal power engineering, comprising the following steps: obtaining deep unrecovered areas, pseudo-thermal recovery time windows, cable loop load values ​​at each acquisition time, out-of-service cable loop numbers, receiving cable loop numbers, and combinations of each cable loop number with candidate path numbers and candidate hole location numbers;

[0007] For each combination, based on the cable loop load value at each acquisition time, the measured conductor temperature and the recovered conductor temperature at each acquisition time within the pseudo-thermal recovery time window are calculated according to the measured soil moisture content, measured soil temperature, and recovered moisture content and recovered temperature. The candidate additional temperature rise sequence is generated by subtracting the recovered conductor temperature from the measured conductor temperature.

[0008] Based on the out-of-service cable circuit number and the receiving cable circuit number, cable circuits that are affected by the same deep unrecovered area and whose candidate additional temperature rise exceeds the preset temperature rise threshold time periods are divided into thermal coupling circuit groups.

[0009] Eliminate combinations of two or more cable loops in the same thermal coupling loop group that pass through the same deep unrecovered area or occupy candidate hole positions affected by the deep unrecovered area, and determine the pipe routing and hole positions for each cable loop.

[0010] In summary, due to the adoption of the above-mentioned design method for underground cable duct distribution in municipal power engineering, the beneficial effects of this invention are as follows: This invention determines the false thermal recovery time window and deep unrecovered areas by measuring the measured soil moisture content and measured soil temperature at the top, side and bottom of the duct, which solves the problem that relying solely on the monitoring results at the top of the duct can easily lead to the misjudgment that the deep soil has not yet recovered as the entire duct section has recovered, and realizes the dynamic identification of the differences in thermal recovery of the layers around the duct.

[0011] This invention calculates conductor temperature based on measured soil moisture content, measured soil temperature, and restored moisture content and temperature, and generates a candidate additional temperature rise sequence based on the difference between the two calculated conductor temperatures. This solves the problem that temperature calculation under a single restoration condition is difficult to separate the additional heat influence of deep unrestored areas, and improves the accuracy of temperature risk calculation for candidate paths and candidate well sites.

[0012] This invention divides thermally coupled circuit groups by combining the out-of-service cable circuit number, the receiving cable circuit number, the overlapping relationship of temperature rise periods, and the influence of deep unrecovered areas. It also eliminates combinations in which multiple cable circuits in the same group are concentrated in the same deep unrecovered area, thus solving the problem of temperature rise superposition during pseudo-thermal recovery of cable circuits with transfer relationships and reducing the risk of conductor temperature exceeding limits during load transfer. Attached Figure Description

[0013] Figure 1 A flowchart illustrating the underground cable duct distribution design method of the present invention is shown;

[0014] Figure 2 A schematic diagram of the thermal coupling circuit group division process of the present invention is shown;

[0015] Figure 3 A schematic diagram of the arrangement of monitoring locations in this invention is shown. Detailed Implementation

[0016] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the protection scope of the present invention.

[0017] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0018] Example 1:

[0019] See Figure 1 - Figure 3 This embodiment provides a method for designing the distribution of underground cable ducts in municipal power engineering. Among other things, Figure 1 Steps S1-S6 in the above text correspond to the following six processing steps, Figure 2 Steps S101-S105 correspond to the five sub-steps of step S5. Figure 3 This corresponds to the monitoring location setup, data acquisition, and identification of deep unrecovered areas in step S1.

[0020] See Figure 1 Step S1 involves acquiring the deep unrecovered area, the pseudo-thermal recovery time window, the cable loop load value at each acquisition time, the out-of-service cable loop number, the receiving cable loop number, and the combination of each cable loop number with the candidate path number and the candidate hole position number. Step S1 specifically includes the following processes.

[0021] Considering that the soil at the top of the drainage pipe usually becomes wet and cools down before the soil on the sides and bottom of the drainage pipe after rainfall, relying solely on data from the top of the drainage pipe could easily lead to the misjudgment that the deeper soil has not yet recovered as if the entire drainage pipe section has completed thermal recovery. Therefore, it is necessary to collect soil data from the top, sides, and bottom of the drainage pipe separately.

