A method and device for fault location measurement in multi-branch power distribution network based on traveling waves

Abstract

The present invention discloses a method and device for fault distance measurement of a multi-branch power distribution network based on traveling waves, and relates to the technical field of power grid fault distance measurement; the device comprises a fault voltage traveling wave extraction device and a controller, a fault voltage traveling wave extraction device is arranged at the end point of a trunk line, and a fault voltage traveling wave extraction device is arranged at an interval branch connection point; the method comprises a distance measurement step, the fault voltage traveling wave extraction device obtains the arrival time of the fault voltage traveling wave arriving at the fault voltage traveling wave extraction device, and the arrival time comprises a zero mode time t0 and an α mode time t α According to the arrival time, based on the section location algorithm, it is known that the fault point is located on the branch line between two adjacent fault voltage traveling wave extraction devices. According to the zero mode time t0 and the α mode time t α The distance to the fault point is calculated by the time difference Δt; the fault voltage traveling wave extraction device and the controller are arranged at intervals to achieve the fault point distance measurement in the branch line without the fault voltage traveling wave extraction device, thereby reducing the cost.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid fault distance measurement, and in particular to a multi-branch power distribution network fault distance measurement method and device based on traveling waves. Background Art

[0002] In recent years, traveling wave fault location technology has made great progress, and the fault location of two points in a straight line in the power grid can be accurately located to the order of ten meters. However, due to the complex grid topology and diverse load types in the distribution network, it is difficult to apply a single fault location technology. How to ensure the accuracy of fault distance measurement while controlling the distance measurement cost has become a practical problem that needs to be solved.

[0003] The authorization announcement number is CN 103901324 B, and the name is a combined distance measurement method for hybrid lines of distribution networks based on single-end fault information. It can effectively extract the initial wave head and various reflected wave heads of the traveling wave at the time of the fault, and is used in occasions where double-end traveling wave distance measurement is not available to achieve accurate fault distance measurement, thus supplementing the shortcomings of the existing hybrid line fault distance measurement of distribution networks. On the basis of realizing fault distance measurement by current traveling waves, the distance measurement results of voltage traveling waves are comprehensively considered to improve the reliability and accuracy of distance measurement.

[0004] The authorization announcement number is CN 109581149 B, and the name is "Traveling wave ranging method and system under arc suppression coil parallel small resistance grounding mode". By injecting signals during live operation, there is no need to increase primary equipment investment, and the existing parallel small resistor can be used to complete the ranging. It requires fewer devices and does not require synchronous sampling, which reduces the overall cost and significantly improves the accuracy of ranging.

[0005] Combining the above two patent documents and the existing technical solutions, the inventors analyzed and found that there are the following technical problems in the existing technical solutions. The current fault distance measurement adopts the multi-terminal traveling wave fault distance measurement method, and fault distance measurement devices are installed at all branch points and both ends of the main line. After the fault occurs, according to the fault traveling waves collected by each distance measurement device, the section positioning method is used to know the section where the fault point is located, that is, first know whether the fault point is located on the main line or the branch line, and then use the double-terminal traveling wave fault distance measurement method to determine the distance of the main line fault point, and use the modulus wave velocity difference method to locate the branch line fault point. In this distance measurement method, all fault distance measurement devices are synchronized by GPS, and each fault distance measurement device obtains the time when the fault traveling wave arrives at the fault distance measurement device and calculates the distance between the fault point and the fault distance measurement device. The principle is simple and the distance measurement accuracy is high, but a fault distance measurement device needs to be installed at the branch point of each branch line, which invisibly increases the distance measurement cost.

[0006] Existing technical problems and considerations:

[0007] How to solve the technical problem of high cost of measuring distance to fault points in power grid. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a multi-branch power distribution network fault distance measurement method and device based on traveling waves, so as to solve the technical problem of power grid fault point distance measurement.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is: a multi-branch power distribution network fault distance measurement device based on traveling waves includes a fault voltage traveling wave extraction device and a controller, the power distribution network is a trunk line with branch lines, the connection between the branch line and the trunk line is a branch connection point, a fault voltage traveling wave extraction device is arranged at the end point of the trunk line, and a fault voltage traveling wave extraction device is arranged at the interval branch connection point, and the controller is respectively connected to and communicates with each fault voltage traveling wave extraction device.

[0010] A further technical solution is: further comprising a distance measuring module, the controller being a single chip microcomputer or a computer, the distance measuring module being a program module, for the fault voltage traveling wave extraction device to obtain the arrival time of the fault voltage traveling wave arriving at the fault voltage traveling wave extraction device and send it to the controller, the arrival time including the zero mode time t0 and the α mode time t α , the controller obtains the arrival time, and based on the arrival time, it is known that the fault point is located on the branch line between two adjacent fault voltage traveling wave extraction devices based on the section positioning algorithm. The controller calculates the arrival time based on the zero mode time t0 and the α mode time t α The distance to the fault point is calculated by the time difference Δt.

[0011] A further technical solution is that the fault voltage traveling wave extraction device includes a first fault voltage traveling wave extraction device and a second fault voltage traveling wave extraction device, a branch connection point between a branch line and a trunk line is a second reference point on the trunk line, a first fault voltage traveling wave extraction device is arranged on one side of the second reference point, and a second fault voltage traveling wave extraction device is arranged on the other side of the second reference point, the position of the first fault voltage traveling wave extraction device on the trunk line is the first reference point, the position of the second fault voltage traveling wave extraction device on the trunk line is the third reference point, the first reference point is the end point or branch connection point of the trunk line, the third reference point is the end point or branch connection point of the trunk line, and the line on the trunk line between the first reference point and the third reference point is the main line.

