Induced current vector synthesis analysis method and device for high-voltage cable grounding system

Abstract

The invention belongs to the field of electric power, and discloses a high-voltage cable grounding system induced current vector synthesis analysis method and device, and the method comprises the steps: synchronously collecting grounding current signals of a three-phase metal sheath of a high-voltage cable and synthesis current signals of each phase wire core through double Rogowski coils with consistent linearity, the synthesized current signal is a superposition value of the running current and the circulating current component; carrying out point-by-point subtraction on the synthetic current sampling value and the grounding current sampling value which are in the same phase so as to counteract a ring current component in the synthetic current signal; absolute values of the difference signals are obtained and summed, and a summed value is converted into a real operation current value through a preset segmented calibration curve; respectively carrying out discrete Fourier transform on the grounding current signal and the difference signal, representing by complex numbers of the two signals under power frequency, and calculating a quotient represented by the complex numbers to obtain a phase difference between the grounding current signal and the difference signal; and determining the system state of the high-voltage cable grounding system based on the operation current value and the phase difference.

Description

Technical Field

[0001] This invention belongs to the field of power, and particularly relates to a method and apparatus for vector synthesis analysis of induced current in high-voltage cable grounding systems. Background Technology

[0002] High-voltage cables are an important component of urban power grids. The grounding method of their metal sheath and the state of the grounding system directly affect the cable's current carrying capacity, insulation life, and operational safety.

[0003] In related technologies, the inspection of high-voltage cable grounding systems mainly relies on regular manual inspections. This involves measuring the amplitude of the grounding current using clamp-on ammeters and combining this with experience to determine if the system has faults such as multiple grounding points or sheath damage. However, due to the linearity limitations of clamp-on ammeters, this method has significant errors when measuring small currents and cannot accurately measure phase, making precise vector analysis impossible. Furthermore, the current flowing through the metallic sheath of high-voltage cables consists of a superposition of operating current (load current) and circulating current (induced current, capacitive leakage current). Traditional methods cannot effectively separate these two components, easily leading to distortions in the assessment of the operating current. Summary of the Invention

[0004] In view of this, the present invention discloses a method and apparatus for vector synthesis analysis of induced current in high-voltage cable grounding systems, which can solve the shortcomings of related technologies.

[0005] To achieve the above objectives, the present invention discloses the following technical solution: According to a first aspect of the present invention, a method for vector synthesis analysis of induced current in a high-voltage cable grounding system is proposed, comprising: The grounding current signal of the three-phase metal sheath of the high-voltage cable and the composite current signal of each phase conductor are synchronously acquired by dual Rogowski coils with consistent linearity. The composite current signal is the superposition value of the operating current and the circulating current component. After converting the acquired current signal into digital sampled values, the composite current sampled values ​​with the ground current sampled values ​​in the same phase are subtracted point by point to cancel the circulating current component in the composite current signal, and the difference signal proportional to the operating current is extracted. The absolute value of the difference signal is taken and summed, and the summation value is converted into the actual operating current value through a preset piecewise calibration curve; Discrete Fourier transforms are performed on the ground current signal and the difference signal respectively, and the two signals are represented by complex numbers at the power frequency. The phase difference between the ground current signal and the difference signal is obtained by calculating the quotient of the complex number representation. The system state of the high-voltage cable grounding system is determined based on the operating current value and the phase difference.

[0006] According to a second aspect of the present invention, a vector synthesis analysis device for induced current in a high-voltage cable grounding system is provided, the device comprising: Acquisition Unit: The grounding current signal of the three-phase metal sheath of the high-voltage cable and the composite current signal of each phase conductor are synchronously acquired by two Rogowski coils with consistent linearity. The composite current signal is the superposition value of the operating current and the circulating current component. Elimination unit: After converting the acquired current signal into digital sampled values, the composite current sampled value with the ground current sampled value in the same phase is subtracted point by point to cancel the circulating current component in the composite current signal, and the difference signal proportional to the operating current is extracted. Conversion unit: Takes the absolute value of the difference signal and sums it, and converts the summation value into the actual operating current value through a preset segmented calibration curve; Solving unit: Performs discrete Fourier transform on the grounding current signal and the difference signal respectively, expresses the two signals in complex number representation at power frequency, and obtains the phase difference between the grounding current signal and the difference signal by calculating the quotient of the complex number representation; Determination Unit: Determines the system state of the high-voltage cable grounding system based on the operating current value and the phase difference.

