Single-phase high-resistance fault line selection method in resonant grounding system based on transition resistance

Abstract

The invention belongs to the technical field of relay protection of power system distribution network, and provides a single-phase high-resistance fault line selection method for a resonant grounding system based on transition resistance, comprising: S1, constructing a single-phase high-resistance fault detection start criterion; S2, respectively obtaining the transient components of each feeder current and bus voltage; S3, fitting the linear relationship between the integrals of the transient components of voltage and current and calculating the resistance; the invention respectively performs steady-state and transient analysis on a single-phase high-resistance fault occurring in a resonant grounding mode, uses theoretical analysis to find out why high-resistance fault detection cannot be achieved by only using the steady-state components of each feeder zero-sequence current and bus zero-sequence voltage, and then extracts the bus zero-sequence voltage and the transient components of each feeder zero-sequence current, and analyzes that the integral value of the transient part of the zero-sequence current of the fault feeder is linearly correlated with the transient sub-part of the bus zero-sequence voltage and its integral, thereby laying a foundation for achieving single-phase high-resistance fault detection.

Description

Technical Field

[0001] The invention belongs to the technical field of relay protection of power system distribution network, in particular to single-phase high-resistance fault line selection in a resonant grounding system based on transition resistance. Background Art

[0002] Most of my country's medium and low voltage distribution networks use resonant grounding, which can reduce the size of single-phase grounding fault current and effectively limit the duration of the arc when a fault occurs, thereby reducing damage to system equipment and safety hazards caused by faults.

[0003] However, since the fault characteristics of a single-phase high-resistance fault in the distribution network are originally relatively weak and the fault hazards are very serious, when the system adopts resonant grounding, the fault current will be smaller and the fault characteristics will be less obvious after a single-phase high-resistance fault. Traditional protection devices are prone to failure, resulting in safety hazards in system operation.

[0004] To this end, those skilled in the art have proposed a single-phase high-resistance fault line selection method for a resonant grounding system based on transition resistance to solve the problems raised by the background technology, which is crucial to improving power supply reliability and safe operation of the power system. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a single-phase high-resistance fault line selection method for a resonant grounding system based on transition resistance, so as to solve the problem that when a single-phase high-resistance fault occurs in the distribution network in the prior art, the fault characteristics are originally relatively weak and the fault hazards are very serious. When the system adopts a resonant grounding method, the fault current after the single-phase high-resistance fault is smaller and the fault characteristics are less obvious. The traditional protection device is prone to failure, which leads to safety hazards in the operation of the system.

[0006] The method for selecting a single-phase high-resistance fault line in a resonant grounding system based on transition resistance includes the following steps:

[0007] Step 1: Construct a single-phase high-resistance fault detection start-up criterion, collect the bus zero-sequence voltage, and start the single-phase high-resistance fault line selection method when the effective value of the bus zero-sequence voltage is greater than 0.15 times the system voltage;

[0008] Step 2: Obtain the transient components of each feeder current and bus voltage respectively, obtain the bus zero-sequence voltage and each feeder zero-sequence current signal of the 20 power frequency cycle window length after the fault moment, and subtract the waveform data of the corresponding first 10 cycles from the waveform of the last 10 cycles to obtain several transient components;

[0009] Step 3: Fit the linear relationship between the integrals of the transient components of voltage and current and calculate the resistance. Use the area method to estimate the integral results of each transient component to obtain the linear relationship between them, and use the least squares method to fit the linear relationship to calculate the resistance.

[0010] Step 4: Use the transition resistance value to construct a single-phase high-resistance fault detection criterion, calculate the transition resistance value of each feeder, and realize single-phase high-resistance fault detection by comparing the difference of the transition resistance values ​​of each feeder;

[0011] Step 5: Finally, complete the line selection for single-phase high-resistance fault in the resonant grounding system.

[0012] Preferably, the specific formula for calculating each transient component in step 2 is as follows:

[0013]

[0014] In the formula, is the value corresponding to the kth sampling point of the transient component of the bus zero-sequence voltage, For the j The transient component of zero-sequence current of feeder k The value corresponding to the sampling point; N represents the number of sampling points in a sampling period; and Respectively represent the bus zero sequence voltage and The value of the sampling point; and Respectively represent j Feeder zero sequence current and The value of the sampling point.

