Distribution network differential protection method based on current amplitude and phase characteristics and distance algorithm

Abstract

The invention discloses a distribution network differential protection method based on current amplitude-phase characteristics and a distance algorithm, and relates to the technical field of distribution network differential protection, comprising: obtaining real-time power parameters at both ends of a protection installation in a target detection distribution network area, extracting current phasors and calculating a first signal amplitude characteristic ratio and a phase angle difference at both ends of the protection installation to calculate a first differential protection coefficient, and calculating the Hausdorff distance at both ends based on a Hausdorff distance algorithm, thereby obtaining a second differential protection coefficient; judging the fault state twice according to the first differential protection coefficient and the Hausdorff distance, calculating a reliability improvement coefficient and a safety improvement coefficient, and comprehensively analyzing the fault type of the fault distribution network in combination with the current phasors; the method overcomes the problem that traditional current differential protection lacks comprehensive data analysis of multi-terminal quantities, resulting in unreliable fault judgment and poor protection performance, significantly improves the distribution network differential protection performance and fault judgment efficiency, and improves the reliability of the distribution network differential protection.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network differential protection, and in particular to a distribution network differential protection method based on current amplitude-phase characteristics and a distance algorithm. Background Art

[0002] With the widespread access of distributed energy, the distribution network has gradually transformed into a multi-terminal active network. The topology and fault characteristics of the distribution network are becoming increasingly complex. Distributed power sources based on inverter interfaces such as photovoltaic, wind power and energy storage show fault characteristics of limited amplitude and controlled phase angle, which further aggravates the complexity of the distribution network fault current. The conventional distribution network current differential protection technology mainly judges the line operation status and fault section based on the characteristics of the numerical range of the current amplitude ratio on both sides of the line under different working conditions. However, facing the characteristics of multi-source, multi-load branches, and bidirectional power flow in the distribution network, the technology of fault analysis based on a single current characteristic is difficult to ensure the accuracy of the distribution network fault state judgment and the reliability of the fault judgment criterion, resulting in poor performance of the current differential protection, or even failure to operate correctly, causing major power outages and other accidents, affecting the safe and stable operation of the power grid. In addition, the conventional distribution network current differential protection technology is limited by the calculation flow of the current amplitude on both sides, and can no longer calculate the comprehensive amplitude and performance coefficient. Due to the complex distribution network results and load status, the fault judgment criterion cannot be accurately described. Summary of the invention

[0003] The purpose of the present invention is to solve the problem that the traditional current differential protection lacks comprehensive data analysis of multi-terminal quantities, resulting in poor reliability of protection judgment criteria and thus poor differential protection performance; a distribution network differential protection method based on current amplitude-phase characteristics and distance algorithm is proposed, by obtaining the signal amplitude characteristic ratio and phase angle difference at both ends of the protection installation, a first differential protection coefficient is calculated, and the Hausdorff distance at both ends is calculated based on the Hausdorff distance algorithm, thereby obtaining the second differential protection coefficient; the fault state is judged twice according to the first differential protection coefficient and the Hausdorff distance, and the reliability improvement coefficient and the safety improvement coefficient are calculated, and the fault type of the fault distribution network is comprehensively analyzed in combination with the current phase quantity; the problem that the traditional current differential protection lacks comprehensive data analysis of multi-terminal quantities, resulting in unreliable fault judgment and poor protection performance is overcome, the distribution network differential protection performance and fault judgment efficiency are significantly improved, and the reliability of the distribution network differential protection is improved.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a distribution network differential protection method based on current amplitude and phase characteristics and a distance algorithm, comprising the following steps:

[0005] S1. Acquire real-time power parameters at both ends of the protection installation in the target detection distribution network area, extract the current phasor and calculate the first signal amplitude characteristic ratio and phase angle difference at both ends of the protection installation;

[0006] S2. Calculating a first differential protection coefficient based on the first signal amplitude characteristic ratio and the phase angle difference;

[0007] S3, using the real-time power parameter as an input parameter of a Hausdorff distance algorithm, and calculating the Hausdorff distance at both ends of the protection installation and a second differential protection coefficient;

[0008] S4, secondarily judging whether a fault occurs in the target detection distribution network area according to the first differential protection coefficient and the Hausdorff distance, if so, executing S5; if not, executing S1;

[0009] S5. Calculating a reliability improvement coefficient based on the first differential protection coefficient, and calculating a safety improvement coefficient based on the second differential protection coefficient;

[0010] S6. Comprehensively determine the fault type based on the reliability improvement factor, the safety improvement factor and the current phasor, and perform corresponding protection actions according to the fault type.

