A method and device for locating a single-pole grounding fault in a direct current area of a photovoltaic substation

Abstract

The application discloses a photovoltaic substation DC area single pole grounding fault positioning method and device, the method comprises the following steps: monitoring the positive and negative pole-to-ground voltage and the inter-pole voltage of the photovoltaic substation DC area bus; judging the single pole grounding fault state of the photovoltaic substation DC area according to the positive and negative pole-to-ground voltage and the inter-pole voltage; judging the fault pole according to the relationship between the positive and negative pole-to-ground voltage and the inter-pole voltage when the single pole grounding fault occurs; realizing the positioning of the single pole grounding fault according to the multiple correlation degree characteristics between the transient current and voltage of each interval fault pole when the single pole grounding fault of the photovoltaic substation DC area occurs, and judging the fault line. The application can accurately realize the positioning of the single pole grounding fault according to the correlation degree characteristics of the transient current and voltage of each interval when the single pole grounding fault of the photovoltaic substation DC area occurs, and can accurately judge the fault line.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of direct-current area fault detection of photovoltaic power stations, and particularly relates to a method and device for locating single-pole grounding faults in the direct-current area of a photovoltaic substation. BACKGROUND

[0002] With the continuous development of the world economy, the demand for energy by industry is increasing, and traditional fossil fuels cannot meet the demand. As one of high-quality green energy, solar power generation has the characteristics of economy and environmental protection. Therefore, photovoltaic power generation has developed rapidly, and some large photovoltaic power stations have also begun to be constructed and put into operation in large quantities.

[0003] With the continuous expansion of the scale of photovoltaic power stations, faults in photovoltaic power generation often occur. There are a large number of DC cables between photovoltaic components and between photovoltaic strings and inverters or combiner boxes. Once the insulation layer ages or is damaged due to external factors, ground or short circuit faults occur, the photovoltaic power generation system stops, and the power generation benefit is damaged. At the same time, a high DC voltage can break through the air and cause an electric arc, causing fires, injuries to personnel, damage to equipment, etc. In large photovoltaic power stations, the probability of single-pole grounding faults is the highest in the direct-current area due to the large number of cables and complex wiring. However, due to the small fault current when a single-pole grounding fault occurs, the protection part of the traditional photovoltaic power station cannot normally operate. After the fault occurs, it is difficult to patrol the fault location due to the large number of cables and complexity, thereby causing more serious short circuit faults and even causing the entire photovoltaic power station to shut down.

[0004] In the current technology, a complex mathematical model and algorithm are mostly used to locate single-pole grounding faults in the direct-current area of a photovoltaic power station, but there are problems such as difficulty in modeling, difficulty in extracting fault samples, and low positioning accuracy, which are constrained in actual engineering applications.

[0005] Therefore, there is an urgent need for a single-pole grounding fault positioning technology that can accurately determine the direct-current area of a large photovoltaic power station to ensure reliable operation of the photovoltaic power station. SUMMARY

[0006] In order to solve the problems of poor positioning accuracy and difficulty in implementation of single-pole grounding faults in the direct-current area of a large photovoltaic power station, the application provides a method and device for locating single-pole grounding faults in the direct-current area of a photovoltaic power station.

[0007] The application is implemented according to the following technical scheme:

[0008] On the one hand, the application provides a method for locating single-pole grounding faults in the direct-current area of a photovoltaic power station, and the steps of the method are as follows:

[0009] Monitoring the positive and negative pole-to-ground voltages and the modulus of the inter-pole voltage in the direct-current area of the photovoltaic substation;

[0010] The single-pole grounding fault status of the DC zone of the photovoltaic substation can be determined based on the magnitude of the positive and negative pole-to-ground voltages and the inter-pole voltages.

[0011] When a single-pole grounding fault occurs, the faulty pole can be determined based on the relationship between the positive and negative pole voltages to ground and the magnitude of the inter-pole voltage.

[0012] The location of the single-pole grounding fault is achieved by leveraging the correlation characteristics between the transient currents and voltages of the faulty poles in each section during a single-pole grounding fault in the DC zone of a photovoltaic substation, thus identifying the faulty line.