[0022] In one specific embodiment, multiple monitoring sections are set along the length of the pipe section, and soil moisture and soil temperature sensors are installed at the top, side, and bottom of the pipe at each monitoring section. The measured soil moisture and soil temperature are collected at a uniform sampling period, and the spatial location and sampling time of each monitoring point are recorded. As an example, the sampling period is set to 10 minutes.

[0023] See Figure 3 In step S1, Figure 3The dashed rectangles in the diagram represent monitoring sections, the rectangles within the monitoring sections represent pipes, and the multiple circular holes inside the pipes represent candidate well locations. The hollow circles located at the top, sides, and bottom of the pipes represent soil moisture sensors, and the hollow triangles represent soil temperature sensors. The soil moisture sensors at the top, sides, and bottom of the pipes collect the measured soil moisture content and measured soil temperature at their respective locations, while also recording the spatial location and acquisition time of each monitoring point. Figure 3 The area at the bottom of the pipe, filled with diagonal lines, represents the deep, unrecovered area. Its location and boundaries are for illustrative purposes only and are actually determined based on the measured soil moisture content, measured soil temperature, and spatial location at each monitoring location within the pseudo-thermal recovery time window, according to the interpolation and merging methods of the spatial grid cells described later. Therefore, Figure 3 The monitoring sections, top of the pipe, side of the pipe, bottom of the pipe, soil moisture sensor, soil temperature sensor, candidate well locations, and deep unrecovered areas in the monitoring section correspond one-to-one with the monitoring range, stratified acquisition location, acquisition device, candidate well location information, and deep unrecovered area identification results in step S1.

[0024] Then, the recovery moisture content is determined based on the historical soil moisture content when no high-load heat loss occurred in the pipeline section, and the recovery temperature is determined based on the historical soil temperature within the same season and time period that was not significantly affected by cable heating. Specifically, the median historical soil moisture content after excluding rainfall periods and abnormally high load periods can be determined as the recovery moisture content, and the corresponding median historical soil temperature can be determined as the recovery temperature. As an example, the same season is taken from the historical time period within the same natural month as the design time, and the same time period is taken from the same hour interval within a day; the period when the ratio of the cable circuit load value to the rated load value exceeds 80% is determined as the abnormally high load period, and the period when the ratio does not exceed 30% is determined as the period when it was not significantly affected by cable heating.

[0025] Subsequently, when the measured soil moisture content at the top of the pipe is not lower than the recovered moisture content and the measured soil temperature is not higher than the recovered temperature, but the side or bottom of the pipe does not simultaneously meet the above conditions, the corresponding sampling time is determined as the start time of the pseudo-thermal recovery time window; when both the side and bottom of the pipe simultaneously meet the above conditions, the sampling time at which the above conditions are first met is determined as the end time of the pseudo-thermal recovery time window. To reduce misjudgments caused by fluctuations in a single measurement, the condition can be considered valid only if the corresponding conditions are met at three consecutive sampling times.

[0026] If the top of the pipe no longer meets the recovery conditions before the side and bottom of the pipe reach the recovery conditions, the last time the top of the pipe met the recovery conditions is determined as the end time of the current pseudo-thermal recovery time window. When the top of the pipe meets the recovery conditions again, a new pseudo-thermal recovery time window is determined. If the side or bottom of the pipe has not reached the recovery conditions by the design time, the last time collected is determined as the temporary end time used for the current calculation, and subsequent temperature calculations continue based on the start time and temporary end time of the pseudo-thermal recovery time window. When new collected values ​​are obtained, the temporary end time is updated.

[0027] Furthermore, within the pseudo-thermal recovery time window, spatial locations where the measured soil moisture content is lower than the recovered moisture content or the measured soil temperature is higher than the recovered temperature are screened. Two screened spatial locations with a spatial distance not greater than the installation spacing of adjacent sensors are determined as adjacent spatial locations. Specifically, the soil space between adjacent monitoring sections is divided into spatial grid units, with the side length of each spatial grid unit not greater than the installation spacing of adjacent sensors. Using the measured soil moisture content and measured soil temperature of adjacent spatial locations as interpolation control values, linear interpolation is used to calculate the interpolated soil moisture content and interpolated soil temperature of each spatial grid unit. Spatial grid units where the interpolated soil moisture content is lower than the recovered moisture content or the interpolated soil temperature is higher than the recovered temperature are determined as unrecovered units, and unrecovered units with a common boundary are merged to form a deep unrecovered region.