[0012] A further technical solution is that the distance measurement module is also used for the controller to calculate the distance to the fault point according to equation (3) and equation (10).

[0013] Δt=t0-t α (3)

[0014] In formula (3), the zero mode time t0 is the time when the zero mode reaches the traveling wave extraction device, unit is s; the α mode time t α is the time when the α mode reaches the traveling wave extraction device, in seconds; Δt is the time after the zero mode time t0 to the α mode time t α The time difference, unit is s;

[0015]

[0016] In formula (10), i is the reference point number, the value of i is 1 or 3, and the i-th reference point is the first reference point or the third reference point; L i is the distance from the fault point to the second reference point calculated with the i-th reference point as the distance measurement center, in meters; v0 is the zero modulus wave velocity, in meters per second; v α is the α-mode wave velocity, in m / s; Δt is the time from the zero-mode moment t0 to the α-mode moment t α The time difference to reach the i-th reference point, in seconds; l i It is the physical length of the trunk line between the i-th reference point and the second reference point, in meters.

[0017] A further technical solution is that the distance measuring module is also used for the controller to calculate the distance to the fault point according to the arrival time obtained by the fault voltage traveling wave extraction device closest to the fault point.

[0018] A further technical solution is that the ranging module is also used for the controller to obtain the distance from the fault point with the first reference point as the ranging center to the second reference point as the first fault distance, obtain the distance from the fault point with the third reference point as the ranging center to the second reference point as the second fault distance, and obtain the average value of the first fault distance and the second fault distance as the fault point distance, that is, sum the first fault distance and the second fault distance and divide it by 2.

[0019] A multi-branch distribution network fault distance measurement method based on traveling waves, based on the above-mentioned fault voltage traveling wave extraction device, includes a distance measurement step, the fault voltage traveling wave extraction device obtains the arrival time of the fault voltage traveling wave arriving at the fault voltage traveling wave extraction device, the arrival time includes the zero mode time t0 and the α mode time t α According to the arrival time, based on the section location algorithm, it is known that the fault point is located on the branch line between two adjacent fault voltage traveling wave extraction devices. According to the zero mode time t0 and the α mode time t α The distance to the fault point is calculated by the time difference Δt.

[0020] A further technical solution is that: in the distance measurement step, the fault point distance is calculated according to formula (3) and formula (10), or the fault point distance is calculated according to the arrival time obtained by the fault voltage traveling wave extraction device closest to the fault point, or the average value of the first fault distance and the second fault distance is obtained as the fault point distance.

[0021] A multi-branch distribution network fault distance measuring device based on traveling waves comprises a memory, a processor and a computer program stored in the memory and executable on the processor. The processor implements the above corresponding steps when executing the computer program.

[0022] A multi-branch distribution network fault distance measuring device based on traveling waves comprises a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the above corresponding steps are implemented.

[0023] The beneficial effects of adopting the above technical solution are:

[0024] A multi-branch distribution network fault distance measurement device based on traveling waves includes a fault voltage traveling wave extraction device and a controller. The distribution network is a trunk line with branch lines. The connection between the branch line and the trunk line is a branch connection point. A fault voltage traveling wave extraction device is arranged at the end point of the trunk line, and a fault voltage traveling wave extraction device is arranged at the interval branch connection point. The controller is respectively connected to and communicates with each fault voltage traveling wave extraction device. This technical solution realizes fault point distance measurement in a branch line without a fault voltage traveling wave extraction device through the interval-arranged fault voltage traveling wave extraction devices and controllers, thereby reducing costs.

[0025] A multi-branch distribution network fault distance measurement method based on traveling waves, based on the above-mentioned fault voltage traveling wave extraction device, includes a distance measurement step, the fault voltage traveling wave extraction device obtains the arrival time of the fault voltage traveling wave arriving at the fault voltage traveling wave extraction device, the arrival time includes the zero mode time t0 and the α mode time t α According to the arrival time, based on the section location algorithm, it is known that the fault point is located on the branch line between two adjacent fault voltage traveling wave extraction devices. According to the zero mode time t0 and the α mode time t α The distance to the fault point is calculated by the time difference Δt. The technical solution realizes the distance measurement of the fault point in the branch line of the fault-free voltage traveling wave extraction device through the distance measurement step, etc., thereby reducing the cost.

[0026] Please refer to the detailed description of the specific implementation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a distribution diagram of the fault voltage traveling wave extraction device in Example 1 of the present invention;

[0028] Figure 2 It is the distribution diagram of the multi-branch power supply model;

[0029] Figure 3 It is the distribution diagram of the fault occurring on the main distribution line;

[0030] Figure 4 It is the distribution diagram of the fault occurring in the branch with the distance measuring device;

[0031] Figure 5 It is the distribution diagram of the fault occurring in the branch without distance measuring device;

[0032] Figure 6 It is the distribution diagram of the fault occurring at the end of the line;

[0033] Figure 7 is a flow chart of the fault location method;

[0034] Figure 8 It is the data flow diagram of fault location;

[0035] Fig. 9 It is the distribution diagram of the simulation model of the AE section;

[0036] Fig.10 It is the distribution diagram of the IB section simulation model;

[0037] Fig.11 is the first screenshot;

[0038] Fig.12 is the second screenshot;

[0039] Fig.13 is the third screenshot;

[0040] Fig.14 It’s the fourth screenshot;

[0041] Fig.15 It is the fifth screenshot;

