Grounding impedance correction method and device, nonvolatile storage medium and electronic equipment

Abstract

The invention discloses a grounding impedance correction method and device, a nonvolatile storage medium and electronic equipment. The method comprises the steps that a cable line is detected, initial grounding impedance is obtained, and conduction modes of short-circuit current in the cable line comprise a first conduction mode of conducting through a grounding point of the cable line and a second conduction mode of flowing back to a neutral point of a transformer through a metal sheath layer of the cable line; grounding currents corresponding to a plurality of preset grounding points of the first conduction mode are determined, and the plurality of preset grounding points are grounding points with different short-circuit current distribution on the cable line; determining a shunting coefficient based on the grounding currents corresponding to the plurality of predetermined grounding points; and correcting the initial grounding impedance according to the shunting coefficient to obtain target grounding impedance. The technical problem that the accuracy of the grounding impedance measurement value is not ideal in the prior art is solved.

Description

Technical Field

[0001] The present application relates to the field of power systems, and in particular to a ground impedance correction method, device, non-volatile storage medium and electronic device. Background Art

[0002] The determination of cable grounding impedance is an important means to detect the operation status of the cable and evaluate the working status of the grounding point. Ensuring the measurement and calculation accuracy of cable grounding impedance is to ensure the stable operation of the power system. When a short circuit occurs, a large short-circuit current often flows into the ground grid. Different short-circuit faults will produce different short-circuit currents entering the ground, and different short-circuit currents entering the ground will cause different degrees of ground potential rise, step voltage, and contact voltage. Therefore, the short-circuit current shunt analysis under line short-circuit faults and the calculation of the maximum short-circuit current entering the ground are the basis for the evaluation of the grounding network status. At the same time, when injecting heterofrequency current into the tunnel for on-site testing of the grounding impedance, part of the current is shunted through the cable sheath to the substations at both ends of the tunnel, and there are two current derivation paths. The relevant technology lacks consideration of the shunting of the short-circuit current entering the ground in the tunnel when a short circuit occurs in the cable line, resulting in unsatisfactory accuracy in the grounding impedance measurement.

[0003] To address the above-mentioned problems, no effective solution has been proposed yet. Summary of the invention

[0004] The embodiments of the present application provide a ground impedance correction method, device, non-volatile storage medium and electronic device to at least solve the technical problem of unsatisfactory accuracy of ground impedance measurement values ​​existing in the related art.

[0005] According to one aspect of an embodiment of the present application, a grounding impedance correction method is provided, comprising: detecting a cable line to obtain an initial grounding impedance, wherein the conduction mode of the short-circuit current in the cable line includes a first conduction mode of conduction through a grounding point of the cable line, and a second conduction mode of returning to a neutral point of a transformer through a metal sheath layer of the cable line; determining the ground currents corresponding to a plurality of predetermined grounding points of the first conduction mode, wherein the plurality of predetermined grounding points are grounding points with different short-circuit current distributions on the cable line; determining a shunt coefficient based on the ground currents corresponding to the plurality of predetermined grounding points, wherein the shunt coefficient represents the proportion of the short-circuit current conducted by the first conduction mode to the total short-circuit current, and the total short-circuit current is obtained based on the short-circuit current conducted by the first conduction mode and the short-circuit current conducted by the second conduction mode; and correcting the initial grounding impedance according to the shunt coefficient to obtain a target grounding impedance.

[0006] Optionally, the shunt coefficient is determined based on the ground currents corresponding to multiple predetermined grounding points, including: determining the total short-circuit current according to a predetermined short-circuit type based on a reference voltage and a reference current of the transformer; and determining the shunt coefficient based on the ground currents corresponding to multiple predetermined grounding points, and the total short-circuit current.

[0007] Optionally, the shunt coefficient is determined based on the ground currents corresponding to multiple predetermined grounding points and the total short-circuit current, including: adding the ground currents corresponding to multiple predetermined grounding points to determine the added short-circuit current of the first conduction mode; and determining the shunt coefficient based on the ratio between the added short-circuit current and the total short-circuit current.

[0008] Optionally, based on a reference voltage and a reference current of the transformer, a total short-circuit current is determined according to a predetermined short-circuit type, including: determining an additional impedance and a predetermined coefficient according to the predetermined short-circuit type, wherein the predetermined coefficient is determined based on the number of faulty phases in the three-phase electricity of the predetermined short-circuit type, and the additional impedance is used to characterize the influence of the flow paths of different sequence currents in the transformer on the short-circuit current; the total short-circuit current is determined based on the reference voltage, the reference current, the additional impedance, and the predetermined coefficient.

[0009] Optionally, determining the ground currents corresponding to multiple predetermined grounding points of the first conduction mode, includes: using a predetermined power simulation model to control line opening and closing, and generating a fault state corresponding to a predetermined short circuit type, wherein the power simulation model is determined based on cable line parameters, transformer parameters, and system power supply parameters; in the fault state, determining the ground currents corresponding to multiple predetermined grounding points.

[0010] Optionally, the method also includes: in the case where there are multiple predetermined short-circuit types, summing up the ground currents corresponding to the multiple predetermined grounding points according to the fault states corresponding to the multiple predetermined short-circuit types, and determining the summed short-circuit currents corresponding to the multiple predetermined short-circuit types; determining the sub-coefficients corresponding to the multiple predetermined short-circuit types based on the summed short-circuit currents and the total short-circuit current corresponding to the multiple predetermined short-circuit types; and determining the shunt coefficient based on the sub-coefficients corresponding to the multiple predetermined short-circuit types using an average value processing method.

[0011] Optionally, the plurality of predetermined grounding points include an equivalent power supply terminal grounding point and a transformer terminal grounding point.

[0012] According to another aspect of an embodiment of the present application, a grounding impedance correction device is provided, including: an initial grounding impedance determination module, used to detect a cable line to obtain an initial grounding impedance, wherein the conduction mode of the short-circuit current in the cable line includes a first conduction mode of conduction through a grounding point of the cable line, and a second conduction mode of returning to the neutral point of the transformer through a metal sheath layer of the cable line; a ground current determination module, used to determine the ground currents corresponding to a plurality of predetermined grounding points of the first conduction mode, wherein the plurality of predetermined grounding points are grounding points with different short-circuit current distributions on the cable line; a shunt coefficient determination module, used to determine a shunt coefficient based on the ground currents corresponding to the plurality of predetermined grounding points, wherein the shunt coefficient represents the proportion of the short-circuit current conducted by the first conduction mode to the total short-circuit current, and the total short-circuit current is obtained based on the short-circuit current conducted by the first conduction mode and the short-circuit current conducted by the second conduction mode; a target grounding impedance determination module, used to correct the initial grounding impedance according to the shunt coefficient to obtain a target grounding impedance.

[0013] According to another aspect of an embodiment of the present application, a non-volatile storage medium is provided, wherein the non-volatile storage medium stores a plurality of instructions, and the instructions are suitable for being loaded by a processor and executing any one of the ground impedance correction methods.

[0014] According to another aspect of an embodiment of the present application, an electronic device is provided, comprising: one or more processors and a memory, the memory being used to store one or more programs, wherein when the one or more programs are executed by one or more processors, the one or more processors implement any one of the ground impedance correction methods.

