Wiring error electric leakage user identification method and device for low-voltage distribution area

Abstract

The invention provides a low-voltage distribution area wiring error electric leakage user identification method and device. The low-voltage distribution area wiring error electric leakage user identification method comprises the following steps: (A) in an acquisition time period, acquiring residual current of a tested area and load current of each user in the tested area at a set sampling interval; and calculating a correlation coefficient matrix so as to obtain the correlation coefficient of the load current of the jth user in the tested area with respect to the real part and imaginary part of the residual current in the tested area. And (B) if the amplitude of the multiple correlation coefficient of the jth user is greater than or equal to a preset threshold value, judging that the jth user is a wiring error electric leakage user, otherwise, judging that the jth user is a normal user.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power systems, and in particular to detection and identification of leakage faults caused by incorrect connection of neutral and ground wires of users in a low-voltage distribution station area. Background Art

[0002] As the end of the power supply system, the low-voltage substation is the last station connecting the power grid and electricity users. Due to the complexity of the feeder lines in the substation, the unpredictable operating environment of the lines and equipment, leakage faults are common in the daily life and production of residents, directly threatening the safety of people's lives and property. In order to ensure the personal safety of users, the low-voltage substation adopts graded residual current protection (RCD) to selectively isolate leakage faults, and reliably ground the conductive shell of the electrical appliance through the grounding protection line. When a leakage fault occurs and the RCD loses its protective function, the voltage of the electrical shell can still be limited to a safe level to ensure the personal safety of users.

[0003] However, there are many causes of leakage faults in the substation area, all of which can cause the leakage protection device to trip. When a fault occurs, the coordinated operation of the graded RCD can help reduce the impact of the fault and the scope of investigation, but it does not provide more information about the fault itself, such as the type of fault, the location of the fault, etc. Some users also have problems with the configuration and use of RCDs that do not meet the requirements, resulting in the leakage protection device tripping beyond the level, further increasing the difficulty of locating the leakage fault. If the leakage fault is not cleared in time, the frequent tripping of the RCD will seriously affect the reliability of power supply.

[0004] In low-voltage distribution substations, incorrect wiring of the neutral and ground wires in the user's distribution box is a common fault caused by human negligence. When the user uses electricity, the load current returns from the ground wire to the neutral point of the transformer, and the residual current in the substation increases significantly, which will cause the RCD to trip intermittently. Since incorrect wiring of the neutral and ground wires does not affect normal power consumption, when the user fails to locate and troubleshoot the fault, the final RCD is exited, which will cause the upper RCD to trip frequently. Incorrect wiring of the user's neutral and ground wires and leakage are common reasons for the difficulty in commissioning RCD in the substation; if the fault is not located in time, the continuous load current will also burn the ground wire connector and cause an abnormal increase in grounding resistance, making the conductive shells of all users' electrical appliances connected to the ground wire charged, significantly increasing the risk of electric shock casualties.

[0005] According to the correlation between the abnormal residual current in the substation area and the load current of the faulty user when the wiring error fault occurs, the existing technology generally constructs a multiple linear regression equation using the load current and the residual current amplitude to calculate the weight coefficient values of each user and determine the existence of abnormal users. However, the wiring error leakage fault may occur in a single user, or it may occur in multiple users in a certain phase of the three-phase (phase A, phase B, phase C), or it may occur in multiple users in different phases of the three-phase. The multiple linear regression equation of the existing technology only focuses on the current amplitude for multiple linear regression, which is only a description of the linear relationship between the residual current in the substation area and the load current of the user. It has a good recognition effect for identifying a single faulty user, but when there are multiple users with wiring error leakage faults in different phases, the recognition effect is poor, and there are significant false detections and missed detections, and it is impossible to accurately identify the users with wiring error leakage faults. Summary of the Invention

[0006] The problem to be solved by the present invention is that the existing method for identifying abnormal users with wiring errors by constructing a multiple linear regression equation using load current and residual current amplitude has a poor recognition effect when there are multiple users with wiring error leakage faults in different phases, and provides a method for identifying users with wiring error leakage faults in a low-voltage distribution substation area.

[0007] To solve the above technical problems, the technical solution of the present invention is: a method for identifying users with wiring error leakage faults in a low-voltage distribution substation area, including:

[0008] (A) During the acquisition time period, the residual current of the measured substation area and the load current of each user in the measured substation area are collected at a set sampling interval; the correlation coefficient matrix α is calculated using the following formula, so as to obtain the correlation coefficient α of the real part of the load current of the jth user in the measured substation area with respect to the real part of the residual current of the measured substation area j.x and the correlation coefficient α of the imaginary part of the load current of the jth user in the measured substation area with respect to the imaginary part of the residual current of the measured substation area j.y :

[0009] α = (A T A) -1 A T b;

[0010] where: the expression of α is α = [α 1.x , α 1.y , α 2.x , α 2.y ,..., α M+N+P.x , α M+N+P.y T ;

