A method, system and readable storage medium for estimating high voltage cable induction parameters

Abstract

An embodiment of the present application provides a method, system and readable storage medium for estimating inductive parameters of a high-voltage cable. The method includes obtaining a sheath current generated at a preset detection point for a long-distance high-voltage cable line composed of a plurality of three-phase nine-segment cross-interconnected cable basic units, wherein the detection point includes a direct grounding point located at the left and right ends of the high-voltage cable line; calculating the induced current generated in the line loop according to a superposition calculation relationship between the sheath current and the capacitive current generated at each cable segment; estimating inductive parameters according to the induced current while taking into account multiple non-ideal conditions in actual working conditions, the inductive parameters including the self-inductance of the sheath, the mutual inductance of the A-phase conductor to the B-phase sheath, the mutual inductance of the A-phase conductor to the C-phase sheath, and the mutual inductance of the B-phase conductor to the C-phase sheath.

Description

Technical Field

[0001] The present application relates to the technical field of induction parameter estimation, and in particular to a method, system and readable storage medium for estimating induction parameters of a high-voltage cable. Background Art

[0002] The induction parameters of high-voltage cables are crucial for ground fault diagnosis, reactive power compensation, relay protection, etc. At present, the existing technology mainly relies on electromagnetic field theory to calculate the induction parameters, and there is no online estimation method for the actual parameters. However, due to the limitations of the laying conditions of the actual cable line and the nonlinearity of magnetic induction coupling, this method will be difficult to meet the parallel, symmetrical, and equal length assumptions of electromagnetic field theory, resulting in a large error between the actual induction parameters and the theoretical calculation parameters. Summary of the invention

[0003] The purpose of the embodiments of the present application is to provide a method, system and readable storage medium for estimating high-voltage cable induction parameters, which can reduce the estimation error of high-voltage cable induction parameters.

[0004] The present invention provides a method for estimating inductive parameters of a high-voltage cable, the method comprising the following steps:

[0005] S1. For a long-distance high-voltage cable line composed of a plurality of three-phase nine-section cross-connected cable basic units, obtaining the sheath current generated at a preset detection point, wherein the detection point includes a direct grounding point located at the left and right ends of the high-voltage cable line;

[0006] S2. Calculate the induced current generated in the line loop according to the superposition calculation relationship between the sheath current and the capacitive current generated at each cable section;

[0007] S3. Under the condition of considering multiple non-ideal conditions in actual working conditions, the induction parameters are estimated according to the induced current, and the induction parameters include the self-inductance of the sheath, the mutual inductance of the A-phase conductor to the B-phase sheath, the mutual inductance of the A-phase conductor to the C-phase sheath, and the mutual inductance of the B-phase conductor to the C-phase sheath.

[0008] In a second aspect, an embodiment of the present application further provides a high-voltage cable induction parameter estimation system, the system comprising a sheath current detection module, an induction current calculation module and an induction parameter estimation module, wherein:

[0009] The sheath current detection module is used to obtain the sheath current generated at a preset detection point for a long-distance high-voltage cable line composed of a plurality of three-phase nine-section cross-connected cable basic units, wherein the detection point includes a direct grounding point located at the left and right ends of the high-voltage cable line;

[0010] The induced current calculation module is used to calculate the induced current generated in the line loop according to the superposition calculation relationship between the sheath current and the capacitive current generated at each cable section;

[0011] The induction parameter estimation module is used to estimate the induction parameters according to the induced current while taking into account multiple non-ideal conditions in actual working conditions. The induction parameters include the self-inductance of the sheath, the mutual inductance of the A-phase conductor to the B-phase sheath, the mutual inductance of the A-phase conductor to the C-phase sheath, and the mutual inductance of the B-phase conductor to the C-phase sheath.

[0012] In a third aspect, an embodiment of the present application further provides a readable storage medium, wherein the readable storage medium includes a high-voltage cable induction parameter estimation method program. When the high-voltage cable induction parameter estimation method program is executed by a processor, the steps of a high-voltage cable induction parameter estimation method as described in any one of the above items are implemented.

[0013] As can be seen from the above, the embodiment of the present application provides a method, system and readable storage medium for estimating the inductive parameters of a high-voltage cable. First, the sheath current generated at the direct grounding points at the left and right ends of the high-voltage cable line is obtained, and the inductive current generated in each line loop is calculated based on the superposition calculation relationship between the sheath current and the capacitive current generated at each cable section. Secondly, by utilizing the characteristics that the inductive components of the sheath currents at adjacent cross-connected grounding points of the same sheath loop are the same, and the capacitive components are in opposite directions, the relationship between the inductive parameters and the inductive currents between the three phases and the three sheath loops is established, and based on the inferred inductive current, the inductive parameters are estimated under non-ideal conditions, thereby avoiding the problem of mismatch between the actual inductive parameters and the theoretically calculated parameters, and improving the estimation accuracy of the inductive parameters of the high-voltage cable.

