Phase voltage-based phase selection method and system for single-phase earth fault of power distribution network

Abstract

The invention relates to the field of power distribution network fault diagnosis, in particular to a phase voltage-based power distribution network single-phase earth fault phase selection method and system, and the method comprises the steps: obtaining the relative variation of a three-phase voltage amplitude relative to a normal voltage EA, and carrying out the sorting, thereby obtaining a maximum variation, an intermediate variation and a minimum variation; judging whether the maximum variable quantity is smaller than or equal to alpha EA, if not, determining that the single-phase earth fault does not occur, if yes, judging whether the maximum variable quantity is larger than or equal to beta EA, if not, judging whether the maximum variable quantity is larger than 0, if not, determining that the single-phase earth fault does not occur, if yes, preliminarily judging that the phase corresponding to the intermediate variable quantity is the fault phase, and if not, judging that the phase corresponding to the intermediate variable quantity is the fault phase. If the maximum variable quantity is greater than or equal to betaEA, preliminarily judging that the phase corresponding to the minimum variable quantity is a fault phase; whether the fault phase and the non-fault phase meet the phase sequence relation or not is judged, if yes, the phase corresponding to the corresponding intermediate variable quantity or the minimum variable quantity is the fault phase, and fault phase judgment can be accurately achieved.

Description

Technical Field

[0001] The present invention relates to the field of distribution network fault diagnosis, and in particular to a phase voltage-based single-phase grounding fault phase selection method and system for distribution network. Background Art

[0002] As an important link in the power system that directly supplies power to users, the operating status of the distribution network directly affects the power supply quality and the overall stability of the system. In the neutral point non-effectively grounded distribution network, such as the system grounded by arc suppression coil, ungrounded or grounded by high resistance, single-phase grounding fault is a more common fault type. When a single-phase grounding fault occurs in this type of system, the short-circuit current is relatively small due to the non-direct grounding of the neutral point, thus avoiding the direct impact of the short-circuit current on the equipment, but it also increases the difficulty of fault detection and location.

[0003] With the expansion of the scale of power systems and the improvement of users' requirements for power supply reliability, the rapid and accurate diagnosis of single-phase grounding faults in neutral point non-effectively grounded distribution networks is particularly important. Traditional fault diagnosis methods are mostly based on characteristics such as zero-sequence voltage and harmonics, but in practical applications, due to the complex structure of distribution networks, diverse operating modes, and the influence of factors such as transition resistance, these methods often have high misjudgment and missed judgment rates.

[0004] At present, the most commonly used fault characteristics are zero-sequence voltage, zero-sequence current, harmonics, waveform, active power and other fault characteristic parameters. In some cases, phase voltage characteristics are used as the starting criterion for ground fault diagnosis. The current ground fault diagnosis methods mainly include zero-sequence current amplitude ratio method, zero-sequence current phase ratio method, zero-sequence current active component method, first half-wave method, neural network method, external signal method, multi-criteria fusion method, etc. The main problems are as follows: the above methods are greatly affected by the operation mode of the power grid, the fault characteristics used cannot be clearly distinguished from the normal state, it will have an adverse effect on the power grid, the selection and extraction of characteristic parameters are difficult, etc., resulting in serious missed judgments and misjudgments in reality.

[0005] Therefore, in the operation of the distribution network, single-phase grounding fault is one of the common fault types. Since the fault current is small when a single-phase grounding fault occurs in a system with non-effective neutral point grounding (such as grounding through an arc suppression coil, ungrounded or high-resistance grounding system), the traditional fault characteristic analysis method based on zero-sequence voltage and harmonics has a high misjudgment and missed judgment rate. Summary of the invention

[0006] In order to solve the problem that the prior art has a high misjudgment and missed judgment rate in the fault phase identification of three-phase voltage, the first aspect of the present invention proposes a phase selection method for single-phase grounding fault in a distribution network based on phase voltage, comprising:

[0007] Get the three-phase voltage amplitude relative to the normal voltage E within the preset timeA The relative changes are sorted based on the size to obtain the maximum change, the middle change and the minimum change;

[0008] Determine whether the maximum change is less than or equal to αE A If not, no single-phase grounding fault occurs. If so, determine whether the maximum change is greater than or equal to βE A , if the maximum change is less than βE A , then further determine whether the maximum change is greater than 0. If not, no single-phase grounding fault has occurred. If so, it is preliminarily determined that the phase corresponding to the intermediate change is the fault phase. If the maximum change is greater than or equal to βE A , then the phase corresponding to the minimum change is preliminarily determined to be the fault phase; where α is the first judgment coefficient, α∈[0,1], β is the second judgment coefficient β∈[0,1], and α>β;

[0009] Determine whether the faulty phase and the non-faulty phase satisfy the phase sequence relationship. If so, the phase corresponding to the corresponding intermediate change or the minimum change is the faulty phase. If not, no single-phase grounding fault occurs.

[0010] Optionally, the first judgment coefficient and the second judgment coefficient are obtained by the following steps:

[0011] Obtain the relationship curve between three-phase voltage and transition resistance in a single-phase fault power grid;

[0012] The relative change in the voltage amplitude of each phase before the intersection of the fault phase and the non-fault phase is obtained in the relationship curve, and the coefficient corresponding to the maximum value of the relative change is the first judgment coefficient; at the same time, the relative change in the voltage amplitude of each phase after the intersection of the fault phase and the non-fault phase is obtained in the relationship curve, and the coefficient corresponding to the maximum value of the relative change is the second judgment coefficient.

[0013] Optionally, the step of obtaining a relationship curve between three-phase voltage and transition resistance in a single-phase fault power grid includes:

[0014] Construct an equivalent model of single-phase grounding fault in distribution network;

[0015] Analyzing the single-phase grounding fault equivalent model of the distribution network to obtain the neutral point voltage;

[0016] The neutral point voltage is inferred to obtain a relationship curve between the phase voltage and transition resistance of the fault phase and the non-fault phase.

[0017] Optionally, the analysis of the distribution network single-phase grounding fault equivalent model to obtain the neutral point voltage is specifically as follows:

[0018] Kirchhoff's law is used to analyze the equivalent model of the single-phase grounding fault of the distribution network to obtain the neutral point voltage.

[0019] Optionally, the neutral point voltage is:

[0020]

[0021] Among them, U Ng is the neutral point voltage, R k is the transition resistance and δ is a constant value.

[0022] Optionally, the phase voltage of the fault phase is:

[0023]

[0024] Among them, U Ag is the phase voltage of the fault phase A, R k is the transition resistance and δ is a constant value.

[0025] Optionally, the non-fault phases include the fault leading phase B and the fault lagging phase C, and the phase voltage of the fault leading phase B is:

[0026]

[0027] The phase voltage of the fault lagging phase C is:

[0028]

[0029] Among them, U Bg is the phase voltage of the fault leading phase B, U Cg is the phase voltage of the fault lagging phase C, R k is the transition resistance and δ is a constant value.

[0030] Optionally, the value of the first judgment coefficient α is 0.8229.

[0031] Optionally, the value of the second judgment coefficient β is 0.5.

[0032] Optionally, the non-fault phase includes a fault leading phase and a fault lagging phase. In the overcompensated power grid, the preliminary determination that the phase corresponding to the intermediate variation is the fault phase also includes:

[0033] The phase corresponding to the minimum change is determined as the fault lagging phase, and the phase corresponding to the maximum change is determined as the fault leading phase;

[0034] In an under-compensated power grid, the preliminary determination that the phase corresponding to the intermediate variation is the fault phase also includes:

[0035] The phase corresponding to the minimum change is determined as the fault leading phase, and the phase corresponding to the maximum change is determined as the fault lagging phase.

[0036] Optionally, the non-fault phase includes a fault leading phase and a fault lagging phase. In the overcompensated power grid, the preliminary determination that the phase corresponding to the minimum change amount is the fault phase also includes:

[0037] The phase corresponding to the intermediate change is determined as the fault lagging phase, and the phase corresponding to the maximum change is determined as the fault leading phase;

[0038] In an under-compensated power grid, the preliminary determination that the phase corresponding to the minimum change is the fault phase also includes:

[0039] The phase corresponding to the intermediate change is determined as the fault leading phase, and the phase corresponding to the maximum change is determined as the fault lagging phase.