[0007] According to a third aspect of the present invention, an electronic device is provided, comprising: processor; Memory used to store processor-executable instructions; The processor implements the steps of the method as described in the first aspect by running the executable instructions.

[0008] According to a fourth aspect of the invention, a computer-readable storage medium is provided having computer instructions stored thereon that, when executed by a processor, implement the steps of the method as described in the first aspect.

[0009] As can be seen from the above technical solutions, the vector synthesis and analysis method for induced current in high-voltage cable grounding systems disclosed in this invention is as follows: On the one hand, by utilizing dual Rogowski coils with consistent linearity and subtracting digital sample values ​​point by point, the circulating current component in the synthesized current signal is canceled out, thereby extracting the pure operating current and solving the problem of traditional methods being unable to separate current components. On the other hand, the phase difference is calculated using discrete Fourier transform and the complex quotient method, avoiding the cumulative error caused by two calculations in traditional methods, thus improving the accuracy of phase analysis. Furthermore, not only is the state determination of high-voltage cable grounding systems achieved based on operating current values ​​and phase differences, but also nonlinear errors across the entire measurement range are compensated for through preset segmented calibration curves, ensuring the accuracy of the measurement results. Attached Figure Description

[0010] Figure 1 This is a flowchart of an exemplary embodiment of a method for vector synthesis and analysis of induced current in a high-voltage cable grounding system; Figure 2 This is a schematic diagram of a cable double-π lumped parameter model provided in an exemplary embodiment; Figure 3 This is a schematic diagram of an equivalent model of a cable cross-connection grounding system provided in an exemplary embodiment; Figure 4 This is a schematic diagram of a DFT algorithm flow provided in an exemplary embodiment; Figure 5 This is a schematic diagram of an ADC sampling process provided in an exemplary embodiment; Figure 6 This is a schematic structural diagram of a device provided in an exemplary embodiment; Figure 7 This is a block diagram of an exemplary embodiment of a vector synthesis and analysis device for induced current in a high-voltage cable grounding system. Detailed Implementation

[0011] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with one or more embodiments of the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of one or more embodiments of the present invention as detailed in the appended claims.

[0012] It should be noted that in other embodiments, the corresponding methods are not necessarily performed in the order shown and described in this invention. The method comprises steps. In some other embodiments, the method may include more or fewer steps than those described in this invention. Furthermore, a single step described in this invention may be broken down into multiple steps in other embodiments; and multiple steps described in this invention may be combined into a single step in other embodiments.

[0013] High-voltage cables are an important component of urban power grids. The grounding method of their metal sheath and the state of the grounding system directly affect the cable's current carrying capacity, insulation life, and operational safety.

[0014] In related technologies, the inspection of high-voltage cable grounding systems mainly relies on regular manual inspections. This involves measuring the amplitude of the grounding current using clamp-on ammeters and combining this with experience to determine if the system has faults such as multiple grounding points or sheath damage. However, due to the linearity limitations of clamp-on ammeters, this method has significant errors when measuring small currents and cannot accurately measure phase, making precise vector analysis impossible. Furthermore, the current flowing through the metallic sheath of high-voltage cables consists of a superposition of operating current (load current) and circulating current (induced current, capacitive leakage current). Traditional methods cannot effectively separate these two components, easily leading to distortions in the assessment of the operating current.

[0015] To address the shortcomings in related technologies, this invention proposes a method and apparatus for vector synthesis analysis of induced current in high-voltage cable grounding systems.

[0016] Figure 1 This is a flowchart illustrating an exemplary embodiment of a method for vector synthesis and analysis of induced current in a high-voltage cable grounding system. (See flowchart for example.) Figure 1 As shown, the method may include the following steps: Step 101: Synchronously acquire the grounding current signal of the three-phase metal sheath of the high-voltage cable and the composite current signal of each phase conductor by using two Rogowski coils with consistent linearity. The composite current signal is the superposition value of the operating current and the circulating current component.