[0014] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by practicing the embodiments of the present application. The purpose and other advantages of the present application can be realized and obtained by the structures specifically pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 A flowchart of a high-voltage cable induction parameter estimation method provided in an embodiment of the present application;

[0017] Figure 2 It is a schematic diagram of the basic unit of the cross-interconnected high-voltage cable;

[0018] Figure 3 It is the arrangement mode of the three phases ABC and the definition form of the geometric spacing of the wire cores under ideal conditions;

[0019] Figure 4 A flowchart for implementing outputting a stable value of a sensing parameter when an error term is substituted;

[0020] Figure 5 This is a diagram showing the implementation effect of the high-voltage cable induction parameter estimation method;

[0021] Figure 6 A schematic diagram of the structure of a high-voltage cable sensing parameter estimation system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0023] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0024] Please refer to Figure 1 , Figure 1 This is a flowchart of a method for estimating high-voltage cable induction parameters in some embodiments of the present application. Taking the method applied to a computer device (the computer device can be a terminal or a server, and the terminal can be, but is not limited to, various personal computers, laptops, smart phones, tablet computers, and portable wearable devices. The server can be an independent server or a server cluster composed of multiple servers) as an example, the method includes the following steps:

[0025] Step S1, for a long-distance high-voltage cable line composed of multiple three-phase nine-segment cross-connected cable basic units, obtain the sheath current generated at a preset detection point, wherein the detection point includes a direct grounding point located at the left and right ends of the high-voltage cable line.

[0026] Step S2, calculating the induced current generated in the line loop according to the superposition calculation relationship between the sheath current and the capacitive current generated at each cable section.

[0027] Step S3, under the condition of considering multiple non-ideal conditions in actual working conditions, the induction parameters are estimated according to the induced current, and the induction parameters include the self-inductance of the sheath, the mutual inductance of the A-phase conductor to the B-phase sheath, the mutual inductance of the A-phase conductor to the C-phase sheath, and the mutual inductance of the B-phase conductor to the C-phase sheath.

[0028] As can be seen from the above, a method for estimating the inductive parameters of a high-voltage cable provided in an embodiment of the present application first obtains the sheath current generated at the direct grounding points at the left and right ends of the high-voltage cable line, and calculates the induced current generated in each line loop based on the superposition calculation relationship between the sheath current and the capacitive current generated at each cable section. Secondly, by utilizing the characteristics that the sheath current inductive components of adjacent cross-interconnected grounding points of the same sheath loop are the same and the capacitive components are in opposite directions, the relationship between the inductive parameters and the induced current between the three phases and the three sheath loops is established, and based on the inferred induced current, the inductive parameters are estimated under non-ideal conditions, thereby avoiding the problem of mismatch between the actual inductive parameters and the theoretically calculated parameters, and improving the estimation accuracy of the inductive parameters of the high-voltage cable.

[0029] In one of the embodiments, in step S1, the long-distance high-voltage cable line includes three sheath loops, wherein: the first sheath loop is composed of 1, 5 and 9 cable segments; the second sheath loop is composed of 2, 6 and 7 cable segments; the third sheath loop is composed of 3, 4 and 8 cable segments; the sheath current at the direct grounding point is collected by a direct grounding box connected to the detection point, and a current transformer is provided in the direct grounding box.

[0030] For details, please refer to Figure 2 The high-voltage cable line disclosed in the embodiment of the present application includes three sheath loops, wherein each sheath loop is composed of three sections of cable. It can be understood that Figure 2 The part marked with "1" can be understood as 1 section of cable, and the part marked with "4" can be understood as 4 sections of cable, which will not be described in detail in the present embodiment. Figure 2 It is clear that the cable sections 1 to 3 shown in the figure correspond to the direct grounding points at the left end of the high-voltage cable line, and the cable sections 7 to 9 correspond to the direct grounding points at the right end of the high-voltage cable line.

[0031] In one embodiment, in step S2, the induced current generated in the line loop is calculated according to the superposition calculation relationship between the sheath current and the capacitive current generated at each cable segment, including:

[0032] Step S21, determining the vector superposition result of three-segment capacitive current according to the difference between the sheath currents at the left and right detection points of the same sheath loop.