[0042] Fig.16 It is the sixth screenshot;

[0043] Fig.17 It’s the seventh screenshot;

[0044] Fig.18 It is the eighth screenshot;

[0045] Fig.19 It’s the ninth screenshot;

[0046] Fig. 20 It’s the tenth screenshot;

[0047] Fig.21 It’s the eleventh screenshot;

[0048] Fig. 22 It is the twelfth screenshot;

[0049] Fig.23 It’s the thirteenth screenshot;

[0050] Fig.24 It is the fourteenth screenshot;

[0051] Fig.25 It’s the fifteenth screenshot;

[0052] Fig.26 It is the sixteenth screenshot;

[0053] Fig. 27 It is the seventeenth screenshot;

[0054] Fig.28 It is the eighteenth screenshot;

[0055] Fig.29 It’s the nineteenth screenshot;

[0056] Fig.30 This is the twentieth screenshot. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0058] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0059] Embodiment 1:

[0060] like Figure 1As shown, the present invention discloses a multi-branch distribution network fault ranging device based on traveling waves, including a fault voltage traveling wave extraction device, a controller and a ranging module. When the distribution line is a trunk line, the fault voltage traveling wave extraction device is distributed at the end point of the trunk line. When the trunk line has a branch line, the connection between the branch line and the trunk line is a branch connection point. The fault voltage traveling wave extraction devices are distributed at intervals at the branch connection points, and the controller is wirelessly connected to and communicates with each fault voltage traveling wave extraction device respectively.

[0061] like Figure 1 As shown, the fault voltage traveling wave extraction device includes first to fourth fault voltage traveling wave extraction devices, the first fault voltage traveling wave extraction device is installed at one end A of the trunk line, that is, the first node, the fourth fault voltage traveling wave extraction device is installed at the other end B of the trunk line, that is, the sixth node, the second fault voltage traveling wave extraction device is installed at E of the trunk line, that is, the third node, the third fault voltage traveling wave extraction device is installed at I of the trunk line, that is, the fifth node, and no fault voltage traveling wave extraction device is installed at D of the trunk line, that is, the second node, and H of the trunk line, that is, the fourth node.

[0062] like Figure 1 As shown, the controller calculates the distance to the fault point according to the arrival time obtained by the fault voltage traveling wave extraction device closest to the fault point, and the fault voltage traveling wave extraction device closest to the fault point is the first fault voltage traveling wave extraction device or the third fault voltage traveling wave extraction device.

[0063] The branch connection point D between the first branch line CD and the main line is the second reference point on the main line, the first fault voltage traveling wave extraction device is installed on one side of the second reference point, and the second fault voltage traveling wave extraction device is installed on the other side of the second reference point, the position A of the first fault voltage traveling wave extraction device on the main line is the first reference point, and the position E of the second fault voltage traveling wave extraction device on the main line is the third reference point, the first reference point is the endpoint of the main line, the third reference point is the branch connection point of the main line, and the line on the main line between the first reference point and the third reference point is the main line AE.

[0064] The ranging module is a program module, which is used by the fault voltage traveling wave extraction device to obtain the arrival time of the fault voltage traveling wave at the fault voltage traveling wave extraction device and send it to the controller. The arrival time includes the zero mode time t0 and the α mode time t α , the controller obtains the arrival time, and based on the arrival time, it is known that the fault point is located on the branch line between two adjacent fault voltage traveling wave extraction devices based on the section positioning algorithm. The controller calculates the distance to the fault point based on the arrival time obtained by the fault voltage traveling wave extraction device closest to the fault point. The controller calculates the distance to the fault point based on the arrival time after the zero mode time t0 and the α mode time t αThe distance to the fault point is calculated by the time difference Δt. That is, the controller calculates the distance to the fault point according to equations (3) and (10).

[0065] Δt=t0-t α (3)

[0066] In formula (3), the zero mode time t0 is the time when the zero mode reaches the traveling wave extraction device, unit is s; the α mode time t α is the time when the α mode reaches the traveling wave extraction device, in seconds; Δt is the time after the zero mode time t0 to the α mode time t α The time difference, in seconds.

[0067]

[0068] In formula (10), i is the reference point number, the value of i is 1 or 3, and the i-th reference point is the first reference point or the third reference point; L i is the distance from the fault point to the second reference point calculated with the i-th reference point as the distance measurement center, in meters; v0 is the zero modulus wave velocity, in meters per second; v α is the α-mode wave velocity, in m / s; Δt is the time from the zero-mode moment t0 to the α-mode moment t α The time difference to reach the i-th reference point, in seconds; l i It is the physical length of the trunk line between the i-th reference point and the second reference point, in meters.

[0069] Among them, the controller is a single-chip microcomputer, and the fault voltage traveling wave extraction device, the single-chip microcomputer itself and the corresponding communication connection technology are existing technologies and will not be described in detail here.

[0070] Embodiment 2:

[0071] The present invention discloses a multi-branch distribution network fault distance measurement method based on traveling waves, based on the device of embodiment 1, comprising the steps of:

[0072] The fault voltage traveling wave extraction device obtains the arrival time of the fault voltage traveling wave at the fault voltage traveling wave extraction device and sends it to the controller. The arrival time includes the zero mode time t0 and the α mode time t α , the controller obtains the arrival time, and based on the arrival time, it is known that the fault point is located on the branch line between two adjacent fault voltage traveling wave extraction devices based on the section positioning algorithm. The controller calculates the distance to the fault point based on the arrival time obtained by the fault voltage traveling wave extraction device closest to the fault point. The controller calculates the distance to the fault point based on the arrival time after the zero mode time t0 and the α mode time t α The distance to the fault point is calculated by the time difference Δt. That is, the controller calculates the distance to the fault point according to equations (3) and (10).