[0017] High-voltage cables are typically single-core structures, consisting of two conductors: the conductor core and the metal sheath. On one hand, when alternating current flows through the three-phase conductor core, an alternating magnetic field is generated around the conductor. This alternating magnetic field links with the metal sheath, inducing a voltage on the metal sheath. If the metal sheath forms a closed loop with the ground (using either end-to-end grounding or cross-interconnected grounding), a grounding loop current will occur. Although in ideal conditions—where cross-interconnected grounding, perfectly symmetrical three-phase loads, and a triangular laying arrangement with equal lengths of the three cross-interconnected segments—the sum of the induced voltages is zero. However, in actual cable laying, perfect symmetry is difficult to achieve, inevitably leading to the existence of a grounding loop current, which is the induced current component of the sheath loop current. On the other hand, the three-layer structure of "core-insulation-metal sheath" can be equivalent to a cylindrical capacitor. The cable also contains longitudinal currents—leakage currents—flowing from the conductor core through the main insulation to the metal sheath and from the metal sheath through the outer sheath to the ground. Leakage current includes capacitive leakage current and resistive leakage current. Typically, capacitive leakage current is on the same order of magnitude (A-level) as the sheath induced current component, while resistive leakage current is only on the mA-level, much smaller than capacitive leakage current. Therefore, resistive leakage current can be ignored in calculations. The leakage current flows into the ground through the metal sheath; this grounding current is the leakage current component of the sheath circulating current. The metal sheath circulating current is the result of the combined effect of the induced current component and the capacitive leakage current component.

[0018] Based on the structure of a single-core cable, the double-π model can accurately represent the coupling relationship between the conductor and the metal sheath. Since the calculation of sheath circulating current falls under the category of steady-state calculation, this paper uses a double-π lumped parameter model to account for the influence of leakage current.

[0019] Figure 2 This is a double-π lumped-parameter model of a cable segment. Since resistive leakage current is negligible, the double-π model does not include conductance. In the figure, Rc and Lc are the total resistance and total inductance of the conductor, respectively; Rs and Ls are the total resistance and total inductance of the metal sheath, respectively; Ccs is the total capacitance between the conductor and the metal sheath; and Csg is the total capacitance of the metal sheath to ground. Because the sheath is grounded at both ends, the potential difference between the metal sheath and the ground is much smaller than the potential difference between the conductor and the metal sheath. Therefore, the capacitive leakage current flowing from the metal sheath through the outer sheath to the ground is very small and can be ignored in the calculation. Thus, an equivalent model of the three-phase cable cross-interconnection grounding system can be obtained. Each sheath loop consists of three π-type equivalent circuits. This equivalent model is the basis for analyzing and solving the sheath circulating current.

[0020] Figure 3 Middle,U A U B U C These are the three-phase core voltage phasors; I A I B I C These are the phasors of the three-phase conductor load current (voltage and current in the following text are phasors and will not be elaborated further); I sai I sbi I sci (i=1, 2, 3) represents the total circulating current through the i-th segment of each sheath loop; I cai I is the leakage current of the equivalent capacitance at both ends of the i-th segment of cable in phase A; Lai I represents the total current flowing through the i-th segment of the cable in phase A (including leakage current); g11 I g12 I g13 with I g21 I g22 I g23 These are the three-phase sheath circulating currents in the directly grounded boxes on the left and right sides, respectively; I c11 I c12 I c13 with I c21 I c22 I c23 These are the three-phase sheath circulating currents in the two cross-connect boxes; R d1 R d2 R is the grounding resistance at both ends of the sheath; cai L caiLet R be the concentrated resistance and inductance of the i-th segment of cable A, respectively; sai L sai Here, Ci represents the concentrated resistance and inductance of the metal sheath of the i-th segment of cable in phase A; Ci represents the concentrated capacitance between the conductor and the sheath of the i-th segment of cable in phase A; the other parameters for phases B and C have similar meanings to those for phase A. Among these, Ci, Cbi, and Cci can be calculated using the following formulas: ; ; Among them, I cai The phasor of the capacitive leakage current in the i-th segment of phase A cable is represented by j; j represents the imaginary unit; ω represents the angular frequency of the alternating current; C ai U represents the total capacitance between the i-th segment of cable core in phase A and the metal sheath; A ε represents the voltage phasor of phase A conductor; r ε0 represents the relative permittivity of the main insulation material of the cable; ε0 represents the vacuum permittivity; D c Indicates the diameter of the cable core; δ represents the thickness of the cable's main insulation; L i This represents the length of the i-th cable segment.