[0033] Specifically, based on Figure 2 It can be seen that the capacitive current of the high-voltage cable flows to two direct grounding points respectively, and the capacitive currents flowing to the two direct grounding points are equal in magnitude and opposite in direction. Therefore, in the current embodiment, the difference of the sheath current generated at the left and right detection points of the same sheath loop is the vector superposition result of the three-segment capacitive current. For example, for the first sheath loop composed of 1, 5 and 9 segments of cable, the sheath current I generated at the left and right detection points of the first sheath loop is a1 ,I c2 The difference is the capacitive current I generated at the cable sheath of sections 1, 5 and 9. C1 ,I C5 and I C9 The difference between the sheath currents at the left and right detection points of other sheath loops can be derived according to the above steps, and this embodiment of the present application does not limit this.

[0034] Step S22, calculating the induced currents generated by the three sheath loops according to the sheath current, the first vector superposition result of the capacitive current flowing to the left, and the second vector superposition result of the capacitive current flowing to the left.

[0035] Specifically, since the capacitance parameters of the high-voltage cable remain basically unchanged after leaving the factory, and the capacitance current per unit length also remains basically unchanged. Based on step S22, the sheath current I a1 ~I c2 It is known that, according to the sheath current I a1 ~I c2 When the vector superposition results of the corresponding three-segment capacitive current are also known, the induced current generated by the three sheath loops can be obtained based on the calculation rule that the induced current is determined according to the sheath current and the superposition results of the current flowing to the capacitive current.

[0036] In one embodiment, in step S21, the vector superposition result of the three-segment capacitor current is determined by the following formula:

[0037] I c2 -I a1 =I C1 +I C5 +I C9; (1)

[0038] I a2 -I b1 =I C2 +I C6 +I C7 ; (2)

[0039] I b2 -I c1 =I C3 +I C4 +I C8 ; (3)

[0040] Among them, I a1 ,I b1 ,I c1 ,I a2 ,I b2 and I c2 are respectively the sheath current measured at the direct grounding point, I C1 ,I C2 ,I C3 ,I C4 ,I C5 ,I C6 ,I C7 ,I C8 and I C9 They are the capacitive currents generated at the sheaths of cable sections 1, 2, 3, 4, 5, 6, 7, 8 and 9 respectively.

[0041] Specifically, in the sheath current I a1 ~I c2 If all are known, the computer device will calculate the sheath current I obtained in step S1. a1 ~I c2 Substituting into the above formula (1) to formula (3), the superposition result of the corresponding three-segment capacitive current in each sheath loop can be obtained.

[0042] In one embodiment, in step S22, the induced currents generated by the three sheath loops are calculated respectively by the following formula:

[0043] I a1 =I L1 -0.5(I C1 +I C5 +I C9 ); (4)

[0044] I b1 =I L2 -0.5(I C2 +I C6 +I C7 ); (5)

[0045] I c1 =I L3 -0.5(I C3 +I C4 +I C8 ); (6)

[0046] I a2 =I L1 +0.5(I C1 +I C5 +I C9 ); (7)

[0047] I b2 =I L2 +0.5(I C2 +I C6 +I C7 ); (8)

[0048] I c2 =I L3 +0.5(I C3 +I C4 +I C8 ); (9)

[0049] Among them, I L1 ,I L2 and I L3 are the induced currents generated by the three sheath loops. Based on formulas (4)-(6), it can be determined that I a1 ,I b1 and I c1 According to the first vector superposition result of the capacitive current flowing to the left (for example, for the first sheath loop, the first vector superposition result is based on “I C1 +I C5 +I C9 ” determined) and the induced current I generated by the sheath loop L1 ~I L3 Determined. a2 ,I b2 and I c2 According to the second vector superposition result of the capacitive current flowing to the right and the induced current I generated by the sheath loop L1 ~I L3 Determined.

[0050] Specifically, based on step S21, the sum of the corresponding three-segment capacitance current in each sheath loop and the sheath current I a1 ~I c2 If the above parameters are known, the induced current I generated by the three sheath loops can be obtained by substituting the above known parameters into the above formulas (4) to (9). L1~I L3 .

[0051] In one embodiment, in step S3, the estimating the sensing parameter according to the induced current includes:

[0052] Step S31, modeling the sensing parameters according to the cable structural parameters and the error terms substituted under non-ideal conditions, wherein the cable structural parameters include the equivalent inner and outer radii of the sheath and the geometric spacing of the wire cores.

