Distributed traveling wave distance measurement stationing method and system for multi-branch hybrid line

Abstract

The invention discloses a distributed traveling wave distance measurement stationing method and system for a multi-branch hybrid line, and belongs to the technical field of electrical engineering measurement. The method comprises the following steps: acquiring a traveling wave distance measuring device at the tail end of a multi-branch hybrid line; the method comprises the following steps: solving an attenuation coefficient of a cross node through which a traveling wave distance measurement device transmitted from a fault line to the tail end of the line passes, constructing an attenuation coefficient matrix, solving a full overhead line fault traveling wave amplitude transmission attenuation matrix, setting the attenuation matrix as an actual amplitude, judging whether the line is measurable or not, and judging whether double-end distance measurement of an unmeasurable line fails or not according to double-end distance measurement; and taking an intersection of the propagation ranges of all the unmeasurable lines, setting nodes in an intersection line as optimal additional distance measurement device points, and if no intersection exists, taking a node additional distance measurement device point in the propagation ranges of all the unmeasurable lines and then taking a union set, thereby realizing distributed traveling wave distance measurement distribution of the multi-branch mixed line. According to the method, an economical point distribution strategy is met, and the reliability of fault distance measurement is enhanced.

Description

Technical Field

[0001] The present invention belongs to the field of electrical engineering measurement technology, and more specifically, relates to a distributed traveling wave ranging point arrangement method and system for multi-branch hybrid lines. Background Art

[0002] The mainstream method of distribution network traveling wave ranging, the two-terminal method, relies on the initial traveling wave signals on both sides and does not consider the problem of traveling wave signal attenuation, resulting in insufficient structural adaptability to complex power grids. In multi-T-type lines and cable-overhead line hybrid lines, the traveling wave propagation path is complex. The traditional two-terminal method may not be able to accurately distinguish the fault branch and needs to rely on data from more monitoring points.

[0003] The existing technology converts the optimization configuration problem into a mathematical programming problem, but ignores the existence of a certain range of ranging blind spots when the device fails; the existing technology proposes a distribution network fault location method based on the distance matrix and branch coefficient, which is based on the two-terminal method and optimizes the configuration of the traveling wave acquisition device by extracting the zero and line mode components of the fault traveling wave. However, the zero mode component attenuates rapidly in the line and the line zero mode component attenuates greatly at the branch point and the cable connection point, making the positioning reliability uncertain; the existing technology uses a new hybrid optical fiber sensor to obtain broadband transient traveling waves and adopts interval positioning and the two-terminal method for traveling wave ranging, but its long-distance propagation characteristics and stability have not been effectively verified; the existing technology considers that the distribution network contains complex multiple branches, resulting in excessive signal attenuation, which affects ranging, and chooses to add a ranging device at each branch point. It does not consider the impact of attenuation caused by the line mixing point, and this method will cause redundancy in the ranging range and increase economic costs.

[0004] Traveling wave monitoring devices trigger recording when the amplitude of the arriving traveling wave's head reaches its trigger threshold. However, for 35kV and 10kV distribution networks, the presence of a large number of branch lines and cable-overhead line hybrid connections leads to significant attenuation of not only the zero-mode component of the overhead line and the ground-mode component of the cable, but also the significant attenuation of the line-mode and coaxial-mode components of the overhead line. When the initial traveling wave of a fault reaches the traveling wave monitoring device, it is attenuated to a certain degree, making it unable to effectively detect the wave head, resulting in ranging failure or excessive error.

[0005] Generally speaking, current deployment methods fail to account for the attenuation of traveling waves caused by branch lines and mixed cable-overhead line connections, which can make traveling wave monitoring devices undetectable. Traveling wave monitoring equipment uses the amplitude of the arriving traveling wave's head as the trigger for fault recording. The numerous overhead line-cable connection points and T-junctions in distribution networks are the primary factors contributing to the attenuation of fault-related traveling wave amplitudes. When traveling waves are significantly attenuated during propagation due to these influences, traveling wave monitoring equipment may be unable to detect the initial traveling wave head, resulting in significant errors in ranging recognition.

[0006] The existing technology relies on manual intervention, has complex calculations, and relies on the injected traveling wave amplitude to obtain the attenuation coefficient, which has a high possibility of misjudgment. The existing technology does not take into account the attenuation of the fault traveling wave at the overhead line-cable connection point, resulting in the monitoring device being unable to effectively detect the wave head, causing ranging failure or excessive error. Summary of the Invention

[0007] To address the shortcomings of the existing technology, the present invention provides a method for solving the problem of undetectable traveling wave devices in existing 35kV and 10kV distribution network distributed traveling wave ranging point placement methods, which are affected by branch points and overhead-cable hybrid connection points. This method fully considers the impact of branch lines, overhead-cable hybrid connection points, and line parameters on the amplitude attenuation of fault traveling wave transmission. It uses the voltage traveling wave line modulus attenuation as the basis for traveling wave monitoring point placement, and by constructing a quantized attenuation matrix, implements a placement solution based on the principle of two-terminal traveling wave ranging.

[0008] The present invention adopts the following technical solutions.

[0009] A first aspect of the present invention provides a method for distributing traveling wave ranging points for a multi-branch hybrid line, comprising:

[0010] Acquire a set of traveling wave ranging devices at the end of a multi-branch hybrid line;

[0011] Determine the attenuation coefficient of the cross-nodes that the traveling wave ranging device passes through when transmitting from the fault line to the end of the line. The cross-nodes include the overhead line-cable hybrid point and the T-branch point.

[0012] An attenuation coefficient matrix is ​​constructed based on the attenuation coefficient of the cross node that the fault line transmits to the traveling wave ranging device at the end of the line. The initial fault traveling wave matrix of the fault line is multiplied by the attenuation coefficient matrix to obtain the full overhead line fault traveling wave amplitude transmission attenuation matrix.

[0013] The full overhead line fault traveling wave amplitude transmission attenuation matrix is ​​set to the actual amplitude to determine whether the traveling wave ranging device at the end of the line has failed. Based on the two-terminal ranging method and the traveling wave ranging device at the end of the failed line, it is determined whether each line is measurable, and the set of non-failed cross nodes in the unmeasurable line is obtained.

[0014] Take the intersection of the non-failed cross nodes in the set of non-failed cross nodes in all unmeasurable lines, set any non-failed cross node in the intersection as the best point for adding a ranging device and add a traveling wave ranging device. If there is no intersection, randomly select one node in the set of non-failed cross nodes under all unmeasurable lines to add a traveling wave ranging device and then take the union of all nodes to realize the distributed traveling wave ranging point layout of multi-branch hybrid lines.