[0011]

[0012]

[0013] ​ denotes the real part of the load current of the j-th user in the measured area at the sa-th sampling point, denotes the imaginary part of the load current of the j-th user in the measured area at the sa-th sampling point; denotes the real part of the residual current in the measured area at the sa-th sampling point, denotes the imaginary part of the residual current in the measured area at the sa-th sampling point; j ∈ [1, M + N + P]; M, N, P represent the number of users in phase A, phase B, and phase C in the three-phase current, sa ∈ [1, S], and S represents the number of sampling values; A T denotes the transpose matrix of A; (A T A) -1 denotes A T the inverse matrix of A;

[0014] (B) If β j is greater than or equal to the preset threshold value, then it is determined that the j-th user is a user with wiring error and leakage, otherwise, it is determined that the j-th user is a normal user;

[0015] wherein, the amplitude value β of the complex correlation coefficient of the j-th user is calculated by the following formula j :

[0016]

[0017] When the applicant was researching, it was found that due to the differences in the composition of household appliances of each user, the phases of their load currents are also different. When a wiring error fault occurs, after the phasor synthesis of the load currents of multiple abnormal users and the natural residual current in the area, it will significantly affect the correlation between the synthesized residual current in the area and the time series fluctuation trend of the load current of abnormal users. According to the above settings, the present invention considers the complex forms of the residual current in the area and the user load current, that is, at each sampling point, the real part and the imaginary part of the residual current in the area and the real part and the imaginary part of the load current of each user are obtained, and then the correlation coefficient α of the load current of the j-th user in the measured area with respect to the real part of the residual current in the measured area j.x and the correlation coefficient α of the load current of the j-th user in the measured area with respect to the imaginary part of the residual current in the measured area j.y are obtained, and then the amplitude value β of the complex correlation coefficient of the j-th user is calculated j , and according to the amplitude value β of the complex correlation coefficient jBased on the magnitude relationship with the preset threshold, it is determined whether the user has wiring error and leakage. For single-user wiring error and leakage faults (single-user faults), multiple-user wiring error and leakage faults of a certain phase in three phases (A phase, B phase, C phase) (multi-user faults of the same phase), and multiple-user wiring error and leakage faults of different phases in three phases (multi-user faults of different phases), since the currents of each user in the complex domain are complex numbers, the amplitude and phase data in the polar coordinate system can be measured, and then converted into the real part and imaginary part data in the rectangular coordinate system. Therefore, according to the above method of the present invention, for single-user faults, multi-user faults of the same phase, and multi-user faults of different phases, the real part correlation coefficient and the imaginary part correlation coefficient can be obtained, and then it is determined whether the user is a user with wiring error and leakage according to the amplitude of the complex correlation coefficient of each user, so as to achieve the effect of effectively identifying faulty users in multiple fault scenarios.

[0018] In the above technical solution, It is calculated by the following formula:

[0019]

[0020] wherein, is the amplitude of the load current of the jth user in the measured distribution area at the sa-th sampling point, is corresponding to phase angle.

[0021] In the above technical solution, It is calculated by the following formula:

[0022]

[0023] wherein, is the amplitude of the residual current in the measured distribution area at the sa-th sampling point, is corresponding to phase angle.

[0024] In the above technical solution, the preset threshold is 0.8.

[0025] In the above technical solution, the value range of the set sampling interval is [1 min, 30 min].

[0026] In the above technical solution, S≥200.

[0027] Based on the same inventive concept, the present invention also provides a device for identifying users with wiring error and leakage in a low-voltage distribution area, including a computer device; the computer device is configured or programmed to execute the steps of the above method for identifying users with wiring error and leakage in a low-voltage distribution area. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0029] Figure 1(a) is a scatter plot of the minute-level residual current throughout the day for a normal power distribution area obtained according to an embodiment of the present invention. Each dot in Figure 1 corresponds to a minute-level residual current acquisition point.

[0030] Figure 1(b) is the resistance component (blue dots) and reactance component (green dots) of the minute-level residual current throughout the day for the corresponding normal power distribution area in Figure 1.

[0031] Figure 2 is a time series diagram of the residual current for a single-user wiring error power distribution area obtained according to an embodiment of the present invention.

[0032] Figure 3 is a phasor diagram of the residual current at time t for a single-user wiring error power distribution area obtained according to an embodiment of the present invention.

[0033] Figure 4 is a time series diagram of the residual current for a two-users-in-phase wiring error power distribution area obtained according to an embodiment of the present invention.

[0034] Figure 5 is a phasor diagram of the current at time t for a two-users-in-phase wiring error power distribution area obtained according to an embodiment of the present invention.

[0035] Figure 6 is a time series diagram of the residual current for a two-users-in-opposite-phase wiring error power distribution area obtained according to an embodiment of the present invention.

[0036] Figure 7 is a phasor diagram of the current at time t for a two-users-in-opposite-phase wiring error power distribution area obtained according to an embodiment of the present invention.

