A ground fault line selection method and device based on double-ended zero sequence voltage

Abstract

The application discloses a grounding fault line selection method and device based on double-end zero sequence voltage. The method comprises the following steps: monitoring the bus zero sequence voltage corresponding to the bus in real time; when the bus zero sequence voltage exceeds the starting voltage threshold, acquiring the upstream zero sequence voltage corresponding to the bus and the downstream zero sequence voltage corresponding to each feeder; respectively calculating the absolute value of the ratio between each downstream zero sequence voltage and the upstream zero sequence voltage to obtain the zero sequence voltage amplitude ratio; and if the zero sequence voltage amplitude ratio is greater than the preset fault threshold, determining that the single-phase broken-line power side grounding fault occurs in the feeder to which the zero sequence voltage amplitude belongs. Thus, the technical problem that the existing grounding fault line selection method cannot be applied to the broken-line grounding fault and is difficult to comprehensively and accurately select the line is solved, and the fault line can still be accurately selected under the influence of the fault position and transition resistance.

Description

Technical Field

[0001] This invention relates to the field of ground fault location technology, and in particular to a ground fault location method and apparatus based on double-ended zero-sequence voltage. Background Technology

[0002] With the widespread use of overhead insulated wires in power distribution networks, wire breakage faults caused by lightning strikes, mechanical forces, and other factors have become one of the most common types of faults in power distribution networks. These wire breakage faults include various types, such as ground faults caused by wire breaks, which can easily lead to forest fires, electric shocks to people and livestock, and other accidents. Therefore, accurately selecting the fault line for ground faults caused by wire breaks is crucial for maintaining the normal and safe operation of the power grid.

[0003] Currently, line breakage faults are mainly handled through manual line inspection, which may suffer from problems such as delayed information acquisition, low efficiency, and low accuracy. Existing technologies for grounding faults include methods such as using negative sequence current characteristics for fault selection or fault analysis of line breakage-to-ground faults. For example, analyzing the voltage at the break point only considers the case where both sides of the break are suspended, without further research on the voltage characteristics when a grounding fault occurs at the break point; using the neutral point voltage offset phase angle to identify line breakage-to-ground faults only has grounding side identification capability and cannot achieve fault selection; using negative sequence current characteristics to identify line breakage-to-power supply grounding faults is greatly affected by load; and when selecting faults for line breakage-to-power supply side grounding faults, the impact of transition resistance is insufficiently considered, making fault selection impossible in high-resistance grounding situations.

[0004] However, since single-phase open circuit plus power supply side grounding fault is fundamentally different from grounding fault and single-phase open circuit without grounding fault, the existing grounding fault line selection method cannot be applied to open circuit grounding fault, and the above line selection scheme is difficult to select the line comprehensively and accurately. Summary of the Invention

[0005] This invention provides a ground fault line selection method and device based on double-ended zero-sequence voltage, which solves the technical problem that existing ground fault line selection methods cannot be applied to open-circuit ground faults because there is an essential difference between single-phase open-circuit ground faults and ground faults and single-phase open-circuit ungrounded faults. This makes it difficult to select the line comprehensively and accurately.

[0006] This invention provides a ground fault location method based on dual-terminal zero-sequence voltage, relating to an arc suppression coil grounding system. The arc suppression coil grounding system includes a busbar and multiple feeders connected to the busbar. The method includes:

[0007] Real-time monitoring of the zero-sequence voltage of the bus corresponding to the bus;

[0008] When the zero-sequence voltage of the bus exceeds the start-up voltage threshold, the upstream zero-sequence voltage corresponding to the bus and the downstream zero-sequence voltage corresponding to each feeder are obtained.

[0009] Calculate the absolute value of the ratio between each of the downstream zero-sequence voltages and the upstream zero-sequence voltages to obtain the zero-sequence voltage amplitude ratio;

[0010] If the zero-sequence voltage amplitude ratio is greater than the preset fault threshold, it is determined that a single-phase open-circuit ground fault has occurred on the power supply side of the feeder to which the zero-sequence voltage amplitude belongs.

[0011] Optionally, the step of obtaining the upstream zero-sequence voltage corresponding to the bus and the downstream zero-sequence voltage corresponding to each of the feeders when the bus zero-sequence voltage exceeds the start-up voltage threshold includes:

[0012] When the zero-sequence voltage of the bus exceeds the start-up voltage threshold, the upstream zero-sequence equivalent impedance, transition resistance, and downstream zero-sequence equivalent impedance of each feeder are obtained.

