Neutral-to-ground voltage measurement method and device for power grid measurement switch and medium thereof

Abstract

The application provides a neutral line-to-ground voltage measurement method and device of a power grid measurement switch and a medium thereof. The current value and voltage value corresponding to a first phase conductor, a second phase conductor and a third phase conductor are obtained, the zero sequence current value of the neutral line is determined according to each current value, the zero sequence voltage value of the neutral line is determined according to each voltage value, when any current value suddenly changes, the phase conductor in which the current suddenly changes is determined as a sudden change phase conductor, and the current change amount, voltage change amount and zero sequence current change amount of the sudden change phase conductor before and after the sudden change are determined; the zero line total impedance and equivalent fire line total impedance are calculated according to the zero sequence current value, zero sequence voltage value, current change amount, voltage change amount and zero sequence current change amount; and the ground voltage value of the neutral line is determined according to the equivalent fire line total impedance, zero line total impedance and zero sequence voltage value, so that the ground voltage of the neutral line can be indirectly obtained without additional wiring.

Description

Technical Field

[0001] This application relates to the field of low-voltage power distribution technology, and in particular to a method, device and medium for measuring the neutral line-to-ground voltage of a power grid measuring switch. Background Technology

[0002] Three-phase four-wire systems are widely used in low-voltage power distribution networks and terminal power supply scenarios containing single-phase loads. Their operational safety is closely related to power quality. Because three-phase loads are difficult to maintain perfect symmetry in actual operation, an unbalanced current exists on the neutral line for a long time, causing a continuous potential shift between the load-side neutral point and the power supply-side neutral point. This neutral point potential shift will cause a redistribution of voltages relative to the neutral points, directly affecting the voltage withstand level of equipment and potentially leading to safety hazards such as neutral line overload, protection malfunction, and even electric shock. Therefore, the neutral-to-ground voltage is an important comprehensive characteristic quantity for measuring the operational health of a low-voltage power distribution system.

[0003] However, currently installed smart measuring switches typically only directly acquire the voltage of each phase conductor relative to the neutral line, and then calculate the zero-sequence voltage using the three-phase voltage phasor sum. However, due to the lack of a ground reference point and insufficient information on the impedance of the live and neutral wires, they cannot directly obtain the crucial parameter of the neutral-to-ground voltage. Existing indirect measurement methods often require the additional installation of a ground voltage transformer or the introduction of an independent grounding point, which is complex, costly, and difficult to promote in existing equipment. Therefore, a method is needed that can indirectly obtain the neutral-to-ground voltage based on the existing hardware of the measuring switch without requiring additional wiring. Summary of the Invention

[0004] The purpose of this application is to at least solve one of the technical problems existing in the prior art, and to provide a method, device and medium for measuring the neutral line to ground voltage of a power grid measuring switch, which can indirectly obtain the neutral line to ground voltage without additional wiring.

[0005] To achieve the above objectives, a first aspect of this application provides a method for measuring the neutral-to-ground voltage of a power grid measuring switch. The power grid measuring switch includes a first-phase conductor, a second-phase conductor, a third-phase conductor, and a neutral conductor connected in parallel. The method includes: Obtain the first current and first voltage values ​​of the first phase conductor, the second current and second voltage values ​​of the second phase conductor, and the third current and third voltage values ​​of the third phase conductor under the current power frequency cycle; The zero-sequence current value of the neutral line is determined based on the first current value, the second current value, and the third current value. The zero-sequence voltage value of the neutral line is determined based on the first voltage value, the second voltage value, and the third voltage value. When any one of the first current value, the second current value, or the third current value changes abruptly, the phase conductor in which the current changes abruptly, is identified as the abruptly changed phase conductor, and the changes in current, voltage, and zero-sequence current of the neutral line before and after the abrupt change are determined. Based on the zero-sequence current value, zero-sequence voltage value, current change, voltage change, and zero-sequence current change, calculate the total neutral impedance and equivalent live wire total impedance of the measuring switch on the power supply side. The neutral voltage to ground is determined based on the equivalent total impedance of the live wire, the total impedance of the neutral wire, and the zero-sequence voltage value.

[0006] Furthermore, in some embodiments, when any one of the first current value, the second current value, or the third current value undergoes a sudden change and the change exceeds a preset threshold, the phase conductor in which the current changes abruptly, is identified as the abruptly changing phase conductor, including: Obtain the fourth current value of the first phase conductor, the fifth current value of the second phase conductor, and the sixth current value of the second phase conductor under the previous power frequency cycle; If the vector difference between the first current value and the fourth current value is greater than a preset threshold, it is determined that the first current value has abruptly changed, and the corresponding first phase conductor is identified as the abruptly changed phase conductor. Alternatively, if the vector difference between the second current value and the fifth current value is greater than a preset threshold, then it is determined that the second current value has abruptly changed, and the corresponding second phase conductor is determined as the abruptly changed phase conductor. Alternatively, if the vector difference between the third current value and the sixth current value is greater than a preset threshold, then the third current value is determined to have a sudden change, and the corresponding third phase conductor is determined to be the sudden change phase conductor. The preset threshold is 10% of the rated current of the measuring switch.

[0007] Furthermore, in some embodiments, the calculation of the total neutral impedance and the equivalent total live wire impedance of the measuring switch on the power supply side based on the zero-sequence current value, zero-sequence voltage value, current change, voltage change, and zero-sequence current change includes: Based on the loop voltage constraints of the conductor before and after the abrupt change, the first correlation equation between the change in current, the change in voltage, and the change in zero-sequence current is established. Based on the circuit constraints between zero-sequence voltage, zero-sequence current and line impedance, a second correlation equation is established between the zero-sequence voltage value and the zero-sequence current value, the equivalent total impedance of the live wire and the total impedance of the neutral wire. Based on the zero-sequence current value, zero-sequence voltage value, current change, voltage change, and zero-sequence current change, the first and second correlation equations are solved simultaneously to obtain the equivalent total impedance of the live wire and the total impedance of the neutral wire.

[0008] Furthermore, in some embodiments, the first correlation equation established based on the loop voltage constraints of the abruptly changing phase conductor before and after the abrupt change, and the zero-sequence current change, includes: Based on the loop voltage constraints of the abrupt phase conductor before and after the abrupt change, the first abrupt voltage equation for the abrupt phase conductor at the moment before the abrupt change and the second abrupt voltage equation at the moment after the abrupt change are established respectively. Subtracting the first and second sudden voltage equations yields the first correlation equation.