[0037] Figure 8 is a flow chart of a method for identifying wiring error and leakage fault users based on a real and imaginary part separation multiple linear regression method according to an embodiment of the present invention. Detailed implementation manners

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present application.

[0039] The present invention provides a method for identifying a user with wiring error and leakage in a low-voltage distribution substation area, including:

[0040] (A) During the acquisition time period, the residual current of the measured substation area and the load current of each user in the measured substation area are acquired at a set sampling interval; the correlation coefficient matrix α is calculated using the following formula:

[0041] α = (A T A) -1 A T b;

[0042] Where:

[0043]

[0044] represents the real part of the load current of the j-th user in the measured substation area at the sa-th sampling point, represents the imaginary part of the load current of the j-th user in the measured substation area at the sa-th sampling point; represents the real part of the residual current of the measured substation area at the sa-th sampling point, represents the imaginary part of the residual current of the measured substation area at the sa-th sampling point; j ∈ [1, M + N + P]; M, N, P represent the number of users in phase A, phase B, and phase C in the three-phase current, sa ∈ [1, S], S represents the number of sampling values; A T represents the transpose matrix of A; (A T A) -1 represents the inverse matrix of A T A;

[0045] After calculating the correlation coefficient matrix α, according to the following formula:

[0046] [α 1.x , α 1.y , α 2.x , α 2.y ,..., α M+N+P.x , α M+N+P.y ) T = α;

[0047] Thus, the correlation coefficient α j.x of the real part of the load current of the j-th user in the measured substation area with respect to the real part of the residual current of the measured substation area, and the correlation coefficient α j.y of the imaginary part of the load current of the j-th user in the measured substation area with respect to the imaginary part of the residual current of the measured substation area are obtained;

[0048] (B) If β j is greater than or equal to the preset threshold, it is determined that the j-th user is a user with wiring error and leakage; otherwise, it is determined that the j-th user is a normal user;

[0049] Among them, the amplitude β of the complex correlation coefficient of the j-th user is calculated by the following formula j :

[0050]

[0051] It is calculated by the following formula:

[0052]

[0053] Among them, is the amplitude of the load current of the j-th user in the measured power distribution area at the sa-th sampling point, is corresponding to phase angle. Among them, collecting the user load current and obtaining the amplitude and phase angle of the user load current are all prior arts.

[0054] It is calculated by the following formula:

[0055]

[0056] Among them, is the amplitude of the residual current in the measured power distribution area at the sa-th sampling point, is corresponding to phase angle. Among them, collecting the residual current in the measured power distribution area and obtaining the amplitude and phase angle of the residual current in the measured power distribution area are all prior arts.

[0057] The preset threshold is 0.8. The value range of the set sampling interval is [1 min, 30 min]. S≥200.

[0058] According to the same inventive concept, the present invention also provides a device for identifying a user with wiring error and leakage in a low-voltage power distribution area, including a computer device; the computer device is configured or programmed to execute the steps of the above method for identifying a user with wiring error and leakage in a low-voltage power distribution area.

[0059] The following further details the solution of the present invention.

[0060] In a low-voltage distribution substation area, when a leakage fault occurs due to incorrect connection of the neutral line and the ground wire in a user's distribution box, all the load current of the user will be converted into the residual current in the substation area, and its value is much larger than the natural residual current. The main component of the residual current in the substation area changes to the abnormal user load current, and its fluctuation characteristics are highly correlated with the abnormal user's electricity consumption behavior. Since the phases of the users in the substation area are different, the voltage phases of the users in phases A, B, and C differ by 120°. The user current is affected by the load characteristics of household appliances indoors and leads or lags behind the user voltage. Due to the differences in the composition of household appliances of each user, the phases of their load currents are also different. When a fault of reverse connection of the neutral line and the ground wire occurs, after the phasor synthesis of multiple abnormal user load currents and the natural residual current in the substation area, it will significantly affect the correlation between the synthesized residual current in the substation area and the time series of the abnormal user load current.

[0061] In the present invention, considering the influence of the user phase and the load current phase, a phasor model of the residual current in the substation area and a linear relationship model between it and the user load current are constructed in the complex domain to analyze the influence of the leakage fault caused by incorrect connection of the neutral line and the ground wire on the residual current in the substation area. Furthermore, the multiple regression algorithm of real and imaginary part separation is used to calculate the complex correlation coefficient of each user's load current with respect to the residual current in the substation area, and a threshold is set to distinguish abnormal users.

[0062] The present invention utilizes the linear relationship between the residual current in the substation area and the user load current in the complex domain to provide clearer and more accurate information for troubleshooting leakage faults caused by incorrect wiring. Based on the real and imaginary components, multiple linear regression equations are constructed to calculate the suspicion coefficients of incorrect wiring for each user.