[0011] In this scheme, by calculating the signal amplitude characteristic ratio and phase angle difference at both ends of the line, and then calculating the first differential protection coefficient, it is possible to preliminarily detect whether there is a fault in the line according to the first differential protection coefficient, and reflect the change of the fault state through the change characteristics of the signal amplitude and phase angle, which is helpful to distinguish the fault type, realize targeted fault processing, and make corresponding protection action decisions; by calculating the Hausdorff distance, the current phasors at both ends can be compared, so as to identify the offset and deformation of the line, and further calculate the safety improvement factor and reliability improvement factor of the distribution network according to the Hausdorff distance to realize rapid and accurate judgment of the type of fault occurring in the line and fault location; by calculating the Hausdorff distance and combining the safety improvement factor and the reliability improvement factor to evaluate the distribution network in multiple dimensions, the fault judgment criteria are made more comprehensive, reliable and accurate, and the differential protection system's perception of the line state is significantly enhanced, and the difference between normal operation and fault conditions is comprehensively, efficiently and reliably distinguished, thereby reducing misjudgment. Among them, the safety improvement factor and the reliability improvement factor can more carefully reflect the impact of faults on the distribution network, more effectively identify non-fault conditions, prevent protection misoperation and thus improve the reliability of protection; at the same time, the introduction of a comprehensive judgment criterion for the safety improvement factor and the reliability improvement factor provides a basis for formulating more effective protection measures, so that the protection measures can be flexibly adjusted according to different situations, thereby improving the adaptability and flexibility of the protection, and solving the problem that traditional current differential protection lacks comprehensive data analysis of multi-terminal quantities, resulting in unreliable fault judgment and poor protection performance, significantly improving the protection performance as well as the accuracy and reliability of the protection, and further ensuring the safe and stable operation of the distribution network.

[0012] Preferably, S1 comprises the following sub-steps:

[0013] S11, collecting real-time power parameters at both ends of the protection installation in the target detection distribution network area based on a discrete sampling method, and obtaining discrete sequence point sets at both ends of the protection installation, including a first discrete sequence point set and a second discrete sequence point set;

[0014] S12, performing data transformation on the first discrete sequence point set and the second discrete sequence point set based on discrete Fourier transform to obtain a first current phasor of the first discrete sequence point set and a second current phasor of the second discrete sequence point set;

[0015] S13, calculating a first signal amplitude characteristic ratio according to the amplitudes of the first current phasor and the second current phasor;

[0016] S14. Calculate the phase angle difference based on the argument of the first current phasor and the second current phasor.

[0017] Preferably, S2 comprises the following sub-steps:

[0018] The first differential protection coefficient is obtained by summing the sinusoidal angle compensation of the phase angle difference and the first signal amplitude characteristic ratio.

[0019] Preferably, S3 includes the following sub-steps:

[0020] S31, calculating the Hausdorff one-way distance between the first discrete sequence point set and the second discrete sequence point set based on the opposite number of the first current phasor and the second current phasor;

[0021] S32, calculating the Hausdorff distance between the first discrete sequence point set and the second discrete sequence point set based on the Hausdorff one-way distance, and merging the Hausdorff distances to obtain a data window point set;

[0022] S33. Extracting the sample ratio of the Hausdorff distance based on the data window point set, and calculating the second differential protection coefficient.

[0023] Preferably, the S31 includes:

[0024] Based on the opposite number of the first current phasor and the second current phasor, calculate a first Hausdorff one-way distance from the first discrete sequence point set to the second discrete sequence point set, and a second Hausdorff one-way distance from the second discrete sequence point set to the first discrete sequence point set;

[0025] The calculation formula of the first Hausdorff one-way distance is as follows:

[0026] ;

[0027] The calculation formula of the second Hausdorff one-way distance is as follows:

[0028] ;

[0029] In the formula, represents the Euclidean distance between the sampling points at both ends of the protection installation, is the first Hausdorff one-way distance, is the second Hausdorff one-way distance, represents the current phasor of the sampling point from the i-th sampling point in the first discrete sequence point set to the j-th sampling point in the second discrete sequence point set, represents the current phasor of the jth sampling point in the second discrete sequence point set that is closest to the ith sampling point in the first discrete sequence point set, represents the first discrete sequence point set, Represents the second discrete sequence point set.