[0028] Further, in step S1, a combination of cable loop number, candidate path number, and candidate hole number is generated.

[0029] Since the allocation of pipe routing and hole positions needs to meet the requirements of cable access, routing capacity and hole position occupancy, it is necessary to first generate a combination that meets the basic engineering conditions before performing temperature calculations.

[0030] In one specific embodiment, firstly, the access start point, access end point and cable loop number of each cable loop are obtained, and then the candidate path number, the maximum number of cable loops that each candidate path can accommodate, the candidate hole number contained in each candidate path, and the existing cable loop number in each candidate hole are obtained.

[0031] Then, candidate paths that can connect the corresponding access start point and access end point are selected for each cable loop, and candidate hole positions that do not have existing cable loop numbers are selected from the corresponding candidate paths.

[0032] Subsequently, the cable loop numbers, candidate path numbers, and candidate hole number are combined. Combinations with more than two cable loops assigned to the same candidate hole are eliminated, as are combinations with more than the maximum number of cable loops assigned to candidate paths. This yields the combinations used for temperature calculation.

[0033] Specifically, candidate path numbers and candidate hole positions are assigned one by one according to the cable loop number. After each cable loop is assigned, it is determined whether the corresponding candidate hole position has been assigned other cable loops, and whether the number of assigned cable loops for the corresponding candidate path exceeds the maximum number of cable loops. When a candidate hole position has been assigned or the number of assigned cable loops for a candidate path exceeds the maximum number of cable loops, the generation of combinations containing the current assignment relationship is stopped, and candidate paths and candidate hole positions are reselected.

[0034] See Figure 1 Step S2: For each combination, based on the cable loop load value at each acquisition time, calculate the measured conductor temperature and the recovered conductor temperature at each acquisition time within the pseudo-thermal recovery time window according to the measured soil moisture content, measured soil temperature, and recovered moisture content and recovered temperature.

[0035] Considering that the same candidate path and candidate borehole location have different heat dissipation capabilities under measured soil conditions and restored soil conditions, it is necessary to keep the cable loop load value and pipe structure the same, and determine the temperature difference caused by the deep unrestored area through two calculations.

[0036] In one specific embodiment, firstly, multiple moisture contents are set for soil samples in the pipe laying section, and the soil thermal resistivity corresponding to each moisture content is obtained through thermophysical property testing, thus establishing the correspondence between soil moisture content and soil thermal resistivity.

[0037] When the soil moisture content to be queried falls between two adjacent measured moisture contents, a linear interpolation is performed between the corresponding two measured soil thermal resistivity values ​​based on the proportion of the soil moisture content to be queried between the two measured moisture contents. Thus, the measured soil moisture content is converted to the measured soil thermal resistivity, and the recovered moisture content is converted to the recovered soil thermal resistivity. In this embodiment, the soil moisture content is the volumetric moisture content. For different soil layers and different backfill materials, a correspondence between soil moisture content and soil thermal resistivity is established. When the soil moisture content to be queried is lower than the minimum measured moisture content or higher than the maximum measured moisture content, the soil thermal resistivity corresponding to the measured moisture content closest to the soil moisture content to be queried is used, and a prompt for supplementary thermophysical property testing is output.

[0038] Then, using cable conductors, ducts, and soil as nodes, a thermal resistance and thermal capacity network is established according to the candidate path number and candidate hole number in each combination. The heating power of the cable conductor node is determined based on the cable loop load value, the number of current-carrying conductors, and the cable loss; the thermal resistance between nodes is determined based on the heat transfer distance, heat transfer area, and the thermal resistivity of the corresponding material; the node thermal capacity is determined based on the density, specific heat capacity, and representative volume of the node.

[0039] When the load value of the cable circuit is active power, the active power is converted into current value according to the corresponding voltage and power factor, and then the heating power of the cable conductor node is determined.

[0040] The temperature calculation formulas for each node in a thermal resistance-thermal capacity network are shown in the following example: .