[0015] Preferably, the integration results of each transient component calculated by the area method in step 3 are used to obtain a linear relationship between them, and the linear relationship is fitted by the least squares method. The specific steps for calculating the resistance are as follows:

[0016] Step 3.1: First, the specific calculation process of the integral results of each transient component calculated using the area method is as follows:

[0017]

[0018] In the formula, and They represent the busbar zero-sequence voltage transient component and the j The integral value of the transient component of the zero-sequence current of the feeder; and Respectively represent and The time corresponding to each sampling point;

[0019] Step 3.2: Obtain the expressions of the bus zero-sequence voltage and each feeder zero-sequence current when a single-phase high-resistance fault occurs in the resonant grounding system, extract its transient component, and then obtain the relationship between the transient component integral value of each feeder zero-sequence current and the bus zero-sequence voltage transient amount and its integral through the analysis in the working principle 3 of the present invention, which can be expressed as:

[0020]

[0021] In the formula, Indicates j The capacitance of the feeder to ground; R Indicates the size of resistance;

[0022] For the convenience of calculation, let , , , then the above formula can be simplified to:

[0023]

[0024] Step 3.3: Use the difference between the left and right sides of the above equation to define the overall error of each feeder as:

[0025]

[0026] In the formula, Indicates j The overall error of the feeder; , and They represent the bus zero-sequence voltage transient component, the bus zero-sequence voltage transient component integral value and the j The integral value of the transient component of the zero-sequence current of the feeder k The value corresponding to each sampling point;

[0027] Then, the transient relationship of each current and voltage transient component is fitted using the least squares method through the formula in step 3.2. First, the partial derivative of 1 / R is calculated:

[0028]

[0029] Simplifying, we can get the expression of 1 / R as:

[0030] .

[0031] Preferably, the specific process of realizing single-phase high-resistance fault detection by comparing the difference in transition resistance values ​​of each feeder in step 4 is as follows:

[0032] Use the formula in step 3.3 to calculate the estimated value of 1 / R, and then calculate the transition resistance R f The value is as follows:

[0033]

[0034] In the fault line, R f Represents the actual transition resistance; in a healthy circuit, R f tends to infinity, the coefficient 1 / R tends to 0; finally, if the transition resistance calculated for a certain line R f If the value of is significantly lower than that of all other lines, the line can be determined to be a faulty line, thus realizing single-phase high-resistance fault detection.

[0035] A single-phase high-resistance fault detection device for a resonant grounding system based on transition resistance, comprising:

[0036] The signal acquisition module is responsible for real-time acquisition of the busbar zero-sequence voltage and the zero-sequence current signals of each feeder; this module must have high-precision sampling capabilities to ensure that the acquired signals are accurate;

[0037] The fault start judgment module determines whether to start the single-phase high-resistance fault detection process according to the collected bus zero-sequence voltage effective value; when the bus zero-sequence voltage effective value is greater than 0.15 times the system voltage, the detection is started;

[0038] The transient component extraction module extracts the bus zero-sequence voltage and each feeder zero-sequence current waveform within 20 power frequency cycles after the fault moment after the fault is detected, and obtains the transient component by subtracting the waveform of the first 10 cycles from the waveform of the last 10 cycles;

[0039] The transient component integration and linear relationship fitting module uses the area method to calculate the integral results of each transient component, and finds the linear relationship between the busbar zero-sequence voltage transient component and the zero-sequence current transient component of each feeder; the least squares method is used to fit the linear relationship to calculate the transition resistance value of each feeder;

[0040] The fault detection and location module compares the transition resistance values ​​of each feeder to determine which feeder has a significantly lower transition resistance value than other feeders, thereby determining the fault line;

[0041] Display and alarm module, when a single-phase high-resistance fault is detected, the fault information (such as fault feeder number, fault time, etc.) is displayed on the display screen, and an audible and visual alarm signal is issued;

[0042] Communication module, which communicates with the host computer or other intelligent devices, uploads fault detection results, and receives control instructions;

[0043] The data storage module stores the collected signal data, calculation results and fault detection records for subsequent analysis.

[0044] A processor is configured to execute the above-mentioned single-phase high-resistance fault line selection method in a resonant grounding system based on transition resistance.

[0045] A machine-readable storage medium stores instructions, which, when executed by a processor, configure the processor to execute the above-mentioned single-phase high-resistance fault line selection method for a resonant grounding system based on transition resistance.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. Analysis of single-phase high-resistance fault characteristics: Steady-state and transient analyses are performed on single-phase high-resistance faults occurring under resonant grounding mode. Theoretical analysis is used to find out why high-resistance fault detection cannot be achieved using only the steady-state components of each feeder zero-sequence current and bus zero-sequence voltage. Then, by extracting the transient components of the bus zero-sequence voltage and each feeder zero-sequence current, it is analyzed that the integral value of the transient part of the zero-sequence current of the faulty feeder is linearly correlated with the transient part of the bus zero-sequence voltage and its integral, and the proportional coefficients are the derivatives of the zero-sequence capacitance to ground and the grounding resistance of the line, respectively, thus laying the foundation for the detection of single-phase high-resistance faults.