[0021] Similarly, the leakage currents of phases B and C can be obtained.

[0022] When the cable is disconnected at the end, the load current component of the conductor is equivalent to zero. At this time, the circulating current flowing through the cable's metallic sheath is entirely generated by the leakage current. The leakage current affects the sheath circulating current in two main ways: First, the leakage current between the conductor and the sheath forms a circulating current in each sheath segment through impedance shunting; second, the leakage current in the conductor also forms a circulating current in each sheath segment through electromagnetic induction. Both of these circulating currents induce voltages through the mutual inductance between the metallic sheaths, thus generating new circulating currents. The total circulating current in the metallic sheath is the sum of the above circulating currents. When the cable is operating normally, the current in the conductor includes both load current and leakage current. At this time, the circulating current in the metallic sheath is generated by the combined effect of the conductor load current and the various leakage currents.

[0023] Grounding current testing instruments are typically used for live-line testing. The testing equipment should meet the following requirements: it should be able to measure grounding wires with a diameter of not less than 50 mm, with a maximum current range of not less than 500 A; the equipment should be portable, easy to operate, have high measurement accuracy, an AC current measurement resolution of 0.2 A, and good repeatability of measurement results; it should have multiple AC current ranges. The testing cycle for grounding current testing of cable metallic sheaths is shown in Table 1. Table 1

[0024] Step 102: After converting the acquired current signal into digital sampled values, the composite current sampled values ​​with the ground current sampled values ​​in the same phase are subtracted point by point to cancel the circulating current component in the composite current signal, and the difference signal proportional to the operating current is extracted.

[0025] The consistent linearity of the dual Rogowski coils ensures that the circulating components have the same scaling factor at the digital sampling level.

[0026] Let the linear scaling factor of the dual CT be K (since the linearity is consistent, K is the same for both), after removing DC: ADC sampled value corresponding to the ground current signal: ; The ADC sampled value corresponding to the synthesized current signal: ; Subtract point by point: ; The subtraction completely cancels out the circulation. The corresponding ADC components differ only from the actual operating current. It exhibits a linear proportional relationship, thereby eliminating circulating current interference and extracting the ADC signal corresponding to the pure operating current.

[0027] Step 103: Take the absolute value of the difference signal and sum it, and convert the summed value into the actual operating current value through a preset segmented calibration curve.

[0028] The reason for using absolute value summation is that both the operating current and the circulating current are AC power frequency signals (sine waves). The sampled values ​​alternate between positive and negative. If the difference signals are summed directly, the positive and negative values ​​will cancel each other out, and the sum will approach 0, which cannot reflect the actual magnitude of the signal. After taking the absolute value, the AC signal is converted into a sequence of all positive values. The summed value can effectively characterize the "total energy" or "effective amplitude" of the signal.

[0029] The step of converting the summation value into the actual operating current value through a preset piecewise calibration curve includes: pre-establishing a mapping table between the known operating current and the summation value of the difference signal, and using piecewise linear interpolation to compensate for nonlinear errors throughout the entire range.

[0030] Compensating for hardware nonlinearity enables precise quantization. Since linearity is not absolutely ideal (a slight nonlinearity exists across the entire range), piecewise calibration, through pre-calibration (establishing a mapping table between known operating current and the sum of the difference signal), uses piecewise linear interpolation to accurately convert `sum_buff` into the true operating current value, compensating for the aforementioned nonlinearity error. This is a highly efficient way to improve accuracy.

[0031] Step 104: Perform Discrete Fourier Transform on the grounding current signal and the difference signal respectively, and express the two signals in complex number representation at power frequency. Then, calculate the phase difference between the grounding current signal and the difference signal by calculating the quotient of the complex number representation.

