DG-containing distribution line single-phase earth fault single-end impedance distance measurement technology

Abstract

The invention discloses a DG-containing distribution line single-phase earth fault single-end impedance distance measurement method and system, and the method comprises the steps: inputting parameters and DG distribution conditions into equipment, when a distribution network has a single-phase earth fault, enabling the zero-sequence voltage of the equipment to rise, judging the occurrence of the single-phase earth fault, and starting fault distance measurement calculation; using a symmetric component method to calculate sequence components of voltage and current at the bus, the DG access, the load access and the fault point; and on the basis of the sequence components of the voltage and the current of the fault point, the phasor angle difference between the voltage and the current of the line fault is obtained, and the fault distance is calculated according to the phasor angle difference. The method is good in distance measurement effect and has practicability.

Description

Technical Field

[0001] The present invention belongs to the field of single-ended fault ranging, and in particular, relates to a single-ended impedance ranging method and system for single-phase grounding fault of a distribution line containing a DG. Background Art

[0002] At present, experts and scholars have proposed many single-phase grounding fault distance measurement technologies for distribution networks. According to the principle, most methods can be divided into two categories: traveling wave method and impedance method. The time it takes for the voltage and current traveling waves propagating from the fault point to both ends of the line to reach the detection point after the fault occurs can be used to calculate the line length from the fault point to the head end of the line based on the traveling wave speed and time. According to the specific implementation method, the traveling wave method can be divided into many different methods such as type A, type B, and type C. The traveling wave method is not affected by factors such as the transition resistance of the fault point and the access of distributed power sources. The impedance method calculates the equivalent impedance between the measurement point and the fault point by detecting the power frequency phase of the voltage and current after the fault occurs. The line length from the fault point to the head end of the line can be calculated based on the impedance per unit length of the line. The impedance method is not affected by zero-crossing faults, has a low sampling rate, is not costly, and is easy to promote.

[0003] The existing traveling wave method has the problem of weak traveling wave signals when there is a zero-crossing fault. In addition, the traveling wave method requires a high-speed signal sampling device, especially the two-terminal traveling wave ranging technology, which requires the installation of a large number of detection devices at the end of each line of the distribution network, making it difficult to promote.

[0004] The impedance method is easily affected by factors such as the transition resistance at the fault point and the load current. In particular, a large number of distributed power sources are currently connected to the distribution network. The high frequency of harmonics and voltage changes caused by the access of distributed power sources has brought challenges to the single-phase grounding fault distance measurement technology. In addition, the existing single-ended impedance method also ignores the problem of current angle, resulting in inaccurate impedance calculation when distributed power sources are connected. Under complex conditions such as high transition resistance and harmonic interference, the fault location may be incorrectly identified.

[0005] The prior art document (CN116930685A) discloses a single-ended distance measurement method suitable for single-phase grounding faults in distribution networks. The method used in this document does not belong to the commonly used impedance method, so it is greatly affected by voltage and current fluctuations. The sampling device used must be high-frequency and require high accuracy. The calculation process is complicated and the calculation time is long. The least squares method is used for fitting and solving. The result is a numerical result, which is relatively idealized and difficult to apply in practice. Summary of the invention

[0006] In order to solve the deficiencies in the prior art, the present invention provides a method for obtaining the voltage and current phasors of each line by measuring the voltage and current phasors at the line head end M for a simple single line according to a centralized parameter circuit model. The voltage and current vector angles at each position of the line are compared to obtain the fault location. According to the single line model, the calculation formulas for hybrid lines, multi-branch lines, and lines with distributed power access can be obtained.

[0007] The first aspect of the present invention discloses a single-ended impedance distance measurement method for a single-phase ground fault of a distribution line taking into account DG, comprising:

[0008] Enter parameters into the distance measurement center. When a single-phase grounding fault occurs in the distribution network, the zero-sequence voltage of the equipment increases, and it is determined that a single-phase grounding fault has occurred, and the fault distance measurement calculation is started;

[0009] The sequence components of voltage and current at the fault point are calculated using the symmetrical component method;

[0010] Based on the sequence components of the voltage and current at the fault point, the phasor angle difference between the line fault phase voltage and current is obtained, and the fault distance of the distribution line containing distributed generation is determined according to the phasor angle difference.

