Length estimation method for secondary cable of transformer substation

Abstract

The invention provides a method for estimating the length of a secondary cable of a transformer substation, and the method comprises the following steps: space division and working principle division: dividing the transformer substation into a plurality of fields according to the space layout, and dividing the fields into a plurality of intervals according to the working principle; inputting basic data of the transformer substation, wherein the basic data comprises basic information such as total capacity, voltage class and main wiring system of the transformer substation; counting the number of cables or optical cables: counting the number of cables or optical cables of different specifications in each interval according to design and specific project requirements; estimating the length of the cable or the optical cable: calculating the length of the cable or the optical cable in each interval by using a related formula; and outputting a calculation result: summarizing and outputting the calculated lengths of the cable or the optical cable. According to the method, the actual length of the cable in a complex laying environment can be truly reflected, the estimation precision is remarkably improved, the operation safety and reliability of the transformer substation are enhanced, the operation and maintenance cost in the whole life cycle can be reduced, and the overall economic benefit of the transformer substation is improved.

Description

Technical Field

[0001] The invention relates to the field of cable length estimation, and in particular to a method for estimating the length of a secondary cable in a transformer substation. Background Art

[0002] Substations are important nodes in the power system, in which secondary cables not only carry the transmission of protection, measurement, control, communication and other signals, but also directly affect the automation level, fault diagnosis and processing capabilities of substations. However, the laying and management of secondary cables face many challenges, especially in terms of length estimation. In the existing technology, the problems existing in the estimation of secondary cable length and the limitations of the existing technology mainly include the following aspects:

[0003] Traditional secondary cable length estimation methods are often based on empirical formulas, simple straight-line distance measurements, or rough drawing ratio calculations, which fail to fully consider the various complex factors in the cable laying process, such as corner bends, fixed point spacing and sag, end wiring allowances, special environmental corrections, etc. This simplified processing can easily lead to a large deviation between the estimated results and actual needs, resulting in excessive or insufficient cable procurement, which in turn leads to material waste, construction delays, cost overruns and other problems.

[0004] The layout of equipment inside the substation is complex, and the cable laying path often includes various special environments such as corners, turns, wall penetration, bridge crossing, and laying along bridges. Existing estimation methods often ignore the impact of these special environments on cable length and do not provide targeted correction calculation methods.

[0005] The performance parameters of the cable (such as the minimum bending radius, linear expansion coefficient, etc.) and the laying specifications (such as the suspension point spacing, tension requirements, etc.) have a significant impact on the cable length. However, the existing estimation methods often ignore the impact of these parameters on the length and do not incorporate them into the calculation model, resulting in the estimation results not accurately reflecting the actual laying requirements.

[0006] During operation, the cable will expand and contract due to temperature changes, and a corresponding length needs to be reserved to accommodate this change. In addition, the wiring inside the junction box and the production of terminal connectors will also consume a certain length of cable. Existing estimation methods often ignore these factors, resulting in incomplete calculation of cable length and affecting the accuracy of project implementation.

[0007] A Chinese patent with publication number CN105811320A discloses "a method for estimating the length of a secondary cable or optical cable in a substation". The method divides the substation into several sites, calculates the lengths between several intervals one by one, and finally accumulates them. Although this method can quickly calculate the length, it does not take into account the errors caused by cable bending, wall penetration, etc.

[0008] At present, there is a lack of systematic tools and methods for accurately estimating the length of secondary cables in substations on the market. Most projects still rely on manual calculations or empirical judgments, which are inefficient and prone to errors. At the same time, although the existing engineering design software has certain cable laying functions, it often has deficiencies in terms of cable length estimation accuracy and adaptability to special environments. Summary of the invention

[0009] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for estimating the length of a secondary cable in a substation to solve the problems raised in the above background technology. The present invention improves the accuracy of estimation by separately calculating the length between cable bending and cable falling.

[0010] In order to achieve the above object, the present invention is implemented through the following technical solution: a method for estimating the length of a secondary cable in a substation, comprising the following steps:

[0011] S1. According to the actual spatial layout of the substation, the substation is divided into multiple areas with specific functions, such as high-voltage switchgear area, relay protection and control room area, AC / DC power system area, etc. Within each area, the relevant equipment is further divided into logically clear and functionally independent intervals based on the working principle and electrical connection requirements of the equipment, such as circuit breaker intervals, protection screen intervals, AC / DC power screen intervals, etc.;

[0012] S2. Collect and enter basic information of the substation, including but not limited to total installed capacity, voltage level, main wiring system form, equipment model and configuration, secondary equipment interface standard and other key data, to provide accurate basic parameters for subsequent cable or optical cable length estimation;

[0013] S3. According to the design drawings and project technical specifications, detailed statistics are made on the types, specifications, and quantities of secondary cables or optical cables required to be connected between each compartment, including but not limited to control cables, signal cables, communication optical cables, etc. Ensure that the statistics are comprehensive and match the actual equipment interface to provide a complete data set for subsequent length calculations;

[0014] S4. Use the cable or optical cable length calculation model to estimate the length of each cable or optical cable to ensure that the result is close to the actual demand;

[0015] S5. Summarize the estimated lengths of all cables or optical cables and generate a detailed cable or optical cable length list, which includes not only the starting and ending points, specifications, and quantity of each cable or optical cable, but also the estimated length value.

