An overhead transmission line breakage fault identification method and system

Abstract

The application discloses an overhead transmission line breakage fault identification method and system, and the method comprises the following steps: acquiring three-phase voltage instantaneous values and three-phase current instantaneous values after a transmission line fault; performing Fourier decomposition on the three-phase voltage instantaneous values and the three-phase current instantaneous values to acquire three-phase voltage amplitudes, three-phase current amplitudes and three-phase voltage current angles; calculating three-phase active power P φ , three-phase reactive power Q φ and zero sequence current I0 based on the three-phase voltage amplitudes, the three-phase current amplitudes and the three-phase voltage current angles; calculating three-phase active power changes based on the three-phase active power P φ ; judging the three-phase active power changes at different time points to acquire three-phase judgment coefficients; performing sliding window integration on the three-phase judgment coefficients and the zero sequence current I0 to acquire three-phase integral values and zero sequence current integral values dI0; and identifying the fault of the transmission line based on a threshold value K1 of the three-phase integral values, a threshold value K2 of the three-phase reactive power Q φ and a threshold value K3 of the zero sequence current integral values dI0.

Description

Technical Field

[0001] The present invention relates to the technical field of transmission line disconnection fault identification, and more specifically, to a method and system for identifying an overhead transmission line disconnection fault. Background Art

[0002] Due to the combined impacts of global warming and other factors, extreme disasters are becoming increasingly common, posing severe challenges to the safe operation of power grids. During the winter of 2023-2024, five cold snaps resulted in ice coating on over 3,300 transmission lines above 110 kV and ice swaying on over 1,300 lines. Six simultaneous outages of ultra-high voltage AC double-circuit lines were also reported. During each cold snap, approximately 70% of line trips above 500 kV occurred within 48 hours, with each event rapidly affecting one or more severely affected localized areas. This resulted in significant grid damage, isolated grids, localized load shedding, and even complete outages in small areas. When faced with line outages and grid failures caused by natural disasters like icing, the inability to quickly analyze the cause of the fault severely impacts troubleshooting and power restoration, negatively impacting the reliability and resilience of the power grid. Currently, accurate identification of the cause and nature of high-voltage line faults is not yet possible, and there is a lack of methods for identifying line outages based on electrical quantity analysis.

[0003] In current grid operations and dispatch decisions, when a line is broken and causes a fault, operations and maintenance personnel primarily rely on on-site inspections to determine if a line break has occurred. However, in the face of rain, snow, freezing weather, or other extreme weather conditions, poor inspection conditions and low visibility often make it difficult to quickly determine the cause of the fault. This significantly prolongs repairs and power restoration, creating inconvenience for dispatch and maintenance decisions and increasing the economic losses caused by power outages. Furthermore, if reclosing or forced power transmission is performed without identifying the cause of the fault, the system will experience two short-circuit current surges in a short period of time, severely impacting the grid's power supply reliability.

[0004] Prior art 1 (application name: Line break identification method based on data prediction) includes: calling the basic data of the transmission line including external environmental data and internal state data, predicting the comprehensive failure probability of each transmission line when iced and the total ice load of each transmission line, so as to determine the probability of line break for each line. However, prior art 1 requires additional collection of basic data of various parts of the transmission line, including the load of each tower, the load of adjacent towers, operating environment parameters, etc. For long-distance transmission lines such as ultra-high voltage and ultra-high voltage, the amount of data and information that needs to be collected is huge. In order to accurately obtain tower-related information, each tower needs to be equipped with an information collection device, which increases the investment cost. At the same time, a loop traversal method is used to calculate the line break probability of each section of the transmission line. The calculation amount is large and it is easily affected by cumulative errors, resulting in reduced calculation accuracy. In addition, this similar technology can only be used to predict the line break probability before the fault occurs. When a permanent fault occurs in the transmission line, it is impossible to identify whether a line break fault has occurred.

[0005] Prior art 2 (application name: Transmission line disconnection fault identification method based on signal quantity transmission) includes: based on the three-phase voltage and three-phase current of the transmission line, by judging whether there is a phase with no current or a phase with capacitive current (i.e. whether the current phase is 90° ahead of the voltage phase) on both sides of the line, if it is satisfied, then the phase is identified as a disconnected phase. However, prior art 2 identifies the disconnected phase by considering whether there is no current or whether it is a capacitive current in a certain phase. However, when the transmission line is in no-load operation, the current flowing through the line is mainly capacitive current. The disconnection identification method of prior art 2 may be mistakenly judged as a three-phase disconnection, which is difficult to meet the accuracy requirements of identification.

