Power distribution network single-phase high-resistance grounding fault detection method based on full phasor measurement

Abstract

The invention provides a power distribution network single-phase high-resistance grounding fault detection method based on full phasor measurement, and the method comprises the steps: deducing a deterministic function relation among phase voltage, phase current and unbalanced current through line state space analysis, and constructing a monitoring quantity calculation method which is approximately equal to fault current; according to the present invention, the coefficient is solved based on the measurement data during the fault-free operation of the system, and the current monitoring amount is calculated by using the solved coefficient, such that the fault detection and the line selection are achieved, the method is suitable for the point-to-point direct supply special line, the early detection capability of the high resistance grounding fault is significantly improved, and the new technical means is provided for ensuring the important load power supply reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network detection, and particularly to a method for detecting single-phase high-resistance grounding faults in a distribution network based on full phasor measurement. Background Art

[0002] With the accelerating advancement of the intelligent upgrading of China's manufacturing industry, the in-depth application of artificial intelligence technology, and the transformation of transportation electrification, the medium-voltage distribution network presents the dual characteristics of a sharp increase in large-capacity and highly sensitive loads and the large-scale access of centralized and distributed energy. The number of dedicated lines directly from substations to users has increased rapidly. The reliable operation of such lines is directly related to the stability of core industrial production capacity, the continuity of power supply for critical infrastructure, and the new energy consumption efficiency.

[0003] The distribution line passes through a complex environment and is prone to high-resistance grounding faults (HIF) such as wire touching trees and human electric shock. Especially when the grounding fault transition resistance is greater than 10 kΩ, the fault electrical quantity characteristics are weak and it is difficult to be detected by existing equipment, which may lead to major safety accidents such as fires and casualties, or the spread of faults may lead to serious power outages. To ensure the reliability of dedicated line power supply, it is necessary to detect and dispose of high-resistance grounding faults such as wire touching trees early, which requires the relay protection system to have sensitive single-phase high-resistance grounding fault monitoring capabilities. In addition, high-resistance grounding faults belong to weak asymmetric faults, and the unbalanced current generated by factors such as untransposed lines and non-full-phase power supply in the actual distribution network adds difficulties to fault detection and becomes one of the main interference factors for high-resistance grounding fault detection.

[0004] Existing HIF detection methods are mainly divided into transient methods, steady-state methods, and AI methods. Based on the distortion and irregularity of the transient time-domain zero-sequence current waveform, the existing technology realizes the quantification of signal fluctuations through the nonlinear analysis of the waveform and then uses mathematical morphology to enhance the fault characteristics to achieve HIF detection. However, when the distortion of the fault signal is extremely small, the sensitivity decreases. In order to better capture the transient characteristics, some scholars use the harmonic components of HIF for detection, but it is prone to failure in the nonlinear load switching scenario. In the existing technology, there is also the use of differential energy detection of positive-sequence current components to reduce the influence of nonlinear loads, but it is limited in application for situations such as unbalanced operation. Although the existing technology combines the traveling wave method with energy mutation to construct an HIF criterion to solve the confusion of normal transient disturbances, its applicability in actual different systems still needs to be verified. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a method for detecting single-phase high-resistance grounding faults in a distribution network based on full phasor measurement, including the following steps: Full phasor at the line outlet without a fault Zero-sequence current And monitored quantity The functional relationship existing between them is as follows: ; wherein, K is a 6×1 complex coefficient vector; When the line is operating normally without a fault, let , and use at least 6 sets of measured values of the full-phase vectors and zero-sequence currents to solve the complex coefficient vector K; After completing the solution of K, use the real-time measured values of the full-phase vectors and zero-sequence currents and the calculated complex coefficient vector K to calculate the current monitored quantity ; Determine whether the current monitored quantity is located in the protection action area. If so, determine that a fault exists and execute the protection action.

