A submarine cable selection method and device based on the longest power transmission distance, a terminal device, and a storage medium

Abstract

This invention discloses a method, apparatus, terminal equipment, and storage medium for selecting submarine cables based on the longest transmission distance, belonging to the field of power system transmission planning. The method includes: acquiring the submarine cable to be evaluated and acquiring the basic parameters of each type of submarine cable; acquiring the ideal active power utilization rate and the preset reactive power compensation degree; determining the current carrying capacity correction coefficient based on the fitting formula of conductor cross-sectional area and current carrying capacity correction coefficient; obtaining the low-frequency rated current carrying capacity based on the current carrying capacity correction coefficient; determining the low-frequency rated capacity based on the low-frequency rated current carrying capacity and the calibrated rated voltage; establishing and solving the submarine cable capacity-distance equation to obtain the limit transmission distance of the submarine cable; correcting the limit transmission distance according to the ideal active power utilization rate and the preset reactive power compensation degree; and determining the submarine cable type based on the theoretical longest transmission distance of each type. By implementing this invention, the problem of poor universality of existing submarine cable selection methods can be solved.

Description

Technical Field

[0001] This invention relates to the field of power system transmission planning, and in particular to a method, apparatus, terminal equipment and storage medium for selecting submarine cables based on the longest transmission distance. Background Technology

[0002] During the planning stage of offshore wind power transmission projects, it is necessary to complete the selection of submarine cable specifications. The cable selection results directly determine the project construction investment, the active power transmission capacity of the line, and the long-term operational safety margin.

[0003] Existing submarine cable selection methods, whether for conventional power frequency transmission scenarios or low-frequency AC transmission scenarios, directly substitute the calibration and rated parameters under conventional power frequency into a fixed power frequency calculation model to determine the maximum transmission distance of the submarine cable and thus select the submarine cable type. However, this selection method does not consider the significant differences in the allowable current carrying capacity and line capacitive reactive power loss between low-frequency and conventional operating conditions, and lacks a transmission distance assessment mechanism adapted to low-frequency scenarios. Therefore, existing submarine cable selection methods suffer from poor versatility. Summary of the Invention

[0004] This invention provides a method, apparatus, terminal equipment, and storage medium for selecting submarine cables based on the longest transmission distance, which can solve the problem of poor universality in existing submarine cable selection methods.

[0005] The method for selecting submarine cables based on the longest transmission distance provided by this invention includes: Acquire several types of submarine cables to be evaluated. For each type of submarine cable to be evaluated, obtain the conductor cross-sectional area, capacitance per unit length, rated voltage at the first power frequency, and rated current carrying capacity. Obtain the ideal active power utilization rate of the submarine cable to be evaluated; and obtain the preset reactive power compensation degree of the symmetrical reactors at both ends; Based on the conductor cross-sectional area and the preset current carrying capacity correction coefficient fitting formula, the current carrying capacity correction coefficient is determined; and based on the current carrying capacity correction coefficient, the calibrated rated current carrying capacity at the first power frequency is corrected to the rated current carrying capacity corresponding to the second power frequency, so as to obtain the low-frequency rated current carrying capacity of the submarine cable to be evaluated at the second power frequency; wherein, the second power frequency is less than the first power frequency. Based on the low-frequency rated current carrying capacity and the calibrated rated voltage, the total three-phase apparent capacity of the cable at the second power frequency is determined as the low-frequency rated capacity. Based on the low-frequency rated capacity, low-frequency rated current carrying capacity, second power frequency, unit length capacitance, preset first correction fitting coefficient and preset second correction fitting coefficient, a submarine cable capacity distance equation is established, and the submarine cable capacity distance equation is solved to obtain the limit transmission distance of the submarine cable. The maximum transmission distance of the submarine cable is theoretically corrected based on the ideal active power utilization rate and the preset reactive power compensation degree to obtain the theoretical maximum transmission distance when the ideal active power utilization rate is met. Based on the theoretical maximum transmission distance of each type of submarine cable to be evaluated, the type of submarine cable suitable for the engineering requirements is determined.

[0006] Furthermore, the method for constructing the fitting formula for the current carrying capacity correction coefficient includes: Multiple sets of submarine cable test samples with different conductor cross-sectional areas were collected under the same test conditions; each set of submarine cable test samples included a calibrated rated current carrying capacity sample at the first power frequency and a low-frequency rated current carrying capacity sample at the second power frequency, corresponding to the same conductor cross-sectional area. For each set of submarine cable test samples, calculate the ratio of the corresponding low-frequency rated current carrying capacity sample to the calibrated rated current carrying capacity sample to obtain the current carrying capacity correction coefficient sample corresponding to each set of submarine cable test samples. Using the current carrying capacity correction coefficient sample as the dependent variable and the conductor cross-sectional area corresponding to the current carrying capacity correction coefficient sample as the independent variable, a quadratic polynomial is obtained by fitting, which serves as the fitting formula for the current carrying capacity correction coefficient.

[0007] Furthermore, based on the low-frequency rated current carrying capacity and rated voltage, the total apparent capacity of the cable under the second power frequency is determined, including: Based on the fixed coefficient of the three-phase symmetrical AC system, the three-phase capacity is converted between the rated voltage and the low-frequency rated current carrying capacity to obtain the total three-phase apparent capacity of the cable at the second power frequency.

[0008] Furthermore, the formula for the submarine cable capacity-distance equation is as follows: in, This refers to the active power capacity that the submarine cable can transmit. For low-frequency rated capacity, For the second power frequency, Capacitance per unit length For the maximum transmission distance, To preset the first correction fitting coefficient, To preset the second correction fitting coefficient, It is the low-frequency rated current carrying capacity. It is the calibrated rated voltage.

[0009] Furthermore, based on the ideal active power utilization rate and the preset reactive power compensation degree, the maximum transmission distance is corrected to obtain the theoretical maximum transmission distance of the submarine cable when the ideal active power utilization rate is met, including: The theoretical maximum transmission distance of submarine cables while meeting ideal active power utilization rate can be calculated using the following formula: in, This is the theoretical maximum transmission distance of a submarine cable while meeting ideal active power utilization. To preset the reactive power compensation degree, It is the ideal active power utilization rate. It is the maximum transmission distance.

