Distribution line fault point positioning method and device

Abstract

The invention discloses a distribution line fault point positioning method and device, and relates to the field of power distribution networks, and the method comprises the steps: constructing a plurality of virtual fault points, and determining the zero-sequence current before the fault point and the zero-sequence voltage of the fault point of each virtual fault point based on the head-end zero-sequence voltage, the head-end zero-sequence current and the tail-end zero-sequence current of a fault section; determining the phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage of the virtual fault point; and taking the virtual fault point with the phase difference smaller than the judgment threshold as a fault point, and determining the fault distance between the fault point and the head end of the fault section. Because the zero-sequence voltage and the zero-sequence current of each virtual fault point have a phase constraint relationship, when the voltage phase and the current phase are approximate, the virtual fault point is proved to be an actual fault point. Therefore, a plurality of virtual fault points are constructed, the phase difference between the zero-sequence voltage and the zero-sequence current is respectively calculated, additional measurement equipment is not needed, and the calculation result is simpler.

Description

Technical Field

[0001] This invention relates to the field of power distribution networks, and in particular to a method and apparatus for locating fault points in power distribution lines. Background Technology

[0002] When a single-phase ground fault occurs in a power distribution line, it is often necessary to determine the location of the fault point in order to address it. Among related technologies, the main method for locating fault points in power distribution lines is the traveling wave method. The core principle of the traveling wave method is to utilize the characteristics of the traveling wave generated when a fault occurs and its propagation in the line. By analyzing parameters such as the arrival time and waveform characteristics of the traveling wave, the location of the fault point can be calculated. However, the traveling wave method requires additional high-precision detection and timing devices, which is not conducive to on-site implementation. Summary of the Invention

[0003] The purpose of this invention is to provide a method and apparatus for locating fault points in power distribution lines. Multiple virtual fault points are constructed, and the phase difference between zero-sequence voltage and zero-sequence current is calculated for each virtual point. No additional measuring equipment is required, and the calculation results are simpler. When the voltage phase and current phase are approximately the same, it is proven that this virtual fault point is the actual fault point.

[0004] To solve the above-mentioned technical problems, the present invention provides a method for locating fault points in power distribution lines, comprising:

[0005] Determine the zero-sequence voltage, zero-sequence current and zero-sequence current at the beginning and end of the fault section of the power distribution line, where a fault point exists in the fault section;

[0006] Multiple virtual fault points are constructed, and the zero-sequence current before the fault point and the zero-sequence voltage at the beginning of the fault section, the zero-sequence current at the beginning of the fault section, and the zero-sequence current at the end of the fault section are determined.

[0007] Determine the phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point;

[0008] Virtual fault points with phase differences less than the judgment threshold are taken as fault points, and the fault distance between the fault point and the beginning of the fault section is determined.

[0009] On the other hand, determining the zero-sequence voltage, zero-sequence current at the beginning of the fault section of the power distribution line, and zero-sequence current at the end of the fault section includes:

[0010] After acquiring the fault occurrence time, at least two acquisition cycles are required for the discrete beginning zero-sequence voltage, discrete beginning zero-sequence current, and discrete end zero-sequence current of the fault segment.

[0011] The zero-sequence voltage, zero-sequence current and zero-sequence current at the beginning and end of the fault section in the two acquisition cycles are fitted to obtain the zero-sequence voltage, zero-sequence current and zero-sequence current at the beginning and end.

[0012] The expressions for the zero-sequence voltage at the beginning, the zero-sequence current at the beginning, and the zero-sequence current at the end are as follows:

[0013] ;

[0014] in, Let M be the zero-sequence current at time t. Let M be the zero-sequence current at time t. instantaneous amplitude, , Let M be the zero-sequence current at time t. The instantaneous initial phase, , Let M be the zero-sequence current at time t. The magnitude of the cosine function term, Let M be the zero-sequence current at time t. The magnitude of the sine function term, Let be the zero-sequence voltage at terminal M at time t. Let M be the zero-sequence voltage at time t. instantaneous amplitude, Let M be the zero-sequence voltage at time t. The instantaneous initial phase, Let M be the zero-sequence voltage at time t. The magnitude of the cosine function term, Let M be the zero-sequence voltage at time t. The magnitude of the sine function term, Let be the zero-sequence current at terminal N at time t. Let N be the zero-sequence current at time t. instantaneous amplitude, Let N be the zero-sequence current at time t. The instantaneous initial phase, Let N be the zero-sequence current at time t. The magnitude of the cosine function term, Let N be the zero-sequence current at time t. The magnitude of the sine function term, Let N be the zero-sequence voltage at time t. Let N be the zero-sequence voltage at time t. instantaneous amplitude, Let N be the zero-sequence voltage at time t. The instantaneous initial phase, Let N be the zero-sequence voltage at time t. The magnitude of the cosine function term, Let N be the zero-sequence voltage at time t. The magnitude of the sin function term, wherein the fault segment is the segment with M as the beginning and N as the end;

[0015] Based on the zero-sequence voltage at the beginning of the fault section, the zero-sequence current at the beginning of the fault section, and the zero-sequence current at the end of the fault section, the zero-sequence current before the fault point and the zero-sequence voltage at the fault point are determined, including:

[0016] Based on the zero-sequence voltage, zero-sequence current and zero-sequence current at the beginning and end of the continuous fault sections, the zero-sequence current before the fault point and the zero-sequence voltage at the fault point of each virtual fault point are determined.