[0006] Therefore, there is an urgent need to develop a method for identifying transmission line disconnection faults, improve the accuracy and speed of identifying the causes and nature of line faults, provide dispatching and operation personnel with disconnection fault identification results in a short time, and ensure the safe supply of electricity. Summary of the Invention

[0007] The technical solution of the present invention provides a method and system for identifying an overhead transmission line disconnection fault to solve the problem of how to identify an overhead transmission line disconnection fault based on fault recording data of the three-phase voltage and three-phase current of the transmission line.

[0008] In order to solve the above problems, the present invention provides a method for identifying a disconnection fault of an overhead transmission line, the method comprising:

[0009] Get the instantaneous value U of the three-phase voltage after the transmission line fault A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C ;

[0010] The instantaneous value of the three-phase voltage U A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C Perform Fourier decomposition to obtain the three-phase voltage amplitude U MA 、U MB 、U MC , three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C ;

[0011] Based on the three-phase voltage amplitude U MA 、U MB 、U MC , the three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate the three-phase active power P φ , three-phase reactive power Q φ and zero sequence current I0;

[0012] Based on the three-phase active power P φ , calculate the three-phase active power change P AB 、P BC 、P CA ;

[0013] The three-phase active power changes P at different times AB 、P BC 、P CA Make a judgment and obtain the three-phase judgment coefficient k PA 、k PB 、k PC ;

[0014] The three-phase judgment coefficient k PA 、k PB 、k PC And the zero-sequence current I0 is integrated by sliding window to obtain the three-phase integral value dk PA 、dk PB 、dk PC And the zero-sequence current integral value dI0;

[0015] Based on the threshold value K1 and three-phase reactive power Q of the obtained three-phase integral valueφ The threshold value K2 of the zero-sequence current integral value dI0 and the threshold value K3 of the zero-sequence current integral value dI0 are used to identify the fault of the transmission line.

[0016] Preferably, the three-phase voltage amplitude U MA 、U MB 、U MC , the three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate the three-phase active power P φ , three-phase reactive power Q φ and zero-sequence current I0, including:

[0017]

[0018] Where φ is phase A, B, and C; t is time; P φ (t) is the three-phase active power at time t; Q φ (t) is the three-phase reactive power at time t; U Mφ (t) is the three-phase voltage amplitude at time t; I Mφ (t) is the amplitude of the three-phase current at time t; θ φ (t) is the angle between the three-phase voltage and current at time t; I0(t) is the zero-sequence current at time t; I A (t), I B (t), I C (t) are the instantaneous current values ​​of phase A, phase B and phase C at time t respectively.

[0019] Preferably, the three-phase active power P φ , calculate the three-phase active power change P AB 、P BC 、P CA ,include:

[0020]

[0021] Among them, P AB (t), P BC (t), P CA (t) are the active power changes of phase A, phase B and phase C at time t.

[0022] Preferably, the three-phase active power change P at different times AB 、P BC 、P CA Make a judgment and obtain the three-phase judgment coefficient k PA 、k PB 、kPC ,include:

[0023]

[0024] Among them, k PA (t), k PB (t) and k PC (t) are the judgment systems of phase A, phase B and phase C at time t. If the judgment conditions are met, then the current time t otherwise

[0025] Preferably, the three-phase judgment coefficient k PA 、k PB 、k PC And the zero-sequence current I0 is integrated by sliding window to obtain the three-phase integral value dk PA 、dk PB 、dk PC And the zero-sequence current integral value dI0; the threshold value K1 based on the obtained three-phase integral value, the three-phase reactive power Q φ The threshold value K2 of the zero-sequence current integral value dI0 and the threshold value K3 of the zero-sequence current integral value dI0 are used to identify the fault of the transmission line, including:

[0026] The three-phase judgment coefficient, k PB 、k PC And zero sequence current I0 are integrated by sliding window, the integration time window is T1, and the phase integral value dk is calculated respectively. PA 、dk PB 、dk PC And the zero-sequence current integral value dI0:

[0027]

[0028] Where, I0(t) is the zero-sequence current at time t;

[0029] Take the three-phase integral value The threshold value is K1, three-phase reactive power The threshold of the zero-sequence current integral value dI0 is K2, and the threshold of the zero-sequence current integral value dI0 is K3. It is judged whether each phase in the line meets the following line break identification criteria:

[0030]

[0031] When it is determined that there is a phase that meets the transmission line trunk identification criterion during a continuous preset time period, the phase that meets the transmission line trunk identification criterion is determined to be a broken phase.