[0015] Preferably, the set of traveling wave ranging devices for obtaining the line end of the multi-branch hybrid line specifically includes:

[0016] Determine whether all multi-branch hybrid lines meet the ranging accuracy requirements of overhead lines and cables. If a multi-branch hybrid line meets the ranging accuracy requirements of overhead lines and cables, no traveling wave ranging device is set at the end of the current line. If a multi-branch hybrid line does not meet the ranging accuracy requirements of overhead lines and cables, a traveling wave ranging device is set at the end of the current line. Finally, the set of traveling wave ranging devices at the end of the multi-branch hybrid line is obtained.

[0017] Preferably, the step of determining the attenuation coefficient of the cross-nodes through which the traveling wave ranging device transmits the fault line to the end of the line specifically includes:

[0018] When the fault traveling wave passes through the overhead line-cable connection point, the overhead line mode and the cable coaxial mode are monitored. The mixed point is connected in the phase domain according to the traveling wave refraction and reflection law. The fault traveling wave transmission refraction value at the overhead line-cable mixed point is obtained by combining the phase mode transformation matrix and the wave impedance parameters.

[0019] Calculate the refraction value of the fault traveling wave at the T branch point;

[0020] The fault traveling wave transmission refraction values ​​at all overhead line-cable hybrid points and T-branch points are set as the attenuation coefficients of the cross nodes that the fault line passes through when transmitting to the traveling wave ranging device at the end of the line.

[0021] Preferably, when the fault traveling wave passes through the overhead line-cable connection point, the overhead line mode and the cable coaxial mode are used as monitoring objects, the mixed point is connected in the phase domain according to the traveling wave refraction and reflection law, and the fault traveling wave transmission refraction value at the overhead line-cable mixed point is obtained in conjunction with the phase mode transformation matrix and the wave impedance parameter, specifically including:

[0022] When a single-phase ground fault occurs on an overhead line, the equations for the overhead line phase voltage and cable phase voltage, as well as the equations for the overhead line phase current and cable phase current at the first overhead line-cable hybrid point are constructed based on the voltage wave refraction and reflection law at the overhead line-cable connection point.

[0023] The overhead line phase domain voltage and the overhead line phase domain current are converted into the overhead line mode domain voltage and the overhead line mode domain current by using the Karen Bell phase mode transformation matrix;

[0024] The three-phase single-core cable uses the cable Karen Bell phase mode transformation matrix to convert the cable phase domain voltage and cable phase domain current into the cable mode domain voltage and cable mode domain current;

[0025] The overhead line mode wave impedance is solved based on the overhead line mode voltage and the overhead line mode current. The cable coaxial mode wave impedance is solved based on the cable mode voltage and the cable mode current. Combined with the fault boundary conditions of the first overhead line-cable hybrid point, and ignoring the propagation of the fault traveling wave in the non-fault phase, the refraction value of the fault traveling wave at the first cable-overhead line connection point is solved.

[0026] The fault boundary conditions of the first overhead line-cable hybrid point include that the incident traveling wave of the B-phase current is equal to 0 and the incident traveling wave of the C-phase current is equal to 0.

[0027] Preferably, if the fault traveling wave continues to pass through the overhead line-cable connection point, solving the fault traveling wave transmission refraction value at the second overhead line-cable hybrid point specifically includes:

[0028] If the traveling wave of the A-phase coaxial fault in the cable continues to pass through the overhead line-cable connection point, it will be refracted at the cable-overhead line connection point and transmitted to the overhead line. The equations for the overhead line phase voltage and cable phase voltage, as well as the equations for the overhead line phase current and cable phase current at the second overhead line-cable hybrid point are constructed.

[0029] Based on the equations for the overhead line phase voltage and cable phase voltage at the second overhead line-cable hybrid point, as well as the equations for the overhead line phase current and cable phase current, phase mode transformation of the overhead line and cable is performed to solve the overhead line line mode wave impedance and the cable coaxial mode wave impedance.

[0030] According to the overhead line mode wave impedance and the cable coaxial mode wave impedance, combined with the fault boundary conditions of the second overhead line-cable hybrid point, the refraction value of the fault traveling wave at the second cable-overhead line connection point is solved.

[0031] Among them, the fault boundary conditions of the second overhead line-cable hybrid point include that the incident voltage of the cable core phase B is equal to the incident voltage of the cable core phase C and is equal to 0, and the incident current of the cable core phase A is opposite in direction to the incident current of the cable sheath phase A.

[0032] Preferably, if the fault traveling wave continues to pass through the overhead line-cable connection point, solving the fault traveling wave transmission refraction value at the third overhead line-cable hybrid point specifically includes:

[0033] If the fault traveling wave continues to pass through the overhead line-cable connection point, the equations for the overhead line phase-domain voltage and cable phase-domain voltage, as well as the equations for the overhead line phase-domain current and cable phase-domain current at the first overhead line-cable hybrid point are constructed to determine the equations for the overhead line phase-domain voltage and cable phase-domain voltage, as well as the equations for the overhead line phase-domain current and cable phase-domain current at the third overhead line-cable hybrid point.

[0034] Based on the equations for the overhead line phase voltage and cable phase voltage at the third overhead line-cable hybrid point, as well as the equations for the overhead line phase current and cable phase current, phase mode transformation of the overhead line and cable is performed to solve the overhead line line mode wave impedance and the cable coaxial mode wave impedance.

[0035] According to the overhead line mode wave impedance and the cable coaxial mode wave impedance, and combined with the fault boundary conditions of the third overhead line-cable hybrid point, the refraction value of the fault traveling wave at the third cable-overhead line connection point is solved.

[0036] Among them, the fault boundary condition of the third overhead line-cable hybrid point includes that the incident voltage of the overhead line phase B is equal to the incident voltage of the overhead line phase C and is equal to 0.

[0037] Preferably, the constructing of the attenuation coefficient matrix specifically includes:

[0038] The fault line e i The traveling wave ranging device transmitted to the end of the line passes through the cross node T i Multiplication of attenuation coefficients

[0039] With e as the base, the line parameter frequency attenuation coefficient α line And the shortest path distance from the fault point to each terminal device The multiplication result is an exponential, which gives us the exponential decay law.

[0040] Multiply the result and exponential decay law Multiply them together to get the fault line e i Transmit to Mth j The attenuation coefficient matrix at the node of the traveling wave ranging device at the end of the line

[0041] Preferably, the method of setting the full overhead line fault traveling wave amplitude transmission attenuation matrix to the actual amplitude, solving whether the traveling wave ranging device at the end of the line has failed, and judging whether each line is measurable based on the two-terminal ranging method and the traveling wave ranging device at the end of the failed line, and obtaining the set of non-failed cross nodes in the unmeasurable line specifically includes:

[0042] The actual amplitude of the existing terminal device at the time of each line fault is obtained based on the full overhead line fault traveling wave amplitude transmission attenuation matrix. Combined with the device detection threshold, the failure coefficient of the traveling wave ranging device at the end of the line is used to determine whether the traveling wave ranging device at the end of the line has failed, and the set of line failure devices is obtained.