[0017] On the other hand, multiple virtual fault points are constructed, and the zero-sequence current before the fault point and the zero-sequence voltage at the fault point are determined based on the zero-sequence voltage at the beginning of the fault section, the zero-sequence current at the beginning of the fault section, and the zero-sequence current at the end of the fault section, including:

[0018] Multiple virtual fault points are constructed, wherein the distance between any two adjacent virtual fault points is . And there is a transition resistance;

[0019] Based on the zero-sequence voltage and zero-sequence current at the beginning of the fault section, the virtual fault point-before zero-sequence current and fault point-zero-sequence voltage of each virtual fault point are determined. The expressions for the virtual fault point-before zero-sequence current and fault point-zero-sequence voltage are as follows:

[0020] ;

[0021] in, The zero-sequence voltage at the virtual fault point. Let be the zero-sequence voltage at terminal M at time t. Let be the zero-sequence current at terminal M at time t. Let be the derivative of the zero-sequence current at terminal M at time t. As the first transition function, The zero-sequence current before the virtual fault point. Let R be the second transition function, l be the resistance per unit length, l be the length of the line, and L be the inductance per unit length.

[0022] On the other hand, the expression for the first transition function is:

[0023] ;

[0024] in, The length of the line is a power of 2q. To select p elements from q distinct elements, , The resistance per unit length is raised to the power of p. The value is the qp power of the inductance per unit length. Let j be the power of the capacitance per unit length. Let be the 2q-p derivative of the zero-sequence voltage at terminal M at time t. The conductance per unit length is raised to the power of q. Let be the 2q-p-1th order derivative of the zero-sequence voltage at terminal M at time t. The length of the line is a power of 2q+1. To select p elements from q+1 distinct elements, The value is the inductance per unit length raised to the power of q-p+1. It is the q-th power of the capacitance per unit length. Let be the 2q-p+1th derivative of the zero-sequence current at terminal M at time t. Let be the 2q-p derivative of the zero-sequence current at terminal M at time t;

[0025] The expression for the second transition function is:

[0026] ;

[0027] in, The length of the line is a power of 2q-1. To select p elements from q-1 distinct elements, The value is the qp⁻¹ power of the inductance per unit length. Let be the 2q-p-2nd order derivative of the zero-sequence voltage at terminal M at time t. The length of the line is a power of 2q. Let be the 2q-p derivative of the zero-sequence current at terminal M at time t. Let be the 2q-p-1 derivative of the zero-sequence current at terminal M at time t.

[0028] On the other hand, before determining the phase difference between the zero-sequence current and the zero-sequence voltage before the virtual fault point, the method further includes:

[0029] Determine the instantaneous amplitude of the zero-sequence voltage, the instantaneous amplitude of the zero-sequence current, and the instantaneous phase of the zero-sequence voltage and the instantaneous phase of the zero-sequence current of the transition resistance between each virtual fault point;

[0030] The expressions for the instantaneous amplitude of the zero-sequence voltage of the transition resistor and the instantaneous phase of the zero-sequence voltage of the transition resistor are as follows:

[0031] ;

[0032] in, The instantaneous amplitude of the zero-sequence voltage of the transition resistor is given. The first steady-state constant of the zero-sequence voltage of the transition resistance is... It is an exponential function of the decay of the zero-sequence voltage. The second steady-state constant of the zero-sequence voltage of the transition resistance is... The Hilbert transform corresponds to the exponential function of the decay of the zero-sequence voltage. The zero-sequence voltage instantaneous phase of the transition resistor;

[0033] The expressions for the instantaneous amplitude of the zero-sequence current of the transition resistor and the instantaneous phase of the zero-sequence current of the transition resistor are as follows:

[0034] ;

[0035] in, The instantaneous amplitude of the zero-sequence current of the transition resistor is given. The first steady-state constant of the zero-sequence current of the transition resistance is... It is an exponential function of the decay of the zero-sequence current. The second steady-state constant of the zero-sequence current of the transition resistance is... The Hilbert transform corresponds to the exponential function of the decay of the zero-sequence current. The zero-sequence current instantaneous phase of the transition resistor.

