A power distribution network single-phase ground fault line selection method based on hybrid arc extinction process

Abstract

The application discloses a distribution network single-phase grounding fault line selection method based on a hybrid arc extinguishing process. The waveform change characteristics of the transient and steady state zero sequence voltage and the transient and steady state zero sequence current of each line in the hybrid arc extinguishing process are comprehensively utilized to realize preliminary identification of a fault line, re-determination and line selection result verification. The application can ensure the rapid input of the arc extinguishing device while accurately selecting the grounding fault line, greatly avoiding the problem that the fault information of the traditional fault line selection method is affected by the arc extinguishing. The application has good safety and high reliability in fault line selection.

Description

Technical Field

[0001] This invention relates to the field of single-phase grounding fault detection and protection in distribution networks, specifically a method for selecting the fault line of a single-phase grounding fault in a distribution network based on a hybrid arc extinguishing process. Background Technology

[0002] As the "last mile" for electricity to reach every household, the power distribution network is a vital infrastructure for serving people's livelihoods. Fault arc suppression and fault detection are crucial means to maximize the safety of people's lives and property. In my country, medium-voltage distribution networks mostly use ineffective grounding methods, with single-phase grounding faults accounting for over 80% of all faults, and the grounding current primarily being capacitive current. While low-current grounding systems can continue operating for a period after a single-phase grounding fault, the increasingly complex structure of distribution networks and the continuously increasing capacitive current mean that if an arc that cannot be extinguished persists at the fault point for an extended period, it can lead to the expansion of the fault area, such as multi-point grounding or phase-to-phase short circuits, potentially threatening personal safety and even causing fires.

[0003] Ground fault detection in distribution networks is a crucial means to minimize the fault range, ensure the safety of distribution equipment, provide guidance for fault diagnosis, and improve fault repair efficiency and power supply reliability. In recent years, single-phase ground fault (especially high-resistance ground fault) fault location technology has become a key focus of distribution network fault protection. Existing fault location technologies can be mainly divided into passive and active methods. Passive methods can be further divided into steady-state and transient methods based on signal characteristics. For single-phase ground fault detection, research by domestic and international experts has primarily focused on the fault stage before arc suppression measures are implemented, utilizing the transient steady-state electrical information caused by the fault or constructing location criteria by injecting non-arc suppression signals. Research on fault detection technology for the rapid activation of arc suppression devices after a fault occurs is relatively scarce, thus failing to meet current demands for rapid arc suppression. Furthermore, existing detection methods have poor tolerance to transition resistance, especially since the transient steady-state signals generated by high-resistance ground faults are very weak, hindering signal acquisition and analysis. Simultaneously, the injection of non-arc suppression signals is detrimental to safe grid operation and may affect the self-extinguishing of the ground arc, potentially leading to the development of transient faults into permanent faults. Research has shown that when an arc-extinguishing device aimed at extinguishing fault arcs is put into operation (generating an arc-extinguishing signal), the transient process it induces is very obvious and not easily affected by the magnitude of the transition resistance. Therefore, making full use of the state information of the arc-extinguishing process is the most direct and effective means to improve the reliability of fault detection and ensure the speed of arc extinguishing.

[0004] A search of existing technical fields revealed that Chinese patent application number 202411159030.7, publication number CN118671517A, entitled "A Fault Selection Method for Flexible DC Distribution Network Based on Improved Capsule Network," uses an algorithm to process fault information of current and voltage in each line of a flexible DC distribution network to intelligently determine the faulty line. However, it does not consider the interference of arc suppression in the actual distribution network on the fault information, resulting in low detection accuracy.

[0005] The Chinese patent application number is 202411303011.7, the publication number is CN119165293A, and the patent title is: Fault Selection Method Based on Gram Angle Field and Convolutional Neural Network. This patent collects one-dimensional zero-sequence current time series data of each feeder when a single-phase ground fault occurs in the distribution network to select the fault line. However, it does not consider the influence of three-phase asymmetry of the distribution line on the zero-sequence current of the line, which leads to a decrease in the sensitivity of the fault selection. Summary of the Invention

[0006] Technical Problem: The technical problem to be solved by this invention is to provide a method for selecting single-phase ground faults in distribution networks based on a hybrid arc suppression process. This method should be able to solve the problem that traditional ground fault selection methods cannot adapt to rapid arc suppression and that fault signals are easily affected by the activation of arc suppression devices, thus causing the fault selection method to fail.