[0009] Furthermore, in some embodiments, determining the neutral-to-ground voltage value based on the equivalent total live wire impedance, the total neutral wire impedance, and the zero-sequence voltage value includes: Based on a three-phase four-wire circuit with a measuring switch, circuit constraint equations are established between the zero-sequence voltage value, the voltage value to ground, and the equivalent total impedance of the live wire and the total impedance of the neutral wire. Based on the neutral loop voltage equation and circuit constraint equations relating the total neutral impedance, zero-sequence current value, and voltage to ground value, the amplitude ratio between the zero-sequence voltage value and the voltage to ground value is determined. The amplitude ratio is determined by the ratio of the equivalent total live wire impedance to the total neutral impedance. Calculate the voltage to ground based on the amplitude ratio and the zero-sequence voltage value.

[0010] Furthermore, in some embodiments, the circuit constraint equations established between the zero-sequence voltage value, the voltage value to ground, and the equivalent total impedance of the live wire and the total impedance of the neutral wire in the above-mentioned three-phase four-wire circuit based on the measuring switch include: Based on Kirchhoff's voltage law, the first-loop voltage equation for the first-phase conductor, the second-loop voltage equation for the second-phase conductor, and the third-loop voltage equation for the third-phase conductor are established. Based on the characteristic that the sum of the three-phase power supply potentials is zero under a three-phase four-wire circuit, the voltage equations of the first loop, the voltage equation of the second loop, and the voltage equation of the third loop are superimposed and summed to obtain the third correlation equation between the zero-sequence voltage value, the voltage value to ground, the equivalent total impedance of the live wire, and the total value of the three-phase current. The total value of the three-phase current is the sum of the first current value, the second current value, and the third current value. Based on Kirchhoff's current law, a fourth correlation equation is determined between the total value of the three-phase current and the value of the zero-sequence current. Based on the fourth and third correlation equations, determine the circuit constraint equations.

[0011] Furthermore, in some embodiments, determining the zero-sequence current value of the neutral line based on the first current value, the second current value, and the third current value includes: The zero-sequence current value of the neutral line is obtained by performing a vector sum operation on the first current value, the second current value, and the third current value.

[0012] Furthermore, in some embodiments, determining the zero-sequence voltage value of the neutral line based on the first voltage value, the second voltage value, and the third voltage value includes: The zero-sequence voltage value of the neutral line is obtained by performing a vector sum operation on the first, second, and third voltage values.

[0013] To achieve the above objectives, a second aspect of the present application provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the neutral-to-ground voltage measurement method of the power grid measuring switch described in the first aspect.

[0014] To achieve the above objectives, a third aspect of the present application provides a storage medium, which is a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the neutral-to-ground voltage measurement method of the power grid measuring switch described in the first aspect.

[0015] According to an embodiment of this application, a method, device, and medium for measuring the neutral-to-ground voltage of a power grid measuring switch have at least the following beneficial effects: the neutral-to-ground voltage can be obtained online by collecting the three-phase current and three-phase voltage by the measuring switch itself, without the need for additional hardware or modification of the primary wiring, effectively reducing system modification costs and construction complexity; when a sudden change in any phase current is detected, the equivalent total impedance of the live wire and the total impedance of the neutral wire on the power supply side can be accurately calculated by using the changes in current, voltage, and zero-sequence current before and after the change, thus solving the problem that the line impedance parameters cannot be directly obtained in the prior art. Based on this, the neutral-to-ground voltage value can be calculated based on the equivalent total impedance of the live wire and the total impedance of the neutral wire, combined with the currently acquired zero-sequence voltage value, thereby realizing online measurement of the ground voltage without relying on additional hardware. The measurement results are not affected by load fluctuations, thus realizing non-intrusive and low-cost online detection of the neutral-to-ground voltage, providing a reliable data foundation for voltage quality assessment, neutral fault early warning, and protection strategy optimization.

[0016] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the description and the accompanying drawings. Attached Figure Description

[0017] The accompanying drawings are used to provide a further understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0018] The present application will be further described below with reference to the accompanying drawings and embodiments; Figure 1 This is an optional flowchart of the neutral-to-ground voltage measurement method for the power grid measuring switch provided in this application embodiment; Figure 2 This is an optional flowchart provided in an embodiment of the present application for identifying a phase conductor where the current changes abruptly as a phase conductor with a sudden change; Figure 3 This is provided by the embodiments of this application. Figure 1 An optional flowchart for step S105; Figure 4 This is a simplified equivalent model diagram of the three-phase four-wire circuit of the measuring switch provided in the embodiments of this application; Figure 5 This is provided by the embodiments of this application. Figure 1 An optional flowchart for step S104; Figure 6 This is provided by the embodiments of this application. Figure 1 An optional flowchart for step S105; Figure 7 This is provided by the embodiments of this application. Figure 6 An optional flowchart for step S501; Figure 8 This is an optional schematic diagram of a Simulink simulation model of a three-phase four-wire system provided in the embodiments of this application; Figure 9 This is a schematic diagram of an optional hardware structure of the electronic device provided in the embodiments of this application. Detailed Implementation

[0019] This section will describe in detail the specific embodiments of this application. Preferred embodiments of this application are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of this application, but they should not be construed as limiting the scope of protection of this application.

[0020] In the description of this application, the use of "first" and "second" is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of the indicated technical features. It should be understood that such use of data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0022] Three-phase four-wire systems are widely used in low-voltage power distribution networks and terminal power supply scenarios containing single-phase loads. Their operational safety is closely related to power quality. Because three-phase loads are difficult to maintain perfect symmetry in actual operation, an unbalanced current exists on the neutral line for a long time, causing a continuous potential shift between the load-side neutral point and the power supply-side neutral point. This neutral point potential shift will cause a redistribution of voltages relative to the neutral points, directly affecting the voltage withstand level of equipment and potentially leading to safety hazards such as neutral line overload, protection malfunction, and even electric shock. Therefore, the neutral-to-ground voltage is an important comprehensive characteristic quantity for measuring the operational health of a low-voltage power distribution system.