[0006] In the preferred embodiment, when the line is free of faults, the current of each phase to the ground is: ; wherein, the three-phase voltage vectors to the ground at the outlet of Line1 are , the three-phase current vectors are , is the full length of Line1, is the current of each phase to the ground, i = A, B, C; A, B, C represent three phases, is the admittance matrix of Line1 to the ground, the impedance matrix per unit length of Line1 is Z, and the propagation constant is ; Since the zero-sequence current is the sum of the currents of each phase of the three-phase line to the ground : ; Therefore, there is a fixed functional relationship between the full-phase vector at the outlet of the line without a fault and the zero-sequence current : ; The monitored quantity is: ; When there is no fault, there is .

[0007] In the preferred embodiment, solve the zero-sequence current during a single-phase ground fault: If there is a single-phase ground fault with a ground admittance of Y f at the l f position of phase A, divide the line into two sections of 0~l f and l f ~l for solution. The solution process for the first section is: ; ; where the superscripts (1) or (2) represent the first or second section of the line, is the three-phase current and voltage at the start of the second section; the three-phase current vector of the first section of the line is , and the three-phase current vector of the second section of the line is ; Calculate the three-phase capacitance current to ground according to the following formula : ; , are the three-phase voltage vectors to ground at a distance x from the Line1 outlet in the first and second sections of the line respectively; For a specific fault, there is also a definite functional relationship between the full vector at the line outlet and the zero-sequence current: ; If the function obtained under normal fault-free conditions is still used to solve , then during a fault, there is , and is approximately equal to the fault current.

[0008] In the preferred embodiment, linearized dimensionality reduction is used to solve, and a monitoring quantity equation is constructed: Solve and for the complex coefficient matrices M and N: ; ; where is a 3-order matrix, the impedance admittance matrix is a 3-order square matrix, and both M and N are 3-order matrices, then: ; ; where , are the elements in the i-th row and j-th column of M and N respectively, , represent the j-th element of the vector; After arrangement: ; Then it is simplified to: ; With the load fluctuations and line switching during normal system operation, obtain at least 6 different and and then solve the complex coefficient vector K under normal system operation to construct a monitoring quantity equation: 。

[0009] In a preferred embodiment, the monitored quantity calculated under normal conditions is approximately equal to 0; During a single-phase ground fault, the calculated monitored quantity is approximately equal to the fault current; The influence of the consistency measurement deviation of voltage transformers and current transformers and the direct measurement or three-phase synthesis acquisition method of zero-sequence current on the calculation error of the monitored quantity is negligible.

[0010] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention proposes a high-resistance ground fault detection method for distribution networks based on full phasor measurement using state space theory. Compared with the sensitivity upper limit of about 10 kΩ of traditional zero-sequence current protection, the theoretical upper limit of the detection sensitivity of this method is increased to several hundred kΩ, and it is independent of the system grounding method, and has self-adaptability under different line and load parameters, which can greatly improve the system's ability to observe line faults, and can be used for sensitive detection and early elimination of high-hazard and high-risk faults or hidden dangers such as personnel electric shock, tree faults, and cable insulation damage, and greatly improve the prevention ability of electrical line accidents for point-to-point direct supply dedicated lines and the power supply reliability of important sensitive loads.

[0011] The method proposed by the present invention has theoretical completeness and shows extremely high detection sensitivity in digital simulation, but lacks actual engineering verification. To ensure reliability, in actual application scenarios, the action threshold can be set according to safety requirements, such as a 30 mA threshold to ensure personal safety in live working scenarios, a 200 mA threshold to prevent fires in the case of wire touching trees, etc. Brief Description of the Drawings

[0012] Figure 1 is an unbalanced current analysis model for a medium-voltage distribution system; Figure 2 is a simulation model of a medium-voltage distribution network; Figure 3 is the simulation result of the fault line; Figure 4 is the simulation result of the non-fault line. Detailed Embodiments

[0013] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0014] 1. When there is no fault in the line, there is a fixed complex linear relationship between the unbalanced current in the running state of the line and the full phasor at the line outlet. The complex coefficient vector K in this relationship is obtained by solving the state space. Using the zero-sequence current in the running state of the line , to solve for K.