[0016] Furthermore, the step S1 specifically includes the following steps:

[0017] S1-1. Obtain a detailed substation layout diagram, including building structure, equipment location, channel layout, cable trench direction and other information, as the basis for space division.

[0018] S1-2. Based on the overall functions and equipment distribution of the substation, identify areas with obvious physical boundaries and functional characteristics, such as high-voltage switchgear area, relay protection and control room area, AC and DC power supply system area, etc. These areas usually correspond to the main electrical function modules of the substation, and have relatively concentrated equipment layout on the floor plan.

[0019] S1-3. On the substation plan, the boundaries of each area shall be clearly marked with lines, using physical partitions such as building walls, partitions, fences, etc. as boundaries, or based on the actual situation of centralized equipment layout.

[0020] S1-4. For each identified site, further refine it into logically clear and functionally independent intervals according to the working principle and electrical connection requirements of the equipment, analyze the working relationship between the equipment, study the electrical connection, control logic, signal transmission path, etc. between the equipment in the site, and clarify the working coordination relationship between the equipment.

[0021] S1-5. Divide and name the intervals. In the field, according to the determined division principle, combine the equipment into logically independent and functionally related intervals. To facilitate subsequent design and construction, give each interval a clear name, such as "No. 1 main transformer high-voltage side circuit breaker interval", "220kV busbar protection screen interval", "DC operating power supply screen interval", etc.

[0022] S1-6. Draw an interval layout diagram. Based on the site plan, describe in detail the specific location, arrangement and electrical connection relationship of the equipment in each interval to form an interval layout diagram.

[0023] Furthermore, the step S2 specifically includes the following steps:

[0024] S2-1. Clarify the required information categories. Total installed capacity: the total power generation or transmission capacity of the substation, usually in kilowatts (kW) or megawatts (MW). Voltage level: the rated voltage used by each part of the substation (such as high-voltage incoming lines, main transformers, feeders, etc.), such as 110kV, 220kV, 35kV, 10kV, etc. Main connection system form: the main circuit connection method on the high-voltage side and low-voltage side of the substation, such as single busbar segmentation, double busbar, bridge connection, angle connection, etc. Equipment model and configuration: including the specific model, quantity, rated parameters and installation location of primary equipment such as transformers, circuit breakers, disconnectors, current / voltage transformers, lightning arresters, grounding switches, capacitors, reactors, etc. Secondary equipment interface standards: communication protocols, interface standards (such as IEC 61850, IEC 60870-5-103, etc.), signal types (analog, digital, GOOSE, SV, etc.) and terminal configurations of secondary equipment such as protection devices, measurement and control devices, metering devices, and automation equipment.

[0025] S2-2. On-site investigation and data collection: Conduct a detailed investigation at the substation site to verify the equipment installation location, actual operating status, sign information, etc., and record any discrepancies with the drawings.

[0026] S2-3. Establish an information database and create a spreadsheet or database template suitable for storing basic information of the substation, including fields corresponding to the above-mentioned types of information.

[0027] S2-4. Accurately enter the collected information into the corresponding fields to ensure the integrity and consistency of the data. Perform preliminary verification on the entered data, such as checking whether the value range is reasonable, whether the logical relationship is correct, whether the equipment configuration is consistent with the main wiring diagram, etc., and correct any problems in a timely manner.

[0028] S2-5. Draw or update the cable route map based on the substation layout and equipment location, and clarify the cable direction, laying method (overhead, direct burial, pipe, cable trench, etc.) and the location of intermediate joints and terminal joints. Mark cable information: Mark the starting and ending point equipment, cable model, cross-sectional area, length and other information of each cable on the cable route map to ensure that it is consistent with the equipment location information in the equipment configuration table.

[0029] S2-6. Identify the communication protocols, interface standards and versions used by each secondary device and record them in the database. Draw an interface diagram: Draw an interface connection diagram between secondary devices, indicating the signal type, transmission direction, interface terminal number, etc., to ensure that it is consistent with the device interface configuration.

[0030] S2-7. Count the interface cable requirements: Based on the interface connection diagram, estimate the type, quantity, and length of the required interface cables such as optical fiber, coaxial cable, and twisted pair, and provide data for optical or electrical cable length estimation.

[0031] Furthermore, the step S3 specifically includes the following steps:

[0032] S3-1. Be familiar with design drawings and technical specifications, and study design drawings: Carefully read the design drawings such as the primary and secondary system diagrams of the substation, the panel layout diagram, and the cable laying diagram, and understand the location of each compartment (such as protection screen, measurement and control screen, metering screen, smart terminal screen, etc.), the internal equipment layout, and the connection relationship between them. Interpret technical specifications: In-depth understanding of the relevant clauses in the project technical specifications regarding secondary equipment selection, interface standards, cable selection, laying requirements, etc., to ensure that the statistical work meets the requirements of the specifications.

[0033] S3-2. Identify the secondary equipment interface and mark the interface type: mark the input and output interface type of each secondary equipment (such as relays, protection devices, measurement and control devices, intelligent terminals, switches, etc.) on the drawing.

[0034] S3-3. According to the interface type and function, the required cables are divided into control cables, signal cables, communication optical cables, power cables and other categories.

[0035] S3-4. Draw a detailed secondary cable connection diagram on the drawing, clearly marking the starting point, end point, interface number, cable type and specification of each cable. Count the number of cables: Count each type of cable one by one, including trunk cables, branch cables, jumpers, etc., to ensure that no necessary cables are missed.