[0010] Another embodiment of the present invention provides a submarine cable selection device based on the longest transmission distance, comprising: a first data acquisition module, a second data acquisition module, a low-frequency rated current carrying capacity determination module, a low-frequency rated capacity determination module, a limit transmission distance determination module, a theoretical longest transmission distance determination module, and a submarine cable type determination module; The first data acquisition module is used to acquire several types of submarine cables to be evaluated. For each type of submarine cable to be evaluated, it acquires the conductor cross-sectional area, capacitance per unit length, rated voltage and rated current carrying capacity at the first power frequency. The second data acquisition module is used to obtain the ideal active power utilization rate of the submarine cable to be evaluated; and to obtain the preset reactive power compensation degree of the symmetrical reactors at both ends; The low-frequency rated current carrying capacity determination module is used to determine the current carrying capacity correction coefficient based on the conductor cross-sectional area and a preset current carrying capacity correction coefficient fitting formula; and based on the current carrying capacity correction coefficient, correct the calibrated rated current carrying capacity at the first power frequency to the rated current carrying capacity corresponding to the second power frequency, so as to obtain the low-frequency rated current carrying capacity of the submarine cable to be evaluated at the second power frequency; wherein, the second power frequency is less than the first power frequency; The low-frequency rated capacity determination module is used to determine the total apparent capacity of the cable under the second power frequency based on the low-frequency rated current carrying capacity and the calibrated rated voltage, and use it as the low-frequency rated capacity. The limit transmission distance determination module is used to establish the submarine cable capacity distance equation based on the low-frequency rated capacity, low-frequency rated current carrying capacity, second power frequency, unit length capacitance, preset first correction fitting coefficient and preset second correction fitting coefficient, and solve the submarine cable capacity distance equation to obtain the limit transmission distance of the submarine cable. The theoretical maximum transmission distance determination module is used to correct the limit transmission distance based on the ideal active power utilization rate and the preset reactive power compensation degree, so as to obtain the theoretical maximum transmission distance of the submarine cable when the ideal active power utilization rate is met. The submarine cable type determination module is used to determine the submarine cable type that best suits the engineering requirements based on the theoretical maximum transmission distance of each type of submarine cable to be evaluated.

[0011] Furthermore, the low-frequency rated capacity determination module includes: a low-frequency rated capacity determination subunit; The low-frequency rated capacity determination subunit is used to perform three-phase capacity conversion between the rated voltage and the low-frequency rated current carrying capacity based on the fixed coefficient of the three-phase symmetrical AC system, so as to obtain the total three-phase rated apparent capacity of the cable at the second power frequency.

[0012] Furthermore, the module for determining the theoretical maximum transmission distance includes: a subunit for determining the theoretical maximum transmission distance; The theoretical maximum transmission distance determination subunit is used to calculate the theoretical maximum transmission distance of the submarine cable while satisfying the ideal active power utilization rate, based on the following formula: in, This is the theoretical maximum transmission distance of a submarine cable while meeting ideal active power utilization. To preset the reactive power compensation degree, It is the ideal active power utilization rate. It is the maximum transmission distance.

[0013] Another embodiment of the present invention provides a terminal device, including: a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the steps of the submarine cable selection method based on the longest transmission distance provided by the present invention.

[0014] Another embodiment of the present invention also provides a computer-readable storage medium item, including: a stored computer program, which, when the computer program is running, controls the device where the computer-readable storage medium is located to perform the steps of the submarine cable selection method based on the longest transmission distance provided by the present invention.

[0015] The following benefits can be obtained by implementing the present invention: This invention provides a method, apparatus, terminal equipment, and storage medium for selecting submarine cables based on the longest transmission distance. The method includes: acquiring several types of submarine cables to be evaluated; for each type of submarine cable to be evaluated, acquiring the conductor cross-sectional area, capacitance per unit length, rated voltage at a first power frequency, and rated current carrying capacity; acquiring the ideal active power utilization rate of the submarine cable to be evaluated; and acquiring the preset reactive power compensation degree of the symmetrical reactors at both ends; determining the current carrying capacity correction coefficient based on a fitting formula using the conductor cross-sectional area and a preset current carrying capacity correction coefficient; and based on the current carrying capacity correction coefficient, correcting the rated current carrying capacity at the first power frequency to the rated current carrying capacity corresponding to the second power frequency, thereby obtaining the low-frequency rated current carrying capacity of the submarine cable to be evaluated at the second power frequency. Current carrying capacity; wherein the second power frequency is less than the first power frequency; based on the low-frequency rated current carrying capacity and the rated voltage, the total apparent capacity of the three phases of the cable at the second power frequency is determined as the low-frequency rated capacity; based on the low-frequency rated capacity, low-frequency rated current carrying capacity, second power frequency, capacitance per unit length, preset first correction fitting coefficient and preset second correction fitting coefficient, a submarine cable capacity distance equation is established, and the submarine cable capacity distance equation is solved to obtain the limit transmission distance of the submarine cable; the limit transmission distance is corrected according to the ideal active power utilization rate and the preset reactive power compensation degree to obtain the theoretical maximum transmission distance of the submarine cable when the ideal active power utilization rate is met; based on the theoretical maximum transmission distance of each type of submarine cable to be evaluated, the submarine cable type suitable for the project requirements is determined.

[0016] Compared with existing technologies, this invention no longer determines the transmission distance of submarine cables based on the rated parameters of the submarine cable at the conventional power frequency, regardless of whether the operating conditions are normal or low-frequency. Instead, it determines the current carrying capacity correction coefficient based on the conductor cross-sectional area and a preset current carrying capacity correction coefficient fitting formula. Then, based on the current carrying capacity correction coefficient, the corrected low-frequency rated current carrying capacity at the second power frequency is obtained. Next, based on the low-frequency rated current carrying capacity and the rated voltage, the low-frequency rated capacity at the second power frequency is determined. Then, based on the low-frequency rated capacity, low-frequency rated current carrying capacity, the second power frequency, the capacitance per unit length, the preset first correction fitting coefficient, and the preset second correction fitting coefficient, a submarine cable capacity-distance equation is established and solved to obtain the ultimate transmission distance of the submarine cable. Finally, the influence of the symmetrical reactors at both ends and the active power utilization rate on the transmission distance is considered. The reactive power compensation degree and ideal active power utilization rate are used to correct the limit transmission distance, so as to obtain the theoretical maximum transmission distance of the submarine cable when the ideal active power utilization rate is met. Then, the cable type is selected based on the theoretical maximum transmission distance. Since this invention corrects the rated current carrying capacity to the low-frequency rated current carrying capacity under the second power frequency by fitting the formula based on the conductor cross-sectional area and the preset current carrying capacity correction coefficient, it reduces the deviation of the basic electrical parameters of the submarine cable under different frequency conditions. At the same time, the preset reactive power compensation degree of the symmetrical reactors at both ends is used to correct the transmission distance, taking into account the influence of the reactor on the transmission distance. The final transmission distance calculation result is consistent with the actual operating conditions of low-frequency long-distance submarine cables under both low-frequency and conventional conditions, which solves the problem of poor universality of the existing submarine cable transmission distance evaluation method. Attached Figure Description