[0023] However, currently installed smart measuring switches typically only directly acquire the voltage of each phase conductor relative to the neutral line, and then calculate the zero-sequence voltage using the three-phase voltage phasor sum. However, due to the lack of a ground reference point and insufficient information on the impedance of the live and neutral wires, they cannot directly obtain the crucial parameter of the neutral-to-ground voltage. Existing indirect measurement methods often require the additional installation of a ground voltage transformer or the introduction of an independent grounding point, which is complex, costly, and difficult to promote in existing equipment. Therefore, a method is needed that can indirectly obtain the neutral-to-ground voltage based on the existing hardware of the measuring switch without requiring additional wiring.

[0024] Based on this, embodiments of this application provide a method, device and medium for measuring the neutral line-to-ground voltage of a power grid measuring switch, which can indirectly obtain the neutral line-to-ground voltage without additional wiring.

[0025] Therefore, the embodiments of this application will be further described below with reference to the accompanying drawings.

[0026] Reference Figure 1 As shown, Figure 1 This is an optional flowchart of a method for measuring the neutral line-to-ground voltage of a power grid measuring switch provided in this application embodiment. The power grid measuring switch includes a first phase conductor A, a second phase conductor B, a third phase conductor C, and a neutral line N connected in parallel. The method may include, but is not limited to, steps S101 to S105.

[0027] Step S101: Obtain the first current value and first voltage value of the first phase conductor, the second current value and second voltage value of the second phase conductor, and the third current value and third voltage value of the third phase conductor under the current power frequency cycle.

[0028] Specifically, the measuring switch has a built-in current sampling unit and a voltage sampling unit. The current sampling unit, through a current transformer connected to the first, second, and third phase conductors, collects the instantaneous current values ​​of the first, second, and third phase conductors respectively within one power frequency cycle at a preset sampling frequency, and obtains the first current value through phasor calculation. Second current value and the third current value The voltage sampling unit synchronously acquires the instantaneous voltage values ​​of each phase conductor relative to the neutral line through voltage measurement circuits connected in parallel between the first phase conductor and the neutral line, the second phase conductor and the neutral line, and the third phase conductor and the neutral line. The first voltage value is obtained through phasor calculation. Second voltage value and the third voltage value The aforementioned first current value First voltage value Second current value Second voltage value Third current value Third voltage value All correspond to the same current power frequency cycle and retain phase information.

[0029] Step S102: Determine the zero-sequence current value of the neutral line based on the first current value, the second current value, and the third current value.

[0030] Furthermore, in the process of determining the zero-sequence current value of the neutral line based on the first current value, the second current value, and the third current value, the following steps may be included: performing a vector sum operation on the first current value, the second current value, and the third current value to obtain the zero-sequence current value of the neutral line.

[0031] Specifically, the data processing unit built into the measuring switch acquires the first current value obtained through phasor calculation in step S101. Second current value and the third current value Then, according to Kirchhoff's current law, the three current phasors are vector summed, that is, according to... Thus, the zero-sequence current value of the neutral line is obtained. The zero-sequence current value It characterizes the phasor form of the unbalanced current flowing through the neutral line during the current power frequency cycle.

[0032] Step S103: Determine the zero-sequence voltage value of the neutral line based on the first voltage value, the second voltage value, and the third voltage value.

[0033] Furthermore, in the process of determining the zero-sequence voltage value of the neutral line based on the first voltage value, the second voltage value, and the third voltage value, the following steps may be included: performing a vector sum operation on the first voltage value, the second voltage value, and the third voltage value to obtain the zero-sequence voltage value of the neutral line.

[0034] Specifically, the data processing unit built into the measuring switch acquires the first voltage value obtained through phasor calculation in step S101. Second voltage value and the third voltage value Then, according to Kirchhoff's current law, the three voltage phasors are vector summed, that is, according to... Thus, the zero-sequence voltage value of the neutral line is obtained. The zero-sequence voltage value It characterizes the asymmetric components of the three-phase voltage with respect to the neutral line within the current power frequency cycle.

[0035] Step S104: When any one of the first current value, the second current value, or the third current value changes abruptly, the phase conductor in which the current changes abruptly is identified as the abruptly changed phase conductor, and the changes in current, voltage, and zero-sequence current of the neutral line are determined before and after the abrupt change in the abruptly changed phase conductor.

[0036] The data processing unit built into the measuring switch continuously acquires the first current value during the continuous power frequency cycle. Second current value and the third current value and the first current value of the current power frequency cycle ( ), second current value ( ), third current value ( The first current value stored corresponding to the previous power frequency cycle ( ), second current value ( ), third current value ( The comparison is performed one by one, where T is the duration of the power frequency cycle. When the first current value is detected... Second current value and the third current value If the vector difference amplitude of any one of them exceeds a preset threshold, it is determined that the phase current has abruptly changed, and the phase conductor is identified as the abruptly changing phase conductor. .

[0037] In determining the abrupt phase conductor Subsequently, the data processing unit acquires the abrupt phase conductor. Current value at the moment before the sudden change and voltage value Current value at a moment after the sudden change and voltage value And the zero-sequence current value of the neutral line at the moment before the abrupt change. and the zero-sequence current value at the moment after the abrupt change Based on the corresponding electrical quantities at the two moments before and after the abrupt change, the change in current of the conductor in the abrupt phase before and after the abrupt change is determined. Voltage change and the change in zero-sequence current of the neutral line .

[0038] It should be noted that, , The change in zero-sequence current of the neutral line Where t1-t2=T, and T is the power frequency period. In one embodiment, the power frequency period T = 0.02s.

[0039] Step S105: Calculate the total impedance of the neutral wire and the equivalent total impedance of the live wire on the power supply side of the measuring switch based on the zero-sequence current value, zero-sequence voltage value, current change, voltage change and zero-sequence current change.

[0040] The data processing unit built into the measuring switch uses the current change determined in step S104. Voltage change and the change in zero-sequence current of the neutral line and the zero-sequence current values ​​obtained in steps S102 and S103. and zero-sequence voltage value As input parameters, based on the voltage balance relationship that the circuit on the power supply side of the measuring switch should satisfy before and after the abrupt change, as well as the circuit constraint relationship between zero-sequence voltage, zero-sequence current, and line impedance, the total neutral impedance of the measuring switch on the power supply side is solved by simultaneous calculations. and equivalent live wire total impedance .

