Polarity judgment method, device and equipment for zero sequence current transformer of power transmission line

Abstract

The application relates to a method, device and equipment for judging the polarity of a zero sequence current transformer of a power transmission line. The method comprises: determining whether the three-phase power supply of the power transmission line is symmetrical by detecting the closing state of each phase power supply gate; if not, detecting a first actual zero sequence current of the zero sequence current transformer connected to the power transmission line in the current polarity and a second actual zero sequence current of the zero sequence current transformer connected to the power transmission line in the reverse polarity of the current polarity; and determining the current polarity of the zero sequence current transformer connected to the power transmission line according to the first actual zero sequence current, the second actual zero sequence current and a target theoretical zero sequence current. The above method can safely and efficiently judge the polarity of the zero sequence current transformer connected to the power transmission line.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric power, in particular to a polarity judgment method, device and equipment of a zero sequence current transformer of a power transmission line. BACKGROUND

[0002] With the development of the power system, electric power affects people's life in various aspects, so the safe operation of the power system is of great significance. The zero sequence current transformer is an important device in the power system. When a grounding fault occurs in the power system, the zero sequence current transformer can proportionally transform the large amplitude zero sequence current in the power system into a small amplitude zero sequence current, which is convenient for the secondary protection device to work.

[0003] However, the correct polarity connection of the zero sequence current transformer is necessary to ensure the correct measurement of the current on the line. Once the polarity of the zero sequence current transformer is reversed, the measured zero sequence current phase will be reversed, which will lead to incorrect judgment of the zero sequence power direction and greatly affect the safety of the power grid. Therefore, after the new line is put into operation, the polarity of the zero sequence current transformer needs to be tested.

[0004] Currently, people usually artificially cause a grounding fault to obtain a larger zero sequence current, so as to test the polarity of the zero sequence current transformer. However, this method will adversely affect the normal operation of the system and is dangerous. Therefore, how to safely and efficiently test the polarity of the zero sequence current transformer has become a problem to be solved. SUMMARY

[0005] Therefore, it is necessary to provide a polarity judgment method, device and equipment of a zero sequence current transformer of a power transmission line, which can safely and efficiently test the polarity of the zero sequence current transformer.

[0006] In a first aspect, the present application provides a polarity judgment method of a zero sequence current transformer of a power transmission line. The method comprises:

[0007] determining whether the three-phase power supply of the power transmission line is symmetrical by detecting the closing state of each phase power supply gate of the three-phase power supply of the power transmission line;

[0008] if not, detecting a first actual zero sequence current of the zero sequence current transformer connected to the power transmission line in the current polarity, and a second actual zero sequence current of the zero sequence current transformer connected to the power transmission line in the reverse polarity of the current polarity;

[0009] determining the current polarity of the zero-sequence current transformer connected to the power transmission line according to the first actual zero-sequence current, the second actual zero-sequence current and the target theoretical zero-sequence current; wherein the target theoretical zero-sequence current comprises a first theoretical zero-sequence current when the zero-sequence current transformer is connected to the power transmission line in a forward direction, and / or a second theoretical zero-sequence current when the zero-sequence current transformer is connected to the power transmission line in a reverse direction.

[0010] In one embodiment, the determination of whether the three-phase power of the power transmission line is symmetrical comprises:

[0011] If it is detected that two of the three-phase power supply gates of the power transmission line have been closed and the third-phase power supply gate has been opened, it is determined that the three-phase power of the power transmission line is not symmetrical.

[0012] In one embodiment, the determination of the current polarity of the zero-sequence current transformer connected to the power transmission line according to the first actual zero-sequence current, the second actual zero-sequence current and the target theoretical zero-sequence current comprises:

[0013] determining a first Fréchet distance between the first actual zero-sequence current and the target theoretical zero-sequence current;

[0014] determining a second Fréchet distance between the second actual zero-sequence current and the target theoretical zero-sequence current;

[0015] determining the current polarity of the zero-sequence current transformer connected to the power transmission line according to the way in which the zero-sequence current transformer corresponding to the target theoretical zero-sequence current is connected to the power transmission line, and the first Fréchet distance and the second Fréchet distance.

[0016] In one embodiment, the determination of the current polarity of the zero-sequence current transformer connected to the power transmission line according to the way in which the zero-sequence current transformer corresponding to the target theoretical zero-sequence current is connected to the power transmission line, and the first Fréchet distance and the second Fréchet distance comprises:

[0017] if the way in which the zero-sequence current transformer corresponding to the target theoretical zero-sequence current is connected to the power transmission line is forward connection, and the first Fréchet distance is smaller than the second Fréchet distance, it is determined that the polarity of the zero-sequence current transformer connected to the power transmission line is forward; and / or if the way in which the zero-sequence current transformer corresponding to the target theoretical zero-sequence current is connected to the power transmission line is reverse connection, and the second Fréchet distance is smaller than the first Fréchet distance, it is determined that the polarity of the zero-sequence current transformer connected to the power transmission line is forward.

[0018] In one embodiment, the determination of the current polarity of the zero-sequence current transformer connected to the power transmission line according to the first actual zero-sequence current, the second actual zero-sequence current and the target theoretical zero-sequence current comprises:

[0019] performing time discretization processing on the target theoretical zero-sequence current according to the sampling frequencies of the first actual zero-sequence current and the second actual zero-sequence current to obtain a processed target theoretical zero-sequence current;

[0020] The current polarity of the zero-sequence current transformer connected to the transmission line is determined according to the first actual zero-sequence current, the second actual zero-sequence current and the processed target theoretical zero-sequence current.

[0021] In one embodiment, the method further comprises:

[0022] Determining the closing time of each phase power switch of a three-phase power supply of a transmission line, wherein the closing time of any phase power switch is later than the closing time of the other two phase power switches;

[0023] Control the power switches of each phase of the three-phase power supply and close them according to the corresponding closing time.