[0013] In one embodiment, the step of locating the single-pole grounding fault and determining the faulty line based on the correlation characteristics of the fault pole and transient currents and voltages in each section during a single-pole grounding fault in the DC zone of a photovoltaic substation includes:

[0014] The correlation P between the transient component of the reference current in the DC region of a photovoltaic substation under a single-pole ground fault condition and the transient voltage of the fault pole is used to determine the relationship between the transient component and the transient voltage of the fault pole. r·U The correlation P between the transient component of the reference current and the transient components of all line fault pole currents r·k Determine whether a single-pole grounding fault has occurred on the busbar;

[0015] The correlation P between the currents at both ends of the faulty pole of the line k·g·S·W The correlation between the fault pole current and the fault pole voltage on the line bus side, P k·s·u To identify the faulty circuit;

[0016] The correlation P between the positive and negative currents at the beginning of the line k·s·+- The correlation between barrier current and fault voltage P k·s·u The comprehensive criterion Q constitutes k This allows for the identification of non-definite fault lines.

[0017] In one implementation, a single-pole grounding fault is determined to have occurred in the DC zone of the photovoltaic substation when the magnitudes of the positive and negative pole-to-ground voltages and the inter-pole voltages on the DC bus satisfy the following formula:

[0018]

[0019] In the formula: U P —Positive-to-ground voltage measurement modulus; U N —Measurement modulus of negative pole voltage to ground; U PN —Inter-electrode voltage measurement modulus; U PN· — Inter-electrode voltage rating; 0.4 and 0.8 — Setting coefficients.

[0020] In one embodiment, determining the faulty pole based on the relationship between the magnitudes of the positive and negative pole-to-ground voltages and the inter-pole voltages when a single-pole ground fault occurs includes:

[0021] When the single-pole ground fault occurs in the DC area of the photovoltaic power station, when the positive bus voltage to ground is less than the negative bus voltage to ground, it is determined that the positive pole fault occurs;

[0022] When the positive bus voltage to ground is greater than the negative bus voltage to ground, it is determined that the negative pole fault occurs.

[0023] In an embodiment, the correlation degree P of the transient component in the reference current of the DC area of the photovoltaic substation in the single-pole ground fault state and the transient voltage of the fault pole r·U And the correlation degree P of the transient component in the reference current and the transient component of the fault pole current of all lines r·k Determine whether a single-pole ground fault occurs at the bus, comprising:

[0024] Optionally, the fault pole current of one of the lines is taken as the reference current;

[0025] Calculate the correlation degree P of the transient component in the reference current and the transient voltage of the fault pole r·U ;

[0026] Calculate the correlation degree P of the transient component in the reference current and the transient component of the fault pole current of all lines r·k ;

[0027] When P r·U And all P r·k Satisfy the following formula, it is determined that the bus fault occurs:

[0028]

[0029] In the formula: ε V , ε I Is the allowable error value, generally 0.2-0.5; k=1-N.

[0030] In an embodiment, the correlation degree P of the current between the two ends of the line fault pole k·g·S·W And the correlation degree P of the fault pole current at the bus side of the line and the fault pole voltage k·s·u Determine the certain fault line, comprising:

[0031] Calculate the correlation degree P between the transient currents between the two ends of each line fault pole k·g·S·W ;

[0032] Calculate the correlation degree P between the transient current of the fault pole at the bus side of each line and the transient voltage of the fault pole k·s·u ;

[0033] The correlation degrees P k·s·u And P k·g·S·W , respectively, are:

[0034]

[0035] In the formula: P k·g·S·W —The correlation between the first and last ends of the fault pole on the k-th line, i k·g·s·j —The j-th sampling point of the current at the S-terminal of the fault pole of the k-th line; i k·g·w·j —The j-th sampling point of the fault pole W-terminal current of the k-th line; P k·s·u —The correlation between the current at the S terminal of the fault pole and the voltage of the fault pole in the kth line;

[0036] If P of all lines k·s·u and P k·g·S·W If only one line satisfies the following formula in terms of correlation, then that line is considered a faulty line:

[0037]

[0038] In the formula, ε V ε I The allowable error value is generally taken as 0.2 to 0.5; k = 1 to N.

[0039] In one implementation, the correlation P between the positive and negative currents at the beginning of the line is... k·s·+- The correlation between barrier current and fault voltage P k·s·u The comprehensive criterion Q constitutes k Identify non-definite fault lines, including:

[0040] Calculate the correlation P between the positive and negative currents at the beginning of each line. k·· ;

[0041] Calculate the correlation P between the fault-transient current and fault-transient voltage on the bus side of each line. k·s·u ;

[0042] Through correlation P k·s·+- and correlation P k·s·u Calculate the comprehensive criterion Q for each line. k ;

[0043] Q k The line corresponding to the minimum value is the faulty line, and the judgment ends.