[0073] Embodiment 3:

[0074] The present invention discloses a multi-branch distribution network fault distance measuring device based on traveling waves, comprising a memory, a processor and a computer program stored in the memory and executable on the processor. The processor implements the steps of embodiment 2 when executing the computer program.

[0075] Embodiment 4:

[0076] The present invention discloses a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps in Embodiment 2 are implemented.

[0077] Embodiment 5:

[0078] Embodiment 5 differs from Embodiment 1 in that the distance measurement module is also used for the controller to obtain the distance from the fault point with the first reference point as the distance measurement center to the second reference point as the first fault distance, obtain the distance from the fault point with the third reference point as the distance measurement center to the second reference point as the second fault distance, and obtain the average value of the first fault distance and the second fault distance as the fault point distance, that is, sum the first fault distance and the second fault distance and divide the sum by 2.

[0079] Compared with the above embodiment, the controller may also be a computer.

[0080] Embodiment 6:

[0081] Embodiment 6 is different from Embodiment 2 in that the controller is a computer, and the calculation is performed manually.

[0082] The present invention discloses a multi-branch distribution network fault distance measurement method based on traveling waves, comprising the steps of:

[0083] The fault voltage traveling wave extraction device obtains the arrival time of the fault voltage traveling wave at the fault voltage traveling wave extraction device and sends it to the controller. The arrival time includes the zero mode time t0 and the α mode time t α , the controller obtains the arrival time, the staff knows the arrival time through the controller, and based on the arrival time based on the section positioning algorithm, it is known that the fault point is located on the branch line between two adjacent fault voltage traveling wave extraction devices. The staff calculates the distance to the fault point based on the arrival time obtained by the fault voltage traveling wave extraction device closest to the fault point, that is, based on the zero mode time t0 after the α mode time t α The distance to the fault point is calculated by the time difference Δt. That is, the distance to the fault point is calculated according to formula (3) and formula (10).

[0084] Purpose of this application:

[0085] Aiming at the complex structure of current distribution network and the diverse fault location technologies that cannot be universally applied to various types of power supply networks, a new fault location method and traveling wave extraction device configuration scheme are proposed, which can reduce the required number of traveling wave extraction devices while ensuring the ranging accuracy.

[0086] Technical contributions of this application:

[0087] Technical methods for fault location and configuration scheme of traveling wave extraction device.

[0088] Technical solution description:

[0089] The current fault distance measurement adopts the multi-terminal traveling wave fault distance measurement method, that is, fault distance measurement devices are installed at all branch points and both ends of the main line. After the fault occurs, the fault point of the main line is determined by the double-terminal traveling wave fault distance measurement method based on the fault traveling waves collected by each distance measurement device; the fault point of the branch line is located by the modulus wave velocity difference method. This distance measurement method has a simple principle and high distance measurement accuracy, but it is necessary to install a fault distance measurement device at the branch point of each branch line and synchronize it with GPS, which invisibly increases the distance measurement cost.

[0090] Fault voltage traveling wave. Most distribution networks are systems with ungrounded neutral points. When a grounding fault occurs, the current traveling wave is not obvious and the waveform is relatively smooth, making it difficult to analyze its waveform. Therefore, the fault voltage traveling wave is used.

[0091] Aiming at the current ranging scheme, a fault location method based on double-end-line zero-mode wave velocity difference is proposed.

[0092] like Figure 2 As shown in Figure 1, this is a common multi-branch power supply model in the power grid.

[0093] like Figure 2 As shown in the figure, AB is the trunk line, CD, EF, GH, and IK are all branch lines on the trunk line. l1~l9 are the physical lengths of each section of the transmission line shown in the figure. Different from the traditional method, voltage traveling wave extraction devices are only set at A, E, I, and B, that is, voltage traveling wave extraction devices are set at both sides of the line and at the end of the interval branch line, and GPS synchronization timing is performed. CD and GH are branch lines without ranging devices. The location of the single-phase grounding fault in this model is divided into the following four situations: fault in the trunk line, branch line fault with a fault ranging device, branch line fault without a fault ranging device, and fault at the end of the line.

[0094] According to the above fault classification, the transmission line structure of section AB can be further divided into three sections: AE, EI and IB. Due to the lack of branch lines in section IB, faults can only occur on the main distribution line. When a branch line is added to section IB, the topology will be the same as the previous two sections. The situation where the end line lacks a branch will be separately demonstrated in the subsequent analysis. Sections AE and EI have the conditions for the occurrence of three fault conditions (AE / EI main lines, EF / IK lines contain distance measuring devices, and CD / GH is a branch without a distance measuring device). The following takes section AE as an example for a detailed analysis.

[0095] 1) The fault occurs on the power distribution main line

[0096] like Figure 3 As shown in Figure 1, when the fault occurs in the AE section, that is, the fault occurs in the distribution trunk line.

[0097] The traveling wave head radiates from the fault point to both sides to the distance measuring device. By analyzing the fault traveling waves of A, E, I, and B, the fault can be located in the AE section. a If the first time reaches end A, the fault distance measurement is performed with A as the distance measurement center, and the time point T recorded by the distance measurement device E closest to A is used. E Perform calculations.