[0017] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating a method for selecting submarine cables based on the longest transmission distance, provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of a submarine cable selection device based on the longest transmission distance provided in an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0021] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0024] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0025] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0026] See Figure 1 To address the problem of poor universality in existing submarine cable selection methods, an embodiment of the present invention provides a submarine cable selection method based on the longest transmission distance, comprising: S101: Obtain several types of submarine cables to be evaluated. For each type of submarine cable to be evaluated, obtain the conductor cross-sectional area, capacitance per unit length, rated voltage at the first power frequency, and rated current carrying capacity of the submarine cable to be evaluated. Specifically, this step is the data input stage for the entire submarine cable selection method. First, multiple specifications of submarine cables to be evaluated are retrieved in batches. For each candidate submarine cable, the conductor cross-sectional area, capacitance per unit length, rated voltage at the first power frequency, and rated current carrying capacity are collected. The conductor cross-sectional area is the cross-sectional area of ​​the conductive core of the submarine cable; this parameter directly determines the cable's heat dissipation capacity and current carrying capacity limit, and is the core input variable for subsequent fitting calculations of the low-frequency current carrying capacity correction coefficient. The capacitance per unit length is the distributed capacitance of the submarine cable to the ground per unit length; the capacitive reactive power loss of long-distance transoceanic submarine cables is mainly caused by this capacitance. The parameters determine the basic data for establishing the submarine cable capacity-distance equation and calculating the reactive power loss of the line. The rated voltage at the first power frequency is the rated line voltage calibrated based on the first power frequency when the cable leaves the factory. It is the reference parameter for the cable insulation withstand capability. The rated voltage of the cable insulation remains unchanged under low-frequency transmission conditions. The rated voltage is used for power calculation throughout the process. Preferably, the first power frequency is the conventional power frequency of 50Hz. The rated current carrying capacity at the first power frequency is the maximum rated current that the cable can carry for a long time under conventional power frequency conditions. It is the manufacturer's standard factory parameter. This value cannot be directly applied to low-frequency transmission scenarios and needs to be corrected for power frequency differences later.

[0027] S102: Obtain the ideal active power utilization rate of the submarine cable to be evaluated; and obtain the preset reactive power compensation degree of the symmetrical reactors at both ends; Specifically, this step is used to obtain the operating constraint parameters and reactive power device preset parameters of the submarine low-frequency power transmission system. It is a key preliminary step for subsequent correction of the limit transmission distance and to conform to the actual engineering operating conditions.

[0028] Among them, the ideal active power utilization rate is a fixed operating parameter pre-set during the engineering planning stage. It refers to the ideal ratio of the actual active power transmitted by the submarine cable to the cable's rated apparent capacity. It is the core operating condition indicator used in this method to constrain the active power transmission capacity of the cable. Affected by line reactive power loss and power frequency variation, the cable cannot always operate at full apparent power. This parameter is used to limit the active power output range of the cable, conforming to the power transmission requirements of actual power transmission projects and avoiding cable overload operation. At the same time, this parameter will be used in subsequent steps to correct the ultimate transmission distance, ultimately obtaining the theoretical maximum transmission distance that meets the actual active power transmission requirements, ensuring the steady-state operation stability of the power transmission system. Regarding the preset reactive power compensation degree of the symmetrical reactors at both ends, to address the issue of excess capacitive reactive power in long-distance submarine cables, symmetrical reactors will be installed at both ends of the transmission line in the project for reactive power compensation. The preset reactive power compensation degree is a pre-set reactive power compensation matching ratio. This parameter is used to characterize the reactor's ability to offset the capacitive reactive power of the submarine cable line, which can eliminate the constraint of long-distance capacitive reactive power on the transmission distance. Subsequently, this parameter will be used to correct the initial limit transmission distance and restore the true maximum transmission capacity after the reactive power compensation device is put into operation.

[0029] The two types of parameters obtained in this step correspond to the system's active power operation constraints and the line's reactive power compensation constraints, respectively. This overcomes the limitations of relying solely on the electrical parameters of the cable itself to calculate the transmission distance, making the subsequent transmission distance calculation results more consistent with the actual engineering operation conditions after the addition of reactive power compensation equipment.

[0030] S103: Based on the conductor cross-sectional area and the preset current carrying capacity correction coefficient fitting formula, determine the current carrying capacity correction coefficient; and based on the current carrying capacity correction coefficient, correct the calibrated rated current carrying capacity at the first power frequency to the rated current carrying capacity corresponding to the second power frequency, to obtain the low-frequency rated current carrying capacity of the submarine cable to be evaluated at the second power frequency; wherein, the second power frequency is less than the first power frequency. The methods for constructing the fitting formula for the current carrying capacity correction coefficient include: Multiple sets of submarine cable test samples with different conductor cross-sectional areas were collected under the same test conditions; each set of submarine cable test samples included a calibrated rated current carrying capacity sample at the first power frequency and a low-frequency rated current carrying capacity sample at the second power frequency, corresponding to the same conductor cross-sectional area. For each set of submarine cable test samples, calculate the ratio of the corresponding low-frequency rated current carrying capacity sample to the calibrated rated current carrying capacity sample to obtain the current carrying capacity correction coefficient sample corresponding to each set of submarine cable test samples. Using the current carrying capacity correction coefficient sample as the dependent variable and the conductor cross-sectional area corresponding to the current carrying capacity correction coefficient sample as the independent variable, a quadratic polynomial is obtained by fitting, which serves as the fitting formula for the current carrying capacity correction coefficient.

[0031] For example, through a limited number of simulations, test samples of submarine cables with different conductor cross-sectional areas can be obtained, as shown in the table below: Table 1. Example of submarine cable test samples with different conductor cross-sectional areas. It should be noted that this table contains simulation data of the rated current carrying capacity at the first power frequency and the low-frequency rated current carrying capacity at the second power frequency for submarine cables with different conductor cross-sections under the same laying conditions. The calculation basis conditions are uniformly set as follows: seabed burial depth of 2.5m, ambient temperature of 25℃, and soil thermal resistivity of 0.7K. m / W eliminates the interference of laying and environmental variables on current carrying capacity, and only retains two types of variables, conductor cross-section and operating frequency, for comparative analysis.

[0032] Based on the sample data in the table, the following patterns can be observed: For submarine cables with the same conductor cross-section, the low-frequency rated current carrying capacity allowed for long-term operation under the second power frequency low-frequency condition is always higher than the rated current carrying capacity under the first power frequency conventional condition; as the cross-sectional area of ​​the cable conductor gradually increases, the current carrying capacity correction coefficient generally shows an upward trend, indicating that there is a strong correlation between the conductor cross-sectional size and the difference between high and low frequency current carrying capacity, and there is no uniform fixed correction coefficient applicable to all cross-sectional specifications; the existing technology directly uses the rated current carrying capacity of the first power frequency to substitute into the model to calculate the low-frequency transmission distance without distinguishing the differentiated correction coefficients corresponding to different cross-sections, resulting in an underestimation of the low-frequency current carrying capacity value, and the final calculated ultimate transmission distance will deviate significantly from the actual transmission capacity of the cable.