[0048] 2. High-resistance fault detection criteria: First, collect the bus zero-sequence voltage. When its effective value is greater than 0.15 times the system voltage, start the single-phase high-resistance fault line selection method. Then, collect the bus zero-sequence voltage and each feeder zero-sequence current waveform within 20 cycles after the fault, and subtract the waveform data of the corresponding first 10 cycles from the waveform of the last 10 cycles to obtain several voltage and current transient components. Secondly, use the linear relationship between the voltage and current transient components and use the least squares method to estimate the value of the transition resistance of each feeder. Finally, through the difference in the transition resistance of each feeder, single-phase high-resistance fault detection can be achieved. The criterion calculation is simple, and it is not affected by the transition resistance, so the reliability is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a flow chart of the single-phase high-resistance fault line selection method of the present invention;

[0050] Figure 2 It is a schematic diagram of the zero-sequence equivalent network of the arc suppression coil grounding system in the present invention;

[0051] Figure 3 It is a schematic diagram of zero-sequence current waveforms of a faulty feeder and a sound feeder when a single-phase high-resistance fault occurs in the resonant grounding system of the present invention;

[0052] Figure 4 This is a schematic diagram of a simulation model of a 10kV resonant grounded distribution network according to an embodiment of the present invention;

[0053] Figure 5 The schematic diagram is a schematic diagram of the transient components of the zero-sequence voltage of the busbar and the zero-sequence current of each feeder when a single-phase grounding fault occurs through a 2000Ω transition resistor at the head end of line 15 6 km away from the busbar according to an embodiment of the present invention. DETAILED DESCRIPTION

[0054] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0055] The present invention provides a single-phase high-resistance fault line selection method for a resonant grounding system based on transition resistance, such as Figure 1 As shown, the specific steps include:

[0056] Step 1: Construct a single-phase high-resistance fault detection start-up criterion, collect the bus zero-sequence voltage, and start the single-phase high-resistance fault line selection method when the effective value of the bus zero-sequence voltage is greater than 0.15 times the system voltage;

[0057] Step 2: Obtain the transient components of each feeder current and bus voltage respectively, obtain the bus zero-sequence voltage and each feeder zero-sequence current signal of the 20 power frequency cycle window length after the fault moment, and subtract the waveform data of the corresponding first 10 cycles from the waveform of the last 10 cycles to obtain several transient components; the specific formula for calculating each transient component in step 2 is as follows:

[0058]

[0059] In the formula, is the value corresponding to the kth sampling point of the transient component of the bus zero-sequence voltage, For the j The transient component of zero-sequence current of feeder k The value corresponding to the sampling point; N represents the number of sampling points in a sampling period; and Respectively represent the bus zero sequence voltage and The value of the sampling point; and Respectively represent j Feeder zero sequence current and The value of the sampling point;

[0060] Step 3: Fit the linear relationship between the integrals of the transient components of voltage and current and calculate the resistance. Use the area method to estimate the integral results of each transient component, obtain the linear relationship between them, and use the least squares method to fit the linear relationship to calculate the resistance. The integral results of each transient component calculated by the area method in step 3 are used to obtain the linear relationship between them, and the least squares method is used to fit the linear relationship. The specific steps for calculating the resistance are as follows:

[0061] Step 3.1: First, the specific calculation process of the integral results of each transient component calculated using the area method is as follows:

[0062]

[0063] In the formula, and They represent the busbar zero-sequence voltage transient component and the j The integral value of the transient component of the zero-sequence current of the feeder; and Respectively represent and The time corresponding to each sampling point;

[0064] Step 3.2: Obtain the expressions of the bus zero-sequence voltage and each feeder zero-sequence current when a single-phase high-resistance fault occurs in the resonant grounding system, extract its transient component, and then obtain the relationship between the transient component integral value of each feeder zero-sequence current and the bus zero-sequence voltage transient amount and its integral through the analysis in the working principle 3 of the present invention, which can be expressed as:

[0065]

[0066] In the formula, Indicates j The capacitance of the feeder to ground; R Indicates the size of resistance;