[0040] Optionally, after obtaining the maximum change, the intermediate change and the minimum change, it is determined whether the maximum change is less than or equal to αE A Previously included:

[0041] Determine whether the maximum change and the minimum change are greater than or equal to lE A If not, no single-phase grounding fault occurs. If so, further determine whether the maximum change is less than or equal to αE. A , l∈(0,0.1).

[0042] Optionally, the non-fault phase includes a fault lagging phase and a fault leading phase, and the determining whether the fault phase and the non-fault phase satisfy a phase sequence relationship is specifically as follows:

[0043] Determine whether the fault phase, fault lagging phase and fault leading phase all satisfy the phase sequence relationship.

[0044] Optionally, in the single-phase grounding fault equivalent model of the distribution network, the neutral point is grounded through an arc suppression coil, and each line includes a ground admittance branch.

[0045] Optionally, δ=3ωC-1 / (ωL), wherein ω is the angular frequency, C is the unidirectional total capacitance to ground, and L is the inductance of the arc suppression coil.

[0046] A second aspect of the present invention provides a phase selection system for a single-phase ground fault in a distribution network based on phase voltage, comprising:

[0047] The acquisition module is used to obtain the three-phase voltage amplitude relative to the normal voltage E within a preset time. A The relative changes are sorted based on the size to obtain the maximum change, the middle change and the minimum change;

[0048] Comparison module, used to determine whether the maximum change is less than or equal to αE A If not, no single-phase grounding fault occurs. If so, determine whether the maximum change is greater than or equal to βEA , if the maximum change is less than βE A , then further determine whether the maximum change is greater than 0. If not, no single-phase grounding fault has occurred. If so, it is preliminarily determined that the phase corresponding to the intermediate change is the fault phase. If the maximum change is greater than or equal to βE A , then the phase corresponding to the minimum change is preliminarily determined to be the fault phase; where α is the first judgment coefficient, α∈[0,1], β is the second judgment coefficient β∈[0,1], and α>β;

[0049] Determination module: used to determine whether the faulty phase and the non-faulty phase satisfy the phase sequence relationship. If so, the phase corresponding to the corresponding intermediate change or the minimum change is the faulty phase. If not, no single-phase grounding fault occurs.

[0050] Optionally, the first judgment coefficient and the second judgment coefficient in the comparison module are obtained by the following steps:

[0051] Obtain the relationship curve between three-phase voltage and transition resistance in a single-phase fault power grid;

[0052] The relative change in the voltage amplitude of each phase before the intersection of the fault phase and the non-fault phase is obtained in the relationship curve, and the coefficient corresponding to the maximum value of the relative change is the first judgment coefficient; at the same time, the relative change in the voltage amplitude of each phase after the intersection of the fault phase and the non-fault phase is obtained in the relationship curve, and the coefficient corresponding to the maximum value of the relative change is the second judgment coefficient.

[0053] Optionally, the comparison module obtains a relationship curve between three-phase voltage and transition resistance in a single-phase fault power grid, the steps comprising:

[0054] Construct an equivalent model of single-phase grounding fault in distribution network;

[0055] Analyzing the single-phase grounding fault equivalent model of the distribution network to obtain the neutral point voltage;

[0056] The neutral point voltage is inferred to obtain a relationship curve between the phase voltage and transition resistance of the fault phase and the non-fault phase.

[0057] Optionally, the comparison module analyzes the distribution network single-phase grounding fault equivalent model to obtain the neutral point voltage, specifically:

[0058] Kirchhoff's law is used to analyze the equivalent model of the single-phase grounding fault of the distribution network to obtain the neutral point voltage.

[0059] Optionally, the neutral point voltage in the comparison module is:

[0060]

[0061] Among them, U Ngis the neutral point voltage, R k is the transition resistance and δ is a constant value.

[0062] Optionally, the phase voltage of the faulty phase in the comparison module is:

[0063]

[0064] Among them, U Ag is the phase voltage of the fault phase A, R k is the transition resistance and δ is a constant value.

[0065] Optionally, the non-fault phases in the comparison module include a fault leading phase B and a fault lagging phase C, and the phase voltage of the fault leading phase B is:

[0066]

[0067] The phase voltage of the fault lagging phase C is:

[0068]

[0069] Among them, U Bg is the phase voltage of the fault leading phase B, U Cg is the phase voltage of the fault lagging phase C, R k is the transition resistance and δ is a constant value.

[0070] Optionally, the value of the first judgment coefficient α in the comparison module is 0.8229.

[0071] Optionally, the value of the second judgment coefficient β in the comparison module is 0.5.

[0072] Optionally, the non-fault phase in the comparison module includes a fault leading phase and a fault lagging phase. In the overcompensated power grid, the preliminary determination that the phase corresponding to the intermediate variation is the fault phase also includes:

[0073] The phase corresponding to the minimum change is determined as the fault lagging phase, and the phase corresponding to the maximum change is determined as the fault leading phase;

[0074] In an under-compensated power grid, the preliminary determination that the phase corresponding to the intermediate variation is the fault phase also includes:

[0075] The phase corresponding to the minimum change is determined as the fault leading phase, and the phase corresponding to the maximum change is determined as the fault lagging phase.

[0076] Optionally, the non-fault phase includes a fault leading phase and a fault lagging phase. In the overcompensated power grid, the preliminary determination that the phase corresponding to the minimum change amount is the fault phase also includes:

[0077] The phase corresponding to the intermediate change is determined as the fault lagging phase, and the phase corresponding to the maximum change is determined as the fault leading phase;

[0078] In an under-compensated power grid, the preliminary determination that the phase corresponding to the minimum change is the fault phase also includes:

[0079] The phase corresponding to the intermediate change is determined as the fault leading phase, and the phase corresponding to the maximum change is determined as the fault lagging phase.

[0080] Optionally, the acquisition module acquires the maximum change, the intermediate change and the minimum change, and determines whether the maximum change is less than or equal to αE A Previously included:

[0081] Determine whether the maximum change and the minimum change are greater than or equal to lE A If not, no single-phase grounding fault occurs. If so, further determine whether the maximum change is less than or equal to αE. A , l∈(0,0.1).

[0082] Optionally, the non-fault phase in the determination module includes a fault lagging phase and a fault leading phase, and the determination of whether the fault phase and the non-fault phase satisfy a phase sequence relationship is specifically as follows:

[0083] Determine whether the fault phase, fault lagging phase and fault leading phase all satisfy the phase sequence relationship.

[0084] Optionally, in the single-phase grounding fault equivalent model of the distribution network in the comparison module, the neutral point is grounded through an arc suppression coil, and each line includes a ground admittance branch.

[0085] Optionally, in the comparison module, δ=3ωC-1 / (ωL), wherein ω is the angular frequency, C is the unidirectional total capacitance to ground, and L is the inductance of the arc suppression coil.

[0086] A third aspect of the present invention provides a computer device, comprising: at least one processor and a memory; the memory and the processor are connected via a bus;

[0087] The memory is used to store one or more programs;

[0088] When the one or more programs are executed by the at least one processor, the phase selection method for single-phase grounding fault in power distribution network based on phase voltage as described above is implemented.

[0089] A fourth aspect of the present invention provides a computer-readable storage medium having an execution program stored thereon, which, when executed, implements the phase selection method for single-phase grounding fault in a distribution network based on phase voltage as described above.

