Power distribution network cable fault distance measurement method and system

Abstract

The invention discloses a power distribution network cable fault distance measurement method and system, and the method comprises the steps: collecting a fault component voltage at a protection installation part, and starting fault distance measurement when the fault component voltage is greater than a set threshold value; after fault distance measurement is started, a fault type is obtained firstly, and then a measurement impedance phasor at a protection installation position and an equivalent line impedance phasor of a fault line are obtained according to the fault type; respectively constructing a first distance model and a second distance model by using the measured impedance phasor at the protection installation position and the equivalent line impedance phasor of the fault line; establishing fault distance measurement models corresponding to different fault types by using the first distance model, the second distance model, the measured impedance phasor at the protection installation position and the equivalent line impedance phasor of the fault line; and based on the fault distance measurement model, outputting the distance between the fault point and the protection installation position under different fault types. On the basis of considering the cable line topology, the position of a fault point is calculated by using the change of specific electrical parameters generated when the cable has a fault.

Description

Technical Field

[0001] The present invention belongs to the technical field of distribution network fault detection, and in particular, relates to a distribution network cable fault distance measurement method and system. Background Art

[0002] The complexity and variability of urban distribution networks require them to have a high degree of stability and reliability, and it is necessary to improve the fault detection and location capabilities of the distribution networks and reduce power outage time.

[0003] In the prior art, the fault distance measurement technology of the distribution network mainly relies on traditional electrical measurement methods, such as voltage and current measurement and phase comparison. Although these methods can realize the detection and location of faults to a certain extent, they often have problems such as the need to operate after power failure, slow response time, and low accuracy. First, these methods often need to be operated after power failure, which not only increases the difficulty of the maintenance personnel's work, but also may cause further instability in the operation of the power grid. Secondly, the response time of these methods is slow, and it is difficult to meet the demand for rapid location of the fault point. Finally, due to the complexity of the urban distribution network, the accuracy of these traditional methods in practical applications is not ideal, and multiple measurements and verifications are often required, which increases the time and cost of fault repair. Moreover, there is a lack of methods for realizing online distance measurement of cable faults in urban distribution networks, and it is impossible to quickly and accurately locate the fault point, which is not conducive to shortening the repair time. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a distribution network cable fault distance measurement method and system, which calculates the location of the fault point by utilizing the changes in specific electrical parameters generated when the cable fails, based on the consideration of the cable line topology.

[0005] The present invention adopts the following technical solution.

[0006] The present invention proposes a distribution network cable fault distance measurement method, comprising:

[0007] Collect the fault component voltage at the protection installation location, and start fault distance measurement when the fault component voltage is greater than the set threshold value;

[0008] After starting the fault distance measurement, the fault type is first obtained, and then the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line are obtained according to the fault type; the first distance model and the second distance model are respectively constructed using the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line;

[0009] A fault distance measurement model corresponding to different fault types is established by using the first distance model, the second distance model, the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line; based on the fault distance measurement model, the distance between the fault point and the protection installation under different fault types is output.

[0010] The method also includes:

[0011] The distribution network operating parameters under different fault types are obtained, and the measured impedance phasor of the protection installation under different fault types is calculated using the distribution network operating parameters under different fault types, the equivalent line impedance phasor of the fault line, and the distance between the fault point and the protection installation; when the measured impedance phasor is less than the set impedance phasor of the distance protection, the distance between the fault point and the protection installation is sent to the distance protection.

[0012] Preferably, the fault component voltage collected at the protection installation includes: a fault component phase-to-phase voltage and a fault component phase voltage;

[0013] Fault distance measurement starts when the following equation holds:

[0014]

[0015] In the formula, To protect the fault component phase-to-phase voltage at the installation, is the fault component phase voltage at the protection installation, and ε is the threshold value.

[0016] Preferably, the first distance model and the second distance model are constructed respectively using the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line, and they respectively satisfy the following relationship:

[0017]

[0018] Where A(α) is the first distance model; B(α) is the second distance model; α is the ratio of the distance m between the fault point and the protection installation location to the total line length L. Z m is the measured impedance of the protection installation under different fault types; Z L is the equivalent line impedance of the fault line; The measured impedance phase angle at the protection installation under different fault types; is the equivalent line impedance angle of the fault line, and |·| is the modulus of the phase quantity.