[0053] Specifically, the high-voltage cable contains two parts: self-inductance and mutual inductance. When the phases and relative sheaths of the high-voltage cable meet the conditions of parallelism, symmetry, and equal length (i.e., under ideal conditions), Figure 3 The high-voltage cable arrangement shown in the figure, the computer equipment will model the sensing parameters based on Maxwell's equations, where the specific modeling form can refer to the subsequent formulas (10)-(13), and the selection of cable structure parameters can refer to Figure 3 .

[0054] In one of the embodiments, in actual working conditions, since it is difficult for the high-voltage cable phases and the sheaths to meet ideal conditions such as parallelism, symmetry, and equal length, the computer equipment needs to add error terms and linearize the nonlinear problem when modeling the sensing parameters.

[0055] Step S32, determining a calculation method of the inductance parameters according to the induction parameters obtained by modeling, wherein the inductance parameters include the induced electromotive force generated on the sheath due to the A-phase current, the B-phase current and the C-phase current.

[0056] Specifically, computer equipment is based on Faraday's law of electromagnetic induction. Figure 2 Taking the first section as an example, the sheath is exposed to the current I A 、B phase current I B And the C phase current I C The generated induced electromotive force e1 is determined by the product of the cumulative sum of the three-phase cable core current and the mutual inductance of the three-phase cable core and the first cable sheath, the system angular frequency ω, and the length l1 of the first cable, that is:

[0057] e1=-jωl1(I A L s +I B M B1 +I C M C1 ); (17)

[0058] Among them, L S is the self-inductance per unit length, M B1 For the B phase Figure 2 The mutual inductance of the first cable segment shown in the figure, MC1 For the C phase Figure 2 The mutual inductance of the first cable section shown in FIG.

[0059] It should be noted that the induced electromotive forces e2 to e9 generated on other cable sections can also be further obtained based on the above principle, and the embodiments of the present application do not limit this.

[0060] Step S33 , based on the proportional relationship between the induced current and the inductance parameter, the induced parameter is estimated when the calculation method of the induced current and the inductance parameter is known.

[0061] Specifically, since the induced current is proportional to the inductance parameter, in the current embodiment, the computer device can estimate the inductance parameter by calculating the induced current component in the sheath current.

[0062] In one embodiment, in step S31, the modeling form of the sensing parameters includes:

[0063]

[0064]

[0065]

[0066]

[0067] Among them, L S is the self-inductance of the sheath, M AB is the mutual inductance of phase A conductor to phase B sheath, M AC is the mutual inductance of phase A conductor to phase C sheath, M BC is the mutual inductance of the B-phase conductor to the C-phase sheath; r2 is the equivalent inner radius of the sheath, r3 is the equivalent outer radius of the sheath; d AB d is the distance between the two-phase wire cores AB, AC is the distance between the two phase AC lines, d BC is the distance between the two-phase wire cores of BC; e ls 、e MAB 、e MAC 、e MBC These are all error terms introduced under non-ideal conditions.

[0068] Specifically, for the error terms substituted into equations (10) to (13), in the case of long-time sampling, since the error terms conform to Gaussian distribution, in the current embodiment, the computer device can estimate the expectation and variance of the Gaussian distribution by least squares, and thus obtain a stable value of the sensing parameter.

[0069] In one of the embodiments, when specifying the embodiment, reference may be made to Figure 4The computer device can set a loop based on the least squares minimum principle of the expected residual error; wherein, in each loop, the computer device will use 1 cycle (i.e., the preset sampling time) + 20ms of sampling data for iterative calculation until the expected residual mean is less than 1nH (this limit value will be different in different embodiments, and the embodiment of the present application does not limit this), and then output the result (i.e., the stable value of the output sensing parameter). In one embodiment, please refer to Figure 5 , the induction parameter error terms substituted into equations (10) to (13) will tend to be stable within 10 cycles.

[0070] In one embodiment, in step S32, the inductance parameters generated on each cable segment are determined based on the product of the three-phase cable core current and the corresponding cable sheath mutual inductance, the system angular frequency, and the product of the lengths of each cable segment.