[0043] Compare the set of line failure devices with the set of devices at both ends of the corresponding line. If a line failure device coincides with the device at either end of its corresponding line, it is determined that the dual-end ranging of the line has failed and the line is determined to be unmeasurable.

[0044] When a line failure device fails at a certain node, the node is determined to be a failed node, and a set of non-failed cross nodes in the untestable line is obtained.

[0045] Preferably, the non-failure coefficient of the traveling wave ranging device at the end of the line specifically includes:

[0046] Take 1 and the actual amplitude divided by the minimum value of the device detection threshold of the set multiple, and round it up to get the non-failure coefficient of the traveling wave ranging device at the end of the line. When the non-failure coefficient of the traveling wave ranging device at the end of the line is 1, it is set to be measurable, and when it is 0, it is set to be unmeasurable.

[0047] The second aspect of the present invention provides a distributed traveling wave ranging point placement system for a multi-branch hybrid line, which runs the distributed traveling wave ranging point placement method for a multi-branch hybrid line described in the first aspect of the present invention, specifically comprising:

[0048] A traveling wave ranging device setting module at the end of a line is used to obtain a set of traveling wave ranging devices at the end of a multi-branch hybrid line;

[0049] An attenuation coefficient solving module is used to solve the attenuation coefficient of the cross node through which the fault line transmits the traveling wave ranging device to the end of the line. The cross node includes the overhead line-cable hybrid point and the T-branch point;

[0050] The attenuation matrix solving module is used to construct an attenuation coefficient matrix based on the attenuation coefficient of the cross node through which the traveling wave ranging device at the end of the line is transmitted from the fault line. The initial fault traveling wave matrix of the fault line is multiplied by the attenuation coefficient matrix to obtain the full overhead line fault traveling wave amplitude transmission attenuation matrix;

[0051] A traveling wave ranging device acquisition module is added to set the full overhead line fault traveling wave amplitude transmission attenuation matrix to the actual amplitude, determine whether the traveling wave ranging device at the end of the line has failed, and determine whether each line is measurable based on the two-terminal ranging method and the traveling wave ranging device at the end of the failed line, and obtain the set of non-failed cross nodes in the unmeasurable line;

[0052] The point distribution module is used to take the intersection of the non-failed cross nodes in the set of non-failed cross nodes in all unmeasurable lines, set any non-failed cross node in the intersection as the best point for adding a ranging device and add a traveling wave ranging device. If there is no intersection, any one node in the set of non-failed cross nodes under all unmeasurable lines is randomly selected to add a traveling wave ranging device and then the union of all nodes is taken to realize distributed traveling wave ranging point distribution of multi-branch hybrid lines.

[0053] Compared with the prior art, the beneficial effects of the present invention include at least:

[0054] (1) The present invention does not rely on the amplitude of the injected traveling wave to obtain the attenuation coefficient. Instead, the branch point attenuation coefficient can be obtained only by relying on line parameters (such as, but not limited to, the three-phase voltage and current of the overhead line and the three-phase voltage and current of the cable). By using known line parameters to obtain the node attenuation coefficient, the electromagnetic interference problem caused by the traditional injection of the traveling wave amplitude can be avoided.

[0055] (2) The present invention fully considers the attenuation of traveling wave transmission caused by T-nodes and cable-overhead hybrid connection points, and arranges the device points based on this consideration, thereby avoiding the problem in existing layout methods that the ranging device cannot start recording due to the significant attenuation of the fault traveling wave in the distribution network, thereby avoiding ranging failures and eliminating ranging blind spots. Ultimately, the reliability of fault ranging can be greatly enhanced on the basis of meeting the economical layout strategy.

[0056] (3) By monitoring the overhead line mode component and the cable coaxial mode component for distance measurement, the double-ended traveling wave distance measurement of the fault point in the cable and overhead line can be realized.

[0057] (4) Distance measurement is performed by monitoring the overhead line mode component and the cable coaxial mode component, which not only ensures the amplitude of the traveling wave transmission to ensure the detection sensitivity of the traveling wave head, but also can be applied to ground fault and short circuit fault ranging applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 is a schematic diagram of a deployment planning flow chart provided according to an embodiment of the present invention;

[0059] Figure 2 is a schematic diagram of a mixed scenario of air lines and cables in a multi-branch rack according to an embodiment of the present invention;

[0060] Figure 3 This is a schematic diagram of a 10kV distribution network model provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0061] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0062] like Figure 1 and Figure 2 As shown, embodiment 1 of the present invention provides a distributed traveling wave ranging point arrangement method for a multi-branch hybrid line, comprising the following steps:

[0063] Step 1: Acquire a set of traveling wave ranging devices at the end of a multi-branch hybrid line.

[0064] In a preferred but non-limiting embodiment of the present invention, step 1 comprises:

[0065] Determine whether all multi-branch hybrid lines meet the ranging accuracy requirements of overhead lines and cables. If a multi-branch hybrid line meets the ranging accuracy requirements of overhead lines and cables in formula (1), the current line is only inspected manually, and there is no need to set up a traveling wave ranging device at the end of the line to meet the economic requirements. It should be noted that there is no situation where all multi-branch hybrid lines do not need to set up a traveling wave ranging device at the end of the line. Most multi-branch hybrid lines do not meet the ranging accuracy requirements. If a multi-branch hybrid line does not meet the ranging accuracy requirements of overhead lines and cables, a traveling wave ranging device is set at the end of the current line to obtain the set of traveling wave ranging devices at the end of the multi-branch hybrid line.

[0066] Further preferably, the distance measurement accuracy requirement of the overhead lines and cables is expressed by the following formula:

[0067] L≤aL ε (1)

[0068] Where,

[0069] L is the actual length of the overhead line or cable,

[0070] L ε For the distance measurement accuracy of overhead lines or cables,

[0071] a is the ranging accuracy coefficient, which can be flexibly set according to reliability requirements and the amount of manual inspection.

[0072] Step 2: Calculate the attenuation coefficient of the cross-nodes through which the fault line is transmitted to the traveling wave ranging device at the end of the line described in step 1. The cross-nodes include the overhead line-cable hybrid point and the T-branch point.