[0019] Preferably, the fault location models corresponding to different fault types satisfy the following relationship:

[0020]

[0021] Where m is the distance between the fault point and the protection installation, and L is the total length of the fault line.

[0022] Preferably, under a single-phase grounding fault, the distribution network operation parameters obtained include: the grounding transition resistance of the single-phase grounding fault, the fault phase current measurement value and its zero-sequence component at the protection installation after the single-phase grounding fault occurs, the zero-sequence component of the equivalent impedance phasor on the fault line system side, the zero-sequence component of the equivalent impedance phasor on the load side of the fault line, and the zero-sequence component and positive-sequence component of the equivalent line impedance phasor of the fault line;

[0023] Using the distribution network operating parameters under a single-phase grounding fault, the equivalent line impedance phasor of the fault line under a single-phase grounding fault, and the distance between the fault point and the protection installation, the measured impedance phasor at the protection installation under a single-phase grounding fault is calculated using the following relationship:

[0024]

[0025] In the formula, It is the measured impedance phase quantity at the protection installation under single-phase ground fault; is the equivalent line impedance phasor of the fault line under single-phase grounding fault, is the zero-sequence component of the equivalent line impedance phasor of the fault line under a single-phase grounding fault; is the ground transition resistance of single-phase ground fault; It is the fault phase current measurement value at the protection installation after a single-phase grounding fault occurs; It is the zero-sequence component of the fault phase current measurement value on the fault line at the protection installation after a single-phase grounding fault occurs; is the zero-sequence component of the equivalent impedance phasor on the fault line system side; is the zero-sequence component of the equivalent impedance phasor on the load side of the fault line; is the positive sequence component of the equivalent line impedance phasor of the fault line; k0 is the line zero sequence compensation coefficient, satisfying α is the ratio of the distance m between the fault point and the protection installation to the total line length L.

[0026] When the measured impedance phasor at the protection installation under a single-phase grounding fault is less than the set impedance phasor of the distance protection, the distance between the single-phase grounding fault point and the protection installation is sent to the distance protection.

[0027] Preferably, under a two-phase short-circuit fault, the distribution network operation parameters obtained include: the phase-to-phase transition resistance of the two-phase short-circuit fault, the phase-to-phase current of the two faulty phases after the two-phase short-circuit fault occurs, and the phase-to-phase current of the two faulty phases on the fault branch after the two-phase short-circuit fault occurs;

[0028] Using the distribution network operating parameters under a two-phase short-circuit fault, the equivalent line impedance phasor of the fault line under a two-phase short-circuit fault, and the distance between the fault point and the protection installation, the measured impedance phasor at the protection installation under a two-phase short-circuit fault is calculated using the following relationship:

[0029]

[0030] In the formula, is the measured impedance phasor at the protection installation under two-phase short-circuit fault, is the equivalent line impedance phasor of the fault line under two-phase short-circuit fault, is the phase-to-phase transition resistance of a two-phase short-circuit fault, is the phase-to-phase current of the two fault phases after a two-phase short-circuit fault occurs, It is the phase-to-phase current of the two fault phases on the fault branch after a two-phase phase-to-phase short circuit fault occurs;

[0031] When the measured impedance phasor at the protection installation under a two-phase short-circuit fault is less than the set impedance phasor of the distance protection, the distance between the two-phase short-circuit fault point and the protection installation is sent to the distance protection.

[0032] Preferably, under a two-phase interphase ground short circuit fault, the distribution network operation parameters obtained include: the phase-to-phase transition resistance of the two-phase interphase ground short circuit fault, the ground transition resistance of the two-phase interphase ground short circuit fault, the phase-to-phase current of the two fault phases after the two-phase interphase ground short circuit fault occurs, and the phase-to-phase current of the two fault phases on the fault branch after the two-phase interphase ground short circuit fault occurs;

[0033] Using the distribution network operating parameters under a two-phase interphase to ground short circuit fault, the equivalent line impedance phasor of the fault line under a two-phase interphase to ground short circuit fault, and the distance between the fault point and the protection installation, the measured impedance phasor at the protection installation under a two-phase interphase to ground short circuit fault is calculated using the following relationship:

[0034]

[0035] In the formula, is the measured impedance phasor at the protection installation under two-phase inter-phase short-circuit fault, is the equivalent line impedance phasor of the fault line under two-phase-to-phase ground short circuit fault, is the phase-to-phase transition resistance of a two-phase phase-to-ground short circuit fault, is the ground transition resistance of the two-phase inter-phase ground short circuit fault, is the phase-to-phase current of the two fault phases after a two-phase phase-to-ground short circuit fault occurs. It is the phase-to-phase current of the two fault phases on the fault branch after a two-phase phase-to-ground short circuit fault occurs;

[0036] When the measured impedance phasor at the protection installation under a two-phase inter-phase to ground short circuit fault is less than the set impedance phasor of the distance protection, the distance protection is sent the distance protection with the distance between the two-phase inter-phase to ground short circuit fault point and the protection installation.