[0041] It should be noted that the equivalent total impedance of the live wire is... Total impedance of neutral line .

[0042] Step S106: Determine the neutral line voltage to ground based on the equivalent total impedance of the live wire, the total impedance of the neutral wire, and the zero-sequence voltage value.

[0043] Specifically, the data processing unit built into the measuring switch acquires the equivalent total live wire impedance and neutral wire impedance calculated in step S105, as well as the zero-sequence voltage value obtained in step S103. Based on the relationship between the zero-sequence voltage value and the neutral-to-ground voltage value, and the equivalent total live wire impedance... and total impedance of neutral line The circuit constraints determined by the joint factors, combined with the zero-sequence voltage value under the current power frequency cycle. The neutral line voltage to ground value was calculated. .

[0044] In specific embodiments of steps S101 to S106, the neutral-to-ground voltage can be obtained online by measuring the three-phase current and three-phase voltage collected by the measuring switch itself, without the need for additional hardware or modification of the primary wiring, effectively reducing system modification costs and construction complexity. When a sudden change in any phase current is detected, the equivalent total impedance of the live wire and the total impedance of the neutral wire on the power supply side can be accurately calculated by using the changes in current, voltage, and zero-sequence current before and after the change, thus solving the problem that the line impedance parameters cannot be directly obtained in the prior art. Based on this, the neutral-to-ground voltage value can be calculated based on the equivalent total impedance of the live wire and the total impedance of the neutral wire, combined with the currently obtained zero-sequence voltage value. Thus, online measurement of the ground voltage can be achieved without relying on additional hardware, and the measurement results are not affected by load fluctuations. This achieves non-intrusive, low-cost online detection of the neutral-to-ground voltage, providing a reliable data foundation for voltage quality assessment, neutral fault early warning, and protection strategy optimization.

[0045] Reference Figure 2 As shown, Figure 2 This is an optional flowchart provided in the embodiments of this application for identifying a phase conductor whose current changes abruptly as a phase conductor with abrupt changes. The method may include, but is not limited to, steps S201 to S204.

[0046] Step S201: Obtain the fourth current value of the first phase conductor, the fifth current value of the second phase conductor, and the sixth current value of the second phase conductor under the previous power frequency cycle.

[0047] Specifically, the data processing unit built into the measuring switch, after acquiring and processing the first, second, and third current values ​​in each power frequency cycle, stores these values ​​in the storage unit. When performing a sudden change determination in the current power frequency cycle, the data processing unit reads the first, second, and third current values ​​stored in the previous power frequency cycle from the storage unit and records them as the fourth current value. ( ), fifth current value ( ) and the sixth current value ( (), which serves as the benchmark for determining current power frequency cycle mutations.

[0048] Step S202: If the vector difference between the first current value and the fourth current value is greater than a preset threshold, it is determined that the first current value has abruptly changed, and the corresponding first phase conductor is determined as the abruptly changed phase conductor.

[0049] Specifically, after the data processing unit built into the measuring switch obtains the first current value of the current power frequency cycle and the fourth current value read in step S201, it calculates the first current value. ( ) and the fourth current value ( vector difference When the vector difference amplitude exceeds a preset threshold, the data processing unit determines that the current in the first phase conductor has changed significantly within one power frequency cycle, confirming the first current value. ( A sudden change occurs, and the first phase conductor A is identified as the abruptly changed phase conductor. .

[0050] Step S203: Alternatively, if the vector difference between the second current value and the fifth current value is greater than a preset threshold, then it is determined that the second current value has abruptly changed, and the corresponding second phase conductor is determined as the abruptly changed phase conductor.

[0051] Specifically, after the data processing unit built into the measuring switch obtains the second current value of the current power frequency cycle and the fifth current value read in step S201, it calculates the second current value. ( ) and the fifth current value ( vector difference When the vector difference amplitude exceeds a preset threshold, the data processing unit determines that the current in the second phase conductor has changed significantly within one power frequency cycle, confirming the second current value. ( A sudden change occurs, and the second-phase conductor B is identified as the abruptly changed phase conductor. .

[0052] Step S204: Alternatively, if the vector difference between the third current value and the sixth current value is greater than a preset threshold, then it is determined that the third current value has abruptly changed, and the corresponding third phase conductor is determined as the abruptly changed phase conductor.

[0053] Specifically, after the data processing unit built into the measuring switch obtains the third current value of the current power frequency cycle and the sixth current value read in step S201, it calculates the third current value. ( ) and the sixth current value ( vector difference When the vector difference amplitude exceeds a preset threshold, the data processing unit determines that the current in the third-phase conductor has changed significantly within one power frequency cycle, confirming the third current value. ( A sudden change occurs, and the third-phase conductor C is identified as the abruptly changed phase conductor. .

[0054] The preset threshold is 10% of the rated current of the measuring switch.

[0055] In the specific embodiments of steps S201 to S204, by independently comparing the current vector difference amplitude of adjacent power frequency cycles phase by phase, and using 10% of the rated current of the measuring switch as a preset threshold, the phase conductors whose current changes abruptly can be accurately identified and reliably determined as abruptly changing phase conductors. This avoids misjudgments caused by normal load fluctuations or measurement noise, and provides a reliable prerequisite for the accurate calculation of the total impedance of the neutral line and the equivalent total impedance of the live line, thereby ensuring the accuracy and robustness of the neutral line-to-ground voltage measurement results.

[0056] Reference Figure 3 As shown, Figure 3 This is provided by the embodiments of this application. Figure 1 An optional flowchart for step S105, the method may include, but is not limited to, steps S301 to S303.

[0057] Step S301: Based on the loop voltage constraints of the abruptly changed phase conductor before and after the abrupt change, establish the first correlation equation between the change in current, the change in voltage, and the change in zero-sequence current.

[0058] Specifically, refer to Figure 4 As shown, Figure 4 This is a simplified equivalent model diagram of the three-phase four-wire circuit of the measuring switch provided in the embodiments of this application. The simplified equivalent model in the diagram includes the three-phase power supply potential. , , Measure the equivalent total live wire impedance of each phase conductor on the switching power supply side. ( =A, B, C), total impedance of the neutral wire (A, B, C) Three-phase conductor current Neutral zero-sequence current Each phase conductor relative to the load-side neutral point The voltages are respectively , , Each phase conductor relative to the load-side neutral point voltage , , and load-side neutral point voltage to ground relative to the neutral point on the power supply side .in, , , = , , .