[0063] The purpose of the present invention is to consider the differences between the user phase and the load current phase, analyze the influence of abnormal users on the residual current in the substation area when a leakage fault occurs due to incorrect connection of the neutral line and the ground wire, construct a phasor model of the residual current in the substation area and a linear relationship model between it and the user load current, and provide more accurate and detailed fault information for fault perception and troubleshooting of incorrect wiring faults. To achieve the above object, the present invention establishes a phasor model of the residual current in the substation area under the fault of incorrect connection of the neutral line and the ground wire, analyzes the linear relationship between the residual current in the substation area and the user load current based on different fault scenarios, constructs multiple linear regression equations of real and imaginary part separation, and calculates the suspicion coefficients of incorrect wiring faults for each user.

[0064] The present invention classifies and analyzes the leakage faults caused by reverse connection of the neutral line and the ground wire indoors in a low-voltage distribution substation area, establishes a phasor model of the residual current in the substation area, and then identifies the users with leakage faults due to incorrect wiring.

[0065] Under the three fault scenarios of single - user fault, in - phase multi - user fault, and out - of - phase multi - user fault, the dependent variable is the remaining current in the distribution transformer area, and the independent variable is still the user load current. The difference lies in the different sources of leakage current included in the remaining current in the distribution transformer area. In the first fault case, it comes from a single user; in the second fault case, it comes from multiple in - phase users; in the third fault case, it comes from multiple out - of - phase users. In different cases, there is a characteristic of phase synthesis, which is difficult to reflect in the comparison of amplitudes. However, according to the method of the present invention, in the complex domain, the real part and the imaginary part can be algebraically superimposed separately, so as to effectively separate the correlation coefficients corresponding to each user (the correlation coefficient α j.x of the load current of the j - th user with respect to the real part of the remaining current in the measured distribution transformer area, and the correlation coefficient α j.y of the load current of the j - th user with respect to the imaginary part of the remaining current in the measured distribution transformer area).

[0066] The present invention constructs a phasor model of the remaining current in the distribution transformer area under the zero - line and ground - line reverse connection leakage fault. As Figure 8 shown, the steps for constructing the phasor model of the remaining current in the distribution transformer area under the zero - line and ground - line reverse connection leakage fault are as follows:

[0067] A. The establishment of this model mainly involves the change of the fault leakage current component that plays a dominant role in the remaining current in the distribution transformer area under the zero - line and ground - line reverse connection leakage fault, and considers the differences in the phase and power factor of the fault users, and analyzes the phasor superposition result of the leakage current from the fault location and the natural remaining current in the distribution transformer area.

[0068] B. Consider the differences in the number of wiring error faults and the phases they are in, and classify the zero - line and ground - line reverse connection leakage faults.

[0069] C. Based on Kirchhoff's current law, analyze the composition and physical connection of the remaining current in the distribution transformer area when different types of wiring error faults occur, and construct a phasor model of the remaining current in the distribution transformer area under the wiring error fault in the complex domain to characterize the influence of the fault current on the remaining current in the distribution transformer area. Its expression is as follows:

[0070]

[0071] Among them, is the phasor of the remaining current in the distribution transformer area at the sa - th sampling point, is the phasor of the fault leakage current at the sa - th sampling point, represents the phasor of the natural remaining current in the distribution transformer area at the sa - th sampling point.

[0072] The establishment of this model does not consider the occurrence of other leakage faults in the distribution transformer area. The fault leakage current in step A refers to the load current of the user with wiring error leakage fault.

[0073] In step B, according to the number of wiring error faults, this fault can be divided into single-user wiring errors and multi-user wiring errors. In the case of multi-user wiring errors, according to the different phases of the faulty users with wiring errors, this fault can be divided into in-phase leakage faults with wiring errors and out-of-phase leakage faults with wiring errors.

[0074] Both the residual current in the substation area and the user load current consider the influence of phase, and are expressed in the rectangular coordinate form in the complex domain, with a resistance component and a reactance component, such as Among them

[0075] In the case of single-user zero-line and ground-line reverse connection leakage faults, the user load current is all converted into the residual current in the substation area. The amplitude level of the abnormal user load current is much higher than that of the natural leakage current in the substation area, dominating the fluctuation of the residual current in the substation area.

[0076] In the case of in-phase multi-user zero-line and ground-line reverse connection leakage faults, the phase differences of the user load currents are relatively small, and the phasor synthesis has an enhancement effect. At any moment, the amplitude level of the residual current in the substation area is higher than that of any one of the users, and the fluctuation will be quite different from that of the abnormal user load current.

[0077] In the case of out-of-phase multi-user zero-line and ground-line reverse connection leakage faults, the phase differences of the user load currents are relatively large, and the phasor synthesis has a weakening effect. At different moments, the amplitude level of the residual current in the substation area is lower than that of the user with the highest amplitude at this time, and the fluctuation will be quite different from that of the abnormal user load current.

[0078] Considering the characteristics of current phasor synthesis, a real and imaginary part separation regression method is used to identify the users with wiring error leakage faults.