[0090] Compared with the prior art, the present invention has the following beneficial effects:

[0091] The present invention provides a phase selection method and system for single-phase grounding fault in distribution network based on phase voltage, comprising obtaining the relative value of three-phase voltage amplitude to normal voltage E within a preset time. A The relative changes are sorted based on the size to obtain the maximum change, the middle change and the minimum change; determine whether the maximum change is less than or equal to αE A If not, no single-phase grounding fault occurs. If so, determine whether the maximum change is greater than or equal to βE A , if the maximum change is less than βE A , then further determine whether the maximum change is greater than 0. If not, no single-phase grounding fault has occurred. If so, it is preliminarily determined that the phase corresponding to the intermediate change is the fault phase. If the maximum change is greater than or equal to βE A , then it is preliminarily determined that the phase corresponding to the minimum change is the fault phase; whether the fault phase and the non-fault phase meet the phase sequence relationship is determined, if so, the phase corresponding to the corresponding intermediate change or the minimum change is the fault phase, if not, no single-phase grounding fault occurs; the present invention monitors the relative change size of each phase, compares the relative change size with a plurality of judgment preset values ​​obtained through analysis to obtain the fault phase, which is scientific, reasonable and has high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Figure 1 It is a flow chart of the phase identification method of the single-phase grounding fault in the distribution network based on phase voltage proposed by the present invention;

[0093] Figure 2 A schematic diagram of the steps for obtaining the first judgment coefficient and the second judgment coefficient proposed by the present invention;

[0094] Figure 3 The present invention proposes Figure 2 Detailed step diagram of step S21;

[0095] Figure 4 The single-phase grounding fault equivalent model of the distribution network proposed by the present invention;

[0096] Figure 5 A three-phase voltage relationship curve diagram of the compensation system proposed by the present invention when the fault phase is phase A;

[0097] Figure 6 It is a schematic diagram of the analysis of the three-phase voltage relationship curve of the compensation system proposed by the present invention when the fault phase is phase A;

[0098] Figure 7 A schematic diagram of the key point voltage and transition resistance of the three-phase voltage relationship curve of the grounding compensation system proposed by the present invention, in which the fault phase is phase A;

[0099] Figure 8 A schematic diagram of the key point voltage and transition resistance of the three-phase voltage relationship curve of the ungrounded compensation system proposed by the present invention, in which the fault phase is phase A;

[0100] Fig. 9 It is a three-phase voltage relationship curve diagram of the single-phase grounding fault simulation model of the 10kV overhead distribution network proposed by the present invention;

[0101] Fig.10 It is a flow chart of a complete phase voltage-based phase selection method for a single-phase grounding fault in a distribution network in an overcompensation system proposed by the present invention;

[0102] Fig.11 It is a flow chart of a complete phase voltage-based phase selection method for a single-phase grounding fault in a distribution network in an under-compensated system proposed by the present invention;

[0103] Fig.12 This is a structural schematic diagram of a phase selection system for a single-phase grounding fault in a distribution network based on phase voltage proposed by the present invention;

[0104] Fig.13 This is a schematic diagram of the structure of the electronic device proposed by the present invention. DETAILED DESCRIPTION

[0105] The present invention proposes a phase identification method and system for single-phase grounding fault in distribution network based on phase voltage. Since the phase voltage of the fault phase and the non-fault phase will change when a single-phase grounding fault occurs, and this change is closely related to grid parameters, transition resistance and other conditions, by analyzing the change characteristics of the voltage and obtaining the law therein, the single-phase grounding fault can be effectively diagnosed. Based on this idea, by establishing an equivalent model of grounding fault in distribution network considering grid parameters and transition resistance, the change characteristics of the phase voltage of grounding fault under different conditions are revealed, and a single-phase grounding fault diagnosis method and criterion based on phase voltage are proposed.

[0106] Furthermore, in the fault diagnosis of the neutral point non-effectively grounded distribution network, the change of the three-phase voltage is the most essential fault feature. At present, the research on the phase voltage of the grounding fault is insufficient and cannot support the identification of the grounding fault. The existing technology does not consider the influence of the inductance of the arc suppression coil in the non-effective grounding system in the single-phase grounding fault line selection and location analysis of the distribution network based on resistive current, and has a zero-sequence impedance and phase sequence relationship, and the existing measurement is difficult to measure the phase sequence and zero-sequence impedance, and the specific law of the phase voltage is not analyzed. The present invention can also consider the influence of the inductance of the arc suppression coil in the non-effective node system, without using the zero-sequence vector feature, carefully analyze the mechanism of the phase voltage, calculate the size of the special value of the transition resistance, and propose a single-phase grounding fault diagnosis method and criterion based on phase voltage, thereby improving the accuracy and reliability of the single-phase grounding fault diagnosis, reducing the misjudgment and missed judgment rate, and ensuring the safe and stable operation of the distribution network.

[0107] Embodiment 1:

[0108] A phase selection method for single-phase grounding fault in distribution network based on phase voltage, such as Figure 1 As shown, it includes steps S1 to S3:

[0109] S1: Get the three-phase voltage amplitude relative to the normal voltage E within the preset time A The relative changes are sorted based on size to obtain the maximum change, the middle change, and the minimum change.

[0110] The relative change of the three-phase voltage amplitude relative to the normal voltage in the actual distribution network within a preset time can be obtained by real-time monitoring, and the maximum change ΔU can be obtained by sorting based on the size of the relative change. max , Intermediate change ΔU mid and the minimum change ΔU min .

[0111] S2: Determine whether the maximum change is less than or equal to αE A If not, no single-phase grounding fault occurs. If so, determine whether the maximum change is greater than or equal to βE A , if the maximum change is less than βE A , then further determine whether the maximum change is greater than 0. If not, no single-phase grounding fault has occurred. If so, it is preliminarily determined that the phase corresponding to the intermediate change is the fault phase. If the maximum change is greater than or equal to βE A , then it is preliminarily determined that the phase corresponding to the minimum change is the fault phase; wherein α is the first judgment coefficient, α∈[0,1], β is the second judgment coefficient β∈[0,1], and α>β.

[0112] In a further preferred embodiment, Figure 2As shown, the first judgment coefficient and the second judgment coefficient are obtained by the following steps S21 and S22:

[0113] S21: Obtain a relationship curve between three-phase voltage and transition resistance in a single-phase fault power grid.

[0114] like Figure 3 As shown, step S21 specifically includes steps S211 to S213.

[0115] S211: Construct an equivalent model of single-phase grounding fault in distribution network;

[0116] S212: Analyze the equivalent model of the single-phase grounding fault of the distribution network to obtain a neutral point voltage;

[0117] S213: Inferring the neutral point voltage to obtain a relationship curve between the phase voltage and transition resistance of the fault phase and the non-fault phase.

[0118] In step S211, considering the influence of the neutral point grounding through the arc suppression coil and the line-to-ground admittance branch, an equivalent model of a single-phase grounding fault in a 10 kV distribution network is established, such as Figure 4 , assuming that the distribution network parameters are three-phase symmetrical and the single-phase grounding fault occurs at the busbar or near the busbar, the influence of line impedance and load can be ignored.

[0119] In step S212, Kirchhoff's law is preferably used to analyze the equivalent model of the single-phase grounding fault of the distribution network to obtain the neutral point voltage.

[0120] like Figure 4 As shown, let Y A =Y 1A +Y 2A , Y B =Y 1B +Y 2B , Y C =Y 1C +Y 2C , Y A =Y B =Y C =ωC, where Y A is the admittance of phase A to ground, Y B is the admittance of phase B to ground, Y C is the admittance of phase C to ground, Y 1A is the ground admittance of branch 1 of phase A, Y 2A is the ground admittance of branch 2 of phase A, Y 1B is the ground admittance of branch 1 of phase B, Y 2B is the ground admittance of branch 2 of phase B, Y 1C is the ground admittance of branch 1 of phase C, Y 2Cis the admittance of C-phase branch 2 to ground, ω is the angular frequency, and C is the total capacitance of a single phase to ground.

[0121] Based on Kirchhoff's law, the equivalent model of single-phase grounding fault in the distribution network is analyzed to obtain the neutral point voltage:

[0122]

[0123] Among them, U Ng is the neutral point voltage, R k is the transition resistance, δ is a constant value. In the model where the neutral point is grounded via an arc extinguishing coil, δ=3ωC-1 / (ωL), where L is the inductance of the arc extinguishing coil.