[0059] In this circuit model, the conductor with the abrupt change in phase satisfies the loop voltage constraint determined by Kirchhoff's voltage law both before and after the abrupt change. Taking the conductor with the abrupt change as the first phase conductor A as an example, assume that the fourth current before the abrupt change is... The fourth voltage value before the mutation was The equivalent total impedance of the live wire is The zero-sequence current value of the neutral line is The power source potential before the sudden change Equal to the total impedance of the equivalent live wire The voltage drop on top plus the fourth voltage value Plus the total impedance of the neutral wire The pressure drop above, i.e. = Furthermore, assume the first current value after the abrupt change is... The first voltage value after the mutation is The zero-sequence current value of the neutral line is Then the power supply potential after the sudden change Equal to the total impedance of the equivalent live wire The voltage drop across plus the first voltage value Plus the total impedance of the neutral wire The pressure drop above, i.e. = The above are combined = = The first correlation equation is obtained as follows: .

[0060] Step S302: Based on the circuit constraints between zero-sequence voltage, zero-sequence current and line impedance, establish a second correlation equation between the zero-sequence voltage value, zero-sequence current value, equivalent live wire total impedance and neutral wire total impedance.

[0061] exist Figure 4 In the simplified equivalent model of the three-phase four-wire circuit shown, based on Kirchhoff's voltage law and current law, it can be derived that the zero-sequence voltage value, zero-sequence current value, equivalent total live wire impedance, and total neutral wire impedance satisfy inherent circuit constraint relationships. Taking the abruptly changing phase conductor as the first phase conductor A as an example, the specific derivation process is as follows: At the neutral point on the load side, according to Kirchhoff's current law, the sum of the currents in the three phase conductors and the zero-sequence current of the neutral line satisfy... The relationship is that the total value of the three-phase current is equal in magnitude and opposite in direction to the zero-sequence current. The voltage of the three-phase conductors relative to the neutral point on the load side is considered. , , Summing yields the zero-sequence voltage value. By utilizing the characteristic that the sum of the potentials of the three-phase power supply is zero under three-phase symmetrical power conditions, and combining this with the loop voltage equations of each phase conductor, the zero-sequence voltage value can be obtained through summation. Equal to the total impedance of the equivalent live wire With neutral zero-sequence current The product plus three times the total impedance of the neutral line With neutral zero-sequence current The product of, i.e. This relationship characterizes the circuit constraints between the zero-sequence voltage value, the zero-sequence current value, the equivalent total impedance of the live wire, and the total impedance of the neutral wire; it is the second correlation equation.

[0062] Step S303: Based on the zero-sequence current value, zero-sequence voltage value, current change, voltage change and zero-sequence current change, solve the first correlation equation and the second correlation equation simultaneously to obtain the equivalent total impedance of the live wire and the total impedance of the neutral wire.

[0063] Taking the abruptly changing phase conductor as the first phase conductor A as an example, let... , , Then the simultaneous system of equations of the first and second correlation equations can be written as: .

[0064] Solving the equations simultaneously, we obtain the equivalent total live wire impedance corresponding to the abrupt phase conductor. and the total impedance of the neutral wire .

[0065] In specific embodiments of steps S301 to S303, based on the simplified equivalent model of the three-phase four-wire circuit of the measuring switch, a first correlation equation is established using the loop voltage constraints satisfied by the abrupt phase conductor before and after the abrupt change. A second correlation equation is established using the inherent circuit constraints between zero-sequence voltage, zero-sequence current, and line impedance. This transforms the line impedance parameters, which are originally difficult to measure directly, into unknown quantities that can be solved using known electrical quantities. Using current change, voltage change, and zero-sequence current change as excitation response characteristic quantities, combined with the steady-state zero-sequence current and zero-sequence voltage values, by simultaneously solving the two correlation equations, the equivalent total live wire impedance and total neutral wire impedance on the measuring switch power supply side can be accurately calculated without relying on external injected signals or additional measuring devices. This provides a key parameter basis for the subsequent determination of the neutral-to-ground voltage.

[0066] Reference Figure 5 As shown, Figure 5 This is provided by the embodiments of this application. Figure 1 An optional flowchart for step S104, the method may include, but is not limited to, steps S401 to S402.

[0067] Step S401: Based on the loop voltage constraints of the abrupt phase conductor before and after the abrupt change, establish the first abrupt change voltage equation for the abrupt phase conductor at the moment before the abrupt change and the second abrupt change voltage equation at the moment after the abrupt change.

[0068] exist Figure 4 In the circuit model, the conductor with the abrupt change in phase satisfies the loop voltage constraint determined by Kirchhoff's voltage law both before and after the abrupt change. Taking the conductor with the abrupt change as the first phase conductor A as an example, assume that the fourth current before the abrupt change is... The fourth voltage value before the mutation was The equivalent total impedance of the live wire is The zero-sequence current value of the neutral line is The power source potential before the sudden change Equal to the total impedance of the equivalent live wire The voltage drop on top plus the fourth voltage value Plus the total impedance of the neutral wire The pressure drop above, i.e. = This leads to the first sudden voltage equation. .

[0069] Furthermore, assuming the first current value after the abrupt change is... The first voltage value after the mutation is The zero-sequence current value of the neutral line is Then the power supply potential after the sudden change Equal to the total impedance of the equivalent live wire The voltage drop across plus the first voltage value Plus the total impedance of the neutral wire The pressure drop above, i.e. = This leads to the second sudden voltage equation. .

[0070] Step S402: Subtract the first sudden voltage equation from the second sudden voltage equation to obtain the first correlation equation.

[0071] Specifically, the first sudden voltage equation With the second sudden voltage equation Subtraction is performed to obtain the first correlation equation. .

[0072] Reference Figure 6 As shown, Figure 6 This is provided by the embodiments of this application. Figure 1 An optional flowchart for step S105, the method may include, but is not limited to, steps S501 to S503.

[0073] Step S501: Based on the three-phase four-wire circuit of the measuring switch, establish the circuit constraint equations between the zero-sequence voltage value, the voltage value to ground, and the equivalent total impedance of the live wire and the total impedance of the neutral wire.