[0013] Calculate the sum of the upstream zero-sequence equivalent impedance and the transition resistance;

[0014] Calculate the sum, the first multiplication between the downstream zero-sequence equivalent impedance and the first constant to obtain the downstream zero-sequence voltage corresponding to each feeder;

[0015] The upstream zero-sequence voltage is determined based on the upstream zero-sequence equivalent impedance, each of the downstream zero-sequence equivalent impedances, and the transition resistance.

[0016] Optionally, the step of determining the upstream zero-sequence voltage based on the upstream zero-sequence equivalent impedance, the downstream zero-sequence equivalent impedance, and the transition resistance includes:

[0017] Calculate the second multiplication value between each of the downstream zero-sequence equivalent impedances and the second constant;

[0018] Calculate the third multiplication factor between the transition resistance and the first constant;

[0019] Calculate the first difference between each of the second multipliers and the third multiplier;

[0020] The upstream zero-sequence voltage is obtained by multiplying each of the first differences by the upstream zero-sequence equivalent impedance.

[0021] Optionally, before performing the step of using the product of each of the first differences and the upstream zero-sequence equivalent impedance as the upstream zero-sequence voltage, the method further includes:

[0022] Obtain the downstream negative sequence impedance corresponding to each of the feed lines;

[0023] The sum of each of the first differences and the downstream negative sequence impedance is calculated as a new first difference.

[0024] Optionally, the method further includes:

[0025] If the zero-sequence voltage of the bus does not exceed the starting voltage threshold, then proceed to the step of real-time monitoring of the zero-sequence voltage of the bus corresponding to the bus.

[0026] If the zero-sequence voltage amplitude ratio is less than or equal to a preset fault threshold, it is determined that the feeder to which the zero-sequence voltage amplitude belongs has not experienced a single-phase open-circuit power supply side grounding fault.

[0027] This invention also provides a ground fault location device based on dual-terminal zero-sequence voltage, relating to an arc suppression coil grounding system. The arc suppression coil grounding system includes a busbar and multiple feeders connected to the busbar. The device includes:

[0028] The monitoring module is used to monitor the zero-sequence voltage of the bus corresponding to the bus in real time.

[0029] The zero-sequence voltage acquisition module is used to acquire the upstream zero-sequence voltage corresponding to the bus and the downstream zero-sequence voltage corresponding to each feeder when the zero-sequence voltage of the bus exceeds the start-up voltage threshold.

[0030] The amplitude ratio calculation module is used to calculate the absolute value of the ratio between each of the downstream zero-sequence voltages and the upstream zero-sequence voltages to obtain the zero-sequence voltage amplitude ratio.

[0031] The fault determination module is used to determine that a single-phase open-circuit power supply side grounding fault has occurred in the feeder to which the zero-sequence voltage amplitude belongs if the zero-sequence voltage amplitude ratio is greater than a preset fault threshold.

[0032] Optionally, the zero-sequence voltage acquisition module includes:

[0033] The impedance detection submodule is used to acquire the upstream zero-sequence equivalent impedance, transition resistance, and downstream zero-sequence equivalent impedance of each feeder when the zero-sequence voltage of the bus exceeds the start-up voltage threshold.

[0034] The sum calculation submodule is used to calculate the sum between the upstream zero-sequence equivalent impedance and the transition resistance;

[0035] The downstream zero-sequence voltage determination submodule is used to calculate the sum, the first multiplication between the downstream zero-sequence equivalent impedance and the first constant, respectively, to obtain the downstream zero-sequence voltage corresponding to each feeder.

[0036] The upstream zero-sequence voltage determination submodule is used to determine the upstream zero-sequence voltage based on the upstream zero-sequence equivalent impedance, each of the downstream zero-sequence equivalent impedances, and the transition resistance.

[0037] Optionally, the upstream zero-sequence voltage determination submodule is specifically used for:

[0038] Calculate the second multiplication value between each of the downstream zero-sequence equivalent impedances and the second constant;

[0039] Calculate the third multiplication factor between the transition resistance and the first constant;

[0040] Calculate the first difference between each of the second multipliers and the third multiplier;

[0041] The upstream zero-sequence voltage is obtained by multiplying each of the first differences by the upstream zero-sequence equivalent impedance.

[0042] Optionally, before the upstream zero-sequence voltage determination submodule is specifically configured to perform the step of using the product between each of the first differences and the upstream zero-sequence equivalent impedance as the upstream zero-sequence voltage, it is further configured to:

[0043] Obtain the downstream negative sequence impedance corresponding to each of the feed lines;

[0044] The sum of each of the first differences and the downstream negative sequence impedance is calculated as a new first difference.