[0030] Preferably, the S33 includes the following sub-steps:

[0031] According to the data window point set, the sample ratio information of the Hausdorff distance under the distribution network line fault state is obtained, and the second differential protection coefficient is calculated;

[0032] The calculation formula of the second differential protection coefficient is as follows:

[0033] ;

[0034] In the formula, is the second differential protection coefficient, i represents the number of current sampling points, It represents the number of sampling points in the data window point set 10ms after the fault is detected. total in 10 ms Indicates that the time to record the number of sampling points after a fault is detected is 10 milliseconds. It indicates the number of samples in the data window point set for which the Hausdorff distance does not approach 0.

[0035] Preferably, S4 includes the following sub-steps:

[0036] S41, performing a fault judgment on the target detection distribution network area based on the first differential protection coefficient. If the first differential protection coefficient is less than a critical threshold, the target detection distribution network area operates normally; if the first differential protection coefficient is greater than or equal to the critical threshold, executing S42;

[0037] S42, performing secondary fault judgment on the target detection distribution network area based on the Hausdorff distance. If the Hausdorff distance exceeds the safe distance range, the target detection distribution network area has a fault, and S5 is executed; if the Hausdorff distance is within the safe distance range, the target detection distribution network area has no fault, and S1 is executed.

[0038] In this scheme, by comparing the first differential protection coefficient with the critical threshold, the obvious difference between the current amplitude characteristic and the fault state can be used to quickly determine whether a fault has occurred. Among them, the first signal amplitude characteristic ratio increases, the phase angle difference decreases, and the sine angle compensation value of the phase angle difference increases, which indicates that a fault has occurred in the characterization area. When the first differential protection coefficient is greater than or equal to the critical threshold, the larger the first differential protection coefficient, the more serious the fault. Therefore, calculating the first differential protection coefficient for initial fault detection improves the efficiency and reliability of distribution network differential protection.

[0039] Preferably, in S5, calculating the reliability improvement coefficient based on the first differential protection coefficient includes the following sub-steps:

[0040] The first differential protection coefficient is calculated based on a hyperbolic function to obtain a first reliability improvement coefficient and a second reliability improvement coefficient. The calculation formula is as follows:

[0041] ;

[0042] In the formula, is the first reliability improvement coefficient, is the second reliability improvement coefficient, is the first differential protection coefficient, and e represents the base of the natural logarithm of the hyperbolic function.

[0043] Preferably, in S5, calculating the safety improvement coefficient based on the second differential protection coefficient includes: the following calculation formula:

[0044] The second differential protection coefficient is used as a calculation parameter based on the hyperbolic tangent function to calculate the safety improvement coefficient. The calculation formula is as follows:

[0045] ;

[0046] In the formula, represents the safety improvement coefficient, e represents the base of the natural logarithm of the hyperbolic function, represents the second differential protection coefficient.

[0047] Preferably, the S6 comprises the following sub-steps:

[0048] Presetting a protection criterion for the target detection distribution network area based on the first reliability improvement coefficient, the second reliability improvement coefficient, the safety improvement coefficient and the first current phasor and the second current phasor;

[0049] Determine whether the fault in the target detection distribution network area is an internal fault according to the protection criterion, and if so, send a trip signal to the circuit breaker; if not, do not send a trip signal to the circuit breaker;

[0050] The protection criteria are expressed as follows:

[0051] ;

[0052] In the formula, K represents the switch action safety factor, is the first current phasor, is the second current phasor, represents the safety improvement factor, is the first reliability improvement coefficient, is the second reliability improvement coefficient.

[0053] In this scheme, the first reliability improvement coefficient, the second reliability improvement coefficient, and the safety improvement coefficient are combined with the comprehensive analysis of the current phasor and the formulation of protection criteria to improve the judgment criteria of the single-ended quantity. Calculating the reliability improvement coefficient and the safety improvement coefficient separately can effectively ensure that the protection does not refuse to operate in the event of a fault within the zone and does not malfunction in the event of a fault outside the zone, improve the sensitivity of the differential protection in the event of a fault within the zone, avoid protection refusal to operate, and at the same time cannot reduce the safety of the protection.

[0054] Beneficial effects of the present invention:

[0055] 1. By introducing the amplitude, phase relationship and Hausdorff distance of the current on both sides of the protection installation into the distribution network fault judgment criteria, a comprehensive and integrated analysis of the distribution network fault is achieved, which improves the sensitivity and reliability of the current differential protection;

[0056] 2. By combining the reliability improvement factor and the safety improvement factor with the comprehensive analysis of the current phasor and formulating the protection criterion, the improvement of the single-end quantity and the single double-end phasor criterion is achieved, which can more quickly and accurately identify the fault type and fault phase, prevent the protection from false operation, and ensure that the distribution network is not affected by the saturation of the current transformer, thereby improving the reliability of the protection, improving the adaptability and flexibility of the protection, and ensuring the safe and stable operation of the active distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings. The drawings are only for the purpose of illustrating preferred embodiments and are not to be considered as limiting the present invention. Also, the same reference symbols are used throughout the drawings to represent the same parts.