[0074] Specifically, in the three-phase four-wire circuit of the measuring switch, the voltage to ground between the neutral point on the three-phase power supply side and the neutral point on the load side means that the voltage of each phase conductor relative to the neutral point on the load side includes not only the difference between the power supply potential and the voltage drop across the live wire impedance, but also the influence of the voltage to ground.

[0075] Based on the three-phase four-wire circuit architecture of the measuring switch, the data processing unit utilizes the constraint relationships between various electrical quantities determined by Kirchhoff's voltage law and current law. Combined with the inherent characteristic that the sum of the three-phase power supply potentials is zero under three-phase symmetrical power conditions, it establishes and superimposes the voltage equations for each phase conductor loop, eliminating the power supply potential term. The total three-phase current is expressed as the zero-sequence current value. The circuit constraint equations between the zero-sequence voltage value and the equivalent total impedance of the live wire, the total impedance of the neutral wire, the zero-sequence current value, and the voltage to ground are then derived. The circuit constraint equations quantitatively describe the analytical relationship between the zero-sequence voltage, the voltage to ground, and the equivalent total impedance of the live wire and the total impedance of the neutral wire.

[0076] Step S502: Determine the amplitude ratio between the zero-sequence voltage value and the voltage to ground based on the neutral loop voltage equation and circuit constraint equations between the total neutral impedance, the zero-sequence current value and the voltage to ground.

[0077] The amplitude ratio is determined by the ratio of the equivalent total impedance of the live wire to the total impedance of the neutral wire, and the neutral-to-ground voltage drop on the neutral return path satisfies: This expression is the neutral loop voltage equation.

[0078] Specifically, the data processing unit is based on the neutral loop voltage equation. The voltage to ground is expressed as the product of the total neutral impedance and the zero-sequence current, and this relationship is introduced into the circuit constraint equations established in step S501. In the middle, by eliminating the zero-sequence current value , deduced This leads to the magnitude ratio between the zero-sequence voltage value and the voltage to ground value. This amplitude ratio is determined solely by the equivalent total impedance of the live wire. Total impedance of neutral line The ratio is determined by the magnitude of the three-phase load current and the degree of imbalance.

[0079] Step S503: Calculate the voltage to ground based on the amplitude ratio and the zero-sequence voltage value.

[0080] The data processing unit reads the zero-sequence voltage amplitude U_0n obtained in step S103 under the current power frequency cycle, and calls the amplitude ratio relationship K = determined in step S502. ,according to The calculation relationship is used to obtain the voltage amplitude of the load-side neutral point relative to the power supply-side neutral point under the current power frequency cycle. This allows for the online acquisition of the neutral-to-ground voltage.

[0081] In the specific embodiments of steps S501 to S503, by establishing circuit constraint equations between the zero-sequence voltage value, the voltage to ground value, the equivalent total impedance of the live wire, and the total impedance of the neutral wire, and by using the neutral wire loop voltage equation to eliminate the intermediate variable of the zero-sequence current value, an amplitude ratio relationship determined only by the ratio of the equivalent total impedance of the live wire to the total impedance of the neutral wire is derived. This ratio relationship is independent of the magnitude and degree of imbalance of the three-phase load current, so that the calculation of the voltage to ground does not need to rely on the load-side operating condition information, and can be directly obtained by measuring the zero-sequence voltage collected by the switch itself. The measurement result is not affected by load fluctuations, has high robustness and engineering practicality, and realizes non-intrusive online measurement of the neutral wire to ground voltage.

[0082] Reference Figure 7 As shown, Figure 7 This is provided by the embodiments of this application. Figure 6 An optional flowchart for step S501, the method may include, but is not limited to, steps S601 to S602.

[0083] Step S601: Based on Kirchhoff's voltage law, establish the first-loop voltage equation for the first phase conductor, the second-loop voltage equation for the second phase conductor, and the third-loop voltage equation for the third phase conductor.

[0084] Specifically, the data processing unit is based on Figure 4 The simplified equivalent model of the three-phase four-wire circuit shown uses Kirchhoff's voltage law to establish the loop voltage equations for each phase, specifically for the loops containing the first, second, and third phase conductors.

[0085] For the first phase conductor A, starting from the neutral point on the power supply side, through the first phase power supply potential... Equivalent total live wire impedance Voltage of the first phase conductor relative to the load-side neutral point to the load-side neutral point Then, by the voltage to ground Return to power supply side neutral point The circuit satisfies This is the voltage equation for the first loop. Similarly, for the second phase conductor B, the voltage equation for the second loop is established as follows: For the third phase conductor C, the voltage equation for the third loop is established as follows: .

[0086] Step S602: Based on the characteristic that the sum of the three-phase power supply potentials is zero under a three-phase four-wire circuit, the voltage equations of the first loop, the voltage equation of the second loop, and the voltage equation of the third loop are superimposed and summed to obtain the third correlation equation between the zero-sequence voltage value, the voltage value to ground, the equivalent total impedance of the live wire, and the total value of the three-phase current.

[0087] The total three-phase current is the sum of the first current value, the second current value, and the third current value.

[0088] Specifically, the data processing unit adds the equal sides of the first loop voltage equation, the second loop voltage equation, and the third loop voltage equation established in step S601, respectively, and obtains the sum of the three-phase power supply potentials on the left side of the equation. The right side of the equation yields ,in, ,Right now Equivalent to After sorting, we get .

[0089] Then, based on the characteristic that the sum of the potentials of the three-phase power supply is zero under the condition of a three-phase symmetrical power supply, = 0, and the zero-sequence voltage value of the above neutral line After sorting, we get This equation is the third correlation equation between the zero-sequence voltage, the voltage to ground, the equivalent total live wire impedance, and the total three-phase current. Step S603: Based on Kirchhoff's current law, determine the fourth correlation equation between the total value of the three-phase current and the value of the zero-sequence current.

[0090] Specifically, in Figure 4 In the three-phase four-wire circuit of the measuring switch shown, the neutral point on the load side... The current from the first phase conductor was collected at this location. Second phase conductor current Third phase conductor current and neutral zero-sequence current According to Kirchhoff's current law, current flows into this neutral point. The sum of the currents is zero, that is... After sorting, we get This equation is the fourth correlation equation.