[0015] In an embodiment of the present application, an initial grounding impedance is obtained by detecting a cable line, wherein the conduction mode of the short-circuit current in the cable line includes a first conduction mode of conduction through the grounding point of the cable line, and a second conduction mode of returning to the neutral point of the transformer through the metal sheath layer of the cable line; the grounding current corresponding to multiple predetermined grounding points of the first conduction mode is determined, wherein the multiple predetermined grounding points are grounding points with different short-circuit current distributions on the cable line; based on the grounding current corresponding to the multiple predetermined grounding points, a shunt coefficient is determined, wherein the shunt coefficient represents the proportion of the short-circuit current conducted by the first conduction mode to the total short-circuit current, and the total short-circuit current is obtained based on the short-circuit current conducted by the first conduction mode and the short-circuit current conducted by the second conduction mode; according to the shunt coefficient, the initial grounding impedance is corrected to obtain the target grounding impedance. The purpose of correcting the initial grounding impedance by using the shunt coefficient is achieved, and the technical effect of improving the accuracy of the cable grounding impedance measurement value is achieved, thereby solving the technical problem of unsatisfactory accuracy of the grounding impedance measurement value existing in the related art. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0017] Figure 1 is a flow chart of an optional ground impedance correction method provided according to an embodiment of the present application;

[0018] Figure 2 It is a schematic diagram of short-circuit current shunting according to an optional ground impedance correction method provided in an embodiment of the present application;

[0019] Figure 3 is a schematic cross-sectional view of a three-phase cross-connected cable according to an optional ground impedance correction method provided in an embodiment of the present application;

[0020] Figure 4 It is a schematic diagram of a cable outlet short-circuit model according to an optional ground impedance correction method provided in an embodiment of the present application;

[0021] Figure 5 It is a schematic diagram of grounding points of a cable line according to an optional ground impedance correction method provided in an embodiment of the present application.

[0022] Figure 6 It is a schematic diagram of short-circuit current shunting results of an optional ground impedance correction method provided in an embodiment of the present application;

[0023] Figure 7 It is a schematic diagram of an optional ground impedance correction device provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution 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 part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0025] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0026] For the convenience of description, some nouns or terms involved in the embodiments of the present application are explained below:

[0027] The contact voltage is the potential difference between the human body touching the equipment casing or structure and the standing point when a ground fault occurs in the electrical equipment. The magnitude of the contact voltage depends on the current flowing into the ground grid, the resistance of the ground grid, and the contact resistance between the human body and the grounded equipment. The measurement and evaluation of the contact voltage is of great significance in the safe operation of the power system and is an important part of the electrical safety assessment and grounding system design.

[0028] Step voltage refers to the potential difference between two points on the ground when current flows through the earth. It is used to assess the safety of personnel around power facilities when fault current flows through them. When designing and operating power systems, the level of step voltage must be strictly controlled to prevent personnel from being injured by electric shock due to step voltage.

[0029] The current split coefficient refers to the ratio of the current flowing into a specific path to the total current under a specific short circuit fault or ground fault condition. It is usually used for testing and correcting ground impedance, safety assessment and optimization design of power systems, and power system fault analysis.

[0030] Single-phase ground short circuit refers to an abnormal electrical connection between a phase conductor and the earth in a power system. Single-phase ground short circuit may generate overcurrent and overvoltage, leading to increased ground potential, electromagnetic interference, and relay potential protection, threatening the safety and stability of the power system.

[0031] Two-phase ground short circuit refers to a short circuit fault between any two-phase conductors and the earth in the power system. In a two-phase ground short circuit, since the fault point is connected to the earth, the fault current will not only flow between the two-phase conductors, but also flow through the earth back to the neutral point or grounding system of the power system, causing current surge, voltage imbalance, power supply interruption and relay protection action, affecting the operation status and safety of the entire power system.

[0032] According to an embodiment of the present application, a method embodiment for correcting ground impedance is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0033] Figure 1 is a flow chart of an optional ground impedance correction method provided according to an embodiment of the present application, such as Figure 1 As shown, the method comprises the following steps:

[0034] Step S102, detecting the cable line to obtain an initial grounding impedance, wherein the conduction mode of the short-circuit current in the cable line includes a first conduction mode of conducting through a grounding point of the cable line and a second conduction mode of returning to a neutral point of a transformer through a metal sheath layer of the cable line;

[0035] It can be understood that when a short circuit occurs in a cable line, the short circuit current can be conducted in two ways. The first conduction mode is that the short circuit current flows through the metal sheath loop of the cable line and enters the ground from the grounding grid connected to the cable sheath; the second conduction mode is that the short circuit current flows back to the neutral point of the transformer through the metal sheath layer of the cable line. When a short circuit occurs in a cable line, a large short circuit current will enter the grounding grid through the first conduction mode. In order to avoid the harm of excessive ground current to the power system, the cable line needs to be tested to obtain the initial grounding impedance, which is used for safety assessment and fault detection of the line to ensure the safe and stable operation of the power system.

[0036] Optionally, when the power system is operating normally, the current entering the earth through the neutral point of the transformer is very small, but when a short circuit fault occurs in the power system, the voltage at the fault point drops sharply, causing the potential difference between the fault point and the earth to increase, so that a large amount of current flows into the earth through the grounding grid. The total short-circuit current will not all flow into a certain grounding point, but will be diverted within the system and transmitted to the ground from different grounding points. For cable lines, when a short circuit occurs, due to the cable's herringbone arrangement and cross-interconnection design, the cable's metal sheath will form a closed loop, allowing part of the short-circuit current to flow back along this path instead of directly into the ground. Therefore, part of the short-circuit current will flow back to the neutral point of the transformer through the metal sheath layer of the cable line; at the same time, since the cable's metal sheath is directly connected to the grounding grid, forming a low-impedance path, when a short circuit occurs, most of the current will flow through the metal sheath loop and enter the ground from the grounding grid connected to the cable sheath. This path into the ground will have a greater impact on the ground potential rise, step voltage and contact voltage near the connection point. The grounding impedance can be measured to conduct a safety assessment of the grounding system, and corresponding maintenance and optimization can be carried out to improve the reliability of the power system.

[0037] Step S104, determining the ground currents respectively corresponding to a plurality of predetermined grounding points of the first conduction mode, wherein the plurality of predetermined grounding points are grounding points with different short-circuit current distributions on the cable line;

[0038] It can be understood that when a short circuit occurs in a cable line, a large short circuit current will flow through the metal sheath loop of the cable line and enter the ground from the grounding grid connected to the cable sheath, and the magnitude of the short circuit current entering the ground from each predetermined grounding point is determined. The magnitude of the short circuit current entering the ground from each predetermined grounding point can be used to obtain the current shunt coefficient of the first conduction mode current, which is of great significance for correcting the grounding impedance and evaluating the safety of the grounding system.

[0039] In an optional embodiment, determining the ground currents corresponding to multiple predetermined grounding points of the first conduction mode includes: using a predetermined power simulation model to control line opening and closing, generating a fault state corresponding to a predetermined short circuit type, wherein the power simulation model is determined based on cable line parameters, transformer parameters, and system power supply parameters; in the fault state, determining the ground currents corresponding to multiple predetermined grounding points.