[0071] Specifically, the inductance parameters e1 to e9 generated on each cable segment can refer to the following formula:

[0072] e1=-jωl1(I A L s +I B M B1 +I C M C1 ); (18)

[0073] e2=-jωl2(I B L s +I A M A2 +I C M C2 ); (19)

[0074] e3=-jωl3(I C L s +I B M B3 +I A M A3 ); (20)

[0075] e4=-jωl4(I A L S +I B M B4 +I C M C4 ); (twenty one)

[0076] e5=-jωl5(I B L S +I A M A5 +I C M C5); (twenty two)

[0077] e6=-jωl6(I C L S +I B M B6 +I A M A6 ); (twenty three)

[0078] e7=-jωl7(I A L S +I B M B7 +I C M C7 ); (twenty four)

[0079] e8=-jωl8(I B L S +I A M A8 +I C M C8 ); (25)

[0080] e9=-jωl9(I C L S +I B M B9 +I A M A9 ); (26)

[0081] Among them, l i is the length of the i-th cable segment; L s is the self-inductance per unit length, which can be obtained from formula (10); M Pi (P=A,B,C,i=1,2,…,9) is the Pth phase and Figure 2 The mutual inductance of the i-th cable section shown in , which can be obtained by equations (11) to (13); ω is the system angular frequency.

[0082] In step S33, the proportional relationship between the induced current and the inductance parameter includes:

[0083]

[0084]

[0085]

[0086] Among them, e1~e9 are the induced electromotive force generated on the cable sheath of sections 1~9 respectively; I L1 ,I L2 and I L3are the induced currents generated by the three sheath loops; Z1~Z9 are the impedances of cable sheaths in sections 1~9, e is the earth impedance.

[0087] Specifically, Figure 2 As shown in the figure, the long-distance high-voltage cable is composed of multiple three-phase nine-section cross-interconnected cable basic units, among which the induced electromotive force of the three sheath loops 1-5-9, 2-6-7, and 3-4-8 conforms to the superposition principle. Based on the reference calculation formulas (18) to (26) of the above inductance parameters e1 to e9, the superposition sum of the induced electromotive force generated by each sheath loop is:

[0088] e1+e5+e9=-jωl((I A +I B +I C )L s +I A (M A5 +M A9 )+I B (M B1 +M B9 )+I C (M C1 +M C5 )); (27)

[0089] e2+e6+e7=-jωl((I A +I B +I C )L s +I A (M A2 +M A6 )+I B (M B6 +M B7 )+I C (M C2 +M C7 )); (28)

[0090] e3+e4+e8=-jωl((I A +I B +I C )L s +I A (M A3 +M A8 )+I B (M B3 +M B4 )+I C (M C4 +M C8 )); (29)

[0091] Wherein, the above formulas (27) to (29) are substituted into formulas (14) to (16), and when Z1 to Z9 and Z e In the case of , the induced current I generated by the three sheath loops can be obtained L1 ~I L3 At this point, the relationship between the induced current and the induced parameters has been established.

[0092] In one embodiment, the complete estimation process of the sensing parameters can be referred to Figure 4 , specifically including the following steps:

[0093] (1) Based on the preset cable structural parameters and taking into account the error term, the cable self-inductance L is calculated using formulas (10) to (13): S , and the mutual inductance M AB 、M AC 、M BC .

[0094] (2) Using the measured sheath current I a1 ~I c2 , first calculate the capacitor current I through formula (1) to formula (3) C1 ~I C9 , then, based on the capacitor current I C1 ~I C9 , the induced current I is calculated by using formula (4) to formula (9) L1 ,I L2 and I L3 Finally, the sensing parameters and their errors are estimated by taking the error terms into consideration (Formula (14) to Formula (16)).

[0095] (3) To ensure the stability of the output results, a loop setting based on the least squares minimum principle of the expected residual of the error is considered. In each loop, iterative calculation is performed using 1-cycle 20ms sampling data until the expected residual mean is less than 1nH, and then the result is output.

[0096] The above is the overall implementation process of the high-voltage cable induction parameter estimation method disclosed in the embodiment of the present application, wherein, first, a normal distribution probability model containing induction parameter errors is proposed to be established (i.e., formula (10) to formula (13)), and the induction current components of each loop are calculated according to the detected sheath current (i.e., formula (4) to formula (9)); then, the sheath current induction components of adjacent cross-connected grounding points of the same sheath loop are the same, and the capacitive components are in opposite directions. The linear equation group of the induction parameters and the induction current between the three phases and the three sheath loops is constructed (i.e., formula (14) to formula (16)); finally, the expectation and variance of the induction parameter probability function are determined according to the principle of minimum least squares residual of long-time sampling to ensure the stability of the output results and reduce the estimation error of the induction parameters of the high-voltage cable.