[0037] Preferably, under a three-phase grounding fault, the distribution network operation parameters obtained include: the grounding transition resistance of the three-phase grounding fault, the phase-to-phase current of any two fault phases after the three-phase grounding fault occurs, and the phase-to-phase current of any two fault phases on the fault branch after the three-phase grounding fault occurs;

[0038] Using the distribution network operating parameters under a three-phase grounding fault, the equivalent line impedance phasor of the fault line under a three-phase grounding fault, and the distance between the fault point and the protection installation, the measured impedance phasor at the protection installation under a three-phase grounding fault is calculated using the following relationship:

[0039]

[0040] In the formula, is the measured impedance phasor at the protection installation under three-phase ground fault, is the equivalent line impedance phasor of the fault line under three-phase grounding fault, is the ground transition resistance of three-phase ground fault, is the phase-to-phase current of any two fault phases after a three-phase grounding fault occurs, It is the phase-to-phase current of any two fault phases on the fault branch after a three-phase grounding fault occurs;

[0041] When the measured impedance phasor at the protection installation under a three-phase grounding fault is less than the set impedance phasor of the distance protection, the distance between the three-phase grounding fault point and the protection installation is sent to the distance protection.

[0042] The present invention also proposes a distribution network cable fault distance measurement system, comprising:

[0043] Fault distance measurement start-up module, model building module, fault distance measurement module;

[0044] The fault distance measurement start module is used to collect the fault component voltage at the protection installation location. When the fault component voltage is greater than the set threshold value, the fault distance measurement is started;

[0045] A model building module is used to first obtain the fault type after starting the fault distance measurement, and then obtain the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line according to the fault type; and construct the first distance model and the second distance model respectively by using the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line;

[0046] The fault distance measurement module is used to establish a fault distance measurement model corresponding to different fault types by using the first distance model, the second distance model, the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line; based on the fault distance measurement model, the distance between the fault point and the protection installation under different fault types is output.

[0047] The system also includes: a measurement impedance phasor calculation module;

[0048] The measured impedance phasor calculation module is used to obtain the distribution network operating parameters under different fault types, and calculate the measured impedance phasor of the protection installation under different fault types by using the distribution network operating parameters under different fault types, the equivalent line impedance phasor of the fault line and the distance between the fault point and the protection installation; when the measured impedance phasor is less than the set impedance phasor of the distance protection, the distance between the fault point and the protection installation is sent to the distance protection.

[0049] A terminal comprises a processor and a storage medium; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the method.

[0050] A computer-readable storage medium stores a computer program, which implements the steps of the method when executed by a processor.

[0051] The beneficial effects of the present invention are that, compared with the prior art, at least the method proposed by the present invention overcomes the influence of transition resistance and equivalent impedance of the line opposite end on the ranging accuracy in principle, and the ranging accuracy is good in the case of high-resistance faults, and the relative error is less than 0.5% at 200Ω. In particular, for high-resistance grounding faults, the fault ranging method proposed by the present invention can improve the accuracy and speed of fault ranging.

[0052] According to the obtained fault distance, after considering the operating conditions and limitations of the actual distribution network, including non-ideal characteristics of the line, noise interference and other factors, the measured impedance phasor at the protection installation is recalculated for the judgment of the start of distance protection. Therefore, the method proposed in the present invention can not only improve the accuracy and response speed of fault location, but also help to save the repair time after the cable line fault, shorten the power grid fault recovery time, and improve the overall stability and reliability of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 A flow chart of a method for measuring cable fault distance in a distribution network proposed by the present invention;

[0054] Figure 2 The schematic wiring diagram of a regional power distribution network in an embodiment of the present invention is shown in FIG. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0056] The present invention proposes a method for measuring the distance between cable faults in a distribution network. Figure 1 As shown, including:

[0057] Step 1: collect the fault component voltage at the protection installation location, and when the fault component voltage is greater than the set threshold value, start the fault distance measurement.