[0044] In one implementation, the correlation P between the positive and negative currents at the beginning of the line is... k·s·+- The comprehensive criterion Qk is:

[0045]

[0046] In the formula: P k·s·+- —The correlation between the positive and negative transient currents at the beginning of the k-th line; Q k —Comprehensive criteria for the k-th route; ik·s·+·j — the jth sampling value of the positive electrode current of the kth line at the S end; i k·s·+·j — the jth sampling value of the negative electrode current of the kth line at the S end; i k·+·avg — the current sampling value of the kth line 5 ms before the positive electrode fault; i k·-·avg — the current sampling value of the kth line 5 ms before the negative electrode fault.

[0047] In another aspect, the application also provides a photovoltaic substation DC area monopolar grounding fault positioning device, which comprises:

[0048] a monitoring module for monitoring the modulus of the positive and negative electrode-to-ground voltage and the inter-electrode voltage of the photovoltaic substation DC area bus;

[0049] a grounding fault state judgment module for judging the monopolar grounding fault state of the photovoltaic substation DC area according to the modulus of the positive and negative electrode-to-ground voltage and the inter-electrode voltage;

[0050] a fault electrode judgment module for judging the fault electrode according to the relationship between the modulus of the positive and negative electrode-to-ground voltage and the inter-electrode voltage when the monopolar grounding fault occurs;

[0051] a fault line judgment module for realizing the positioning of the monopolar grounding fault according to the plurality of correlation degree characteristics between the transient current and voltage of each interval fault electrode when the monopolar grounding fault of the photovoltaic substation DC area occurs, and judging the fault line.

[0052] In an embodiment, the fault line judgment module comprises:

[0053] a bus monopolar grounding fault judgment module for judging whether the bus monopolar grounding fault occurs by the correlation degree P r·U between the transient component in the reference current and the transient voltage of the fault electrode and the correlation degree P r·k between the transient component in the reference current and the transient component of the current of all line fault electrodes when the photovoltaic substation DC area is in the monopolar grounding fault state;

[0054] a deterministic fault line judgment module for judging the deterministic fault line by the correlation degree P k·g·S·W between the current at both ends of the line fault electrode and the correlation degree P k·s·u between the fault electrode current and the fault electrode voltage at the bus side of the line;

[0055] a non-ambiguous fault line judgment module for judging the non-ambiguous fault line by the comprehensive criterion Qk composed of the correlation degree P k·s·+- between the positive and negative electrode currents at the head end of the line and the correlation degree P k·s·u between the fault electrode current and the fault electrode voltage.

[0056] Compared with the prior art, the application has the advantages of:

[0057] The application provides a photovoltaic substation DC area single-pole grounding fault positioning method based on multi-transient correlation degree calculation. The application calculates multiple correlation degrees of the first and last ends of each line, the positive and negative poles, and the positive and negative pole voltages, and accurately determines the fault position according to the correlation degree relationship when a single-pole grounding fault occurs at different positions in the photovoltaic substation DC area. The application is not affected by factors such as the transition resistance of the fault point, the structure of the photovoltaic substation, the length of the line, and the number of lines, and has excellent positioning performance. BRIEF DESCRIPTION OF DRAWINGS

[0058] The accompanying drawings are part of the present application and serve to provide a further understanding of the present application, and the schematic embodiments of the present application and the descriptions thereof serve to explain the present application but do not constitute an improper limitation on the present application. Obviously, the accompanying drawings in the following description are only some embodiments, and other drawings can be obtained by those skilled in the art without creative labor.

[0059] In the drawings:

[0060] Figure 1 A photovoltaic substation DC area single-pole grounding fault positioning method and device flowchart are provided for an embodiment of the present application.

[0061] Figure 2 A large photovoltaic substation DC area structure and installation position diagram of current transformers and voltage transformers are provided for an embodiment of the present application.

[0062] Figure 3 Voltage and current waveforms of each detection point when a single-pole grounding fault occurs in the positive pole of the bus (wherein, Figure 3-1 a bus positive pole fault voltage waveform, Figure 3-2 a bus positive pole fault L1 current waveform, Figure 3-3 a bus positive pole fault L2 current waveform, Figure 3-4 a bus positive pole fault L3 current waveform, Figure 3 a bus positive pole fault L4 current waveform) are provided.