[0036] On the other hand, determining the phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point includes:

[0037] The phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point is determined, and the expression for the phase difference is:

[0038] ;

[0039] in, The phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage of the virtual fault point.

[0040] On the other hand, before identifying virtual fault points with phase differences less than a judgment threshold as fault points and determining the fault distance between the fault point and the beginning of the fault section, the method further includes:

[0041] Construct a virtual fault point search matrix, the expression of which is:

[0042] ;

[0043] in, For phase difference, The distance between any two adjacent virtual fault points is denoted as . Let n be the number of virtual fault points at the z-th sampling time. For N times at The sum of the instantaneous phase differences of the transition resistance voltage and current along the line length.

[0044] On the other hand, virtual fault points with phase differences less than a judgment threshold are taken as fault points, and the fault distance between the fault point and the beginning of the fault section is determined, including:

[0045] Obtain the phase difference of the first virtual fault point from the search matrix;

[0046] Determine if the phase difference of the first virtual fault point meets the requirements. , The threshold value is the threshold value used for judgment.

[0047] If satisfied, output the fault distance. .

[0048] On the other hand, it is determined whether the phase difference of the first virtual fault point satisfies the requirement. Following that, it also includes:

[0049] If not satisfied, then sequentially obtain the phase difference of the remaining virtual fault points and determine whether they are satisfied. ;

[0050] If satisfied, output the fault distance. .

[0051] To solve the above-mentioned technical problems, the present invention also provides a device for locating fault points in power distribution lines, comprising:

[0052] Memory, used to store computer programs;

[0053] A processor is used to implement the steps of the above-described method for locating fault points in power distribution lines when executing the computer program.

[0054] This application provides a method and apparatus for locating fault points in power distribution lines, relating to the field of power distribution networks. The method includes constructing multiple virtual fault points and determining the zero-sequence current before the fault point and the zero-sequence voltage at the fault point based on the zero-sequence voltage, zero-sequence current at the beginning of the fault section, and zero-sequence current at the end of the fault section; determining the phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point; identifying virtual fault points with a phase difference less than a judgment threshold as actual fault points, and determining the fault distance between the fault point and the beginning of the fault section. Since the zero-sequence voltage and zero-sequence current of each virtual fault point have a phase constraint relationship, when the voltage phase and current phase are approximately the same, it is proven that this virtual fault point is the actual fault point. Therefore, multiple virtual fault points are constructed, and the phase difference between the zero-sequence voltage and zero-sequence current is calculated separately, eliminating the need for additional measuring equipment and simplifying the calculation results. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 A flowchart of a method for locating fault points in a power distribution line provided by the present invention;

[0057] Figure 2 A structural schematic diagram of a fault point provided by the present invention;

[0058] Figure 3 A schematic diagram of a virtual fault point provided by the present invention;

[0059] Figure 4 This is a schematic diagram of the structure of a fault location device for power distribution lines provided by the present invention. Detailed Implementation

[0060] The core of this invention is to provide a method and apparatus for locating fault points in power distribution lines. Multiple virtual fault points are constructed, and the phase difference between zero-sequence voltage and zero-sequence current is calculated for each. No additional measuring equipment is required, and the calculation results are simpler. When the voltage phase and current phase are approximately the same, it is proven that this virtual fault point is the actual fault point.

[0061] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] Figure 1 A flowchart of a method for locating fault points in a power distribution line provided by the present invention includes:

[0063] S11: Determine the zero-sequence voltage, zero-sequence current and zero-sequence current at the beginning and end of the fault section of the power distribution line, and identify the fault point in the fault section.

[0064] S12: Construct multiple virtual fault points, and determine the zero-sequence current before the fault point and the zero-sequence voltage at the fault point based on the zero-sequence voltage at the beginning of the fault section, the zero-sequence current at the beginning of the fault section and the zero-sequence current at the end of the fault section.

[0065] S13: Determine the phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point;

[0066] S14: Take the virtual fault point with a phase difference less than the judgment threshold as the fault point, and determine the fault distance between the fault point and the beginning of the fault section.

[0067] Currently, the main methods for locating fault points in power distribution lines include the traveling wave method and the fault analysis method. The traveling wave method has high ranging accuracy but requires additional high-precision detection and timing devices, making it less suitable for on-site implementation. The fault analysis method can directly establish a quantitative relationship between fault distance and electrical quantities from the voltage and current information measured and recorded on the feeder. Depending on the analysis object, it can be divided into frequency domain calculation methods based on steady-state power frequency components and time domain calculation methods based on transient full-band components. The fault analysis method only requires voltage and current measurement information on the line, making it more suitable for engineering implementation. However, the actual location accuracy is easily affected by factors such as line model parameters, system operation, signal measurement, and transition resistance.