[0033] For example, the second power frequency is 20 Hz.

[0034] For example, using the current carrying capacity correction coefficient sample as the dependent variable and the conductor cross-sectional area corresponding to the current carrying capacity correction coefficient sample as the independent variable, a quadratic polynomial is fitted to obtain the current carrying capacity correction coefficient fitting formula, which can be expressed as: (1) in, This represents the current carrying capacity correction factor. This represents the cross-sectional area of ​​the conductor.

[0035] For example, the current carrying capacity correction coefficient is determined based on the conductor cross-sectional area and a preset current carrying capacity correction coefficient fitting formula, including: determining the current carrying capacity correction coefficient according to the current carrying capacity correction coefficient fitting formula as shown in formula (1).

[0036] For example, "based on the current carrying capacity correction factor, the calibrated rated current carrying capacity at the first power frequency is corrected to the rated current carrying capacity corresponding to the second power frequency to obtain the low-frequency rated current carrying capacity of the submarine cable to be evaluated at the second power frequency" includes: calculating the low-frequency rated current carrying capacity of the submarine cable to be evaluated at the second power frequency according to the following formula: (2) in, This indicates the low-frequency rated current carrying capacity at the second power frequency. This represents the current carrying capacity correction factor. This indicates the rated current carrying capacity at the first power frequency.

[0037] S104: Based on the low-frequency rated current carrying capacity and the calibrated rated voltage, determine the total apparent capacity of the three phases of the cable at the second power frequency, which is taken as the low-frequency rated capacity.

[0038] Furthermore, based on the low-frequency rated current carrying capacity and rated voltage, the total apparent capacity of the cable under the second power frequency is determined, including: Based on the fixed coefficient of the three-phase symmetrical AC system, the three-phase capacity is converted between the rated voltage and the low-frequency rated current carrying capacity to obtain the total three-phase apparent capacity of the cable at the second power frequency.

[0039] For example, the total apparent capacity of the cable at the second power frequency is calculated according to the following formula: (3) in, This indicates the apparent capacity of the cable's three-phase total capacity at the second power frequency. Indicates the rated voltage. Indicates the rated current carrying capacity at low frequencies. This represents the fixed coefficient of a three-phase symmetrical AC system.

[0040] This step relies on the corrected low-frequency rated current carrying capacity and the cable's factory-calibrated rated voltage to solve for the total apparent capacity of the three phases of the submarine cable under the second power frequency condition. This yields the low-frequency rated capacity used for subsequent transmission distance calculations, providing core capacity parameters for establishing the submarine cable capacity-distance equation.

[0041] It should be noted that this step uses the cable's factory-rated voltage throughout, only replacing it with the corrected low-frequency rated current carrying capacity for capacity calculation. Unlike existing technologies that directly use power frequency current carrying capacity to calculate apparent capacity, this invention first completes low-frequency correction of current carrying capacity through a cross-section matching correction coefficient, and then substitutes it into the three-phase capacity formula for calculation. The resulting low-frequency rated capacity can truly reflect the maximum apparent power that the cable can safely transmit for a long time at the second power frequency, avoiding the problem of underestimating the rated capacity due to ignoring the difference between high and low frequency current carrying capacity, which would lead to conservative calculation results for the ultimate transmission distance and excessive redundancy in cable selection specifications.

[0042] S105: Based on the low-frequency rated capacity, low-frequency rated current carrying capacity, second power frequency, unit length capacitance, preset first correction fitting coefficient and preset second correction fitting coefficient, establish the submarine cable capacity distance equation, solve the submarine cable capacity distance equation, and obtain the limit transmission distance of the submarine cable. Furthermore, the formula for the submarine cable capacity-distance equation is as follows: (4) in, This refers to the active power capacity that the submarine cable can transmit. For low-frequency rated capacity, For the second power frequency, Capacitance per unit length For the maximum transmission distance, To preset the first correction fitting coefficient, To preset the second correction fitting coefficient, It is the low-frequency rated current carrying capacity. It is the calibrated rated voltage.

[0043] It should be noted that formula (4) With the previous formula All of these represent the low-frequency rated current carrying capacity of the submarine cable under the second power frequency low-frequency condition. For the sake of simplicity, the symbols used hereafter will be consistent. Refers to this parameter.

[0044] In one possible implementation, the submarine cable capacity-distance equation is solved to obtain the limiting transmission distance of the submarine cable. The limiting transmission distance of the submarine cable obtained by the solution can be expressed as: (5) in, (6) in, This represents the maximum transmission distance for submarine cables. For low-frequency rated current carrying capacity, A customized comprehensive proportional coefficient for low-frequency submarine cable charging current. For the second power frequency, Capacitance per unit length It is the calibrated rated voltage.

[0045] The following explains the principle behind establishing the submarine cable capacity-distance equation: The transmission capacity of the transmission line is the primary consideration in designing offshore wind power grid connection schemes. The transmission capacity of the transmission line is generally constrained by two types of factors: stability limit and thermal limit. The stability limit refers to the upper limit of power transmission that the AC transmission system can allow to ensure stable operation under small disturbances. The thermal limit requires that the thermal effect generated by the line current cannot exceed the rated limit of the cable, that is, the effective value of the current at any point on the line must not exceed the rated current carrying capacity of the cable.

[0046] Submarine cables are mostly used in cross-sea power transmission scenarios. The inductance of submarine cables is much smaller than that of overhead lines, and the stability limit is higher. However, submarine cables are laid in a closed environment with poor heat dissipation conditions. The heat generated by the current is easy to accumulate and rise inside the line. Therefore, the thermal limit is the core constraint that limits the transmission capacity of submarine cables.

[0047] The total line current of the submarine cable during operation can be decomposed into two components with a 90° phase difference and independent thermal effects: one is the active current component used to transmit the active power of the wind farm. Its magnitude is determined by the wind farm's output and the line voltage level; secondly, it is the reactive charging current component caused by the line's distributed capacitance. It is directly related to the line voltage level and distributed capacitance parameters, and is also the dominant current component under no-load conditions of the cable. The complex form of the line current is: (7) in, A complex number representing the line current; Represents the active current component; Indicates the imaginary unit; This represents the charging current component.