[0063] Figure 4 Voltage and current waveforms of each detection point when a single-pole grounding fault occurs in the positive pole of the line L1 (wherein, Figure 4-1 a line L1 positive pole fault voltage waveform, Figure 4-2 a line L1 positive pole fault L1 current waveform, Figure 4-3 a line L1 positive pole fault L2 current waveform, Figure 4-4 a line L1 positive pole fault L3 current waveform, Figure 4 a line L1 positive pole fault L4 current waveform).

[0064] It should be noted that these drawings and written descriptions are not intended to limit the scope of the inventive concept in any way, but to illustrate the inventive concept to those skilled in the art by referring to specific embodiments. Embodiments

[0065] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments will be described clearly and completely below with reference to the drawings in the embodiments of the present application. The following embodiments are used to illustrate the present application, but not to limit the scope of the present application.

[0066] Reference Figure 1 The present embodiment provides a flow chart of a DC area single-pole grounding fault positioning method for a photovoltaic power station based on multi-correlation degree calculation. The method is based on multi-transient correlation degree calculation and specifically includes the following steps:

[0067] Step S100: Monitor the positive and negative pole-to-ground voltage and the inter-pole voltage of the DC area bus of the photovoltaic substation.

[0068] Specifically, each line in the DC area of the photovoltaic substation is numbered 1~N; where N is the total number of lines; the side connected to the bus of each line is called the first end (S), and the other side is called the last end (W); current transformers are installed at the first and last ends of the positive and negative poles of each line, and the installation direction is unified as the current flowing from the bus to the line being positive; voltage measurement transformers are installed on the positive and negative poles of the bus; the positive pole-to-ground voltage module value U P , the negative pole-to-ground voltage module value U N and the inter-pole voltage module value U PN on the DC bus are measured.

[0069] Step S200: Determine the single-pole grounding fault state of the DC area of the photovoltaic substation according to the positive and negative pole-to-ground voltage and the inter-pole voltage module values.

[0070] Specifically, the positive pole-to-ground voltage module value U P , the negative pole-to-ground voltage module value U N and the inter-pole voltage module value U PN on the DC bus are measured; by the changes of the positive and negative pole-to-ground voltage module values and the inter-pole voltage module value on the DC bus of the photovoltaic substation, it is determined whether a single-pole grounding fault occurs in the DC area of the photovoltaic substation.

[0071] Further, when the positive and negative pole-to-ground voltage and the inter-pole voltage on the DC bus satisfy formula (1), it is determined that a single-pole grounding fault occurs in the DC area of the photovoltaic substation:

[0072]

[0073] In the formula, UP —positive electrode-to-ground voltage measurement modulus value;

[0074] U N —negative electrode-to-ground voltage measurement modulus value;

[0075] U PN —inter-electrode voltage measurement modulus value;

[0076] U PN· —inter-electrode voltage rated value;

[0077] 0.4 and 0.8—setting coefficient.

[0078] Step S300: judging the fault electrode according to the modulus values of the positive electrode-to-ground voltage, the negative electrode-to-ground voltage and the inter-electrode voltage when a single-pole earth fault occurs;

[0079] In the embodiment, the judging the fault electrode according to the modulus values of the positive electrode-to-ground voltage, the negative electrode-to-ground voltage and the inter-electrode voltage when a single-pole earth fault occurs includes:

[0080] When a single-pole earth fault occurs in the DC area of the photovoltaic power station, when the modulus value of the positive electrode-to-ground voltage of the bus is less than the modulus value of the negative electrode-to-ground voltage of the bus, it is judged that the positive electrode is faulty;

[0081] When the modulus value of the positive electrode-to-ground voltage of the bus is greater than the modulus value of the negative electrode-to-ground voltage of the bus, it is judged that the negative electrode is faulty.

[0082] Step S400: positioning the single-pole earth fault and judging the fault line according to the multiple correlation degree characteristics between the transient currents and voltages of each section when a single-pole earth fault occurs in the DC area of the photovoltaic substation.