[0068] Because a transition resistance exists at the fault point, and it is usually approximately purely resistive, a unique and strict phase constraint relationship always exists between the zero-sequence voltage across the transition resistance and the zero-sequence current flowing through it. That is, the instantaneous phase must always be consistent. Based on the distribution law of zero-sequence voltage and current on the line, this constraint condition holds only at the fault point. Due to the instantaneous phase constraint condition, the transition resistance is the electrical connection between fault points that is not an ideal metallic short circuit when a fault occurs; it is a certain resistance. The phase of the zero-sequence voltage across the transition resistance and the zero-sequence current flowing through it must always remain equal. Therefore, by determining the phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point, it is possible to determine whether the virtual fault point is indeed a fault point.

[0069] Specifically, the calculation process requires determining the current and voltage at each point in the section based on the zero-sequence voltage at the beginning, the zero-sequence current at the beginning, and the zero-sequence current at the end. When calculating the current and voltage, the distance between the virtual fault points and the equivalent resistance between the virtual fault points also need to be considered.

[0070] This application provides a method and apparatus for locating fault points in power distribution lines, relating to the field of power distribution networks. The method includes constructing multiple virtual fault points and determining the zero-sequence current before the fault point and the zero-sequence voltage at the fault point based on the zero-sequence voltage, zero-sequence current at the beginning of the fault section, and zero-sequence current at the end of the fault section; determining the phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point; identifying virtual fault points with a phase difference less than a judgment threshold as actual fault points, and determining the fault distance between the fault point and the beginning of the fault section. Since the zero-sequence voltage and zero-sequence current of each virtual fault point have a phase constraint relationship, when the voltage phase and current phase are approximately the same, it is proven that this virtual fault point is the actual fault point. Therefore, multiple virtual fault points are constructed, and the phase difference between the zero-sequence voltage and zero-sequence current is calculated separately, eliminating the need for additional measuring equipment and simplifying the calculation results.

[0071] Based on the above embodiments:

[0072] In some embodiments, determining the zero-sequence voltage at the beginning of a fault section of a power distribution line, the zero-sequence current at the beginning of the fault section, and the zero-sequence current at the end of the fault section includes:

[0073] After acquiring the fault occurrence time, at least two acquisition cycles are required for the discrete beginning zero-sequence voltage, discrete beginning zero-sequence current, and discrete end zero-sequence current of the fault segment.

[0074] The zero-sequence voltage, zero-sequence current and zero-sequence current at the beginning and end of the fault section in two acquisition cycles are fitted to obtain the zero-sequence voltage, zero-sequence current and zero-sequence current at the beginning and end.

[0075] The expressions for the zero-sequence voltage at the beginning, the zero-sequence current at the beginning, and the zero-sequence current at the end are:

[0076] ;

[0077] in, Let M be the zero-sequence current at time t. Let M be the zero-sequence current at time t. instantaneous amplitude, , Let M be the zero-sequence current at time t. The instantaneous initial phase, , Let M be the zero-sequence current at time t. The magnitude of the cosine function term, Let M be the zero-sequence current at time t. The magnitude of the sine function term, Let be the zero-sequence voltage at terminal M at time t. Let M be the zero-sequence voltage at time t. instantaneous amplitude, Let M be the zero-sequence voltage at time t. The instantaneous initial phase, Let M be the zero-sequence voltage at time t. The magnitude of the cosine function term, Let M be the zero-sequence voltage at time t. The magnitude of the sine function term, Let be the zero-sequence current at terminal N at time t. Let N be the zero-sequence current at time t. instantaneous amplitude, Let N be the zero-sequence current at time t. The instantaneous initial phase, Let N be the zero-sequence current at time t. The magnitude of the cosine function term, Let N be the zero-sequence current at time t. The magnitude of the sine function term, Let N be the zero-sequence voltage at time t. Let N be the zero-sequence voltage at time t. instantaneous amplitude, Let N be the zero-sequence voltage at time t. The instantaneous initial phase, Let N be the zero-sequence voltage at time t. The magnitude of the cosine function term, Let N be the zero-sequence voltage at time t. The amplitude of the sin function term; the fault section is the section with M as the beginning and N as the end.

[0078] Based on the zero-sequence voltage, zero-sequence current at the beginning of the fault section, and zero-sequence current at the end of the fault section, determine the zero-sequence current before the fault point and the zero-sequence voltage at the fault point for each virtual fault point, including:

[0079] The zero-sequence voltage, zero-sequence current and zero-sequence current at the beginning and end of the continuous fault section are used to determine the zero-sequence current before the fault point and the zero-sequence voltage at the fault point of each virtual fault point.

[0080] The fault signal to be calculated is obtained by collecting N data points (at least one power frequency cycle) of zero-sequence voltage and current from the moment of fault occurrence using a waveform recorder. Since the model requires the (2q-p)-th order derivatives of the zero-sequence voltage and current during calculation, but the actual measured signals are discrete transient data, processing of the discrete transient data is necessary. This patent uses a sinusoidal representation method for transient signals proposed in existing literature to fit the discrete transient data to obtain a functional expression, which can then be differentiated at higher orders.