[0036] S3-5. Compare the statistical cable information with the actual interfaces of the equipment one by one to confirm that the cable type and specifications fully match the interface requirements without omissions or errors. If inconsistencies or errors are found, adjust the cable type, specifications or quantity in a timely manner, and update the cable connection diagram and statistical list.

[0037] S3-6. Based on the statistical results, prepare a detailed secondary cable inventory, which should include cable number, type, specification, starting device and interface, terminal device and interface, length (to be calculated later), quantity and other information.

[0038] Furthermore, the step S4 specifically includes the following steps:

[0039] S4-1. Obtain design drawings containing detailed information such as the location of equipment in each compartment, the layout of the cabinets, and the wiring path, as the basic data for calculating the length of the cable or optical cable. Determine the type and specification of the cable or optical cable: Refer to the cable inventory to clarify the type, specification, starting and ending equipment, and interface information of each cable or optical cable.

[0040] S4-2. Calculate the total length Y1 of the straight section.

[0041] Furthermore, in S4, the sites C1, C2, ... n Represents the venues connected by straight lines, with intervals T1, T2…T m represents different intervals and S1, S2…S m Represents the number of intervals corresponding to different intervals. The distance between each venue is represented by a one-dimensional array [DC], then:

[0042] [DC]=[LC 11 , L.C. 12 ,…LC 1n , L.C. 22 , L.C. 23 ,…LC (n-1)(n-1) , L.C. nn ]

[0043] The total straight-line distance is:

[0044]

[0045] Where m is the number of intervals, n is the number of sites, LP ij (i≠j) represents the straight-line distance between the various sites;

[0046] S4-3. Calculate the reserved Y2 for corner bending

[0047] Determine the bending radius: Refer to the cable or optical cable laying specifications to check the minimum allowable bending radius of cables or optical cables of different diameters and types at various corners (such as 90°, 45°, etc.).

[0048] Single bend length calculation formula: For a specific corner (such as 90° or 45°), the actual length of the bend (L_bend) can be calculated by the following formula:

[0049]

[0050] in:

[0051] θ is the turning angle, in degrees (°); R is the minimum allowable bending radius of the cable or optical cable at this angle, in meters (m); π is the circumference of a circle, which is approximately 3.14159.

[0052] For each corner or turn on the total cable or total optical cable path, the bending length (L_bend_i) is calculated according to the above formula, where i represents the i-th turning point.

[0053] Sum up all the individual bend lengths to get the total bend reserve length (Y2):

[0054]

[0055] Where n is the total number of turning points or turns on the total path.

[0056] Further, S4-4, consider the fixed point spacing and slack

[0057] Determine the spacing between suspension points: set a reasonable spacing between suspension points in accordance with the cable or optical cable laying specifications and in combination with site conditions.

[0058] Calculate sag: Use parameters such as the weight of the cable or optical cable, the distance between the suspension points, and the acceleration of gravity to calculate the degree of sag (sag) of the cable or optical cable under its own weight.

[0059] The sag degree (sag) of the cable or optical cable under its own weight can be calculated according to the following formula:

[0060]

[0061] Where: L s is the sag (droop length), in meters (m); W is the weight of the cable or optical cable per unit length, in Newton per meter (N / m); l is the suspension point spacing, in meters (m); l span It is the length of the actual hanging part of the cable or optical cable between two adjacent hanging points (taking into account the bending reserve, etc.), measured in meters (m); T is the tension of the cable or optical cable (usually a certain proportion of the maximum allowable tension, such as 50% to 70%), measured in Newtons (N); α is the angle between the cable or optical cable and the vertical direction, that is, the hanging angle, measured in radians (rad).

[0062] Reserve length for thermal expansion and contraction: Refer to the linear expansion coefficient of the cable or optical cable material, calculate the length change caused by thermal expansion and contraction according to the maximum temperature difference and the length of the straight segment, and reserve the corresponding length.

[0063] Electrical cables or optical cables will expand and contract under temperature changes, so it is necessary to reserve a corresponding length based on the linear expansion coefficient of the material, the maximum temperature difference, and the length of the straight segment. The calculation formula is as follows:

[0064] L t =α×ΔT×L s

[0065] in:

[0066] L t is the length reserved due to thermal expansion and contraction, in meters (m); α is the linear expansion coefficient of the cable or optical cable material, in units of percentage change in length per degree Celsius (℃); ΔT is the maximum temperature difference that the cable or optical cable may experience, in degrees Celsius (℃); L s It is the length of the straight cable or optical cable that needs to consider the thermal expansion and contraction effects, measured in meters (m).

[0067] For each straight cable on the entire cable or optical cable path, the length of the straight line segment is calculated according to the above formula and the corresponding length is reserved, where i represents the number of the i-th straight line.

[0068] Sum all the straight line length reservations to get the total straight line length reservation (Y3):

[0069]

[0070] Where n is the total number of straight cables in the total path.

[0071] S4-5. Add the length of the straight section, the corner bend reserve, the fixed point spacing and the sag to obtain the estimated length L of each cable or optical cable. sum .

[0072] L sum =Y1+Y2+Y3

[0073] Furthermore, the cable or optical cable length calculation model in S4 includes the following factors: straight section length, corner bend reservation, fixed point spacing and sag.