[0097] Please refer to Figure 6 As shown, the embodiment of the present application further provides a high-voltage cable induction parameter estimation system 600, the system 600 includes a sheath current detection module 601, an induction current calculation module 602 and an induction parameter estimation module 603, wherein:

[0098] The sheath current detection module 601 is used to obtain the sheath current generated at a preset detection point for a long-distance high-voltage cable line composed of multiple three-phase nine-segment cross-interconnected cable basic units, wherein the detection point includes a direct grounding point located at the left and right ends of the high-voltage cable line.

[0099] The induced current calculation module 602 is used to calculate the induced current generated in the line loop according to the superposition calculation relationship between the sheath current and the capacitive current generated at each cable section.

[0100] The induction parameter estimation module 603 is used to estimate the induction parameters according to the induced current while taking into account multiple non-ideal conditions in actual working conditions. The induction parameters include the self-inductance of the sheath, the mutual inductance of the A-phase conductor to the B-phase sheath, the mutual inductance of the A-phase conductor to the C-phase sheath, and the mutual inductance of the B-phase conductor to the C-phase sheath.

[0101] In one of the embodiments, the system 600 may also execute the method in any optional implementation of the above embodiments to ensure accurate estimation of the sensing parameters.

[0102] The above-mentioned high-voltage cable induction parameter estimation system first obtains the sheath current generated at the direct grounding points at the left and right ends of the high-voltage cable line, and calculates the induced current generated in each line loop based on the superposition calculation relationship between the sheath current and the capacitive current generated at each cable section. Secondly, by utilizing the characteristics that the sheath current induction components of adjacent cross-connected grounding points of the same sheath loop are the same and the capacitive components are in opposite directions, the relationship between the induction parameters and the induced current between the three phases and the three sheath loops is established, and based on the calculated induced current, the induction parameters are estimated under non-ideal conditions, avoiding the problem of mismatch between the actual induction parameters and the theoretical calculation parameters, and improving the estimation accuracy of the high-voltage cable induction parameters.

[0103] A readable storage medium provided in an embodiment of the present application, when the computer program is executed by a processor, executes the method in any optional implementation of the above embodiment. Wherein, the storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (Static Random Access Memory, referred to as SRAM), electrically erasable programmable read-only memory (Electrically Erasable Programmable Read-Only Memory, referred to as EEPROM), erasable programmable read-only memory (Erasable Programmable Read Only Memory, referred to as EPROM), programmable read-only memory (Programmable Red-Only Memory, referred to as PROM), read-only memory (Read-Only Memory, referred to as ROM), magnetic memory, flash memory, disk or optical disk.

[0104] The above-mentioned readable storage medium first obtains the sheath current generated at the direct grounding points at the left and right ends of the high-voltage cable line, and calculates the induced current generated in each line loop based on the superposition calculation relationship between the sheath current and the capacitive current generated at each cable section. Secondly, by utilizing the characteristics that the sheath current induction components of adjacent cross-connected grounding points of the same sheath loop are the same and the capacitive components are in opposite directions, the relationship between the induction parameters and the induced current between the three phases and the three sheath loops is established, and based on the inferred induced current, the induction parameters are estimated under non-ideal conditions, thereby avoiding the mismatch between the actual induction parameters and the theoretical calculation parameters, and improving the estimation accuracy of the induction parameters of the high-voltage cable.

[0105] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0106] In addition, the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0107] Furthermore, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist independently, or two or more modules may be integrated to form an independent part.