[0048] When a cable transmits active power, both the active current and the charging current occupy the cable's rated current-carrying capacity. The total rated capacity of the line can be divided into two parts: the charging capacity occupied by the charging current and the available capacity that can be used to transmit active power. These two parts satisfy a capacity balance relationship: Rated capacity = Charging capacity + Available capacity. Based on the capacity distribution law of the current thermal effect, a general formula for calculating charging capacity can be derived: (8) in, For charging capacity, For charging current, The rated current carrying capacity of the cable is used here. Since the calculation is for charging capacity under low-frequency conditions, the low-frequency rated current carrying capacity is taken here. This is the rated capacity for low frequency.

[0049] Based on this, a general expression for available capacity is further obtained: (9) in, This refers to the active power capacity that the line can transmit externally. For low-frequency rated capacity, For charging capacity, For charging current, This is the cable's rated current carrying capacity. Since we are calculating the capacity under low-frequency operating conditions, we will use the low-frequency rated current carrying capacity here.

[0050] Formulas (8) and (9) above are general derivations of capacity relationships under normal load conditions. Charging current It is not a fixed constant; its value varies with the cable transmission length. In actual engineering planning, it is usually required that the wind farm turbines operate under a unity power factor condition, with the wind farm only outputting active power and not sending out excess reactive power. At this time, all reactive current in the line comes from the charging current generated by the distributed capacitance of the submarine cable under the excitation of the second power frequency (low frequency) AC voltage. Therefore, the complete expression for the charging current is: (10) in, For charging current, For the second power frequency, Capacitance per unit length Indicates the cable transmission length. This is a correction term for the long-line effect capacitance of long-distance submarine cables. It is the calibrated rated voltage. This is constructed by pre-setting the first correction fitting coefficient and the second correction fitting coefficient. (11) in, This is a correction term for the long-line effect capacitance of long-distance submarine cables. To preset the first correction fitting coefficient, To preset the second correction fitting coefficient, Indicates the length of the cable used for power transmission.

[0051] The charging current varies with length With the long-line effect capacitance correction term of long-distance submarine cables By substituting the above general available capacity basic formula (9), we can obtain the equation of this invention specifically adapted to low-frequency submarine cable conditions, reflecting the relationship between available capacity and transmission length: (12) in, This refers to the active power capacity that the submarine cable can transmit. For low-frequency rated capacity, For the second power frequency, Capacitance per unit length For the maximum transmission distance, To preset the first correction fitting coefficient, To preset the second correction fitting coefficient, It is the low-frequency rated current carrying capacity. It is the calibrated rated voltage.

[0052] This equation can intuitively reflect the available active power capacity. With transmission length The secondary attenuation law is as follows: the longer the cable transmission length, the larger the total distributed capacitance of the line, the higher the amplitude of the charging current, the more the rated capacity is squeezed out by the charging capacity, and the smaller the active capacity that the line can transmit.

[0053] To determine the maximum transmission distance at which a cable can stably deliver active power, this invention introduces a critical constraint condition corresponding to the line under no-load conditions: when the line reaches its maximum transmission length, the charging current will completely fill the cable's rated current-carrying capacity, and the line will no longer have the ability to transmit any active power. The corresponding available active capacity in the equation is... This critical operating state is equivalent to the line's no-load condition.

[0054] Critical constraints By substituting the values ​​into the established equations, the cable length required to reduce the available capacity to zero can be determined. This length represents the ultimate transmission distance of the submarine cable. .

[0055] S106: Based on the ideal active power utilization rate and the preset reactive power compensation degree, the maximum transmission distance of the submarine cable is corrected to obtain the theoretical maximum transmission distance when the ideal active power utilization rate is met. Based on the ideal active power utilization rate and the preset reactive power compensation degree, the maximum transmission distance of the submarine cable is corrected to obtain the theoretical maximum transmission distance when the ideal active power utilization rate is met, including: The theoretical maximum transmission distance of submarine cables while meeting ideal active power utilization rate can be calculated using the following formula: (13) in, This is the theoretical maximum transmission distance of a submarine cable while meeting ideal active power utilization. To preset the reactive power compensation degree, It is the ideal active power utilization rate. It is the maximum transmission distance.

[0056] The principle of formula (13) will be explained in detail below: The aforementioned method enables available capacity The limit transmission distance obtained by solving This is the theoretical extreme value under ideal boundaries. This value only represents the critical length at which the cable cannot transmit active power at all, without taking into account the actual active power output constraints of the project. Actual offshore wind power projects will not fully overdraw the cable capacity to the limit state of no active power output. In the project planning stage, the ideal active power utilization rate will be preset as the system operation constraint index to ensure that the wind power output has a stable adjustment margin. Therefore, it is necessary to introduce the line utilization rate to correct the limit transmission distance and find the theoretical farthest transmission distance that meets the preset active power transmission level.

[0057] In practical engineering construction, besides the absolute value of available capacity, line utilization rate (i.e., the ideal active power utilization rate of this invention) is a more important indicator. Line utilization rate is defined as the ratio of available capacity to low-frequency rated capacity: (14) in, It is the line utilization rate (i.e., the ideal active power utilization rate of this invention). This refers to the active power capacity that the submarine cable can transmit. This is the rated capacity for low frequency. The higher the value, the greater the proportion of available capacity to total rated capacity, the smaller the proportion of capacity squeezed out by charging capacity, and the more fully the rated transmission capacity of the cable is utilized. After incorporating line utilization into the capacity-distance equation and substituting variables, for a given ideal active power utilization rate... Based on formula (5), the corresponding maximum power transmission distance after modification can be expressed as: (15) in, To match the preset ideal active power utilization rate At that time, the theoretical maximum transmission distance of the submarine cable is after the active power utilization rate is corrected (without compensation correction). To preset the ideal active power utilization rate, It is the maximum transmission distance.

[0058] It should be noted that the transmission distance obtained by introducing only the ideal active power utilization rate for the initial correction is only suitable for bare cable conditions without any reactive power compensation devices. In actual cross-sea low-frequency power transmission projects, the distributed capacitance of long submarine cables will generate a large amount of capacitive reactive power charging current, which will significantly reduce the rated current carrying capacity of the cable and compress the active power transmission distance. In engineering projects, symmetrical reactors are generally installed at both ends of the line to absorb capacitive reactive power. Therefore, the theoretical maximum transmission distance of the submarine cable after the ideal active power utilization rate correction still needs to be corrected a second time by the preset reactive power compensation degree of the symmetrical reactors at both ends, so as to restore the actual transmission limit capacity after the addition of reactive power compensation devices.

[0059] The aforementioned basic derivation of the capacity-distance equation only considers the submarine cable itself and assumes that the wind farm operates under ideal conditions with unity power factor and no additional reactive power compensation, without taking into account the inductive reactive power cancellation effect of the reactors at both ends. To reduce the capacitive reactive current inside the AC submarine cable and effectively increase the active power that the cable can transmit and the maximum transmission distance, the industry's conventional solution is to connect symmetrical reactors in parallel at both ends of the submarine cable. The inductive reactive power output by the reactors can cancel the capacitive reactive power generated by the cable's distributed capacitance, directly changing the distribution pattern of reactive current and charging capacity along the entire submarine cable.