[0124] Based on the analysis of the neutral point voltage, in the fault circuit, the voltage vector of the fault phase A is for:

[0125]

[0126] Fault phase voltage U Ag for:

[0127]

[0128] The non-fault phases include the fault leading phase B and the fault lagging phase C. Similarly, the phase voltage vector of the non-fault phase B can be obtained. and the phase voltage vector of phase C for:

[0129]

[0130]

[0131] Therefore, the phase voltage of the fault leading phase B is:

[0132]

[0133] The phase voltage of the fault lagging phase C is:

[0134]

[0135] Among them, U Bg is the phase voltage of the fault leading phase B, U Cg is the phase voltage of the fault lagging phase C, R k is the transition resistance and δ is a constant value.

[0136] The relationship curve between each phase voltage and transition resistance can be constructed by formulas (3)(6)(7).

[0137] S22: Obtain the relative change in the voltage amplitude of each phase before the intersection of the fault phase and the non-fault phase in the relationship curve, and the coefficient corresponding to the maximum value of the relative change is the first judgment coefficient; at the same time, obtain the relative change in the voltage amplitude of each phase after the intersection of the fault phase and the non-fault phase in the relationship curve, and the coefficient corresponding to the maximum value of the relative change is the second judgment coefficient.

[0138] It can be seen from formulas (3)(6)(7) that, under the condition that the three-phase power supply voltage remains unchanged, the three-phase voltage amplitude after a single-phase grounding fault is closely related to the grid scale, compensation degree, and transition resistance.

[0139] By deriving formula (3), we can get:

[0140]

[0141] In the specific distribution network, δ is a constant value. When overcompensation occurs, δ>0. At this time, the fault phase voltage derivative is always greater than zero. The fault phase voltage shows a monotonically increasing characteristic with the transition resistance, and its variation range is [0, E A ]; When under-compensation occurs, δ<0. At this time, the fault phase voltage derivative is always less than zero, and the fault phase voltage shows a monotonically decreasing characteristic with the transition resistance. Its variation range is [-E A ,0], both cases are consistent with the phase voltage characteristics under the two extreme cases of metallic grounding and infinite transition resistance.

[0142] By deriving formula (6), we can get:

[0143]

[0144] Analysis of formula (9) shows that the voltage derivative of phase B of the fault leading phase has two zero points.

[0145] When overcompensation is δ>0, when R k ∈[0,0.3728 / δ], formula (9) is greater than 0, and the voltage amplitude of phase B presents a monotonically increasing characteristic; when R k When ∈(0.3728 / δ,+∞), formula (9) is less than 0, and the voltage amplitude of phase B shows a monotonically decreasing characteristic.

[0146] When under-compensation, δ<0, when R k ∈[0,2.6822 / δ], formula (9) is less than 0, and the voltage amplitude of phase B shows a monotonically decreasing characteristic. k When ∈(2.6822 / δ,+∞), formula (9) is greater than 0, and the voltage amplitude of phase B shows a monotonically increasing characteristic.

[0147] By deriving formula (7), we can get:

[0148]

[0149] Analysis of formula (10) shows that the voltage derivative of phase C, the fault lagging phase, has two zero points.

[0150] When overcompensation is δ>0, when R k ∈[0,0.3728 / δ], formula (10) is less than 0, and the voltage amplitude of phase C shows a monotonically decreasing characteristic; when R k When ∈(0.3728 / δ,+∞), formula (10) is greater than 0, and the voltage amplitude of phase C shows a monotonically increasing characteristic.

[0151] When under-compensation, δ<0, when R k ∈[0,2.6822 / δ], formula (10) is greater than 0, and the voltage amplitude of phase C shows a monotonically increasing characteristic; when R k When ∈(0.3728 / δ,+∞), formula (10) is less than 0, and the voltage amplitude of phase C shows a monotonically decreasing characteristic.

[0152] The above analysis also provides a rough trend curve of the three-phase voltage during a single-phase grounding fault. The under-compensated system only needs to swap the fault leading phase B and the fault lagging phase C in the over-compensated system. The following only discusses the phase voltage characteristics of the over-compensated system.

[0153] In the scenario where the number of outgoing lines, feeder length, feeder parameters, compensation parameters, etc. of the distribution network are determined, by substituting into formulas (3), (6), and (7), we can obtain the typical curve of the phase voltage changing with the transition resistance after a single-phase grounding fault occurs, as shown in Figure 5 As shown in the figure, the voltage amplitude of the fault phase A always increases with the increase of transition resistance, the voltage amplitude of the fault leading phase B shows a trend of first increasing and then decreasing with the transition resistance, and the voltage of the fault lagging phase C shows a trend of first decreasing and then increasing. In the typical curve of three-phase voltage, there are key coordinate points such as extreme points and intersection points. The key points can briefly describe the overall characteristics of the curve, analyze the phase voltage characteristics in different transition resistance intervals, and explore the comprehensive judgment criteria based on phase voltage when a single-phase grounding fault occurs.

[0154] The following analysis results take the over-compensation scenario in a three-phase symmetrical arc suppression coil grounding system as an example. In the case of under-compensation, it is only necessary to swap the fault lagging phase C with the fault leading phase B.

[0155] (1) Intersection point between fault phase A and fault lagging phase C (point 1)

[0156] The voltage of the fault phase A and the fault lagging phase C intersects in the area slightly smaller than the normal phase voltage, such as Figure 6Point 1 in the figure shows that when the transition resistance reaches a certain value, the non-fault phase voltage will be lower than the normal voltage, or even lower than the fault phase voltage. Therefore, the phenomenon that the fault phase voltage decreases and the non-fault phase voltage increases when a single-phase grounding fault occurs, which is generally believed to be directly related to the transition resistance interval, is not applicable to all single-phase grounding faults. Therefore, analyzing the intersection of the fault phase and the fault lagging phase voltage curves is of great significance for fault phase selection.

[0157] Let U Ag =U Cg , it can be concluded that the fault resistance value at the intersection of the fault phase and the fault lagging phase is 1.7321 / δΩ. Substituting it into formula (3), the coordinates of point 1 are (1.7321 / δ, 0.8660E A ).

[0158] (2) Fault leading phase extension intersection (point 2)

[0159] The intersection of the vertical extension line of point 1 and the fault leading phase voltage curve is the extended intersection point, such as Figure 6 As shown in point 2 in , the area on the left of the intersection is characterized by a fault phase voltage lower than the fault lagging phase voltage, and the area on the right is characterized by a fault phase voltage higher than the fault lagging phase voltage. When both the fault phase and the fault lagging phase voltages are lower than normal values, phase selection cannot be achieved based on the two phase voltage amplitudes alone, and it is necessary to distinguish them with the help of the fault leading phase voltage range.

[0160] Substituting the transition resistance value 1.7321 / δΩ at point 1 into formula (6), the coordinates of point 2 are (1.7321 / δ, 1.5E A ).

[0161] (3) Fault leading phase extreme point (point 3)

[0162] The voltage amplitude of the fault leading phase B shows a trend of first increasing and then decreasing with the transition resistance. Therefore, by calculating the maximum value of the phase voltage curve, as shown in Figure 6 As shown in point 3 in the figure, it can help to depict its overall change law. Let U' in formula (9) Bg =0, it can be obtained that the transition resistance at the maximum point of the fault leading phase is 0.3728 / δΩ, substituting it into formula (6) to obtain the coordinates of point 3 as (0.3728 / δ,1.8229E A ).

[0163] (4) Intersection point between the fault lagging phase C and the normal value (point 4)

[0164] The fault lagging phase voltage amplitude shows a trend of decreasing first and then increasing with the transition resistance, and the phase voltage amplitude in the second half of the decreasing section is lower than the normal value, and then the phase voltage increases again below the normal value and finally converges to the normal value. The intersection of the fault lagging phase voltage and the normal value is as follows: Figure 6 The midpoint 4 is shown as the dividing line between the fault diagnosis criteria at different stages.

[0165] Let U in formula (7) Cg =E A , it can be obtained that the transition resistance at the intersection of the fault lagging phase and the normal value is 1.1547 / δΩ. Substituting it into formula (7), the coordinate value of point 4 can be obtained as (1.1547 / δ, E A ).

[0166] (5) Fault lagging phase extreme point (point 5)

[0167] According to the characteristic that the fault lagging phase voltage amplitude first decreases and then increases, the minimum value of the phase voltage curve can be calculated, such as Figure 6 The midpoint is shown at 5.