[0007] Technical Solution: To solve the above-mentioned technical problems, this invention proposes a method for selecting single-phase grounding faults in distribution networks based on a hybrid arc-extinguishing process. An arc-extinguishing coil and an active arc-extinguishing device are sequentially connected to the neutral point of the distribution network to form a multi-stage arc-extinguishing process, thereby generating transient steady-state information of the arc-extinguishing process and realizing accurate judgment of fault feeders based on the hybrid arc-extinguishing process.

[0008] A method for locating single-phase ground faults in a distribution network based on a hybrid arc-extinguishing process includes the following steps:

[0009] S1: When the distribution network is operating normally, measure the steady-state zero-sequence voltage value and record it as follows: The steady-state zero-sequence current value of line n is measured and denoted as .

[0010] S2: In t c After a ground fault occurs in the distribution network, the steady-state zero-sequence voltage value is measured and recorded as follows: The steady-state zero-sequence current value of line n is measured and denoted as .

[0011] S3: At time t0, the fully compensated arc suppression coil is connected to the neutral point of the distribution network. The theoretical expression for the transient zero-sequence current waveform of line n is 3i. 0n_tra (t) is:

[0012]

[0013] In the above formula, C n G n Here are the total distributed capacitance and total distributed conductance to ground of line n; u 0_tra (t) represents the system transient zero-sequence voltage after the fully compensated arc suppression coil is switched on;

[0014] S4: Record the actual value 3i of the transient zero-sequence current of line n. 0Cn_tra (t), compare 3i 0Cn_tra (t) and 3i 0n_tra The magnitude of (t) is used to preliminarily determine whether line n has a fault, including the following steps:

[0015] S4-1: If 3i 0Cn_tra (t0)=3i 0n_tra If (t0), then it can be preliminarily determined that line n is normal;

[0016] S4-2: If 3i 0Cn_tra (t0)≠3i 0n_tra If (t0), then proceed to step S4-3;

[0017] S4-3: When u 0_tra When (t0)>0, 3i 0Cn_tra (t0)>3i 0n_tra (t0); or when u 0_tra When (t0) < 0, 3i 0Cn_tra (t0)<3i 0n_tra If (t0), then a preliminary judgment is made that line n is faulty;

[0018] S5: At time t1, connect the active arc suppression device and the fully compensated arc suppression coil in parallel to the neutral point of the distribution network, record the transient zero-sequence voltage waveform and the transient zero-sequence current waveform of line n, and determine the faulty line based on the difference in the attenuation direction of the zero-sequence voltage and zero-sequence current. The steps are as follows:

[0019] S5-1: If the transient zero-sequence voltage and the transient zero-sequence current waveform of line n have the same decay direction, and the transient zero-sequence current decay direction and the transient zero-sequence voltage are the same on the other lines except line n, then line n is further determined to be a faulty line.

[0020] S5-2: If the attenuation directions of the transient zero-sequence voltage and the transient zero-sequence current waveform of line n are opposite, then line n is further determined to be a normal line.

[0021] S6: After the grounding current is completely suppressed to 0, measure the steady-state zero-sequence voltage value and record it as follows. The steady-state zero-sequence current value of line n is measured and denoted as .

[0022] S7: Based on the measurement Construct a steady-state fault selection criterion Y to verify the accuracy of the fault lines selected in steps S4 and S5.

[0023] Furthermore, the time t0 at which the fully compensated arc suppression coil is connected to the neutral point of the distribution network in step S3 satisfies:

[0024] t0 = t c +5T f Formula 2

[0025] In the above formula, T f It is the power frequency period, and T f =0.02s.

[0026] Furthermore, the time t1 at which the fully compensated arc suppression coil is connected to the neutral point of the distribution network in step S5 satisfies:

[0027] t1 = t0 + 6τ (Equation 3)

[0028] In the above formula, τ is the time constant corresponding to the transient zero-sequence current in step S4.

[0029] Furthermore, in step S7, the steady-state fault selection criterion Y is:

[0030]

[0031] In the above formula, Y i Y is the total distributed admittance to ground of line n. Σ R is the total ground-distributed admittance of the system. E For grounding resistance; the textual description of the steady-state fault selection criterion Y is: based on measurement. When the calculation formula The total distributed admittance to ground Y of line n is equal to and equal to that of line n. n When n is a normal line, the calculation formula is used. Not equal, and only one The total distributed admittance to ground of line n is equal to Y. n If the condition is met, then line n is determined to be a faulty line.