[0058] Figure 1 This is a flow chart of a distribution network differential protection method based on current amplitude and phase characteristics and distance algorithm in this embodiment.

[0059] Figure 2 The diagram is a schematic diagram of current collection topology at both ends of a protection installation in this embodiment.

[0060] Figure 3 This is a flow chart of a distribution network differential protection method based on current amplitude-phase characteristics and Hausdorff distance in this embodiment. DETAILED DESCRIPTION

[0061] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation method described herein is only an optimal embodiment of the present invention, which is only used to explain the present invention and does not limit the scope of protection of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0062] Example 1: Figure 1 As shown, the distribution network differential protection method based on current amplitude and phase characteristics and distance algorithm includes steps S1-S6, wherein:

[0063] S1. Acquire real-time power parameters at both ends of the protection installation in the target detection distribution network area, extract the current phasor and calculate the first signal amplitude characteristic ratio and phase angle difference at both ends of the protection installation.

[0064] Specifically, Figure 2 and Figure 3 As shown, S1 includes the following sub-steps:

[0065] S11, collecting real-time power parameters at both ends of the protection installation in the target detection distribution network area based on a discrete sampling method, and obtaining discrete sequence point sets at both ends of the protection installation, including a first discrete sequence point set and a second discrete sequence point set;

[0066] S12, performing data transformation on the first discrete sequence point set and the second discrete sequence point set based on discrete Fourier transform to obtain a first current phasor of the first discrete sequence point set and a second current phasor of the second discrete sequence point set;

[0067] S13, calculating a first signal amplitude characteristic ratio according to the amplitudes of the first current phasor and the second current phasor;

[0068] S14. Calculate the phase angle difference based on the argument of the first current phasor and the second current phasor.

[0069] As an implementation method, the first current phasor on the grid side of the protection installation and the second current phasor on the power supply side of the protection installation are respectively collected to calculate the first signal amplitude characteristic ratio; wherein the calculation formula of the first signal amplitude characteristic ratio is as follows:

[0070] (1)

[0071] In the formula, is the first signal amplitude characteristic ratio, is the first current phasor, is the second current phasor, the first current phasor is the grid side, and the second current phasor is the distributed power supply side. Indicates the magnitude of the current phasor;

[0072] The calculation formula for the phase angle difference is as follows:

[0073] (2)

[0074] In the formula, is the phase angle difference, Represents the argument of the phasor.

[0075] S2. Calculate a first differential protection coefficient based on the first signal amplitude characteristic ratio and the phase angle difference.

[0076] Specifically, S2 includes the following sub-steps:

[0077] Summing the sinusoidal angle compensation of the phase angle difference and the first signal amplitude characteristic ratio to obtain the first differential protection coefficient;

[0078] The calculation formula of the first differential protection coefficient is as follows:

[0079] (3)

[0080] In the formula, is the first differential protection coefficient, is the sinusoidal angle compensation value of the phase angle difference.

[0081] In this embodiment, when the power system is operating normally or an out-of-zone fault occurs, the current phasors on both sides have equal amplitudes and opposite directions. is equal to 1, is equal to 180°, Equal to 0; when a fault occurs in the area, the current amplitude on both sides is Increase, phase difference Reduce, The value of increases, Greater than 1, and the more serious the fault The larger the value is; when an out-of-zone fault occurs, Equal to 0, thus, the distribution network fault can be quickly analyzed and judged to avoid the occurrence of misjudgment of the fault and ensure the accuracy and reliability of the judgment result.

[0082] S3. Using the real-time power parameters as input parameters of the Hausdorff distance algorithm, the Hausdorff distance at both ends of the protection installation and the second differential protection coefficient are calculated.

[0083] Specifically, S3 includes the following sub-steps:

[0084] S31, calculating the Hausdorff one-way distance between the first discrete sequence point set and the second discrete sequence point set based on the opposite number of the first current phasor and the second current phasor;

[0085] S32, calculating the Hausdorff distance between the first discrete sequence point set and the second discrete sequence point set based on the Hausdorff one-way distance, and merging the Hausdorff distances to obtain a data window point set;

[0086] S33. Extract the sample ratio of Hausdorff distance based on the data window point set, and calculate the second differential protection coefficient.