[0024] In a second aspect, the present application also provides a device for determining the polarity of a zero-sequence current transformer of a transmission line. The device comprises:

[0025] A symmetry judgment module is used to determine whether the three-phase power of the transmission line is symmetrical by detecting the closing status of each phase power switch of the three-phase power supply of the transmission line;

[0026] a current detection module, configured to detect a first actual zero-sequence current when the zero-sequence current transformer is connected to the transmission line with a current polarity, and a second actual zero-sequence current when the zero-sequence current transformer is connected to the transmission line with a polarity reverse to the current polarity;

[0027] A polarity judgment module is used to determine the current polarity of the zero-sequence current transformer connected to the transmission line based on the first actual zero-sequence current, the second actual zero-sequence current and the target theoretical zero-sequence current; wherein the target theoretical zero-sequence current includes the first theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the forward direction, and / or the second theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the reverse direction.

[0028] In a third aspect, the present application further provides a computer device. The computer device includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, the following steps are performed:

[0029] By detecting the closing status of each phase power switch of the three-phase power supply of the transmission line, it is determined whether the three-phase power of the transmission line is symmetrical;

[0030] If it is asymmetric, detecting a first actual zero-sequence current of the zero-sequence current transformer connected to the transmission line with a current polarity, and a second actual zero-sequence current of the zero-sequence current transformer connected to the transmission line with a reverse polarity of the current polarity;

[0031] The current polarity of the zero-sequence current transformer connected to the transmission line is determined based on the first actual zero-sequence current, the second actual zero-sequence current and the target theoretical zero-sequence current; wherein the target theoretical zero-sequence current includes the first theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the forward direction, and / or the second theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the reverse direction.

[0032] In a fourth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the following steps:

[0033] By detecting the closing status of each phase power switch of the three-phase power supply of the transmission line, it is determined whether the three-phase power of the transmission line is symmetrical;

[0034] If it is asymmetric, detecting a first actual zero-sequence current of the zero-sequence current transformer connected to the transmission line with a current polarity, and a second actual zero-sequence current of the zero-sequence current transformer connected to the transmission line with a reverse polarity of the current polarity;

[0035] The current polarity of the zero-sequence current transformer connected to the transmission line is determined based on the first actual zero-sequence current, the second actual zero-sequence current and the target theoretical zero-sequence current; wherein the target theoretical zero-sequence current includes the first theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the forward direction, and / or the second theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the reverse direction.

[0036] In a fifth aspect, the present application further provides a computer program product. The computer program product includes a computer program that, when executed by a processor, implements the following steps:

[0037] By detecting the closing status of each phase power switch of the three-phase power supply of the transmission line, it is determined whether the three-phase power of the transmission line is symmetrical;

[0038] If it is asymmetric, detecting a first actual zero-sequence current of the zero-sequence current transformer connected to the transmission line with a current polarity, and a second actual zero-sequence current of the zero-sequence current transformer connected to the transmission line with a reverse polarity of the current polarity;

[0039] The current polarity of the zero-sequence current transformer connected to the transmission line is determined based on the first actual zero-sequence current, the second actual zero-sequence current and the target theoretical zero-sequence current; wherein the target theoretical zero-sequence current includes the first theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the forward direction, and / or the second theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the reverse direction.

[0040] The aforementioned method, device, and apparatus for determining the polarity of a zero-sequence current transformer for a transmission line compare the actual detected zero-sequence current with the calculated theoretical zero-sequence current based on the closing conditions of the three-phase power supply to determine the polarity of the zero-sequence current transformer. This method is simple to operate, does not adversely affect the normal operation of the power system, and can safely and efficiently determine the polarity of the zero-sequence current transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 FIG2 is an application environment diagram of a method for determining the polarity of a zero-sequence current transformer of a transmission line in one embodiment;

[0042] Figure 2 1 is a flow chart of a method for determining the polarity of a zero-sequence current transformer of a transmission line in one embodiment;

[0043] Figure 3 A schematic diagram of a zero-sequence network closing process analysis for a transmission line in one embodiment;

[0044] Figure 4 A schematic diagram of a process for determining the current polarity of a zero-sequence current transformer connected to a transmission line in one embodiment;

[0045] Figure 5 A schematic diagram of a process for determining the current polarity of a zero-sequence current transformer connected to a transmission line in another embodiment;

[0046] Figure 6 A schematic diagram of a process for determining asymmetry of a three-phase power supply in one embodiment;

[0047] Figure 7 1 is a flow chart of a method for determining the polarity of a zero-sequence current transformer of a transmission line in another embodiment;

[0048] Figure 8 1 is a structural block diagram of a device for determining the polarity of a zero-sequence current transformer of a transmission line in one embodiment;

[0049] Figure 9 is a structural block diagram of a polarity determination device for a zero-sequence current transformer of a transmission line in another embodiment;

[0050] Figure 10 is a structural block diagram of a polarity determination device for a zero-sequence current transformer of a transmission line in yet another embodiment;

[0051] Figure 11 is a structural block diagram of a polarity determination device for a zero-sequence current transformer of a transmission line in yet another embodiment;

[0052] Figure 12 FIG. 1 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0053] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0054] The method for judging polarity of a zero sequence current transformer of a power transmission line provided by the embodiments of the present application can be applied in an application environment as shown in Figure 1 In an embodiment, a computer device is provided, which can be a server, and an internal structure diagram of the computer device can be as shown in Figure 1 The computer device includes a processor, a memory and a network interface connected through a system bus. The processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for running of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is configured to store data required for processing of alarm data. The network interface of the computer device is configured to communicate with an external terminal through a network connection. The computer program is executed by the processor to implement the method for judging polarity of a zero sequence current transformer of a power transmission line shown in any of the embodiments described below.

[0055] In an embodiment, as shown in Figure 2 A method for judging polarity of a zero sequence current transformer of a power transmission line is provided, which will be described by taking the computer device in Figure 1 as an example, and includes the following steps.