[0060] Reactive power compensation for submarine cables is divided into two categories: inductive parallel reactors and power electronic compensation. This invention employs inductive reactors symmetrically arranged at both ends for reactive power regulation. Without installing any reactive power compensation equipment, reactive power can be adjusted at any location along the submarine cable. At this point, only the capacitive charging current generated by the cable's distributed capacitance exists, with no canceling component. Therefore, the effective value expression for the reactive current along the line is: (16) in, This represents the effective value of the reactive current along the line. For the second power frequency, Capacitance per unit length It is the calibrated rated voltage. This represents the length along the cable from the cable's beginning. As the formula shows, under uncompensated conditions, the charging current increases linearly with the cable's length, reaching its maximum at the end of the line and consuming a significant portion of the cable's rated capacity.

[0061] To quantify the reactive power compensation effect of the reactor, the reactive power compensation degree is defined as the ratio of the reactor's output inductive reactive power to the total capacitive charging reactive power of the entire submarine cable, and its expression is: (17) in, It is the reactive power compensation degree. It is inductive reactive power. It is the total capacitive charging reactive power of the entire submarine cable. For the second power frequency, Capacitance per unit length Indicates the cable transmission length. It is the calibrated rated voltage.

[0062] The inductive reactive power output by the reactor is out of phase with the capacitive reactive power generated by the cable capacitance, and the two can cancel each other out. Under the condition of symmetrical compensation at both ends of the line, at any point along the submarine cable... The reactive current expression at point is corrected to: (18) in, For any location along the submarine cable reactive current at the location, For the second power frequency, Capacitance per unit length It is the calibrated rated voltage. For reactive power compensation, It refers to any location along the submarine cable route.

[0063] If we do not distinguish between the phase directions of capacitive and inductive currents, and only focus on the effective value of reactive current heating, then we take the absolute value of the expression: (19) in, For any location along the submarine cable reactive current at the location, For the second power frequency, Capacitance per unit length It is the calibrated rated voltage. For reactive power compensation, It refers to any location along the submarine cable route.

[0064] The thermal limit is determined by the location of the maximum effective value of reactive current on the line; only the two endpoints of the line need to be calculated. (First end) The absolute value of the reactive current at the (end) terminal: Head Location: (20) in, This represents the absolute value of the reactive current at the beginning of the circuit. For the second power frequency, Capacitance per unit length It is the calibrated rated voltage. For cable transmission length, This refers to reactive power compensation.

[0065] end Location: (twenty one) in, This represents the absolute value of the reactive current at the end. For the second power frequency, Capacitance per unit length It is the calibrated rated voltage. For cable transmission length, This refers to reactive power compensation.

[0066] Comparing the currents at the two locations, since ( Therefore, the end of the line This is the point where the reactive current reaches its maximum value. The maximum reactive current is: (twenty two) in, The maximum reactive current, For the second power frequency, Capacitance per unit length It is the calibrated rated voltage. For cable transmission length, This refers to reactive power compensation.

[0067] When there is no compensation Substituting into equation (22) above, we obtain the maximum charging current of the entire line without compensation: (twenty three) in, This represents the maximum charging current across the entire line without compensation. For the second power frequency, Capacitance per unit length It is the calibrated rated voltage. This refers to the cable transmission length.

[0068] Therefore, the equivalent charging capacity after compensation is: (twenty four) in, To compensate for the equivalent charging capacity, It is the calibrated rated voltage. For compensation degree The maximum reactive current at that time.

[0069] Uncompensated charging capacity is: (25) in, This is the capacity for uncompensated charging. It is the calibrated rated voltage. This is the maximum charging current for the entire line without compensation.

[0070] Comparing formulas (24) and (25), eliminating common terms and simplifying, we get: (26) in, To compensate for the equivalent charging capacity, It is the calibrated rated voltage. For the second power frequency, Capacitance per unit length It is the calibrated rated voltage. For cable transmission length, For reactive power compensation, This refers to the uncompensated charging capacity.

[0071] Based on the transformation of formula (26), the equivalent charging capacity formula with compensation is obtained: (27) in, To compensate for the equivalent charging capacity, This is the capacity for uncompensated charging. This refers to reactive power compensation.

[0072] In formula (9) Replace with After compensation, the available capacity is: (28) in, The compensated active power capacity that the line can transmit externally. For low-frequency rated capacity, This is the equivalent charging capacity after compensation.

[0073] Both sides of equation (28) are divided by the low-frequency rated capacity. Construct utilization form: (29) in, The compensated active power capacity that the line can transmit externally. For low-frequency rated capacity, This is the equivalent charging capacity after compensation.

[0074] Substitute the line utilization rate included in reactive power compensation ,get: (30) in, To account for line utilization in reactive power compensation, To compensate for the equivalent charging capacity, This is the rated capacity for low frequency.

[0075] Combining formulas (8) and (23), the charging capacity without compensation can be obtained: (31) in, This refers to the charging capacity without compensation. To achieve the theoretical maximum transmission distance that simultaneously considers active power utilization and reactive power compensation, A customized comprehensive proportional coefficient for low-frequency submarine cable charging current. For low-frequency rated capacity, It is the rated current carrying capacity for low frequency.

[0076] Combining formulas (27), (30), and (31), we first establish the conversion relationship between the compensated equivalent charging capacity and the uncompensated charging capacity using formula (27). Then, we substitute the uncompensated charging capacity shown in formula (31) into the line utilization rate relationship (30) including reactive power compensation. After variable substitution and simplification, we obtain the corrected expression for the line utilization rate including reactive power compensation: (32) in, To account for line utilization in reactive power compensation, This refers to the active power capacity that the line can stably transmit after reactive power compensation. For low-frequency rated capacity, A customized comprehensive proportional coefficient for low-frequency submarine cable charging current. To achieve the theoretical maximum transmission distance that simultaneously considers active power utilization and reactive power compensation, For reactive power compensation, It is the rated current carrying capacity for low frequency.

[0077] By solving the formula with variables, we finally obtained the modified theoretical maximum transmission distance formula (13), which takes into account both the ideal active power utilization rate and the reactive power compensation degree of the symmetrical reactors at both ends.

[0078] S107: Based on the theoretical maximum transmission distance of each type of submarine cable to be evaluated, determine the type of submarine cable that best suits the engineering requirements.