[0040] It can be understood that based on the cable line parameters, transformer parameters, and system power supply parameters, a power system short-circuit model, i.e., a power simulation model, is constructed. The ATP (Alternative Transient Program) simulation software can be used to construct a power system short-circuit model based on ATP, which can be used to simulate the electrical characteristics of a power system when a short-circuit fault occurs. By setting an appropriate switch closing time to simulate the fault state corresponding to a predetermined short-circuit type on the cable line, and using the model to obtain the ground current corresponding to multiple predetermined grounding points under the fault state corresponding to the predetermined short-circuit type. The ATP power system short-circuit model can simulate various short-circuit type faults, and can simulate the current changes during short-circuit faults, and then obtain the ground current under different fault states as data support to improve the accuracy of the calculation of the shunt coefficient.

[0041] Optionally, the parameters that need to be determined for constructing the ATP power system short-circuit model are system power supply parameters, transformer parameters and cable line parameters. The above-mentioned system power supply parameters include rated voltage and frequency, positive sequence, negative sequence and zero sequence impedance and system equivalent internal impedance and reactance. The above-mentioned transformer parameters include rated capacity, rated voltage, connection mode of high voltage side, medium voltage side and low voltage side, no-load current, no-load loss, load loss and short-circuit impedance percentage. The above-mentioned cable line parameters include line length, cable model, cross-sectional size, resistivity and capacitance of cable core, resistivity and inductance of sheath, grounding method and grounding resistance value. The ATP power system short-circuit model constructed based on the above parameters can accurately reflect the behavior of the system under short-circuit fault conditions and improve the accuracy of simulation results.

[0042] Optionally, the fault states corresponding to the above-mentioned predetermined short-circuit types may be multiple, for example, a single-phase ground short circuit in the middle of the line, a two-phase ground short circuit in the middle of the line, a single-phase ground short circuit near the system power supply end of the line, and a two-phase ground short circuit near the system power supply end of the line. A single-phase ground short circuit in the middle of the line refers to a short circuit between one of the three-phase conductors of the three-phase electricity and the earth in the middle of the cable line. This fault may cause problems such as overcurrent and overvoltage in the system, increased ground potential near the grounding point, relay protection action, and electromagnetic compatibility. A two-phase ground short circuit in the middle of the line refers to a short circuit between the two-phase conductors in the middle of the cable line and the earth at the same time. This fault may cause problems such as huge short-circuit current, voltage sag near the fault point, and relay protection action. A single-phase ground short circuit near the system power supply end of the line refers to a short circuit at one end of the cable line near the system power supply. This fault may cause problems such as huge short-circuit current, voltage sag, relay protection action, and huge thermal and mechanical effects at the fault point. Two-phase ground short circuit near the system power supply refers to the short circuit between the two-phase conductors of the cable line and the ground at the same time near the system power supply. This fault will cause arc fault, grounding system overload and voltage distortion at the fault point. According to different short circuit types, the corresponding shunt correction coefficient is obtained. Based on the above shunt coefficient, the ground impedance of the corresponding short circuit type is corrected to improve the accuracy and reliability of the ground impedance.

[0043] In an optional embodiment, the method also includes: in the case where there are multiple predetermined short-circuit types, summing up the ground currents corresponding to the multiple predetermined grounding points according to the fault states corresponding to the multiple predetermined short-circuit types, and determining the summed short-circuit currents corresponding to the multiple predetermined short-circuit types; determining the shunt coefficients corresponding to the multiple predetermined short-circuit types based on the summed short-circuit currents and the total short-circuit current corresponding to the multiple predetermined short-circuit types; and determining the shunt coefficient based on the shunt coefficients corresponding to the multiple predetermined short-circuit types using an average value processing method.

[0044] It can be understood that the ATP power system short-circuit model is used to construct the fault states corresponding to the predetermined short-circuit types, and the ground currents corresponding to the multiple predetermined grounding points of each fault state are obtained. The ground currents corresponding to the above-mentioned multiple predetermined grounding points are summed up to obtain the total current of the short-circuit current shunted through the first conduction mode under the fault states corresponding to the predetermined short-circuit types. Based on the total current shunted through the first conduction mode and the total short-circuit current, the shunt coefficients under the fault states corresponding to the multiple predetermined short-circuit types are obtained. The shunt coefficients under the fault states corresponding to the above-mentioned multiple predetermined short-circuit types are averaged to obtain the shunt coefficient. The ATP power system short-circuit model can be used to simulate a variety of short-circuit types and fault states. By calculating the shunt coefficients under the fault states corresponding to the multiple short-circuit types and taking the average value, a comprehensive shunt correction coefficient suitable for cable tunnel grounding impedance testing can be obtained, which improves the test accuracy and reliability.

[0045] In an optional embodiment, the plurality of predetermined grounding points include an equivalent power supply terminal grounding point and a transformer terminal grounding point.

[0046] It can be understood that the predetermined grounding points are selected near the system equivalent power supply end, the grounding point in the middle of the cable line and the grounding point near the transformer end. By analyzing the low current entering the above three grounding points, the distribution relationship of the short-circuit current between the cable sheath and the earth can be obtained, which is beneficial to maintaining the safety and stability of the grounding network system.

[0047] Optionally, the grounding method for the cable metal sheath may include direct grounding and isolated grounding. The above-mentioned direct grounding refers to direct grounding at both ends of the cable. This grounding method can provide a discharge path for the fault current and form an electrical connection between the metal sheath of the cable and the earth to reduce the induced voltage on the sheath and reduce electromagnetic interference to nearby communication lines. Isolation grounding means that the metal sheath is completely disconnected and not directly connected to the ground grid to reduce sheath circulation and electromagnetic interference. By reasonably designing the cable sheath grounding method, the operating reliability and safety of the cable line can be effectively improved.

[0048] Step S106, determining a shunt coefficient based on the ground currents corresponding to the plurality of predetermined grounding points, wherein the shunt coefficient represents a ratio of the short-circuit current conducted by the first conduction mode to the total short-circuit current, and the total short-circuit current is obtained based on the short-circuit current conducted by the first conduction mode and the short-circuit current conducted by the second conduction mode;

[0049] It can be understood that the ground currents corresponding to multiple predetermined grounding points are obtained through the power simulation model of ATP and summed up to obtain the total current of the short-circuit current shunted by the first conduction mode. Based on the short-circuit current conducted by the first conduction mode and the short-circuit current conducted by the second conduction mode, the total short-circuit current is obtained. According to the total current shunted by the first conduction mode and the total short-circuit current, the shunt coefficient is obtained. By calculating the ground currents of multiple grounding points and summing them up to obtain the shunt coefficient, the shunting situation of the short-circuit current can be reflected more accurately and comprehensively, and the accuracy of fault analysis and system testing can be improved.

[0050] In an optional embodiment, the shunt coefficient is determined based on the ground currents corresponding to multiple predetermined grounding points, including: determining the total short-circuit current according to a predetermined short-circuit type based on a reference voltage and a reference current of the transformer; determining the shunt coefficient based on the ground currents corresponding to multiple predetermined grounding points, and the total short-circuit current.