[0011] Preferably, the process of calculating the fault distance is as follows:

[0012] Starting from the beginning of the line, an initial step length x is set, and the initial step length x is continuously increased, each time by a set step length increment until it is equal to the total length L of the line; each time the step length is increased, the fault phase voltage and fault phase current at the current step length are calculated, and the phase angle difference θ between the two is calculated. The step length corresponding to the minimum value of all calculated angle differences is the fault distance.

[0013] Preferably, the phase angle difference θ can be expressed by the following formula:

[0014]

[0015] In the formula, is the voltage of the fault phase, is the current of the fault phase.

[0016] Preferably, the voltage and current of the fault phase of the single-type line and the mixed-type line can be expressed by the following formula:

[0017]

[0018] In the formula, is the voltage of the fault phase, are the three-sequence voltage phasors of the fault point, is the zero-sequence current phasor at the fault point, is the current of the fault phase.

[0019] Preferably, for a distribution network containing a load branch and a distribution network containing a distributed power generation branch, the voltage and current of the fault phase can be expressed by the following formula:

[0020]

[0021] In the formula, are the three-sequence voltage phasors of the fault point, They represent the three-sequence current phasors on the right side of point A respectively.

[0022] Preferably, if the line at the location of the fault point is a single-type line distribution network, the three-sequence voltage and zero-sequence current at the fault point can be expressed by the following formula:

[0023]

[0024] In the formula, They are the three-sequence voltage phasors of the fault point respectively; They are the three-sequence voltage phasors measured at the endpoints of the head end respectively; are the three-sequence current phasors measured at the end points of the head end; y1, y2, y0 represent the three-sequence admittance of the line per unit length; z1, z2, z0 represent the three-sequence impedance of the line per unit length, is the zero-sequence current phasor at the fault point, is the zero-sequence current phasor on the left side of the fault point, is the zero-sequence current phasor on the right side of point F, x is the distance between the fault point and the first end of the line, and L is the total length of the line.

[0025] Preferably, if the line at the location of the fault point is a mixed type line distribution network, the three-sequence voltage and zero-sequence current at the fault point can be expressed by the following formula:

[0026]

[0027] In the formula, are the three-sequence voltage phasors of the fault point respectively; y1′, y′2, y′0 represent the three-sequence admittance per unit length of the PN section line respectively; z1′, z′2, z′0 represent the three-sequence impedance per unit length of the PN section line respectively; They represent the three-sequence voltage phasors of the line boundary point P respectively; They represent the three-sequence current phasors of the line boundary point P respectively; L MP It is the length of the line from point M at the beginning of the line to point P at the dividing point.

[0028] Preferably, if the line at the location of the fault point is a distribution line with a load branch, the sequence component of the fault point voltage is the same as that of a single type of line, when the fault point is located on the left side of the branch point, the sequence component of the fault point current is the same as that of the single type of line, and when the fault point is located on the right side of the branch point, the three-sequence components of the fault point current are calculated, and the three-sequence components of the fault point current can be expressed by the following formula:

[0029]

[0030] In the formula, Represents the three-sequence current phasors on the right side of the dividing point A The three-sequence current phasors on the left side of the demarcation point A respectively; They represent the three-sequence current phasors at the head end of branch AB respectively.

[0031] Preferably, if the line where the fault point is located is a distribution line containing more than one load branch, the voltage sequence component of the fault point can be expressed by the following formula:

[0032]

[0033] In the formula, They are the three-sequence voltage phasors at point A; They are the three-sequence voltage phasors measured at the head end point M respectively; are the three-sequence current phasors measured at the head end point M; y1, y2, y0 represent the three-sequence admittance per unit length of the line; z1, z2, z0 represent the three-sequence impedance per unit length of the line; L MA Indicates the length of the MA segment of the line.

[0034] Preferably, if the line at the location of the fault point is a distribution line containing a distributed power generation branch, the three-sequence voltage at the fault point is the same as that of a single type of line, and the three-sequence current at the fault point can be expressed by the following formula:

[0035]

[0036] In the formula, They represent the three-sequence current phasors on the right side of point A, The three-sequence current phasors on the left side of point A respectively; They represent the three-sequence current phasors at the head end of branch AB respectively.