[0032] like Figure 4 As shown, the step of calculating the phase difference between the grounding current signal and the difference signal by calculating the quotient expressed in complex numbers includes: The phase difference is calculated using the complex quotient method, and the formula is as follows: ; in, , These are the real and imaginary parts of the complex representation of the grounding current signal, respectively. , These are the real and imaginary parts in the complex representation of the difference signal, respectively, and the phase difference is corrected to a range of 0-360°.

[0033] Step 105: Determine the system state of the high-voltage cable grounding system based on the operating current value and the phase difference.

[0034] In this embodiment, on the one hand, by utilizing dual Rogowski coils with consistent linearity and subtracting digital sample values ​​point by point, the circulating current component in the synthesized current signal is canceled out, thereby extracting the pure operating current and solving the problem that traditional methods cannot separate current components. On the other hand, the phase difference is calculated using discrete Fourier transform and the complex quotient method, avoiding the cumulative error caused by two calculations in traditional methods, thus improving the accuracy of phase analysis. Furthermore, not only is the state determination of the high-voltage cable grounding system based on the operating current value and phase difference achieved, but also the nonlinear error across the entire range is compensated through a preset piecewise calibration curve, ensuring the accuracy of the measurement results.

[0035] In one embodiment, determining the system state of the high-voltage cable grounding system based on the operating current value and the phase difference includes: calculating the ratio of the grounding current to the load current based on the operating current value, and calculating the phase difference between the three-phase currents based on the phase difference between the grounding current signal and the difference signal; comparing the ratio and the phase difference between the three-phase currents with a preset threshold to determine the system state judgment result; wherein, the system state includes: normal, caution, and abnormal.

[0036] Figure 5 For the specific sampling process, and specifically for the analysis of the cable metal sheath grounding current measurement data, it is necessary to combine the cable line load conditions and comprehensively analyze the development and changing trend of the metal sheath grounding current anomaly. The judgment criteria for the detection of metal sheath grounding current in high-voltage cable lines are shown in Table 2.

[0037] Table 2

[0038] In a field application of a 110kV high-voltage cable grounding system, this method calculated the ratio of phase A grounding current to load current to be 0.1, phase B to 0.2, and phase C to 0.3. Simultaneously, the phase difference between phases A and B was measured to be 120°, the phase difference between phases B and C was 120°, and the phase difference between phase C and A was 120°. After comparing these data with preset thresholds, the system automatically outputs a judgment result of "normal".

[0039] In one embodiment, the method further includes: uploading the operating current value, phase difference, and system status to a monitoring center to generate a historical trend analysis report and early warning information.

[0040] Figure 6 This is a schematic structural diagram of a device provided in an exemplary embodiment. Please refer to... Figure 6 At the hardware level, the device includes a processor 602, an internal bus 604, a network interface 606, memory 608, and non-volatile memory 610, and may also include other hardware required for its functions. One or more embodiments of the present invention can be implemented in software, for example, the processor 602 reads the corresponding computer program from the non-volatile memory 610 into memory 608 and then runs it. Of course, in addition to software implementation, one or more embodiments of the present invention do not exclude other implementation methods, such as logic devices or a combination of hardware and software, etc. That is to say, the execution subject of the following processing flow is not limited to each logic unit, but can also be hardware or logic devices.

[0041] Please refer to Figure 7 A vector synthesis and analysis device for induced current in a high-voltage cable grounding system can be applied to, for example... Figure 7 The device shown, in order to implement the technical solution of the present invention, includes: The acquisition unit 701 is used to synchronously acquire the grounding current signal of the three-phase metal sheath of the high-voltage cable and the composite current signal of each phase conductor through a double Rogowski coil with consistent linearity. The composite current signal is the superposition value of the operating current and the circulating current component. The reduction unit 702 is used to subtract the composite current sample value with the ground current sample value in the same phase from the sample value after converting the collected current signal into digital sample value, so as to cancel the circulating current component in the composite current signal and extract the difference signal proportional to the operating current. The conversion unit 703 is used to take the absolute value of the difference signal and sum it, and convert the summed value into the actual operating current value through a preset segmented calibration curve; Solver 704 is used to perform discrete Fourier transform on the grounding current signal and the difference signal respectively, to express the two signals in complex number representation at power frequency, and to obtain the phase difference between the grounding current signal and the difference signal by calculating the quotient of the complex number representation; The determining unit 705 is used to determine the system state of the high-voltage cable grounding system based on the operating current value and the phase difference.