[0083] In the embodiment, the positioning the single-pole earth fault and judging the fault line according to the correlation degree characteristics of the fault electrode and the transient currents and voltages of each section when a single-pole earth fault occurs in the DC area of the photovoltaic substation includes:

[0084] Step S410: judging whether a single-pole earth fault of the bus occurs by the correlation degree P r·U of the transient component in the reference current and the transient voltage of the fault electrode and the correlation degree P r·k of the transient component in the reference current and the transient component of the fault electrode current of all lines in the state of the single-pole earth fault;

[0085] In the embodiment, the judging whether a single-pole earth fault of the bus occurs includes:

[0086] Optionally, the fault electrode current of one line is taken as the reference current;

[0087] The correlation degree Pr·U ;

[0088] Calculate the correlation degree P of the transient component in the reference current and all line fault pole transient current components r·k ;

[0089] When P r·U and all P r·k satisfy the following formula, it is judged as bus fault:

[0090]

[0091] In the formula: ε V , ε I is the allowable error value, generally 0.2-0.5; k=1-N.

[0092] Specifically, one of the line fault pole currents is selected as the reference current, and the correlation degree P of the transient component in the reference current and the fault pole transient voltage is calculated according to formula (2) r·U , the correlation degree P of the transient component in the reference current and all line fault pole current transient components r·k When P r·U and all correlation degrees P r·k satisfy formula (3), it is judged as bus fault, and the judgment conclusion is given.

[0093] Otherwise, it is judged as line fault, and the following steps are executed to judge the line where the fault is located.

[0094]

[0095] In the formula: P r·U is the correlation degree of the reference current and the fault pole transient voltage; r is the optional line number, and the value range is [1, N];

[0096] M is the sampling point number, generally 10ms sampling point number, including 5ms before fault and 5ms after fault; i r·g is the reference current sampling point; i r·g·j is the jth sampling value of the reference current; i r·g·avg is the average value of the reference current 5ms before fault; u g·j is the jth sampling value of the fault pole voltage; u g·avg is the average value of the fault pole voltage 5ms before fault; P r·k is the correlation degree of the reference current and the kth line fault pole transient current; i k·g·j is the jth sampling point of the kth line fault pole current; i k·g·avg is the average value of the kth line fault pole current 5ms before fault.

[0097]

[0098] wherein ε V , ε I is an allowable error value, generally taken as.2-.5; k=1-N.

[0099] Step S420: judging the certain fault line through the correlation degree P k·g·S·W of the fault polar current and the fault polar voltage at the line bus side k·s·u ;

[0100] In the embodiments of the present application, judging the certain fault line specifically comprises:

[0101] calculating the correlation degree P k·g·S·W between the transient currents at both ends of each line fault polar;

[0102] calculating the correlation degree P k·s·u between the transient current at the bus side of each line fault polar and the transient voltage at the fault polar;

[0103] The correlation degrees P k·s·u and P k·g·S·W are respectively represented as:

[0104]

[0105] wherein P k·g·S·W is the correlation degree between the first and the last ends of the kth line fault polar i k·g·s·j is the jth sampling point of the current at the S end of the kth line fault polar; i k·g·w·j is the jth sampling point of the current at the W end of the kth line fault polar; P k·s·u is the correlation degree between the current at the S end of the kth line fault polar and the voltage at the fault polar;

[0106] If the correlation degrees P k·s·u and P k·g·S·W of all lines only one line satisfies the following formula, the line is the fault line:

[0107]

[0108] wherein ε V , ε I is an allowable error value, generally taken as.2-.5; k=1-N.

[0109] Specifically, the correlation degree P k·g·S·W between the transient currents at both ends of each line fault polar is calculated, as shown in formula (4), and the correlation degree P k·s·u between the transient current at the bus side of each line fault polar and the transient voltage at the fault polar is calculated; if the correlation degrees P k·s·u and P k·g·S·WIf only one line satisfies equation (5), then that line is the faulty line, and a judgment conclusion is given; if there is no line or multiple lines that satisfy equation (5), then step S430 is executed to continue to determine the fault location.

[0110] Step S430: Analyze the correlation P between the positive and negative currents at the beginning of the line. k·· The correlation between barrier current and fault voltage P k·s·u The comprehensive criterion Q constitutes k This allows for the identification of non-definite fault lines.

[0111] In this embodiment of the application, the correlation P between the positive and negative currents at the beginning of the line is... k·· The correlation between barrier current and fault voltage P k·· The comprehensive criterion Q constitutes k Identify non-definite fault lines, including:

[0112] Calculate the correlation P between the positive and negative currents at the beginning of each line. k·s·+- ;

[0113] Calculate the correlation P between the fault-transient current and fault-transient voltage on the bus side of each line. k·s·u ;

[0114] Through correlation P k·s·+- and correlation P k·s·u Calculate the comprehensive criterion Q for each line. k ;

[0115] Q k The line corresponding to the minimum value is the faulty line, and the judgment ends.