[0037] The second aspect of the present invention discloses a single-ended impedance distance measurement system for single-phase grounding fault of distribution line taking into account DG, and the method is executed as described above, comprising:

[0038] Data entry module, used to enter necessary parameters into the device;

[0039] Fault detection module, used to monitor the zero-sequence voltage of the equipment and determine whether a single-phase grounding fault occurs;

[0040] The fault distance measurement module is used to calculate the fault distance of the distribution network containing distributed power sources when a fault occurs.

[0041] The beneficial effect of the present invention is that, compared with the prior art, the method of the present invention has a good ranging effect and is practical. The method of the present invention is simple and feasible, requires a small amount of data, only requires transient information, reduces the required memory, and has a short calculation time. It is applicable to various topological line modes including distributed power sources, cable high-voltage hybrid lines, or multi-branch lines, and can improve the scope of application of the single-ended impedance method, reduce the proportion of one-time investment, and has a fast calculation speed and high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of a simple line single-phase grounding fault;

[0043] Figure 2 This is a schematic diagram of a single-phase grounding fault in a hybrid line;

[0044] Figure 3 This is a schematic diagram of a single-phase grounding fault occurring in a load branch;

[0045] Figure 4 It is a schematic diagram of a single-phase grounding fault occurring in multiple load branches;

[0046] Figure 5 It is a schematic diagram of a single-phase grounding fault occurring in a distributed power supply branch;

[0047] Figure 6 It is a schematic diagram of the simulation model of the circuit;

[0048] Figure 7 It is the result of single-phase grounding fault of the model line when the fault distance is 500m;

[0049] Figure 8 This is the result of a single-phase ground fault in the model line when the fault distance is 3000m;

[0050] Fig. 9 It is the result of single-phase grounding fault of the model line when the grounding resistance is 500Ω;

[0051] Fig.10 It is a flow chart of the single-ended fault location method. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0053] The first embodiment of the present invention is as follows Fig.10 As shown, a single-ended impedance distance measurement method for a single-phase ground fault of a distribution line including a DG is provided, comprising the following steps:

[0054] Step 1: Enter necessary parameters in advance to the control center or ranging center (i.e. where the final ranging result is displayed), including: topology parameters, installation location of the ranging algorithm center, DG access status and location, etc.

[0055] Step 2: When a single-phase grounding fault occurs, the zero-sequence voltage of the distribution network including the DG increases, and it is determined that a single-phase grounding fault has occurred, and the fault distance calculation is started.

[0056] Step 3: After confirming that a single-phase grounding fault has occurred in the distribution network containing DG, Fourier transform the steady-state data of phase voltage and current at the bus, DG access point, and load access point to obtain the phase voltage and current phasors, and then use the symmetrical component method to calculate the sequence components of the phase voltage and current. Based on the sequence components of the phase voltage and current, calculate the voltage and current of the fault phase and the phase angle difference between the two.

[0057] For Figure 1 The simple distribution line shown in the figure, when a single-phase grounding fault occurs in the distribution network containing DG, it will transition from a short transient process to a steady-state process. The impedance method requires the measurement of the steady-state voltage and current of the distribution network containing DG. The present invention uses a π-type equivalent lumped parameter circuit to analyze the steady-state distribution network containing DG with fault operation. When a single-phase grounding fault occurs in a simple line of the distribution network, its equivalent circuit is as follows Figure 1 shown.

[0058] Assume that the distance between the fault location point F and the head end point M is x, the positive direction of the positive sequence current is from point M to the end point N, and the positive direction of the negative sequence current and the zero sequence current is from point F to point M and point N. Through the symmetrical component method, the voltage and current data measured at the head end point M can be used to derive the three-sequence voltage and zero-sequence current at point F, which can be expressed by the following formula:

[0059]

[0060] In the formula, They are the three-sequence voltage phasors at point F; They are the three-sequence voltage phasors measured at the head end point M respectively; are the three-sequence current phasors measured at the head end point M; y1, y2, y0 represent the three-sequence admittance per unit length of the line; z1, z2, z0 represent the three-sequence impedance per unit length of the line, is the zero-sequence current phasor at point F, is the zero-sequence current phasor on the left side of point F, is the zero-sequence current phasor on the right side of point F, and L is the total length of the line.

[0061] From equations (1) and (2), we can know that the voltage and current of the fault phase (assuming it is phase A) at point F can be expressed by the following formula:

[0062]

[0063] In the formula, is the voltage of the fault phase, is the current of the fault phase.