[0079] Based on the phasor data of the residual current in the substation area and the user load current, with the residual current in the substation area as the dependent variable and the user load current as the independent variable, a multiple linear regression equation for real part data and a multiple linear regression equation for imaginary part data are respectively constructed.

[0080] At intervals of 15 minutes, the phasor data of the total residual current in the substation area and the load currents of each user are collected. The number of users is M + N + P, specifically including amplitude and phase, so as to obtain real part component and imaginary part component data, and the total number of sample points is S points.

[0081] The real part multiple linear regression equation set is as follows:

[0082]

[0083] Among them, represents the magnitude of the real part of the load current of user j at the sa-th sampling point, α j.xdenotes the correlation coefficient of the real part of the load current of the j-th user with respect to the real part of the residual current, where j ∈ [1, M + N + P].

[0084] The imaginary part multiple linear regression equation is as follows:

[0085]

[0086] Where, denotes the magnitude of the imaginary part of the load current of user j at the sa-th sampling point, and α j.y denotes the correlation coefficient of the imaginary part of the load current of the j-th user with respect to the imaginary part of the residual current, where j ∈ [1, M + N + P].

[0087] Construct a combined system of real and imaginary part multiple linear regression equations with a total dimension of S and 2(M + N + P) independent variables. Using the sum of squared residuals RMSE as the loss function, find the optimal real and imaginary part proportionality coefficients by minimizing it.

[0088] Based on the obtained optimal real and imaginary part proportionality coefficients, construct the complex correlation coefficient β of the load current of the j-th user with respect to the residual current in the transformer substation area i , and calculate the magnitude of the complex correlation coefficient as an evaluation index:

[0089]

[0090] Use 0.8 as the threshold for segmentation to distinguish normal users and abnormal users. If the magnitude is higher than 0.8, it is an abnormal user; if the magnitude is lower than 0.8, it is a normal user.

[0091] The present invention discloses a phasor model of residual current in a transformer substation area and a method for identifying users with wiring error leakage faults for incorrect wiring of neutral and ground wires of low-voltage users, which is used to describe the phasor composition of the residual current in the transformer substation area when a wiring error fault occurs indoors of a user. Considering the user phase and power factor angle, analyze the phasor relationship between the residual current in the transformer substation area and the load current of each abnormal user when different types of incorrect wiring faults of neutral and ground wires occur, establish a corresponding phasor model of the residual current in the transformer substation area, and further comprehensively consider the correlation between the current resistance component and the reactance component, and use the real and imaginary part separation regression method to identify abnormal users. The present invention further considers the influence of the user wiring error leakage fault on the residual current in the transformer substation area from the perspective of phasors, which is closer to the engineering reality, can effectively improve the accuracy of identifying users with wiring error faults, provide prior guidance for leakage fault investigation, thereby improving the operation rate of leakage protection in the transformer substation area and ensuring the safety of user electricity consumption.

[0092] Theoretically, the residual current in the transformer substation area can be calculated from the three-phase current on the low-voltage side of the distribution transformer and the neutral wire current, and its formula is:

[0093]

[0094] wherein represents the residual current of the transformer substation area, represents the current of phase A, represents the current of phase B, represents the current of phase C, represents the current of the N line (i.e., the current of the neutral line N).

[0095] However, it is difficult to reflect the composition of the residual current inside the transformer substation area by calculating the residual current using the bus current. In fact, the current of phase A is the phasor sum of the load currents of each user in phase A, the current of phase B is the phasor sum of the load currents of each user in phase B, the current of phase C is the phasor sum of the load currents of each user in phase C, and the zero-sequence current of the neutral line is the phasor sum of the zero-line currents of each user in the transformer substation area. The formula can be further expanded as:

[0096]

[0097] wherein: represents the load current of the j-th user, j ∈ [1, M + N + P]. ……, are respectively the load currents of M users in phase A, that is, the 1st user, ……, the M-th user are respectively called user A1, ……, user AM; ……, are respectively the load currents of N users in phase B, that is, the (M + 1)-th user, ……, the (M + N)-th user are respectively called user B1, ……, user BN; ……, are respectively the load currents of P users in phase C, that is, the (M + N + 1)-th user, ……, the (M + N + P)-th user are respectively called user C1, ……, user CP; is the current of the j-th user; is the leakage current of the power supply line of the transformer substation area to the ground.

[0098] It can be further written as:

[0099]

[0100] wherein is the residual current of the j-th user in the transformer substation area, j ∈ [1, M + N + P], and the residual current of the transformer substation area is the phasor sum of the residual currents of each user and the residual current of the power supply line to the ground.

[0101] Based on the above ideas, the basic idea of ​​the present invention is to use Kirchhoff's current law to analyze the changes in the residual current composition of the substation when a neutral line or ground line wiring error occurs, and consider the difference between the user phase and the load current phase, and study the phasor synthesis results of the fault leakage current and the natural residual current of the substation, and then construct a substation residual current phasor model in the complex domain, and then use the real and imaginary part separation to construct a multivariate linear regression equation, and calculate the correlation coefficient of each user's wiring error leakage fault in the real domain.