[0032] Beneficial Effects: The single-phase grounding fault location method for distribution networks based on a hybrid arc suppression process proposed in this invention can accurately identify the faulty line while the grounding current is fully compensated after a single-phase grounding fault occurs in the distribution network. This method ensures that fault arc suppression and fault location can be carried out simultaneously, and can accurately determine the specific line where the grounding fault occurred while reliably suppressing the grounding current. Attached Figure Description

[0033] Figure 1A schematic diagram of equivalent calculation for fault location in a multi-feeder distribution network;

[0034] Figure 2 The transient zero-sequence voltage and transient zero-sequence current waveforms after the arc suppression coil is put into operation (grounding resistance is set to 20 ohms);

[0035] Figure 3 The transient zero-sequence voltage and transient zero-sequence current waveforms after the arc suppression coil is put into operation (grounding resistance is set to 2000 ohms);

[0036] Figure 4 The waveforms of transient zero-sequence voltage and transient zero-sequence current of each line after the active arc suppression device is put into operation. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously,

[0038] The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0039] Appendix Figure 1 This is a schematic diagram illustrating the equivalent calculation for fault location in a multi-feeder distribution network. The distribution network has n lines, C... nA C nB C nC These are the distributed capacitances to ground of phases A, B, and C of line n, respectively; G nA G nB G nC These are the ground-distributed conductivities of phases A, B, and C of line n, respectively, R. E Let be the grounding resistance. When a phase-A ground fault occurs on the nth line of the distribution network, a method for selecting the line for a single-phase ground fault in the distribution network based on a hybrid arc suppression process is as follows.

[0040] Step S1: When the distribution network is operating normally, measure the steady-state zero-sequence voltage value and record it as follows: The steady-state zero-sequence current value of line n is measured and denoted as .

[0041] Step S2: At t c After a ground fault occurs in the distribution network, the steady-state zero-sequence voltage value is measured and recorded as follows: The steady-state zero-sequence current value of line n is measured and denoted as .

[0042] Step S3: At time t0, connect the fully compensated arc suppression coil to the neutral point of the distribution network. The theoretical expression for the transient zero-sequence current waveform of line n is 3i. 0n_tra(t) is:

[0043]

[0044] In the above formula, C n G n Here are the total distributed capacitance and total distributed conductance to ground of line n; u 0_tra (t) represents the system transient zero-sequence voltage after the fully compensated arc suppression coil is switched on; the time t0 when the fully compensated arc suppression coil is connected to the neutral point of the distribution network satisfies:

[0045] t0 = t c +5T f Formula 6

[0046] In the above formula, T f It is the power frequency period, and T f =0.02s.

[0047] Step S4: Record the actual value 3i of the transient zero-sequence current of line n. 0Cn_tra (t), compare 3i 0Cn_tra (t) and 3i 0n_tra The magnitude of (t) is used to preliminarily determine whether line n has a fault, including the following steps:

[0048] Step S4-1: If 3i 0Cn_tra (t0)=3i 0n_tra If (t0), then it can be preliminarily determined that line n is normal;

[0049] Step S4-2: If 3i 0Cn_tra (t0)≠3i 0n_tra If (t0), then proceed to step S4-3;

[0050] Step S4-3: When u 0_tra When (t0)>0, 3i 0Cn_tra (t0)>3i 0n_tra (t0); or when u 0_tra When (t0) < 0, 3i 0Cn_tra (t0)<3i 0n_tra If (t0), then a preliminary judgment is made that line n is faulty;

[0051] Step S5: At time t1, connect the active arc suppression device and the fully compensated arc suppression coil in parallel to the neutral point of the distribution network. The time t1 when the fully compensated arc suppression coil is connected to the neutral point of the distribution network satisfies:

[0052] t1 = t0 + 6τ (Equation 7)

[0053] In the above formula, τ is the time constant corresponding to the transient zero-sequence current in step S4.

[0054] Record the transient zero-sequence voltage waveform and the transient zero-sequence current waveform of line n. Determine the faulty line based on the difference in the decay direction of the zero-sequence voltage and zero-sequence current. The steps include the following:

[0055] Step S5-1: If the transient zero-sequence voltage and the transient zero-sequence current waveform of line n have the same decay direction, and the transient zero-sequence current decay direction and the transient zero-sequence voltage are the same on the other lines except line n, then line n is further determined to be the faulty line.