[0073] In a preferred but non-limiting embodiment of the present invention, step 2 comprises:

[0074] In step 2.1, when the fault traveling wave passes through the overhead line-cable connection point, the overhead line mode and the cable coaxial mode are monitored. The mixed point is connected in the phase domain according to the traveling wave refraction and reflection law. The fault traveling wave transmission refraction value at the overhead line-cable mixed point is obtained by combining the phase mode transformation matrix and the wave impedance parameters.

[0075] Further preferably, step 2.1 includes:

[0076] Step 2.1.1, calculate the fault traveling wave transmission refraction value at the first overhead line-cable hybrid point.

[0077] More preferably, step 2.1.1 comprises:

[0078] When a single-phase (phase A) ground fault occurs on the overhead line, the equations for the overhead line phase voltage and cable phase voltage, as well as the equations for the overhead line phase current and cable phase current at the first overhead line-cable hybrid point are constructed at the overhead line-cable connection point based on the voltage wave refraction and reflection law. These equations are expressed as follows:

[0079] U (ABC)q +U (ABC)r =U C(ABC)t (2)

[0080] I (ABC)q -I (ABC)r =I C(ABC)t

[0081] Where,

[0082] U (ABC)q is the incident traveling wave of the three-phase voltage in the phase domain of the overhead line,

[0083] U (ABC)r is the reflected traveling wave of the three-phase voltage in the overhead line,

[0084] U C(ABC)t is the refracted traveling wave of the three-phase core voltage in the cable,

[0085] I (ABC)q is the incident traveling wave of the three-phase current in the overhead line,

[0086] I (ABC)r is the reflected traveling wave of the three-phase current in the overhead line.

[0087] I C(ABC)t It is the traveling wave refracted by the current in the phase domain of the three-phase core of the cable.

[0088] The overhead line phase domain voltage and the overhead line phase domain current are converted into the overhead line mode domain voltage and the overhead line mode domain current through the Karen Bell phase mode transformation matrix. The overhead line Karen Bell phase mode transformation matrix is ​​expressed as the following formula:

[0089]

[0090] Where,

[0091] u α ,u β is the overhead line mode voltage, u0 is the overhead line zero mode voltage, corresponding to the overhead line mode domain voltage,

[0092] u A ,u B ,u C are the overhead line A, B, and C phase voltages, corresponding to the overhead line phase voltages,

[0093] i α ,i β is the overhead line mode current; i0 is the overhead line zero mode current, i α 、i β and i0 corresponds to the overhead line mode current,

[0094] i A ,i B ,i C They are the A, B, and C phase currents of the overhead line, corresponding to the phase domain currents of the overhead line.

[0095] Based on the high-frequency skin effect of the cable, the cable Karen Bell phase mode transformation matrix is ​​solved. The three-phase single-core cable uses the cable Karen Bell phase mode transformation matrix to convert the cable phase domain voltage and cable phase domain current into the cable mode domain voltage and cable mode domain current. The cable Karen Bell phase mode transformation matrix is ​​expressed as the following formula:

[0096]

[0097] Where,

[0098] u1 is the ground mode voltage of the cable sheath, u2 and u3 are the line mode voltages of the cable sheath, and u4, u5 and u6 are the coaxial mode voltages of the cable, corresponding to the cable domain voltage;

[0099] u CA 、u CB 、u CC are the phase voltages of cable core A, B, and C respectively, u SA 、u SB 、u SC are the phase voltages of the cable sheath A, B, and C, corresponding to the phase voltage of the cable;

[0100] i1 is the ground mode current of the cable sheath, i2 and i3 are the line mode currents of the cable sheath, and the voltages i4, i5, and i6 are the coaxial mode currents of the cable, corresponding to the cable domain current;

[0101] i CA 、i CB 、i CC are the phase currents of the cable core A, B, and C respectively, i SA 、i SB 、i SC They are the A, B, and C phase currents of the cable sheath, corresponding to the cable phase currents.

[0102] The overhead line mode voltage and the overhead line mode current are used to solve the overhead line mode wave impedance and the cable mode voltage and the cable mode current are used to solve the cable coaxial mode wave impedance. In combination with formula (2), the fault boundary condition i of the first overhead line-cable hybrid point is set. Bq =0,i Cq =0,i Bq represents the incident traveling wave of phase B current, i Cq represents the incident traveling wave of phase C current, u αq represents the incident traveling wave of the overhead line line mode voltage. The refracted traveling wave of the fault voltage traveling wave at the connection between the overhead line and the cable is obtained by solving the following formula:

[0103]

[0104] Where,

[0105] u αq is the incident traveling wave of the overhead line mode fault voltage;

[0106] u 4t ,u 5t They are the coaxial mode fault traveling waves refracted from the overhead line fault traveling waves to the cable phases A and B respectively;

[0107] Z4, Z α They are the coaxial mode wave impedance of the cable and the line mode wave impedance of the overhead line respectively.

[0108] At the cable connection point, the value of the fault traveling wave refraction from the fault phase into the non-fault phase is much smaller than that propagating between the fault phases, and Z α It is much larger than Z4, so the propagation of the fault traveling wave in the non-fault phase is approximately ignored in this process, which can be expressed as follows:

[0109]

[0110] Where,

[0111] u 4t,1 It indicates the refraction value of the cable coaxial mode of the fault traveling wave passing through the first cable-overhead line connection point.

[0112] In step 2.1.2, if the fault traveling wave continues to pass through the overhead line-cable connection point, calculate the fault traveling wave transmission refraction value at the second overhead line-cable hybrid point.

[0113] Further preferably, step 2.1.2 includes:

[0114] The fault traveling wave enters the three-phase cable and propagates. When the distribution network topology is complex, there are multiple hybrid connection points. That is, the fault traveling wave on the same axis of phase A in the cable will be refracted at the cable-overhead line connection point and transmitted to the overhead line. The phase domain voltage formula of the second overhead line-cable hybrid point is expressed as follows:

[0115] U C(ABC)q +U C(ABC)r =U (ABC)t (7)

[0116] I C(ABC)q -I C(ABC)r =I (ABC)t

[0117] Where,

[0118] U C(ABC)q Indicates the incident traveling wave of the phase domain voltage of the three-phase core of the cable,

[0119] U C(ABC)r Indicates the reflected traveling wave of the phase domain voltage of the three-phase core of the cable.

[0120] U (ABC)t It represents the refracted traveling wave of the three-phase voltage in the phase domain of the overhead line.

[0121] I C(ABC)q Indicates the incident traveling wave of the current in the phase domain of the three-phase core of the cable,

[0122] I C(ABC)r Indicates the reflected traveling wave of the phase domain current of the three-phase core of the cable.

[0123] I (ABC)t It represents the refracted traveling wave of the three-phase current in the overhead line.