[0032] According to another aspect of the present invention, a system for identifying a disconnection fault of an overhead transmission line is provided, the system comprising:

[0033] The first acquisition unit is used to obtain the instantaneous value U of the three-phase voltage after the transmission line fails. A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C ;

[0034] The second acquisition unit is used to obtain the instantaneous value U of the three-phase voltage A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C Perform Fourier decomposition to obtain the three-phase voltage amplitude U MA 、U MB 、U MC , three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C ;

[0035] The first calculation unit is used to calculate the three-phase voltage amplitude U MA 、U MB 、U MC , the three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate the three-phase active power P φ , three-phase reactive power Q φ and zero sequence current I0;

[0036] The second calculation unit is used to calculate the three-phase active power P based on the φ , calculate the three-phase active power change P AB 、P BC 、P CA ;

[0037] The result unit is used to calculate the three-phase active power changes P at different times. AB 、P BC 、P CA Make a judgment and obtain the three-phase judgment coefficient k PA 、k PB 、k PC ; The three-phase judgment coefficient k PA 、kPB 、k PC And the zero-sequence current I0 is integrated by sliding window to obtain the three-phase integral value dk PA 、dk PB 、dk PC And the zero-sequence current integral value dI0; based on the threshold value K1 of the obtained three-phase integral value, the three-phase reactive power Q φ The threshold value K2 of the zero-sequence current integral value dI0 and the threshold value K3 of the zero-sequence current integral value dI0 are used to identify the fault of the transmission line.

[0038] Preferably, the second acquisition unit is used to obtain the voltage based on the three-phase voltage amplitude U MA 、U MB 、U MC , the three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate the three-phase active power P φ , three-phase reactive power Q φ and zero sequence current I0, and is also used for:

[0039]

[0040] Where φ is phase A, B, and C; t is time; P φ (t) is the three-phase active power at time t; Q φ (t) is the three-phase reactive power at time t; U Mφ (t) is the three-phase voltage amplitude at time t; I Mφ (t) is the amplitude of the three-phase current at time t; θ φ (t) is the angle between the three-phase voltage and current at time t; I0(t) is the zero-sequence current at time t; I A (t), I B (t), I C (t) are the instantaneous current values ​​of phase A, phase B and phase C at time t respectively.

[0041] Preferably, the second calculation unit is used to calculate the three-phase active power P φ , calculate the three-phase active power change P AB 、P BC 、P CA , also used for:

[0042]

[0043] Among them, P AB (t), P BC (t), P CA(t) are the active power changes of phase A, phase B and phase C at time t.

[0044] Preferably, the result unit is used to calculate the three-phase active power change P at different times. AB 、P BC 、P CA Make a judgment and obtain the three-phase judgment coefficient k PA 、k PB 、k PC , also used for:

[0045]

[0046] Among them, k PA (t), k PB (t) and k PC (t) are the judgment systems of phase A, phase B and phase C at time t. If the judgment conditions are met, then the current time t otherwise

[0047] Preferably, the result unit is used to calculate the three-phase judgment coefficient k PA 、k PB 、k PC And the zero-sequence current I0 is integrated by sliding window to obtain the three-phase integral value dk PA 、dk PB 、dk PC And the zero-sequence current integral value dI0; the threshold value K1 based on the obtained three-phase integral value, the three-phase reactive power Q φ The threshold value K2 of the zero-sequence current integral value dI0 and the threshold value K3 of the zero-sequence current integral value dI0 are used to identify the fault of the transmission line and are also used to:

[0048] The three-phase judgment coefficient, k PB 、k PC And zero sequence current I0 are integrated by sliding window, the integration time window is T1, and the phase integral value dk is calculated respectively. PA 、dk PB 、dk PC And the zero-sequence current integral value dI0:

[0049]

[0050] Where, I0(t) is the zero-sequence current at time t;

[0051] Take the three-phase integral value The threshold value is K1, three-phase reactive power The threshold of the zero-sequence current integral value dI0 is K2, and the threshold of the zero-sequence current integral value dI0 is K3. It is judged whether each phase in the line meets the following line break identification criteria:

[0052]

[0053] When it is determined that there is a phase that meets the transmission line trunk identification criterion during a continuous preset time period, the phase that meets the transmission line trunk identification criterion is determined to be a broken phase.

[0054] The technical solution of the present invention provides a method and system for identifying a broken line fault in an overhead transmission line, wherein the method comprises: obtaining the instantaneous value U of the three-phase voltage after the transmission line fault A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C ; For the instantaneous value of three-phase voltage U A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C Perform Fourier decomposition to obtain the three-phase voltage amplitude U MA 、U MB 、U MC , three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C ; Based on the three-phase voltage amplitude U MA 、U MB 、U MC , three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate the three-phase active power P φ , three-phase reactive power Q φ and zero-sequence current I0; based on three-phase active power P φ , calculate the three-phase active power change P AB 、P BC 、P CA ; Changes in three-phase active power P at different times AB 、P BC 、P CA Make a judgment and obtain the three-phase judgment coefficient k PA 、k PB 、k PC ; For the three-phase judgment coefficient k PA 、k PB 、kPC And the zero-sequence current I0 is integrated by sliding window to obtain the three-phase integral value dk PA 、dk PB 、dk PC And the zero-sequence current integral value dI0; based on the threshold value K1 of the obtained three-phase integral value, the three-phase reactive power Q φ The threshold value K2 of the zero-sequence current integral value dI0 and the threshold value K3 of the zero-sequence current integral value dI0 are used to identify the fault of the transmission line. The technical solution of the present invention proposes a method and criterion for identifying the fault of the transmission line break, which can quickly and accurately identify the line break based on the fault recording data of the three-phase voltage and three-phase current of the transmission line. When faced with natural disasters such as rain, snow and ice that make it difficult for operation and maintenance personnel to patrol the line, the technical solution of the present invention can use the transmission line break identification method proposed by the present invention to quickly and accurately determine whether the line is broken, thereby providing dispatching and operation and maintenance personnel with quick decision-making and reducing economic losses caused by power outages. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0056] Figure 1 Flowchart of a method for identifying a broken line fault of an overhead transmission line according to a preferred embodiment of the present invention;