[0041] in, Number the current node; Number adjacent nodes; This is the set of adjacent nodes that have a heat transfer relationship with the current node; and These represent two adjacent calculation times; This represents the heat capacity of the current node, in joules per Kelvin. and These are the temperatures of the current node at two adjacent calculation times, in degrees Celsius. The time step is calculated in seconds; This represents the heat output of the current node, in watts. The temperature of the adjacent nodes at the next calculation time, in degrees Celsius; The thermal resistance between the current node and its adjacent nodes is expressed in Kelvin per watt. The left side of the formula represents the thermal storage power of the current node, and the right side represents the sum of the heating power and heat transfer power of the current node. Both sides of the formula are expressed in watts, with consistent dimensions.

[0042] Furthermore, two temperature calculations were performed for each combination. The first calculation assigned the corresponding measured soil thermal resistivity and measured soil temperature to the deep unrecovered area at each acquisition time, yielding the measured conductor temperature. The second calculation assigned the recovered soil thermal resistivity and recovered temperature to the deep unrecovered area, yielding the recovered conductor temperature. Both calculations maintained the same initial conductor temperature, cable loop load value at each acquisition time, duct structure, calculation time step, and soil thermal resistivity outside the deep unrecovered area.

[0043] Specifically, the start time of the pseudo-thermal recovery time window is used as the starting point for temperature calculation. When a conductor temperature monitoring device is installed, the measured conductor temperature corresponding to this start time is determined as the initial conductor temperature. When no conductor temperature monitoring device is installed, the cable loop load value before this start time is read, and the measured soil temperature at the same time is used as the boundary temperature. The temperature is continuously calculated up to the start time using a thermal resistance-capacity network, and the resulting conductor temperature is determined as the initial conductor temperature. The backtracking time of the cable loop load value is gradually increased, and the difference in initial conductor temperature before and after increasing the backtracking time for each cable loop is calculated. The maximum value of all initial conductor temperature differences is extracted. When the maximum value is no greater than 0.5 degrees Celsius, the backtracking time is stopped, and the currently calculated conductor temperature of each cable loop is determined as the corresponding initial conductor temperature. The above backtracking calculation simultaneously obtains the temperatures of the pipe laying nodes and soil nodes at the calculation start point, and these are used as the initial temperatures of the corresponding nodes.

[0044] See Figure 1 Step S3: Subtract the recovered conductor temperature from the measured conductor temperature of the same combination, the same cable loop, and the same acquisition time to generate a candidate additional temperature rise sequence.

[0045] Directly comparing conductor temperatures of different combinations is easily affected by the initial conductor temperature and the cable circuit load value. Therefore, it is necessary to compare the measured conductor temperature and the recovered conductor temperature within the same combination.

[0046] In one specific embodiment, the measured conductor temperature and the recovered conductor temperature are matched one-to-one according to the combination, cable loop number, candidate path number, candidate hole position number, and acquisition time, and the candidate additional temperature rise is calculated according to the following formula: .

[0047] in, For the first The cable loop in the first Candidate additional temperature rise at each acquisition time; This corresponds to the measured conductor temperature; This corresponds to the recovery conductor temperature. When the candidate additional temperature rise is greater than zero, it indicates that the measured soil conditions caused an additional temperature rise relative to the recovery soil conditions; when the candidate additional temperature rise is not greater than zero, the corresponding acquisition time is not included in the temperature rise period. Candidate additional temperature rises for the same cable loop are arranged according to the acquisition time to generate a candidate additional temperature rise sequence.

[0048] See Figure 1 Step S4: Calculate the additional temperature rise in the target area caused by each deep unrecovered area, and determine the relationship between the candidate path and the candidate hole location and the influence of each deep unrecovered area.

[0049] When multiple deep unrecovered regions exist, simply comparing all measured conditions and all recovered conditions is insufficient to determine which deep unrecovered region specifically affects the candidate path and candidate well location. Therefore, it is necessary to calculate the temperature difference caused by each deep unrecovered region separately.

[0050] In one specific embodiment, firstly, the entire deep unrecovered region is assigned the measured soil thermal resistivity and measured soil temperature, and the temperature of the entire measured conductor is calculated.

[0051] Then, each deep unrestored region is sequentially identified as the target deep unrestored region, while keeping other deep unrestored regions unchanged. Only the target deep unrestored region is replaced with the restored soil thermal resistivity and restoration temperature, and the single-region restored conductor temperature is calculated.