[0116] Furthermore, the correlation P between the transient currents at the positive and negative terminals of each line was calculated. k·s·+- and comprehensive criterion Q k As shown in equation (6);

[0117]

[0118] In the formula: P k·s·+- —The correlation between the positive and negative transient currents at the beginning of the k-th line; Q k —Comprehensive criteria for the k-th route; i k·s·+·j —The j-th sampled value of the positive current at terminal S of the k-th line; i k·s·+·j —The j-th sampled value of the negative electrode current at the S terminal of the k-th line; i k·+·avg —The current sampling value of the k-th line 5ms before the positive pole fault; i k·-·avg — Current sampling value 5ms before the negative pole fault of the kth line.

[0119] Qk The line corresponding to the minimum value is the faulty line, and a judgment conclusion is given.

[0120] refer to Figure 2 , Figure 2 The diagram shown depicts the DC combiner area structure of a photovoltaic power station. The rated voltage on the DC side is...

[0121] ±1000V; sampling frequency is 24kHz Z The photovoltaic power station has four lines, L1 to L4. A single-pole grounding fault is considered to have occurred when the voltage drop between the positive or negative pole and ground exceeds 20% of the rated voltage.

[0122] When a single-pole ground fault occurs at the positive terminal of the busbar, the voltage and waveform at each monitoring point are as follows: Figure 3 As shown in the figure, it is clear that the fault location cannot be determined solely by the magnitude and direction of the transient current change; it requires considering the relationships between various correlations of transient voltages and currents in each line to pinpoint the fault area. The positive current of L3 is selected as the reference current; ε V ε I The values ​​were set to 0.3 and 0.4 respectively; the calculated correlation coefficients are shown in Table 1.

[0123] Table 1. Calculation values ​​of correlation degree for each line when a single-pole ground fault occurs at the positive pole of the busbar.

[0124]

[0125] Table 1 clearly shows that the busbar is faulty.

[0126] like Figure 2 As shown, when a single-pole ground fault occurs at the positive terminal of line L1, the voltage and waveform at each monitoring point are as follows: Figure 4 As shown in the figure, it is clear that the fault location cannot be determined solely by the magnitude and direction of the transient current change; it requires considering the relationships between various correlations of transient voltages and currents in each line to pinpoint the fault area. The positive current of L3 is selected as the reference current; ε V ε I The values ​​were set to 0.3 and 0.4 respectively; the calculated correlation coefficients are shown in Table 2.

[0127] Table 2. Calculation values ​​of correlation for each line when a single-pole grounding fault occurs at the positive pole of line L1.

[0128]

[0129]

[0130] As shown in Table 2, through P r·U P r·k Its formula (3) can determine that it is not a busbar fault;

[0131] By P k·s·u , P k·g·S·W and its formula (5) can determine that the fault occurs in the line L1; By P k·s·+- , Q k and step S430 can also determine that the fault occurs in the line L1; However, the determination of step S420 is more definite than that of step S430; However, step S430 can not install a current transformer at the end of each line W, facilitating application.

[0132] The application can accurately realize the positioning of the single-pole grounding fault according to the correlation degree characteristics of the transient currents and voltages between each interval when the single-pole grounding fault occurs in the direct-current area of the photovoltaic substation, and can accurately determine the fault line. Through different positions, different poles and different transition resistances of different lines, the application can determine the fault position.

[0133] The application also provides a single-pole grounding fault positioning device for a direct-current area of a photovoltaic substation.

[0134] A monitoring module is configured to monitor the module values of the positive and negative pole-to-ground voltages and the inter-pole voltage of the direct-current area of the photovoltaic substation.

[0135] A grounding fault state judgment module is configured to determine the single-pole grounding fault state of the direct-current area of the photovoltaic substation according to the module values of the positive and negative pole-to-ground voltages and the inter-pole voltage.

[0136] A fault pole judgment module is configured to determine the fault pole according to the relationship between the module values of the positive and negative pole-to-ground voltages and the inter-pole voltage when the single-pole grounding fault occurs.

[0137] A fault line judgment module is configured to realize the positioning of the single-pole grounding fault according to the multiple correlation degree characteristics between the transient currents and voltages of each interval fault pole when the single-pole grounding fault occurs in the direct-current area of the photovoltaic substation, and determine the fault line.