[0108] In this document, relational terms such as first and second, etc. are used merely to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0109] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for estimating inductive parameters of a high-voltage cable, characterized in that: The method comprises the following steps: S1. For a long-distance high-voltage cable line composed of a plurality of three-phase nine-section cross-connected cable basic units, obtaining the sheath current generated at a preset detection point, wherein the detection point includes a direct grounding point located at the left and right ends of the high-voltage cable line; S2. Calculate the induced current generated in the line loop according to the superposition calculation relationship between the sheath current and the capacitive current generated at each cable section; S3. Under the condition of considering multiple non-ideal conditions in actual working conditions, the induction parameters are estimated according to the induced current, wherein the induction parameters include the self-inductance of the sheath, the mutual inductance of the A-phase conductor to the B-phase sheath, the mutual inductance of the A-phase conductor to the C-phase sheath, and the mutual inductance of the B-phase conductor to the C-phase sheath; In step S3, the estimating sensing parameters according to the induced current includes: S31, modeling the sensing parameters according to the cable structural parameters and the error terms substituted under non-ideal conditions, wherein the cable structural parameters include the equivalent inner and outer radii of the sheath and the geometric spacing of the wire cores; S32, determining a calculation method of the inductance parameters according to the induction parameters obtained by the modeling, wherein the inductance parameters include the induced electromotive force generated on the sheath due to the A-phase current, the B-phase current, and the C-phase current; S33, based on the positive proportional relationship between the induced current and the inductance parameter, when the calculation method of the induced current and the inductance parameter is known, estimating the induced parameter; In step S31, the modeling form of the sensing parameters includes: Among them, L S is the self-inductance of the sheath, M AB is the mutual inductance of phase A conductor to phase B sheath, M AC is the mutual inductance of phase A conductor to phase C sheath, M BC is the mutual inductance of the B-phase conductor to the C-phase sheath; r2 is the equivalent inner radius of the sheath, r3 is the equivalent outer radius of the sheath; d AB d is the distance between the two-phase wire cores AB, AC is the distance between the two phase AC lines, d BC is the distance between the two-phase wire cores of BC; e ls 、e MAB 、e MAC 、e MBC These are all error terms substituted under non-ideal conditions; In step S32, the inductance parameters generated on each cable segment are determined by the following formula, based on the product of the three-phase cable core current and the corresponding cable sheath mutual inductance, the system angular frequency, and the product of the lengths of each cable segment; e1=-jωl1(I A L s +I B M B1 +I C M C1 );(18) e2=-jωl2(I B L s +I A M A2 +I C M C2 );(19) e3=-jωl3(I C L s +I B M B3 +I A M A3 );(20) e4=-jωl4(I A L S +I B M B4 +I C M C4 );(21) e5=-jωl5(I B L S +I A M A5 +I C M C5 );(22) e6=-jωl6(I C L S +I B M B6 +I A M A6 );(23) e7=-jωl7(I A L S +I B M B7 +I C M C7 );(24) e8=-jωl8(I B L S +I A M A8 +I C M C8 );(25) e9=-jωl9(I C L S +I B M B9 +I A M A9 );(26) Where, ω is the system angular frequency, l i is the length of the cable in the ith section, I A is the A-phase current on the cable sheath, I B is the B-phase current on the cable sheath, I C is the C phase current on the cable sheath, L S The self-inductance per unit length is determined by formula (10), M Pi is the mutual inductance between the Pth phase and the i-th cable section, P = A, B, C, i = 1, 2, ..., 9, determined by formulas (11) to (13); In step S33, the proportional relationship between the induced current and the inductance parameter includes: Among them, e1~e9 are the induced electromotive force generated on the cable sheath of sections 1~9 respectively; I L1 ,I L2 and I L3 are the induced currents generated by the three sheath loops; Z1~Z9 are the impedances of cable sheaths in sections 1~9, e is the earth impedance.

2. The method according to claim 1, characterized in that In step S1, the long-distance high-voltage cable line includes three sheath loops, wherein: The first sheath loop consists of 1, 5 and 9 cable segments; The second sheath loop consists of 2, 6 and 7 cable segments; The third sheath loop consists of 3, 4 and 8 cable segments; The sheath current at the direct grounding point is collected by a direct grounding box connected to the detection point, wherein a current transformer is provided in the direct grounding box.

3. The method according to claim 2, characterized in that In step S2, the induced current generated in the line loop is calculated according to the superposition calculation relationship between the sheath current and the capacitive current generated at each cable segment, including: S21, determining the vector superposition result of the three-segment capacitive current according to the difference between the sheath currents at the left and right detection points of the same sheath loop; S22, calculating the induced currents generated by the three sheath loops according to the sheath current, the first vector superposition result of the capacitor current flowing to the left, and the second vector superposition result of the capacitor current flowing to the left.

4. The method according to claim 3, characterized in that In step S21, the vector superposition result of the three-segment capacitor current is determined by the following formula: I c2 -I a1 =I C1 +I C5 +I C9 ; (1) I a2 -I b1 =I C2 +I C6 +I C7 ;(2) I b2 -I c1 =I C3 +I C4 +I C8 ;(3) Among them, I a1 ,I b1 ,I c1 ,I a2 ,I b2 and I c2 are respectively the sheath current measured at the direct grounding point, I C1 ,I C2 ,I C3 ,I C4 ,I C5 ,I C6 ,I C7 ,I C8 and I C9 They are the capacitive currents generated at the sheaths of cable sections 1, 2, 3, 4, 5, 6, 7, 8 and 9 respectively.