[0045] Optionally, the device further includes:

[0046] The loop module is used to jump to the step of real-time monitoring of the zero-sequence voltage of the bus if the zero-sequence voltage of the bus does not exceed the starting voltage threshold.

[0047] The fault denial module is used to determine that no single-phase open-circuit power supply side grounding fault has occurred on the feeder to which the zero-sequence voltage amplitude belongs if the zero-sequence voltage amplitude ratio is less than or equal to a preset fault threshold.

[0048] As can be seen from the above technical solutions, the present invention has the following advantages:

[0049] This invention monitors the zero-sequence voltage of the busbar in real time. When the zero-sequence voltage exceeds the starting voltage threshold, it acquires the upstream zero-sequence voltage of the busbar and the downstream zero-sequence voltage of each feeder. It then calculates the absolute value of the ratio between each downstream zero-sequence voltage and the upstream zero-sequence voltage to obtain the zero-sequence voltage amplitude ratio. If the zero-sequence voltage amplitude ratio is greater than a preset fault threshold, it determines that the feeder to which the zero-sequence voltage amplitude belongs has experienced a single-phase open-circuit ground fault on the power supply side. This solves the technical problem that existing ground fault selection methods cannot be applied to open-circuit ground faults, making it difficult to comprehensively and accurately select the faulty line. Even under the influence of fault location and transition resistance, it can still accurately select the faulty line. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1 The flowchart illustrates the steps of a ground fault location method based on dual-terminal zero-sequence voltage according to Embodiment 1 of the present invention.

[0052] Figure 2 This is a schematic diagram of the circuit topology of an arc suppression coil grounding system according to an embodiment of the present invention;

[0053] Figure 3 This is a flowchart illustrating the steps of a ground fault location method based on dual-terminal zero-sequence voltage according to Embodiment 2 of the present invention.

[0054] Figure 4 This is a composite sequence network diagram of a single-phase open circuit plus power supply side grounding fault in an arc suppression coil grounding system according to an embodiment of the present invention;

[0055] Figure 5 This is a schematic diagram illustrating the variation of the zero-sequence voltage amplitude ratio with grounding resistance according to an embodiment of the present invention;

[0056] Figure 6 A schematic flowchart of a ground fault selection method based on dual-terminal zero-sequence voltage provided in an embodiment of the present invention;

[0057] Figure 7 A schematic diagram of a simulation model of a 10kV arc suppression coil grounding system with multiple circuits on the same busbar and grounding complex fault provided in an embodiment of the present invention;

[0058] Figure 8 This is a structural block diagram of a ground fault location device based on dual-terminal zero-sequence voltage provided in Embodiment 3 of the present invention. Detailed Implementation

[0059] This invention provides a ground fault location method and apparatus based on dual-terminal zero-sequence voltage. It addresses the technical problem that existing ground fault location methods cannot be applied to open-circuit ground faults due to the fundamental differences between single-phase open-circuit ground faults and ground faults, as well as single-phase open-circuit ungrounded faults, making it difficult to locate faults comprehensively and accurately.

[0060] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0061] Please see Figure 1 , Figure 1 This is a flowchart illustrating the steps of a ground fault location method based on dual-terminal zero-sequence voltage, as provided in Embodiment 1 of the present invention.

[0062] This invention provides a ground fault location method based on dual-terminal zero-sequence voltage, relating to an arc suppression coil grounding system. The arc suppression coil grounding system includes a busbar and multiple feeders connected to the busbar. The method includes:

[0063] Step 101: Monitor the zero-sequence voltage of the bus corresponding to the bus in real time;

[0064] In this embodiment of the invention, the circuit topology diagram of the arc suppression coil grounding system can be as follows: Figure 2 As shown, T0 is the grounding transformer, T1 is the system-side main transformer, and C... S For bus stray capacitance, L p This is an arc suppression coil. The line adopts a π-type equivalent model, and a single-phase open circuit and a ground fault on the power supply side occur in feeder n. T0 is the grounding transformer, T1 is the system-side main transformer, and C... S For bus stray capacitance, L p For the arc suppression coil, the circuit adopts a π-type equivalent model.

[0065] In this embodiment, the zero-sequence voltage of the bus can be detected in real time, and this can be used as a criterion to determine whether to perform fault line selection.

[0066] Zero-sequence voltage refers to the voltage generated when a ground fault occurs in a directly grounded neutral system or when a single-phase ground fault occurs in a non-directly grounded system.