[0057] Figure 2 A schematic diagram of a topological structure of a power transmission line according to a preferred embodiment of the present invention;

[0058] Figure 3 Flowchart of a method for identifying a power transmission line disconnection fault according to a preferred embodiment of the present invention;

[0059] Figure 4 A logic diagram for identifying a power transmission line disconnection fault according to a preferred embodiment of the present invention; and

[0060] Figure 5 The figure is a structural diagram of an overhead transmission line disconnection fault identification system according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0061] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to provide a thorough and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments shown in the accompanying drawings is not intended to limit the present invention. In the accompanying drawings, identical elements are denoted by the same reference numerals.

[0062] Unless otherwise specified, the terms used herein (including technical terms) have the meanings commonly understood by those skilled in the art. In addition, it is understood that terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0063] Figure 1 The figure is a flow chart of a method for identifying a broken line fault of an overhead transmission line according to a preferred embodiment of the present invention.

[0064] The present invention relates to a method and criterion for identifying overhead transmission line disconnection faults, which are used to identify transmission line disconnection faults and provide support for scheduling operations and fault analysis in extreme disaster scenarios, and belongs to the technical field of transmission line disconnection fault identification.

[0065] The present invention provides a method and criterion for identifying a power transmission line disconnection fault, which can quickly and accurately identify a line disconnection based on fault recording data of three-phase voltage and three-phase current of the power transmission line.

[0066] When faced with natural disasters such as rain, snow, and ice that make it difficult for operation and maintenance personnel to patrol the lines, the transmission line break identification method proposed in the present invention can be used to quickly and accurately determine whether the line is broken, thereby providing dispatching and operation and maintenance personnel with quick decision-making and reducing economic losses caused by power outages.

[0067] The present invention analyzes the changes in active power, reactive power, and zero-sequence current after a transmission line fault, thereby effectively identifying a transmission line disconnection fault. The following describes a detailed description of the transmission line disconnection fault identification method.

[0068] The present invention analyzes the characteristics of AC transmission line disconnection faults, such as Figure 2 The figure shows the topological structure of the transmission line. The positive direction of the line current is when the protection installation is pointing towards the line.

[0069] Taking the case of a phase A disconnection in a line as an example, we analyze the fault characteristics after the line is disconnected. Assuming that the three phases of the line are operating symmetrically before the fault, the zero-sequence current can be obtained as:

[0070]

[0071] When phase A of the line is disconnected, the fault boundary condition at the disconnection point is:

[0072]

[0073] Where, is the current of phase A after line break, is the voltage change of phase B and phase C at the disconnection point.

[0074] According to formula (1), when a line fault occurs, the fault phase current Close to 0, at this time:

[0075]

[0076] According to formula (3), after a line fault occurs, the zero-sequence current

[0077] At the same time, according to the boundary condition formula (2), when a line fault occurs, the broken phase presents the characteristic of "voltage without current". At this time, the active power of the broken phase decreases to nearly 0, and the reactive power is approximately equal to the reactive power generated by the distributed capacitance of the line.

[0078] The present invention provides a method for identifying a power transmission line disconnection fault. The present invention proposes a method and criteria for identifying a power transmission line disconnection based on changes in zero-sequence current, active power, and reactive power, as follows:

[0079] like Figure 1 As shown, the present invention provides a method for identifying a broken line fault in an overhead transmission line, the method comprising:

[0080] Step 101: Obtain the instantaneous value U of the three-phase voltage after the transmission line fault A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C ;

[0081] The present invention first reads the instantaneous values ​​U of the three-phase voltage and three-phase current after the transmission line fails. A 、U B 、U C , I A , I B , I C ;

[0082] Step 102: The instantaneous value of the three-phase voltage U A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C Perform Fourier decomposition to obtain the three-phase voltage amplitude U MA 、U MB 、U MC , three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C;

[0083] The present invention performs Fourier decomposition on the instantaneous values ​​of three-phase voltage and current to obtain the three-phase voltage amplitude U MA 、U MB 、U MC And the three-phase current amplitude I MA , I MB , I MC and the angle θ between the three-phase voltage and current A ,θ B ,θ C .