[0079] Specifically, after the entire calculation process from S101 to S106, the theoretical maximum transmission distance that each type of submarine cable to be evaluated can stably transmit power under the conditions of preset ideal active power utilization rate and preset reactive power compensation degree of symmetrical reactors at both ends has been calculated. This step uses the theoretical maximum transmission distance corresponding to each type of cable as the core evaluation criterion, combined with the actual transmission length requirements of offshore wind power projects, to complete the screening of submarine cable specifications. This is specifically divided into two steps: the first step is the screening based on hard distance conditions. The actual transmission length required for the project plan is extracted, and the theoretical maximum transmission distance of each type of cable is compared one by one, retaining only the cable specifications whose theoretical transmission length can cover the actual needs of the project. If the theoretical maximum transmission distance of a certain cable does not meet the laying length required by the project, operational risks such as excessive cable overheating, limited active power output, and line overload may occur after its commissioning, failing to meet the requirements for stable system operation. Therefore, this type of cable should be directly excluded. The second step is economical selection. Within the range of candidate cables that meet the distance requirements, a comprehensive comparison is made of different cables' conductor cross-sections, procurement costs, offshore laying construction costs, and long-term low-frequency transmission losses. Provided there is sufficient transmission margin, cables with smaller cross-sections and lower overall construction costs are prioritized. If the costs of multiple cables are similar, the model with lower line operating losses and better overall life-cycle benefits is prioritized.

[0080] This step relies on the precise transmission limits obtained through multiple corrections, including low-frequency current carrying capacity correction, long-line distributed capacitance correction, ideal active power utilization constraints, and preset reactive power compensation of symmetrical reactors at both ends, to conduct the selection. Compared with the existing selection method that relies solely on rough estimation based on conventional power frequency parameters, the screening results are more in line with the actual operating conditions of low-frequency submarine cables. It avoids safety hazards caused by selecting too small cable specifications, and also avoids redundant engineering investment caused by selecting too large cross-sections. At the same time, it takes into account the long-term operational stability of the equipment and the economic efficiency of project construction, thus improving the versatility of the submarine cable selection method.

[0081] like Figure 2 As shown, based on the above method embodiments, corresponding apparatus embodiments are provided; An embodiment of the present invention provides a submarine cable selection device based on the longest transmission distance, comprising: a first data acquisition module 201, a second data acquisition module 202, a low-frequency rated current carrying capacity determination module 203, a low-frequency rated capacity determination module 204, a limit transmission distance determination module 205, a theoretical longest transmission distance determination module 206, and a submarine cable type determination module 207. The first data acquisition module 201 is used to acquire several types of submarine cables to be evaluated. For each type of submarine cable to be evaluated, it acquires the conductor cross-sectional area, capacitance per unit length, rated voltage and rated current carrying capacity at the first power frequency. The second data acquisition module 202 is used to acquire the ideal active power utilization rate of the submarine cable to be evaluated; and to acquire the preset reactive power compensation degree of the symmetrical reactors at both ends; The low-frequency rated current carrying capacity determination module 203 is used to determine the current carrying capacity correction coefficient based on the conductor cross-sectional area and a preset current carrying capacity correction coefficient fitting formula; and based on the current carrying capacity correction coefficient, correct the calibrated rated current carrying capacity at the first power frequency to the rated current carrying capacity corresponding to the second power frequency, so as to obtain the low-frequency rated current carrying capacity of the submarine cable to be evaluated at the second power frequency; wherein, the second power frequency is less than the first power frequency. The low-frequency rated capacity determination module 204 is used to determine the total apparent capacity of the three phases of the cable at the second power frequency based on the low-frequency rated current carrying capacity and the calibrated rated voltage, and use it as the low-frequency rated capacity. The limit transmission distance determination module 205 is used to establish the submarine cable capacity distance equation based on the low-frequency rated capacity, low-frequency rated current carrying capacity, second power frequency, unit length capacitance, preset first correction fitting coefficient and preset second correction fitting coefficient, and solve the submarine cable capacity distance equation to obtain the limit transmission distance of the submarine cable. The theoretical maximum transmission distance determination module 206 is used to correct the limit transmission distance based on the ideal active power utilization rate and the preset reactive power compensation degree, so as to obtain the theoretical maximum transmission distance of the submarine cable when the ideal active power utilization rate is met. The submarine cable type determination module 207 is used to determine the submarine cable type that meets the engineering requirements based on the theoretical maximum transmission distance of each type of submarine cable to be evaluated.

[0082] The low-frequency rated capacity determination module 204 includes: a low-frequency rated capacity determination subunit; The low-frequency rated capacity determination subunit is used to perform three-phase capacity conversion between the rated voltage and the low-frequency rated current carrying capacity based on the fixed coefficient of the three-phase symmetrical AC system, so as to obtain the total three-phase rated apparent capacity of the cable at the second power frequency.

[0083] The theoretical maximum transmission distance determination module 206 includes: a theoretical maximum transmission distance determination subunit; The theoretical maximum transmission distance determination sub-unit is used to calculate the theoretical maximum transmission distance of the submarine cable when the ideal active power utilization rate is met according to formula (13).

[0084] It is understood that the above-described device embodiments correspond to the method embodiments of the present invention, and can implement the submarine cable selection method based on the longest transmission distance provided by any of the above-described method embodiments of the present invention.

[0085] It should be noted that the device embodiments described above are merely illustrative, and some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can specifically be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0086] Based on the above embodiments of the submarine cable selection method based on the longest transmission distance, another embodiment of the present invention provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the submarine cable selection method based on the longest transmission distance of any embodiment of the present invention.

[0087] For example, in this embodiment, the computer program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the terminal device.

[0088] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0089] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device via various interfaces and lines.

[0090] Based on the above-described method embodiments, another embodiment of the present invention provides a computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to execute the submarine cable selection method based on the longest transmission distance described in any of the above-described method embodiments of the present invention.

[0091] The modules / units integrated in the device / terminal equipment, if implemented as software functional units and sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0092] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for selecting submarine cables based on the longest transmission distance, characterized in that, include: Acquire several types of submarine cables to be evaluated. For each type of submarine cable to be evaluated, obtain the conductor cross-sectional area, capacitance per unit length, rated voltage at the first power frequency, and rated current carrying capacity. To obtain the ideal active power utilization rate of the submarine cable to be evaluated; And obtain the preset reactive power compensation degree of the symmetrical reactors at both ends; The current carrying capacity correction factor is determined based on the conductor cross-sectional area and the preset current carrying capacity correction factor fitting formula. Based on the current carrying capacity correction factor, the calibrated rated current carrying capacity at the first power frequency is corrected to the rated current carrying capacity corresponding to the second power frequency, so as to obtain the low-frequency rated current carrying capacity of the submarine cable to be evaluated at the second power frequency; wherein, the second power frequency is less than the first power frequency; Based on the low-frequency rated current carrying capacity and the calibrated rated voltage, the total three-phase apparent capacity of the cable at the second power frequency is determined as the low-frequency rated capacity. Based on the low-frequency rated capacity, low-frequency rated current carrying capacity, second power frequency, unit length capacitance, preset first correction fitting coefficient and preset second correction fitting coefficient, a submarine cable capacity distance equation is established, and the submarine cable capacity distance equation is solved to obtain the limit transmission distance of the submarine cable. The maximum transmission distance of the submarine cable is theoretically corrected based on the ideal active power utilization rate and the preset reactive power compensation degree to obtain the theoretical maximum transmission distance when the ideal active power utilization rate is met. Based on the theoretical maximum transmission distance of each type of submarine cable to be evaluated, the type of submarine cable suitable for the engineering requirements is determined.