[0087] Specifically, S31 includes:

[0088] Based on the opposite number of the first current phasor and the second current phasor, a first Hausdorff one-way distance from the first discrete sequence point set to the second discrete sequence point set and a second Hausdorff one-way distance from the second discrete sequence point set to the first discrete sequence point set are calculated;

[0089] The calculation formula of the first Hausdorff one-way distance is as follows:

[0090] (4)

[0091] The calculation formula of the second Hausdorff one-way distance is as follows:

[0092] (5)

[0093] In the formula, It represents the Euclidean distance between the sampling points at both ends of the protection installation. is the first Hausdorff one-way distance, is the second Hausdorff one-way distance, represents the current phasor of the sampling point from the i-th sampling point in the first discrete sequence point set to the j-th sampling point in the second discrete sequence point set, represents the current phasor of the jth sampling point in the second discrete sequence point set that is closest to the ith sampling point in the first discrete sequence point set, represents the first discrete sequence point set, Represents the second discrete sequence point set.

[0094] As an implementation method, a hyperbolic function is used to calculate the distance between each point i in the first discrete sequence point set and the point j in the second discrete sequence point set closest to the point i. Sort them and take the maximum value of the distance as Similarly, for each point j in the second discrete sequence point set, the distance from the point i in the first discrete sequence point set closest to this point j is Sort them and take the maximum value of the distance as The value of is then calculated based on the zero-sequence current wavelet approximation sequence deviation matrix between the detection nodes, and the fault section is determined by comparing the deviation degree.

[0095] Specifically, the calculation formula of Hausdorff distance is as follows:

[0096] (6)

[0097] In the formula, represents the Hausdorff distance.

[0098] Specifically, take the first discrete sequence point set of the opposite number of the current sampling value And the second discrete sequence point set of the current direct sampling value The representation of is as follows:

[0099] (7)

[0100] (8).

[0101] Specifically, S33 includes the following sub-steps:

[0102] According to the data window point set, the sample proportion information of the Hausdorff distance under the fault state of the distribution network line is obtained, and the second differential protection coefficient is calculated;

[0103] The calculation formula of the second differential protection coefficient is as follows:

[0104] (9)

[0105] In the formula, is the second differential protection coefficient, i represents the number of current sampling points, Indicates the number of sampling points in the 10ms data window after the fault is detected. total in 10 ms Indicates that the time to record the number of sampling points after a fault is detected is 10 milliseconds. It indicates the number of samples whose Hausdorff distance in the data window point set does not approach 0.

[0106] As an implementation method, a short data window containing three points is selected from the set of the first Hausdorff one-way distance and the set of the second Hausdorff one-way distance to calculate the Hausdorff distance. The point set HD (data window point set) formed by the Hausdorff distance calculated in the short data window is expressed as follows:

[0107] (10)

[0108] Second differential protection factor It is expressed as:

[0109] (11)

[0110] In the formula, and They represent any three current sampling points between the two ends of the line for calculating the Hausdorff distance. is the judgment threshold of whether the sample is close to 0, Indicates the first The Hausdorff distance value of each sampling point;

[0111] When an out-of-zone fault occurs, even if the current sensor is severely saturated, there is at least 1 / 4 of the power frequency cycle in the linear transmission zone, for example, 5ms. At this time, the Hausdorff distance begins to increase after 5ms. Since the line voltage level in the distribution network is low and the length is short, the capacitive current is usually small. Therefore, it can be considered that the Hausdorff distance in the linear transmission zone of normal operation, out-of-zone faults and CT saturation is close to 0. The line fault is secondary judged based on the Hausdorff distance to enhance the accuracy of the judgment result; the second differential protection coefficient is calculated based on the proportion of samples that are not close to 0 in the data window point concentration within 10ms after the fault is detected. .

[0112] It can be understood that the Hausdorff distance can be used to identify differences between current waveforms. When a line fault occurs, such as a short circuit or a ground fault, the current waveform near the fault point will be significantly different from other points that are operating normally. By calculating the Hausdorff distance, this difference can be detected, thereby indicating the possible fault location. At the same time, by comparing the current waveforms at different locations through the Hausdorff distance, it can be determined which locations have waveforms that are least similar to other locations, which can assist in accurately locating the fault point and effectively locate the fault even in complex power networks. By continuously calculating and comparing the distances between waveforms, the protection system can respond to and handle fault events more quickly, thereby improving the reliability and stability of the distribution network.

[0113] S4. Secondarily determine whether a fault occurs in the target detection distribution network area according to the first differential protection coefficient and the Hausdorff distance. If so, execute S5; if not, execute S1.