[0091] Step S604: Determine the circuit constraint equations based on the fourth and third correlation equations.

[0092] In a specific embodiment of steps S601 to S604, the data processing unit processes the fourth correlation equation determined in step S603. Substitute the third correlation equation established in step S602 In the middle, the total value of the three-phase current is eliminated ( This intermediate variable is used to obtain... After simplification, it becomes the circuit constraint equation. The circuit constraint equations establish a quantitative relationship between the zero-sequence voltage, the voltage to ground, the equivalent total live wire impedance, and the zero-sequence current.

[0093] In specific embodiments of steps S601 to S604, the loop voltage equations for the three-phase conductors are established using Kirchhoff's voltage law. The sum of the three-phase power supply potentials under three-phase symmetrical power conditions is then superimposed and summed. Finally, Kirchhoff's current law is used to determine the relationship between the total three-phase current and the zero-sequence current value. This systematically derives the circuit constraint equations between the zero-sequence voltage, the voltage to ground, the equivalent total impedance of the live wire, and the zero-sequence current. This derivation process starts from fundamental circuit laws, gradually eliminating intermediate variables such as power supply potential and the total three-phase current. The resulting circuit constraint equations contain only directly measurable or solvable electrical quantities, laying a solid foundation for subsequently eliminating the zero-sequence current value and establishing a direct proportional relationship between the zero-sequence voltage and the voltage to ground, ensuring the rigor of the entire derivation process and the accuracy of the calculation results.

[0094] Furthermore, regarding the amplitude ratio relationship This amplitude ratio is determined solely by the equivalent total impedance of the live wire. Total impedance of neutral line The ratio determines the result and is independent of the magnitude and degree of imbalance of the three-phase load current. Please refer to [link / reference]. Figure 8 , Figure 8 This is an optional schematic diagram of a Simulink simulation model of a three-phase four-wire system provided in an embodiment of this application. This application is based on... Figure 8 The Simulink simulation model of the three-phase four-wire system shown was used for verification. In this simulation model, three different sets of live wire impedance and neutral wire impedance parameters were set, and the configuration of the three-phase load impedance was changed sequentially under each set of impedance parameters.

[0095] Under the first set of impedance parameters =0.177+1.048j (mΩ) Z N =0.647+2.208j (mΩ), theoretically calculated ratio ; Under the second set of impedance parameters, =5.015+3.565j (mΩ), ZN=22.324+8.323j (mΩ), theoretically calculated ratio ; Under the third set of impedance parameters =11.13+2.193j (mΩ), ZN=50.494+5.193j (mΩ), theoretically calculated ratio .

[0096] Under each set of fixed impedance parameters, the three-phase load impedance Z is respectively... A Z B Z C Multiple unbalanced load combinations were used, including (7Ω, 2Ω, 4Ω), (5Ω, 4Ω, 6Ω), (3Ω, 8Ω, 5Ω), (7Ω, 5Ω, 1Ω), and (10Ω, 2Ω, 8Ω), and the zero-sequence voltage amplitude on the load side was recorded. voltage amplitude of neutral point to ground The measured ratio. The simulation results are shown in Table 1. Table 1 Comparison of theoretical and simulated values ​​under different line parameters

[0097] Under all impedance parameters, even with significant changes in the three-phase load configuration, the measured ratio K consistently matched the theoretically calculated value, with the maximum deviation not exceeding the allowable engineering range. This fully verifies that the amplitude ratio K is determined solely by the equivalent total impedance of the live wires. Total impedance of neutral line Z NThe ratio is determined by the magnitude of the three-phase load and the degree of imbalance.

[0098] This application also provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the above-described method for measuring the neutral-to-ground voltage of a power grid measuring switch. This electronic device can be any smart terminal, including mobile phones, tablets, and in-vehicle computers.

[0099] Please see Figure 9 , Figure 9 This is a schematic diagram of an optional hardware structure of an electronic device provided in an embodiment of this application. The electronic device includes: The processor 901 can be implemented using a general-purpose CPU (Central Processing Unit), microprocessor, application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the neutral-to-ground voltage measurement method of the power grid measurement switch provided in this application embodiment. The memory 902 can be implemented as a read-only memory (ROM), static storage device, dynamic storage device, or random access memory (RAM). The memory 902 can store the operating system and other application programs. When the technical solutions provided in the embodiments of this specification are implemented through software or firmware, the relevant program code is stored in the memory 902 and is called and executed by the processor 901 to execute the neutral-to-ground voltage measurement method of the power grid measuring switch provided in the embodiments of this application. The input / output interface 903 is used to implement information input and output; The communication interface 904 is used to enable communication and interaction between this device and other devices. Communication can be achieved through wired means (such as USB, Ethernet cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.). Bus 905 transmits information between various components of the device (e.g., processor 901, memory 902, input / output interface 903, and communication interface 904); The processor 901, memory 902, input / output interface 903, and communication interface 904 are connected to each other within the device via bus 905.

[0100] This application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, provides a method for measuring the neutral line-to-ground voltage of a power grid measuring switch.

[0101] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory may optionally include memory remotely located relative to the processor, and these remote memories can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0102] The embodiments described in this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided by the embodiments of this application. As those skilled in the art will know, with the evolution of technology and the emergence of new application scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0103] Those skilled in the art will understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of this application, and may include more or fewer steps than shown, or combine certain steps, or different steps.

[0104] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0105] Those skilled in the art will understand that all or some of the steps in the methods disclosed above, as well as the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, or suitable combinations thereof.

[0106] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0107] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship equation of the related objects, indicating that three relationships can exist. For example, "A and / or B" can represent: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0108] In the embodiments provided in this application, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are merely illustrative; for instance, the division of the units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0109] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0110] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0111] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-accessible storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes multiple instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing programs, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0112] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the claims of the present application.