[0124] When the coaxial mode of the cable refracts the traveling wave u 4t,1 When it is transmitted to the overhead line through the second cable-overhead line connection point, it becomes the incident wave u 4q,1 Based on the obtained equations for the second overhead line phase voltage and cable phase voltage, as well as the equations for the overhead line phase current and cable phase current, combined with the phase model transformation of the overhead line and cable, and the fault boundary condition U at the second overhead line-cable hybrid point, CBq =U CCq =0,i CAq =-i sAq,U CBq Indicates the incident voltage of phase B of the cable core, U CCq Indicates the incident voltage of phase C of the cable core, i CAq Indicates the incident current of phase B of the cable core, i SAq represents the incident current of phase A of the cable sheath. The refraction value of the fault traveling wave at the second cable-overhead line connection point is obtained by solving the following formula:

[0125]

[0126] Where,

[0127] u αt,2 It represents the refraction value of the fault traveling wave through the overhead line mode voltage at the second cable-overhead line connection point.

[0128] Z0 represents the overhead line zero-mode wave impedance,

[0129] u 4q Indicates the traveling wave of the same axial mode fault in cable A.

[0130] In step 2.1.3, if the fault traveling wave continues to pass through the overhead line-cable connection point, calculate the fault traveling wave transmission refraction value at the third overhead line-cable hybrid point.

[0131] Further preferably, step 2.1.3 includes:

[0132] When the overhead line mode refracts the traveling wave u at,2 When it is transmitted to the cable through the third cable-overhead line connection point, it becomes the incident wave u aq,2 If the fault traveling wave continues to pass through the overhead line-cable connection point, the connection relationship of the mixed point is as shown in formula (2). According to the phase transformation of the overhead line and cable and the fault boundary condition U of the third overhead line-cable mixed point, Bq =U Cq =0, U Bq Indicates the incident voltage on phase B of the overhead line, U Cq represents the incident voltage on phase C of the overhead line. The refraction value of the fault voltage traveling wave at the connection between the overhead line and the cable is obtained by the following formula:

[0133]

[0134] Where u 4t,3 It indicates the refraction value of the fault traveling wave through the cable coaxial mode at the third cable-overhead line connection point.

[0135] If there are still overhead line-cable connection points, the fault traveling wave propagation process is calculated cyclically according to the above process. For example, but not limited to, the fourth overhead line-cable connection point is calculated according to the first overhead line-cable connection point, the fifth overhead line-cable connection point is calculated according to the fault traveling wave transmission refraction value at the second overhead line-cable mixed point, and the sixth overhead line-cable connection point is calculated according to the fault traveling wave transmission refraction value at the third overhead line-cable mixed point.

[0136] Step 2.2, calculate the refraction value of the fault traveling wave transmission at the T branch point.

[0137] In a preferred but non-limiting embodiment of the present invention, step 2.2 comprises:

[0138] If the line through which the fault traveling wave passes is a T-connected line, and the line type and parameters are the same, the refraction value of the fault traveling wave transmission through the T branch point is attenuated to 2 / 3 times the initial fault traveling wave matrix. When the length of the branch line is very short (overhead line less than 150m, cable less than 75m), the fault traveling wave after the T connection is reflected by the transformer at the end of the branch line and refracted at the branch point. At this time, the refraction value of the fault traveling wave transmission at the T branch point is equal to 1.

[0139] In order for the distance measuring device to normally monitor the fault traveling wave, the amplitude of the initial traveling wave arriving at the monitoring point is set to be no less than 15% of the device detection threshold.

[0140] In step 2.3, the fault traveling wave transmission refraction values ​​at all overhead line-cable hybrid points and T-branch points are set as the attenuation coefficients of the cross nodes through which the fault line transmits to the traveling wave ranging device at the end of the line, and the cross nodes include the overhead line-cable hybrid points and T-branch points.

[0141] Step 3: Construct an attenuation coefficient matrix based on the attenuation coefficient of the cross node through which the fault line transmits the traveling wave ranging device at the end of the line in step 2. Take the fault line as the row and the traveling wave ranging device at the end of the line as the column. Multiply the initial fault traveling wave matrix of the fault line by the attenuation coefficient matrix to obtain the full overhead line fault traveling wave amplitude transmission attenuation matrix.

[0142] In a preferred but non-limiting embodiment of the present invention, step 3 comprises:

[0143] The topology of the distribution network consists of nodes and lines, where M j is the traveling wave ranging device node at the end of the line, T i is a cross node, including multiple branch nodes and cable connection points, E is a set of overhead lines, and each fault line e∈E represents the connection relationship between two nodes in the network. iEach row represents a fault on the corresponding line. When the fault angle and fault resistance change, the initial traveling wave of the fault has a large difference. The node M of the traveling wave ranging device at the end of the line j Establish the full overhead line fault traveling wave amplitude transmission attenuation matrix A for the column t , expressed as follows:

[0144]

[0145] Where,

[0146] A t is the transmission attenuation matrix of the traveling wave amplitude of the full overhead line fault, which is used to describe the amplitude of the fault traveling wave when it reaches the traveling wave ranging device at the end of the distribution network line when each line fails.

[0147] The fault line e i The initial traveling wave matrix of the fault,

[0148] The fault line e i Transmit to Mth j The attenuation coefficient matrix at the traveling wave ranging device node at the end of each line.

[0149] in, is the intersection node T i The attenuation coefficient of the traveling wave ranging device node M from the fault point to the end of the line j The product of the shortest path length and line parameter attenuation value is shown in formula (3):

[0150]

[0151] Where,

[0152] Indicates the fault line e i The traveling wave ranging device transmitted to the end of the line passes through the cross node T i The cumulative attenuation coefficient is

[0153] α line is the frequency-dependent attenuation coefficient of the line parameters,

[0154] It is the shortest path distance from the fault point to each terminal device.

[0155] Step 4: Set the full overhead line fault traveling wave amplitude transmission attenuation matrix obtained in step 3 to the actual amplitude, determine whether the traveling wave ranging device at the end of the line has failed, and determine whether each line is measurable based on the two-terminal ranging method and the traveling wave ranging device at the end of the failed line, and obtain the set of non-failed cross nodes in the unmeasurable line.

[0156] In a preferred but non-limiting embodiment of the present invention, step 4 comprises:

[0157] Step 4.1: Obtain the actual amplitude of the existing terminal device at the time of each line fault based on the full overhead line fault traveling wave amplitude transmission attenuation matrix. Combined with the device detection threshold, determine whether the traveling wave ranging device at the end of the line has failed based on the non-failure coefficient of the traveling wave ranging device at the end of the line, and obtain the line failure device set.

[0158] Further preferably, step 4.1 includes:

[0159] Taking a 10kV distribution network as an example, the device detection threshold is set according to the peak value of the single-phase voltage, i.e., 8.16kV. The fault resistance is calculated as 300Ω. The unfailed coefficient of the traveling wave ranging device at the end of the line is expressed as follows:

[0160]

[0161] Where,

[0162] INT[] is the rounding operation.