[0081] Figure 2 This invention provides a structural schematic diagram of a fault point. The zero-sequence voltage at the fault point; This refers to the zero-sequence current before the fault point. This refers to the zero-sequence current after the fault point. This is the fault zero-sequence current; It is a zero-sequence equivalent voltage source; This is the transition resistance at the fault point.

[0082] Figure 3 This is a schematic diagram of a virtual fault point provided by the present invention.

[0083] In some embodiments, multiple virtual fault points are constructed, and the zero-sequence current before the fault point and the zero-sequence voltage at the fault point are determined based on the zero-sequence voltage at the beginning of the fault section, the zero-sequence current at the beginning of the fault section, and the zero-sequence current at the end of the fault section, including:

[0084] Construct multiple virtual fault points, where the distance between any two adjacent virtual fault points is . And there is a transition resistance;

[0085] Based on the zero-sequence voltage and zero-sequence current at the beginning of the fault section, the virtual fault point inlet zero-sequence current and fault point zero-sequence voltage are determined for each virtual fault point. The expressions for the virtual fault point inlet zero-sequence current and fault point zero-sequence voltage are as follows:

[0086] ;

[0087] in, The zero-sequence voltage at the virtual fault point. Let be the zero-sequence voltage at terminal M at time t. Let M be the zero-sequence current at time t. Let be the derivative of the zero-sequence current at terminal M at time t. As the first transition function, The zero-sequence current before the virtual fault point. Let R be the second transition function, l be the resistance per unit length, l be the length of the line, and L be the inductance per unit length.

[0088] like Figure 3 As shown, due to the presence of transition resistance at the fault point... Furthermore, it is usually approximately purely resistive, therefore the zero-sequence voltage across the transition resistor is... With the zero-sequence current flowing through the transition resistor There will always be a unique and strict phase constraint relationship, that is and The instantaneous phase should always be consistent. According to the distribution law of zero-sequence voltage and current on the line, this constraint condition only holds true at the fault point.

[0089] Assuming the search step size is That is, the faulty sections are evenly distributed at intervals per unit distance. Virtual fault points, such as Figure 3 As shown, the main method involves calculating the phase of the transition resistance at each point by setting virtual fault points, and finally identifying the point with the smallest phase difference as the actual fault point.

[0090] Due to instantaneous phase constraints, the transition resistance is defined as the resistance present when the electrical connection between fault points is not an ideal metallic short circuit during a fault, and a certain resistance exists. The zero-sequence voltage across the transition resistance is... and the zero-sequence current flowing through the transition resistance The phases should always remain equal, that is, satisfy the relation. Therefore, its instantaneous initial phase remains constant at all times, that is... .

[0091] By using trigonometric identity transformations, the instantaneous initial phase of the fault is transformed into:

[0092] .

[0093] The initial phase constraint condition for the fault can also be equivalent to:

[0094] .

[0095] Based on the above principles, substitute the distributed parameter line model to calculate the virtual fault point.

[0096] In some embodiments, the expression for the first transition function is:

[0097] ;

[0098] in, The length of the line is a power of 2q. To select p elements from q distinct elements, , The resistance per unit length is raised to the power of p. The value is the qp power of the inductance per unit length. Let j be the power of the capacitance per unit length. Let be the 2q-p derivative of the zero-sequence voltage at terminal M at time t. The conductance per unit length is raised to the power of q. Let be the 2q-p-1th order derivative of the zero-sequence voltage at terminal M at time t. The length of the line is a power of 2q+1. To select p elements from q+1 distinct elements, The value is the inductance per unit length raised to the power of q-p+1. It is the q-th power of the capacitance per unit length. Let be the 2q-p+1th derivative of the zero-sequence current at terminal M at time t. Let be the 2q-p derivative of the zero-sequence current at terminal M at time t;

[0099] The expression for the second transition function is:

[0100] ;

[0101] in, The length of the line is a power of 2q-1. To select p elements from q-1 distinct elements, The value is the qp⁻¹ power of the inductance per unit length. Let be the 2q-p-2nd order derivative of the zero-sequence voltage at terminal M at time t. The length of the line is a power of 2q. Let be the 2q-p derivative of the zero-sequence current at terminal M at time t. Let be the 2q-p-1 derivative of the zero-sequence current at terminal M at time t.