[0056] S201, it is determined whether three-phase power of a power transmission line is symmetrical by detecting closing conditions of each phase power switch of the three-phase power.

[0057] In the embodiment, the power of the line to be detected is a three-phase power, and each phase of the three-phase power corresponds to a power switch. Only when the three power switches of the three-phase power are closed, the three-phase power supplies power to the power transmission line. When the three power switches of the three-phase power are closed, the three-phase power of the power transmission line is in a symmetrical state. When any two power switches of the three-phase power are closed and the third power switch is open, it is determined that the three-phase power of the power transmission line is in an asymmetrical state.

[0058] Optionally, when it is necessary to judge the polarity of the zero-sequence current transformer of the transmission line, the power switches of two phases of the three-phase power supply can be manually closed, and the power switch of the third phase power supply can be temporarily not closed. At this time, the server detects the closing status of the power switches of the three-phase power supply in the transmission line, and it can be found that two phases of the three-phase power supply are in the closed state and the other phase is in the disconnected state. At this time, it can be determined that the three-phase power of the transmission line is asymmetric.

[0059] S202 , detecting a first actual zero-sequence current when the zero-sequence current transformer is connected to the transmission line with a current polarity, and a second actual zero-sequence current when the zero-sequence current transformer is connected to the transmission line with a polarity reverse to the current polarity.

[0060] The first actual zero-sequence current is the current in the transmission line when the zero-sequence current transformer is connected to the transmission line with the current polarity; the second actual zero-sequence current is the current in the transmission line when the zero-sequence current transformer is connected to the transmission line with the reverse polarity of the current polarity.

[0061] Alternatively, a current detection device may be connected to a load end of a transmission line. A zero-sequence current transformer may be connected to the transmission line with its current polarity. The current detected by the current detection device may be sampled as a first actual zero-sequence current. The zero-sequence current transformer may then be connected to the transmission line with its polarity reversed from the current polarity. The current detected by the current detection device may be sampled as a second actual zero-sequence current. The current detection device may be an ammeter.

[0062] S203 : Determine the current polarity of the zero-sequence current transformer connected to the transmission line according to the first actual zero-sequence current, the second actual zero-sequence current, and the target theoretical zero-sequence current.

[0063] The target theoretical zero-sequence current includes a first theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the forward direction, and / or a second theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the reverse direction. The target theoretical zero-sequence current can be obtained by analyzing the circuit schematic diagram after the zero-sequence current transformer is connected to the transmission line.

[0064] Specifically, such as Figure 3 As shown, the zero-sequence network closing process of the transmission line can be analyzed. The zero-sequence voltage U0 and the zero-sequence parameters of the line are known quantities, and the zero-sequence current I0 is an unknown quantity. The zero-sequence voltage, zero-sequence current and the zero-sequence parameters of the line satisfy the following differential equation (1):

[0065]

[0066] Among them, U0 is the zero-sequence voltage, I0 is the zero-sequence current, C0 is the capacitance, L0 is the inductance, R0 is the resistance, and I is the current on the resistor R0.

[0067] Assuming that the closing phase angle of U0 is φ, that is, U0 = k·cos(ω·t+φ), substituting it into the above formula (1) to solve the zero-sequence current I0, the following formulas (2)-(8) are obtained:

[0068] I0=I m ·sin(ω·t+φ-φ1)+I k .e -αt cos(ω1·t+φ2) (2)

[0069]

[0070]

[0071] Among them, I m is the amplitude of the steady-state signal, I k is the amplitude of the transient signal, α is the attenuation factor of the transient signal, ω is the angular velocity of the signal, ω1 is the angular velocity of the transient signal, U0 is the zero-sequence voltage, I0 is the zero-sequence current, φ is the closing phase angle, φ1 is the first closing phase angle in the closing process, φ2 is the second phase closing angle in the closing process, C0 is the capacitance, L0 is the inductance, and R0 is the resistance.

[0072] Optionally, the amplitude of the transient signal when the zero-sequence current transformer is connected in the forward direction, the closing phase angle, and the angular velocity of the transient signal are substituted into the above formulas (2)-(8) to obtain the first theoretical zero-sequence current; the amplitude of the transient signal when the zero-sequence current transformer is connected in the reverse direction, the closing phase angle, and the angular velocity of the transient signal are substituted into the above formulas (2)-(8) to obtain the second theoretical zero-sequence current.

[0073] Optionally, the current polarity of the zero-sequence current transformer in the transmission line is determined according to the measured first actual zero-sequence current and the second actual zero-sequence current and the calculated first actual zero-sequence current and the second actual zero-sequence current.

[0074] Specifically, the similarities between the first actual zero-sequence current and the second actual zero-sequence current and between each other are calculated, and the current polarity of the zero-sequence current transformer in the transmission line is determined according to the values ​​of the four similarities.

[0075] In the above embodiment, when the three-phase power in the transmission line is asymmetrical, the actual zero-sequence current of the transmission line is detected, and the theoretical zero-sequence current of the transmission line is calculated. Based on the actual zero-sequence current and the theoretical zero-sequence current, the current polarity of the zero-sequence current transformer connected to the transmission line is determined. This method not only efficiently detects the current polarity of the zero-sequence current transformer, but also avoids safety accidents during the detection process that could affect the normal operation of the power grid.

[0076] Based on the above embodiments, Figure 4 As shown, this embodiment further elaborates on the determination of the polarity of the zero-sequence current transformer. According to the first actual zero-sequence current, the second actual zero-sequence current, and the target theoretical zero-sequence current, the current polarity of the zero-sequence current transformer connected to the transmission line is determined, including:

[0077] S401 : Determine a first Fréchet distance between a first actual zero-sequence current and a target theoretical zero-sequence current.