[0084] Step 103: Based on the three-phase voltage amplitude U MA 、U MB 、U MC , three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate the three-phase active power P φ , three-phase reactive power Q φ and zero sequence current I0;

[0085] Preferably, based on the three-phase voltage amplitude U MA 、U MB 、U MC , three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate the three-phase active power P φ , three-phase reactive power Q φ and zero-sequence current I0, including:

[0086]

[0087] Where φ is phase A, B, and C; t is time; P φ (t) is the three-phase active power at time t; Q φ (t) is the three-phase reactive power at time t; U Mφ (t) is the three-phase voltage amplitude at time t; I Mφ (t) is the amplitude of the three-phase current at time t; θ φ (t) is the angle between the three-phase voltage and current at time t; I0(t) is the zero-sequence current at time t; I A (t), I B (t), I C (t) are the instantaneous current values ​​of phase A, phase B and phase C at time t respectively.

[0088] The present invention calculates the three-phase active power P according to formula (4): φ , three-phase reactive power Q φ And zero sequence current I0:

[0089]

[0090] Where φ is phase A, B, and C; t is time.

[0091] Step 104: Based on the three-phase active power P φ , calculate the three-phase active power change P AB 、P BC 、P CA ;

[0092] Preferably, based on the three-phase active power P φ , calculate the three-phase active power change P AB 、P BC 、P CA ,include:

[0093]

[0094] Among them, P AB (t), P BC (t), P CA (t) are the active power changes of phase A, phase B and phase C at time t.

[0095] The present invention calculates the change of active power of three phases A, B and C:

[0096]

[0097] According to formula (5), when the three phases of the line are balanced, P AB 、P BC 、P CA Close to 0; when a phase A disconnection fault occurs, P AB =P B 、P BC =P BC 、P CA =P C .

[0098] Step 105: Changes in three-phase active power P at different times AB 、P BC 、P CA Make a judgment and obtain the three-phase judgment coefficient k PA 、k PB 、k PC ;

[0099] Preferably, the three-phase active power changes P at different times AB 、P BC 、P CA Make a judgment and obtain the three-phase judgment coefficient k PA 、k PB 、k PC ,include:

[0100]

[0101] Among them, k PA (t), k PB (t) and k PC (t) are the judgment systems of phase A, phase B and phase C at time t. If the judgment conditions are met, then the current time t otherwise

[0102] The present invention judges the change of three-phase active power according to formula (6):

[0103]

[0104] In the formula, if the judgment condition is met, then the current moment otherwise

[0105] Step 106: Three-phase judgment coefficient k PA 、k PB 、k PC And the zero-sequence current I0 is integrated by sliding window to obtain the three-phase integral value dk PA 、dk PB 、dk PC And the zero-sequence current integral value dI0;

[0106] Step 107: Based on the threshold value K1 of the acquired three-phase integral value and the three-phase reactive power Q φ The threshold value K2 of the zero-sequence current integral value dI0 and the threshold value K3 of the zero-sequence current integral value dI0 are used to identify the fault of the transmission line.

[0107] Preferably, the three-phase judgment coefficient k PA 、k PB 、k PC And the zero-sequence current I0 is integrated by sliding window to obtain the three-phase integral value dk PA 、dk PB 、dk PC And the zero-sequence current integral value dI0; based on the threshold value K1 of the obtained three-phase integral value, the three-phase reactive power Q φ The threshold value K2 of the zero-sequence current integral value dI0 and the threshold value K3 of the zero-sequence current integral value dI0 are used to identify the fault of the transmission line, including:

[0108] For the three-phase judgment coefficient, k PB 、k PC The sliding window integration is performed with the zero-sequence current I0, and the integration time window length is T1. The phase integral value dk is calculated respectively. PA 、dk PB 、dk PC And the zero-sequence current integral value dI0:

[0109]

[0110] Where, I0(t) is the zero-sequence current at time t;

[0111] Take the three-phase integral value The threshold value is K1, three-phase reactive power The threshold of the zero-sequence current integral value dI0 is K2, and the threshold of the zero-sequence current integral value dI0 is K3. It is judged whether each phase in the line meets the following line break identification criteria:

[0112]

[0113] When it is determined that there is a phase that meets the transmission line trunk identification criterion during a continuous preset time period, the phase that meets the transmission line trunk identification criterion is determined to be a broken phase.