[0058] Specifically, the collected fault component voltages at the protection installation include but are not limited to: fault component phase-to-phase voltages and fault component phase voltages.

[0059] During normal operation, the phase-to-phase voltage and the phase-to-phase voltage of the fault component are both zero; after a fault occurs, the grid voltage drops rapidly, and the phase-to-phase voltage and the phase-to-phase voltage of the fault component increase. This feature is used to construct the starting criterion for fault distance measurement. When the following equation is true, the fault distance measurement starts:

[0060]

[0061] In the formula, To protect the fault component phase-to-phase voltage at the installation, is the fault component phase voltage at the protection installation, and ε is the threshold value.

[0062] To ensure a certain margin, in a non-limiting preferred embodiment, ε is taken as 0.1 kV. In actual engineering applications, it can be adjusted according to the voltage level, measurement device error and reliability requirements.

[0063] Using the fault component phase-to-phase voltage and the fault component phase voltage as the starting criterion for fault distance measurement can achieve synchronization and coordination with the starting of distance protection.

[0064] Step 2: After starting the fault distance measurement, first obtain the fault type, and then obtain the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line according to the fault type; use the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line to construct the first distance model and the second distance model respectively.

[0065] Specifically, the measured impedance phasors at the protection installations corresponding to different fault types and the equivalent line impedance phasors of the faulty lines are different and need to be calculated separately according to the fault types.

[0066] The first distance model and the second distance model are constructed using the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line, respectively, satisfying the following relationships:

[0067]

[0068] Where A(α) is the first distance model; B(α) is the second distance model; α is the ratio of the distance m between the fault point and the protection installation location to the total line length L. Z m is the measured impedance of the protection installation under different fault types; Z L is the equivalent line impedance of the fault line; The measured impedance phase angle at the protection installation under different fault types; is the equivalent line impedance angle of the fault line, and |·| is the modulus of the phase quantity.

[0069] Step 3, using the first distance model, the second distance model, the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line, establish a fault distance model corresponding to different fault types; based on the fault distance model, output the distance between the fault point and the protection installation under different fault types.

[0070] Specifically, the fault location models corresponding to different fault types satisfy the following relationship:

[0071]

[0072] Where m is the distance between the fault point and the protection installation, and L is the total length of the fault line.

[0073] Step 4, obtain the distribution network operating parameters under different fault types, and use the distribution network operating parameters under different fault types, the equivalent line impedance phasor of the fault line, and the distance between the fault point and the protection installation to calculate the measured impedance phasor of the protection installation under different fault types; when the measured impedance phasor is less than the set impedance phasor of the distance protection, send the distance between the fault point and the protection installation to the distance protection.

[0074] Specifically, step 4 includes:

[0075] Step 4.1, under a single-phase grounding fault, the distribution network operation parameters obtained include: the grounding transition resistance of the single-phase grounding fault, the fault phase current measurement value and its zero-sequence component at the protection installation after the single-phase grounding fault occurs, the zero-sequence component of the equivalent impedance phasor on the system side of the fault line, the zero-sequence component of the equivalent impedance phasor on the load side of the fault line, and the zero-sequence component and positive-sequence component of the equivalent line impedance phasor of the fault line;

[0076] Using the distribution network operating parameters under a single-phase grounding fault, the equivalent line impedance phasor of the fault line under a single-phase grounding fault, and the distance between the fault point and the protection installation, the measured impedance phasor at the protection installation under a single-phase grounding fault is calculated using the following relationship:

[0077]

[0078] In the formula, It is the measured impedance phase quantity at the protection installation under single-phase ground fault; is the equivalent line impedance phasor of the fault line under single-phase grounding fault, is the zero-sequence component of the equivalent line impedance phasor of the fault line under a single-phase grounding fault; is the ground transition resistance of single-phase ground fault; It is the fault phase current measurement value at the protection installation after a single-phase grounding fault occurs; It is the zero-sequence component of the fault phase current measurement value on the fault line at the protection installation after a single-phase grounding fault occurs; is the zero-sequence component of the equivalent impedance phasor on the fault line system side; is the zero-sequence component of the equivalent impedance phasor on the load side of the fault line; is the positive sequence component of the equivalent line impedance phasor of the fault line; k0 is the line zero sequence compensation coefficient, satisfying α is the ratio of the distance m between the fault point and the protection installation to the total line length L.