[0114] Specifically, S4 includes the following sub-steps:

[0115] S41, performing a fault judgment on the target detection distribution network area based on the first differential protection coefficient. If the first differential protection coefficient is less than the critical threshold, the target detection distribution network area operates normally; if the first differential protection coefficient is greater than or equal to the critical threshold, executing S42;

[0116] S42, based on the Hausdorff distance, a secondary fault analysis is performed on the target detection distribution network area. If the Hausdorff distance exceeds the safe distance range, a fault occurs in the target detection distribution network area, and S5 is executed; if the Hausdorff distance is within the safe distance range, no fault occurs in the target detection distribution network area, and S1 is executed.

[0117] In this embodiment, by comparing the first differential protection coefficient with the critical threshold, it is possible to use the obvious difference between the current amplitude characteristic and the fault state to quickly determine whether a fault has occurred. Among them, the first signal amplitude characteristic ratio increases, the phase angle difference decreases, and the sine angle compensation value of the phase angle difference increases, which indicates that a fault has occurred in the characterization area. When the first differential protection coefficient is greater than or equal to the critical threshold, the larger the first differential protection coefficient, the more serious the fault. Therefore, calculating the first differential protection coefficient for initial fault detection improves the efficiency and reliability of distribution network differential protection.

[0118] S5. Calculate the reliability improvement coefficient based on the first differential protection coefficient, and calculate the safety improvement coefficient based on the second differential protection coefficient.

[0119] Specifically, in S5, calculating the reliability improvement coefficient based on the first differential protection coefficient includes the following sub-steps:

[0120] The first differential protection coefficient is calculated based on a hyperbolic function to obtain a first reliability improvement coefficient and a second reliability improvement coefficient. The calculation formula is as follows:

[0121] (12)

[0122] In the formula, is the first reliability improvement coefficient, is the second reliability improvement coefficient, is the first differential protection coefficient, and e represents the base of the natural logarithm of the hyperbolic function.

[0123] In this embodiment, by calculating the reliability improvement coefficient, the performance of the distribution network differential protection can be clearly understood, which helps to dynamically adjust the reliability improvement coefficient according to the fault status to ensure the stable and safe operation of the distribution network; for example, when an in-area fault occurs, the differential current is increased based on the first reliability improvement coefficient, and the braking current is reduced based on the second reliability improvement coefficient, thereby improving the reliability of the distribution network differential protection.

[0124] Specifically, in S5, calculating the safety improvement coefficient based on the second differential protection coefficient includes: using the second differential protection coefficient as a calculation parameter based on a hyperbolic function to calculate the safety improvement coefficient, and the calculation formula is as follows:

[0125] (13)

[0126] In the formula, represents the safety improvement factor, e represents the base of the natural logarithm of the hyperbolic function, represents the second differential protection coefficient.

[0127] S6. Comprehensively judge the fault type based on the reliability improvement factor, safety improvement factor and current phasor, and perform corresponding protection actions according to the fault type.

[0128] Specifically, S6 includes the following sub-steps:

[0129] Based on the first reliability improvement coefficient, the second reliability improvement coefficient, the safety improvement coefficient, the first current phasor and the second current phasor preset target detection distribution network area protection criterion;

[0130] Determine whether the fault in the target detection distribution network area is an internal fault according to the protection criterion, and if so, send a trip signal to the circuit breaker; if not, do not send a trip signal to the circuit breaker;

[0131] The protection criteria are expressed as follows:

[0132] (14)

[0133] In the formula, K represents the switch action safety factor, is the first current phasor, is the second current phasor, represents the safety improvement factor, is the first reliability improvement coefficient, is the second reliability improvement coefficient.

[0134] Furthermore, if Greater than , it is determined to be an internal fault; if Less than or equal to , it is determined to be an out-of-zone fault.

[0135] In this embodiment, taking into account the several milliseconds required for fault detection and the fact that the current transformer saturation lasts at least 5 ms, the reliability improvement factor and the safety improvement factor can be combined with the comprehensive analysis of the current phasor and the formulation of protection criteria to effectively ensure that the sensitivity of the enhanced current differential protection during the fault within the zone is not affected, ensure that the protection does not refuse to operate during the fault within the zone and does not malfunction during the fault outside the zone, and improve the sensitivity of the differential protection during the fault within the zone; and during the fault outside the zone under non-ideal conditions, it can reduce the differential current and increase the braking current to improve the safety of the distribution network differential protection. Among them, the use of the hyperbolic tangent function mainly utilizes the nonlinear characteristics of the function, which can better handle complex current waveform characteristics, so that it can more flexibly adapt to different current waveform changes and enhance the protection system's detection ability for complex faults; at the same time, the protection criterion that only considers the phasor may be affected by power grid changes and interference, while the hyperbolic tangent function has a relatively strong ability to suppress noise and interference. Improving the criterion based on the hyperbolic tangent function can reduce the impact of these interferences to a certain extent, improve the stability and reliability of the protection system, and adapt to current changes and fault conditions in complex distribution network environments, thereby improving the operation efficiency and safety of the distribution network.