[0015] Given the analysis system as Figure 1 shown. Taking Line1 as the research object, for simplicity of analysis, it is assumed that the line parameters are uniform. Since the range and speed of change of parameters such as the structure and material of the line over time are extremely small, the per-unit-length impedance matrix Z and admittance matrix Y of the line are regarded as constants.

[0016] Define the three-phase ground voltage vector and the three-phase current vector at a distance x from the outlet of Line1 as (1); (2); where the subscript 1 represents Line1, and A, B, C represent the three phases. The line state variable at a distance x from the starting end of the line is: (3); Then the state equation at a distance x is: (4); where A is the system matrix: (5); The analytical solution of Equation (4) is: (6); Expand at x = 0: (7); where I is the 6th-order identity matrix.

[0017] Substitute Equation (5) and simplify to get (8); It is in the form of a series expansion of a hyperbolic function, that is: (9); where the propagation constant .

[0018] Then the phase voltage at x is: (10); Then the three-phase ground current of the entire line is: (11); where l is the total length of Line1, is the admittance matrix of Line1 to the ground:

[0019] (12); where is the admittance of each phase to the ground. After arrangement, we get: (13); where is the current of each phase to the ground. Except for the phase voltage and phase current at the line outlet on the right side of this formula, the others are all 3D constant complex coefficient matrices determined by line parameters, indicating that there is a fixed functional relationship between the current of each phase to the ground and the phase voltage and phase current at the line outlet.

[0020] Zero-sequence current physically means the current of the loop formed by the line and the ground, which has nothing to do with the phase current. Therefore, the zero-sequence current is actually the sum of the currents of each phase of the three-phase line to the ground, that is: (14); It can be seen from equations (13) and (14) that under the condition of fixed line parameters, there is a definite functional relationship between the full vector at the line outlet without a fault and the zero-sequence current. Denote this relationship as: (15); Define the monitored quantity: (16); Then when there is no fault, we have .

[0021] 2. When there is a single-phase ground fault on the line, the unbalanced current in the zero-sequence current can be calculated using the full-phase vector at the line outlet, and the difference between the zero-sequence current and the calculated unbalanced current is not zero.

[0022] If there is a single-phase ground fault with a ground admittance of Y f at the position of l f in phase A, the line is divided into two sections: 0~l f and l f ~l for solution.

[0023] The solution process of the first section is similar to the previous part, except that the line length changes from l to l f , and we get: (17); (18); where the superscript (1) or (2) represents the first or second section of the line, , As the boundary conditions for the solution in the second paragraph, after obtaining , , the three-phase capacitance currents to the ground can be calculated by the following formula: (19); Furthermore, it can be known that for a specific fault, there is also a definite non-linear function relationship between the full vector at the line outlet and the zero-sequence current.

[0024] (20); If the function f obtained under the fault-free condition is still used to solve , since , there is .

[0025] By comparing the results of the first part and this part, it is easy to see that using the phase voltage and phase current measurements to compensate for the unbalanced capacitance current in the zero-sequence current, and then realizing the single-phase grounding fault detection, has basic feasibility in principle.

[0026] 3. Perform linearized dimensionality reduction suitable for engineering applications according to the parameter structure, and construct a six-dimensional constant complex coefficient linear calculation equation for the monitored quantities.

[0027] It can be seen from equation (13) that the key to the problem lies in solving the complex coefficient matrices and of and .

[0028] From the definition of , it is easy to know that is a 3-order matrix, and the other impedance admittance matrices are also 3-order square matrices. Therefore, both M and N are 3-order matrices.

[0029] Equation (13) is rewritten as: (21); Then equation (14) is: (22); where , are the elements in the i-th row and j-th column of M and N respectively, and , the superscript j represents the j-th element of the vector.