[0052] Subsequently, the measured conductor temperature is subtracted from the single-zone recovered conductor temperature to obtain the additional temperature rise of the target area. When the additional temperature rise of the target area exceeds the preset temperature rise threshold for two or more consecutive acquisition times within the pseudo-thermal recovery time window, the corresponding candidate path and candidate aperture are determined to be affected by the deep unrecovered area of ​​the target.

[0053] Specifically, the maximum verification error of the thermal resistance-capacity network refers to the maximum absolute deviation between the calculated conductor temperature difference and the measured conductor temperature difference when performing paired verification using historical measured conductor temperatures against measured and restored soil conditions. The preset temperature rise threshold is the sum of the maximum absolute deviation, the allowable error of the conductor temperature sensor, and 0.5 degrees Celsius. For example, if the allowable error of the conductor temperature sensor is 0.5 degrees Celsius and the maximum absolute deviation is 1 degree Celsius, the preset temperature rise threshold is 2 degrees Celsius. The candidate path, candidate borehole location, and deep unrestored area are transformed to the same spatial coordinate system. When the outer contour of the pipe corresponding to the candidate path overlaps with the deep unrestored area in spatial grid cells, it is determined that the candidate path passes through the deep unrestored area; when the additional temperature rise of the target area exceeds the preset temperature rise threshold for two or more consecutive sampling times, it is determined that the corresponding candidate borehole location is affected by the deep unrestored area.

[0054] See Figure 1 Step S5: Based on the out-of-service cable circuit number, the receiving cable circuit number, the overlapping relationship of temperature rise periods, and the influence of deep unrecovered areas, divide the thermal coupling circuit group.

[0055] Since the out-of-service cable circuit has accumulated heat before the fault, and the receiving cable circuit generates more heat after the load is transferred, when both are affected by the same deep unrecovered area within the same time period, continuous local thermal risks can easily form. Therefore, it is necessary to divide the thermally coupled circuit group based on the transfer relationship, the temperature rise period, and the deep unrecovered area.

[0056] In one specific embodiment, during execution Figure 2Before steps S101-S105, the load value of the cable circuit, the out-of-service cable circuit number, and the receiving cable circuit number at each acquisition time are obtained. The out-of-service cable circuit number and the receiving cable circuit number are determined based on the load transfer scheme recorded by the power dispatching system.

[0057] See Figure 2 In step S101, the range of time periods in which the candidate additional temperature rise of each cable loop exceeds the preset temperature rise threshold for two or more consecutive sampling times is determined as the temperature rise period.

[0058] Step S102: Combine the circuit number of the out-of-service cable with the circuit number of the receiving cable to form a circuit number pair.

[0059] Step S103: Compare the temperature rise periods of the two cable loops in each loop number pair; when the two temperature rise periods have at least one identical acquisition time, determine that the two temperature rise periods overlap and retain the corresponding loop number pair.

[0060] Step S104: For the loop number pairs retained in step S103, determine whether the corresponding candidate path passes through the same deep unrecovered area, or whether the corresponding candidate hole position is affected by the same deep unrecovered area; if either condition is met, retain the corresponding loop number pair.

[0061] Step S105: Group the loop number pairs with the same cable loop number into the same set, and repeatedly merge the sets with the same cable loop number until any two remaining sets no longer have the same cable loop number, and divide the cable loop numbers contained in each set into a thermal coupling loop group.

[0062] See Figure 1 Step S6: Eliminate combinations in the same thermal coupling loop group where two or more cable loops pass through the same deep unrecovered area or occupy candidate hole positions affected by the deep unrecovered area, and determine the pipe routing path and hole position of each cable loop.

[0063] To avoid multiple cable loops in the same thermal coupling loop group being affected by the same deep unrecovered area, it is necessary to first eliminate the combination with concentrated thermal risk, and then perform temperature verification on the remaining combination.

[0064] In one specific embodiment, firstly, for each thermally coupled loop group and each deep unrecovered region in each combination, at each acquisition time of the pseudo-thermal recovery time window, the cable loop number that is a candidate additional temperature rise exceeding a preset temperature rise threshold and whose candidate path passes through the deep unrecovered region or whose candidate hole position is affected by the deep unrecovered region is selected.