[0079] When the measured impedance phasor at the protection installation under a single-phase grounding fault is less than the set impedance phasor of the distance protection, the distance between the single-phase grounding fault point and the protection installation is sent to the distance protection.

[0080] Step 4.2, under a two-phase short-circuit fault, the distribution network operation parameters obtained include: the phase-to-phase transition resistance of the two-phase short-circuit fault, the phase-to-phase current of the two fault phases after the two-phase short-circuit fault occurs, and the phase-to-phase current of the two fault phases on the fault branch after the two-phase short-circuit fault occurs;

[0081] Using the distribution network operating parameters under a two-phase short-circuit fault, the equivalent line impedance phasor of the fault line under a two-phase short-circuit fault, and the distance between the fault point and the protection installation, the measured impedance phasor at the protection installation under a two-phase short-circuit fault is calculated using the following relationship:

[0082]

[0083] In the formula, is the measured impedance phasor at the protection installation under two-phase short-circuit fault, is the equivalent line impedance phasor of the fault line under two-phase short-circuit fault, is the phase-to-phase transition resistance of a two-phase short-circuit fault, is the phase-to-phase current of the two fault phases after a two-phase short-circuit fault occurs, It is the phase-to-phase current of the two faulty phases on the fault branch after a two-phase phase-to-phase short circuit fault occurs.

[0084] When the measured impedance phasor at the protection installation under a two-phase short-circuit fault is less than the set impedance phasor of the distance protection, the distance between the two-phase short-circuit fault point and the protection installation is sent to the distance protection.

[0085] Step 4.3, under the two-phase interphase ground short circuit fault, the distribution network operation parameters obtained include: the phase-to-phase transition resistance of the two-phase interphase ground short circuit fault, the ground transition resistance of the two-phase interphase ground short circuit fault, the phase-to-phase current of the two fault phases after the two-phase interphase ground short circuit fault occurs, and the phase-to-phase current of the two fault phases on the fault branch after the two-phase interphase ground short circuit fault occurs;

[0086] Using the distribution network operating parameters under a two-phase interphase to ground short circuit fault, the equivalent line impedance phasor of the fault line under a two-phase interphase to ground short circuit fault, and the distance between the fault point and the protection installation, the measured impedance phasor at the protection installation under a two-phase interphase to ground short circuit fault is calculated using the following relationship:

[0087]

[0088] In the formula, is the measured impedance phasor at the protection installation under two-phase inter-phase short-circuit fault, is the equivalent line impedance phasor of the fault line under two-phase-to-phase ground short circuit fault, is the phase-to-phase transition resistance of a two-phase phase-to-ground short circuit fault, is the ground transition resistance of the two-phase inter-phase ground short circuit fault, is the phase-to-phase current of the two fault phases after a two-phase phase-to-ground short circuit fault occurs. It is the phase-to-phase current of the two faulty phases on the fault branch after a two-phase-to-phase ground short circuit occurs.

[0089] When the measured impedance phasor at the protection installation under a two-phase inter-phase to ground short circuit fault is less than the set impedance phasor of the distance protection, the distance protection is sent the distance protection with the distance between the two-phase inter-phase to ground short circuit fault point and the protection installation.

[0090] Step 4.4, under a three-phase grounding fault, the distribution network operation parameters obtained include: grounding transition resistance of the three-phase grounding fault, phase-to-phase currents of any two fault phases after the three-phase grounding fault occurs, and phase-to-phase currents of any two fault phases on the fault branch after the three-phase grounding fault occurs;

[0091] Using the distribution network operating parameters under a three-phase grounding fault, the equivalent line impedance phasor of the fault line under a three-phase grounding fault, and the distance between the fault point and the protection installation, the measured impedance phasor at the protection installation under a three-phase grounding fault is calculated using the following relationship:

[0092]

[0093] In the formula, is the measured impedance phasor at the protection installation under three-phase ground fault, is the equivalent line impedance phasor of the fault line under three-phase grounding fault, is the ground transition resistance of three-phase ground fault, is the phase-to-phase current of any two fault phases after a three-phase grounding fault occurs, It is the phase-to-phase current between any two fault phases on the fault branch after a three-phase grounding fault occurs.