[0102] In some embodiments, before determining the phase difference between the zero-sequence current and the zero-sequence voltage before the virtual fault point, the method further includes:

[0103] Determine the instantaneous amplitude of the zero-sequence voltage, the instantaneous amplitude of the zero-sequence current, and the instantaneous phase of the zero-sequence voltage and the instantaneous phase of the zero-sequence current of the transition resistance between each virtual fault point;

[0104] The expressions for the instantaneous amplitude and phase of the zero-sequence voltage of the transition resistor are as follows:

[0105] ;

[0106] in, The instantaneous amplitude of the zero-sequence voltage of the transition resistor. The first steady-state constant of the zero-sequence voltage of the transition resistance is... It is an exponential function of the decay of the zero-sequence voltage. The second steady-state constant of the zero-sequence voltage of the transition resistance is... The Hilbert transform corresponds to the exponential function of the decay of the zero-sequence voltage. The instantaneous phase of the zero-sequence voltage of the transition resistor;

[0107] The expressions for the instantaneous amplitude and instantaneous phase of the zero-sequence current of the transition resistor are as follows:

[0108] ;

[0109] in, The instantaneous amplitude of the zero-sequence current of the transition resistor. The first steady-state constant of the zero-sequence current of the transition resistance is... It is an exponential function of the decay of the zero-sequence current. The second steady-state constant of the zero-sequence current of the transition resistance is... The Hilbert transform corresponds to the exponential function of the decay of the zero-sequence current. The instantaneous phase of the zero-sequence current of the transition resistor.

[0110] Continuing with the distributed parameter circuit model, based on the idea of ​​cascading micro-circuits in the distributed parameter circuit model, we know that the current in the upper-order micro-circuit can be represented by the current and voltage flowing into the lower-order micro-circuit. This can be extended to the cascading of all micro-circuits in the entire downstream section of the fault point. Assuming the downstream section of the fault point consists of… A series of cascaded micro-element circuits are used to calculate the voltage of each micro-element on the line downstream of the fault point and its corresponding arbitrary derivative for a virtual point. The first derivative of the zero-sequence current after the fault point through the terminal current and the voltage of each micro-element is expressed as follows:

[0111] .

[0112] Zero-sequence capacitance per unit length of line, voltage With the zero-sequence current flowing through the transition resistor It can be represented as:

[0113] In the formula The zero-sequence voltage at the fault point; For the point of inflow to the fault The zero-sequence current; This refers to the zero-sequence current before the fault point. This refers to the zero-sequence current after the fault point. It is a zero-sequence equivalent voltage source. Fault point The zero-sequence voltage across the terminals. Using trigonometric function calculation rules, the above equation can be expressed as a sinusoidal function whose amplitude and initial phase vary with time, i.e.:

[0114] .

[0115] in, , , , The steady-state constants of the zero-sequence voltage and current of the transition resistance; , It is a decaying exponential function; , This is the Hilbert transform corresponding to the decay exponential function. Calculate the instantaneous amplitude of the zero-sequence voltage across the transition resistance. Instantaneous amplitude of zero-sequence current and the instantaneous phase of the zero-sequence voltage of the transition resistance Zero-sequence current instantaneous phase .

[0116] In some embodiments, determining the phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point includes:

[0117] The phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point is determined. The expression for the phase difference is:

[0118] ;

[0119] in, The phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point.

[0120] Because a transition resistance exists at the fault point and is usually approximately purely resistive, the zero-sequence voltage across the transition resistance and the zero-sequence current flowing through the transition resistance are... There will always be a unique and strict phase constraint relationship, meaning the instantaneous phase should always remain consistent. Based on the distribution law of zero-sequence voltage and current on the line, this constraint condition only holds at the fault point. Determining the initial phase constraint condition. Calculate the instantaneous phase difference of the transition resistance voltage and current at the virtual fault point. .

[0121] In some embodiments, before identifying virtual fault points with phase differences less than a judgment threshold as fault points and determining the fault distance between the fault point and the beginning of the fault section, the method further includes:

[0122] Construct a virtual fault point search matrix. The expression for the search matrix is:

[0123] ;

[0124] in, For phase difference, The distance between any two adjacent virtual fault points. Let n be the number of virtual fault points at the z-th sampling time. For N times at The sum of the instantaneous phase differences of the transition resistance voltage and current along the line length.

[0125] Then, the actual fault point is determined based on the fault point search matrix.

[0126] In some embodiments, virtual fault points with phase differences less than a judgment threshold are identified as fault points, and the fault distance between the fault point and the beginning of the fault section is determined, including:

[0127] Obtain the phase difference of the first virtual fault point from the search matrix;

[0128] Determine if the phase difference of the first virtual fault point meets the requirements. , To determine the threshold;

[0129] If satisfied, output the fault distance. .

[0130] In some embodiments, it is determined whether the phase difference of the first virtual fault point satisfies the condition. Following that, it also includes:

[0131] If not satisfied, then sequentially obtain the phase difference of the remaining virtual fault points and determine whether they are satisfied. ;

[0132] If satisfied, output the fault distance. .

[0133] Search for the first virtual fault point , in the form To determine the conditions, This indicates the allowable error tolerance of the model. If the tolerance is met, the fault distance is output; otherwise, proceed to the next step.