[0074] Furthermore, in the length of straight sections, the straight-line distance between each interval is accurately measured or calculated according to the equipment layout diagram; in the corner bend reservation, the bending radius and reserved length of various corners and turns are calculated according to the cable or optical cable laying specifications; in the fixed point spacing and sag, the suspension point spacing when the cable or optical cable is laid, the degree of sagging caused by gravity, and the thermal expansion and contraction caused by temperature changes are considered.

[0075] Beneficial effects of the present invention:

[0076] 1. The substation secondary cable length estimation method comprehensively considers multiple factors such as the length of the straight section, corner bend reservation, fixed point spacing and sag, and constructs a comprehensive and accurate cable length calculation model. This model can truly reflect the actual length of the cable in a complex laying environment and significantly improve the estimation accuracy.

[0077] 2. The length estimation method of the secondary cable of the substation strictly follows the cable laying specifications, fully considering the cable's minimum bending radius, suspension point spacing, tension requirements and other performance parameters, ensuring that the cable laying meets both electrical performance requirements and mechanical strength and safety standards. In addition, the accurate calculation of thermal expansion and contraction effects and wiring margins helps prevent the electrical performance degradation or mechanical damage of the cable due to excessive stretching or relaxation, enhancing the safety and reliability of substation operation.

[0078] 3. The method for estimating the length of the secondary cable of the substation uses accurate cable length estimation to help avoid over-purchasing, reduce inventory backlogs, and improve capital turnover efficiency. At the same time, the accurately matched cable length can maximize the use of cable resources, reduce waste generation, and is conducive to environmental protection and resource conservation. In the long run, the accurate estimation method helps to reduce the operation and maintenance costs throughout the life cycle and improve the overall economic benefits of the substation. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 The present invention is a flow chart showing the appearance of a method for estimating the length of a secondary cable in a substation. DETAILED DESCRIPTION

[0080] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0081] See also Figure 1 The present invention provides the following technical solution: a method for estimating the length of a secondary cable in a substation, specifically comprising the following steps:

[0082] S1: According to the actual spatial layout of the substation, the substation is divided into multiple areas with specific functions, such as high-voltage switchgear area, relay protection and control room area, AC / DC power system area, etc. Within each area, the relevant equipment is further divided into logically clear and functionally independent intervals, such as circuit breaker intervals, protection screen intervals, AC / DC power screen intervals, etc., based on the working principle of the equipment and electrical connection requirements.

[0083] S2: Collect and enter basic information of the substation, including but not limited to total installed capacity, voltage level, main connection system form, equipment model and configuration, secondary equipment interface standard and other key data, to provide accurate basic parameters for subsequent cable or optical cable length estimation.

[0084] S3: According to the design drawings and project technical specifications, detailed statistics are made on the types, specifications, and quantities of secondary cables or optical cables required to be connected between each compartment, including but not limited to control cables, signal cables, communication optical cables, etc. Ensure that the statistics are comprehensive and match the actual equipment interface to provide a complete data set for subsequent length calculations.

[0085] S4: The cable or optical cable length calculation model unique to the present invention is adopted, which comprehensively considers the following factors:

[0086] 1. Length of straight section: According to the equipment layout diagram, accurately measure or calculate the straight distance between each interval;

[0087] 2. Corner bend reserve: Calculate the bending radius and reserved length of various corners and turns according to the cable or optical cable laying specifications;

[0088] 3. Spacing and sag of fixed points: Consider the spacing of suspension points when laying cables or optical cables, the sagging degree (sag) caused by gravity, and the allowance for thermal expansion and contraction caused by temperature changes;

[0089] Through the above model, the estimated length of each cable or optical cable is calculated to ensure that the result is close to actual needs.

[0090] S5: Summarize the estimated lengths of all cables or optical cables to generate a detailed cable or optical cable length list, which includes not only the starting and ending points, specifications, and quantity of each cable or optical cable, but also the estimated length value.

[0091] As an embodiment of the present application, the step S1 specifically includes:

[0092] S11: Obtain a detailed substation layout diagram, including building structure, equipment location, channel layout, cable trench direction and other information as the basis for space division.

[0093] S12: Based on the overall functions and equipment distribution of the substation, identify areas with obvious physical boundaries and functional characteristics, such as high-voltage switchgear area, relay protection and control room area, AC and DC power supply system area, etc. These areas usually correspond to the main electrical function modules of the substation, and have relatively concentrated equipment layout on the floor plan.

[0094] S13: On the substation layout plan, the boundaries of each area shall be clearly marked with lines using physical partitions such as building walls, partitions, fences, etc., or based on the actual situation of centralized equipment layout.

[0095] S14: For each identified site, further refine it into logically clear and functionally independent intervals according to the working principle and electrical connection requirements of the equipment, analyze the working relationship between the equipment, study the electrical connection, control logic, signal transmission path, etc. between the equipment in the site, and clarify the working coordination relationship between the equipment.

[0096] S15: Divide and name the bays. In the field, according to the determined division principle, combine the equipment into logically independent and functionally related bays. To facilitate subsequent design and construction, give each bay a clear name, such as "No. 1 main transformer high-voltage side circuit breaker bay", "220kV busbar protection screen bay", "DC operating power supply screen bay", etc.

[0097] S16: Draw an interval layout diagram. Based on the site plan, the specific location, arrangement and electrical connection relationship of the equipment in each interval are detailed to form an interval layout diagram.