[0064] Assuming the phase angle difference between the fault phase voltage and current is θ, it can be expressed by the following formula:

[0065]

[0066] According to the phase boundary conditions of single-phase grounding fault, if the line is grounded by pure resistance, the voltage and current phase quantities at the fault point are in phase, that is, θ=0.

[0067] Step 4: Read the distribution network topology information of the fault point. If the distribution network is a single-type line, calculate the fault distance based on the fault phase voltage, current and the phasor angle difference between the voltage and current of the fault phase.

[0068] In a preferred but non-limiting embodiment of the present invention, step 4 specifically comprises:

[0069] Starting from the beginning of the line, set a small initial step length x (for example, 10m), and increase the initial step length x continuously, each time increasing a set step length increment (such as 5m) until it is equal to the total length L of the line; each time the step length is increased, use equations (1) to (4) in step 3 to calculate the fault phase voltage and current phasors at x, and calculate the phasor angle difference θ between the two. That is, after traversing the entire line, a series of θ can be obtained, and the x corresponding to the minimum θ is the fault distance.

[0070] Step 5: If the line where the fault point is located is a mixed type line distribution network, use formula (1) to formula (6) to calculate the fault distance.

[0071] In a preferred but non-limiting embodiment of the present invention, step 5 specifically comprises:

[0072] When a single-phase grounding fault occurs in the hybrid line of the distribution network, the fault diagram is as follows: Figure 2 As shown, in Figure 2 In the example, the line MP section and the line PN section are two distribution lines with different parameters. MP , L PN is the length of the two lines, L is the total length of the mixed line, and P is the boundary between the two lines.

[0073] Similar to the calculation process of the simple line, when a hybrid line fault occurs, we also start from the beginning of the line, set a smaller initial step size, and use equations (1) to (4) in step 3 to calculate the fault phase voltage and current phasors at x, and calculate the phasor angle difference θ between the two. It should be noted that when x≤L MP When x>L, the MP section line parameters and equations (1) to (4) are used to calculate the fault phase voltage and current phasor angle difference θ at x. MP When calculating the voltage and current of each sequence at point P, it is necessary to calculate the voltage and current of each sequence at point x using the line parameters of the PN segment, starting from point P. It can be expressed by the following formula:

[0074]

[0075] Where, y1′, y′2, y′0 represent the third-sequence admittance per unit length of the PN line; z1′, z′2, z′0 represent the third-sequence impedance per unit length of the PN line; They represent the three-sequence voltage phasors of the line boundary point P respectively; They represent the three-sequence current phasors of the line boundary point P respectively; L MP It is the length of the line from point M at the beginning of the line to point P at the dividing point.

[0076] Finally, based on the sequence voltages and currents obtained from equations (5) and (6), the voltage, current and phase angle difference θ of the fault phase of the PN segment line are calculated through equations (3) and (4). Similarly, after traversing the entire hybrid line, a series of θ can be obtained, and the x corresponding to the minimum value of θ is the fault distance.

[0077] Step 6: If the line where the fault is located is a distribution network with a load branch, the fault distance is calculated using formula (1), formula (4), formula (7) and formula (8).

[0078] When a single-phase ground fault occurs on a main line with a single load branch, the network diagram is as follows: Figure 3 As shown. Figure 3In the figure, the black arrow indicates the positive sequence current direction; the red arrow indicates the negative sequence and zero sequence current direction. The present invention assumes that there is a measuring device such as FTU or DTU at the head end of the load branch, and each measuring device can perform synchronous measurement through GPS or Beidou to obtain the voltage and current phasors of each measuring point.

[0079] For a distribution network with a single load branch, the calculation starts from the head end of the fault line (point M), and the calculation process before the branch point (point A) is the same as that of a simple line. When calculating to the branch point (point A), the current of the branch needs to be considered, and the main line current on the right side of point A can be calculated, which can be expressed by the following formula:

[0080]

[0081] In the formula, Represent the three-sequence current phasors on the right side of point A The three-sequence current phasors on the left side of point A respectively; They represent the three-sequence current phasors at the head end of branch AB respectively.

[0082] The voltage and current of the fault phase are calculated using formula (3), which can be expressed as follows:

[0083]

[0084] Continue scanning the line. The voltage of the fault phase is calculated in the same way as the single-type line. The current of the fault phase is calculated using formula (8). Formula (4) is used to calculate θ. After traversing the trunk line on the right side of the branch point, a series of θ can be obtained. The x corresponding to the minimum value is the fault distance.