[0078] Among them, the Fréchet distance is a numerical value that characterizes the similarity between two models. The smaller the value, the higher the similarity between the two models. In this embodiment, it can be used to characterize the similarity between the actual zero-sequence current and the theoretical zero-sequence current; the target theoretical zero-sequence current can be the first theoretical zero-sequence current and / or the second theoretical zero-sequence current.

[0079] For example, if the target theoretical zero-sequence current is taken as the first theoretical zero-sequence current, the first actual zero-sequence current curve L with m sampling points is a = <p a1 ,p a2 ,…,p am > and the first theoretical zero-sequence current curve L with m sampling points b = b1 ,q b2 ,…,q bm > Combine to get sequence L:

[0080] L=<(p a1 ,q b1 ), (p a2 ,q b2 ), (p am ,q bm )>

[0081] The Fréchet distance between the first actual zero-sequence current curve and the first theoretical zero-sequence current curve is calculated according to the sequence L. The calculation method is shown in the following formulas (9) and (10):

[0082]

[0083] F(L a ,L b )=min||L|| (10)

[0084] Among them, F(L a ,L b ) is the Fréchet distance between the two curves. ||L|| is L a and L b The length between the two, L a is the first actual zero-sequence current curve, L​b is a first theoretical zero sequence current curve, and d() is a function formula of a calculation length value.

[0085] Optionally, the Fréchet distance between the first actual zero sequence current curve and the first theoretical zero sequence current curve is a first Fréchet distance.

[0086] S402, a second Fréchet distance between the second actual zero sequence current and a target theoretical zero sequence current is determined.

[0087] The target theoretical zero sequence current needs to be consistent with the target theoretical zero sequence current in S401, and both are the first theoretical zero sequence current.

[0088] Optionally, the Fréchet distance between the second actual zero sequence current curve and the first theoretical zero sequence current curve is obtained as the second Fréchet distance by using a method similar to S401.

[0089] S403, a current polarity of the zero sequence current transformer accessing the power transmission line is determined according to a way in which the zero sequence current transformer corresponding to the target theoretical zero sequence current accesses the power transmission line, and the first Fréchet distance and the second Fréchet distance.

[0090] If the way in which the zero sequence current transformer corresponding to the target theoretical zero sequence current accesses the power transmission line is positive access, and the first Fréchet distance is less than the second Fréchet distance, it is determined that the polarity of the zero sequence current transformer accessing the power transmission line is positive; and / or if the way in which the zero sequence current transformer corresponding to the target theoretical zero sequence current accesses the power transmission line is negative access, and the second Fréchet distance is less than the first Fréchet distance, it is determined that the polarity of the zero sequence current transformer accessing the power transmission line is positive.

[0091] For example, in the embodiment, the target theoretical zero sequence current is the first theoretical zero sequence current, and the access way of the zero sequence current transformer corresponding to the first theoretical zero sequence current is positive. If the first Fréchet distance is less than the second Fréchet distance, that is, the Fréchet distance between the first actual zero sequence current curve and the first theoretical zero sequence current curve is less than the Fréchet distance between the second actual zero sequence current curve and the first theoretical zero sequence current curve, according to the definition of the Fréchet distance, it can be known that the similarity between the first actual zero sequence current curve and the first theoretical zero sequence current curve is higher than the similarity between the second actual zero sequence current curve and the first theoretical zero sequence current curve, at this time, it is determined that the polarity of the zero sequence current transformer accessing the circuit is positive, otherwise, if the first Fréchet distance is greater than the second Fréchet distance, it is determined that the polarity of the zero sequence current transformer accessing the circuit is negative.

[0092] Optionally, if the target theoretical zero sequence current is the second theoretical zero sequence current, and it is known that the second theoretical zero sequence current corresponds to the reverse connection mode of the zero sequence current transformer. At this time, if the first Fréchet distance is greater than the second Fréchet distance, that is, the Fréchet distance between the first actual zero sequence current curve and the second theoretical zero sequence current curve is greater than the Fréchet distance between the second actual zero sequence current curve and the second theoretical zero sequence current curve, according to the definition of the Fréchet distance, it can be known that the similarity between the second actual zero sequence current curve and the second theoretical zero sequence current curve is higher than the similarity between the first actual zero sequence current curve and the second theoretical zero sequence current curve. At this time, it is determined that the polarity of the zero sequence current transformer connection circuit is positive, otherwise, if the first Fréchet distance is less than the second Fréchet distance, it is determined that the polarity of the zero sequence current transformer connection circuit is reverse

[0093] In the embodiment, the first Fréchet distance between the first actual zero sequence current and the target theoretical zero sequence current and the second Fréchet distance between the second actual zero sequence current and the target theoretical zero sequence current are calculated, and the first Fréchet distance and the second Fréchet distance are compared to determine the connection mode of the zero sequence current transformer. This method only needs to calculate and compare the distances through an algorithm, without human intervention, greatly improving the accuracy and efficiency of the polarity determination of the zero sequence current transformer.

[0094] On the basis of the above-mentioned embodiments, as shown in Figure 5 Before calculating the Fréchet distance, how to preprocess the collected data is described, so that the current polarity of the zero sequence current transformer connected to the power transmission line is determined according to the first actual zero sequence current, the second actual zero sequence current and the target theoretical zero sequence current, and further comprises:

[0095] S501, according to the sampling frequency of the first actual zero sequence current and the second actual zero sequence current, time-discretizing the target theoretical zero sequence current to obtain the processed target theoretical zero sequence current.

[0096] For example, when sampling the actual zero sequence current, the sampling data of the three-phase unbalanced period (such as the first 10 ms) is usually recorded. Since the zero sequence current is a gradually decaying sinusoidal current, the amplitude becomes smaller and the data becomes less accurate as time goes on. Therefore, we only take the sample data of the preset period (such as the first 5 ms) as the final actual zero sequence current. The target theoretical zero sequence current is usually in units of s. In order to facilitate the calculation of the Fréchet distance between the actual zero sequence current and the target theoretical zero sequence current, we need to perform time-discretization processing on the target theoretical zero sequence current, and take the target theoretical zero sequence current value of the first 5 ms as the processed target theoretical zero sequence current.