[0030] After further arrangement: (23); It can be seen that the coefficients of the phase voltage and phase current are the sums of the corresponding columns in the constant complex coefficient matrices M and N, and are still a constant complex coefficient. When solving, it is not necessary to calculate all 18 matrix elements. Therefore, Equation (23) is simplified as follows: (24); where K is a 6×1 complex coefficient vector.

[0031] When at least 6 different sets of and are obtained, the complex coefficient vector K under normal system operation can be solved, and then the monitored quantity equation can be constructed: (25); 4. The monitored quantity is approximately equal to the fault grounding current for the fault line and almost zero for the non-fault line.

[0032] Equation (25) gives the calculation formula of the monitored quantity , but its physical meaning is still not clear, which is not conducive to setting the action threshold. In this embodiment, its physical meaning is analyzed.

[0033] From the expansion formulas of the hyperbolic sine and cosine functions, it is easy to obtain: (26); (27); Given a typical propagation constant of the distribution line , it has the following characteristics: the modulus of the diagonal elements is about 0.03, and the modulus of the non-diagonal elements is about -0.005 to -0.012. If the line length is short (l < 30 km), the error introduced by taking only the first term in Equations (26) and (27) is not greater than 0.5%. Therefore, both take the first term and substitute it into Equation (13) to get: (28); where, , represent the admittance and impedance of the whole line.

[0034] It can be seen that in this approximate calculation, the influence of the ground current and the phase-to-phase circulating current on the phase current is ignored, and the current of the whole line is regarded as the same, then the phase voltage is linearly related to the distance. At this time, the above formula has a clear physical meaning. The first term represents the current generated by the phase voltage at the line outlet on the admittance to the ground of the whole line, and the second term represents the current generated by half of the line voltage drop on the admittance to the ground of the whole line. This formula is derived from the line state space, and the condition for its establishment is only that the line parameters are constant, and it has nothing to do with the source-load state at both ends of the line, the line power flow direction, the system neutral point grounding method, etc.

[0035] Since the line parameters change slowly and the fluctuation range is extremely small, , can be regarded as a constant. Therefore, under the fault-free state, this formula and formula (25) hold for any phase voltage and phase current.

[0036] When there is a high-resistance grounding fault in phase A where the fault current is much smaller than the line load current, the phase voltage at the line outlet becomes , the phase voltages of each phase are still approximately linearly distributed with distance, the phase currents of each phase are approximately unchanged, and formula (25) becomes: (29); The second term is the unbalanced capacitive current to ground of the non-fault state assuming the system is operating normally in 、 state. And from the definition of zero-sequence current, it can be known that . And is actually the unbalanced current the sum of this non-fault component and the fault grounding current this fault component. Since the fault current is much smaller than the load current, the influence on the second term of formula (29) is relatively small. Moreover, since the physical meaning of the second term of formula (29) is the current to ground generated by the line voltage drop, there is a difference of one or more orders of magnitude compared with the first term. Therefore, the non-fault component is approximately equal to the unbalanced current 、 in the state when the system is operating normally in . In summary, the calculated monitored quantity is approximately equal to the fault current, that is: (30); 5. The influence of the measurement consistency deviation on the calculation accuracy can be ignored.

[0037] In the previous analysis, the phase voltage, phase current, and zero-sequence current are all exact values. In practical applications, the measurement errors introduced by the transformers are inevitable. This chapter analyzes the influence of the measurement errors on the method.

[0038] Assume that the ratios of the measured vectors of the three-line voltage and current transformers to the true vectors 、 、 、 、 、 are the diagonal elements of the diagonal matrix e, and the ratio of the measured vector of the zero-sequence current transformer to the actual vector is , then the measured values are and . When solving for K with the system fault-free, is 0, and the measured zero-sequence current is the unbalanced current with measurement error , then there is: ​ (31); After a fault, there is: (32); Among them is the full phasor at the line outlet after a fault.