[0094] When the measured impedance phasor at the protection installation under a three-phase grounding fault is less than the set impedance phasor of the distance protection, the distance between the three-phase grounding fault point and the protection installation is sent to the distance protection.

[0095] by Figure 2 Taking the distribution network of a certain area as an example, the model is constructed using PSCAD software for simulation. The voltage level of the distribution network is 35kV, and the equivalent impedance parameters of the power supply are: Z E1 =Z E2 =0.5+j9.7Ω, Z E0 =1+j21.6Ω. The parameters of the single-ended power supply multi-stage series power transmission line are set as follows: Z L1 =Z L2 =0.012+j0.126Ω / km, Z L0 =0.02+j0.34Ω / km. The length of the line AM section is 15km, the length of the line MN section is 80km, and the length of the line ND section is 15km. The busbars M, N, and D sections are all connected to loads with a size of 1.8MVA and a power factor of 0.9. A fault point is set on line MN. The time difference is less than 0.1pu / ms, and the simulation data is imported into MATLAB. The fault distance measurement program is written using MALAB, thereby verifying the fault distance measurement method proposed in the present invention.

[0096] The relative error calculation formula of fault distance measurement is:

[0097]

[0098] The following table gives the ranging results and errors of the ranging algorithm based on the fault additional impedance angle when a single-ended power network has a single-phase grounding fault, a two-phase phase-to-phase fault, a two-phase grounding fault and a three-phase grounding fault, under different fault distances and transition resistances.

[0099] Table 1 Fault distances obtained based on the method proposed in the present invention when a single-phase grounding fault occurs

[0100]

[0101] Table 2 Fault distances obtained based on the method proposed in the present invention when two-phase short circuit fault occurs

[0102]

[0103] Table 3 Fault distances obtained based on the method proposed in the present invention when two-phase short circuit grounding fault occurs

[0104]

[0105] Table 3 Fault distances obtained based on the method proposed in the present invention when a three-phase grounding fault occurs

[0106]

[0107] The present invention also proposes a distribution network cable fault distance measurement system, comprising:

[0108] Fault distance measurement start-up module, model building module, fault distance measurement module;

[0109] The fault distance measurement start module is used to collect the fault component voltage at the protection installation location. When the fault component voltage is greater than the set threshold value, the fault distance measurement is started;

[0110] A model building module is used to first obtain the fault type after starting the fault distance measurement, and then obtain the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line according to the fault type; and construct the first distance model and the second distance model respectively by using the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line;

[0111] The fault distance measurement module is used to establish a fault distance measurement model corresponding to different fault types by using the first distance model, the second distance model, the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line; based on the fault distance measurement model, the distance between the fault point and the protection installation under different fault types is output.

[0112] The system also includes: a measurement impedance phasor calculation module;

[0113] The measured impedance phasor calculation module is used to obtain the distribution network operating parameters under different fault types, and calculate the measured impedance phasor of the protection installation under different fault types by using the distribution network operating parameters under different fault types, the equivalent line impedance phasor of the fault line and the distance between the fault point and the protection installation; when the measured impedance phasor is less than the set impedance phasor of the distance protection, the distance between the fault point and the protection installation is sent to the distance protection.

[0114] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0115] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0116] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0117] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for measuring cable fault distance in a distribution network, characterized in that: include: Collect the fault component voltage at the protection installation location, and start fault distance measurement when the fault component voltage is greater than the set threshold value; After starting the fault distance measurement, the fault type is first obtained, and then the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line are obtained according to the fault type; the first distance model and the second distance model are respectively constructed using the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line; Establishing fault distance measurement models corresponding to different fault types by using the first distance model, the second distance model, the measured impedance phasor at the protection installation, and the equivalent line impedance phasor of the fault line; Based on the fault distance measurement model, the distance between the fault point and the protection installation under different fault types is output.

2. The method for measuring cable fault distance in a distribution network according to claim 1, characterized in that: The method further comprises: The distribution network operating parameters under different fault types are obtained, and the measured impedance phasor of the protection installation under different fault types is calculated using the distribution network operating parameters under different fault types, the equivalent line impedance phasor of the fault line, and the distance between the fault point and the protection installation; when the measured impedance phasor is less than the set impedance phasor of the distance protection, the distance between the fault point and the protection installation is sent to the distance protection.