[0051] It can be understood that the reference voltage and reference current of the transformer are determined, and the pre-coefficient and additional impedance are determined according to the short-circuit type. Based on the above reference voltage, reference current, pre-coefficient and additional impedance, the total short-circuit current is obtained. The shunt coefficient is obtained based on the total short-circuit current and the sum of the ground currents corresponding to multiple predetermined grounding points. The actual voltage and current can be converted into per-unit values ​​through the reference voltage and reference current, which not only simplifies the calculation process, but also enables power systems of different sizes to be compared.

[0052] Optionally, the total short-circuit current can be obtained by the general calculation formula of the short-circuit fault current of the power system. The total short-circuit current I of the kth type fk The formula is:

[0053]

[0054] Among them, k is determined according to the short-circuit type of the circuit and the number of fault phases, U B Represents the reference voltage, S B Indicates the base capacity, m k represents the predetermined coefficient, X Δk Indicates additional impedance, m k and X Δk The values ​​of X are shown in Table 1. f0 Represents zero-sequence impedance, X f1 Represents the positive sequence impedance, X f2Represents negative sequence impedance. The above positive sequence impedance refers to the complex value of the ratio of the positive sequence voltage to the positive sequence current on each phase when the three-phase circuit system is unbalanced, which represents the impedance characteristics of the circuit to the positive sequence signal; negative sequence impedance refers to the complex value of the ratio of the negative sequence voltage to the negative sequence current on each phase when the three-phase circuit system is unbalanced, which represents the impedance characteristics of the circuit to the negative sequence signal; zero sequence impedance refers to the complex value of the ratio of the zero sequence voltage to the zero sequence current on each phase when the three-phase circuit system is unbalanced, which represents the impedance characteristics of the circuit to the zero sequence signal.

[0055] Table 1 m under different short circuit conditions k , X Δk Value

[0056]

[0057] In an optional embodiment, the shunt coefficient is determined based on the ground currents corresponding to multiple predetermined grounding points and the total short-circuit current, including: adding the ground currents corresponding to the multiple predetermined grounding points to determine the summed short-circuit current of the first conduction mode; and determining the shunt coefficient based on the ratio between the summed short-circuit current and the total short-circuit current.

[0058] It can be understood that the ground currents corresponding to multiple predetermined grounding points are summed to obtain the total current conducted by the short-circuit current through the first conduction mode, that is, the summed short-circuit current. The total short-circuit current is calculated using the power system short-circuit fault current calculation formula. Based on the ratio between the total current conducted through the first conduction mode and the total short-circuit current, the shunt coefficient is obtained. Calculating the shunt coefficient by summing up the ground currents of multiple grounding points can not only provide more accurate current distribution information, but also simplify the ground impedance test process and improve test efficiency.

[0059] Optionally, when a short circuit occurs on the cable line, the total short circuit current can be obtained by the total current conducted by the first conduction mode and the total current conducted by the second conduction mode. The total short circuit current I max The formula is:

[0060] I max =I g +I b (2)

[0061] Among them, I g is the total current entering the ground through each grounding point of the cable, that is, the total current conducted through the first conduction mode, I b It is the current flowing back to the neutral point of the transformer through the outer sheath of the cable, that is, the total current conducted by the second conduction mode.

[0062] Based on the total short-circuit current and the total current conducted by the first conduction mode, the shunt coefficient c can be obtained. sThe formula is:

[0063]

[0064] in, represents the instantaneous value of the summed short-circuit current conducted by the first conduction mode, Indicates the instantaneous value of the total short-circuit current.

[0065] Optionally, the total short-circuit current can be obtained by a general calculation formula for short-circuit fault current of a power system, can be obtained by summing the total current conducted by the first conduction mode and the total current conducted by the second conduction mode, or can be obtained by an ATP power simulation model.

[0066] In an optional embodiment, based on a reference voltage and a reference current of the transformer, a total short-circuit current is determined according to a predetermined short-circuit type, including: determining an additional impedance and a predetermined coefficient according to the predetermined short-circuit type, wherein the predetermined coefficient is determined based on the number of faulty phases in the three-phase electricity of the predetermined short-circuit type, and the additional impedance is used to characterize the influence of the flow paths of different sequence currents in the transformer on the short-circuit current; the total short-circuit current is determined based on the reference voltage, the reference current, the additional impedance, and the predetermined coefficient.

[0067] It can be understood that the additional impedance and the predetermined coefficient are determined according to the short-circuit type of the circuit. Among them, the predetermined coefficient is determined based on the number of faulty phases in the three-phase electricity of the predetermined short-circuit type, and is used to adjust the calculated amount of the short-circuit current to make it conform to a specific type of short-circuit fault. The additional impedance is used to characterize the influence of the flow paths of different sequence currents in the transformer on the short-circuit current. The total short-circuit current is obtained based on the above-mentioned additional impedance, predetermined coefficient, reference voltage and reference current. By reasonably determining the additional impedance and the predetermined coefficient, the accuracy and efficiency of the short-circuit current calculation can be improved, providing important technical support for the safe operation of the power system.

[0068] Optionally, by selecting additional impedance, predetermined coefficient, reference voltage and reference current based on the circuit short-circuit type, the circuit fault type can be accurately matched, the calculation process can be simplified, the system analysis capability can be improved, the accuracy and reliability of the calculation results can be ensured, and a basis for system design and fault handling can be provided. Moreover, by considering the flow of currents of different sequences, the accuracy of short-circuit current calculation is further improved. At the same time, by adjusting the reference voltage and reference current, it can adapt to power systems of different voltage levels, and enhance the versatility and applicability of the calculation method. By reasonably determining the additional impedance, predetermined coefficient, reference voltage and reference current, the accuracy and efficiency of short-circuit current calculation can be improved, providing important technical support for the safe operation of the power system.

[0069] Step S108: correcting the initial ground impedance according to the shunt coefficient to obtain a target ground impedance.

[0070] It can be understood that based on the shunt coefficient, the initial ground impedance of the test is corrected to obtain the corrected target ground impedance. Correcting the ground impedance by the shunt coefficient can effectively improve the accuracy of the ground impedance, which is beneficial to the subsequent safety assessment, inspection and maintenance of the power system, and is the key to the safe and stable operation of the power system.

[0071] Optionally, in the field test of cable grounding impedance, due to the presence of the cable sheath, part of the test current will be shunted to the grounding grid through the cable sheath, resulting in a deviation between the initial grounding impedance value obtained by the test and the actual value. In order to more accurately reflect the actual performance of the grounding system, it is necessary to correct the initial grounding impedance result according to the shunt coefficient. The shunt coefficient is obtained based on the proportion of the short-circuit current conducted by the first conduction mode to the total short-circuit current. The initial short-circuit current conducted by the uncorrected first conduction mode is tested, and the above initial short-circuit current is corrected based on the shunt coefficient to obtain the corrected target short-circuit current conducted by the first conduction mode. Based on the target short-circuit current, Ohm's law is used to obtain the corrected target grounding impedance. Using the shunt coefficient and Ohm's law to correct the grounding impedance approximation improves the accuracy of the grounding impedance and simplifies the test process. At the same time, it is applicable to various short-circuit types, providing reliable data support for the design and optimization of the grounding system.