[0134] Determine the next virtual fault point ,calculate And so on. When the judgment condition is met, the point is selected as the fault point, and the distance corresponding to its matrix element is... This is the distance from the fault at the beginning.

[0135] Output the distance to the fault point.

[0136] Figure 4 This is a schematic diagram of a fault location device for power distribution lines provided by the present invention. The fault location device for power distribution lines includes:

[0137] Memory 41 is used to store computer programs;

[0138] The processor 42 is used to implement the steps of the above-described method for locating fault points in power distribution lines when executing a computer program.

[0139] Please refer to the above embodiments for a description of the fault location device for power distribution lines provided in this application, and it will not be repeated here.

[0140] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0141] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0142] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for locating fault points in power distribution lines, characterized in that, include: Determine the zero-sequence voltage, zero-sequence current and zero-sequence current at the beginning and end of the fault section of the power distribution line, where a fault point exists in the fault section; Multiple virtual fault points are constructed, and the zero-sequence current before the fault point and the zero-sequence voltage at the beginning of the fault section, the zero-sequence current at the beginning of the fault section and the zero-sequence current at the end of the fault section are determined. Determine the phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point; Virtual fault points with phase differences less than the judgment threshold are taken as fault points, and the fault distance between the fault point and the beginning of the fault section is determined.

2. The method for locating fault points in power distribution lines as described in claim 1, characterized in that, Determine the zero-sequence voltage, zero-sequence current at the beginning of the fault section of the power distribution line, and zero-sequence current at the end of the fault section, including: After acquiring the fault occurrence time, at least two acquisition cycles are required for the discrete beginning zero-sequence voltage, discrete beginning zero-sequence current, and discrete end zero-sequence current of the fault segment. The zero-sequence voltage, zero-sequence current and zero-sequence current at the beginning and end of the fault section in the two acquisition cycles are fitted to obtain the zero-sequence voltage, zero-sequence current and zero-sequence current at the beginning and end. The expressions for the zero-sequence voltage at the beginning, the zero-sequence current at the beginning, and the zero-sequence current at the end are as follows: ； in, Let M be the zero-sequence current at time t. Let M be the zero-sequence current at time t. instantaneous amplitude, , Let M be the zero-sequence current at time t. The instantaneous initial phase, , Let M be the zero-sequence current at time t. The magnitude of the cosine function term, Let M be the zero-sequence current at time t. The magnitude of the sine function term, Let be the zero-sequence voltage at terminal M at time t. Let M be the zero-sequence voltage at time t. instantaneous amplitude, Let M be the zero-sequence voltage at time t. The instantaneous initial phase, Let M be the zero-sequence voltage at time t. The magnitude of the cosine function term, Let M be the zero-sequence voltage at time t. The magnitude of the sine function term, Let be the zero-sequence current at terminal N at time t. Let N be the zero-sequence current at time t. The instantaneous amplitude, Let N be the zero-sequence current at time t. The instantaneous initial phase, Let N be the zero-sequence current at time t. The magnitude of the cosine function term, Let N be the zero-sequence current at time t. The magnitude of the sine function term, Let N be the zero-sequence voltage at time t. Let N be the zero-sequence voltage at time t. The instantaneous amplitude, Let N be the zero-sequence voltage at time t. The instantaneous initial phase, Let N be the zero-sequence voltage at time t. The magnitude of the cosine function term, Let N be the zero-sequence voltage at time t. The magnitude of the sin function term, wherein the fault segment is the segment with M as the beginning and N as the end; Based on the zero-sequence voltage at the beginning of the fault section, the zero-sequence current at the beginning of the fault section, and the zero-sequence current at the end of the fault section, the zero-sequence current before the fault point and the zero-sequence voltage at the fault point are determined, including: Based on the zero-sequence voltage, zero-sequence current and zero-sequence current at the beginning and end of the continuous fault sections, the zero-sequence current before the fault point and the zero-sequence voltage at the fault point of each virtual fault point are determined.

3. The method for locating fault points in power distribution lines as described in claim 1, characterized in that, Multiple virtual fault points are constructed, and the zero-sequence current before the fault point and the zero-sequence voltage at the beginning of the fault section, the zero-sequence current at the beginning of the fault section, and the zero-sequence current at the end of the fault section are determined, including: Multiple virtual fault points are constructed, wherein the distance between any two adjacent virtual fault points is . And there is a transition resistance; Based on the zero-sequence voltage and zero-sequence current at the beginning of the fault section, the virtual fault point inlet zero-sequence current and fault point zero-sequence voltage are determined for each virtual fault point. The expressions for the virtual fault point inlet zero-sequence current and fault point zero-sequence voltage are as follows: ； in, The zero-sequence voltage at the virtual fault point. Let be the zero-sequence voltage at terminal M at time t. Let M be the zero-sequence current at time t. Let be the derivative of the zero-sequence current at terminal M at time t. As the first transition function, The zero-sequence current before the virtual fault point. Let R be the second transition function, l be the resistance per unit length, l be the length of the line, and L be the inductance per unit length.