3. The method for measuring cable fault distance in a distribution network according to claim 1, characterized in that: The fault component voltage collected at the protection installation includes: fault component phase-to-phase voltage and fault component phase voltage; Fault distance measurement starts when the following equation holds: In the formula, To protect the fault component phase-to-phase voltage at the installation, is the fault component phase voltage at the protection installation, and ε is the threshold value.

4. The method for measuring cable fault distance in a distribution network according to claim 2, characterized in that: The first distance model and the second distance model are constructed using the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line, respectively, satisfying the following relationships: Where A(α) is the first distance model; B(α) is the second distance model; α is the ratio of the distance m between the fault point and the protection installation location to the total line length L. Z m is the measured impedance of the protection installation under different fault types; Z L is the equivalent line impedance of the fault line; The measured impedance phase angle at the protection installation under different fault types; is the equivalent line impedance angle of the fault line, and |·| is the modulus of the phase quantity.

5. The method for measuring cable fault distance in a distribution network according to claim 4, characterized in that: The fault location model corresponding to different fault types satisfies the following relationship: Where m is the distance between the fault point and the protection installation, and L is the total length of the fault line.

6. The method for measuring cable fault distance in a distribution network according to claim 5, characterized in that: Under a single-phase grounding fault, the distribution network operation parameters obtained include: the grounding transition resistance of the single-phase grounding fault, the fault phase current measurement value and its zero-sequence component at the protection installation after the single-phase grounding fault occurs, the zero-sequence component of the equivalent impedance phasor on the system side of the fault line, the zero-sequence component of the equivalent impedance phasor on the load side of the fault line, and the zero-sequence component and positive-sequence component of the equivalent line impedance phasor of the fault line; Using the distribution network operating parameters under a single-phase grounding fault, the equivalent line impedance phasor of the fault line under a single-phase grounding fault, and the distance between the fault point and the protection installation, the measured impedance phasor at the protection installation under a single-phase grounding fault is calculated using the following relationship: In the formula, It is the measured impedance phase quantity at the protection installation under single-phase ground fault; is the equivalent line impedance phasor of the fault line under single-phase grounding fault, is the zero-sequence component of the equivalent line impedance phasor of the fault line under a single-phase grounding fault; is the ground transition resistance of single-phase ground fault; It is the fault phase current measurement value at the protection installation after a single-phase grounding fault occurs; It is the zero-sequence component of the fault phase current measurement value on the fault line at the protection installation after a single-phase grounding fault occurs; is the zero-sequence component of the equivalent impedance phasor on the fault line system side; is the zero-sequence component of the equivalent impedance phasor on the load side of the fault line; is the positive sequence component of the equivalent line impedance phasor of the fault line; k0 is the line zero sequence compensation coefficient, satisfying α is the ratio of the distance m between the fault point and the protection installation to the total line length L. When the measured impedance phasor at the protection installation under a single-phase grounding fault is less than the set impedance phasor of the distance protection, the distance between the single-phase grounding fault point and the protection installation is sent to the distance protection.

7. The method for measuring cable fault distance in a distribution network according to claim 5, characterized in that: Under a two-phase short-circuit fault, the distribution network operation parameters obtained include: the phase-to-phase transition resistance of the two-phase short-circuit fault, the phase-to-phase current of the two fault phases after the two-phase short-circuit fault occurs, and the phase-to-phase current of the two fault phases on the fault branch after the two-phase short-circuit fault occurs; Using the distribution network operating parameters under a two-phase short-circuit fault, the equivalent line impedance phasor of the fault line under a two-phase short-circuit fault, and the distance between the fault point and the protection installation, the measured impedance phasor at the protection installation under a two-phase short-circuit fault is calculated using the following relationship: In the formula, is the measured impedance phasor at the protection installation under two-phase short-circuit fault, is the equivalent line impedance phasor of the fault line under two-phase short-circuit fault, is the phase-to-phase transition resistance of a two-phase short-circuit fault, is the phase-to-phase current of the two fault phases after a two-phase short-circuit fault occurs, It is the phase-to-phase current of the two fault phases on the fault branch after a two-phase phase-to-phase short circuit fault occurs; When the measured impedance phasor at the protection installation under a two-phase short-circuit fault is less than the set impedance phasor of the distance protection, the distance between the two-phase short-circuit fault point and the protection installation is sent to the distance protection.