[0039] As can be seen from the previous analysis, the sum of the first two terms of the above formula is always 0, and there is also so there is close to 1, so there is (33); Considering the scenario of synthesizing zero-sequence current for three phases, the measured zero-sequence current is , when there is no fault, there is: (34); After a fault, there is: (35); Similar to formula (33), obviously there is: (36); That is, when using three-phase current to synthesize zero-sequence current, the influence on the calculation error of the monitored quantity is extremely small.

[0040] In summary, the influence of the transformer measurement error and the zero-sequence current measurement method on the calculation error of the monitored quantity can be ignored.

[0041] 6. Detection process and verification of full phasor unbalance compensation high-resistance grounding fault Based on the above analysis, a detection method for full phasor unbalance compensation high-resistance grounding fault is constructed, and its basic process is as follows: a) When there is no fault on the line, let , substitute the measured values of phase voltage, phase current, and zero-sequence current into formula (25) to calculate the complex coefficient vector K; b) After calculating the complex coefficient vector K, calculate the current monitored quantity in real time according to formula (25); c) Determine whether is located in the action area. If so, execute corresponding actions such as alarm and tripping.

[0042] To verify the correctness of this method, a medium-voltage distribution system with n outgoing lines as shown in Figure 2 is established using Matlab / Simulink. Z NG is the neutral grounding impedance. Three lines (Line1 and Line2 are overhead lines, and Line3 is a cable) are simulated with a π model containing unbalanced line parameters, and other lines are simulated in the lumped form of unbalanced three-phase ground capacitances .

[0043] By changing the total capacitive current of the regulating system is adjusted to be lower than 30 A, set it to open circuit to simulate the neutral point ungrounded system. The A phase of Line 1 is connected to a grounding resistor with a resistance value of R f to simulate the grounding fault. The three-phase loads of each outgoing line are independently set for the three-phase load and single-phase load power supply scenarios respectively. The three-phase load scenario accounts for 70%, and random values are assigned according to the requirements that the unbalanced capacity does not exceed 10% and the power factor is not less than 0.9 to simulate the three-phase load fluctuation. The single-phase power supply scenario accounts for 30%, and the load capacity and power factor of the power supply phase are randomly determined. The phase voltages, phase currents, and zero-sequence currents at the outlets of the 3 lines are solved in the phase domain.

[0044] By setting different R f resistance values to simulate different fault transition resistance conditions. The simulation is carried out in groups. For each group of simulations, R f is respectively set to 10 GΩ, 60 kΩ, 40 kΩ, 20 kΩ, 10 kΩ, 5 kΩ, 3 kΩ, 2 kΩ, 1 kΩ, a total of 9 groups. For each group, different random capacities are set for the 3 lines, and unbalanced three-phase loads are assigned to the 3 lines within the unbalanced tolerance requirements for 100 simulations.

[0045] To simulate the measurement error of the current transformer in the actual application scenario, a fixed proportion of deviation is added to the simulation data. The accuracy requirement of a 0.2-class current transformer is that the measured amplitude error is not higher than 0.2%, and the angle error does not exceed 2 minutes. To simulate the worst measurement conditions, the simulation is carried out according to the measurement error not higher than 1%. The specific method is to generate a random angle vector with an amplitude from -0.01 to 0.01 and superimpose it on the 1 vector to form a measurement error simulation vector. Each phase voltage, phase current, and zero-sequence current corresponds to an error simulation vector, and its simulation value is multiplied by the corresponding error simulation vector to simulate the inherent measurement error of each current transformer.

[0046] After calculating K using the noise-added data of the fault-free group, the monitored quantities of each outgoing line in each fault resistance scenario are calculated using the obtained K and the noise-added data.

[0047] Taking the simulation group with R f = 10 GΩ as the fault-free group of the system, the complex coefficient vector K of each line is calculated by the least squares method, and then the monitored quantity of the corresponding line is solved according to equation (25). . Repeat the simulation 10 times, and take the one with the largest fluctuation range of the zero-sequence current. Compare the accurate value of the fault current, the measured value of the monitored quantity, and the measured value of the zero-sequence current. As Figure 3 、 4 shown, where Figure 3The simulation results of the fault resistance being 10 GΩ, 60 kΩ, 20 kΩ, 10 kΩ, 5 kΩ, and 2 kΩ for the fault line in (a)-(f) are as follows. Figure 4 The simulation results of the fault resistance being 10 GΩ, 60 kΩ, 20 kΩ, 10 kΩ, 5 kΩ, and 2 kΩ for the non-fault line in (a)-(f) are as follows.