2. The submarine cable selection method based on the longest transmission distance as described in claim 1, characterized in that, The methods for constructing the fitting formula for the current carrying capacity correction coefficient include: Multiple sets of submarine cable test samples with different conductor cross-sectional areas were collected under the same test conditions; each set of submarine cable test samples included a calibrated rated current carrying capacity sample at the first power frequency and a low-frequency rated current carrying capacity sample at the second power frequency, corresponding to the same conductor cross-sectional area. For each set of submarine cable test samples, calculate the ratio of the corresponding low-frequency rated current carrying capacity sample to the calibrated rated current carrying capacity sample to obtain the current carrying capacity correction coefficient sample corresponding to each set of submarine cable test samples. Using the current carrying capacity correction coefficient sample as the dependent variable and the conductor cross-sectional area corresponding to the current carrying capacity correction coefficient sample as the independent variable, a quadratic polynomial is obtained by fitting, which serves as the fitting formula for the current carrying capacity correction coefficient.

3. The submarine cable selection method based on the longest transmission distance as described in claim 2, characterized in that, Based on the low-frequency rated current carrying capacity and rated voltage, the total three-phase apparent capacity of the cable at the second power frequency is determined, including: Based on the fixed coefficient of the three-phase symmetrical AC system, the three-phase capacity is converted between the rated voltage and the low-frequency rated current carrying capacity to obtain the total three-phase apparent capacity of the cable at the second power frequency.

4. The submarine cable selection method based on the longest transmission distance as described in claim 3, characterized in that, The formula for the submarine cable capacity-distance equation is: in, This refers to the active power capacity that the submarine cable can transmit. For low-frequency rated capacity, For the second power frequency, Capacitance per unit length For the maximum transmission distance, To preset the first correction fitting coefficient, To preset the second correction fitting coefficient, It is the low-frequency rated current carrying capacity. It is the calibrated rated voltage.

5. The submarine cable selection method based on the longest transmission distance as described in claim 4, characterized in that, Based on the ideal active power utilization rate and the preset reactive power compensation degree, the maximum transmission distance of the submarine cable is corrected to obtain the theoretical maximum transmission distance when the ideal active power utilization rate is met, including: The theoretical maximum transmission distance of submarine cables while meeting ideal active power utilization rate can be calculated using the following formula: in, This is the theoretical maximum transmission distance of a submarine cable while meeting ideal active power utilization. To preset the reactive power compensation degree, It is the ideal active power utilization rate. It is the maximum transmission distance.

6. A submarine cable selection device based on the longest transmission distance, characterized in that, include: The system includes a first data acquisition module, a second data acquisition module, a low-frequency rated current carrying capacity determination module, a low-frequency rated capacity determination module, a limit transmission distance determination module, a theoretical maximum transmission distance determination module, and a submarine cable type determination module. The first data acquisition module is used to acquire several types of submarine cables to be evaluated. For each type of submarine cable to be evaluated, it acquires the conductor cross-sectional area, capacitance per unit length, rated voltage and rated current carrying capacity at the first power frequency. The second data acquisition module is used to obtain the ideal active power utilization rate of the submarine cable to be evaluated. And obtain the preset reactive power compensation degree of the symmetrical reactors at both ends; The low-frequency rated current carrying capacity determination module is used to determine the current carrying capacity correction coefficient based on the conductor cross-sectional area and a preset current carrying capacity correction coefficient fitting formula. Based on the current carrying capacity correction factor, the calibrated rated current carrying capacity at the first power frequency is corrected to the rated current carrying capacity corresponding to the second power frequency, so as to obtain the low-frequency rated current carrying capacity of the submarine cable to be evaluated at the second power frequency; wherein, the second power frequency is less than the first power frequency; The low-frequency rated capacity determination module is used to determine the total apparent capacity of the cable under the second power frequency based on the low-frequency rated current carrying capacity and the calibrated rated voltage, and use it as the low-frequency rated capacity. The limit transmission distance determination module is used to establish the submarine cable capacity distance equation based on the low-frequency rated capacity, low-frequency rated current carrying capacity, second power frequency, unit length capacitance, preset first correction fitting coefficient and preset second correction fitting coefficient, and solve the submarine cable capacity distance equation to obtain the limit transmission distance of the submarine cable. The theoretical maximum transmission distance determination module is used to correct the limit transmission distance based on the ideal active power utilization rate and the preset reactive power compensation degree, so as to obtain the theoretical maximum transmission distance of the submarine cable when the ideal active power utilization rate is met. The submarine cable type determination module is used to determine the submarine cable type that best suits the engineering requirements based on the theoretical maximum transmission distance of each type of submarine cable to be evaluated.

7. The submarine cable selection device based on the longest transmission distance as described in claim 6, characterized in that, The low-frequency rated capacity determination module includes: a low-frequency rated capacity determination subunit; The low-frequency rated capacity determination subunit is used to perform three-phase capacity conversion between the rated voltage and the low-frequency rated current carrying capacity based on the fixed coefficient of the three-phase symmetrical AC system, so as to obtain the total three-phase rated apparent capacity of the cable at the second power frequency.

8. The submarine cable selection device based on the longest transmission distance as described in claim 7, characterized in that, The module for determining the theoretical maximum transmission distance includes: a subunit for determining the theoretical maximum transmission distance; The theoretical maximum transmission distance determination subunit is used to calculate the theoretical maximum transmission distance of the submarine cable while satisfying the ideal active power utilization rate, based on the following formula: in, This is the theoretical maximum transmission distance of a submarine cable while meeting ideal active power utilization. To preset the reactive power compensation degree, It is the ideal active power utilization rate. It is the maximum transmission distance.

9. A terminal device, characterized in that, The system includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, it implements the submarine cable selection method based on the longest transmission distance as described in any one of claims 1-5.

10. A computer-readable storage medium, characterized in that, include: A stored computer program, wherein, when the computer program is executed, it controls the device containing the computer-readable storage medium to perform the submarine cable selection method based on the longest transmission distance as described in any one of claims 1-5.

Images