[0168] Let U' in formula (10) Cg =0, the transition resistance at the minimum point 5 of the fault lagging phase is 2.6822 / δΩ. Substituting it into formula (7), the coordinates of point 5 are (2.6822 / δ, 0.8229E A ).

[0169] (6) The point where the phase difference is the largest after the intersection of phase A and phase C (point 6, point 7)

[0170] Depend on Figure 6 So, here is U Ag -U Cg The maximum point of U Ag -U Cg That is, we can find the derivative of formula (3) minus formula (7), and then set the derivative equal to 0 to find this point, so that formula (3) can be transformed into:

[0171]

[0172] Ask for U Ag -U Cg The maximum point of is the value below the square root of formula (11) minus the maximum point below the square root of formula (7), that is, the maximum point of formula (12).

[0173]

[0174] Among them, f(R k ) is the constructor.

[0175] Let formula (12) equal to 0, and take the positive number solution to get the transition resistance here is 3.7321 / δΩ, and the specific coordinates of point 6 are (3.7321 / δ, 0.9659E A ), the coordinates of point 7 are (3.7321 / δ,0.8372E A), the coordinates of point 8 are (3.7321 / δ,1.2518E A ).

[0176] (7) The phase difference between phase A and phase C before intersection is 0.1287E A (Point 9, Point 10, Point 11)

[0177] Subtracting formula (3) from formula (7) equals 0.1287E A It can be concluded that the transition resistance here is 1.3621 / δΩ, and the specific coordinates of point 9 are (1.3621 / δ,1.560E A ), the specific coordinates of point 10 are (1.3621 / δ,0.936E A ), the specific coordinates of point 11 are (1.3621 / δ,0.806E A ).

[0178] From the above analysis, it can be obtained that the horizontal coordinate of the key coordinate point of the phase voltage curve is only related to δ, and the vertical coordinate is a constant. Therefore, under the conditions of the distribution network scale, line parameters, and compensation parameters, the fault diagnosis and phase selection criteria can be adjusted according to the key coordinate points. In particular, the constant value characteristics of the vertical coordinate provide theoretical support for the segmented adjustment of the criteria.

[0179] Figure 4 The three-phase voltage variation curve of the distribution network when a single-phase grounding fault occurs can be divided into the following three areas according to the relative characteristics of the voltage amplitude, such as Figure 6 shown.

[0180] (1) Area 1 formed by the vertical axis and Dd and its extension line. In this area, after a single-phase grounding fault occurs in the three-phase voltage, the maximum voltage amplitude difference is large, the fault phase voltage is the lowest, the fault leading phase voltage is the highest, and the fault lagging phase voltage amplitude is between the two. In this area, the relative change range of the fault leading phase voltage relative to the normal value is [0.5E A , 0.8229E A ]. 0.8229E A is the maximum value of the relative change in area 1, and 0.8229 is the first judgment coefficient.

[0181] (2) Area 2 formed by Dd and its extension line and Ee and its extension line. In this area, after a single-phase grounding fault occurs in the three-phase voltage, the maximum voltage amplitude difference gradually decreases, but is not less than 0.05E A , the fault lagging phase voltage is the lowest, the fault leading phase voltage is the highest, and the fault phase voltage amplitude is between the two. In this area, the range of the fault leading phase voltage point pair variation is [0, 0.5E A ]. 0.5E Ais the maximum value of the relative change in area 2, and 0.5 is the second judgment coefficient.

[0182] (3) Area 3 on the right side of Ee and its extension line. In this area, after a single-phase ground fault occurs in the three-phase voltage, the relative change of the voltage is less than 0.05E A ,Due to the small difference in phase voltages, it is difficult to determine whether the sudden change in three-phase voltage is caused by a ground fault in this area.

[0183] Therefore, the key setting quantity in the single-phase grounding fault diagnosis criterion based on phase voltage is: the critical voltage of the relative change of the fault leading phase 0.5E A , which is the critical voltage between area 1 and area 2, is the dividing point between the fault phase and the fault lagging phase voltage, and is also the fault phase selection criterion. When the relative change in the voltage amplitude of the fault leading phase is greater than the critical voltage 0.5E A When the relative change of the voltage amplitude of the fault leading phase is less than the critical voltage 0.5E A When , the fault lag phase is the lowest.

[0184] Therefore, based on the above analysis, in a further preferred solution, in the overcompensated power grid, the preliminary determination in step S2 that the phase corresponding to the intermediate variation is the fault phase also includes:

[0185] The phase corresponding to the minimum change is determined as the fault lagging phase, and the phase corresponding to the maximum change is determined as the fault leading phase;

[0186] In the under-compensated power grid, the preliminary determination in step S2 that the phase corresponding to the intermediate variation is the fault phase also includes:

[0187] The phase corresponding to the minimum change is determined as the fault leading phase, and the phase corresponding to the maximum change is determined as the fault lagging phase.

[0188] In a further preferred solution, in the overcompensated power grid, the preliminary determination in step S2 that the phase corresponding to the minimum change amount is the fault phase also includes:

[0189] The phase corresponding to the intermediate change is determined as the fault lagging phase, and the phase corresponding to the maximum change is determined as the fault leading phase;

[0190] In an under-compensated power grid, the preliminary determination in step S2 that the phase corresponding to the minimum change is the fault phase also includes:

[0191] The phase corresponding to the intermediate change is determined as the fault leading phase, and the phase corresponding to the maximum change is determined as the fault lagging phase.

[0192] In a further preferred embodiment, the steps between step S1 and step S2 further include:

[0193] Determine whether the maximum change and the minimum change are greater than or equal to lE A If not, no single-phase grounding fault occurs. If so, further determine whether the maximum change is less than or equal to αE. A , l∈(0,0.1).

[0194] S3: Determine whether the faulty phase and the non-faulty phase satisfy the phase sequence relationship. If so, the phase corresponding to the corresponding intermediate change or the minimum change is the faulty phase. If not, no single-phase grounding fault occurs.

[0195] The following selects a power distribution parameter of 100Ω of total capacitance of a single phase to ground to illustrate the method in this application.

[0196] Depend on Figure 7 and Figure 8 The analysis shows that the horizontal coordinate of the key coordinate point of the phase voltage curve found in the present invention is only related to δ, while the vertical coordinate is a constant.

[0197] When phase A and phase C are equal in magnitude and the transition resistance is large, the voltage difference is small, and it is difficult to diagnose a single-phase grounding fault. When the transition resistance reaches 10379Ω in undercompensation and 12684Ω in overcompensation, the difference between the fault leading phase B and the fault lagging phase C is less than 5% of the normal phase voltage; when the transition resistance is 469Ω~592Ω in undercompensation and 573Ω~725Ω in overcompensation, the difference between the fault phase A and the fault lagging phase C is less than 5% of the normal phase voltage, which is the level that can be achieved by normal voltage fluctuations, but it is within the acceptable range in actual engineering. Therefore, the overcompensated system is more suitable for high-resistance grounding faults than the undercompensated system.

[0198] The variation patterns of phase voltages during under-compensation and over-compensation are similar, with only the transition resistance values ​​at the dividing points being different. However, the phase voltage values ​​at the decomposition points are the same, so the judgment criteria are also the same, which is consistent with the results of the mechanism analysis above.

[0199] Depend on Figure 8 Analysis shows that the resistance values ​​of the demarcation points of the ungrounded system and the arc suppression coil grounding system are different, but the phase voltage values ​​are the same, so the judgment criteria are also the same. When the transition resistance of the neutral point ungrounded system is 1155Ω, the difference between the fault leading phase B and the fault lagging phase C is less than 5% of the normal phase voltage; when the transition resistance of the neutral point ungrounded system is 53-66Ω, the difference between the fault phase A and the fault lagging phase C is less than 5% of the normal phase voltage, which is a level that can be achieved by normal voltage fluctuations, but in actual engineering it is within an acceptable range. It can be seen that the arc suppression coil system is more adaptable to high-resistance grounding faults than the ungrounded system.