[0098] According to the double-terminal traveling wave fault distance measurement formula, the fault distance L1 from point A can be obtained as formula (1):

[0099]

[0100] In formula (1), L1 is the distance from the fault point to the traveling wave extraction device at A, in meters; T A is the time when the fault traveling wave reaches the traveling wave extraction device at A, in seconds; T E is the time when the fault traveling wave reaches the traveling wave extraction device at E, in seconds; v α is the α modulus wave velocity, in m / s; l1 is the physical length of the AD section transmission line, in m; is the physical length of the DE section transmission line, in m.

[0101] In formula (1), the α modulus wave velocity v α It is an important factor to ensure the accuracy of distance measurement. Therefore, the positive sequence voltage traveling wave of the fault voltage traveling wave after Clarke transformation is selected, that is, the α-mode voltage traveling wave velocity is selected for fault distance measurement.

[0102] In other sections, as long as the fault occurs in the main line, this method can be used for calculation. However, it should be noted that the farther the two distance measuring devices are apart, the more branches the fault traveling wave passes through before reaching the distance measuring point. The resulting traveling wave attenuation and loss may reduce the accuracy of traveling wave fault distance measurement. The nearest distance measuring point to the fault point should be used for measurement as much as possible.

[0103] The content in step 1) can be directly simplified to a two-terminal ranging method, which is a prior art.

[0104] 2) The fault occurs in the branch with the distance measuring device

[0105] like Figure 4 As shown, when a distribution branch (such as EF) containing a distance measuring device fails, the fault point situation.

[0106] The traveling wave fault distance measuring device at the branch starting point E is used to extract the fault traveling wave emitted by the fault point, and the positive sequence and zero sequence components of the voltage traveling wave, namely the α modulus and the zero modulus component, are extracted using the phase mode transformation theory. The fault distance is measured using the modulus wave velocity difference method. Assuming that the distance between the fault point and the E end is L2, the distance measurement formula is formula (2):

[0107]

[0108] In formula (2), L2 is the distance from the fault point to the traveling wave extraction device at E, in meters; v α is the α modulus wave velocity, unit is m / s; v0 is the zero modulus wave velocity, unit is m / s; Δt is the time difference, unit is s.

[0109] Δt=t0-t α (3)

[0110] In formula (3), t0 is the time when the zero mode reaches the traveling wave extraction device at the branch point E, in seconds; t α is the moment when the α mode arrives at the traveling wave extraction device at the branch point E, in seconds; the line mode, i.e., the α mode wave propagation speed is greater than the zero mode wave speed, and Δt is the time difference between the zero mode and the line mode arriving at the ranging point, in seconds.

[0111] The content in step 2) can be directly simplified to the modulus wave velocity difference ranging method, which is a prior art.

[0112] 3) The fault occurs in the branch without distance measuring device

[0113] like Figure 5 As shown, when a distribution branch without a distance measuring device (such as CD) fails, the fault point situation.

[0114] Since the voltage traveling wave extraction device is connected at the branch starting point D, the required fault traveling wave cannot be extracted, and the fault distance measurement devices on both sides need to be used for coordinated distance measurement.

[0115] After a fault occurs somewhere on branch CD, the fault traveling wave first reaches the D end and propagates to both sides of A and E. According to the principle of double-end traveling wave fault ranging, the fault distance measured with point A as the ranging center is l1, and the fault distance measured with point E as the ranging center is l3. Although the absolute distances of the ranging are different, they are only located to the branch point D, that is, only interval positioning can be performed, and the specific fault location point cannot be determined. At this time, the double-end-line zero-mode wave velocity difference method is used to locate the fault.

[0116] like Figure 8 As shown in the figure, A is taken as the ranging center to receive the fault voltage traveling wave emitted by the fault point, and phase mode transformation and wavelet analysis are performed on it to extract the arrival time of the α-mode and zero-mode voltage traveling waves, and the ranging is performed according to the traveling wave speeds of the two.

[0117] The ranging formula is formula (4):

[0118]

[0119] After simplification, we can get formula (5):

[0120]

[0121] In formula (5), L3 is the distance from the fault point to the branch point at D calculated with point A as the distance measurement center, in meters.

[0122] Similarly, the fault distance can be obtained by locating the fault with E as the center:

[0123]

[0124] In formula (6), L4 is the distance from the fault point to the traveling wave extraction device at D calculated with E as the ranging center, in meters.

[0125] In order to improve the ranging accuracy, the final ranging result takes the average value of the two, as shown in formula (7):

[0126]

[0127] In formula (7), L is the average value, unit is m.

[0128] This method can also use the fault distance measuring devices at H and B to measure the distance, or use the fault distance values ​​obtained by multi-point distance measuring devices to take the average value to calculate a more accurate fault location, which will not be analyzed in detail here.

[0129] The content in step 3) is an innovative point, which is equivalent to replacing the traveling wave extraction device at the end of the branch line with the traveling wave extraction devices on both sides.

[0130] 4) The fault occurs at the end of the line

[0131] like Figure 6 As shown in the figure, when the IB section at the end of the line fails, since this section of the line does not contain branch lines and there are fault distance measurement devices on both sides of I and B, the fault distance measurement method at this time can be simplified to ordinary double-end traveling wave fault distance measurement. When the IB section at the end of the line fails, the fault point situation.

[0132] If the wave head is at T B When the first one arrives at the B end, the fault distance measurement is performed with B as the distance measurement center, and the measured fault distance L5 is expressed as formula (8):

[0133]

[0134] In formula (8), L5 is the distance from the fault point to the traveling wave extraction device at B, in meters; T B is the time when the fault traveling wave reaches the traveling wave extraction device at B, in seconds; T I is the moment when the fault traveling wave reaches the traveling wave extraction device at location I, in s; l9 is the physical length of the IB section of the transmission line, in m.