[0163] min() is the minimum value operation.

[0164] k is the actual amplitude,

[0165] X0 is the device detection threshold, and the present invention sets the device detection threshold multiple to 0.15 times.

[0166] m is the non-failure coefficient of the traveling wave ranging device at the end of the line. It is 1 when it is not failed and 0 when it is failed.

[0167] Step 4.2: Compare the set of line failure devices with the set of devices at both ends of the corresponding line. If a line failure device coincides with a device at either end of its corresponding line, it is determined that the dual-end ranging of the line has failed and the line is unmeasurable.

[0168] In step 4.3, the line failure device fails at a certain node, and the node is determined to be a failed node. Based on the non-failed cross nodes in the unmeasurable line, a ranging device is added to the non-failed cross nodes in the unmeasurable line transmission in step 4.2, and no ranging device is added to the failed cross nodes. This obtains the set of additional traveling wave ranging devices at the non-failed cross nodes in the unmeasurable line.

[0169] Step 5: Take the intersection of the non-failed cross nodes in the set of non-failed cross nodes in all unmeasurable lines, set any non-failed cross node in the intersection as the best point for adding a ranging device and add a traveling wave ranging device. If there is no intersection, take any one node in the set of non-failed cross nodes under all unmeasurable lines and add a traveling wave ranging device, and then take the union of all nodes to ensure that the entire line is measurable, to ensure the ranging reliability, and to realize the distributed traveling wave ranging point layout of multi-branch hybrid lines.

[0170] Embodiment 2 of the present invention provides a distributed traveling wave ranging point placement system for a multi-branch hybrid line, and executes the distributed traveling wave ranging point placement method for a multi-branch hybrid line described in embodiment 1, including:

[0171] A traveling wave ranging device setting module at the end of a line is used to obtain a set of traveling wave ranging devices at the end of a multi-branch hybrid line;

[0172] An attenuation coefficient solving module is used to solve the attenuation coefficient of the cross node through which the fault line transmits the traveling wave ranging device to the end of the line. The cross node includes the overhead line-cable hybrid point and the T-branch point;

[0173] The attenuation matrix solving module is used to construct an attenuation coefficient matrix based on the attenuation coefficient of the cross node through which the traveling wave ranging device at the end of the line is transmitted from the fault line. The initial fault traveling wave matrix of the fault line is multiplied by the attenuation coefficient matrix to obtain the full overhead line fault traveling wave amplitude transmission attenuation matrix;

[0174] A traveling wave ranging device acquisition module is added to set the full overhead line fault traveling wave amplitude transmission attenuation matrix to the actual amplitude, determine whether the traveling wave ranging device at the end of the line has failed, and determine whether each line is measurable based on the two-terminal ranging method and the traveling wave ranging device at the end of the failed line, and obtain the set of non-failed cross nodes in the unmeasurable line;

[0175] The point distribution module is used to take the intersection of the non-failed cross nodes in the set of non-failed cross nodes in all unmeasurable lines, set any non-failed cross node in the intersection as the best point for adding a ranging device and add a traveling wave ranging device. If there is no intersection, any one node in the set of non-failed cross nodes under all unmeasurable lines is randomly selected to add a traveling wave ranging device and then the union of all nodes is taken to realize distributed traveling wave ranging point distribution of multi-branch hybrid lines.

[0176] Example 3 of the present invention uses PSCAD / EMTDC transient simulation software to Figure 3The distribution network is being constructed. M1, M2, M3, M4, M5, and M6 are all end-of-line nodes, suitable for installing traveling wave ranging devices. M1 and M2 are the end-of-line nodes of the main trunk line. A single-phase ground fault is set on each line. The threshold is set based on a fault resistance of 300Ω and a fault phase angle of 90°. The threshold for triggering the device recording is set to 0.1076 kV, with an initial fault phase angle of 30°, an overhead line fault resistance of 300Ω, and a cable fault resistance of 5Ω. The deployment of traveling wave ranging devices at the end of the lines is planned according to the previous process.

[0177] 1) Simplify the distribution network, establish a topological structure diagram, number each node, and determine the edge sets.

[0178]

[0179] 2) Since the T1M3 line is 100m long, according to formula (1), no traveling wave ranging device is installed at M3, and traveling wave ranging devices are installed at M1, M2, M4, M5, and M6. When the fault is determined to be at the T1 branch point or within the T1M3 range, manual inspection is used to perform fault ranging.

[0180] 3) Establish the traveling wave attenuation matrix A of the fault line to be tested:

[0181]

[0182] The device failure set when judging each line fault is shown in Table 2:

[0183] Table 2 Detection status of distance measuring device when each line fails

[0184]

[0185] 4) Compare the failed device set for each line fault with the corresponding device set on one side. If there is any overlap, the faulty line is considered unmeasurable. Table 3 shows the device sets on the left and right sides of each faulty line. Comparing Tables 2 and 3, we find that the two-terminal ranging method fails when faults occur on lines T2T3 and T4T5. This demonstrates that unmeasurable lines exist in the original device configuration of this distribution network and requires additional measurement points.

[0186] Table 3 Distribution of double-end devices on each line

[0187] Fault line Left device Right device <![CDATA[T1M1]]> <![CDATA[{M1}]]> <![CDATA[{M2,M4,M5,M6}]]> <![CDATA[T1T2]]> <![CDATA[{M1}]]> <![CDATA[{M2,M4,M5,M6}]]> <![CDATA[T2T3]]> <![CDATA[{M1,M4}]]> <![CDATA[{M2,M5,M6}]]> <![CDATA[T2M4]]> <![CDATA[{M4}]]> <![CDATA[{M1,M2,M5,M6}]]> <![CDATA[T3T4]]> <![CDATA[{M1,M4}]]> <![CDATA[{M2,M5,M6}]]> <![CDATA[T4T5]]> <![CDATA[{M1,M4}]]> <![CDATA[{M2,M5,M6}]]> <![CDATA[T5T6]]> <![CDATA[{M5,M6}]]> <![CDATA[{M1,M2,M4}]]> <![CDATA[T5M2]]> <![CDATA[{M2}]]> <![CDATA[{M1,M4,M5,M6}]]> <![CDATA[T6M5]]> <![CDATA[{M5}]]> <![CDATA[{M1,M2,M4,M6}]]> <![CDATA[T6M6]]> <![CDATA[{M6}]]> <![CDATA[{M1,M2,M4,M5}]]>

[0188] 5) Based on the m=1 line in the traveling wave transmission path of the untestable line fault, its intersection node is used as the location for additional traveling wave ranging devices. Find the set of locations for additional traveling wave ranging devices at the failed end of each untestable line. The intersection of these sets is the final node to be added to reduce redundancy in the detection range. If these sets do not intersect, the union of these sets is used as the location for additional traveling wave ranging devices.