[0067] For the convenience of calculation, let , , , then the above formula can be simplified to:

[0068]

[0069] Step 3.3: Use the difference between the left and right sides of the above equation to define the overall error of each feeder as:

[0070]

[0071] In the formula, Indicates j The overall error of the feeder; , and They represent the bus zero-sequence voltage transient component, the bus zero-sequence voltage transient component integral value and the j The integral value of the transient component of the zero-sequence current of the feeder k The value corresponding to each sampling point;

[0072] Then, the transient relationship of each current and voltage transient component is fitted using the least squares method through the formula in step 3.2. First, the partial derivative of 1 / R is calculated:

[0073]

[0074] Simplifying, we can get the expression of 1 / R as:

[0075] ;

[0076] Step 4: Use the transition resistance value to construct a single-phase high-resistance fault detection criterion, calculate the transition resistance value of each feeder, and realize single-phase high-resistance fault detection by comparing the difference in the transition resistance values ​​of each feeder; the specific process of realizing single-phase high-resistance fault detection by comparing the difference in the transition resistance values ​​of each feeder in step 4 is as follows:

[0077]

[0078] In the fault line, R f Represents the actual transition resistance; in a healthy circuit, R f tends to infinity, the coefficient 1 / R tends to 0; finally, if the transition resistance calculated for a certain line R f If the value of is significantly lower than that of all other lines, it can be determined that the line is a faulty line, thus realizing single-phase high-resistance fault detection;

[0079] Step 5: Finally, complete the line selection for single-phase high-resistance fault in the resonant grounding system.

[0080] Example

[0081] Use PSCAD to build Figure 4 The simulation model of the 10kV resonant grounded distribution network shown in the figure has 5 outgoing lines, among which: l 1. l 3 is a full overhead line, l 4. l 5 is the full cable line, l 2 is a mixed overhead and cable line. The length of each line has been clearly marked in the figure. The specific parameters of the line are shown in Table 1. In addition, m 1 to m5 represents the zero-sequence current transformer installed at the head end of each feeder. Assuming that the system operates with overcompensation, the overcompensation degree is 10%, the arc suppression coil inductance is 0.4779H, the resistance is 4.5040Ω, and a 0.5MW constant impedance load is used at the end of each feeder.

[0082] Table 1 System specific parameters

[0083]

[0084] Simulation Analysis

[0085] Assume that a single-phase grounding fault occurs through a 2000Ω transition resistor at the head end of line l5, 6 km away from the busbar, and the initial phase angle is 30° for analysis; the system sampling frequency f=10kHz, the simulation time is 1s, and the fault occurrence time is set to 0.08s.

[0086] Figure 1 The flowchart of the single-phase high-resistance fault line selection method for the resonant grounding system of the present invention is as follows. According to the method of the present invention, first, the zero-sequence current at the head end of each feeder and the zero-sequence voltage of the busbar within 20 power frequency cycles after the fault occurs are collected, and then the transient components obtained by subtracting the waveform data of the corresponding first 10 cycles from the waveform of the last 10 cycles are as follows: Figure 5 As shown; then Figure 5 After integrating the transient components of the zero-sequence voltage of the busbar and the zero-sequence current of each feeder, the least squares method is used to estimate the parameters contained in step 3.2, thereby obtaining the estimated value of the transition resistance of each feeder; the estimated value of the transition resistance is [15040000, 947470, 4501100, 43372, 1934], indicating that a single-phase high-resistance fault occurs in feeder l5, and high-resistance fault detection is accurately achieved.

[0087] To further demonstrate the reliability of this method, we used Figure 4 The topology shown was verified by multiple simulations under different fault locations, different noise backgrounds, and different fault initial phase angles.

[0088] use Figure 4 The 10 kV resonant grounding system topology shown in the figure is simulated for different fault locations, and the estimated results of the transition resistance of each feeder are shown in Table 2. Under the conditions of setting the grounding resistance to 2000 Ω, the fault starting phase angle to 0°, and the system overcompensation level to 10%, detailed simulation calculations are carried out for the six different fault locations listed in Table 2. Among them, L is the distance from the fault point to the head end of the busbar.

[0089] Table 2 Transition resistance estimation results at different fault locations

[0090]

[0091] From the analysis of Table 2, we can see that when the same type of single-phase high-resistance grounding fault occurs at different fault locations, by comparing the estimated results of each group of transition resistances, it can be found that the feeders with the minimum values ​​are all faulty feeders, and the minimum values ​​are all close to the grounding resistance value.