Claims

1. A method for measuring the neutral-to-ground voltage of a power grid measuring switch, characterized in that, The power grid measuring switch includes a first-phase conductor, a second-phase conductor, a third-phase conductor, and a neutral conductor connected in parallel. The method includes: Obtain the first current value and first voltage value of the first phase conductor, the second current value and second voltage value of the second phase conductor, and the third current value and third voltage value of the third phase conductor under the current power frequency cycle; The zero-sequence current value of the neutral line is determined based on the first current value, the second current value, and the third current value. The zero-sequence voltage value of the neutral line is determined based on the first voltage value, the second voltage value, and the third voltage value. When any one of the first current value, the second current value, or the third current value changes abruptly, the phase conductor in which the current changes abruptly, is identified as the abruptly changing phase conductor, and the changes in current, voltage, and zero-sequence current of the neutral line are determined before and after the abrupt change. Based on the zero-sequence current value, the zero-sequence voltage value, the current change, the voltage change, and the zero-sequence current change, calculate the total neutral impedance and the equivalent live wire total impedance of the measuring switch on the power supply side. The neutral line voltage to ground is determined based on the equivalent total impedance of the live wire, the total impedance of the neutral wire, and the zero-sequence voltage value.

2. The method for measuring neutral-to-ground voltage according to claim 1, characterized in that, The step of identifying the phase conductor with the sudden current change as the abruptly changing phase conductor when any one of the first current value, the second current value, or the third current value changes abruptly and the change exceeds a preset threshold includes: Obtain the fourth current value of the first phase conductor, the fifth current value of the second phase conductor, and the sixth current value of the second phase conductor under the previous power frequency cycle; If the vector difference between the first current value and the fourth current value is greater than the preset threshold, it is determined that the first current value has abruptly changed, and the corresponding first phase conductor is determined as the abruptly changed phase conductor. Alternatively, if the vector difference between the second current value and the fifth current value is greater than the preset threshold, then it is determined that the second current value has abruptly changed, and the corresponding second phase conductor is determined as the abruptly changed phase conductor; Alternatively, if the vector difference between the third current value and the sixth current value is greater than the preset threshold, then it is determined that the third current value has abruptly changed, and the corresponding third phase conductor is determined as the abruptly changed phase conductor. The preset threshold is 10% of the rated current of the measuring switch.

3. The method for measuring neutral-to-ground voltage according to claim 1, characterized in that, The step of calculating the total neutral impedance and equivalent live wire impedance of the measuring switch on the power supply side based on the zero-sequence current value, the zero-sequence voltage value, the current change, the voltage change, and the zero-sequence current change includes: Based on the loop voltage constraints of the abrupt phase conductor before and after the abrupt change, a first correlation equation is established between the current change, the voltage change, and the zero-sequence current change. Based on the circuit constraints between the zero-sequence voltage, zero-sequence current, and line impedance, a second correlation equation is established between the zero-sequence voltage value, the zero-sequence current value, the equivalent total live wire impedance, and the total neutral wire impedance. Based on the zero-sequence current value, the zero-sequence voltage value, the current change, the voltage change, and the zero-sequence current change, the first correlation equation and the second correlation equation are solved simultaneously to obtain the equivalent total live wire impedance and the total neutral wire impedance.

4. The method for measuring neutral-to-ground voltage according to claim 3, characterized in that, The step of establishing a first correlation equation between the current change, the voltage change, and the zero-sequence current change based on the loop voltage constraints of the abruptly changed phase conductor before and after the abrupt change includes: Based on the loop voltage constraints of the abrupt phase conductor before and after the abrupt change, the first abrupt voltage equation of the abrupt phase conductor at the moment before the abrupt change and the second abrupt voltage equation at the moment after the abrupt change are established respectively. Subtracting the first sudden voltage equation from the second sudden voltage equation yields the first correlation equation.

5. The method for measuring neutral-to-ground voltage according to claim 1, characterized in that, The step of determining the neutral-to-ground voltage value based on the equivalent total live wire impedance, the total neutral wire impedance, and the zero-sequence voltage value includes: Based on the three-phase four-wire circuit of the measuring switch, establish circuit constraint equations between the zero-sequence voltage value, the voltage to ground value, the equivalent total impedance of the live wire, and the total impedance of the neutral wire; Based on the neutral loop voltage equation between the total neutral impedance, the zero-sequence current value, and the voltage to ground value, as well as the circuit constraint equation, the amplitude ratio between the zero-sequence voltage value and the voltage to ground value is determined. The amplitude ratio is determined by the ratio of the equivalent total live wire impedance to the total neutral impedance. The voltage to ground is calculated based on the amplitude ratio and the zero-sequence voltage value.

6. The method for measuring neutral-to-ground voltage according to claim 5, characterized in that, The three-phase four-wire circuit based on the measuring switch establishes circuit constraint equations between the zero-sequence voltage value, the voltage to ground value, the equivalent total live wire impedance, and the total neutral wire impedance, including: Based on Kirchhoff's voltage law, the first loop voltage equation of the first phase conductor, the second loop voltage equation of the second phase conductor, and the third loop voltage equation of the third phase conductor are established. Based on the characteristic that the sum of the three-phase power supply potentials is zero under the three-phase four-wire circuit, the voltage equations of the first loop, the second loop, and the third loop are superimposed and summed to obtain a third correlation equation between the zero-sequence voltage value, the voltage value to ground, the equivalent total impedance of the live wire, and the total value of the three-phase current. The total value of the three-phase current is the sum of the first current value, the second current value, and the third current value. Based on Kirchhoff's current law, a fourth correlation equation is determined between the total value of the three-phase current and the value of the zero-sequence current. The circuit constraint equations are determined based on the fourth correlation equation and the third correlation equation.

7. The method for measuring neutral-to-ground voltage according to claim 1, characterized in that, Determining the zero-sequence current value of the neutral line based on the first current value, the second current value, and the third current value includes: The zero-sequence current value of the neutral line is obtained by performing a vector sum operation on the first current value, the second current value, and the third current value.

8. The method for measuring neutral-to-ground voltage according to claim 1, characterized in that, Determining the zero-sequence voltage value of the neutral line based on the first voltage value, the second voltage value, and the third voltage value includes: The zero-sequence voltage value of the neutral line is obtained by performing a vector sum operation on the first voltage value, the second voltage value, and the third voltage value.

9. An electronic device, characterized in that, The electronic device is provided with a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the neutral-to-ground voltage measurement method of the power grid measuring switch as described in any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a processor-executable program, which, when executed by a processor, constitutes the neutral-to-ground voltage measurement method of the power grid measuring switch as described in any one of claims 1 to 8.

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