[0189] In this example, when the fault line is T2T3, its left side is measurable, and the fault traveling wave on the right side propagates to node T4. When the fault line is T4T5, its right side is measurable, and the fault traveling wave on the left side propagates to node T3. According to the planning rules deployed in this paper, the intersection of the two is taken, that is, adding a distance measuring device in the T3T4 line can ensure that the fault traveling wave amplitude of the entire line can be measured.

[0190] Compared with the prior art, the beneficial effects of the present invention include at least:

[0191] (1) The present invention does not rely on the amplitude of the injected traveling wave to obtain the attenuation coefficient. Instead, the branch point attenuation coefficient can be obtained only by relying on line parameters (such as, but not limited to, the three-phase voltage and current of the overhead line and the three-phase voltage and current of the cable). By using known line parameters to obtain the node attenuation coefficient, the electromagnetic interference problem caused by the traditional injection of the traveling wave amplitude can be avoided.

[0192] (2) The present invention fully considers the attenuation of traveling wave transmission caused by T-nodes and cable-overhead hybrid connection points, and arranges the device points based on this consideration, thereby avoiding the problem in existing layout methods that the ranging device cannot start recording due to the significant attenuation of the fault traveling wave in the distribution network, thereby avoiding ranging failures and eliminating ranging blind spots. Ultimately, the reliability of fault ranging can be greatly enhanced on the basis of meeting the economical layout strategy.

[0193] (3) By monitoring the overhead line mode component and the cable coaxial mode component for distance measurement, the double-ended traveling wave distance measurement of the fault point in the cable and overhead line can be realized.

[0194] (4) Distance measurement is performed by monitoring the overhead line mode component and the cable coaxial mode component, which not only ensures the amplitude of the traveling wave transmission to ensure the detection sensitivity of the traveling wave head, but also can be applied to ground fault and short circuit fault ranging applications.

[0195] 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 field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A distributed traveling wave ranging point arrangement method for multi-branch hybrid lines, characterized by: Acquire a set of traveling wave ranging devices at the end of a multi-branch hybrid line; Determine the attenuation coefficient of the cross-nodes that the traveling wave ranging device passes through when transmitting from the fault line to the end of the line. The cross-nodes include the overhead line-cable hybrid point and the T-branch point. Constructing an attenuation coefficient matrix based on the attenuation coefficient, multiplying the initial fault traveling wave matrix of the fault line by the attenuation coefficient matrix to obtain the full overhead line fault traveling wave amplitude transmission attenuation matrix; The full overhead line fault traveling wave amplitude transmission attenuation matrix is ​​set to the actual amplitude to determine whether the traveling wave ranging device at the end of the line has failed. Based on the two-terminal ranging method and the traveling wave ranging device at the end of the failed line, it is determined whether each line is measurable, and the set of non-failed cross nodes in the unmeasurable line is obtained. Take the intersection of the non-failed cross nodes in the set of non-failed cross nodes in all unmeasurable lines, set any non-failed cross node in the intersection as the best point for adding a ranging device and add a traveling wave ranging device. If there is no intersection, randomly select one node in the set of non-failed cross nodes under all unmeasurable lines to add a traveling wave ranging device and then take the union of all nodes to realize the distributed traveling wave ranging point layout of multi-branch hybrid lines.

2. The method for distributing traveling wave ranging points for a multi-branch hybrid line according to claim 1, characterized in that: The traveling wave ranging device set for obtaining the line end of the multi-branch hybrid line specifically includes: Determine whether all multi-branch hybrid lines meet the ranging accuracy requirements of overhead lines and cables. If a multi-branch hybrid line meets the ranging accuracy requirements of overhead lines and cables, no traveling wave ranging device is set at the end of the current line. If a multi-branch hybrid line does not meet the ranging accuracy requirements of overhead lines and cables, a traveling wave ranging device is set at the end of the current line to obtain the set of traveling wave ranging devices at the end of the multi-branch hybrid line.

3. The method for distributing traveling wave ranging points for a multi-branch hybrid line according to claim 1, characterized in that: The method of solving the attenuation coefficient of the cross node through which the traveling wave ranging device transmits the fault line to the end of the line specifically includes: When the fault traveling wave passes through the overhead line-cable connection point, the overhead line mode and the cable coaxial mode are monitored. The mixed point is connected in the phase domain according to the traveling wave refraction and reflection law. The fault traveling wave transmission refraction value at the overhead line-cable mixed point is obtained by combining the phase mode transformation matrix and the wave impedance parameters. Calculate the refraction value of the fault traveling wave at the T branch point; The fault traveling wave transmission refraction values ​​at all overhead line-cable hybrid points and T-branch points are set as the attenuation coefficients of the cross nodes that the fault line passes through when transmitting to the traveling wave ranging device at the end of the line.

4. The method for distributing traveling wave ranging points for a multi-branch hybrid line according to claim 3 is characterized in that: When the fault traveling wave passes through the overhead line-cable connection point, the overhead line mode and the cable coaxial mode are used as monitoring objects, the mixed point is connected in the phase domain according to the traveling wave refraction and reflection law, and the fault traveling wave transmission refraction value at the overhead line-cable mixed point is obtained in conjunction with the phase mode transformation matrix and the wave impedance parameters, specifically including: When a single-phase ground fault occurs on an overhead line, the equations for the overhead line phase voltage and cable phase voltage, as well as the equations for the overhead line phase current and cable phase current at the first overhead line-cable hybrid point are constructed based on the voltage wave refraction and reflection law at the overhead line-cable connection point. The overhead line phase domain voltage and the overhead line phase domain current are converted into the overhead line mode domain voltage and the overhead line mode domain current by using the Karen Bell phase mode transformation matrix; The three-phase single-core cable uses the cable Karen Bell phase mode transformation matrix to convert the cable phase domain voltage and cable phase domain current into the cable mode domain voltage and cable mode domain current; The overhead line mode wave impedance is solved based on the overhead line mode voltage and the overhead line mode current. The cable coaxial mode wave impedance is solved based on the cable mode voltage and the cable mode current. Combined with the fault boundary conditions of the first overhead line-cable hybrid point, and ignoring the propagation of the fault traveling wave in the non-fault phase, the refraction value of the fault traveling wave at the first cable-overhead line connection point is solved. The fault boundary conditions of the first overhead line-cable hybrid point include that the incident traveling wave of the B-phase current is equal to 0 and the incident traveling wave of the C-phase current is equal to 0.