[0097] S502, determining the current polarity of the zero-sequence current transformer connected to the power transmission line according to the first actual zero-sequence current, the second actual zero-sequence current and the processed target theoretical zero-sequence current.

[0098] Optionally, a first Fréchet distance between the first actual zero-sequence current and the processed target theoretical zero-sequence current is calculated, a second Fréchet distance between the second actual zero-sequence current and the processed target theoretical zero-sequence current is calculated, and the current polarity of the zero-sequence current transformer connected to the power transmission line is determined according to the relationship between the first Fréchet distance and the second Fréchet distance.

[0099] The above embodiment ensures that the sampling frequency of the actual zero-sequence current is the same as that of the target theoretical zero-sequence current by discretizing the target theoretical zero-sequence current, greatly increases the convenience of Fréchet distance calculation, and finally increases the efficiency of the polarity determination of the zero-sequence current transformer.

[0100] Based on the above embodiment, as shown in the following Figure 6 The embodiment illustrates how to determine the three-phase power supply asymmetry of the power transmission line, and the method comprises the following steps:

[0101] S601, determining the closing time of each phase power supply breaker of the three-phase power supply of the power transmission line.

[0102] In which, the closing time of any one phase power supply breaker is later than the closing time of the other two phase power supply breakers.

[0103] For example, it can be determined that the closing time of two phase power supplies in the three-phase power supply is equal, and the closing time of the other phase power supply is 10 ms later than the closing time of the other two phase power supply breakers.

[0104] S602, controlling each phase power supply breaker of the three-phase power supply to close according to the corresponding closing time.

[0105] Optionally, the two phase power supplies in the three-phase power supply with equal closing time are first controlled to close, and the other phase power supply is controlled to close 10 ms later.

[0106] It should be noted that, in the process of controlling the respective phase power switches of the three-phase power supply to close according to the corresponding closing times, since the closing time of one phase power switch is later than that of the other two phase power switches, in the stage where two of the power switches are closed and the third phase power switch is not closed, the server detects the three-phase asymmetry of the power transmission line, at this time, the first actual zero sequence current of the zero sequence current transformer connected to the power transmission line in the current polarity and the second actual zero sequence current of the zero sequence current transformer connected to the power transmission line in the reverse polarity of the current polarity are detected; according to the first actual zero sequence current, the second actual zero sequence current and the target theoretical zero sequence current, the current polarity of the zero sequence current transformer connected to the power transmission line is determined. Thus, the polarity of the zero sequence current transformer of the power transmission line is determined online, which does not affect the normal operation of the power transmission line. The convenience of judging the polarity of the zero sequence current transformer is increased.

[0107] In order to more comprehensively show the present scheme, the present embodiment gives an optional way of the polarity judgment method of the zero sequence current transformer of the power transmission line, as shown in Figure 7

[0108] S701, the closing times of the respective phase power switches of the three-phase power supply of the power transmission line are determined.

[0109] Among them, the closing time of any one phase power switch is later than that of the other two phase power switches.

[0110] S702, in the process of controlling the respective phase power switches of the three-phase power supply to close according to the corresponding closing times, the first actual zero sequence current of the zero sequence current transformer connected to the power transmission line in the current polarity and the second actual zero sequence current of the zero sequence current transformer connected to the power transmission line in the reverse polarity of the current polarity are detected.

[0111] S703, according to the sampling frequency of the first actual zero sequence current and the second actual zero sequence current, the target theoretical zero sequence current is time-discretized to obtain the processed target theoretical zero sequence current.

[0112] S704, the first Fréchet distance between the first actual zero sequence current and the processed target theoretical zero sequence current is determined.

[0113] S705, the second Fréchet distance between the second actual zero sequence current and the processed target theoretical zero sequence current is determined.

[0114] S706, according to the first actual zero sequence current, the second actual zero sequence current and the processed target theoretical zero sequence current, the current polarity of the zero sequence current transformer connected to the power transmission line is determined.

[0115] ​The specific process of the above S701-S706 can be found in the description of the above method embodiment. The implementation principle and technical effects are similar and will not be repeated here.

[0116] It should be understood that, although the steps in the flowcharts of the above embodiments are shown in sequence as indicated by the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be performed in other orders. Moreover, at least a portion of the steps in the flowcharts of the above embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily performed at the same time, but can be performed at different times. The execution order of these steps or stages is not necessarily to be performed in sequence, but can be performed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0117] Based on the same inventive concept, an embodiment of the present application further provides a device for determining the polarity of a zero-sequence current transformer for a transmission line, which is used to implement the aforementioned method for determining the polarity of a zero-sequence current transformer for a transmission line. The solution provided by this device is similar to the solution described in the aforementioned method. Therefore, the specific limitations of the embodiments of the device for determining the polarity of one or more zero-sequence current transformers for transmission lines provided below can be found in the aforementioned method for determining the polarity of a zero-sequence current transformer for transmission lines, and will not be repeated here.

[0118] In one embodiment, Figure 8 As shown, a polarity judgment device for a zero-sequence current transformer of a transmission line is provided, comprising: a symmetry judgment module 80, a current detection module 81 and a polarity judgment module 82, wherein:

[0119] A symmetry determination module 80 is used to determine whether the three-phase power of the transmission line is symmetrical by detecting the closing status of the power switches of each phase of the three-phase power supply of the transmission line;

[0120] a current detection module 81 for detecting a first actual zero-sequence current when the zero-sequence current transformer is connected to the transmission line with a current polarity, and a second actual zero-sequence current when the zero-sequence current transformer is connected to the transmission line with a polarity reverse to the current polarity;

[0121] The polarity judgment module 82 is used to determine the current polarity of the zero-sequence current transformer connected to the transmission line based on the first actual zero-sequence current, the second actual zero-sequence current and the target theoretical zero-sequence current; wherein the target theoretical zero-sequence current includes the first theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the forward direction, and / or the second theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the reverse direction.