[0136] The beneficial effects of the embodiment are as follows: by calculating the characteristic ratio of the signal amplitude and the phase angle difference at both ends of the line, and then calculating the first differential protection coefficient, it is possible to preliminarily detect whether there is a fault in the line according to the first differential protection coefficient, and reflect the change of the fault state through the change characteristics of the signal amplitude and phase angle, which is helpful to distinguish the fault type, realize targeted fault processing, and make corresponding protection action decisions; by calculating the Hausdorff distance, the current phasors at both ends can be compared, so as to identify the offset and deformation of the line, and further calculate the safety improvement factor and reliability improvement factor of the distribution network according to the Hausdorff distance to realize fast and accurate judgment of the type of fault occurring in the line and fault location; by calculating the Hausdorff distance and combining the safety improvement factor and the reliability improvement factor to evaluate the distribution network in multiple dimensions, the fault judgment criteria are made more comprehensive, reliable and accurate, and the differential protection system's perception of the line state is significantly enhanced, and the difference between normal operation and fault conditions is comprehensively, efficiently and reliably distinguished, thereby reducing misjudgment. Among them, the safety improvement factor and the reliability improvement factor can more carefully reflect the impact of faults on the distribution network, more effectively identify non-fault conditions, prevent protection misoperation and thus improve the reliability of protection; at the same time, the introduction of a comprehensive judgment criterion for the safety improvement factor and the reliability improvement factor provides a basis for formulating more effective protection measures, so that the protection measures can be flexibly adjusted according to different situations, thereby improving the adaptability and flexibility of the protection, and solving the problem that traditional current differential protection lacks comprehensive data analysis of multi-terminal quantities, resulting in unreliable fault judgment and poor protection performance, significantly improving the protection performance as well as the accuracy and reliability of the protection, and further ensuring the safe and stable operation of the distribution network.

[0137] The above specific embodiments are preferred embodiments of the present invention, and are not intended to limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to the present specific embodiments. All equivalent changes made in accordance with the shape, structure, and method of the present invention are within the protection scope of the present invention.

Claims

1. A distribution network differential protection method based on current amplitude and phase characteristics and distance algorithm, characterized by: The steps include: S1. Acquire real-time power parameters at both ends of the protection installation in the target detection distribution network area, extract the current phasor and calculate the first signal amplitude characteristic ratio and phase angle difference at both ends of the protection installation; S2. Calculating a first differential protection coefficient based on the first signal amplitude characteristic ratio and the phase angle difference; S3, using the real-time power parameter as an input parameter of a Hausdorff distance algorithm, and calculating the Hausdorff distance at both ends of the protection installation and a second differential protection coefficient; S4, secondarily judging whether a fault occurs in the target detection distribution network area according to the first differential protection coefficient and the Hausdorff distance, if so, executing S5; if not, executing S1; S5. Calculating a reliability improvement coefficient based on the first differential protection coefficient, and calculating a safety improvement coefficient based on the second differential protection coefficient; S6. Comprehensively determine the fault type based on the reliability improvement coefficient, the safety improvement coefficient and the current phasor, and perform corresponding protection actions according to the fault type; The S4 comprises the following sub-steps: S41, performing a fault judgment on the target detection distribution network area based on the first differential protection coefficient. If the first differential protection coefficient is less than a critical threshold, the target detection distribution network area operates normally; if the first differential protection coefficient is greater than or equal to the critical threshold, executing S42; S42, performing secondary fault judgment on the target detection distribution network area based on the Hausdorff distance. If the Hausdorff distance exceeds the safe distance range, the target detection distribution network area has a fault, and S5 is executed; if the Hausdorff distance is within the safe distance range, the target detection distribution network area has no fault, and S1 is executed.

2. The distribution network differential protection method based on current amplitude and phase characteristics and distance algorithm according to claim 1 is characterized in that: The S1 comprises the following sub-steps: S11, collecting real-time power parameters at both ends of the protection installation in the target detection distribution network area based on a discrete sampling method, and obtaining discrete sequence point sets at both ends of the protection installation, including a first discrete sequence point set and a second discrete sequence point set; S12, performing data transformation on the first discrete sequence point set and the second discrete sequence point set based on discrete Fourier transform to obtain a first current phasor of the first discrete sequence point set and a second current phasor of the second discrete sequence point set; S13, calculating a first signal amplitude characteristic ratio according to the amplitudes of the first current phasor and the second current phasor; S14. Calculate the phase angle difference based on the argument of the first current phasor and the second current phasor.