5. The method according to claim 4, characterized in that In step S22, the induced currents generated by the three sheath loops are calculated respectively by the following formulas: I a1 =I L1 -0.5(I C1 +I C5 +I C9 );(4) I b1 =I L2 -0.5(I C2 +I C6 +I C7 );(5) I c1 =I L3 -0.5(I C3 +I C4 +I C8 );(6) I a2 =I L1 +0.5(I C1 +I C5 +I C9 );(7) I b2 =I L2 +0.5(I C2 +I C6 +I C7 ); (8) I c2 =I L3 +0.5(I C3 +I C4 +I C8 ); (9) Among them, I L1 ,I L2 and I L3 These are the induced currents generated by the three sheath loops respectively.

6. A high voltage cable induction parameter estimation system, characterized in that: The system comprises a sheath current detection module, an induced current calculation module and an induced parameter estimation module, wherein: The sheath current detection module is used to obtain the sheath current generated at a preset detection point for a long-distance high-voltage cable line composed of a plurality of three-phase nine-section cross-connected cable basic units, wherein the detection point includes a direct grounding point located at the left and right ends of the high-voltage cable line; The induced current calculation module is used to calculate the induced current generated in the line loop according to the superposition calculation relationship between the sheath current and the capacitive current generated at each cable section; The induction parameter estimation module is used to estimate the induction parameters according to the induced current under the condition of considering multiple non-ideal conditions in actual working conditions, and the induction parameters include the self-inductance of the sheath, the mutual inductance of the A-phase conductor to the B-phase sheath, the mutual inductance of the A-phase conductor to the C-phase sheath, and the mutual inductance of the B-phase conductor to the C-phase sheath; The specific implementation of estimating the sensing parameters according to the induced current is: Modeling of sensing parameters is performed based on cable structural parameters and error terms substituted under non-ideal conditions, wherein the cable structural parameters include equivalent inner and outer radii of the sheath and geometric spacing of the cores; Determine a calculation method of the inductance parameters according to the induction parameters obtained by the modeling, wherein the inductance parameters include the induced electromotive force generated on the sheath due to the A-phase current, the B-phase current and the C-phase current; Based on the positive proportional relationship between the induced current and the inductance parameter, the induction parameter is estimated when the induced current and the calculation method of the inductance parameter are known; The modeling form of the sensing parameters includes: Among them, L S is the self-inductance of the sheath, M AB is the mutual inductance of phase A conductor to phase B sheath, M AC is the mutual inductance of phase A conductor to phase C sheath, M BC is the mutual inductance of the B-phase conductor to the C-phase sheath; r2 is the equivalent inner radius of the sheath, r3 is the equivalent outer radius of the sheath; d AB d is the distance between the two-phase wire cores AB, AC is the distance between the two phase AC lines, d BC is the distance between the two-phase wire cores of BC; e ls 、e MAB 、e MAC 、e MBC These are all error terms substituted under non-ideal conditions; The inductance parameters generated on each cable section are determined by the product of the three-phase cable core current and the corresponding cable sheath mutual inductance, the system angular frequency, and the length of each cable section; e1=-jωl1(I A L s +I B M B1 +I C M C1 );(18) e2=-jωl2(I B L s +I A M A2 +I C M C2 );(19) e3=-jωl3(I C L s +I B M B3 +I A M A3 );(20) e4=-jωl4(I A L S +I B M B4 +I C M C4 );(21) e5=-jωl5(I B L S +I A M A5 +I C M C5 );(22) e6=-jωl6(I C L S +I B M B6 +I A M A6 );(23) e7=-jωl7(I A L S +I B M B7 +I C M C7 );(24) e8=-jωl8(I B L S +I A M A8 +I C M C8 );(25) e9=-jωl9(I C L S +I B M B9 +I A M A9 );(26) Where, ω is the system angular frequency, l i is the length of the cable in the ith section, I A is the A-phase current on the cable sheath, I B is the B-phase current on the cable sheath, I C is the C phase current on the cable sheath, L S The self-inductance per unit length is determined by formula (10), M Pi is the mutual inductance between the Pth phase and the i-th cable section, P = A, B, C, i = 1, 2, ..., 9 determined by formulas (11) to (13); The proportional relationship between the induced current and the inductance parameter includes: Among them, e1~e9 are the induced electromotive force generated on the cable sheath of sections 1~9 respectively; I L1 ,I L2 and I L3 are the induced currents generated by the three sheath loops; Z1~Z9 are the impedances of cable sheaths in sections 1~9, e is the earth impedance.

7. A computer-readable storage medium, characterized in that: The storage medium includes a high-voltage cable induction parameter estimation method program, and when the high-voltage cable induction parameter estimation method program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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