5. The method for distributing traveling wave ranging points for a multi-branch hybrid line according to claim 4, characterized in that: If the fault traveling wave continues to pass through the overhead line-cable connection point, solving the fault traveling wave transmission refraction value at the second overhead line-cable hybrid point specifically includes: If the traveling wave of the A-phase coaxial fault in the cable continues to pass through the overhead line-cable connection point, it will be refracted at the cable-overhead line connection point and transmitted to the overhead line. The equations for the overhead line phase voltage and cable phase voltage, as well as the equations for the overhead line phase current and cable phase current at the second overhead line-cable hybrid point are constructed. Based on the equations for the overhead line phase voltage and cable phase voltage at the second overhead line-cable hybrid point, as well as the equations for the overhead line phase current and cable phase current, phase mode transformation of the overhead line and cable is performed to solve the overhead line line mode wave impedance and the cable coaxial mode wave impedance. According to the overhead line mode wave impedance and the cable coaxial mode wave impedance, combined with the fault boundary conditions of the second overhead line-cable hybrid point, the refraction value of the fault traveling wave at the second cable-overhead line connection point is solved. Among them, the fault boundary conditions of the second overhead line-cable hybrid point include that the incident voltage of the cable core phase B is equal to the incident voltage of the cable core phase C and is equal to 0, and the incident current of the cable core phase A is opposite in direction to the incident current of the cable sheath phase A.

6. The method for distributing traveling wave ranging points for a multi-branch hybrid line according to claim 5, characterized in that: If the fault traveling wave continues to pass through the overhead line-cable connection point, solving the fault traveling wave transmission refraction value at the third overhead line-cable hybrid point specifically includes: If the fault traveling wave continues to pass through the overhead line-cable connection point, the equations for the overhead line phase-domain voltage and cable phase-domain voltage, as well as the equations for the overhead line phase-domain current and cable phase-domain current at the first overhead line-cable hybrid point are constructed to determine the equations for the overhead line phase-domain voltage and cable phase-domain voltage, as well as the equations for the overhead line phase-domain current and cable phase-domain current at the third overhead line-cable hybrid point. Based on the equations for the overhead line phase voltage and cable phase voltage at the third overhead line-cable hybrid point, as well as the equations for the overhead line phase current and cable phase current, phase mode transformation of the overhead line and cable is performed to solve the overhead line line mode wave impedance and the cable coaxial mode wave impedance. According to the overhead line mode wave impedance and the cable coaxial mode wave impedance, and combined with the fault boundary conditions of the third overhead line-cable hybrid point, the refraction value of the fault traveling wave at the third cable-overhead line connection point is solved. Among them, the fault boundary condition of the third overhead line-cable hybrid point includes that the incident voltage of the overhead line phase B is equal to the incident voltage of the overhead line phase C and is equal to 0.

7. The method for distributing traveling wave ranging points for a multi-branch hybrid line according to claim 1, characterized in that: The constructing of the attenuation coefficient matrix specifically includes: The fault line e i The traveling wave ranging device transmitted to the end of the line passes through the cross node T i Multiplication of attenuation coefficients With e as the base, the line parameter frequency attenuation coefficient α line And the shortest path distance from the fault point to each terminal device The multiplication result is an exponential, which gives us the exponential decay law. Multiply the result and exponential decay law Multiply them together to get the fault line e i Transmit to Mth j The attenuation coefficient matrix at the node of the traveling wave ranging device at the end of the line 8. The method for distributing traveling wave ranging points for a multi-branch hybrid line according to claim 1, characterized in that: The full overhead line fault traveling wave amplitude transmission attenuation matrix is ​​set to the actual amplitude, and whether the traveling wave ranging device at the end of the line fails is solved. Based on the two-terminal ranging method and the traveling wave ranging device at the end of the failed line, whether each line is measurable is determined, and the set of non-failed cross nodes in the unmeasurable line is obtained. Specifically, it includes: The actual amplitude of the existing terminal device at the time of each line fault is obtained based on the full overhead line fault traveling wave amplitude transmission attenuation matrix. Combined with the device detection threshold, the failure coefficient of the traveling wave ranging device at the end of the line is used to determine whether the traveling wave ranging device at the end of the line has failed, and the set of line failure devices is obtained. Compare the set of line failure devices with the set of devices at both ends of the corresponding line. If a line failure device coincides with the device at either end of its corresponding line, it is determined that the dual-end ranging of the line has failed and the line is determined to be unmeasurable. When a line failure device fails at a certain node, the node is determined to be a failed node, and a set of non-failed cross nodes in the untestable line is obtained.

9. The method for distributing traveling wave ranging points for a multi-branch hybrid line according to claim 8, characterized in that: The non-failure coefficient of the traveling wave ranging device at the end of the line specifically includes: Take 1 and the actual amplitude divided by the minimum value of the device detection threshold of the set multiple, and round it up to get the non-failure coefficient of the traveling wave ranging device at the end of the line. When the non-failure coefficient of the traveling wave ranging device at the end of the line is 1, it is set to be measurable, and when it is 0, it is set to be unmeasurable.

10. A distributed traveling wave ranging point system for multi-branch hybrid lines, characterized by: A traveling wave ranging device setting module at the end of a line is used to obtain a set of traveling wave ranging devices at the end of a multi-branch hybrid line; An attenuation coefficient solving module is used to solve the attenuation coefficient of the cross node through which the fault line transmits the traveling wave ranging device to the end of the line. The cross node includes the overhead line-cable hybrid point and the T-branch point; The attenuation matrix solving module is used to construct an attenuation coefficient matrix based on the attenuation coefficient of the cross node through which the traveling wave ranging device at the end of the line is transmitted from the fault line. The initial fault traveling wave matrix of the fault line is multiplied by the attenuation coefficient matrix to obtain the full overhead line fault traveling wave amplitude transmission attenuation matrix; A traveling wave ranging device acquisition module is added to set the full overhead line fault traveling wave amplitude transmission attenuation matrix to the actual amplitude, determine whether the traveling wave ranging device at the end of the line has failed, and determine whether each line is measurable based on the two-terminal ranging method and the traveling wave ranging device at the end of the failed line, and obtain the set of non-failed cross nodes in the unmeasurable line; The point distribution module is used to take the intersection of the non-failed cross nodes in the set of non-failed cross nodes in all unmeasurable lines, set any non-failed cross node in the intersection as the best point for adding a ranging device and add a traveling wave ranging device. If there is no intersection, any one node in the set of non-failed cross nodes under all unmeasurable lines is randomly selected to add a traveling wave ranging device and then the union of all nodes is taken to realize distributed traveling wave ranging point distribution of multi-branch hybrid lines.

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