[0098] As an embodiment of the present application, step S2 specifically includes:

[0099] S21: Specify the required information categories. Total installed capacity: the total power generation or transmission capacity of the substation, usually in kilowatts (kW) or megawatts (MW). Voltage level: the rated voltage used by each part of the substation (such as high-voltage incoming lines, main transformers, feeders, etc.), such as 110kV, 220kV, 35kV, 10kV, etc. Main connection system form: the main circuit connection method on the high-voltage side and low-voltage side of the substation, such as single busbar segmentation, double busbar, bridge connection, angle connection, etc. Equipment model and configuration: including the specific model, quantity, rated parameters and installation location of primary equipment such as transformers, circuit breakers, disconnectors, current / voltage transformers, lightning arresters, grounding switches, capacitors, reactors, etc. Secondary equipment interface standards: communication protocols, interface standards (such as IEC 61850, IEC 60870-5-103, etc.), signal types (analog, digital, GOOSE, SV, etc.) and terminal configurations of secondary equipment such as protection devices, measurement and control devices, metering devices, and automation equipment.

[0100] S22: On-site investigation and data collection On-site inspection: Conduct detailed investigation at the substation site to verify the equipment installation location, actual operating status, sign information, etc., and record any discrepancies with the drawings.

[0101] S23: Establish an information database, and create a spreadsheet or database template suitable for storing basic information of the substation, including fields corresponding to the above-mentioned various types of information.

[0102] S24: Accurately enter the collected information into the corresponding fields to ensure the integrity and consistency of the data. Perform preliminary verification on the entered data, such as checking whether the value range is reasonable, whether the logical relationship is correct, whether the equipment configuration is consistent with the main wiring diagram, etc., and correct any problems found in a timely manner.

[0103] S25: Draw or update the cable route map based on the substation layout and equipment location, and clarify the cable direction, laying method (overhead, direct burial, pipe, cable trench, etc.) and the location of intermediate joints and terminal joints. Mark cable information: Mark the starting and ending point equipment, cable model, cross-sectional area, length and other information of each cable on the cable route map to ensure that it is consistent with the equipment location information in the equipment configuration table.

[0104] S26: Identify the communication protocols, interface standards and versions used by each secondary device and record them in the database. Draw an interface diagram: Draw an interface connection diagram between secondary devices, indicating the signal type, transmission direction, interface terminal number, etc., to ensure that it is consistent with the device interface configuration.

[0105] S27: Count interface cable requirements: Estimate the types, quantities, and lengths of required optical fiber, coaxial cable, twisted pair, and other interface cables based on the interface connection diagram, and provide data for optical or electrical cable length estimation.

[0106] As an embodiment of the present application, step S3 specifically includes:

[0107] S31: Be familiar with design drawings and technical specifications, and study design drawings: Carefully read the substation electrical primary and secondary system diagrams, panel cabinet layout diagrams, cable laying diagrams and other design drawings, and understand the location of each compartment (such as protection screen, measurement and control screen, metering screen, smart terminal screen, etc.), the internal equipment layout and the connection relationship between them. Interpret technical specifications: In-depth understanding of the project technical specifications on secondary equipment selection, interface standards, cable selection, laying requirements and other related clauses to ensure that the statistical work meets the requirements of the specifications.

[0108] S32: Identify the secondary device interface and mark the interface type: Mark the input and output interface type of each secondary device (such as relays, protection devices, measurement and control devices, intelligent terminals, switches, etc.) on the drawing.

[0109] S33: According to the interface type and function, the required cables are divided into categories such as control cables, signal cables, communication optical cables, and power cables.

[0110] S34: Draw a detailed secondary cable connection diagram on the drawing, clearly marking the starting point, end point, interface number, cable type and specification of each cable. Count the number of cables: Count each type of cable one by one, including trunk cables, branch cables, jumpers, etc., to ensure that no necessary cables are missed.

[0111] S35: Compare the counted cable information with the actual interfaces of the equipment one by one to confirm that the cable type and specifications fully match the interface requirements without omissions or errors. If inconsistencies or errors are found, adjust the cable type, specifications or quantity in a timely manner, and update the cable connection diagram and statistical list.

[0112] S36: Based on the statistical results, prepare a detailed secondary cable inventory, which should include cable number, type, specification, starting device and interface, terminal device and interface, length (to be calculated later), quantity and other information.

[0113] As an embodiment of the present application, step S4 specifically includes:

[0114] S41: Obtain design drawings containing detailed information such as the location of equipment in each compartment, the layout of the cabinets, and the wiring path as the basic data for calculating the length of the cable or optical cable. Determine the type and specification of the cable or optical cable: Refer to the cable inventory to clarify the type, specification, starting and ending equipment, and interface information of each cable or optical cable.

[0115] S42: Calculate the total length of the straight section Y1

[0116] In S4, the sites C1, C2…C n Represents the venues connected by straight lines, with intervals T1, T2…T m represents different intervals and S1, S2…S m Represents the number of intervals corresponding to different intervals. The distance between each venue is represented by a one-dimensional array [DC], then:

[0117] [DC]=[LC 11 , L.C. 12 ,…LC 1n , L.C. 22 , L.C. 23 ,…LC (n-1)(n-1) , L.C. nn ]

[0118] The total straight-line distance is:

[0119]

[0120] Where m is the number of intervals, n is the number of sites, LP ij (i≠j) represents the straight-line distance between the various sites;

[0121] S43: Calculate the corner bend reserve Y2

[0122] Determine the bending radius: Refer to the cable or optical cable laying specifications to check the minimum allowable bending radius of cables or optical cables of different diameters and types at various corners (such as 90°, 45°, etc.).