[0122] In another embodiment, the symmetry judgment module 80 in the above Figure 8 is further configured to:

[0123] If it is detected that two-phase power supply gates of the three-phase power supply of the power transmission line are closed and the third-phase power supply gate is open, it is determined that the three-phase power of the power transmission line is asymmetric.

[0124] In another embodiment, as shown in the above Figure 9 , the polarity judgment module 82 in the above Figure 8 further includes:

[0125] The first determination unit 820 is configured to determine a first Fréchet distance between the first actual zero-sequence current and the target theoretical zero-sequence current.

[0126] The second determination unit 821 is configured to determine a second Fréchet distance between the second actual zero-sequence current and the target theoretical zero-sequence current.

[0127] The first judgment unit 822 is configured to determine the current polarity of the zero-sequence current transformer connected to the power transmission line according to the connection mode of the zero-sequence current transformer corresponding to the target theoretical zero-sequence current to the power transmission line, and the first Fréchet distance and the second Fréchet distance.

[0128] In another embodiment, the polarity judgment unit 822 in the above Figure 9 is further configured to:

[0129] If the connection mode of the zero-sequence current transformer corresponding to the target theoretical zero-sequence current to the power transmission line is forward connection, and the first Fréchet distance is less than the second Fréchet distance, it is determined that the polarity of the zero-sequence current transformer connected to the power transmission line is forward; and / or if the connection mode of the zero-sequence current transformer corresponding to the target theoretical zero-sequence current to the power transmission line is reverse connection, and the second Fréchet distance is less than the first Fréchet distance, it is determined that the polarity of the zero-sequence current transformer connected to the power transmission line is forward.

[0130] In another embodiment, as shown in the above Figure 10 , the polarity judgment module 82 in the above Figure 8 further includes:

[0131] The discrete processing unit 823 is configured to perform time discretization processing on the target theoretical zero-sequence current according to the sampling frequencies of the first actual zero-sequence current and the second actual zero-sequence current, to obtain a processed target theoretical zero-sequence current.

[0132] The second judgment unit 824 is configured to determine the current polarity of the zero-sequence current transformer connected to the power transmission line according to the first actual zero-sequence current, the second actual zero-sequence current, and the processed target theoretical zero-sequence current.

[0133] In another embodiment, Figure 11 As shown above Figure 8 The polarity judgment device 8 of the zero-sequence current transformer of the transmission line further includes:

[0134] The time determination module 83 is used to determine the closing time of each phase power switch of the three-phase power supply of the transmission line.

[0135] The closing time of any one phase power switch is later than the closing time of the other two phase power switches.

[0136] The power closing module 84 is used to control the power switches of each phase of the three-phase power supply and close the power according to the corresponding closing time.

[0137] Each module in the aforementioned device for determining the polarity of a zero-sequence current transformer for a transmission line can be implemented in whole or in part via software, hardware, or a combination thereof. Each module can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in the computer device in the form of software, so that the processor can call and execute the corresponding operations of each module.

[0138] In one embodiment, a computer device is provided. The computer device may be a terminal, and its internal structure diagram may be as follows: Figure 12 As shown. The computer device includes a processor, a memory, an input / output interface, a communication interface, a display unit and an input device. The processor, the memory and the input / output interface are connected via a system bus, and the communication interface, the display unit and the input device are connected to the system bus via the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, a mobile cellular network, NFC (near field communication) or other technologies. When the computer program is executed by the processor, a method for determining the polarity of a zero-sequence current transformer of a transmission line is implemented. The display unit of the computer device is used to form a visually visible picture, which can be a display screen, a projection device or a virtual reality imaging device. The display screen can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covering the display screen, or a button, trackball or touchpad set on the computer device casing, or an external keyboard, touchpad or mouse.

[0139] Those skilled in the art will understand that Figure 12 The structure shown in the figure is only a block diagram of part of the structure related to the scheme of the present application, and does not constitute a limitation on the computer device to which the scheme of the present application is applied. The specific computer device can include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0140] In one embodiment, a computer device is provided, comprising a memory and a processor, the memory storing a computer program, and the processor implementing the following steps when executing the computer program:

[0141] By detecting the closing of each phase power switch of the three-phase power supply of the power transmission line, it is determined whether the three-phase power of the power transmission line is symmetrical;

[0142] If not, a zero sequence current transformer is detected to have a first actual zero sequence current connected to the power transmission line in a current polarity, and a second actual zero sequence current connected to the power transmission line in a reverse polarity of the current polarity;

[0143] According to the first actual zero sequence current, the second actual zero sequence current and a target theoretical zero sequence current, the current polarity of the zero sequence current transformer connected to the power transmission line is determined; wherein the target theoretical zero sequence current includes a first theoretical zero sequence current when the zero sequence current transformer is connected to the power transmission line in a forward direction, and / or a second theoretical zero sequence current when the zero sequence current transformer is connected to the power transmission line in a reverse direction.

[0144] In one embodiment, the processor further implements the following steps when executing the computer program:

[0145] If it is detected that two phase power switches of the three-phase power supply of the power transmission line have been closed and the third phase power switch has been opened, it is determined that the three-phase power of the power transmission line is not symmetrical.

[0146] In one embodiment, the processor further implements the following steps when executing the computer program:

[0147] A first Fréchet distance between the first actual zero sequence current and the target theoretical zero sequence current is determined;

[0148] A second Fréchet distance between the second actual zero sequence current and the target theoretical zero sequence current is determined;

[0149] According to the way in which the zero sequence current transformer corresponding to the target theoretical zero sequence current is connected to the power transmission line, and the first Fréchet distance and the second Fréchet distance, the current polarity of the zero sequence current transformer connected to the power transmission line is determined.