[0102] First, the natural residual current data of the substation is analyzed. The minute-level data fluctuation curve of the residual current on the distribution transformer side of a normally operating substation for one day (i.e., one dot corresponds to the residual current per minute) is shown in Figure 1(a). Under normal circumstances, the substation only has a small natural leakage current, which comes from the earth reactance leakage current of the power supply line before the user's meter and the small leakage current of the user's indoor lines and equipment. This part of the leakage current has a small amplitude and fluctuates smoothly. The amplitude is kept below 300mA, which is related to the user's electricity consumption behavior and the current intensity on the line. In addition, as shown in Figure 1(b), the reactance component and resistance component of the residual current account for a similar proportion and fluctuate smoothly.

[0103] 1. When the M+1 user (i.e. the M+1th user among the M+N+P users) located in phase B in the substation encounters a reverse connection and leakage fault of the neutral line and ground line in the indoor distribution box, the load current of the user will return from the grounding wire to the neutral point of the transformer and be completely converted into residual current in the substation. becomes Since the amplitude of the user load current is significantly higher than the natural residual current of the substation, the fluctuation characteristics of the substation residual current obtained after the phase synthesis of the two are highly similar to the abnormal user load current. The calculation formula of the substation residual current is:

[0104]

[0105] like Figure 2 As shown, the solid line with a triangle data label refers to the load current of user M+1 (i.e. user B1). The solid line with circular data labels represents the natural residual current in the substation without considering the leakage current of user M+1. The dotted line with circular data labels represents the residual current in the substation area when the leakage current of user M+1 is considered. from Figure 2 It can be seen that the amplitude of the natural leakage current is low, while the load current of user B1 overlaps with the residual current of the substation to a large extent. Figure 2 , Figure 4 , Figure 6 The horizontal axis of has the same meaning as that of Figure 1(a) and Figure 1(b).

[0106] Further, the phasor composition of the remaining current in the transformer substation area at time t is as follows Figure 3 As shown, the natural remaining current in the transformer substation area at time t can be decomposed into a resistance component and a reactance component The abnormal user load current at time t brings an increment in the resistance component and an increment in the reactance component According to the phasor decomposition diagram of the remaining current in the transformer substation area at this moment, a phasor model of the remaining current in the transformer substation area for the leakage fault of incorrect wiring of the single-user distribution box can be established as follows: The remaining current in the transformer substation area obtained when considering the (M + 1)-th user at time t is The resistance component and the reactance component thereof are respectively

[0107]

[0108] 2. When there are leakage faults of incorrect wiring of the neutral line and the ground wire in the indoor areas of multiple users in the transformer substation area, since the amplitude levels of the user load currents are similar, the phasor synthesis result of the abnormal user load currents will be very different from any user load current. Taking the leakage faults of incorrect wiring of two users in the transformer substation area as an example, since the power frequency power supply is adopted in the low-voltage transformer substation area and the frequency is low, the resistance component in the user load current dominates, so the phase shift of the user load current with respect to the voltage is small. Further, it can be considered that the phase difference of the in-phase user load currents is small, and the phase difference of the out-of-phase user load currents is large.

[0109] Further, when the neutral line and the ground wire of the 1st user and the 2nd user located in phase A are reversely connected and there are leakage faults, all the load currents of these two users are converted into leakage currents become become The amplitude levels of the load currents of the two users are similar and they are both located in phase A. The phasor synthesis of the leakage current in the transformer substation area has an enhanced effect, and the amplitude level of the synthesis result is higher than the amplitude of any abnormal user load current. The calculation formula for the remaining current in the transformer substation area is:

[0110]

[0111] where represents the natural remaining current in the transformer substation area without considering the 1st user (i.e., user A1) and the 2nd user (i.e., user A2), as Figure 4 shown, the solid line with circular data labels refers to the load current of the 1st user The solid line with triangular data labels refers to the load current of the 2nd user The dashed line with circular data labels represents the remaining current in the transformer substation area when considering the leakage currents of the 1st user and the 2nd user

[0112] Furthermore, the composition of the residual current phasor in the low-voltage area at time t is as follows Figure 5 shown. The natural residual current in the low-voltage area at time t can be decomposed into a resistance component and a reactance component in two parts. The abnormal user load current at time t brings an increment in the resistance component and an increment in the reactance component The abnormal user load current at time t brings an increment in the resistance component and an increment in the reactance component The residual current in the low-voltage area obtained when considering the (M + 1)-th user at time t is and its resistance component and reactance component are respectively According to the phasor decomposition diagram of the residual current in the low-voltage area at this moment, a phasor model of the residual current in the low-voltage area for the leakage fault of incorrect wiring of the distribution boxes of two in-phase users can be established as follows:

[0113]