[0123] Single bend length calculation formula: For a specific corner (such as 90° or 45°), the actual length of the bend (L_bend) can be calculated by the following formula:

[0124]

[0125] in:

[0126] θ is the turning angle, in degrees (°); R is the minimum allowable bending radius of the cable or optical cable at this angle, in meters (m); π is the circumference of a circle, which is approximately 3.14159.

[0127] For each corner or turn on the total cable or total optical cable path, the bending length (L_bend_i) is calculated according to the above formula, where i represents the i-th turning point.

[0128] Sum up all the individual bend lengths to get the total bend reserve length (Y2):

[0129]

[0130] Where n is the total number of turning points or turns on the total path.

[0131] S44: Considering fixed point spacing and slack

[0132] Determine the spacing between suspension points: set a reasonable spacing between suspension points in accordance with the cable or optical cable laying specifications and in combination with site conditions.

[0133] Calculate sag: Use parameters such as the weight of the cable or optical cable, the distance between the suspension points, and the acceleration of gravity to calculate the degree of sag (sag) of the cable or optical cable under its own weight.

[0134] The sag degree (sag) of the cable or optical cable under its own weight can be calculated according to the following formula:

[0135]

[0136] Where: L s is the sag (droop length), in meters (m); W is the weight of the cable or optical cable per unit length, in Newton per meter (N / m); l is the suspension point spacing, in meters (m); l span It is the length of the actual hanging part of the cable or optical cable between two adjacent hanging points (taking into account the bending reserve, etc.), measured in meters (m); T is the tension of the cable or optical cable (usually a certain proportion of the maximum allowable tension, such as 50% to 70%), measured in Newtons (N); α is the angle between the cable or optical cable and the vertical direction, that is, the hanging angle, measured in radians (rad).

[0137] Reserve length for thermal expansion and contraction: Refer to the linear expansion coefficient of the cable or optical cable material, calculate the length change caused by thermal expansion and contraction according to the maximum temperature difference and the length of the straight segment, and reserve the corresponding length.

[0138] Electrical cables or optical cables will expand and contract under temperature changes, so it is necessary to reserve a corresponding length based on the linear expansion coefficient of the material, the maximum temperature difference, and the length of the straight segment. The calculation formula is as follows:

[0139] L t =α×ΔT×L s

[0140] in:

[0141] L t is the length reserved due to thermal expansion and contraction, in meters (m); α is the linear expansion coefficient of the cable or optical cable material, in units of percentage change in length per degree Celsius (℃); ΔT is the maximum temperature difference that the cable or optical cable may experience, in degrees Celsius (℃); L sIt is the length of the straight cable or optical cable that needs to consider the thermal expansion and contraction effects, measured in meters (m).

[0142] For each straight cable on the entire cable or optical cable path, the length of the straight line segment is calculated according to the above formula and the corresponding length is reserved, where i represents the number of the i-th straight line.

[0143] Sum all the straight line length reservations to get the total straight line length reservation (Y3):

[0144]

[0145] Where n is the total number of straight cables in the total path.

[0146] S45: Add the length of the straight section, the corner bend reserve, the fixed point spacing and the sag to obtain the estimated length L of each cable or optical cable. sum .

[0147] L sum =Y1+Y2+Y3

[0148] The present invention is a method for estimating the length of a substation secondary cable. The method for accurately estimating the length of a substation secondary cable of the present invention shows significant beneficial effects in improving estimation accuracy, optimizing engineering efficiency, enhancing laying standardization and safety, improving resource utilization and economic benefits, and promoting standardization and intelligence in the power industry, and is of great significance to the sustainable development and technological progress of the power industry.

[0149] The basic principles and main features of the present invention and the advantages of the present invention are shown and described above. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention.

[0150] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for estimating the length of a secondary cable in a substation, characterized in that: The following steps are involved: S1. According to the actual spatial layout of the substation, the substation is divided into multiple areas with specific functions, such as high-voltage switchgear area, relay protection and control room area, AC / DC power system area, etc.; within each area, the relevant equipment is further divided into logically clear and functionally independent intervals according to the working principle and electrical connection requirements of the equipment, such as circuit breaker intervals, protection screen intervals, AC / DC power screen intervals, etc.; S2. Collect and enter basic information of the substation, including but not limited to total installed capacity, voltage level, main wiring system form, equipment model and configuration, secondary equipment interface standard and other key data, to provide accurate basic parameters for subsequent cable or optical cable length estimation; S3. According to the design drawings and project technical specifications, detailed statistics are made on the types, specifications and quantities of secondary cables or optical cables required to be connected in each compartment, including but not limited to control cables, signal cables, communication optical cables, etc.; Ensure that the statistics are comprehensive and match the actual device interface, providing a complete data set for subsequent length calculation; S4. Use the cable or optical cable length calculation model to estimate the length of each cable or optical cable to ensure that the result is close to the actual demand; S5. Summarize the estimated lengths of all cables or optical cables to generate a detailed cable or optical cable length list; The list not only includes the starting and ending points, specifications, and quantity of each cable or optical cable, but also includes the estimated length value.