[0085] When a single-phase ground fault occurs on a main line with multiple load branches, the network diagram is as follows: Figure 4 As shown, Figure 4 The current in is the zero sequence current.

[0086] For a distribution network with multiple load branches, that is, when there is more than one load branch in the distribution network, the voltage and current should be calculated to the head end of the fault line first. From the above, the calculation formula for the positive and negative zero-sequence voltage at point A and the current flowing from point A to the fault point can be obtained as follows:

[0087]

[0088] In the formula, They are the three-sequence voltage phasors at point A; They are the three-sequence voltage phasors measured at the head end point M respectively; are the three-sequence current phasors measured at the head end point M; y1, y2, y0 represent the three-sequence admittance per unit length of the line; z1, z2, z0 represent the three-sequence impedance per unit length of the line; L MA , L AB Respectively represent the length of line MA segment and line AB segment; It is the zero-sequence current flowing from point A to the fault point.

[0089] The positive and negative sequence currents flowing from point A to the fault point can be calculated by a similar method. Therefore, the three-sequence voltage at the fault point and the zero-sequence current flowing into the fault point from the power supply side can be calculated by formula (9).

[0090] From the symmetrical component method, we know that in the zero-sequence network, the line section DN and the line section DE are equivalent to parallel lines. Considering that the equivalent end node of the two lines in parallel is the H node, similarly, Y0 and Z0 are the sum of the zero-sequence admittance and impedance of the line, so:

[0091]

[0092] In the formula, is the zero sequence current at point D, Z FH0 is the zero-sequence impedance of the line segment at point FH, Y FH0 is the zero-sequence admittance of the FH section of the line, is the zero-sequence voltage at point F of the line.

[0093] Among them, the calculation of the zero-sequence voltage at the branch point D is taken as

[0094]

[0095] Where Y FD0 is the zero-sequence admittance of the line DF section, Y DN0 is the zero-sequence admittance of the line DN section, Y DE0 is the zero-sequence admittance of line section DE, Z DN0 is the zero-sequence impedance of the line DN section, Z DE0 is the zero-sequence impedance of line section DE, Z FD0 is the zero-sequence impedance of line section DF.

[0096] In summary, when fault distance measurement is performed on multi-branch lines, the steady-state signal should be measured through the first-section measurement device, and the sequence voltage and current of each branch node should be calculated through a distributed parameter model. The equivalent resistance of the line after the fault point should be calculated through series-parallel methods, and finally converted into a simple network for solution.

[0097] Step 7: If the line where the fault point is located is a distribution network containing a distributed generation branch, the fault distance is calculated using formula (1), formula (4), formula (8) and formula (13).

[0098] When a distribution line with a distributed power generation branch fails, the fault network diagram is as follows: Figure 5 As shown. Figure 5 In the figure, the black arrow indicates the direction of positive sequence current; the red arrow indicates the direction of negative sequence and zero sequence current.

[0099] The present invention also assumes that there is a measuring device such as FTU or DTU at the head end of the distributed power supply branch, and each measuring device can perform synchronous measurement through GPS or Beidou to obtain the voltage and current phasors of each measuring point.

[0100] The calculation process is similar to that of the distribution line with load branches. The main difference is that the positive sequence current direction of the distributed generation branch is opposite, which can be expressed by formula (13):

[0101]

[0102] In the formula, They represent the three-sequence current phasors on the right side of point A respectively; The three-sequence current phasors on the left side of point A respectively; They represent the three-sequence current phasors at the head end of branch AB respectively.

[0103] After traversing line AN, the voltage of the fault phase is calculated in the same way as that of a single type of line. The current of the fault phase is calculated using formula (13). Using formula (4), a series of θ can be obtained. The x corresponding to the minimum value of θ is the fault distance.

[0104] The second embodiment of the present invention provides a single-ended impedance distance measurement system for single-phase ground fault of a distribution line including a DG, comprising:

[0105] Data entry module, used to enter necessary parameters into the device;

[0106] Fault detection module, used to monitor the zero-sequence voltage of the equipment and determine whether a single-phase grounding fault occurs;

[0107] The fault distance measurement module is used to calculate the fault distance of the distribution network containing distributed power sources when a fault occurs.