[0135] The traveling wave velocity used in the above calculation is also the α-mode velocity.

[0136] In summary, after the distance measuring device is used to determine the section, the steps for determining the fault point in the four cases are as follows:

[0137] (1) When a fault occurs in the main line, the time it takes for the traveling wave to arrive at both sides is recorded using a distance measuring device, and then the α-mode wave velocity is calculated. The fault location can be obtained using the double-end distance measurement formula.

[0138] (2) When the fault occurs in a branch line containing a distance measuring device, the voltage traveling wave is extracted by the fault distance measuring device at the starting point of the branch and a phase-mode transformation is performed, and the fault is located according to the single-ended modulus wave velocity difference method.

[0139] (3) When the fault occurs in a branch line without a distance measuring device, the fault section is first located using the double-end distance measuring method on the main line; after locating the branch point, the double-end-line zero-mode wave velocity difference method is used to locate the fault point using any distance measuring points on both sides of the branch. The fault traveling wave received at the distance measuring point is subjected to phase-mode transformation, and the distance to the fault point is calculated based on the modulus wave velocity difference Δv and the time difference Δt. Finally, the distance l of the traveling wave transmission on the main line is subtracted to obtain the position of the fault point on the branch line.

[0140] (4) When the fault occurs at the end of a line without branches, since this section does not contain branch lines, the line fault distance measurement will be converted into a simple two-end traveling wave fault distance measurement. The specific calculation method can be calculated by referring to the fault situation of the distribution trunk line.

[0141] The ranging method in step 4) is the same as that in step 1), which is double-end fault ranging.

[0142] like Figure 7 As shown, the fault location method is simplified into a flow chart, which is a simplified flow chart of the double-end-line zero-mode wave velocity difference fault location method.

[0143] Assuming that there are n branch lines in the medium voltage distribution ring network, according to the traditional double-end traveling wave fault distance measuring device configuration scheme, that is, a distance measuring device is installed at the end of each line, a total of n+2 distance measuring devices are required. According to the distance measuring theory proposed in this paper, the number of distance measuring devices configured is expressed as formula (9):

[0144]

[0145] In formula (9), x is the number of required distance measuring devices, and n is the number of branch lines.

[0146] Compared with the traditional two-terminal traveling wave fault location method, the number of distance measurement devices is almost halved while ensuring the accuracy of traveling wave fault location, and the more branches there are, the more economical it is.

[0147] At the same time, the subway medium-voltage distribution ring network distance measurement algorithm proposed in this paper has reference significance for fault distance measurement of other types of distribution networks. When the topology of the power supply network is more complex, such as when there are many slave branch lines in the main branch line, the topology can be decomposed, and each level of branch line can be configured with a fault distance measurement device according to this model and the fault can be accurately located.

[0148] In addition, the determination of the zero-mode wave velocity in this distance measurement method has a great influence on the distance measurement accuracy of the modulus wave velocity difference method. The zero-mode wave velocity has obvious frequency-varying characteristics, and with the increase of the transmission line distance, it produces greater attenuation and loss. This is also an important reason why the modulus wave velocity difference method cannot be applied to long-distance line fault distance measurement. Many solutions have been proposed, such as combining the Li value of the zero-mode wave head and using iterative algorithms. However, due to the difficulty of calculation, the problem of zero-mode wave velocity change during long-distance transmission has not been well solved. Therefore, it is necessary to study and calculate the change of zero-mode wave velocity. In the subway medium-voltage distribution ring network, the length of the terminal branch is between several hundred meters and several kilometers. The application of zero-mode wave velocity has practical significance, which will be actually verified in the simulation experiment later.

[0149] Fault simulation:

[0150] Single-phase fault simulation analysis

[0151] like Fig. 9 As shown in the simplified model, the AE section contains three fault conditions.

[0152] like Fig. 9As shown, l1=5000m, l2=600m, l3=3000m, l4=700m.

[0153] like Fig.10 As shown, take the IB section (line end). l9 = 3000m.

[0154] Use Matlab / simulink platform to build Fig. 9 , Fig.10 The fault simulation model is set, the transition resistance value in the simulation model is set to 200Ω, the initial phase angle of the power supply is set to 0°, the simulation period is: 0.0s-0.1s, the sampling frequency is 5MHz, and the time when the single-phase grounding fault occurs is 0.02s.

[0155] 5.1 Single-phase fault simulation

[0156] 5.1.1 The fault occurs on the main distribution line

[0157] Assume that a single-phase grounding fault of phase B occurs 3 km away from point A. First, all distance measuring devices on the main line are used to locate the section and determine that the fault section is section AD. Then, the fault distance measuring devices at points A and E are used to locate and measure the specific fault point.

[0158] like Fig.11 As shown in Figure 1, the α-mode fault traveling wave received at point A. Fig.12 As shown in the figure, the wavelet transform d1 waveform received at point A. The d1 waveform is locally amplified near the 0.02s mutation point to locate the arrival time T of the first wave head of the α-mode fault traveling wave. A =0.020019s.

[0159] like Fig.13 As shown in Figure 1, the α-mode fault traveling wave received at point E. Fig.14 As shown, the wavelet transform d1 waveform received at point E. The arrival time T of the traveling wave head of the α-mode fault is E =0.020031s.

[0160] Select the positive sequence modulus traveling wave speed as T α =167.3×10 6 m / s, and the fault distance is calculated using formula (1), the result is:

[0161]

[0162] The calculated result differs by 170m from the actual fault point of 3000m, that is, the absolute error is 170m.