[0042] Optionally, the consistent linearity of the dual Rogowski coils ensures that the circulating components have the same scaling factor at the digital sampling level.

[0043] Optionally, the conversion unit 703 is specifically used for: A mapping table between known operating current and the sum of difference signals is pre-established, and piecewise linear interpolation is used to compensate for nonlinear errors across the entire range.

[0044] Optionally, the solving unit 704 is specifically used for: The phase difference is calculated using the complex quotient method, and the formula is as follows: ; in, , These are the real and imaginary parts of the complex representation of the grounding current signal, respectively. , These are the real and imaginary parts in the complex representation of the difference signal, respectively, and the phase difference is corrected to a range of 0-360°. Optionally, determining the system state of the high-voltage cable grounding system based on the operating current value and the phase difference includes: The ratio of ground current to load current is calculated based on the operating current value, and the phase difference between the three-phase currents is calculated based on the phase difference between the ground current signal and the differential signal. The system state determination result is determined by comparing the ratio and the phase difference between the three-phase currents with a preset threshold; wherein the system state includes: normal, warning, and abnormal.

[0045] Optionally, the circulating current component includes an induced current component and a capacitive leakage current component, wherein the capacitive leakage current is calculated according to the following formula: ; ; Among them, I cai The phasor of the capacitive leakage current in the i-th segment of phase A cable is represented by j; j represents the imaginary unit; ω represents the angular frequency of the alternating current; C ai U represents the total capacitance between the i-th segment of cable core in phase A and the metal sheath; Aε represents the voltage phasor of phase A conductor; r ε0 represents the relative permittivity of the main insulation material of the cable; ε0 represents the vacuum permittivity; D c Indicates the diameter of the cable core; δ represents the thickness of the cable's main insulation; L i This represents the length of the i-th cable segment. Optionally, the device further includes: The uploading unit 706 is used to upload the operating current value, phase difference and system status to the monitoring center to generate historical trend analysis reports and early warning information.

[0046] The systems, devices, modules, or units described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer, which can take the form of a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email sending and receiving device, game console, tablet computer, wearable device, or any combination of these devices.

[0047] In a typical configuration, a computer includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0048] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0049] Computer-readable media, including both permanent and non-permanent, removable and non-removable media, can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, disk storage, quantum memory, graphene-based storage media or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0050] For any other form of computer-readable medium (or computer-readable storage medium) as described above, computer instructions may be stored thereon, which, when executed by a processor, implement one or more of the above embodiments, thereby realizing the technical solution of the present invention.

[0051] The present invention also proposes a computer program that, when executed by a processor, implements one or more of the embodiments described above, thereby realizing the technical solution of the present invention. This computer program may be specifically recorded on the above-described or other computer-readable media, and the present invention does not impose any limitations on this.

[0052] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0053] The foregoing has described specific embodiments of the invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims may be performed in a different order than that shown in the embodiments and still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0054] The terminology used in one or more embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” used in one or more embodiments of the invention and in the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0055] It should be understood that although the terms first, second, third, etc., may be used to describe various information in one or more embodiments of the present invention, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first information may also be referred to as second information without departing from the scope of one or more embodiments of the present invention, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0056] The above description is merely a preferred embodiment of one or more embodiments of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments of the present invention should be included within the protection scope of one or more embodiments of the present invention.