[0048] From Figure 3 the simulation results of (a) in Figure 4 and (a)-(f) in

[0049] it can be seen that when the simulated system is operating normally, under the influence of unbalanced line parameters and unbalanced loads, the amplitude of the zero-sequence current in the line (all are unbalanced currents) can reach about 0.7 A magnitude, and the fluctuation range of the amplitude can reach about 0.5 A magnitude. For systems or lines with a greater degree of unbalance, the above two amplitudes may be larger, which is consistent with on-site experience. After data processing according to the method proposed in the present invention, K is calculated using the phase voltage and phase current under normal operation of this line, and then the monitored quantity is calculated according to Equation (25). The of all groups of the non-fault group of the fault line and all groups of the non-fault line do not exceed 1 mA. During a fault,

[0050] Compared with the error does not exceed 30 mA, and this error increases as the fault resistance decreases and only appears in the 2 kΩ group. More groups of simulations are carried out to test the applicability of the method under different grounding systems and scenarios of synthesizing zero-sequence current from three-phase currents. Change Adjust the total capacitive current of the system to about 50 A, Set it as an arc suppression coil with overcompensation of 8% to simulate a resonant grounding system. All three lines are changed to cable lines. Change

[0051] As can be seen from the simulation results, when there is an imbalance in the system itself, the amplitude of the zero-sequence current without a fault is not zero, and the amplitude of the zero-sequence current may decrease when a single-phase ground fault occurs. If the zero-sequence current is obtained by synthesizing three-phase currents, the consistency deviation of the current transformers results in the measured zero-sequence current amplitude being greater than the true zero-sequence current amplitude. Assuming that the maximum amplitude of the unbalanced current during normal system operation reaches 2 A and the maximum amplitude fluctuation range is 1 A, the former limits the upper limit of the fault transition resistance tolerance of the zero-sequence amplitude over-limit detection method to approximately 3 kΩ, and the latter limits the upper limit of the fault transition resistance tolerance of the sudden change detection method to approximately 6 kΩ.

[0052] In the case of a serious consistency deviation in the measurement accuracy of the current transformers, the method of the present invention can still effectively compensate for the unbalanced current introduced by line parameters and load imbalance. The absolute error between the obtained monitored quantity and the actual fault current is at the mA level. Therefore, when setting the fault detection threshold based on the monitored quantity, it is no longer necessary to consider the unbalanced current fluctuation range, but rather to consider the maximum fluctuation range of the relative calculation error of the monitored quantity with respect to the fault current. The theoretical upper limit of the fault transition resistance tolerance can reach several hundred kΩ.

[0053] Since the average relative error of the monitored quantity compared to the actual fault current is less than 0.7% and the maximum error is less than 1%, it can be considered that the calculated monitored quantity is the fault current. Considering the line selection scenario, since the calculation of the monitored quantity only depends on the state of this line, when a fault occurs on a non-this line or an unbalanced load on this line causes a three-phase imbalance in the system, the amplitude of the monitored quantity is not higher than 1 mA. Therefore, by determining a very small threshold (such as 10 mA), it can be determined whether this line is a fault line without comparing with other lines.

[0054] Table 1 Simulation results of the monitored quantity error under different scenarios

[0055] In Table 1, Inf represents the fault-free group, and - represents meaningless.