[0114] The present invention is to PA 、k PB 、k PC Perform sliding window integration with zero-sequence current I0, with the integration time window length being T1, and calculate dk PA 、dk PB 、dk PC and dI0:

[0115]

[0116] The present invention provides a line disconnection fault identification criterion, including:

[0117] Pick The threshold value is K1, reactive power The threshold of the zero-sequence current integral dI0 is K2, and the threshold of the zero-sequence current integral dI0 is K3. According to the calculation results of formula (7), the line break identification criterion is constructed as follows:

[0118]

[0119] According to the calculation result of formula (7), if the continuous T2ms meets the line disconnection identification criterion of formula (8), then the phase is a disconnected phase.

[0120] The overall identification process of the present invention is as follows Figure 3 shown.

[0121] First, in step A, we theoretically analyzed the changes in active power, reactive power, and zero-sequence current during a transmission line disconnection. After a disconnection, the active power of the phase in question drops to zero, the reactive power is approximately equal to the reactive power generated by the distributed capacitance of the line, and the zero-sequence current is not zero.

[0122] Subsequently, in step B, the power changes between different phases are analyzed. The changes in the three-phase active power at each moment after the fault are measured according to formulas (6) and (7). The line disconnection identification criterion given by formula (8) is further combined to confirm the disconnected phase. Based on the PSCAD / EMTDC electromagnetic transient simulation platform, a transmission line disconnection fault simulation model was built to verify the transmission line disconnection identification method proposed in the present invention. The results show that the transmission line disconnection identification method proposed in the present invention has a high recognition accuracy rate and can meet the needs of auxiliary dispatching and operation and maintenance personnel to quickly and accurately determine whether a disconnection fault has occurred after a line fault occurs.

[0123] The present invention proposes a method for identifying a transmission line disconnection fault, which performs Fourier decomposition on the voltage and current fault recording data after the line fault and calculates the changes in active power, reactive power and zero-sequence current, and uses a comprehensive criterion to determine whether a line disconnection fault has occurred.

[0124] The present invention proposes a method for identifying a transmission line disconnection fault, but is not limited to the specific expression writing method and parameter values ​​given in the present invention using a specific voltage level as an example. For transmission lines of other voltage levels, the transmission line disconnection identification method of the present invention should also be regarded as within the scope of protection of the present invention.

[0125] Figure 5 The figure is a structural diagram of an overhead transmission line disconnection fault identification system according to a preferred embodiment of the present invention.

[0126] like Figure 5 As shown, the present invention provides an overhead transmission line disconnection fault identification system, the system comprising:

[0127] The first acquisition unit 501 is used to obtain the instantaneous value U of the three-phase voltage after the transmission line fails. A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C ;

[0128] The second acquisition unit 502 is used to obtain the instantaneous value U of the three-phase voltage A 、U B 、U C And the instantaneous value of three-phase current I A , I B , IC Perform Fourier decomposition to obtain the three-phase voltage amplitude U MA 、U MB 、U MC , three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C ;

[0129] Preferably, the second acquiring unit 502 is configured to obtain the voltage of the three-phase voltage based on the amplitude U MA 、U MB 、U MC , three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate three-phase active power Three-phase reactive power Q φ and zero sequence current I0, and is also used for:

[0130]

[0131] Where φ is phase A, B, and C; t is time; P φ (t) is the three-phase active power at time t; Q φ (t) is the three-phase reactive power at time t; U Mφ (t) is the three-phase voltage amplitude at time t; I Mφ (t) is the amplitude of the three-phase current at time t; θ φ (t) is the angle between the three-phase voltage and current at time t; I0(t) is the zero-sequence current at time t; I A (t), I B (t), I C (t) are the instantaneous current values ​​of phase A, phase B and phase C at time t respectively.

[0132] The first calculation unit 503 is used to calculate the three-phase voltage amplitude U MA 、U MB 、U MC , three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate the three-phase active power P φ , three-phase reactive power Q φ and zero sequence current I0;

[0133] The second calculation unit 504 is used to calculate the three-phase active power P φ , calculate the three-phase active power change P AB 、P BC 、P CA ;

[0134] Preferably, the second calculation unit 504 is configured to calculate the three-phase active power P φ , calculate the three-phase active power change P AB 、P BC 、P CA , also used for:

[0135]

[0136] Among them, P AB (t), P BC (t), P CA (t) are the active power changes of phase A, phase B and phase C at time t.

[0137] The result unit 505 is used to calculate the three-phase active power changes P at different times. AB 、P BC 、P CA Make a judgment and obtain the three-phase judgment coefficient k PA 、k PB 、k PC ; For the three-phase judgment coefficient k PA 、k PB 、k PC And the zero-sequence current I0 is integrated by sliding window to obtain the three-phase integral value dk PA 、dk PB 、dk PC And the zero-sequence current integral value dI0; based on the threshold value K1 of the obtained three-phase integral value, the three-phase reactive power Q φ The threshold value K2 of the zero-sequence current integral value dI0 and the threshold value K3 of the zero-sequence current integral value dI0 are used to identify the fault of the transmission line.