4. The method for locating fault points in power distribution lines as described in claim 3, characterized in that, The expression for the first transition function is: ； in, The length of the line is a power of 2q. To select p elements from q distinct elements, , The resistance per unit length is raised to the power of p. The value is the qp power of the inductance per unit length. Let j be the power of the capacitance per unit length. Let be the 2q-p derivative of the zero-sequence voltage at terminal M at time t. The conductance per unit length is raised to the power of q. Let be the 2q-p-1th order derivative of the zero-sequence voltage at terminal M at time t. The length of the line is a power of 2q+1. To select p elements from q+1 distinct elements, The value is the inductance per unit length raised to the power of q-p+1. It is the q-th power of the capacitance per unit length. Let be the 2q-p+1th derivative of the zero-sequence current at terminal M at time t. Let be the 2q-p derivative of the zero-sequence current at terminal M at time t; The expression for the second transition function is: ； in, The length of the line is a power of 2q-1. To select p elements from q-1 distinct elements, The value is the qp⁻¹ power of the inductance per unit length. Let be the 2q-p-2nd order derivative of the zero-sequence voltage at terminal M at time t. The length of the line is a power of 2q. Let be the 2q-p derivative of the zero-sequence current at terminal M at time t. Let be the 2q-p-1 derivative of the zero-sequence current at terminal M at time t.

5. The method for locating fault points in power distribution lines as described in claim 1, characterized in that, Before determining the phase difference between the zero-sequence current and the zero-sequence voltage at the virtual fault point, the method further includes: Determine the instantaneous amplitude of the zero-sequence voltage, the instantaneous amplitude of the zero-sequence current, and the instantaneous phase of the zero-sequence voltage and the instantaneous phase of the zero-sequence current of the transition resistance between each virtual fault point; The expressions for the instantaneous amplitude of the zero-sequence voltage of the transition resistor and the instantaneous phase of the zero-sequence voltage of the transition resistor are as follows: ； in, The instantaneous amplitude of the zero-sequence voltage of the transition resistor is given. The first steady-state constant of the zero-sequence voltage of the transition resistance is... It is an exponential function of the decay of the zero-sequence voltage. The second steady-state constant of the zero-sequence voltage of the transition resistance is... The Hilbert transform corresponds to the exponential function of the decay of the zero-sequence voltage. The zero-sequence voltage instantaneous phase of the transition resistor; The expressions for the instantaneous amplitude of the zero-sequence current of the transition resistor and the instantaneous phase of the zero-sequence current of the transition resistor are as follows: ； in, The instantaneous amplitude of the zero-sequence current of the transition resistor is given. The first steady-state constant of the zero-sequence current of the transition resistance is... It is an exponential function of the decay of the zero-sequence current. The second steady-state constant of the zero-sequence current of the transition resistance is... The Hilbert transform corresponds to the exponential function of the decay of the zero-sequence current. The zero-sequence current instantaneous phase of the transition resistor.

6. The method for locating fault points in power distribution lines as described in claim 5, characterized in that, Determining the phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point includes: The phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage at the virtual fault point is determined, and the expression for the phase difference is: ； in, The phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage of the virtual fault point.

7. The method for locating fault points in power distribution lines as described in any one of claims 1 to 6, characterized in that, Before determining the virtual fault point whose phase difference is less than the judgment threshold as the fault point, and before determining the fault distance between the fault point and the beginning of the fault section, the method further includes: Construct a virtual fault point search matrix, the expression of which is: ； in, For phase difference, The distance between any two adjacent virtual fault points is denoted as . Let n be the number of virtual fault points at the z-th sampling time. For N times at The sum of the instantaneous phase differences of the transition resistance voltage and current along the line length.

8. The method for locating fault points in power distribution lines as described in claim 7, characterized in that, Virtual fault points with phase differences less than a judgment threshold are designated as fault points, and the fault distance between the fault point and the beginning of the fault section is determined, including: Obtain the phase difference of the first virtual fault point from the search matrix; Determine if the phase difference of the first virtual fault point meets the requirements. , The threshold value is the threshold value used for judgment. If satisfied, output the fault distance. .

9. The method for locating fault points in power distribution lines as described in claim 8, characterized in that, Determine if the phase difference of the first virtual fault point meets the requirements. Following that, it also includes: If not satisfied, then sequentially obtain the phase difference of the remaining virtual fault points and determine whether they are satisfied. ; If satisfied, output the fault distance. .

10. A device for locating fault points in power distribution lines, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the method for locating fault points in a power distribution line as described in any one of claims 1 to 9.

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