3. The distribution network differential protection method based on current amplitude and phase characteristics and distance algorithm according to claim 2 is characterized in that: The S2 comprises the following sub-steps: The first differential protection coefficient is obtained by summing the sinusoidal angle compensation of the phase angle difference and the first signal amplitude characteristic ratio.

4. The distribution network differential protection method based on current amplitude and phase characteristics and distance algorithm according to claim 2 is characterized in that: The S3 comprises the following sub-steps: S31, calculating the Hausdorff one-way distance between the first discrete sequence point set and the second discrete sequence point set based on the opposite number of the first current phasor and the second current phasor; S32, calculating the Hausdorff distance between the first discrete sequence point set and the second discrete sequence point set based on the Hausdorff one-way distance, and merging the Hausdorff distances to obtain a data window point set; S33. Extracting the sample ratio of the Hausdorff distance based on the data window point set, and calculating the second differential protection coefficient.

5. The distribution network differential protection method based on current amplitude and phase characteristics and distance algorithm according to claim 4 is characterized in that: The S31 includes: Calculate a first Hausdorff one-way distance from the first discrete sequence point set to the second discrete sequence point set and a second Hausdorff one-way distance from the second discrete sequence point set to the first discrete sequence point set based on the opposite number of the first current phasor and the second current phasor; The calculation formula of the first Hausdorff one-way distance is as follows: ； The calculation formula of the second Hausdorff one-way distance is as follows: ； In the formula, represents the Euclidean distance between the sampling points at both ends of the protection installation, is the first Hausdorff one-way distance, is the second Hausdorff one-way distance, represents the current phasor of the sampling point from the i-th sampling point in the first discrete sequence point set to the j-th sampling point in the second discrete sequence point set, represents the current phasor of the jth sampling point in the second discrete sequence point set that is closest to the ith sampling point in the first discrete sequence point set, represents the first discrete sequence point set, Denotes the second discrete sequence point set.

6. The distribution network differential protection method based on current amplitude and phase characteristics and distance algorithm according to claim 4 is characterized in that: The S33 comprises the following sub-steps: According to the data window point set, the sample ratio information of the Hausdorff distance under the distribution network line fault state is obtained, and the second differential protection coefficient is calculated; The calculation formula of the second differential protection coefficient is as follows: ； In the formula, is the second differential protection coefficient, i represents the number of current sampling points, It represents the number of sampling points in the data window point set 10ms after the fault is detected. total in 10 ms Indicates that the time to record the number of sampling points after a fault is detected is 10 milliseconds. It indicates the number of samples in the data window point set for which the Hausdorff distance does not approach 0.

7. The distribution network differential protection method based on current amplitude and phase characteristics and distance algorithm according to claim 2 is characterized in that: In the S5, calculating the reliability improvement coefficient based on the first differential protection coefficient includes the following sub-steps: The first differential protection coefficient is calculated based on a hyperbolic function to obtain a first reliability improvement coefficient and a second reliability improvement coefficient. The calculation formula is as follows: ； In the formula, is the first reliability improvement coefficient, is the second reliability improvement coefficient, is the first differential protection coefficient, and e represents the base of the natural logarithm of the hyperbolic function.

8. The distribution network differential protection method based on current amplitude and phase characteristics and distance algorithm according to claim 1 is characterized in that: In S5, calculating the safety improvement factor based on the second differential protection factor includes: using the second differential protection factor as a calculation parameter based on a hyperbolic function to calculate the safety improvement factor, and the calculation formula is as follows: ； In the formula, represents the safety improvement coefficient, e represents the base of the natural logarithm of the hyperbolic function, represents the second differential protection coefficient.

9. The distribution network differential protection method based on current amplitude and phase characteristics and distance algorithm according to claim 7 is characterized in that: The S6 comprises the following sub-steps: Presetting a protection criterion for the target detection distribution network area based on the first reliability improvement coefficient, the second reliability improvement coefficient, the safety improvement coefficient and the first current phasor and the second current phasor; Determine whether the fault in the target detection distribution network area is an internal fault according to the protection criterion, and if so, send a trip signal to the circuit breaker; if not, do not send a trip signal to the circuit breaker; The protection criteria are expressed as follows: ； In the formula, K Indicates the safety factor of switch action, is the first current phasor, is the second current phasor, represents the safety improvement factor, is the first reliability improvement coefficient, is the second reliability improvement coefficient.

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