[0056] Step S5-2: If the attenuation directions of the transient zero-sequence voltage and the transient zero-sequence current waveform of line n are opposite, then line n is further determined to be a normal line.

[0057] Step S6: After the grounding current is completely suppressed to 0, measure the steady-state zero-sequence voltage value and record it as follows. The steady-state zero-sequence current value of line n is measured and denoted as .

[0058] Step S7: Based on the measurement The steady-state fault selection criterion Υ is constructed as follows:

[0059]

[0060] In the above formula, Y i Y is the total distributed admittance to ground of line n. Σ R is the total ground-distributed admittance of the system. E For grounding resistance; the textual description of the steady-state fault selection criterion Y is: based on measurement. When the calculation formula The total distributed admittance to ground Y of line n is equal to and equal to that of line n. n When n is a normal line, the calculation formula is used. Not equal, and only one The total distributed admittance to ground of line n is equal to Y. n If the condition is met, then line n is determined to be a faulty line.

[0061] In the appendix Figure 1 Based on this, the proposed method for selecting single-phase grounding faults in distribution networks based on a hybrid arc suppression process was verified using MATLAB / Simulink simulation. The parameters of each line in the distribution network during the simulation are shown in Table 1. The equivalent inductance of the fully compensated arc suppression coil is L = 0.2528H, and the equivalent output current of the active arc suppression device is... The ground fault is located on phase A of line 3, and the grounding resistance is R. E The resistance was set to 20Ω and 2000Ω respectively. The simulation results of the fault location method based on hybrid arc suppression are detailed in the appendix. Figure 2 Appendix Figure 3 Appendix Figure 4 And Tables 2, 3, and 4.

[0062] Table 1. Ground distribution parameters of distribution network lines

[0063]

[0064] Table 2 When R E Preliminary line selection results at Ω=20Ω

[0065]

[0066] Table 3 When R E Preliminary line selection results at Ω=2000

[0067]

[0068] Table 4 Verification of Route Selection Results Based on Steady-State Information

[0069]

[0070]

[0071] From the appendix Figure 2 As shown in Table 2, when the grounding resistance R E When the Ω is 20Ω (after the fully compensated arc suppression coil is engaged), the zero-sequence current of line 1 satisfies: i 0C1_tra (0.142)=i 01_tra (0.142) = -0.702; The zero-sequence current of line 2 satisfies: i 0C2_tra (0.142)=i 02_tra (0.142) = -1.361; The zero-sequence current of line 3 satisfies: i 0C3_tra (0.142)=29.503, i 03_tra (0.142) = -0.91. According to the line selection method described in step S4, if 3i 0Cn_tra (t0)=3i 0n_tra If (t0), then it can be preliminarily determined that line n is normal. Therefore, it can be preliminarily determined that lines 1 and 2 are normal, while line 3 has a grounding fault.

[0072] Similarly, by appendix Figure 3 As shown in Table 3, when the grounding resistance R E When the Ω is 2000Ω (after the fully compensated arc suppression coil is engaged), the zero-sequence current of line 1 satisfies: i 0C1_tra (0.152)=i 01_tra (0.152) = -2.080; The zero-sequence current of line 2 satisfies: i 0C2_tra (0.152)=i 02_tra(0.152) = -4.120; The zero-sequence current of line 3 satisfies: i 0C3_tra (0.152) = -3.168, i 03_tra (0.152) = -2.425. Additionally, u 0_tra (0.152) = -2759.789 > 0, i 0C3_tra (0.152) 03_tra (0.152). Therefore, it is preliminarily determined that line 1 and line 2 are normal, while line 3 has a grounding fault.

[0073] From the appendix Figure 4 It can be seen that when the grounding resistance R E When the voltage is 2000Ω (after the active arc suppression device is activated), the transient zero-sequence voltage of the system decays downwards. Among the three lines, only the transient zero-sequence current decays in line 3 in the same direction as the transient zero-sequence voltage, both downwards. The transient zero-sequence current decays in lines 1 and 2 in the opposite direction to the transient zero-sequence voltage, both upwards. According to the fault selection method described in step S5, the faulty line is determined to be line 3, while lines 1 and 2 are normal lines.