[0092] use Figure 4 The 10kV resonant grounding system topology shown in the figure is simulated for the same fault location with different initial fault phase angles. It is assumed that a fault occurs at the end of l3, the system overcompensation is 10%, the grounding resistance is 800Ω, and other conditions remain unchanged. Only the initial fault phase angle is changed. By analyzing the estimated values ​​of the transition resistance of each feeder, it is determined whether the line selection result of this method is correct.

[0093] Table 3 Transition resistance estimation results at different fault initial phase angles

[0094]

[0095] Table 3 lists the simulation results under the changing fault initial phase angle. It can be seen from Table 3 that when the fault location and grounding resistance value remain unchanged and only the fault initial phase angle changes, the line l The estimated values ​​of transition resistance of 3 are close to 800Ω, and are smaller than the estimated values ​​of transition resistance of other lines. l 3 is the faulty feeder.

[0096] In order to further verify the anti-interference ability of the proposed method, a single-phase high-resistance fault scenario is set for each feeder, and noise with different signal-to-noise ratios (SNR) is introduced in each scenario; the transition resistance estimation results are shown in Table 4;

[0097] Table 4 Parameter estimation results under strong noise interference

[0098] It can be seen from Table 4 that under different fault conditions, when Gaussian white noise with different signal-to-noise ratios is added, the correct faulty feeder can be selected according to the estimated results of the transition resistance of each feeder, indicating that the method has outstanding anti-noise ability.

[0099] The results show that the method proposed by the present invention is not affected by noise, initial phase angle and fault position and has high reliability.

[0100] Working principle of the invention

[0101] 1. Zero-sequence equivalent network diagram of arc suppression coil grounding system

[0102] In the case of a high-resistance fault, the resistance R is roughly equivalent to 3 times the transition resistance, causing the grounding current flowing through the fault point to become weak, the charging and discharging rate of the capacitor to slow down, and the resonant frequency of the system to decrease; at this time, the line inductance L can be ignored due to its small inductive reactance; the fault transient process is mainly caused by the system distributed capacitance C and the inductance of the arc suppression coil. L p The parallel resonance is dominant, that is, the equivalent model of the system when a single-phase high-resistance fault occurs can be simplified as Figure 2 The second-order RLC parallel circuit shown in i p It is the zero-sequence current flowing through the neutral point or through the arc suppression coil.

[0103] according to Figure 2 , write the circuit equation:

[0104] (1)

[0105] (2)

[0106] (3)

[0107] Combining equations (1), (2) and (3), we get the second-order differential equation:

[0108] (4)

[0109] The characteristic root is solved as:

[0110] (5)

[0111] Which defines:

[0112] (6)

[0113] (7)

[0114] 2. Analysis of steady-state characteristics of single-phase high-resistance fault

[0115] When a high-resistance fault occurs, the system is in an underdamped state. When the resistance R satisfies equation (8), r3 and r4 are a pair of conjugate complex roots, and:

[0116] (8)

[0117] Therefore, let the neutral point zero sequence current ip be:

[0118] (9)

[0119] The busbar zero-sequence voltage u0 is:

[0120] (10)

[0121] According to the initial conditions u0(0-)=0, ip(0-)=0, t=0, the constant coefficients of the second-order differential equation are solved as follows:

[0122] (11)

[0123] The zero-sequence current ik (k=1,2,…,n-1) of a healthy feeder is:

[0124] (12)

[0125] Fault feeder zero sequence current i n for:

[0126] (13)

[0127] According to equation (12), the steady-state component of the zero-sequence current of a healthy feeder can be expressed as:

[0128] (14)

[0129] According to equation (13), the steady-state component of the zero-sequence current of the fault feeder can be expressed as:

[0130] (15)

[0131] When the capacitive current of the distribution network exceeds 10A, an arc suppression coil should be installed. However, this value usually does not exceed 200A. Assuming that the ground capacitance current ranges from 10A to 200A, the system ground distributed capacitance C increases with the increase of ground capacitance current. The range of C is 1.84×10 -6 f / 3.68×10 -5 F, arc suppression coil inductance L p As the capacitance current to ground increases, it decreases. Assuming the system overcompensation is 10%, L p The range is 0.08H~1.67H; since the maximum capacitance current of a single feeder to ground cannot exceed 50A, C 0k The maximum value is 9.19×10 -6 F, C 0k ω The maximum value of 0 is 2.89×10 -3 S; Analyze the amplitude and phase differences of the steady-state components of zero-sequence current of each line based on the inherent parameters of the distribution network.