[0163] 5.1.2 The fault occurs in the branch with the distance measuring device

[0164] Assume that the fault occurs at a distance of 200m from point E and use the fault distance measuring device at point E to measure the distance.

[0165] like Fig.15 As shown in Figure 1, the α-mode fault traveling wave received at point E. Fig.16 As shown, the wavelet transform d1 waveform received at point E. The arrival time T of the traveling wave head of the α-mode fault is α =0.020002s.

[0166] like Fig.17 As shown in Figure 1, the 0-mode fault traveling wave received at point E. Fig.18 As shown, the wavelet transform d1 waveform received at point E. The arrival time of the first wave head of the 0-mode fault traveling wave is T0 = 0.020004s.

[0167] Select the 0-mode traveling wave velocity v0 = 89.07 × 10 6 m / s. According to formula (4) in 4.2.2, the fault distance can be calculated as follows:

[0168]

[0169] The absolute error is 181m.

[0170] 5.1.3 The fault occurs in the branch without distance measuring device

[0171] Assume that a single-phase grounding fault of phase B occurs 300m away from point D, and the fault distance measuring device at point A is used for distance measurement.

[0172] like Fig.19 As shown in Figure 1, the α-mode fault traveling wave received at point A. Fig. 20 As shown, the wavelet transform d1 waveform received at point A. The arrival time T of the traveling wave head of the α-mode fault is α =0.020033s.

[0173] like Fig.21 As shown in Figure 1, the 0-mode fault traveling wave received at point A. Fig. 22 As shown in Figure 1, the wavelet transform d1 waveform received at point A. The arrival time of the first wave head of the 0-mode fault traveling wave is T0 = 0.020060s.

[0174] According to formula (6), the fault distance is calculated as:

[0175]

[0176] The distance from the actual fault point is 157m.

[0177] like Fig.23 As shown, the fault distance measuring device at point E is used to measure the distance and the α-mode fault traveling wave is received.

[0178] like Fig.24 As shown, the fault distance measuring device at point E is used to measure the distance, and the received wavelet transform d1 waveform is obtained.

[0179] The arrival time T of the first wave head of the traveling wave for locating α-mode fault α =0.020021s.

[0180] like Fig.25 As shown in Figure 1, the 0-mode fault traveling wave received at point E. Fig.26 As shown, the wavelet transform d1 waveform received at point E. The arrival time of the first wave head of the 0-mode fault traveling wave is T0 = 0.02038s.

[0181] According to formula (7), the fault distance is calculated as:

[0182]

[0183] The actual fault distance is 62m different, and the average of L3 and L4 is taken as the final calculation result, that is, The absolute error is 109.5m, and the ranging result error meets the requirements.

[0184] 5.1.4 Fault at the end of the line

[0185] Assume that a single-phase grounding fault of phase A occurs 1 km away from point B, and the distance is measured using the fault distance measuring devices at points I and B.

[0186] like Fig. 27 As shown in Figure 1, the α-mode fault traveling wave received at point I. Fig.28 As shown, the wavelet transform d1 waveform is received at point I. The time when the head of the traveling wave of the α-mode fault reaches point I is T I =0.020013s.

[0187] like Fig.29 As shown in the figure, the α-mode fault traveling wave received at point B is as follows: Fig.30 As shown, the wavelet transform d1 waveform received at point B. The time when the head of the traveling wave of the α-mode fault reaches point B is T B =0.020007s.

[0188] According to formula (9), the distance can be calculated as follows:

[0189]

[0190] The calculated result differs from the actual fault point at 1000m by 2m, that is, the absolute error is 2m. The above four fault simulations are continued by selecting different fault points, and the results are summarized in Table 1.

[0191] Table 1: Single-phase fault simulation distance calculation results

[0192]

[0193] In Table 1, the fault distance is the distance from the ranging reference point.

[0194] From the statistical data in Table 1, it can be seen that the absolute error of ranging is the largest when the fault occurs at a branch without a ranging device, with a maximum error of 198m. This is because the zero-mode wave velocity is not stable relative to the line-mode wave velocity and decays quickly, and there is an error between the calculation process and the actual situation. At the same time, when the traveling wave transmission process passes through the branch point, the refraction and reflection generated will also affect the traveling wave transmission process.

[0195] 5.2 Phase-to-phase fault simulation analysis

[0196] In 5.1, the simulation of single-phase high-resistance grounding fault was completed for four fault locations, and the fault distance and ranging error were calculated. This section will focus on the simulation of other types of faults. The simulation process is similar to that in Section 5.1, so it will not be repeated here. The simulation results are summarized and classified, and the results are shown in Table 2.

[0197] Table 2: Phase-to-phase fault simulation distance calculation results

[0198]

[0199] The following conclusions can be drawn from the simulation results in Table 2:

[0200] (1) Two-phase high-resistance grounding faults can be located, and the maximum absolute error of the positioning result is 114m. It is impossible to accurately locate two-phase short-circuit faults, three-phase high-resistance grounding faults, and phase short-circuit faults. Only the main transmission line fault can be located. Faults occurring in branch lines can only be located at the branch point.

[0201] (2) When a two-phase short-circuit fault occurs in a branch of a transmission line, it is impossible to locate the fault. This is because no zero-mode voltage traveling wave is generated during a phase-to-phase short-circuit fault, and it is therefore impossible to identify the zero-mode waveform head.