[0072] Through the above step S102, the cable line is detected to obtain the initial grounding impedance, wherein the conduction mode of the short-circuit current in the cable line includes a first conduction mode of conduction through the grounding point of the cable line and a second conduction mode of returning to the neutral point of the transformer through the metal sheath layer of the cable line; step S104, determining the grounding current corresponding to multiple predetermined grounding points of the first conduction mode, wherein the multiple predetermined grounding points are grounding points with different short-circuit current distributions on the cable line; step S106, based on the grounding current corresponding to multiple predetermined grounding points, determining the shunt coefficient, wherein the shunt coefficient represents the proportion of the short-circuit current conducted by the first conduction mode to the total short-circuit current, and the total short-circuit current is obtained based on the short-circuit current conducted by the first conduction mode and the short-circuit current conducted by the second conduction mode; step S108, correcting the initial grounding impedance according to the shunt coefficient to obtain the target grounding impedance. The purpose of correcting the initial grounding impedance by using the shunt coefficient can be achieved, and the technical effect of improving the accuracy of the cable grounding impedance measurement value is achieved, thereby solving the technical problem of unsatisfactory accuracy of the grounding impedance measurement value existing in the related art.

[0073] Based on the above embodiments and optional embodiments, the present application proposes an optional implementation method for correcting the ground impedance measurement value. In the implementation of the present application, the initial ground impedance obtained by actual measurement is corrected by using the shunt coefficient obtained by the power system short-circuit model, thereby obtaining the corrected target ground impedance.

[0074] Power system short-circuit faults can be divided into symmetrical short circuits and asymmetrical short circuits, among which single-phase ground short circuit faults occur most frequently. For short-circuit faults in a circuit, a large short-circuit current will be generated in the circuit, causing damage to the electrical equipment and stable operation of the power system. In order to better analyze and evaluate the safety of short-circuit faults, it is necessary to quantify the short-circuit current generated by the short-circuit fault. The total short-circuit current I of the kth type of transformation can be obtained through the general calculation formula of the short-circuit fault current of the power system. fk The formula is:

[0075]

[0076] Among them, U B Represents the reference voltage, S B Indicates the base capacity, m k represents the predetermined coefficient, X Δk Represents additional impedance, m k and X Δk The values ​​of are shown in Table 1.

[0077] For formula (1), first determine the reference voltage and reference current of the transformer, and determine the pre-coefficient and additional impedance according to the short-circuit type. Based on the above reference voltage, reference current, pre-coefficient and additional impedance, the total short-circuit current is obtained. The shunt coefficient is obtained based on the total short-circuit current and the sum of the ground currents corresponding to multiple predetermined grounding points. The actual voltage and current can be converted into per-unit values ​​through the reference voltage and reference current, which not only simplifies the calculation process, but also enables power systems of different sizes to be compared.

[0078] The total short-circuit current will not all flow into a certain grounding point, but will be diverted within the system and transmitted to the ground from different grounding points. For cable lines, when a short-circuit fault occurs, due to the cable's triangular arrangement and cross-interconnection design, the cable's metal sheath will form a closed loop, allowing part of the short-circuit current to flow back along this path instead of directly into the ground. Therefore, part of the short-circuit current will flow back to the neutral point of the transformer through the metal sheath layer of the cable line; at the same time, since the cable's metal sheath is directly connected to the grounding grid, forming a low-impedance path, when a short-circuit fault occurs, most of the current will flow through the metal sheath loop and enter the ground from the grounding grid connected to the cable sheath. This path into the ground will have a greater impact on the ground potential rise, step voltage and contact voltage near the connection point. The grounding system can be safely evaluated by measuring the grounding impedance, and corresponding maintenance and optimization can be carried out to improve the reliability of the power system.

[0079] Figure 2is a schematic diagram of short-circuit current shunting according to an optional ground impedance correction method provided in an embodiment of the present application. The short-circuit fault occurs on a cable line, wherein R is the ground impedance of the cable outer sheath, R z is the grounding impedance of the substation grid, I g1 to I g4 are the ground currents at different grounding points, I g is the total current entering the ground through each grounding point of the cable (i.e., the sum of the short-circuit current), I b is the current flowing back to the neutral point of the transformer through the cable sheath, I d The current provided by the substation to flow from the substation ground grid back to the neutral point of the transformer, I z It is the sum of the current flowing back to the neutral point of the transformer through the outer sheath of the cable and the current provided by the substation and flowing back to the neutral point of the transformer through the substation ground grid. max represents the total short-circuit current, AC represents the alternating current power supply, and the dashed box represents the cross-connected cables. Figure 2 It can be seen from the figure that when a short circuit occurs in a cable line, the short circuit current can be conducted in two ways. The first conduction mode is that the short circuit current flows through the metal sheath loop of the cable line and enters the ground from the grounding grid connected to the cable sheath; the second conduction mode is that the short circuit current flows back to the neutral point of the transformer through the metal sheath layer of the cable line. The total short circuit current can be obtained by the total current conducted by the first conduction mode (i.e., the sum of the short circuit currents) and the total current conducted by the second conduction mode. The total short circuit current I max The formula is:

[0080] I max =I g +I b (2)

[0081] Among them, I g is the total current entering the ground through each grounding point of the cable, that is, the total current conducted through the first conduction mode, I b It is the current flowing back to the neutral point of the transformer through the outer sheath of the cable, that is, the total current conducted by the second conduction mode.

[0082] When a short circuit occurs in a cable line, a large short-circuit current will enter the grounding grid through the first conduction mode. In order to avoid the damage of excessive ground current to the power system, it is necessary to determine the current shunt coefficient and correct the initial grounding impedance based on the shunt coefficient to obtain the corrected target grounding impedance for line safety assessment and fault detection to ensure the safe and stable operation of the power system.

[0083] The current split coefficient is the ratio between the total current conducted by the first conduction mode and the total short-circuit current. The total current conducted by the first conduction mode can be determined by constructing the ATP power system short-circuit model. The parameters that need to be determined to construct the ATP power system short-circuit model are system power supply parameters, transformer parameters and cable line parameters. The above-mentioned system power supply parameters include rated voltage and frequency, positive sequence, negative sequence and zero sequence impedance and system equivalent internal impedance and reactance. The above-mentioned transformer parameters include rated capacity, rated voltage, connection mode of high voltage side, medium voltage side and low voltage side, no-load current, no-load loss, load loss and short-circuit impedance percentage. The above-mentioned cable line parameters include line length, cable model, cross-sectional size, resistivity and capacitance of cable core, resistivity and inductance of metal sheath, grounding method and grounding resistance value. The ATP power system short-circuit model constructed based on the above parameters can accurately reflect the behavior of the system under short-circuit fault conditions and improve the accuracy of simulation results.

[0084] In the ATP power system short-circuit model (i.e., the power simulation model), select the transformers and lines actually used in the project: when the line has three voltage levels, select a three-winding transformer, and set the transformer rated, short-circuit, and no-load parameters based on the transformer inventory.

[0085] When the power transmission state is high-voltage long-distance power transmission, the outgoing line selects a three-phase cross-interconnected cable line, and each cable line consists of three groups of cross-interconnected sections. The length of each cross-interconnected section can be, for example, 1500m, and a cross-interconnected transposition is performed every 500m to eliminate the influence of the induced voltage of the metal aluminum sheath. Direct grounding is performed on both sides of each cross-interconnected section, and the three-phase cables used in the line are arranged in a herringbone shape, such as a phase spacing of 0.2m. Figure 3 is a schematic diagram of a cross-sectional view of a three-phase cross-connected cable according to an optional ground impedance correction method provided in an embodiment of the present application, from Figure 3 It can be seen that the three-phase cross-interconnected cable lines are arranged in a T-shape, and each phase line has a mesh-like metal sheath outside.