Claims

1. A method for vector synthesis and analysis of induced current in a high-voltage cable grounding system, characterized in that, include: The grounding current signal of the three-phase metal sheath of the high-voltage cable and the composite current signal of each phase conductor are synchronously acquired by dual Rogowski coils with consistent linearity. The composite current signal is the superposition value of the operating current and the circulating current component. After converting the acquired current signal into digital sampled values, the composite current sampled values ​​with the ground current sampled values ​​in the same phase are subtracted point by point to cancel the circulating current component in the composite current signal, and the difference signal proportional to the operating current is extracted. The absolute value of the difference signal is taken and summed, and the summation value is converted into the actual operating current value through a preset piecewise calibration curve; Discrete Fourier transforms are performed on the ground current signal and the difference signal respectively, and the two signals are represented by complex numbers at the power frequency. The phase difference between the ground current signal and the difference signal is obtained by calculating the quotient of the complex number representation. The system state of the high-voltage cable grounding system is determined based on the operating current value and the phase difference.

2. The method according to claim 1, characterized in that, The consistent linearity of the dual Rogowski coils ensures that the circulating components have the same scaling factor at the digital sampling level.

3. The method according to claim 1, characterized in that, The process of converting the summation value into the actual operating current value using a preset piecewise calibration curve includes: A mapping table between known operating current and the sum of difference signals is pre-established, and piecewise linear interpolation is used to compensate for nonlinear errors across the entire range.

4. The method according to claim 1, characterized in that, The step of calculating the phase difference between the grounding current signal and the difference signal by calculating the quotient in complex number representation includes: The phase difference is calculated using the complex quotient method, and the formula is as follows: ； in, , These are the real and imaginary parts of the complex representation of the grounding current signal, respectively. , These are the real and imaginary parts in the complex representation of the difference signal, respectively, and the phase difference is corrected to a range of 0-360°.

5. The method according to claim 1, characterized in that, Determining the system state of the high-voltage cable grounding system based on the operating current value and the phase difference includes: The ratio of ground current to load current is calculated based on the operating current value, and the phase difference between the three-phase currents is calculated based on the phase difference between the ground current signal and the differential signal. The system state determination result is determined by comparing the ratio and the phase difference between the three-phase currents with a preset threshold; wherein the system state includes: normal, warning, and abnormal.

6. The method according to claim 1, characterized in that, The circulating current component includes an induced current component and a capacitive leakage current component, wherein the capacitive leakage current is calculated according to the following formula: ； ； Among them, I cai The phasor represents the capacitive leakage current of the i-th segment of cable in phase A; j represents the imaginary unit; ω represents the angular frequency of the alternating current; C ai U represents the total capacitance between the i-th segment of cable core in phase A and the metal sheath; A ε represents the voltage phasor of phase A conductor; r ε0 represents the relative permittivity of the main insulation material of the cable; ε0 represents the vacuum permittivity; D c δ represents the diameter of the cable core; L represents the thickness of the cable's main insulation. i This represents the length of the i-th cable segment.

7. The method according to claim 1, characterized in that, The method further includes: The operating current value, phase difference, and system status are uploaded to the monitoring center to generate historical trend analysis reports and early warning information.

8. A vector synthesis and analysis device for induced current in a high-voltage cable grounding system, characterized in that, The device includes: Acquisition Unit: The grounding current signal of the three-phase metal sheath of the high-voltage cable and the composite current signal of each phase conductor are synchronously acquired by two Rogowski coils with consistent linearity. The composite current signal is the superposition value of the operating current and the circulating current component. Elimination unit: After converting the acquired current signal into digital sampled values, the composite current sampled value with the ground current sampled value in the same phase is subtracted point by point to cancel the circulating current component in the composite current signal, and the difference signal proportional to the operating current is extracted. Conversion unit: Takes the absolute value of the difference signal and sums it, and converts the summation value into the actual operating current value through a preset segmented calibration curve; Solving unit: Performs discrete Fourier transform on the grounding current signal and the difference signal respectively, expresses the two signals in complex number representation at power frequency, and obtains the phase difference between the grounding current signal and the difference signal by calculating the quotient of the complex number representation; Determination Unit: Determines the system state of the high-voltage cable grounding system based on the operating current value and the phase difference.

9. An electronic device, characterized in that, include: processor; Memory used to store processor-executable instructions; The processor implements the steps of the method as described in any one of claims 1-7 by running the executable instructions.

10. A computer-readable storage medium storing computer instructions thereon, characterized in that, When executed by the processor, this instruction implements the steps of the method as described in any one of claims 1-7.

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