[0114] Furthermore, as Figure 5 shown: When the 3rd user located in phase A (i.e., user A3) and the (M + 3)-th user located in phase B (i.e., user B3) have a leakage fault with the neutral and ground wires reversed, all the load currents of these two users are converted into leakage currents, becomes becomes Since the two users are in different phases and the phase difference is large, the synthesis of the leakage current phasors in the low-voltage area has a weakening effect, and the amplitude level of the synthesis result is lower than the amplitude of the larger abnormal user load current. The formula for the residual current in the low-voltage area is:

[0115]

[0116] where represents the natural residual current in the low-voltage area without considering the 3rd user in phase A and the (M + 3)-th user in phase B (i.e., user B3). As Figure 6 shown, the solid line with a circular data label indicates the load current of the 3rd user (i.e., user A3) The solid line with a triangular data label indicates the load current of the (M + 3)-th user in phase B (i.e., user B3) The dashed line with a circular data label represents the residual current in the low-voltage area when considering the leakage currents of the 3rd user in phase A and the (M + 3)-th user in phase B

[0117] Furthermore, the composition of the residual current phasor in the low-voltage area at time t is as follows Figure 7 shown. The natural residual current in the low-voltage area Can be decomposed into a resistance component and a reactance component into two parts. The abnormal user load current brings an increment in the resistance component and an increment in the reactance component The abnormal user load current brings an increment in the resistance component and an increment in the reactance component The remaining current of the transformer substation at time t considering the (M + 1)-th user is Its resistance component and reactance component are respectively According to the phasor decomposition diagram of the remaining current of the transformer substation at this moment, a phasor model of the remaining current of the transformer substation for the leakage fault of incorrect wiring of the distribution boxes of two in-phase users can be established as follows:

[0118]

[0119] 3. When there is a leakage fault of incorrect wiring in the transformer substation, the change in the real part of the remaining current of the transformer substation is related to the change in the real part of the load current of the faulty user, and the change in the imaginary part is related to the change in the imaginary part of the load current of the faulty user. Taking the real part and the imaginary part of the remaining current of the transformer substation as the explained variables respectively, and the real part and the imaginary part of the load current of each user as the explanatory variables, a multiple linear regression equation is constructed in the real number domain:

[0120]

[0121]

[0122]

[0123] Furthermore, with a sampling interval of 15 minutes, the phasor data of the remaining current and the load current of the transformer substation are collected, including the amplitude and the phase, so as to obtain the magnitudes of the real part and the imaginary part. The total length of the sample is S, and a multiple linear regression equation set is constructed:

[0124]

[0125] Let:

[0126]

[0127]

[0128]

[0129] α = [α 1.x α 1.y α 2.x α 2.y … α M+N+P.x α M+N+P.y ​T ;

[0130] The real and imaginary part separated multi - linear equations can be expressed in matrix form as:

[0131] b = Aα+ε;

[0132] Where A is a real - number matrix of S×(M + N + P). According to the least - squares theory, the minimum value of the sum of the squared moduli of the real - part and imaginary - part residuals of the residual current in the above - mentioned power distribution area is calculated to obtain the optimal real - part correlation coefficient and imaginary - part correlation coefficient. Its target residual function is:

[0133]

[0134] The solution is:

[0135] α=(A T A) -1 A T b;

[0136] Based on the calculated real - part correlation coefficient α x =[α 1.x α 2.x …α M+N+P.x T and imaginary - part correlation coefficient α y =[α 1.y α 2.y … α M+N+P.y T , find its amplitude as the correlation - coefficient evaluation index of the final user:

[0137]

[0138] And use the RMSE value as the evaluation index of the established real - and - imaginary - part multi - linear regression equation:

[0139]

[0140] In the formula, is the estimated value of the residual current at the sa - th sampling point, b sa is the measured value of the residual current at the sa - th sampling point, and S is the sample length.

[0141] ​​As shown in Table 1, in order to verify the effect of the solution of the present invention, a full-scale simulation substation area is constructed, with a total of 18 users supplied. Among them, there are 6 users in phase A (A1, A2, ……, A6), 7 users in phase B (B1, B2, ……, B7), and 5 users in phase C (C1, C2, ……, C5). When there is a wiring error and leakage fault in user A2, when there are wiring error and leakage faults in users A2 and B5 at the same time, and when there are wiring error and leakage faults in users A2 and A4 at the same time, with a sampling interval of 1 minute, phasor time-series data of the residual current in the substation area and the load current of users are collected within a one-day time span to construct a sample set. Further, the amplitude multiple linear regression method and the real and imaginary part separation multiple linear regression method are used to calculate the magnitude of the correlation coefficient of each user's load current with respect to the residual current in the substation area. The calculation results are shown in Table 1. In Table 1, the data of each user corresponding to the method of the present invention are the magnitudes of the complex correlation coefficients calculated for that user (for the j-th user, the magnitude of the complex correlation coefficient is β j ).