[0065] Then, the number of different cable loop numbers selected at each acquisition time is counted, and the maximum value is determined as the number of loops in the same area corresponding to the deep unrecovered region. If the number of loops in the same area corresponding to any deep unrecovered region is not less than two, the corresponding combination is discarded.

[0066] Subsequently, the maximum value of all candidate additional temperature rise sequences in each remaining combination is extracted, and the remaining combination with the smallest maximum value is determined as the currently selected remaining combination. When the maximum values ​​of candidate additional temperature rise sequences corresponding to two or more remaining combinations are the same, the maximum conductor temperature of each remaining combination under the measured soil conditions is extracted, and the remaining combination with the smallest maximum conductor temperature is determined as the currently selected remaining combination; when the maximum conductor temperature is still the same, the remaining combination with the smallest total candidate path length is determined as the currently selected remaining combination.

[0067] Furthermore, the allowable conductor temperature of each cable circuit is obtained, which is determined based on the insulation material, rated voltage, and manufacturer's technical documents of the cable used in the corresponding cable circuit; and the conductor temperature of the currently selected remaining combination at each acquisition time within the pseudo-thermal recovery time window is calculated according to the measured soil moisture content and measured soil temperature.

[0068] When the temperature of any conductor exceeds the corresponding allowable conductor temperature, the currently selected remaining combination is eliminated, and the remaining combination with the smallest maximum value of the candidate additional temperature rise sequence is reselected; when the conductor temperature of each cable loop does not exceed the corresponding allowable conductor temperature, the candidate path number and candidate hole position number in the currently selected remaining combination are determined as the pipe laying path and hole position of each cable loop.

[0069] When all combinations are eliminated, the system outputs a message indicating that no feasible combinations exist. After adding candidate paths, adjusting the number of candidate holes, or improving the heat dissipation conditions of the pipe section, the design process is repeated.

[0070] Example 2:

[0071] Taking an underground cable duct section with twelve candidate borehole locations as an example, after rainfall, the measured soil moisture content at the top of the duct was 0.18, and the measured soil temperature was 26 degrees Celsius, meeting the recovery conditions of a moisture content of 0.16 and a temperature of 28 degrees Celsius. At the bottom of the duct, the measured soil moisture content was 0.08, and the measured soil temperature was 34 degrees Celsius, not yet meeting the recovery conditions. Based on this, the pseudo-thermal recovery time window was determined to be from 2 PM to 8 PM on the same day, forming the first deep unrecovered area at the bottom of the duct.

[0072] After a fault occurs in the first cable circuit, the load is transferred to the second cable circuit. In the first combination, the first cable circuit occupies the ninth candidate hole position, and the second cable circuit occupies the tenth candidate hole position. Both the ninth and tenth candidate hole positions are affected by the first deep unrecovered area.

[0073] Calculations showed that the candidate additional temperature rise of the first cable circuit exceeded 2 degrees Celsius continuously from 3 PM to 5 PM, and the candidate additional temperature rise of the second cable circuit exceeded 2 degrees Celsius continuously from 3:30 PM to 7 PM, with the two temperature rise periods overlapping. Therefore, the first and second cable circuits were classified into the same thermal coupling circuit group.

[0074] Since both cable loops in the same thermal coupling loop group in the first combination occupy candidate hole positions affected by the first deep unrecovered area, and the number of loops in the same area of ​​the first deep unrecovered area is two, the first combination is eliminated.

[0075] In the second combination, the first cable loop is changed to occupy the third candidate hole position which is not affected by the first deep unrecovered area, while the second cable loop still occupies the tenth candidate hole position. The number of loops in the same area of ​​the first deep unrecovered area is one, so the second combination is retained.

[0076] In the third combination, the maximum value of all candidate additional temperature rise sequences is less than that of the second combination, so the third combination is selected first for conductor temperature verification. However, the highest conductor temperature of the second cable loop in the third combination exceeds the corresponding allowable conductor temperature, so the third combination is eliminated.

[0077] The conductor temperature was rechecked using the second combination. The conductor temperatures of all cable loops in the second combination did not exceed the corresponding allowable conductor temperatures. Therefore, the candidate path numbers and candidate hole position numbers in the second combination were determined as the conduit paths and hole positions for each cable loop.