[0150] In one embodiment, the processor further implements the following steps when executing the computer program:

[0151] If the zero-sequence current transformer is connected to the power transmission line in a forward manner, and the first Fréchet distance is smaller than the second Fréchet distance, it is determined that the polarity of the zero-sequence current transformer connected to the power transmission line is forward; and / or if the zero-sequence current transformer is connected to the power transmission line in a reverse manner, and the second Fréchet distance is smaller than the first Fréchet distance, it is determined that the polarity of the zero-sequence current transformer connected to the power transmission line is forward.

[0152] In one embodiment, the processor, when executing the computer program, also implements the following steps:

[0153] According to the sampling frequencies of the first actual zero-sequence current and the second actual zero-sequence current, the target theoretical zero-sequence current is time-discretized to obtain a processed target theoretical zero-sequence current;

[0154] According to the first actual zero-sequence current, the second actual zero-sequence current, and the processed target theoretical zero-sequence current, the current polarity of the zero-sequence current transformer connected to the power transmission line is determined.

[0155] In one embodiment, the processor, when executing the computer program, also implements the following steps:

[0156] The closing times of the three-phase power supply gates of the three-phase power supply of the power transmission line are determined, wherein the closing time of any one-phase power supply gate is later than the closing times of the other two-phase power supply gates;

[0157] The three-phase power supply gates of the three-phase power supply of the power transmission line are controlled to close according to the corresponding closing times.

[0158] In one embodiment, a computer-readable storage medium is provided, which stores a computer program. When the computer program is executed by a processor, the following steps are implemented:

[0159] By detecting the closing conditions of the three-phase power supply gates of the three-phase power supply of the power transmission line, it is determined whether the three-phase power of the power transmission line is symmetrical;

[0160] If not, the first actual zero-sequence current of the zero-sequence current transformer connected to the power transmission line in the current polarity is detected, and the second actual zero-sequence current of the zero-sequence current transformer connected to the power transmission line in the reverse polarity of the current polarity is detected;

[0161] According to the first actual zero-sequence current, the second actual zero-sequence current, and the target theoretical zero-sequence current, the current polarity of the zero-sequence current transformer connected to the power transmission line is determined. The target theoretical zero-sequence current includes a first theoretical zero-sequence current when the zero-sequence current transformer is connected to the power transmission line in a forward manner, and / or a second theoretical zero-sequence current when the zero-sequence current transformer is connected to the power transmission line in a reverse manner.

[0162] In one embodiment, the computer program, when executed by the processor, also implements the following steps:

[0163] If it is detected that two phase power switches of the three-phase power supply of the transmission line are closed and the third phase power switch is open, it is determined that the three phases of the transmission line are asymmetric.

[0164] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0165] determining a first Fréchet distance between a first actual zero-sequence current and a target theoretical zero-sequence current;

[0166] determining a second Fréchet distance between a second actual zero-sequence current and a target theoretical zero-sequence current;

[0167] The current polarity of the zero-sequence current transformer connected to the transmission line is determined according to the way the zero-sequence current transformer is connected to the transmission line corresponding to the target theoretical zero-sequence current, as well as the first Fréchet distance and the second Fréchet distance.

[0168] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0169] If the zero-sequence current transformer corresponding to the target theoretical zero-sequence current is connected to the transmission line in a forward direction, and the first Fréchet distance is smaller than the second Fréchet distance, then the polarity of the zero-sequence current transformer connected to the transmission line is determined to be forward; and / or if the zero-sequence current transformer corresponding to the target theoretical zero-sequence current is connected to the transmission line in a reverse direction, and the second Fréchet distance is smaller than the first Fréchet distance, then the polarity of the zero-sequence current transformer connected to the transmission line is determined to be reverse.

[0170] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0171] performing time discretization processing on the target theoretical zero-sequence current according to the sampling frequencies of the first actual zero-sequence current and the second actual zero-sequence current to obtain a processed target theoretical zero-sequence current;

[0172] The current polarity of the zero-sequence current transformer connected to the transmission line is determined according to the first actual zero-sequence current, the second actual zero-sequence current and the processed target theoretical zero-sequence current.

[0173] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0174] Determining the closing time of each phase power switch of a three-phase power supply of a transmission line, wherein the closing time of any phase power switch is later than the closing time of the other two phase power switches;

[0175] Control the power switches of each phase of the three-phase power supply and close them according to the corresponding closing time.

[0176] In one embodiment, a computer program product is provided, comprising a computer program, which, when executed by a processor, implements the following steps:

[0177] By detecting the closing status of each phase power switch of the three-phase power supply of the transmission line, it is determined whether the three-phase power of the transmission line is symmetrical;

[0178] If it is asymmetric, detecting a first actual zero-sequence current of the zero-sequence current transformer connected to the transmission line with a current polarity, and a second actual zero-sequence current of the zero-sequence current transformer connected to the transmission line with a reverse polarity of the current polarity;

[0179] The current polarity of the zero-sequence current transformer connected to the transmission line is determined based on the first actual zero-sequence current, the second actual zero-sequence current and the target theoretical zero-sequence current; wherein the target theoretical zero-sequence current includes the first theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the forward direction, and / or the second theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the reverse direction.

[0180] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0181] If it is detected that two phase power switches of the three-phase power supply of the transmission line are closed and the third phase power switch is open, it is determined that the three phases of the transmission line are asymmetric.

[0182] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0183] determining a first Fréchet distance between a first actual zero-sequence current and a target theoretical zero-sequence current;

[0184] determining a second Fréchet distance between a second actual zero-sequence current and a target theoretical zero-sequence current;

[0185] The current polarity of the zero-sequence current transformer connected to the transmission line is determined according to the way the zero-sequence current transformer is connected to the transmission line corresponding to the target theoretical zero-sequence current, as well as the first Fréchet distance and the second Fréchet distance.