[0086] In the ATP power system short-circuit model, the system power supply must be set to be equivalent to the electrical system outside the outgoing line. The following specific settings are for illustration only and are not limited to specific settings. The rated voltage of the power supply must be 5% higher than that of the power grid. Therefore, the rated voltage of the system power supply on the 220kV side is set to 231kV, and the rated voltage of the system power supply on the 110kV side is set to 115.5kV.

[0087] To set the system positive-sequence and zero-sequence equivalent impedance, we must first obtain the overall positive-sequence impedance and zero-sequence impedance of the transformer based on the three-phase short-circuit and single-phase ground short-circuit current parameters on the transformer bus side in actual engineering; secondly, check the positive-sequence and zero-sequence impedance parameters of the outgoing line from the simulation software setting interface; finally, subtract the line parameters from the overall transformer parameters to obtain the positive-sequence impedance and zero-sequence impedance required to set the system equivalent impedance.

[0088] According to the above description, the calculation formula of the per-unit value X1 of the positive-sequence impedance and the per-unit value X0 of the zero-sequence impedance at the 220kV (kilovolt) bus of the system is:

[0089]

[0090] Among them, S n Indicates the rated capacity of the transformer, U n Indicates rated voltage, I k Indicates short-circuit current.

[0091] Figure 4 It is a schematic diagram of a cable outlet short-circuit model according to an optional ground impedance correction method provided in an embodiment of the present application. The model uses the above-mentioned equipment parameters and the calculated positive-sequence and zero-sequence impedance values ​​at the bus to reasonably set parameters in the ATP power system short-circuit model to construct an underground short-circuit current calculation model including transformers, cable lines, and system power supplies. Figure 4 In the figure, the dashed box 1 is the switch of the cable line, and the dashed box 2 is the cross-connected cable. By setting the appropriate switch closing time, the single-phase short circuit to ground and two-phase short circuit to ground faults on the cable line can be simulated.

[0092] Based on the above-mentioned ATP power system short-circuit model, the ground current at the predetermined grounding point of the cable sheath can be obtained, and the total current of the short-circuit current shunted through the first conduction mode can be obtained by summing the current. The total short-circuit current is obtained based on the short-circuit current conducted through the first conduction mode and the short-circuit current conducted through the second conduction mode. The shunt coefficient is obtained based on the ratio between the total current conducted through the first conduction mode and the total short-circuit current. By calculating the ground current at multiple grounding points and summing them to obtain the shunt coefficient, the shunt situation of the short-circuit current can be reflected more accurately and comprehensively, and the accuracy of fault analysis and system testing can be improved.

[0093] Based on the total short-circuit current and the total current conducted by the first conduction mode, the shunt coefficient c can be obtained. s The formula is:

[0094]

[0095] in, represents the instantaneous value of the total current conducted by the first conduction mode, Indicates the instantaneous value of the total short-circuit current.

[0096] Figure 5 This is a schematic diagram of the grounding points of a cable line according to an optional ground impedance correction method provided in an embodiment of the present application. As can be seen from the figure, the three grounding points are grounding point A close to the system equivalent power supply end, grounding point B in the middle of the cable line, and grounding point C close to the transformer end. The dashed box is a cross-connected cable.

[0097] Using the ATP power system short-circuit model, the ground currents at the three predetermined grounding points A, B, and C are obtained, and the frequency domain decomposition is performed to obtain the 50 Hz (Hertz) power frequency components. Based on the power frequency components, the short-circuit current shunt values ​​of the three predetermined grounding points are obtained, and the sum is processed to obtain the total current conducted by the first conduction mode. Using formula (3), the current shunt coefficient is obtained.

[0098] Figure 6 is a schematic diagram of short-circuit current shunting results of an optional ground impedance correction method provided in an embodiment of the present application, Figure 6 It is divided into two sub-graphs, the upper sub-graph, the horizontal axis represents the harmonic order, and the vertical axis represents the harmonic amplitude. In the lower sub-graph, the horizontal axis represents the harmonic order, and the vertical axis represents the phase. Figure 6 For example, the magnitude of the ground current at the predetermined grounding point B can be obtained.

[0099] The ATP power system short-circuit model is used to construct the fault states corresponding to the predetermined short-circuit types, and the ground currents corresponding to the multiple predetermined grounding points of each fault state are obtained. The ground currents corresponding to the above-mentioned multiple predetermined grounding points are summed to obtain the total current of the short-circuit current shunted through the first conduction mode under the fault states corresponding to the predetermined short-circuit types. Based on the total current shunted through the first conduction mode and the total short-circuit current, the shunt coefficients under the fault states corresponding to the multiple predetermined short-circuit types are obtained. The shunt coefficients under the fault states corresponding to the above-mentioned multiple predetermined short-circuit types are averaged to obtain the shunt coefficient. The ATP power system short-circuit model can be used to simulate a variety of short-circuit types and fault states. By calculating the shunt coefficients under the fault states corresponding to the multiple short-circuit types and taking the average value, a comprehensive shunt correction coefficient suitable for cable tunnel grounding impedance testing can be obtained, which improves the test accuracy and reliability.

[0100] In the field test of cable grounding impedance, due to the presence of cable sheath, part of the test current will be shunted to the grounding grid through the cable sheath, resulting in a deviation between the initial grounding impedance value obtained by the test and the actual value. In order to more accurately reflect the actual performance of the grounding system, it is necessary to correct the initial grounding impedance result according to the shunt coefficient. The shunt coefficient is obtained based on the proportion of the short-circuit current conducted by the first conduction mode to the total short-circuit current. The initial short-circuit current conducted by the uncorrected first conduction mode is tested, and the above initial short-circuit current is corrected based on the shunt coefficient to obtain the corrected target short-circuit current conducted by the first conduction mode. Based on the target short-circuit current, Ohm's law is used to obtain the corrected target grounding impedance. Using the shunt coefficient and Ohm's law to correct the grounding impedance approximation improves the accuracy of the grounding impedance and simplifies the test process. At the same time, it is applicable to various short-circuit types and provides reliable data support for the design and optimization of the grounding system.

[0101] The ground impedance correction method can be applied to a software application, and the results of the software application are shown in Table 2. The rated capacity of a certain system transformer is 180MVA (megavolt-ampere), the rated voltage of the high voltage side is 220kV, the rated voltage of the medium voltage side is 115kV, and the rated voltage of the low voltage side is 10.5kV. The three phases of the high voltage side and the medium voltage side adopt a Y-type connection with neutral point grounding, and the low voltage side adopts a Δ-type connection. The high-voltage-low voltage load loss is 273kW (kilowatts), the high-voltage-medium voltage load loss is 579kW, and the medium-voltage-low voltage load loss is 259.6kW. The high-voltage-low voltage short-circuit impedance percentage is 44.47%, the high-voltage-medium voltage short-circuit impedance percentage is 13.36%, and the medium-voltage-low voltage short-circuit impedance percentage is 31.02%. The transformer no-load current is 0.04%, and the no-load loss is 63.99kW. There are three outgoing lines on the 220kV side and two outgoing lines on the 110kV side. The core radius is 0.0485m (meter) and the resistivity is 1.72×10 -8 Ω·m (ohm per meter); the inner radius of the metal aluminum sheath is 0.0735m, the outer radius is 0.0761m, and the resistivity is 2.8264×10 -8 Ω·m.