[0138] Preferably, the result unit 505 is used to calculate the three-phase active power change P at different times. AB 、P BC 、P CA Make a judgment and obtain the three-phase judgment coefficient k PA 、k PB 、k PC , also used for:

[0139]

[0140] Among them, k PA (t), k PB (t) and kPC (t) are the judgment systems of phase A, phase B and phase C at time t. If the judgment conditions are met, then the current time t otherwise

[0141] Preferably, the result unit 505 is used to determine the three-phase judgment coefficient k PA 、k PB 、k PC And the zero-sequence current I0 is integrated by sliding window to obtain the three-phase integral value dk PA 、dk PB 、dk PC And the zero-sequence current integral value dI0; based on the threshold value K1 of the obtained three-phase integral value, the three-phase reactive power Q φ The threshold value K2 of the zero-sequence current integral value dI0 and the threshold value K3 of the zero-sequence current integral value dI0 are used to identify the fault of the transmission line and are also used to:

[0142] For the three-phase judgment coefficient, k PB 、k PC The sliding window integration is performed with the zero-sequence current I0, and the integration time window length is T1. The phase integral value dk is calculated respectively. PA 、dk PB 、dk PC And the zero-sequence current integral value dI0:

[0143]

[0144] Where, I0(t) is the zero-sequence current at time t;

[0145] Take the three-phase integral value The threshold value is K1, three-phase reactive power The threshold of the zero-sequence current integral value dI0 is K2, and the threshold of the zero-sequence current integral value dI0 is K3. It is judged whether each phase in the line meets the following line break identification criteria:

[0146]

[0147] When it is determined that there is a phase that meets the transmission line trunk identification criterion during a continuous preset time period, the phase that meets the transmission line trunk identification criterion is determined to be a broken phase.

[0148] An overhead transmission line disconnection fault identification system according to a preferred embodiment of the present invention corresponds to an overhead transmission line disconnection fault identification method according to another preferred embodiment of the present invention, and will not be described in detail here.

[0149] It will be understood by those skilled in the art that the embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention may be implemented in various computer languages, for example, the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0150] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0151] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0152] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0153] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0154] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

[0155] The invention has been described above with reference to a few embodiments. However, it is readily apparent to a person skilled in the art that other embodiments than the ones disclosed above are equally within the scope of the invention, as defined by the appended patent claims.

[0156] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / / the [means, component, etc.]" are to be interpreted openly as referring to at least one instance of a means, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not necessarily need to be performed in the exact order disclosed, unless explicitly stated otherwise.

Claims

1. A method for identifying a disconnection fault in an overhead transmission line, the method comprising: Get the instantaneous value U of the three-phase voltage after the transmission line fault A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C ; The instantaneous value of the three-phase voltage U A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C Perform Fourier decomposition to obtain the three-phase voltage amplitude U MA 、U MB 、U MC , three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C ; Based on the three-phase voltage amplitude U MA 、U MB 、U MC , the three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate the three-phase active power P φ , three-phase reactive power Q φ and zero sequence current I0; Based on the three-phase active power P φ , calculate the three-phase active power change P AB 、P BC 、P CA , include: Among them, P AB (t), P BC (t), P CA (t) are the active power changes of phase A, phase B and phase C at time t; The three-phase active power changes P at different times AB 、P BC 、P CA Make a judgment and obtain the three-phase judgment coefficient k PA 、k PB 、k PC ,include: Among them, k PA (t), k PB (t) and k PC (t) are the judgment systems of phase A, phase B and phase C at time t. If the judgment conditions are met, then the current time t otherwise The three-phase judgment coefficient k PA 、k PB 、k PC And the zero-sequence current I0 is integrated by sliding window to obtain the three-phase integral value dk PA 、dk PB 、dk PC And the zero-sequence current integral value dI0; Based on the threshold value K1 and three-phase reactive power Q of the obtained three-phase integral value φ The threshold value K2 of the zero-sequence current integral value dI0 and the threshold value K3 of the zero-sequence current integral value dI0 are used to identify the fault of the transmission line, including: The three-phase judgment coefficient, k PB 、k PC The sliding window integration is performed with the zero-sequence current I0, and the integration time window length is T1. The phase integral value dk is calculated respectively. PA 、dk PB 、dk PC And the zero-sequence current integral value dI0: Where, I0(t) is the zero-sequence current at time t; Take the three-phase integral value The threshold value is K1, three-phase reactive power The threshold of the zero-sequence current integral value dI0 is K2, and the threshold of the zero-sequence current integral value dI0 is K3. It is judged whether each phase in the line meets the following line break identification criteria: When it is determined that there is a phase that meets the transmission line trunk identification criterion during a continuous preset time period, the phase that meets the transmission line trunk identification criterion is determined to be a broken phase.