[0132] Amplitude analysis: Comparing equation (14) with equation (1), the amplitude difference of the steady-state component of zero-sequence current between the healthy feeder and the faulty feeder is and ,when Take the maximum value of 2.89mS, L p When the minimum value is 0.08H, The value of is 0.07, The value of is 0.71, the difference is too small, and the resonant grounding system may have a situation where the amplitude of the healthy line is greater than the fault line; therefore, the steady-state component line selection method based on amplitude difference cannot accurately identify the fault line.

[0133] Phase analysis: By comparing equation (14) and equation (15), it can be obtained that the phase difference between the steady-state component of zero-sequence current of the healthy feeder and the faulty feeder is and ,because C k >0, L p >0, so ;because The value range of is 0.697~0.709, so , the phases of the healthy feeder and the faulty feeder are the same; therefore, the steady-state component line selection method based on phase difference cannot accurately identify the faulty line; Figure 3 is the zero-sequence current waveform of the fault feeder and the sound feeder in the resonant grounding system with high impedance and underdamping, Figure 3 It can be seen that in the steady-state region, the phases of the healthy feeder and the faulty feeder are basically the same, and the line cannot be selected based on the phase difference.

[0134] 3. Analysis of transient characteristics of single-phase high-resistance fault

[0135] According to formula (10), the transient component of the bus zero-sequence voltage can be expressed as:

[0136] (16)

[0137] Integrating it gives:

[0138] (17)

[0139] According to equation (12), the transient component of the zero-sequence current of a healthy feeder can be expressed as:

[0140] (18)

[0141] Integrating it gives:

[0142] (19)

[0143] According to equation (13), the transient component of the zero-sequence current of the fault feeder can be expressed as:

[0144] (20)

[0145] Integrating it gives:

[0146] (twenty one)

[0147] Analyzing equations (19) and (21), we can obtain that when a single-phase high-resistance fault occurs, the integral value of the transient part of the zero-sequence current of the healthy feeder is directly proportional to the transient part of the zero-sequence voltage of the busbar, and the proportionality coefficient is the zero-sequence capacitance of the line to the ground; while the integral value of the transient part of the zero-sequence current of the faulty feeder is linearly related to the transient part of the zero-sequence voltage of the busbar and its integral, and the proportionality coefficients are the derivatives of the zero-sequence capacitance of the line to the ground and the grounding resistance, respectively.

[0148] In summary: the present invention has the following beneficial effects:

[0149] 1) Analysis of single-phase high-resistance fault characteristics: Steady-state and transient analyses are performed on single-phase high-resistance faults occurring under resonant grounding mode. Theoretical analysis is used to find out why high-resistance fault detection cannot be achieved using only the steady-state components of the zero-sequence current of each feeder and the zero-sequence voltage of the bus. Then, by extracting the transient components of the bus zero-sequence voltage and the zero-sequence current of each feeder, it is found that the integral value of the transient part of the zero-sequence current of the faulty feeder is linearly correlated with the transient part of the bus zero-sequence voltage and its integral, and the proportional coefficients are the derivatives of the zero-sequence capacitance to ground and the grounding resistance of the line, respectively, which lays the foundation for the detection of single-phase high-resistance faults.

[0150] 2) High-resistance fault detection criteria: First, collect the bus zero-sequence voltage. When its effective value is greater than 0.15 times the system voltage, start the single-phase high-resistance fault line selection method. Then, collect the bus zero-sequence voltage and each feeder zero-sequence current waveform within 20 cycles after the fault, and subtract the waveform data of the corresponding first 10 cycles from the waveform of the last 10 cycles to obtain several voltage and current transient components. Secondly, use the linear relationship between the voltage and current transient components and use the least squares method to estimate the value of the transition resistance of each feeder. Finally, through the difference in the transition resistance of each feeder, single-phase high-resistance fault detection can be achieved. The criterion calculation is simple, and it is not affected by the transition resistance, so the reliability is higher.