[0102] Based on the above information, the overall positive sequence and zero sequence impedance of the system on the 220kV side of the transformer is obtained. Based on the actual operation instructions of the basic transformer, the three-phase short-circuit current on the 220kV bus side of the transformer is 35kA (kiloamperes), and the single-phase short-circuit current is 30kA. In the short-circuit calculation, the system benchmark capacity is taken as 1000MVA and the benchmark voltage is 242kV. Based on the above benchmark capacity and benchmark voltage, the nominal value of the benchmark impedance is 242 2 / 1000=58.564Ω (ohms). Based on the above information, using formula (4) and formula (5), the per-unit value of the positive-sequence impedance is 0.0682, and the effective value is 3.994Ω; the per-unit value of the zero-sequence impedance is 0.1021, and the effective value is 5.979Ω. Similarly, the per-unit value and effective value of the overall positive-sequence impedance and the per-unit value and effective value of the zero-sequence impedance on the 110kV side of the transformer are calculated. Based on the above information, the ATP power system short-circuit model is constructed to obtain the ground currents at the three predetermined grounding points A, B, and C. The ground currents are decomposed in the frequency domain to obtain the corresponding 50Hz (Hertz) power frequency component. The results are shown in Table 2.

[0103] Table 2 Ground short-circuit current under different short-circuit conditions on the line

[0104]

[0105] Based on Table 2, it can be seen that when a short circuit occurs on the line, a large amount of short-circuit current enters the ground through different grounding points on the line, a small amount of short-circuit current enters the transformer ground grid through the outer sheath, and the comprehensive shunt of the short-circuit current directly entering the ground in the tunnel is 90%, which is independent of the short-circuit type. Therefore, when testing the ground impedance of the cable tunnel in this system on-site, if the transformer ground grid at both ends is ignored, the measured impedance should be corrected with a comprehensive shunt coefficient of 90%.

[0106] The above optional implementation methods achieve at least the following effects: construct an ATP power system short-circuit model, based on which various short-circuit types and corresponding fault conditions on the cable line can be simulated by setting appropriate switch closing time, and high-precision ground current values ​​can be obtained, thereby expanding the scope of application and improving the accuracy of shunt coefficient calculation; using the shunt coefficient, the initial ground impedance of the test is corrected to obtain the corrected target ground impedance, thereby improving the accuracy of the ground impedance, which is beneficial to the subsequent safety assessment, inspection and maintenance of the power system.

[0107] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0108] In this embodiment, a ground impedance correction device is also provided, which is used to implement the above-mentioned embodiments and preferred implementation modes, and the descriptions that have been made will not be repeated. As used below, the terms "module" and "device" can implement a combination of software and / or hardware for a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0109] According to an embodiment of the present application, a device embodiment for implementing a ground impedance correction method is also provided. Figure 7 is a schematic diagram of a ground impedance correction device according to an embodiment of the present application, such as Figure 7 As shown, the above-mentioned ground impedance correction device includes an initial ground impedance determination module 702, a ground current determination module 704, a shunt coefficient determination module 706, and a target ground impedance determination module 708. The device is described below.

[0110] The initial grounding impedance determination module 702 is used to detect the cable line to obtain the initial grounding impedance, wherein the conduction mode of the short-circuit current in the cable line includes a first conduction mode of conducting through the grounding point of the cable line and a second conduction mode of returning to the neutral point of the transformer through the metal sheath layer of the cable line;

[0111] A ground current determination module 704, connected to the initial ground impedance determination module 702, is used to determine the ground currents corresponding to a plurality of predetermined grounding points of the first conduction mode, wherein the plurality of predetermined grounding points are grounding points with different short-circuit current distributions on the cable line;

[0112] A shunt coefficient determination module 706, connected to the ground current determination module 704, is used to determine a shunt coefficient based on the ground currents corresponding to the plurality of predetermined grounding points, wherein the shunt coefficient represents a ratio of the short-circuit current conducted by the first conduction mode to the total short-circuit current, and the total short-circuit current is obtained based on the short-circuit current conducted by the first conduction mode and the short-circuit current conducted by the second conduction mode;

[0113] The target ground impedance determination module 708 is connected to the shunt coefficient determination module 706 and is used to correct the initial ground impedance according to the shunt coefficient to obtain the target ground impedance.

[0114] In a ground impedance correction device provided by an embodiment of the present application, an initial ground impedance determination module 702 is set to detect the cable line to obtain the initial ground impedance, wherein the conduction mode of the short-circuit current in the cable line includes a first conduction mode of conduction through the grounding point of the cable line and a second conduction mode of returning to the neutral point of the transformer through the metal sheath layer of the cable line; an in-ground current determination module 704 is connected to the initial ground impedance determination module 702, and is used to determine the in-ground current corresponding to multiple predetermined grounding points of the first conduction mode, wherein the multiple predetermined grounding points are the cable line. The short-circuit current distribution on the grounding points is different; the shunt coefficient determination module 706 is connected to the ground current determination module 704, and is used to determine the shunt coefficient based on the ground current corresponding to multiple predetermined grounding points, wherein the shunt coefficient represents the proportion of the short-circuit current conducted by the first conduction mode to the total short-circuit current, and the total short-circuit current is obtained based on the short-circuit current conducted by the first conduction mode and the short-circuit current conducted by the second conduction mode; the target grounding impedance determination module 708 is connected to the shunt coefficient determination module 706, and is used to correct the initial grounding impedance according to the shunt coefficient to obtain the target grounding impedance. The purpose of correcting the initial grounding impedance by using the shunt coefficient is achieved, and the technical effect of improving the accuracy of the cable grounding impedance measurement value is achieved, thereby solving the technical problem of unsatisfactory accuracy of the grounding impedance measurement value existing in the related art.

[0115] It should be noted that the above modules can be implemented by software or hardware. For example, for the latter, it can be implemented in the following ways: the above modules can be located in the same processor; or the above modules can be located in different processors in any combination.

[0116] It should be noted that the initial ground impedance determination module 702, the ground current determination module 704, the shunt coefficient determination module 706, and the target ground impedance determination module 708 correspond to steps S102 to S108 in the embodiment, and the examples and application scenarios implemented by the modules and the corresponding steps are the same, but are not limited to the contents disclosed in the above embodiments. It should be noted that the modules as part of the device can be run in a computer terminal.

[0117] It should be noted that the optional or preferred implementation of this embodiment can refer to the relevant description in the embodiment, which will not be repeated here.

[0118] The above-mentioned ground impedance correction device may also include a processor and a memory. The initial ground impedance determination module 702, the ground current determination module 704, the shunt coefficient determination module 706, the target ground impedance determination module 708, etc. are all stored in the memory as program units, and the processor executes the above-mentioned program units stored in the memory to realize the corresponding functions.

[0119] The processor includes a kernel, which retrieves the corresponding program unit from the memory. There can be one or more kernels. The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one storage chip.