[0202] (3) When a three-phase fault occurs, the vector sum of the zero-mode components of the three phases is zero, which is shown in the simulation results as zero-mode voltage traveling wave amplitude. This makes it impossible to identify the zero-mode waveform head and locate the fault point in the branch. Just like a two-phase short-circuit fault, in actual fault location, only the branch point can be detected.

[0203] After this application was run confidentially for a period of time, the on-site technicians reported that the benefits were:

[0204] 1. A universal ranging method is proposed for complex distribution network topology, which can locate faults for different types of power supply networks.

[0205] 2. The number of traveling wave extraction devices is reduced by nearly half, greatly reducing the cost required for fault location.

[0206] At present, the technical solution of the present invention has been put into pilot production, that is, a small-scale test of the product before large-scale mass production; after the pilot production was completed, a user usage survey was carried out in a small range, and the survey results showed that user satisfaction was high; now preparations have begun for the formal production of the product for industrialization (including intellectual property risk warning survey).

Claims

1. A multi-branch distribution network fault distance measuring device based on traveling waves, wherein the distribution network is a trunk line with branch lines, and the connection between the branch line and the trunk line is a branch connection point, characterized in that: It includes a fault voltage traveling wave extraction device and a controller, wherein the fault voltage traveling wave extraction device is arranged at the end point of the trunk line, and the fault voltage traveling wave extraction device is arranged at the interval branch connection point, and the controller is respectively connected to and communicates with each fault voltage traveling wave extraction device; It also includes a distance measurement module, the controller is a single chip microcomputer or a computer, and the distance measurement module is a program module, which is used for the fault voltage traveling wave extraction device to obtain the arrival time of the fault voltage traveling wave arriving at the fault voltage traveling wave extraction device and send it to the controller, and the arrival time includes the zero mode time t0 and the α mode time t α , the controller obtains the arrival time, and based on the arrival time, it is known that the fault point is located on the branch line between two adjacent fault voltage traveling wave extraction devices based on the section positioning algorithm. The controller calculates the arrival time based on the zero mode time t0 and the α mode time t α The distance to the fault point is calculated by the time difference Δt; The fault voltage traveling wave extraction device comprises a first fault voltage traveling wave extraction device and a second fault voltage traveling wave extraction device, a branch connection point between a branch line and a trunk line is a second reference point on the trunk line, a first fault voltage traveling wave extraction device is arranged on one side of the second reference point, and a second fault voltage traveling wave extraction device is arranged on the other side of the second reference point, the position of the first fault voltage traveling wave extraction device on the trunk line is a first reference point, and the position of the second fault voltage traveling wave extraction device on the trunk line is a third reference point, the first reference point is an end point or a branch connection point of the trunk line, the third reference point is an end point or a branch connection point of the trunk line, and the line on the trunk line between the first reference point and the third reference point is the main line; The distance measurement module is also used for the controller to calculate the distance to the fault point according to equation (3) and equation (10). Δt=t0-t α (3) In formula (3), the zero mode time t0 is the time when the zero mode reaches the traveling wave extraction device, unit is s; the α mode time t α is the time when the α mode reaches the traveling wave extraction device, in s; Δt is the time t after the zero mode time t0 and the α mode time t α The time difference, unit is s; In formula (10), i is the reference point number, the value of i is 1 or 3, and the i-th reference point is the first reference point or the third reference point; L i is the distance from the fault point to the second reference point calculated with the i-th reference point as the distance measurement center, in meters; v0 is the zero modulus wave velocity, in meters per second; v α is the α-mode wave velocity, in m / s; Δt is the time from the zero-mode moment t0 to the α-mode moment t α The time difference to reach the i-th reference point, in seconds; l i It is the physical length of the trunk line between the ith reference point and the second reference point, in meters.

2. A multi-branch power distribution network fault location device based on traveling waves according to claim 1, characterized in that: The distance measuring module is also used for the controller to calculate the distance of the fault point according to the arrival time obtained by the fault voltage traveling wave extraction device closest to the fault point.

3. The multi-branch power distribution network fault location device based on traveling waves according to claim 1, characterized in that: The distance measurement module is also used for the controller to obtain the distance from the fault point with the first reference point as the distance measurement center to the second reference point as the first fault distance, obtain the distance from the fault point with the third reference point as the distance measurement center to the second reference point as the second fault distance, and obtain the average value of the first fault distance and the second fault distance as the fault point distance, that is, sum the first fault distance and the second fault distance and divide it by 2.

4. A multi-branch distribution network fault location method based on traveling waves, characterized in that: The multi-branch distribution network fault distance measuring device based on traveling waves according to claim 1 comprises a distance measuring step, wherein a fault voltage traveling wave extraction device obtains the arrival time of the fault voltage traveling wave arriving at the fault voltage traveling wave extraction device, and the arrival time comprises a zero mode time t0 and an α mode time t α According to the arrival time, based on the section location algorithm, it is known that the fault point is located on the branch line between two adjacent fault voltage traveling wave extraction devices. According to the zero mode time t0 and the α mode time t α The distance to the fault point is calculated by the time difference Δt.

5. A multi-branch distribution network fault location method based on traveling waves according to claim 4, characterized in that: In the distance measurement step, the fault point distance is calculated according to equations (3) and (10), or the fault point distance is calculated according to the arrival time obtained by the fault voltage traveling wave extraction device closest to the fault point, or the average value of the first fault distance and the second fault distance is obtained as the fault point distance.

6. A multi-branch distribution network fault location device based on traveling waves, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the multi-branch power distribution network fault location method based on traveling waves described in claim 4 or 5 is implemented.

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