2. The method according to claim 1, wherein the three-phase voltage amplitude U MA 、U MB 、U MC , the three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate the three-phase active power P φ , three-phase reactive power Q φ and zero sequence current I0, include: Where φ is phase A, B, and C; t is time; P φ (t) is the three-phase active power at time t; Q φ (t) is the three-phase reactive power at time t; U Mφ (t) is the three-phase voltage amplitude at time t; I Mφ (t) is the amplitude of the three-phase current at time t; θ φ (t) is the angle between the three-phase voltage and current at time t; I0(t) is the zero-sequence current at time t; I A (t), I B (t), I C (t) are the instantaneous current values ​​of phase A, phase B and phase C at time t respectively.

3. A system for identifying a disconnection fault of an overhead transmission line, the system comprising: The first acquisition unit is used to obtain the instantaneous value U of the three-phase voltage after the transmission line fails. A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C ; The second acquisition unit is used to obtain the instantaneous value U of the three-phase voltage A 、U B 、U C And the instantaneous value of three-phase current I A , I B , I C Perform Fourier decomposition to obtain the three-phase voltage amplitude U MA 、U MB 、U MC , three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C ; The first calculation unit is used to calculate the three-phase voltage amplitude U MA 、U MB 、U MC , the three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate the three-phase active power P φ , three-phase reactive power Q φ and zero sequence current I0; The second calculation unit is used to calculate the three-phase active power P based on the φ , calculate the three-phase active power change P AB 、P BC 、P CA ; The second calculation unit is used to calculate the three-phase active power P φ , calculate the three-phase active power change P AB 、P BC 、P CA , also used for: Among them, P AB (t), P BC (t), P CA (t) are the active power changes of phase A, phase B and phase C at time t; The result unit is used to calculate the three-phase active power changes P at different times. AB 、P BC 、P CA Make a judgment and obtain the three-phase judgment coefficient k PA 、k PB 、k PC ; The three-phase judgment coefficient k PA 、k PB 、k PC And the zero-sequence current I0 is integrated by sliding window to obtain the three-phase integral value dk PA 、dk PB 、dk PC And the zero-sequence current integral value dI0; based on the threshold value K1 of the obtained three-phase integral value, the three-phase reactive power Q φ The threshold value K2 of the zero-sequence current integral value dI0 and the threshold value K3 of the zero-sequence current integral value dI0 are used to identify the fault of the transmission line; The result unit is used to calculate the three-phase active power changes P at different times. AB 、P BC 、P CA Make a judgment and obtain the three-phase judgment coefficient k PA 、k PB 、k PC , also used for: Among them, k PA (t), k PB (t) and k PC (t) are the judgment systems of phase A, phase B and phase C at time t. If the judgment conditions are met, then the current time t otherwise The result unit is used to determine the three-phase judgment coefficient k PA 、k PB 、k PC And the zero-sequence current I0 is integrated by sliding window to obtain the three-phase integral value dk PA 、dk PB 、dk PC And the zero-sequence current integral value dI0; the threshold value K1 based on the obtained three-phase integral value, the three-phase reactive power Q φ The threshold value K2 of the zero-sequence current integral value dI0 and the threshold value K3 of the zero-sequence current integral value dI0 are used to identify the fault of the transmission line and are also used to: The three-phase judgment coefficient, k PB 、k PC The sliding window integration is performed with the zero-sequence current I0, and the integration time window length is T1. The phase integral value dk is calculated respectively. PA 、dk PB 、dk PC And the zero-sequence current integral value dI0: Where, I0(t) is the zero-sequence current at time t; Take the three-phase integral value The threshold value is K1, three-phase reactive power The threshold of the zero-sequence current integral value dI0 is K2, and the threshold of the zero-sequence current integral value dI0 is K3. It is judged whether each phase in the line meets the following line break identification criteria: When it is determined that there is a phase that meets the transmission line trunk identification criterion during a continuous preset time period, the phase that meets the transmission line trunk identification criterion is determined to be a broken phase.

4. The system according to claim 3, wherein the second acquisition unit is configured to: MA 、U MB 、U MC , the three-phase current amplitude I MA , I MB , I MC And the three-phase voltage and current angle θ A ,θ B ,θ C Calculate the three-phase active power P φ , three-phase reactive power Q φ and zero sequence current I0, and is also used for: in, φ is phase A, B, and C; t is time; P φ (t) is the three-phase active power at time t; Q φ (t) is the three-phase reactive power at time t; U Mφ (t) is the three-phase voltage amplitude at time t; I Mφ (t) is the amplitude of the three-phase current at time t; θ φ (t) is the angle between the three-phase voltage and current at time t; I0(t) is the zero-sequence current at time t; I A (t), I B (t), I C (t) are the instantaneous current values ​​of phase A, phase B and phase C at time t respectively.

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