[0078] Therefore, this invention identifies pseudo-thermal recovery time windows and deep unrecovered areas, compares conductor temperatures under measured soil conditions with those under recovered soil conditions, generates candidate additional temperature rise sequences, and then divides thermally coupled circuit groups based on the transfer relationship, temperature rise period, and deep unrecovered areas. This avoids multiple cable circuits with transfer relationships being concentrated near the same deep unrecovered area, reducing the risk of conductor temperature exceeding limits during load transfer.

[0079] The above method can be executed by a computer device. The computer device includes a processor and a memory, in which a computer program is stored. When the processor executes the computer program, it completes the identification of deep unrecovered regions, the calculation of conductor temperature, the generation of candidate additional temperature rise sequences, the division of thermally coupled loop groups, and the determination of pipe routing paths and hole positions.

[0080] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the design method for underground cable duct distribution in municipal power engineering and the inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for designing the distribution of underground cable ducts in municipal power engineering, characterized in that, Includes the following steps: Acquire deep unrecovered areas, pseudo-thermal recovery time windows, cable loop load values ​​at each acquisition time, out-of-service cable loop numbers, receiving cable loop numbers, and combinations of each cable loop number with candidate path numbers and candidate hole location numbers; For each combination, based on the cable loop load value at each acquisition time, the measured conductor temperature and the recovered conductor temperature at each acquisition time within the pseudo-thermal recovery time window are calculated according to the measured soil moisture content, measured soil temperature, and recovered moisture content and recovered temperature. The candidate additional temperature rise sequence is generated by subtracting the recovered conductor temperature from the measured conductor temperature. Based on the out-of-service cable circuit number and the receiving cable circuit number, cable circuits that are affected by the same deep unrecovered area and whose candidate additional temperature rise exceeds the preset temperature rise threshold time periods are divided into thermal coupling circuit groups. Eliminate combinations of two or more cable loops in the same thermal coupling loop group that pass through the same deep unrecovered area or occupy candidate hole positions affected by the deep unrecovered area, and determine the pipe routing and hole positions for each cable loop; Methods for obtaining deep unrecovered areas and pseudo-thermal recovery time windows include: The measured soil moisture content, measured soil temperature, and spatial location at the top, side, and bottom of the pipe were collected at each sampling time. The time interval between the time when the measured soil moisture content at the top of the pipe is not lower than the restored moisture content and the measured soil temperature is not higher than the restored temperature, but the time when the side or bottom of the pipe does not simultaneously meet the above conditions, and the time when the side and bottom of the pipe both meet the above conditions, is defined as the false thermal recovery time window. Connect adjacent spatial locations within the pseudo-thermal recovery time window where the measured soil moisture content is lower than the recovery moisture content or the measured soil temperature is higher than the recovery temperature to form a deep unrecovered area; Methods for dividing thermally coupled loop groups include: The range of time intervals during which the candidate additional temperature rise continuously exceeds the preset temperature rise threshold is defined as the temperature rise period. The circuit numbering of the out-of-service cable circuit and the circuit numbering of the receiving cable circuit are combined into a circuit numbering pair. Circuit numbering pairs that overlap in temperature rise period and whose candidate paths pass through the same deep unrecovered area or whose candidate hole positions are affected by the same deep unrecovered area are retained. Group loop number pairs with the same cable loop number into the same set, repeatedly merge sets with the same cable loop number, and divide the cable loop numbers contained in each set into a thermally coupled loop group.

2. The method for designing the distribution of underground cable ducts in municipal power engineering according to claim 1, characterized in that, Methods for determining the conduit routes and hole locations for each cable loop include: The number of different cable loop numbers that pass through each deep unrecovered area or occupy candidate hole positions affected by that deep unrecovered area within the same thermal coupling loop group in each combination is counted to obtain the number of loops in the same area; Eliminate combinations with at least two loops in the same area; Extract the maximum value of all candidate additional temperature rise sequences in each remaining combination, and determine the candidate path number and candidate hole number in the remaining combination with the smallest maximum value as the pipe routing path and hole position for each cable loop.