[0186] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0187] If the zero-sequence current transformer corresponding to the target theoretical zero-sequence current is connected to the transmission line in a forward direction, and the first Fréchet distance is smaller than the second Fréchet distance, then the polarity of the zero-sequence current transformer connected to the transmission line is determined to be forward; and / or if the zero-sequence current transformer corresponding to the target theoretical zero-sequence current is connected to the transmission line in a reverse direction, and the second Fréchet distance is smaller than the first Fréchet distance, then the polarity of the zero-sequence current transformer connected to the transmission line is determined to be forward.

[0188] In one embodiment, the computer program which is executed by the processor further implements the following steps:

[0189] According to the sampling frequencies of the first actual zero sequence current and the second actual zero sequence current, the target theoretical zero sequence current is time-discretized to obtain a processed target theoretical zero sequence current;

[0190] According to the first actual zero sequence current, the second actual zero sequence current and the processed target theoretical zero sequence current, the current polarity of the zero sequence current transformer accessing the power transmission line is determined.

[0191] In one embodiment, the computer program which is executed by the processor further implements the following steps:

[0192] The closing times of the phase power breakers of the three-phase power supply of the power transmission line are determined, wherein the closing time of any one phase power breaker is later than the closing times of the other two phase power breakers;

[0193] The phase power breakers of the three-phase power supply are controlled to be closed according to the corresponding closing times.

[0194] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processor involved in the various embodiments provided herein may be, but are not limited to, a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, and the like.

[0195] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0196] The above embodiments merely illustrate several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A method for determining the polarity of a zero-sequence current transformer of a transmission line, characterized in that: The method comprises: Determining whether the three-phase power of the transmission line is symmetrical by detecting the closing status of each phase power switch of the three-phase power supply of the transmission line; If it is asymmetric, detecting a first actual zero-sequence current of the zero-sequence current transformer connected to the transmission line with a current polarity, and a second actual zero-sequence current of the zero-sequence current transformer connected to the transmission line with a reverse polarity of the current polarity; The current polarity of the zero-sequence current transformer when connected to the transmission line is determined based on the first actual zero-sequence current, the second actual zero-sequence current and the target theoretical zero-sequence current; wherein the target theoretical zero-sequence current includes the first theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the forward direction, and / or the second theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the reverse direction.

2. The method according to claim 1, characterized in that The method of determining whether the three-phase power of the transmission line is symmetrical by detecting the closing status of each phase power switch of the three-phase power supply of the transmission line includes: If it is detected that two phase power switches of the three-phase power supply of the transmission line are closed and the third phase power switch is open, it is determined that the three phases of the transmission line are asymmetric.

3. The method according to claim 1, characterized in that The determining, based on the first actual zero-sequence current, the second actual zero-sequence current, and the target theoretical zero-sequence current, of the current polarity of the zero-sequence current transformer connected to the transmission line includes: determining a first Fréchet distance between the first actual zero-sequence current and the target theoretical zero-sequence current; determining a second Fréchet distance between the second actual zero-sequence current and the target theoretical zero-sequence current; The current polarity of the zero-sequence current transformer connected to the transmission line is determined according to the mode in which the zero-sequence current transformer corresponding to the target theoretical zero-sequence current is connected to the transmission line, as well as the first Fréchet distance and the second Fréchet distance.

4. The method according to claim 3, characterized in that Determining a current polarity of the zero-sequence current transformer connected to the transmission line according to a mode in which the zero-sequence current transformer corresponding to the target theoretical zero-sequence current is connected to the transmission line, as well as the first Fréchet distance and the second Fréchet distance, includes: If the zero-sequence current transformer corresponding to the target theoretical zero-sequence current is connected to the transmission line in a forward direction, and the first Fréchet distance is smaller than the second Fréchet distance, then the polarity of the zero-sequence current transformer connected to the transmission line is determined to be forward; and / or if the zero-sequence current transformer corresponding to the target theoretical zero-sequence current is connected to the transmission line in a reverse direction, and the second Fréchet distance is smaller than the first Fréchet distance, then the polarity of the zero-sequence current transformer connected to the transmission line is determined to be forward.

5. The method according to claim 1, wherein The determining, based on the first actual zero-sequence current, the second actual zero-sequence current, and the target theoretical zero-sequence current, of the current polarity of the zero-sequence current transformer connected to the transmission line includes: performing time discretization processing on the target theoretical zero-sequence current according to the sampling frequencies of the first actual zero-sequence current and the second actual zero-sequence current to obtain a processed target theoretical zero-sequence current; The current polarity of the zero-sequence current transformer connected to the transmission line is determined according to the first actual zero-sequence current, the second actual zero-sequence current and the processed target theoretical zero-sequence current.

6. The method according to any one of claims 1 to 5, characterized in that The method further comprises: Determining the closing time of each phase power switch of a three-phase power supply of a transmission line, wherein the closing time of any phase power switch is later than the closing time of the other two phase power switches; Control each phase power switch of the three-phase power supply and close the switch according to the corresponding closing time.

7. A polarity determination device for a zero-sequence current transformer of a transmission line, characterized in that: The device comprises: A symmetry judgment module is used to determine whether the three-phase power of the transmission line is symmetrical by detecting the closing status of each phase power switch of the three-phase power supply of the transmission line; a current detection module, configured to detect a first actual zero-sequence current when a zero-sequence current transformer is connected to the transmission line with a current polarity, and a second actual zero-sequence current when the zero-sequence current transformer is connected to the transmission line with a polarity reverse to the current polarity; A polarity judgment module is used to determine the current polarity of the zero-sequence current transformer when it is connected to the transmission line based on the first actual zero-sequence current, the second actual zero-sequence current and the target theoretical zero-sequence current; wherein the target theoretical zero-sequence current includes the first theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the forward direction, and / or the second theoretical zero-sequence current when the zero-sequence current transformer is connected to the transmission line in the reverse direction.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

10. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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