2. A method for estimating the length of a substation secondary cable according to claim 1, characterized in that: The step S1 specifically includes the following steps: S1-1. Obtain a detailed substation layout diagram, including building structure, equipment location, channel layout, cable trench direction and other information, as the basis for space division; S1-2. Based on the overall functions and equipment distribution of the substation, identify areas with obvious physical boundaries and functional characteristics, such as high-voltage switchgear area, relay protection and control room area, AC and DC power supply system area, etc. These areas usually correspond to the main electrical function modules of the substation, and have relatively concentrated equipment layout on the floor plan; S1-3. On the substation layout plan, the boundaries of each area shall be clearly marked with lines, using physical partitions such as building walls, partitions, fences, etc., or according to the actual situation of centralized equipment layout; S1-4. For each identified site, further refine it into logically clear and functionally independent intervals according to the working principle and electrical connection requirements of the equipment, analyze the working relationship between the equipment, study the electrical connection, control logic, signal transmission path, etc. between the equipment in the site, and clarify the working coordination relationship between the equipment; S1-5. Divide and name the bays. In the field, according to the determined division principle, combine the equipment into logically independent and functionally related bays. To facilitate subsequent design and construction, give each bay a clear name, such as "No. 1 main transformer high-voltage side circuit breaker bay", "220kV busbar protection panel bay", "DC operating power supply panel bay", etc.; S1-6. Draw an interval layout diagram. Based on the site plan, describe in detail the specific location, arrangement and electrical connection relationship of the equipment in each interval to form an interval layout diagram.

3. A method for estimating the length of a substation secondary cable according to claim 1, characterized in that: The step S2 specifically includes the following steps: S2-1. Identify the required information categories: Total installed capacity: the total power generation or transmission capacity of the substation, usually in kilowatts (kW) or megawatts (MW); Voltage level: the rated voltage used by each part of the substation (such as high-voltage incoming lines, main transformers, feeders, etc.), such as 110kV, 220kV, 35kV, 10kV, etc.; Main wiring system form: the main circuit connection method on the high-voltage side and low-voltage side of the substation, such as single busbar segmentation, double busbar, bridge connection, angle connection, etc.; Equipment model and configuration: including the specific model, quantity, rated parameters and installation location of primary equipment such as transformers, circuit breakers, disconnectors, current / voltage transformers, lightning arresters, grounding switches, capacitors, reactors, etc.; Secondary equipment interface standards: communication protocols and interface standards (such as IEC 61850, ... 60870-5-103, etc.), signal type (analog, digital, GOOSE, SV, etc.) and terminal configuration; S2-2. On-site investigation and data collection: On-site investigation: Conduct detailed investigation at the substation site to verify the equipment installation location, actual operating status, sign information, etc., and record any discrepancies with the drawings; S2-3. Establish an information database and create a spreadsheet or database template suitable for storing basic information of the substation, including fields corresponding to the above-mentioned types of information; S2-4. Accurately enter the collected information into the corresponding fields to ensure the integrity and consistency of the data; perform preliminary verification of the entered data, such as checking whether the value range is reasonable, whether the logical relationship is correct, whether the equipment configuration is consistent with the main wiring diagram, etc., and correct any problems found in a timely manner; S2-5. Draw or update the cable route map based on the substation layout and equipment location, clarify the cable direction, laying method (overhead, direct burial, pipe, cable trench, etc.) and the location of intermediate joints and terminal joints; mark cable information: mark the starting and ending point equipment, cable model, cross-sectional area, length and other information of each cable on the cable route map to ensure that it is consistent with the equipment location information in the equipment configuration table; S2-6. Clarify the communication protocols, interface standards and versions used by each secondary device and record them in the database; draw interface diagrams: draw interface connection diagrams between secondary devices, indicating signal types, transmission directions, interface terminal numbers, etc., to ensure compliance with device interface configurations; S2-7. Count the interface cable requirements: Based on the interface connection diagram, estimate the type, quantity, and length of the required interface cables such as optical fiber, coaxial cable, and twisted pair, and provide data for optical or electrical cable length estimation.

4. A method for estimating the length of a substation secondary cable according to claim 3, characterized in that: The step S3 specifically comprises the following steps: S3-1. Be familiar with design drawings and technical specifications, and study design drawings: Carefully read the substation electrical primary and secondary system diagrams, panel cabinet layout diagrams, cable laying diagrams and other design drawings, and understand the location of each compartment (such as protection screen, measurement and control screen, metering screen, smart terminal screen, etc.), the internal equipment layout and the connection relationship between them; Interpret technical specifications: In-depth understanding of the project technical specifications on secondary equipment selection, interface standards, cable selection, laying requirements and other related clauses to ensure that the statistical work meets the requirements of the specifications; S3-2. Identify the secondary equipment interface and mark the interface type: mark the input and output interface types of each secondary equipment (such as relays, protection devices, measurement and control devices, intelligent terminals, switches, etc.) on the drawings; S3-3. According to the interface type and function, the required cables are divided into control cables, signal cables, communication optical cables, power cables and other categories; S3-4. Draw a detailed secondary cable connection diagram on the drawing, clearly marking the starting point, end point, interface number, cable type and specification of each cable; Count the number of cables: Count each type of cable one by one, including trunk cables, branch cables, jumpers, etc., to ensure that no necessary cables are missed; S3-5. Compare the statistical cable information with the actual interfaces of the equipment one by one to confirm that the cable type and specification fully match the interface requirements without omissions or errors. If inconsistencies or errors are found, adjust the cable type, specification or quantity in a timely manner, and update the cable connection diagram and statistical list; S3-6. Based on the statistical results, prepare a detailed secondary cable inventory, which should include cable number, type, specification, starting device and interface, terminal device and interface, length (to be calculated later), quantity and other information.