[0056] The all-phase vector unbalanced compensation high-resistance ground fault detection method proposed by the present invention based on the state space theory, compared with the sensitivity upper limit of the traditional zero-sequence current protection at the 10 kΩ level, the theoretical upper limit of the detection sensitivity of this method is increased to the level of several hundred kΩ, and it is independent of the system grounding method. It can greatly improve the system's ability to observe line faults, and can be used for sensitive detection and early elimination of high-hazard and high-risk faults or potential hazards such as electric shock to personnel, tree faults, and cable insulation damage, and can greatly improve the prevention ability of electrical line accidents for point-to-point direct supply dedicated lines and the power supply reliability of important sensitive loads.

[0057] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Thus, all changes that fall within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A single-phase high-resistance grounding fault detection method for a distribution network based on full-phase measurement, characterized in that: The steps include: Full phase quantity at the line outlet when there is no fault , zero sequence current And monitoring volume The functional relationship between them is as follows: ； Where K is a 6×1 complex coefficient vector; When the line is operating normally without any fault, , using at least 6 different sets of full-phase and zero-sequence current measurements, solve the complex coefficient vector K; After solving K, the real-time measurement values ​​of the full phase and zero-sequence current and the calculated complex coefficient vector K are used to calculate the current monitoring quantity in real time. ; Determine the current monitoring amount Is it located in the protection action area? If so, it is determined that there is a fault and the protection action is executed.

2. The method for detecting single-phase high-resistance grounding fault in distribution network based on full-phase measurement according to claim 1 is characterized in that: When there is no fault in the line, the currents of each phase to ground are: ； Among them, the three-phase voltage vector at the outlet of Line 1 is , the three-phase current vector is , is the total length of Line1, is the current relative to ground, i=A,B,C; A, B, C represent three phases, is the admittance matrix of Line 1 to ground, the unit length impedance matrix of Line 1 is Z, and the propagation constant is ; Due to the zero sequence current is the ground current of each three-phase line sum: ； Therefore, the full phase quantity at the line outlet when there is no fault With zero sequence current There is a fixed functional relationship between them: ； Monitoring volume for: ； No trouble .

3. The method for detecting single-phase high-resistance grounding fault in distribution network based on full-phase measurement according to claim 2 is characterized in that: Solve the zero-sequence current when a single-phase grounding fault occurs: If phase A f There is an admittance to the ground of Y f Single-phase grounding fault, the line is divided into 0~l f and l f ~l are solved in two stages, and the solution process of the first stage is: ； ； The superscript (1) or (2) indicates the first or second line segment. is the three-phase current and voltage at the beginning of the second section; the three-phase current vector of the first section line is , the three-phase current vector of the second section line is ; Calculate the three-phase ground capacitance current as follows: : ； , are the three-phase voltage vectors to the ground at the distance x from the outlet of Line1 in the first and second sections of the line respectively; For a specific fault, there is also a definite functional relationship between the full vector at the line outlet and the zero-sequence current: ； If we still solve the problem using the function obtained when there is no fault , then the fault occurs ,and Approximately equal to the fault current.

4. The method for detecting single-phase high-resistance grounding fault in distribution network based on full-phase measurement according to claim 3 is characterized in that: Using linear dimensionality reduction to solve, construct the monitoring quantity equation: Solution and The complex coefficient matrices M and N are: ； ； in is a 3rd-order matrix, the impedance-admittance matrix is ​​a 3rd-order square matrix, M and N are both 3rd-order matrices, then: ； ； in , are the i-th row and j-th column elements of M and N respectively, , represents the jth element of a vector; Arranged: ； Then it simplifies to: ; With the load fluctuation and line switching under normal system operation, at least 6 groups of different and Finally, solve the complex coefficient vector K under normal operation of the system and construct the monitoring quantity equation: 。 5. The method for detecting single-phase high-resistance grounding fault in distribution network based on full-phase measurement according to claim 3 is characterized in that: The monitoring quantity calculated when there is no fault is approximately equal to 0; In case of single-phase grounding fault, the calculated monitoring quantity is approximately equal to the fault current; The influence of the consistency measurement deviation of voltage transformer and current transformer and the direct measurement or three-phase synthesis acquisition method of zero-sequence current on the calculation error of the monitored quantity is negligible.

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