[0138] In the embodiment of the application, the fault line judgment module comprises:

[0139] A bus single-pole grounding fault judgment module is configured to determine whether the bus single-pole grounding fault occurs by the correlation degree P r·U between the transient component in the reference current and the transient voltage of the fault pole and the correlation degree P r·k between the transient component in the reference current and the transient component of the fault pole current of all lines in the reference current of the direct-current area of the photovoltaic substation in the single-pole grounding fault state.

[0140] A deterministic fault line judgment module is configured to determine the fault line by the correlation degree P k·g·s·w between the currents at both ends of the line fault pole and the correlation degree P k·s·u between the fault pole current of the line bus side and the fault pole voltage., determine the deterministic fault line;

[0141] The non-deterministic fault line determination module is configured to determine the non-deterministic fault line by using the correlation degree P of the positive and negative polar currents at the line head k·s·+- and the correlation degree P of the fault polar current and the fault polar voltage k·s·u The comprehensive criterion Q is composed of the above two correlation degrees k , determine the non-deterministic fault line.

[0142] It is to be noted that the photovoltaic substation DC area monopolar grounding fault positioning device and the photovoltaic substation DC area monopolar grounding fault positioning method provided by the above embodiment belong to the same concept, and the implementation process is detailed in the photovoltaic substation DC area monopolar grounding fault positioning method. Here, it will not be repeated.

[0143] In addition, those skilled in the art can understand that although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments also means that it is within the protection scope of the present application and forms different embodiments. For example, in the above embodiments, those skilled in the art can use in a combined manner according to the known technical solutions and the technical problems to be solved by the present application.

[0144] The above is only the preferred embodiment of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above-mentioned technical content without departing from the scope of the technical solution of the present application, and any simple modification, equivalent change and modification of the above-mentioned embodiments according to the technical essence of the present application are still within the scope of the present application.

Claims

1. A method for locating a single-pole ground fault in a DC area of a photovoltaic substation, characterized in that: The method comprises the following steps: Monitor the positive and negative ground voltage and the inter-electrode voltage of the DC bus of the photovoltaic substation; Determine the single-pole grounding fault state of the DC area of the photovoltaic substation according to the positive and negative ground voltage and the inter-electrode voltage; Determine the fault pole according to the relationship between the positive and negative ground voltage and the inter-electrode voltage when a single-pole grounding fault occurs; Locate the single-pole grounding fault, determine the fault line, by using multiple correlation degree characteristics between the transient current and voltage of each interval fault pole when a single-pole grounding fault occurs in the DC area of the photovoltaic substation, comprising: The correlation degree P of the transient component in the reference current of the DC area of the photovoltaic substation in a single-pole grounding fault state and the transient voltage of the fault pole r·U And the correlation degree P of the transient component in the reference current and the transient component of the current of all line fault poles r·k Whether the bus is in single-pole grounding fault; By the correlation P of the current across the faulted pole k·g·S·W And the correlation P of the faulted pole current and the faulted pole voltage at the line bus side k·s·u , the deterministic faulted line is determined; By the correlation degree P of the positive and negative electrode current of the line head k·s·+- And the correlation degree P of the fault electrode current and the fault electrode voltage k·s·u The comprehensive criterion Q composed of k , The non-clear fault line is judged out; When the positive and negative ground voltage and the inter-electrode voltage on the DC bus satisfy the following formula, it is determined that a single-pole grounding fault occurs in the DC area of the photovoltaic substation: where: U P — positive pole to ground voltage measurement modulus; U N — negative pole to ground voltage measurement modulus; U PN — inter-pole voltage measurement modulus; U PN·e — inter-pole voltage rating; 0.4 and 0.8 — setting coefficients.

2. The method of claim 1, wherein: The determination of the fault pole according to the relationship between the positive and negative ground voltage and the inter-electrode voltage when a single-pole grounding fault occurs comprises: When a single-pole grounding fault occurs in the DC area of the photovoltaic substation, when the positive ground voltage is less than the negative ground voltage, it is determined that the positive pole is faulty; When the positive ground voltage is greater than the negative ground voltage, it is determined that the negative pole is faulty.

3. The method of claim 1, wherein: Correlation degree P of transient component in reference current of DC area of photovoltaic substation under single pole grounding fault state and transient voltage of fault pole r·U Correlation degree P of transient component in reference current and transient component of all line fault pole currents r·k , judging whether single pole grounding fault of bus occurs, comprising: Optionally, the fault pole current of one of the lines is used as a reference current; Calculate the correlation degree between the transient component in the reference current and the transient voltage of the fault pole; Calculate the correlation degree between the transient component in the reference current and the transient component of the fault pole current of all lines; When P r·U With all P r.k When the following equation is satisfied, the bus fault is determined: wherein: ε V , ε I is the allowable error value, generally taken as 0.2-0.5; k = 1-N.