5. A method for estimating the length of a substation secondary cable according to claim 1, characterized in that: The step S4 specifically comprises the following steps: S4-1. Obtain design drawings containing detailed information such as the location of equipment in each compartment, the layout of the cabinets, and the wiring path, as the basic data for calculating the length of the cable or optical cable; determine the type and specification of the cable or optical cable: refer to the cable inventory to clarify the type, specification, starting and end devices, and interface information of each cable or optical cable; S4-2. Calculate the total length Y1 of the straight section.

6. A method for estimating the length of a substation secondary cable according to claim 5, characterized in that: In S4, the sites C1, C2…C n Represents the venues connected by straight lines, with intervals T1, T2…T m represents different intervals and S1, S2…S m Represents the number of intervals corresponding to different intervals. The distance between each venue is represented by a one-dimensional array [DC], then: [DC]=[LC 11 ,LC 12 ,…LC 1n ,LC 22 ,LC 23 ,…LC (n-1)(n-1) ,LC nn ] The total straight-line distance is: Where m is the number of intervals, n is the number of sites, LP ij (i≠j) represents the straight-line distance between the various sites; S4-3. Calculate the reserved Y2 for corner bending Determine the bending radius: refer to the cable or optical cable laying specifications to check the minimum allowable bending radius of cables or optical cables of different diameters and types at various corners (such as 90°, 45°, etc.); Single bend length calculation formula: For a specific corner (such as 90° or 45°), the actual length of the bend (L_bend) can be calculated by the following formula: in: θ is the turning angle, in degrees (°); R is the minimum allowable bending radius of the cable or optical cable at this angle, in meters (m); π is the circumference of a circle, which is approximately 3.14159; For each corner or turn on the total cable or total optical cable path, the bending length (L_bend_i) is calculated according to the above formula, where i represents the i-th turning point; Sum up all the individual bend lengths to get the total bend reserve length (Y2): Where n is the total number of turning points or turns on the total path.

7. A method for estimating the length of a secondary cable in a substation according to claim 6, characterized in that: S4-4. Consider the fixed point spacing and slack: Determine the spacing between suspension points: According to the cable or optical cable laying specifications and combined with site conditions, set a reasonable spacing between suspension points; Calculate sag: Calculate the sag degree (sag) of the cable or optical cable under its own weight using parameters such as the cable or optical cable weight, the spacing between suspension points, and gravitational acceleration. The sag degree (sag) of the cable or optical cable under its own weight can be calculated according to the following formula: Where: L s is the sag (droop length), in meters (m); W is the weight of the cable or optical cable per unit length, in Newton per meter (N / m); l is the suspension point spacing, in meters (m); l span is the actual hanging length of the cable or optical cable between two adjacent hanging points (taking into account the bending reserve, etc.), in meters (m); T is the tension of the cable or optical cable (usually a certain proportion of the maximum allowable tension, such as 50% to 70%), in Newtons (N); α is the angle between the cable or optical cable and the vertical direction, that is, the hanging angle, in radians (rad); Reserve length for thermal expansion and contraction: refer to the linear expansion coefficient of the cable or optical cable material, calculate the length change caused by thermal expansion and contraction according to the maximum temperature difference and the length of the straight section, and reserve the corresponding length; Electrical cables or optical cables will expand and contract under temperature changes. It is necessary to reserve a corresponding length based on the linear expansion coefficient of the material, the maximum temperature difference, and the length of the straight segment. The calculation formula is as follows: L t =α×ΔT×L s in: L t is the length reserved due to thermal expansion and contraction, in meters (m); α is the linear expansion coefficient of the cable or optical cable material, in units of percentage change in length per degree Celsius (℃); ΔT is the maximum temperature difference that the cable or optical cable may experience, in degrees Celsius (℃); L s It is the length of the straight cable or optical cable that needs to take into account the effect of thermal expansion and contraction, in meters (m); For each straight cable on the entire cable or optical cable path, the length of the straight segment is calculated according to the above formula and the corresponding length is reserved, where i represents the number of the i-th straight line; Sum all the straight line length reservations to get the total straight line length reservation (Y3): Where n is the total number of straight cables on the total path; S4-5. Add the length of the straight section, the corner bend reserve, the fixed point spacing and the sag to obtain the estimated length L of each cable or optical cable. sum ; <h2 style=";text-align:left;direction:ltr">L<h2 style=";text-align:left;direction:ltr"> sum <h2 style=";text-align:left;direction:ltr"> =Y1+Y2+Y3 8. A method for estimating the length of a substation secondary cable according to claim 1, characterized in that: The cable or optical cable length calculation model in S4 includes the following factors: straight section length, corner bend reservation, fixed point spacing and sag.

9. A method for estimating the length of a secondary cable in a substation according to claim 8, characterized in that: For the length of straight sections, the straight-line distance between each interval is accurately measured or calculated according to the equipment layout diagram; for corner bend reservation, the bending radius and reserved length of various corners and turns are calculated according to the cable or optical cable laying specifications; for the fixed point spacing and sag, the spacing between hanging points when laying cables or optical cables, the degree of sag caused by gravity, and the thermal expansion and contraction caused by temperature changes are considered.

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