[0151] A single-phase high-resistance fault detection device for a resonant grounding system based on transition resistance, comprising a signal acquisition module, a fault start criterion module, a transient component extraction module, a transient component integral and linear relationship fitting module, a fault detection and positioning module, a display and alarm module, a communication module, and a data storage module, wherein the signal acquisition module, the fault start criterion module, the transient component extraction module, the transient component integral and linear relationship fitting module, the fault detection and positioning module, the display and alarm module, the communication module, and the data storage module are electrically connected in sequence;

[0152] The signal acquisition module is responsible for real-time acquisition of the busbar zero-sequence voltage and the zero-sequence current signals of each feeder; this module must have high-precision sampling capabilities to ensure that the acquired signals are accurate;

[0153] The fault start judgment module determines whether to start the single-phase high-resistance fault detection process according to the collected bus zero-sequence voltage effective value; when the bus zero-sequence voltage effective value is greater than 0.15 times the system voltage, the detection is started;

[0154] The transient component extraction module extracts the bus zero-sequence voltage and each feeder zero-sequence current waveform within 20 power frequency cycles after the fault moment after the fault is detected, and obtains the transient component by subtracting the waveform of the first 10 cycles from the waveform of the last 10 cycles;

[0155] The transient component integration and linear relationship fitting module uses the area method to calculate the integral results of each transient component, and finds the linear relationship between the busbar zero-sequence voltage transient component and the zero-sequence current transient component of each feeder; the least squares method is used to fit the linear relationship to calculate the transition resistance value of each feeder;

[0156] The fault detection and location module compares the transition resistance values ​​of each feeder to determine which feeder has a significantly lower transition resistance value than other feeders, thereby determining the fault line;

[0157] Display and alarm module, when a single-phase high-resistance fault is detected, the fault information (such as fault feeder number, fault time, etc.) is displayed on the display screen, and an audible and visual alarm signal is issued;

[0158] Communication module, which communicates with the host computer or other intelligent devices, uploads fault detection results, and receives control instructions;

[0159] The data storage module stores the collected signal data, calculation results and fault detection records for subsequent analysis.

[0160] In this embodiment, the single-phase high-resistance fault detection device of the resonant grounding system based on transition resistance includes a processor and a memory, wherein the processor includes a kernel, and the kernel retrieves the corresponding program unit from the memory. One or more kernels may be provided, and the above-mentioned single-phase high-resistance fault line selection method of the resonant grounding system based on transition resistance is realized by adjusting kernel parameters.

[0161] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0162] An embodiment of the present application provides a processor configured to execute the above-mentioned single-phase high-resistance fault line selection method for a resonant grounding system based on transition resistance.

[0163] An embodiment of the present application provides a machine-readable storage medium having instructions stored thereon. When the instructions are executed by a processor, the processor is configured to execute the above-mentioned single-phase high-resistance fault line selection method for a resonant grounding system based on transition resistance.

[0164] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0165] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0166] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0167] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0168] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0169] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0170] Computer readable media include permanent and non-permanent, removable and non-removable media, and can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0171] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0172] The embodiments of the present invention are provided for the purpose of illustration and description. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations of the present invention. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A single-phase high-resistance fault line selection method for a resonant grounding system based on transition resistance is characterized by: The following steps are involved: S1. Construct a single-phase high-resistance fault detection start criterion, collect the bus zero-sequence voltage, and start the single-phase high-resistance fault detection method when the effective value of the bus zero-sequence voltage is greater than 0.15 times the system voltage; S2. Obtain the transient components of each feeder current and bus voltage respectively, obtain the bus zero-sequence voltage and each feeder zero-sequence current signal of the window length of 20 power frequency cycles after the fault moment, and subtract the waveform data of the corresponding first 10 cycles from the waveform of the last 10 cycles to obtain several transient components; S3. Fit the linear relationship between the integrals of the transient components of voltage and current and calculate the grounding resistance. Use the area method to estimate the integral results of each transient component to obtain the linear relationship between them. Use the least squares method to fit the linear relationship and calculate the grounding resistance. R Size; according to 1 / (3 R f ) = 1 / R , the transition resistance is calculated R f ; S4, constructing a single-phase high-resistance fault detection criterion using the transition resistance value, calculating the transition resistance value of each feeder, and realizing single-phase high-resistance fault detection by comparing the difference in the transition resistance values ​​of each feeder; The integration results of each transient component calculated by the area method in step 3 are used to obtain the linear relationship between them, and the least squares method is used to fit the linear relationship to calculate the grounding resistance. R The specific steps of size are as follows: Step 3.1: First, the specific calculation process of the integral results of each transient component calculated using the area method is as follows: ； In the formula, and They represent the busbar zero-sequence voltage transient component and the j The integral value of the transient component of the zero-sequence current of the feeder; and Respectively represent and The time corresponding to each sampling point; Step 3.2: Obtain the expressions of bus zero-sequence voltage and zero-sequence current of each feeder when a single-phase high-resistance fault occurs in the resonant grounding system, and extract their transient components. When a single-phase high-resistance fault occurs, the integral value of the transient part of the zero-sequence current of the healthy feeder is directly proportional to the transient part of the bus zero-sequence voltage, and the proportionality coefficient is the zero-sequence capacitance of the feeder to the ground; while the integral value of the transient part of the zero-sequence current of the faulty feeder is linearly related to the transient part of the bus zero-sequence voltage and its integral, and the proportionality coefficients are the derivatives of the zero-sequence capacitance of the feeder to the ground and the grounding resistance, respectively. The following results are obtained through analysis: ； In the formula, Indicates j The capacitance of the feeder to ground; R Indicates the grounding resistance; For the convenience of calculation, let , , , then the above formula can be simplified to: ； Step 3.3: Use the difference between the left and right sides of the above equation to define the overall error of each feeder as: ； In the formula, Indicates j The overall error of the feeder; , and They represent the bus zero-sequence voltage transient component, the bus zero-sequence voltage transient component integral value and the j The integral value of the transient component of the zero-sequence current of the feeder k The value corresponding to each sampling point; Then, the transient relationship of each current and voltage transient component is fitted using the least squares method through the formula in step 3.