[0108] In the third embodiment of the present invention, the method described in the first embodiment is verified by combining specific data. The simulation model is as follows: Figure 6 As shown, the line voltage level is 10kV.

[0109] The positive and negative sequence parameters of the line per unit length are:

[0110] R 1,2 =1.23×10 -4 Ω / m

[0111] L 1,2 =2.292×10 -7 H / m

[0112] C 1,2 =2.84×10 -10 F / m

[0113] The zero sequence parameters are:

[0114] R0=1.23×10 -4 Ω / m;

[0115] L0=9.167×10 -7 H / m

[0116] C0=2.58333×10 -10 F / m

[0117] Assume that the total length of the trunk line is 5 km, the load branch and distributed power generation branch are both 2 km, and the fault phase is phase A.

[0118] The ground resistance is 10Ω and the fault distance is 500m

[0119] The calculated voltage and current sequence components at the line head end are:

[0120]

[0121] Taking 1m as the step length, the phase angle difference of each calculation point is calculated as follows: Figure 7 As shown, it can be seen that the corresponding fault distance when the phase angle difference is the smallest is 493m, and the error is only 7m.

[0122] The grounding resistance is 10Ω and the fault distance is 3000m.

[0123] Also using 1m as the step length, the phase angle difference results of each calculation point are calculated as follows Figure 8 As shown, it can be seen that the corresponding fault distance when the phase angle difference is the smallest is 3001m, and the error is only 1m.

[0124] The ground resistance is 500Ω and the fault distance is 3000m

[0125] Also using 1m as the step length, the phase angle difference results of each calculation point are calculated as follows Fig. 9 As shown, it can be seen that the corresponding fault distance when the phase angle difference is the smallest is 2999m, and the error is only 1m.

[0126] In order to analyze the applicability and error of the model when the fault grounding resistance is different and the fault distance is different, the fault point is set at 500, 1000, 2000, 3000, and 4500m from the line head end detection device in the model; and the grounding resistance is set to 10, 500, 1000, and 2000Ω. The calculation results are shown in Table 1.

[0127] Table 1 Single-phase ground fault distance measurement results for load branches and distributed generation branches

[0128]

[0129] It can be seen from the above table that when a single-phase grounding fault occurs in a distribution line containing distributed power sources and load branches, under the influence of different fault distances and grounding resistances, the model has a good ranging effect, with the maximum absolute error of only 48m, the maximum relative error of 9.6%, and the average relative error of 2.03%. This shows that the method proposed in the present invention has a good ranging effect and is practical.

[0130] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A single-ended impedance distance measurement method for single-phase ground fault of a distribution line containing DG, characterized in that: include: Enter parameters to the distance measurement center. When a single-phase grounding fault occurs on the distribution line containing DG, the zero-sequence voltage of the distribution line containing DG increases, and it is judged that a single-phase grounding fault occurs, and the fault distance measurement calculation is started; The sequence components of voltage and current at the fault point are calculated using the symmetrical component method; Based on the sequence components of the voltage and current at the fault point, the phasor angle difference between the voltage and current of the fault phase of the line is calculated; The fault distance of the distribution line containing DG is determined based on the phasor angle difference.

2. A single-ended impedance distance measurement method for single-phase ground fault of a distribution line containing DG as claimed in claim 1, characterized in that: The process of determining the fault distance includes: Starting from the beginning of the line, an initial step length x is set, and the initial step length x is continuously increased, each time by a set step length increment until it is equal to the total length L of the line; each time the step length is increased, the fault phase voltage and fault phase current at the current step length are calculated, and the phase angle difference θ between the two is calculated. The step length corresponding to the minimum value of all calculated angle differences is the fault distance.

3. A single-ended impedance distance measurement method for single-phase ground fault of a distribution line containing DG as claimed in claim 2, characterized in that: The phase angle difference θ can be expressed by the following formula: In the formula, is the voltage of the fault phase, is the current of the fault phase.

4. A single-ended impedance distance measurement method for single-phase ground fault of a distribution line containing DG as claimed in claim 3, characterized in that: If the line where the fault point is located is a single type line or a mixed type line, the voltage and current of the fault phase can be expressed by the following formula: In the formula, is the voltage of the fault phase, are the three-sequence voltage phasors of the fault point, is the zero-sequence current phasor at the fault point, is the current of the fault phase.