[0074] As shown in Table 4, when the grounding resistance R E When the current is 20Ω, line 1 satisfies: ∠88.969°; Line 2 satisfies: Line 3 satisfies: Based on the fault selection criteria described in step S7, the faulty line can be re-identified as line 3. Similarly, when the grounding resistance R... E When the current is 2000Ω, line 1 satisfies: Line 2 satisfies: Line 3 satisfies: Based on the fault selection criteria described in step S7, the faulty line can be identified as line 3 again.​

Claims

1. A method for selecting the fault location of a single-phase grounding fault in a distribution network based on a hybrid arc-extinguishing process, characterized in that, The selection of the faulty line is achieved by utilizing the differences in the metastable zero-sequence voltage and zero-sequence current of each distribution line during the mixed arc suppression process, including the following steps: S1: When the distribution network is operating normally, measure the steady-state zero-sequence voltage value and record it as follows: The steady-state zero-sequence current value of line n is measured and denoted as . S2: In t c After a ground fault occurs in the distribution network, the steady-state zero-sequence voltage value is measured and recorded as follows: The steady-state zero-sequence current value of line n is measured and denoted as . S3: At time t0, the fully compensated arc suppression coil is connected to the neutral point of the distribution network. The theoretical expression for the transient zero-sequence current waveform of line n is 3i. 0n_tra (t) is: In the above formula, C n G n Here are the total distributed capacitance and total distributed conductance to ground of line n; u 0_tra (t) represents the system transient zero-sequence voltage after the fully compensated arc suppression coil is switched on; S4: Record the actual value 3i of the transient zero-sequence current of line n. 0Cn_tra (t), compare 3i 0Cn_tra (t) and 3i 0n_tra The magnitude of (t) is used to preliminarily determine whether line n has a fault, including the following steps: S4-1: If 3i 0Cn_tra (t0)=3i 0n_tra If (t0), then it can be preliminarily determined that line n is normal; S4-2: If 3i 0Cn_tra (t0)≠3i 0n_tra If (t0), then proceed to step S4-3; S4-3: When u 0_tra When (t0)>0, 3i 0Cn_tra (t0)>3i 0n_tra (t0); or when u 0_tra When (t0) < 0, 3i 0Cn_tra (t0)<3i 0n_tra If (t0), then a preliminary judgment is made that line n is faulty; S5: At time t1, connect the active arc suppression device and the fully compensated arc suppression coil in parallel to the neutral point of the distribution network, record the transient zero-sequence voltage waveform and the transient zero-sequence current waveform of line n, and determine the faulty line based on the difference in the attenuation direction of the zero-sequence voltage and zero-sequence current. The steps are as follows: S5-1: If the transient zero-sequence voltage and the transient zero-sequence current waveform of line n have the same decay direction, and the transient zero-sequence current decay direction and the transient zero-sequence voltage are the same on the other lines except line n, then line n is further determined to be a faulty line. S5-2: If the attenuation directions of the transient zero-sequence voltage and the transient zero-sequence current waveform of line n are opposite, then line n is further determined to be a normal line. S6: After the grounding current is completely suppressed to 0, measure the steady-state zero-sequence voltage value and record it as follows. The steady-state zero-sequence current value of line n is measured and denoted as . S7: Based on the measurement Construct a steady-state fault selection criterion Y to verify the accuracy of the fault lines selected in steps S4 and S5.

2. The method for selecting a single-phase grounding fault in a distribution network based on a hybrid arc-extinguishing process according to claim 1, characterized in that, In step S3, the time t0 when the fully compensated arc suppression coil is connected to the neutral point of the distribution network satisfies: t0 = t c +5T f Formula 2 In the above formula, T f It is the power frequency period, and T f =0.02s.

3. The method for selecting a single-phase grounding fault in a distribution network based on a hybrid arc-extinguishing process according to claim 1, characterized in that, In step S5, the time t1 at which the fully compensated arc suppression coil is connected to the neutral point of the distribution network satisfies the following: t1 = t0 + 6τ (Equation 3) In the above formula, τ is the time constant corresponding to the transient zero-sequence current in step S4.

4. The method for selecting a single-phase grounding fault in a distribution network based on a hybrid arc-extinguishing process according to claim 1, characterized in that, In step S7, the steady-state fault selection criterion Y is: In the above formula, Y i Y is the total distributed admittance to ground of line n. Σ R is the total ground-distributed admittance of the system. E For grounding resistance; the textual description of the steady-state fault selection criterion Y is: based on measurement. When the calculation formula The total distributed admittance Y to ground of line n is equal to and equal to that of line n. n When n is a normal line, it is determined that line n is a normal line. When the calculation formula Not equal, and only one The total distributed admittance to ground of line n is equal to Y. n If the condition is met, then line n is determined to be a faulty line.

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