3. The method for designing the distribution of underground cable ducts in municipal power engineering according to claim 2, characterized in that, Methods for obtaining the number of loops in the same area include: For each thermally coupled loop group and each deep unrecovered region in each combination, at each acquisition time of the pseudo-thermal recovery time window, select the cable loop number where the candidate additional temperature rise exceeds the preset temperature rise threshold and the candidate path passes through the deep unrecovered region or the candidate hole position is affected by the deep unrecovered region. The number of different cable loop numbers selected at each acquisition time was counted, and the maximum value was taken as the number of loops in the same area corresponding to the deep unrecovered area.

4. The method for designing the distribution of underground cable ducts in municipal power engineering according to claim 1, characterized in that, Methods for calculating conductor temperature include: Based on the relationship between soil moisture content and soil thermal resistivity, the measured soil moisture content and the restored soil moisture content are converted into the measured soil thermal resistivity and the restored soil thermal resistivity, respectively. A thermal resistance and thermal capacity network is established using cable conductors, ducts and soil as nodes, according to the candidate path number and candidate hole number in each combination. Keeping the initial conductor temperature, cable loop load value, and soil thermal resistivity outside the deep unrecovered area the same, the measured soil thermal resistivity, measured soil temperature, and restored soil thermal resistivity and restored temperature are assigned to the deep unrecovered area respectively, and the conductor temperature is calculated twice through the thermal resistance and thermal capacity network.

5. The method for designing the distribution of underground cable ducts in municipal power engineering according to claim 1, characterized in that, Methods for generating candidate additional temperature rise sequences include: The conductor temperature calculated based on the measured soil moisture content and measured soil temperature is determined as the measured conductor temperature, and the conductor temperature calculated based on the recovered moisture content and recovered temperature is determined as the recovered conductor temperature. The measured conductor temperature of the same cable loop in the same combination at each acquisition time is subtracted from the recovered conductor temperature, and the difference is arranged according to the acquisition time to generate a candidate additional temperature rise sequence.

6. The method for designing the distribution of underground cable ducts in municipal power engineering according to claim 1, characterized in that, Methods for generating combinations of cable loop numbers, candidate path numbers, and candidate hole location numbers include: Obtain the access start and end points of each cable loop, the maximum number of cable loops that each candidate path can accommodate, and the existing cable loop numbers in each candidate hole position. For each cable loop, select candidate paths to connect the corresponding access start point and access end point, and select candidate hole positions from the candidate paths that do not have existing cable loop numbers recorded. The combination of cable loop number, candidate path number, and candidate hole position number is used to eliminate combinations in which more than two cable loops are assigned to the same candidate hole position or the number of cable loops assigned to the same candidate path exceeds the maximum number of cable loops.

7. The method for designing the distribution of underground cable ducts in municipal power engineering according to claim 4, characterized in that, Methods for determining the influence of each deep unrecovered region on candidate paths and candidate aperture locations include: Each deep unrecovered region is sequentially identified as a target deep unrecovered region; Assign measured soil thermal resistivity and measured soil temperature to all deep unrestored areas and calculate the full measured conductor temperature; keep other deep unrestored areas unchanged, replace only the target deep unrestored area with restored soil thermal resistivity and restored temperature, and calculate the single-area restored conductor temperature; The additional temperature rise of the target area is obtained by subtracting the single-zone recovered conductor temperature from the total measured conductor temperature. The candidate paths and candidate hole positions corresponding to the cable loops whose additional temperature rise in the target area exceeds the preset temperature rise threshold are determined as being affected by the target deep unrecovered area.

8. The method for designing the distribution of underground cable ducts in municipal power engineering according to claim 2, characterized in that, The methods for determining the candidate path number and candidate hole position number as the duct path and hole position for each cable loop include: Obtain the allowable conductor temperature for each cable loop; Based on the measured soil moisture content and measured soil temperature, calculate the conductor temperature of the remaining selected combinations at each sampling time within the pseudo-thermal recovery time window; When the temperature of any conductor exceeds the corresponding allowable conductor temperature, the selected remaining combination is discarded, and the remaining combination with the smallest maximum value of the candidate additional temperature rise sequence is selected again, until the conductor temperature of each cable loop does not exceed the corresponding allowable conductor temperature.

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