5. A single-ended impedance distance measurement method for single-phase ground fault of a distribution line containing DG as claimed in claim 3, characterized in that: If the line where the fault point is located is a distribution line with a load branch or a distribution line with a distributed power generation branch, the voltage and current of the fault phase can be expressed by the following formula: In the formula, are the three-sequence voltage phasors of the fault point, They represent the three-sequence current phasors on the right side of point A respectively.

6. A single-ended impedance distance measurement method for single-phase ground fault of a distribution line containing DG as claimed in claim 4, characterized in that: If the line at the fault point is a single type of line, the voltage sequence component and current sequence component of the fault point can be expressed by the following formula: In the formula, They are the three-sequence voltage phasors of the fault point respectively; They are the three-sequence voltage phasors measured at the endpoints of the head end respectively; are the three-sequence current phasors measured at the end points of the head end; y1, y2, y0 represent the three-sequence admittance of the line per unit length; z1, z2, z0 represent the three-sequence impedance of the line per unit length, is the zero-sequence current phasor at the fault point, is the zero-sequence current phasor on the left side of the fault point, is the zero-sequence current phasor on the right side of point F, x is the distance between the fault point and the first end of the line, and L is the total length of the line.

7. A single-ended impedance distance measurement method for single-phase ground fault of a distribution line containing DG as claimed in claim 4, characterized in that: If the line where the fault point is located is a mixed type line distribution network, the voltage sequence component and current sequence component of the fault point can be expressed by the following formula: In the formula, are the three-sequence voltage phasors of the fault point respectively; y1′, y′2, y′0 represent the three-sequence admittance per unit length of the PN section line respectively; z1′, z′2, z′0 represent the three-sequence impedance per unit length of the PN section line respectively; They represent the three-sequence voltage phasors of the line boundary point P respectively; They represent the three-sequence current phasors of the line boundary point P respectively; L MP It is the length of the line from point M at the beginning of the line to point P at the dividing point.

8. A single-ended impedance distance measurement method for single-phase ground fault of a distribution line containing DG as claimed in claim 5, characterized in that: If the line where the fault point is located is a distribution line with a single load branch, the voltage sequence component of the fault point is the same as that of a single type of line. When the fault point is located on the left side of the branch point, the sequence component of the fault point current is the same as that of a single type of line. When the fault point is located on the right side of the branch point, the three-sequence components of the fault point current are calculated. The three-sequence components of the fault point current can be expressed by the following formula: In the formula, They represent the three-sequence current phasors on the right side of the dividing point A, The three-sequence current phasors on the left side of the demarcation point A respectively; They represent the three-sequence current phasors at the head end of branch AB respectively.

9. A single-ended impedance distance measurement method for single-phase ground fault of a distribution line containing DG as claimed in claim 5, characterized in that: If the line where the fault point is located is a distribution line with more than one load branch, the voltage sequence component at the fault point can be expressed by the following formula: In the formula, They are the three-sequence voltage phasors at point A; They are the three-sequence voltage phasors measured at the head end point M respectively; are the three-sequence current phasors measured at the head end point M; y1, y2, y0 represent the three-sequence admittance per unit length of the line; z1, z2, z0 represent the three-sequence impedance per unit length of the line; L MA Indicates the length of the MA segment of the line.

10. A single-ended impedance distance measurement method for single-phase ground fault of a distribution line containing DG as claimed in claim 5, characterized in that: If the line where the fault point is located is a distribution line containing a distributed power generation branch, the voltage sequence component of the fault point is the same as that of a single type of line, and the current sequence component of the fault point can be expressed by the following formula: In the formula, They represent the three-sequence current phasors on the right side of the dividing point A, The three-sequence current phasors on the left side of point A respectively; They represent the three-sequence current phasors at the head end of branch AB respectively.

11. A single-ended impedance distance measurement system for single-phase ground fault of a distribution line containing DG, running a single-ended impedance distance measurement method for single-phase ground fault of a distribution line containing DG according to any one of claims 1 to 10, characterized in that: include: Data entry module, used to enter necessary parameters into the device; Fault detection module, used to monitor the zero-sequence voltage of the equipment and determine whether a single-phase grounding fault occurs; A phase angle calculation module, used to calculate the phase angle difference between the voltage and current of the fault phase of the distribution line when a fault occurs; The fault distance measurement module is used to determine the fault distance of the distribution line containing DG based on the phase angle difference.

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