2. First, the partial derivative of 1 / R is calculated: ； Simplifying, we can get the expression of 1 / R as: 。 2. A method for selecting a single-phase high-resistance fault line in a resonant grounding system based on transition resistance as claimed in claim 1, characterized in that: The specific formula for calculating each transient component in step 2 is as follows: ； In the formula, is the transient component of bus zero-sequence voltage k The value corresponding to the sampling point, For the j The transient component of zero-sequence current of feeder k The value corresponding to the sampling point; N represents the number of sampling points in a sampling period; and Respectively represent the bus zero sequence voltage and The value of the sampling point; and Respectively represent j Feeder zero sequence current and The value of the sampling point.

3. A method for selecting a single-phase high-resistance fault line in a resonant grounding system based on transition resistance as claimed in claim 1, characterized in that: In step S4, the specific process of realizing single-phase high-resistance fault detection by comparing the values ​​of transition resistances of each feeder is as follows: S4.

1. First calculate the estimated value of 1 / R, then calculate the transition resistance R f The value of S4.

2. Finally, when the transition resistance calculated for a line R f If the value of is significantly lower than that of all other lines, the line can be determined to be a faulty line, thus realizing single-phase high-resistance fault detection.

4. A single-phase high-resistance fault detection device for a resonant grounding system based on transition resistance, characterized in that: A single-phase high-resistance fault detection method for a resonant grounding system based on transition resistance according to any one of claims 1 to 3, comprising: The signal acquisition module is responsible for real-time acquisition of the busbar zero-sequence voltage and the zero-sequence current signals of each feeder; this module must have high-precision sampling capabilities to ensure that the acquired signals are accurate; The fault start judgment module determines whether to start the single-phase high-resistance fault detection process according to the collected bus zero-sequence voltage effective value; when the bus zero-sequence voltage effective value is greater than 0.15 times the system voltage, the detection is started; The transient component extraction module extracts the bus zero-sequence voltage and each feeder zero-sequence current waveform within 20 power frequency cycles after the fault moment after the fault is detected, and obtains the transient component by subtracting the waveform of the first 10 cycles from the waveform of the last 10 cycles; The transient component integration and linear relationship fitting module uses the area method to calculate the integral results of each transient component, and finds the linear relationship between the busbar zero-sequence voltage transient component and the zero-sequence current transient component of each feeder; the least squares method is used to fit the linear relationship to calculate the transition resistance value of each feeder; The fault detection and location module compares the transition resistance values ​​of each feeder to determine which feeder has a significantly lower transition resistance value than other feeders, thereby determining the fault line; Display and alarm module, when a single-phase high-resistance fault is detected, the fault information is displayed on the display screen and an audible and visual alarm signal is issued; Communication module, which communicates with the host computer or other intelligent devices, uploads fault detection results, and receives control instructions; The data storage module stores the collected signal data, calculation results and fault detection records for subsequent analysis.

5. A processor, characterized in that: The method is configured to execute the method for selecting a single-phase high-resistance fault line in a resonant grounding system based on transition resistance according to any one of claims 1 to 3.

6. A machine-readable storage medium having instructions stored thereon, characterized in that: When the instruction is executed by a processor, the processor is configured to execute the method for selecting a single-phase high-resistance fault line in a resonant grounding system based on transition resistance according to any one of claims 1 to 3.

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