[0200] The distribution network is modeled using Simulink. It is a 10kV overhead distribution network single-phase grounding fault simulation model based on Simulink. The grid parameters are the same as in the previous section. The model uses two outgoing lines with a voltage level of 110kV / 10.5kV. The high-voltage side of the 10kV / 380V transformer adopts Δ-type connection. The line parameters are 5nF of capacitance to ground per kilometer and a compensation degree of 1.1.

[0201] By changing the transition resistance, the three-phase voltage under different grounding resistances can be obtained from the distribution network single-phase grounding fault simulation model, and then the relationship between the three-phase voltage and transition resistance of the simulated distribution network can be obtained by fitting. Fig. 9 shown.

[0202] Depend on Fig. 9 Analysis shows that the voltage of the fault phase A of the simulated distribution network increases with the increase of transition resistance. The voltage of the fault lagging phase C first decreases to the normal phase voltage or even below the voltage of the fault phase A, and then increases to near the normal phase voltage. The voltage of the fault leading phase B increases to the maximum value point and then decreases to near the normal phase voltage.

[0203] The intersection point of the fault phase A curve and the fault phase C curve is (642, 5.0). After the intersection point, the maximum difference between phase A and phase C is (1382, 5.60), and the same difference before the intersection point is (512, 4.60).

[0204] The maximum point of the non-fault phase B curve is (642, 8.70), and the B point corresponding to the grounding resistance at the intersection of phases A and C is (1382, 7.43). The same difference before the intersection is (512, 9.28).

[0205] The minimum point of the non-fault phase C curve is (938, 4.75), the point of C where the difference between phases A and C is the largest after the intersection is (1382, 4.92), and the same difference before the intersection is (512, 5.47).

[0206] The error between the above data and the conclusion obtained by the present invention is less than 3%, which can prove that the characteristic analysis of the key characteristic points of the phase voltage is correct.

[0207] Based on the above method, a simulation model is constructed to verify the phase selection method for single-phase ground fault based on phase voltage in the present invention. By applying the fault phase selection method described in the present invention, 100 different ground resistance values ​​are selected within the applicable range, and the accuracy rate can reach 98.3%. The following Table 1 shows the results of ten typical cases.

[0208]

[0209] It can be seen that the fault phase selection method in the present invention has high accuracy.

[0210] Application process, in the over-compensation system, the complete fault phase selection method of the present invention is as follows Fig.10 As shown, the relative changes of the three-phase voltage amplitudes are monitored in real time, and the relative changes are sorted to obtain the maximum change ΔU max , intermediate change ΔU mid And the minimum change ΔU min , and then judge ΔU max -ΔU min Is it greater than l*E A , if ΔU max -ΔU min Greater than or equal to l*E A， Then further determine ΔU max Is it less than or equal to 0.8229E A , if ΔU max -ΔU min Less than l*E A， No single-phase fault occurs. If ΔU max Greater than 0.8229E A , then no single-phase fault occurs, so ΔU max No less than or equal to 0.8229E A , then further determine ΔU max Is it greater than or equal to 0.5E? A If so, then preliminarily determine ΔU min The corresponding phase is the fault phase, ΔU mid The corresponding phase is the fault lagging phase, ΔU max The corresponding phase is the fault leading phase. If not, further determine ΔU max Is it greater than 0? If ΔU max If it is greater than 0, then the initial judgment is ΔU mid The corresponding phase is the fault phase, ΔU min The corresponding phase is the fault lagging phase, ΔU max The corresponding phase is the fault leading phase. If ΔU max If it is less than or equal to 0, a single-phase grounding fault occurs. Further determine whether the amplitudes corresponding to each phase conform to the phase sequence relationship. If so, it is confirmed that a single-phase grounding fault occurs. ΔU min or ΔU mid It is the fault phase, otherwise no single-phase grounding fault occurs.

[0211] Similarly, in an undercompensated system, if Fig.11 As shown, the complete fault phase selection method in the present invention is as follows Fig.13 As shown, the relative changes of the three-phase voltage amplitudes are monitored in real time, and the relative changes are sorted to obtain the maximum change ΔU max, intermediate change ΔU mid And the minimum change ΔU min , and then judge ΔU max -ΔU min Is it greater than l*E A , if ΔU max -ΔU min Greater than or equal to l*E A， Then further determine ΔU max Is it less than or equal to 0.8229E A , if ΔU max -ΔU min Less than l*E A， No single-phase fault occurs. If ΔU max Greater than 0.8229E A , then no single-phase fault occurs, so ΔU max No less than or equal to 0.8229E A , then further determine ΔU max Is it greater than or equal to 0.5E? A If so, then preliminarily determine ΔU min The corresponding phase is the fault phase, ΔU mid The corresponding phase is the fault leading phase, ΔU max The corresponding phase is the fault lagging phase. If not, further determine ΔU max Is it greater than 0? If ΔU max If it is greater than 0, then the initial judgment is ΔU mid The corresponding phase is the fault phase, ΔU min The corresponding phase is the fault leading phase, ΔU max The corresponding phase is the fault lagging phase. If ΔU max If it is less than or equal to 0, a single-phase grounding fault occurs. Further determine whether the amplitudes corresponding to each phase conform to the phase sequence relationship. If so, it is confirmed that a single-phase grounding fault occurs. ΔU min or ΔU mid It is the fault phase, otherwise no single-phase grounding fault occurs.

[0212] Embodiment 2:

[0213] The present invention based on the same inventive concept also provides a phase selection system for single-phase grounding fault in a distribution network based on phase voltage, such as Fig.12 As shown, including:

[0214] The acquisition module is used to obtain the three-phase voltage amplitude relative to the normal voltage E within a preset time. A The relative changes are sorted based on the size to obtain the maximum change, the middle change and the minimum change;

[0215] Comparison module, used to determine whether the maximum change is less than or equal to αEA If not, no single-phase grounding fault occurs. If so, determine whether the maximum change is greater than or equal to βE A , if the maximum change is less than βE A , then further determine whether the maximum change is greater than 0. If not, no single-phase grounding fault has occurred. If so, it is preliminarily determined that the phase corresponding to the intermediate change is the fault phase. If the maximum change is greater than or equal to βE A , then the phase corresponding to the minimum change is preliminarily determined to be the fault phase; where α is the first judgment coefficient, α∈[0,1], β is the second judgment coefficient β∈[0,1], and α>β;

[0216] Determination module: used to determine whether the faulty phase and the non-faulty phase satisfy the phase sequence relationship. If so, the phase corresponding to the corresponding intermediate change or the minimum change is the faulty phase. If not, no single-phase grounding fault occurs.

[0217] In a further preferred embodiment, the first judgment coefficient and the second judgment coefficient in the comparison module are obtained by the following steps:

[0218] Obtain the relationship curve between three-phase voltage and transition resistance in a single-phase fault power grid;

[0219] The relative change in the voltage amplitude of each phase before the intersection of the fault phase and the non-fault phase is obtained in the relationship curve, and the coefficient corresponding to the maximum value of the relative change is the first judgment coefficient; at the same time, the relative change in the voltage amplitude of each phase after the intersection of the fault phase and the non-fault phase is obtained in the relationship curve, and the coefficient corresponding to the maximum value of the relative change is the second judgment coefficient.

[0220] In a further preferred solution, the comparison module obtains a relationship curve between three-phase voltage and transition resistance in a single-phase fault power grid, and the steps include:

[0221] Construct an equivalent model of single-phase grounding fault in distribution network;

[0222] Analyzing the single-phase grounding fault equivalent model of the distribution network to obtain the neutral point voltage;

[0223] The neutral point voltage is inferred to obtain a relationship curve between the phase voltage and transition resistance of the fault phase and the non-fault phase.

[0224] In a further preferred solution, the comparison module analyzes the distribution network single-phase grounding fault equivalent model to obtain the neutral point voltage, specifically:

[0225] Kirchhoff's law is used to analyze the equivalent model of the single-phase grounding fault of the distribution network to obtain the neutral point voltage.

[0226] In a further preferred solution, the neutral point voltage in the comparison module is:

[0227]

[0228] Among them, U Ng is the neutral point voltage, R k is the transition resistance and δ is a constant value.