[0142] As shown in Table 1, if the preset threshold of the correlation coefficient (for the present invention, it is the preset threshold for comparison with β j ) is set to 0.8, when there is a fault in user A2, both the prior art method and the method of the present invention can effectively identify the fault of user A2. When there are faults in users A2 and A4, the prior art method can only identify the fault of user A2, but when the threshold is set to 0.8, it cannot identify the fault of user A4, and it can only identify the fault of user A4 when the correlation coefficient threshold is set to 0.7 (that is, the prior art method has a high requirement for threshold setting. When the threshold is set too high, it is easy to miss the faulty users, and when the threshold is set too low, normal users may also be determined as faulty users). When there are faults in users A2 and A4, using the method of the present invention and setting the preset threshold to 0.8, the faults of users A2 and A4 can still be effectively identified. When there are faults in users A2, B4, and B6, using the method of the prior art, even when the threshold is set to 0.7, only the fault of user B4 can be identified, and the faults of users A2 and B6 still cannot be identified. When there are faults in users A2, B4, and B6, using the method of the present invention and setting the threshold to 0.8, the faults of users A2, B4, and B6 can be effectively identified.

[0143] In addition, as shown in Table 1, under different fault conditions, the calculated RMSE values obtained according to the prior art are significantly higher than those of the method proposed by the present invention, which also indicates that the identification effect of the method proposed by the present invention is significantly better than that of the prior art method.

[0144] This example shows that in the scenario of wiring error and leakage faults of multiple users, the amplitude multiple linear regression has insufficient ability to distinguish abnormal users, while the method proposed by the present invention (the real and imaginary part separation regression method) can effectively identify abnormal users.

[0145] Table 1

[0146]

[0147] It should be noted that the various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. The embodiments of the present invention have been described in detail above, but the content described is only the preferred embodiments of the present invention and cannot be considered as used to limit the scope of the present invention. All equivalent changes and improvements made according to the scope of the present invention should still fall within the scope covered by the present invention. After reading the present invention, various equivalent forms of modification of the present invention by those skilled in the art all fall within the scope defined by the appended claims of this application. Without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

Claims

1. A method for identifying a user with leakage due to wiring error in a low-voltage distribution substation, characterized in that: Including: (A) During the acquisition time period, the residual current of the measured substation area and the load currents of each user within the measured substation area are acquired at a set sampling interval; the correlation coefficient matrix α is calculated using the following formula, so as to obtain the correlation coefficient α of the real part of the load current of the j-th user within the measured substation area with respect to the real part of the residual current of the measured substation area j.x , and the correlation coefficient α of the imaginary part of the load current of the j-th user within the measured substation area with respect to the imaginary part of the residual current of the measured substation area j.y : α=(A T A) -1 A T b; Among them: The expression of α is α = [α 1.x , α 1.y , α 2.x , α 2.y ,..., α M+N+P.x , α M+N+P.y T ;​ The real part of the load current of the j-th user in the measured area at the sa-th sampling point, represents the imaginary part of the load current of the j-th user in the measured area at the sa-th sampling point; represents the real part of the residual current in the measured area at the sa-th sampling point, represents the imaginary part of the residual current in the measured area at the sa-th sampling point; j ∈ [1, M + N + P]; M, N, P represent the number of users in phase A, phase B, and phase C in the three-phase current, sa ∈ [1, S], and S represents the number of sampling values; A T represents the transpose matrix of A; (A T A) -1 represents A T the inverse matrix of A; (B) If β j is greater than or equal to a preset threshold value, it is determined that the j-th user is a user with a wiring error and leakage. Otherwise, it is determined that the j-th user is a normal user; Among them, the amplitude β of the multiple correlation coefficient of the j-th user is calculated by the following formula j :[[]]END]] 2. The method for identifying a user with wiring error and leakage in a low-voltage power distribution substation according to claim 1, characterized in that: Calculated using the following formula: Among them, is the amplitude of the load current of the j-th user in the measured power supply area at the sa-th sampling point, is corresponding to the phase angle.

3. The method for identifying a user with wiring error and leakage in a low-voltage distribution substation according to claim 1, wherein: Calculate using the following formula: Wherein, is the amplitude of the residual current of the measured power distribution area at the sa-th sampling point, is corresponding to the phase angle.

4. The method for identifying a user with wiring error and leakage in a low-voltage distribution substation according to any one of claims 1-3, characterized in that: The preset threshold is 0.

8.

5. The method for identifying a user with wiring error and leakage in a low-voltage distribution substation according to any one of claims 1-3, characterized in that: The value range of the set sampling interval is [1 min, 30 min].

6. The method for identifying a user with wiring error and leakage in a low-voltage distribution substation according to any one of claims 1-3, characterized in that: S≥200。 7. A device for identifying a user with leakage due to wiring error in a low-voltage distribution substation, characterized in that, Including a computer device; The computer device is configured or programmed to perform the steps of the method for identifying a user with wiring error and leakage in a low-voltage distribution substation area according to any one of claims 1-6.

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