8. The method for measuring cable fault distance in a distribution network according to claim 5, characterized in that: Under the two-phase interphase ground short circuit fault, the distribution network operation parameters obtained include: the phase-to-phase transition resistance of the two-phase interphase ground short circuit fault, the ground transition resistance of the two-phase interphase ground short circuit fault, the phase-to-phase current of the two fault phases after the two-phase interphase ground short circuit fault occurs, and the phase-to-phase current of the two fault phases on the fault branch after the two-phase interphase ground short circuit fault occurs; Using the distribution network operating parameters under a two-phase interphase to ground short circuit fault, the equivalent line impedance phasor of the fault line under a two-phase interphase to ground short circuit fault, and the distance between the fault point and the protection installation, the measured impedance phasor at the protection installation under a two-phase interphase to ground short circuit fault is calculated using the following relationship: In the formula, is the measured impedance phasor at the protection installation under two-phase inter-phase short-circuit fault, is the equivalent line impedance phasor of the fault line under two-phase-to-phase ground short circuit fault, is the phase-to-phase transition resistance of a two-phase phase-to-ground short circuit fault, is the ground transition resistance of the two-phase inter-phase ground short circuit fault, is the phase-to-phase current of the two fault phases after a two-phase phase-to-ground short circuit fault occurs. It is the phase-to-phase current of the two fault phases on the fault branch after a two-phase phase-to-ground short circuit fault occurs; When the measured impedance phasor at the protection installation under a two-phase inter-phase to ground short circuit fault is less than the set impedance phasor of the distance protection, the distance protection is sent the distance protection with the distance between the two-phase inter-phase to ground short circuit fault point and the protection installation.

9. The method for measuring cable fault distance in a distribution network according to claim 5, characterized in that: Under a three-phase grounding fault, the distribution network operation parameters obtained include: the grounding transition resistance of the three-phase grounding fault, the phase-to-phase current of any two fault phases after the three-phase grounding fault occurs, and the phase-to-phase current of any two fault phases on the fault branch after the three-phase grounding fault occurs; Using the distribution network operating parameters under a three-phase grounding fault, the equivalent line impedance phasor of the fault line under a three-phase grounding fault, and the distance between the fault point and the protection installation, the measured impedance phasor at the protection installation under a three-phase grounding fault is calculated using the following relationship: In the formula, is the measured impedance phasor at the protection installation under three-phase ground fault, is the equivalent line impedance phasor of the fault line under three-phase grounding fault, is the ground transition resistance of three-phase ground fault, is the phase-to-phase current of any two fault phases after a three-phase grounding fault occurs, It is the phase-to-phase current of any two fault phases on the fault branch after a three-phase grounding fault occurs; When the measured impedance phasor at the protection installation under a three-phase grounding fault is less than the set impedance phasor of the distance protection, the distance between the three-phase grounding fault point and the protection installation is sent to the distance protection.

10. A distribution network cable fault distance measurement system, characterized in that: include: Fault distance measurement start-up module, model building module, fault distance measurement module; The fault distance measurement start module is used to collect the fault component voltage at the protection installation location. When the fault component voltage is greater than the set threshold value, the fault distance measurement is started; A model building module is used to first obtain the fault type after starting the fault distance measurement, and then obtain the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line according to the fault type; and construct the first distance model and the second distance model respectively by using the measured impedance phasor at the protection installation and the equivalent line impedance phasor of the fault line; A fault distance measurement module, for establishing a fault distance measurement model corresponding to different fault types by using the first distance model, the second distance model, the measured impedance phasor at the protection installation, and the equivalent line impedance phasor of the fault line; Based on the fault distance measurement model, the distance between the fault point and the protection installation under different fault types is output.

11. The distribution network cable fault distance measurement system according to claim 10, characterized in that: The system further comprises: a measurement impedance phasor calculation module; The measured impedance phasor calculation module is used to obtain the distribution network operating parameters under different fault types, and calculate the measured impedance phasor of the protection installation under different fault types by using the distribution network operating parameters under different fault types, the equivalent line impedance phasor of the fault line and the distance between the fault point and the protection installation; when the measured impedance phasor is less than the set impedance phasor of the distance protection, the distance between the fault point and the protection installation is sent to the distance protection.

12. A terminal comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 9.

13. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 9 are implemented.

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