[0229] In a further preferred solution, the phase voltage of the faulty phase in the comparison module is:

[0230]

[0231] Among them, U Ag is the phase voltage of the fault phase A, R k is the transition resistance and δ is a constant value.

[0232] In a further preferred solution, the non-fault phases in the comparison module include the fault leading phase B and the fault lagging phase C, and the phase voltage of the fault leading phase B is:

[0233]

[0234] The phase voltage of the fault lagging phase C is:

[0235]

[0236] Among them, U Bg is the phase voltage of the fault leading phase B, U Cg is the phase voltage of the fault lagging phase C, R k is the transition resistance and δ is a constant value.

[0237] In a further preferred solution, the value of the first judgment coefficient α in the comparison module is 0.8229.

[0238] In a further preferred solution, the value of the second judgment coefficient β in the comparison module is 0.5.

[0239] In a further preferred solution, the non-fault phase in the comparison module includes a fault leading phase and a fault lagging phase. In the overcompensated power grid, the preliminary determination that the phase corresponding to the intermediate variation is the fault phase also includes:

[0240] The phase corresponding to the minimum change is determined as the fault lagging phase, and the phase corresponding to the maximum change is determined as the fault leading phase;

[0241] In an under-compensated power grid, the preliminary determination that the phase corresponding to the intermediate variation is the fault phase also includes:

[0242] The phase corresponding to the minimum change is determined as the fault leading phase, and the phase corresponding to the maximum change is determined as the fault lagging phase.

[0243] In a further preferred solution, the non-fault phase includes a fault leading phase and a fault lagging phase. In the overcompensated power grid, the preliminary determination that the phase corresponding to the minimum change is the fault phase also includes:

[0244] The phase corresponding to the intermediate change is determined as the fault lagging phase, and the phase corresponding to the maximum change is determined as the fault leading phase;

[0245] In an under-compensated power grid, the preliminary determination that the phase corresponding to the minimum change is the fault phase also includes:

[0246] The phase corresponding to the intermediate change is determined as the fault leading phase, and the phase corresponding to the maximum change is determined as the fault lagging phase.

[0247] In a further preferred embodiment, the acquisition module acquires the maximum change, the intermediate change and the minimum change, and determines whether the maximum change is less than or equal to αE A Previously included:

[0248] Determine whether the maximum change and the minimum change are greater than or equal to lE A If not, no single-phase grounding fault occurs. If so, further determine whether the maximum change is less than or equal to αE. A , l∈(0,0.1).

[0249] In a further preferred solution, the non-fault phase in the determination module includes a fault lagging phase and a fault leading phase, and the determination of whether the fault phase and the non-fault phase satisfy the phase sequence relationship is specifically as follows:

[0250] Determine whether the fault phase, fault lagging phase and fault leading phase all satisfy the phase sequence relationship.

[0251] In a further preferred solution, the neutral point in the single-phase grounding fault equivalent model of the distribution network in the comparison module is grounded through an arc suppression coil, and each line includes a ground admittance branch.

[0252] In a further preferred solution, in the comparison module, δ=3ωC-1 / (ωL), wherein ω is the angular frequency, C is the unidirectional total capacitance to the ground, and L is the inductance of the arc suppression coil.

[0253] Example 3

[0254] like Fig.13As shown, the present invention also provides an electronic device, which may be a computer device, a single-chip device, an intelligent mobile device, etc. The electronic device in this embodiment may include a processor, a memory, a transceiver component, etc. The memory, the processor, and the transceiver component are connected via a bus; the memory may be used to store an execution program, and an exemplary execution program may include instructions; the processor is used to execute the instructions stored in the memory. The memory may also be used to store data, which may be called and / or modified when the instructions are executed.

[0255] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in a storage medium to implement the corresponding method flow or corresponding functions, so as to implement the steps of a single-phase grounding fault phase identification method for a distribution network based on phase voltage in the above-mentioned embodiment.

[0256] Example 4

[0257] Based on the same inventive concept, the present invention also provides a readable storage medium, specifically an electronic device readable storage medium (Memory), which is a memory device in the electronic device for storing programs and data. It can be understood that the storage medium here can include both the built-in storage medium in the electronic device and the extended storage medium supported by the electronic device. The storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more execution programs (including program codes). It should be noted that the storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk storage. The processor loads and executes one or more instructions stored in the storage medium, which can implement the steps of a single-phase grounding fault phase identification method for a distribution network based on phase voltage in the above embodiment.

[0258] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take 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 code.

[0259] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of 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 produce 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.

[0260] 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 comprising 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.

[0261] 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. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0262] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A phase selection method for single-phase grounding fault in distribution network based on phase voltage, characterized in that: include: Get the three-phase voltage amplitude relative to the normal voltage E within the preset time A The relative changes are sorted based on the size to obtain the maximum change, the middle change and the minimum change; Determine whether the maximum change is less than or equal to αE A If not, no single-phase grounding fault occurs. If so, determine whether the maximum change is greater than or equal to βE A , if the maximum change is less than βE A , then further determine whether the maximum change is greater than 0. If not, no single-phase grounding fault has occurred. If so, it is preliminarily determined that the phase corresponding to the intermediate change is the fault phase. If the maximum change is greater than or equal to βE A , then the phase corresponding to the minimum change is preliminarily determined to be the fault phase; where α is the first judgment coefficient, α∈[0,1], β is the second judgment coefficient β∈[0,1], and α>β; Determine whether the faulty phase and the non-faulty phase satisfy the phase sequence relationship. If so, the phase corresponding to the corresponding intermediate change or the minimum change is the faulty phase. If not, no single-phase grounding fault occurs.

2. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 1 is characterized in that: The first judgment coefficient and the second judgment coefficient are obtained by the following steps: Obtain the relationship curve between three-phase voltage and transition resistance in a single-phase fault power grid; The relative change in the voltage amplitude of each phase before the intersection of the fault phase and the non-fault phase is obtained in the relationship curve, and the coefficient corresponding to the maximum value of the relative change is the first judgment coefficient; at the same time, the relative change in the voltage amplitude of each phase after the intersection of the fault phase and the non-fault phase is obtained in the relationship curve, and the coefficient corresponding to the maximum value of the relative change is the second judgment coefficient.

3. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 2 is characterized in that: The step of obtaining a relationship curve between three-phase voltage and transition resistance in a single-phase fault power grid comprises: Construct an equivalent model of single-phase grounding fault in distribution network; Analyzing the single-phase grounding fault equivalent model of the distribution network to obtain the neutral point voltage; The neutral point voltage is inferred to obtain a relationship curve between the phase voltage and transition resistance of the fault phase and the non-fault phase.

4. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 3 is characterized in that: The neutral point voltage is obtained by analyzing the equivalent model of the single-phase grounding fault of the distribution network, specifically: Kirchhoff's law is used to analyze the equivalent model of the single-phase grounding fault of the distribution network to obtain the neutral point voltage.

5. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 3 or 4, characterized in that: The neutral point voltage is: Among them, U Ng is the neutral point voltage, R k is the transition resistance and δ is a constant value.

6. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 3 or 4, characterized in that: The phase voltage of the fault phase is: Among them, U Ag is the phase voltage of the fault phase A, R k is the transition resistance and δ is a constant value.

7. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 3 or 4, characterized in that: The non-fault phases include the fault leading phase B and the fault lagging phase C. The phase voltage of the fault leading phase B is: The phase voltage of the fault lagging phase C is: Among them, U Bg is the phase voltage of the fault leading phase B, U Cg is the phase voltage of the fault lagging phase C, R k is the transition resistance and δ is a constant value.

8. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 1 or 2, characterized in that: The value of the first judgment coefficient α is 0.8229.

9. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 1 or 2, characterized in that: The value of the second determination coefficient β is 0.

5.

10. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 1, characterized in that: The non-fault phase includes a fault leading phase and a fault lagging phase. In the overcompensated power grid, the preliminary determination that the phase corresponding to the intermediate variation is the fault phase also includes: The phase corresponding to the minimum change is determined as the fault lagging phase, and the phase corresponding to the maximum change is determined as the fault leading phase; In an under-compensated power grid, the preliminary determination that the phase corresponding to the intermediate variation is the fault phase also includes: The phase corresponding to the minimum change is determined as the fault leading phase, and the phase corresponding to the maximum change is determined as the fault lagging phase.

11. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 1 or 10, characterized in that: The non-fault phase includes a fault leading phase and a fault lagging phase. In the overcompensated power grid, the phase corresponding to the minimum change is initially determined to be the fault phase and also includes: The phase corresponding to the intermediate change is determined as the fault lagging phase, and the phase corresponding to the maximum change is determined as the fault leading phase; In an under-compensated power grid, the preliminary determination that the phase corresponding to the minimum change is the fault phase also includes: The phase corresponding to the intermediate change is determined as the fault leading phase, and the phase corresponding to the maximum change is determined as the fault lagging phase.

12. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 1, characterized in that: After obtaining the maximum change, the intermediate change, and the minimum change, determine whether the maximum change is less than or equal to αE A Previously included: Determine whether the maximum change and the minimum change are greater than or equal to lE A If not, no single-phase grounding fault occurs. If so, further determine whether the maximum change is less than or equal to αE. A , l∈(0,0.1).

13. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 1, characterized in that: The non-fault phase includes a fault lagging phase and a fault leading phase, and the determination of whether the fault phase and the non-fault phase satisfy the phase sequence relationship is specifically as follows: Determine whether the fault phase, fault lagging phase and fault leading phase all satisfy the phase sequence relationship.

14. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 5, characterized in that: In the single-phase grounding fault equivalent model of the distribution network, the neutral point is grounded via an arc suppression coil, and each line includes a ground admittance branch.

15. The phase selection method for single-phase grounding fault in distribution network based on phase voltage according to claim 14, characterized in that: δ=3ωC-1 / (ωL), wherein ω is the angular frequency, C is the total unidirectional capacitance to the ground, and L is the inductance of the arc suppression coil.

16. A phase selection system for single-phase grounding fault in distribution network based on phase voltage, characterized in that: include: The acquisition module is used to obtain the three-phase voltage amplitude relative to the normal voltage E within a preset time. A The relative changes are sorted based on the size to obtain the maximum change, the middle change and the minimum change; Comparison module, used to determine whether the maximum change is less than or equal to αE A If not, no single-phase grounding fault occurs. If so, determine whether the maximum change is greater than or equal to βE A , if the maximum change is less than βE A , then further determine whether the maximum change is greater than 0. If not, no single-phase grounding fault has occurred. If so, it is preliminarily determined that the phase corresponding to the intermediate change is the fault phase. If the maximum change is greater than or equal to βE A , then the phase corresponding to the minimum change is preliminarily determined to be the fault phase; where α is the first judgment coefficient, α∈[0,1], β is the second judgment coefficient β∈[0,1], and α>β; Determination module: used to determine whether the faulty phase and the non-faulty phase satisfy the phase sequence relationship. If so, the phase corresponding to the corresponding intermediate change or the minimum change is the faulty phase. If not, no single-phase grounding fault occurs.

17. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 16, characterized in that: The first judgment coefficient and the second judgment coefficient in the comparison module are obtained by the following steps: Obtain the relationship curve between three-phase voltage and transition resistance in a single-phase fault power grid; The relative change in the voltage amplitude of each phase before the intersection of the fault phase and the non-fault phase is obtained in the relationship curve, and the coefficient corresponding to the maximum value of the relative change is the first judgment coefficient; at the same time, the relative change in the voltage amplitude of each phase after the intersection of the fault phase and the non-fault phase is obtained in the relationship curve, and the coefficient corresponding to the maximum value of the relative change is the second judgment coefficient.

18. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 17, characterized in that: The comparison module obtains a relationship curve between three-phase voltage and transition resistance in a single-phase fault power grid, and the steps include: Construct an equivalent model of single-phase grounding fault in distribution network; Analyzing the single-phase grounding fault equivalent model of the distribution network to obtain the neutral point voltage; The neutral point voltage is inferred to obtain a relationship curve between the phase voltage and transition resistance of the fault phase and the non-fault phase.

19. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 18, characterized in that: The comparison module analyzes the equivalent model of the single-phase grounding fault of the distribution network to obtain the neutral point voltage, specifically: Kirchhoff's law is used to analyze the equivalent model of the single-phase grounding fault of the distribution network to obtain the neutral point voltage.

20. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 18 or 19, characterized in that: The neutral point voltage in the comparison module is: Among them, U Ng is the neutral point voltage, R k is the transition resistance and δ is a constant value.

21. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 18 or 19, characterized in that: The phase voltage of the fault phase in the comparison module is: Among them, U Ag is the phase voltage of the fault phase A, R k is the transition resistance and δ is a constant value.

22. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 18 or 19, characterized in that: The non-fault phases in the comparison module include the fault leading phase B and the fault lagging phase C. The phase voltage of the fault leading phase B is: The phase voltage of the fault lagging phase C is: Among them, U Bg is the phase voltage of the fault leading phase B, U Cg is the phase voltage of the fault lagging phase C, R k is the transition resistance and δ is a constant value.

23. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 16 or 17, characterized in that: The value of the first judgment coefficient α in the comparison module is 0.8229.

24. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 16 or 17, characterized in that: The value of the second judgment coefficient β in the comparison module is 0.

5.

25. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 16, characterized in that: The non-fault phase in the comparison module includes a fault leading phase and a fault lagging phase. In the overcompensated power grid, the preliminary determination that the phase corresponding to the intermediate variation is the fault phase also includes: The phase corresponding to the minimum change is determined as the fault lagging phase, and the phase corresponding to the maximum change is determined as the fault leading phase; In an under-compensated power grid, the preliminary determination that the phase corresponding to the intermediate variation is the fault phase also includes: The phase corresponding to the minimum change is determined as the fault leading phase, and the phase corresponding to the maximum change is determined as the fault lagging phase.

26. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 16 or 25, characterized in that: The non-fault phase includes a fault leading phase and a fault lagging phase. In the overcompensated power grid, the phase corresponding to the minimum change is initially determined to be the fault phase and also includes: The phase corresponding to the intermediate change is determined as the fault lagging phase, and the phase corresponding to the maximum change is determined as the fault leading phase; In an under-compensated power grid, the preliminary determination that the phase corresponding to the minimum change is the fault phase also includes: The phase corresponding to the intermediate change is determined as the fault leading phase, and the phase corresponding to the maximum change is determined as the fault lagging phase.

27. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 16, characterized in that: The acquisition module acquires the maximum change, the intermediate change and the minimum change, and determines whether the maximum change is less than or equal to αE A Previously included: Determine whether the maximum change and the minimum change are greater than or equal to lE A If not, no single-phase grounding fault occurs. If so, further determine whether the maximum change is less than or equal to αE. A , l∈(0,0.1).

28. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 16, characterized in that: The non-fault phase in the determination module includes a fault lagging phase and a fault leading phase, and the determination of whether the fault phase and the non-fault phase satisfy the phase sequence relationship is specifically as follows: Determine whether the fault phase, fault lagging phase and fault leading phase all satisfy the phase sequence relationship.

29. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 20, characterized in that: In the comparison module, the neutral point in the single-phase grounding fault equivalent model of the distribution network is grounded through an arc suppression coil, and each line includes a ground admittance branch.

30. The phase selection system for single-phase grounding fault in power distribution network based on phase voltage according to claim 29, characterized in that: In the comparison module, δ=3ωC-1 / (ωL), wherein ω is the angular frequency, C is the unidirectional total capacitance to the ground, and L is the inductance of the arc suppression coil.

31. A computer device, characterized in that: include: at least one processor and memory; The memory and the processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, the phase selection method for single-phase grounding fault in a power distribution network based on phase voltage as described in any one of claims 1 to 15 is implemented.

32. A computer-readable storage medium, characterized in that: An execution program is stored thereon, and when the execution program is executed, the phase selection method for single-phase grounding fault in a distribution network based on phase voltage as described in any one of claims 1 to 15 is implemented.

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