4. The method of claim 1, wherein: the correlation degree P of the current through the line fault pole k.g.S.W and the correlation degree P of the fault pole current and the fault pole voltage at the line bus side k·s·u determining the deterministic fault line, comprising: Calculate the correlation degree between the transient currents at both ends of each line fault pole; Calculate the correlation degree between the transient current of the fault pole at the bus side of each line and the transient voltage of the fault pole; The correlation degree P k·s·u and P k·g·S·W , respectively, are given by: wherein: i k·g·s·j — the jth sampling point of the S-terminal current of the kth line fault pole; i k·g·w·j — the jth sampling point of the W-terminal current of the kth line fault pole; i k·g·avg — the average value of the kth line fault pole current 5 ms before the fault; u g·j — the jth sampling value of the fault pole voltage; u g·avg — the average value of the fault pole voltage 5 ms before the fault; If P k·s·u and P k·g·S·W of all lines satisfy the following formula, the line is the fault line: In the formula, ε V , ε I is an allowable error value, generally taken as 0.2-0.5; k = 1-N.

5. The method of claim 1, wherein: The correlation degree P of the positive and negative polar currents at the line head k·s·+- And the correlation degree P of the fault polar current and the fault polar voltage k·s·u The comprehensive criterion Q composed of the above k The non-ambiguous fault line is determined, comprising: Calculate the correlation degree of the positive and negative currents at the head of each line; Calculate the correlation degree between the transient current of the fault pole at the bus side of each line and the transient voltage of the fault pole; By the correlation P k·s·+- and the correlation P k·s·u Calculating the comprehensive criterion Q of each line k ; Q k The line corresponding to the minimum value is the fault line, and the judgment ends.

6. The method of claim 5, wherein: The correlation degree P of the positive and negative currents of the line end k·s·+- and the comprehensive criterion Q k is: In the formula: i k·s·+·j — the jth sampling value of the positive electrode current at the S end of the kth line; i k·s·-·j — the jth sampling value of the negative electrode current at the S end of the kth line; i k·+·avg — the current sampling value of the kth line 5 ms before the positive electrode fault; i k·-·avg — the current sampling value of the kth line 5 ms before the negative electrode fault; P k·s·u — the correlation degree of the S end current and the fault pole voltage of the kth line.

7. A photovoltaic substation DC area single pole ground fault locating device characterized by: The device comprises: A monitoring module for monitoring the positive and negative ground voltage and the inter-electrode voltage of the DC bus of the photovoltaic substation; A grounding fault state determination module for determining the single-pole grounding fault state of the DC area of the photovoltaic substation according to the positive and negative ground voltage and the inter-electrode voltage; A fault pole determination module for determining the fault pole according to the relationship between the positive and negative ground voltage and the inter-electrode voltage when a single-pole grounding fault occurs; A fault line determination module, comprising: The bus single-pole grounding fault judgment module is configured to judge whether the bus single-pole grounding fault occurs by the correlation degree P of the transient component in the reference current of the photovoltaic substation DC area in the single-pole grounding fault state and the transient voltage of the fault pole r·U and the correlation degree P of the transient component in the reference current and the transient component of the current of all line fault poles r·k , to judge whether the bus single-pole grounding fault occurs. A deterministic fault line judgment module is configured to determine a deterministic fault line by correlation degree P of current at both ends of the fault pole k·g·S·W and correlation degree P of fault pole current and fault pole voltage at the line bus side k·s·u . The non-definite fault line judgment module is used to determine the correlation P between the positive and negative currents at the beginning of the line. k·s·+- The correlation between barrier current and fault voltage P k·s·u The comprehensive criterion Q constitutes k This allows for the identification of non-definite fault lines. When the positive and negative ground voltage and the inter-electrode voltage on the DC bus satisfy the following formula, it is determined that a single-pole grounding fault occurs in the DC area of the photovoltaic substation: where: U P — positive pole to ground voltage measurement modulus; U N — negative pole to ground voltage measurement modulus; U PN — inter-pole voltage measurement modulus; U PN·e — inter-pole voltage rating; 0.4 and 0.8 — setting coefficients.

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