[0120] An embodiment of the present application provides a non-volatile storage medium on which a program is stored. When the program is executed by a processor, a ground impedance correction method is implemented.

[0121] The embodiment of the present application provides an electronic device, which includes a processor, a memory, and a program stored in the memory and can be run on the processor. When the processor executes the program, the following steps are implemented: detecting the cable line to obtain the initial grounding impedance, wherein the conduction mode of the short-circuit current in the cable line includes a first conduction mode of conduction through the grounding point of the cable line, and a second conduction mode of returning to the neutral point of the transformer through the metal sheath layer of the cable line; determining the grounding current corresponding to multiple predetermined grounding points of the first conduction mode, wherein the multiple predetermined grounding points are grounding points with different short-circuit current distributions on the cable line; determining the shunt coefficient based on the grounding current corresponding to the multiple predetermined grounding points, wherein the shunt coefficient represents the proportion of the short-circuit current conducted by the first conduction mode to the total short-circuit current, and the total short-circuit current is obtained based on the short-circuit current conducted by the first conduction mode and the short-circuit current conducted by the second conduction mode; correcting the initial grounding impedance according to the shunt coefficient to obtain the target grounding impedance. The device in this article can be a server, a PC, etc.

[0122] The present application also provides a computer program product, which, when executed on a data processing device, is suitable for executing an initialization program having the following method steps: detecting the cable line to obtain an initial grounding impedance, wherein the conduction mode of the short-circuit current in the cable line includes a first conduction mode of conduction through the grounding point of the cable line, and a second conduction mode of returning to the neutral point of the transformer through the metal sheath layer of the cable line; determining the ground current corresponding to multiple predetermined grounding points of the first conduction mode, wherein the multiple predetermined grounding points are grounding points with different short-circuit current distributions on the cable line; determining a shunt coefficient based on the ground current corresponding to the multiple predetermined grounding points, wherein the shunt coefficient represents the proportion of the short-circuit current conducted by the first conduction mode to the total short-circuit current, and the total short-circuit current is obtained based on the short-circuit current conducted by the first conduction mode and the short-circuit current conducted by the second conduction mode; and correcting the initial grounding impedance according to the shunt coefficient to obtain a target grounding impedance.

[0123] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0124] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0125] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0126] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0127] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0128] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0129] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules 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 technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0130] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0131] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0132] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A ground impedance correction method, characterized in that: include: Detecting the cable line to obtain an initial grounding impedance, wherein the conduction mode of the short-circuit current in the cable line includes a first conduction mode of conducting through a grounding point of the cable line and a second conduction mode of returning to a neutral point of a transformer through a metal sheath layer of the cable line; Determine the ground currents respectively corresponding to a plurality of predetermined grounding points of the first conduction mode, wherein the plurality of predetermined grounding points are grounding points with different short-circuit current distributions on the cable line; Determine a shunt coefficient based on the ground currents respectively corresponding to the multiple predetermined grounding points, wherein the shunt coefficient represents a ratio of the short-circuit current conducted by the first conduction mode to the total short-circuit current, and the total short-circuit current is obtained based on the short-circuit current conducted by the first conduction mode and the short-circuit current conducted by the second conduction mode; The initial ground impedance is corrected according to the shunt coefficient to obtain a target ground impedance.

2. The method according to claim 1, characterized in that The determining of the shunt coefficient based on the ground currents respectively corresponding to the plurality of predetermined grounding points includes: Determining the total short-circuit current based on a reference voltage and a reference current of the transformer according to a predetermined short-circuit type; The shunt coefficient is determined according to the ground currents respectively corresponding to the plurality of predetermined grounding points and the total short-circuit current.

3. The method according to claim 2, characterized in that The determining of the shunt coefficient according to the ground currents respectively corresponding to the plurality of predetermined grounding points and the total short-circuit current includes: Adding up the ground currents respectively corresponding to the plurality of predetermined grounding points to determine the added short-circuit current of the first conduction mode; The shunt coefficient is determined based on a ratio between the summed short-circuit current and the total short-circuit current.

4. The method according to claim 2, characterized in that: The determining the total short-circuit current based on the reference voltage and the reference current of the transformer according to the predetermined short-circuit type includes: According to the predetermined short-circuit type, determining an additional impedance and a predetermined coefficient, wherein the predetermined coefficient is determined based on the number of phases with faults in the three-phase electricity of the predetermined short-circuit type, and the additional impedance is used to characterize the influence of the flow paths of different sequence currents in the transformer on the short-circuit current; The total short-circuit current is determined based on the reference voltage, the reference current, the additional impedance, and the predetermined coefficient.

5. The method according to claim 1, characterized in that The determining of the ground currents respectively corresponding to the plurality of predetermined grounding points of the first conduction mode includes: Using a predetermined power simulation model to perform line opening and closing control to generate a fault state corresponding to a predetermined short circuit type, wherein the power simulation model is determined based on cable line parameters, transformer parameters, and system power supply parameters; In the fault state, ground currents respectively corresponding to the plurality of predetermined grounding points are determined.

6. The method according to claim 5, characterized in that The method further comprises: In the case where there are multiple predetermined short-circuit types, summing up the ground currents corresponding to the multiple predetermined grounding points according to the fault states corresponding to the multiple predetermined short-circuit types, and determining the summed short-circuit currents corresponding to the multiple predetermined short-circuit types; Determine the shunt coefficients corresponding to the plurality of predetermined short-circuit types respectively based on the summed short-circuit currents and the total short-circuit currents corresponding to the plurality of predetermined short-circuit types respectively; The shunt coefficient is determined based on the shunt coefficients respectively corresponding to the plurality of predetermined short-circuit types by using an average value processing method.

7. The method according to any one of claims 1 to 6, characterized in that: The plurality of predetermined grounding points include an equivalent power supply terminal grounding point and a transformer terminal grounding point.

8. A ground impedance correction device, characterized in that: include: An initial grounding impedance determination module is used to detect the cable line to obtain the initial grounding impedance, wherein the conduction mode of the short-circuit current in the cable line includes a first conduction mode of conducting through the grounding point of the cable line and a second conduction mode of returning to the neutral point of the transformer through the metal sheath layer of the cable line; A ground current determination module, used to determine the ground currents corresponding to a plurality of predetermined grounding points of the first conduction mode, wherein the plurality of predetermined grounding points are grounding points with different short-circuit current distributions on the cable line; a shunt coefficient determination module, configured to determine a shunt coefficient based on the ground currents respectively corresponding to the plurality of predetermined grounding points, wherein the shunt coefficient represents a ratio of the short-circuit current conducted by the first conduction mode to the total short-circuit current, and the total short-circuit current is obtained based on the short-circuit current conducted by the first conduction mode and the short-circuit current conducted by the second conduction mode; The target grounding impedance determination module is used to correct the initial grounding impedance according to the shunt coefficient to obtain the target grounding impedance.

9. A non-volatile storage medium, characterized in that: The non-volatile storage medium stores a plurality of instructions, and the instructions are suitable for being loaded by a processor and executing the ground impedance correction method described in any one of claims 1 to 7.

10. An electronic device, characterized in that: include: One or more processors and a memory, wherein the memory is used to store one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors implement the ground impedance correction method described in any one of claims 1 to 7.

Images