[0067] Step 102: When the bus zero-sequence voltage exceeds the start-up voltage threshold, obtain the upstream zero-sequence voltage corresponding to the bus and the downstream zero-sequence voltage corresponding to each feeder.

[0068] In practical implementation, if a ground fault occurs in a three-phase circuit, the zero-sequence voltage of the bus will increase. If the zero-sequence voltage of the bus exceeds the starting voltage threshold, it indicates that a single-phase open circuit and a ground fault on the power supply side may have occurred in the feeder associated with the bus. At this time, the upstream zero-sequence voltage corresponding to the bus and the downstream zero-sequence voltage corresponding to each feeder can be obtained.

[0069] It should be noted that the upstream zero-sequence voltage refers to the bus-side voltage, i.e. Figure 2 The zero-sequence voltage of the M-side busbar, and the downstream zero-sequence voltage refer to the voltage on the feeder side, i.e. Figure 2 The zero-sequence voltage of the N-side bus.

[0070] Step 103: Calculate the absolute value of the ratio between each downstream zero-sequence voltage and the upstream zero-sequence voltage to obtain the zero-sequence voltage amplitude ratio;

[0071] In this embodiment of the invention, the zero-sequence voltage amplitude ratio is obtained by calculating the ratio between the downstream zero-sequence voltage of each feeder and the upstream zero-sequence voltage of its bus.

[0072] It should be noted that the zero-sequence voltage amplitude ratio is used to measure the proportion of the zero-sequence voltage of each feeder caused by a single-phase open circuit and a ground fault on the power supply side to the zero-sequence voltage of the bus. When the grounding resistance R on the power supply side... f When K is small n It mainly depends on the zero-sequence admittance upstream and downstream of the fault; as the transition resistance changes, K... n The value did not change significantly.

[0073] Step 104: If the zero-sequence voltage amplitude ratio is greater than the preset fault threshold, it is determined that a single-phase open circuit power supply side ground fault has occurred in the feeder to which the zero-sequence voltage amplitude belongs.

[0074] After calculating the zero-sequence voltage amplitude ratio, the zero-sequence voltage amplitude ratio can be further compared with the preset fault threshold. If any zero-sequence voltage amplitude ratio is greater than the preset fault threshold, it indicates that a single-phase open circuit power supply side ground fault has occurred in the feeder to which the zero-sequence voltage amplitude belongs. At this time, it can be marked as a faulty line and will be dealt with further.

[0075] If the zero-sequence voltage amplitude ratio is not greater than the preset fault threshold, it indicates that there is no single-phase open circuit grounding fault on the power supply side of its feeder.

[0076] In this embodiment of the invention, by real-time monitoring of the zero-sequence voltage of the bus corresponding to the bus, when the zero-sequence voltage of the bus exceeds the starting voltage threshold, the upstream zero-sequence voltage corresponding to the bus and the downstream zero-sequence voltage corresponding to each feeder are obtained. The absolute value of the ratio between each downstream zero-sequence voltage and the upstream zero-sequence voltage is calculated to obtain the zero-sequence voltage amplitude ratio. If the zero-sequence voltage amplitude ratio is greater than a preset fault threshold, it is determined that a single-phase open-circuit ground fault has occurred on the power supply side of the feeder to which the zero-sequence voltage amplitude belongs. This solves the technical problem that existing ground fault line selection methods cannot be applied to open-circuit ground faults, making it difficult to select the line comprehensively and accurately. Even under the influence of fault location and transition resistance, the faulty line can still be accurately selected.

[0077] Please see Figure 3, Figure 3 This is a flowchart illustrating the steps of a ground fault location method based on dual-terminal zero-sequence voltage, as provided in Embodiment 2 of the present invention.

[0078] This invention provides a ground fault location method based on dual-terminal zero-sequence voltage, relating to an arc suppression coil grounding system. The arc suppression coil grounding system includes a busbar and multiple feeders connected to the busbar. The method includes:

[0079] Step 201: Monitor the zero-sequence voltage of the bus corresponding to the bus in real time;

[0080] In this embodiment of the invention, the specific implementation process of step 201 is similar to that of step 101, and will not be repeated here.

[0081] Step 202: When the bus zero-sequence voltage exceeds the start-up voltage threshold, obtain the upstream zero-sequence equivalent impedance, transition resistance, and downstream zero-sequence equivalent impedance of each feeder corresponding to the bus.

[0082] When the bus zero-sequence voltage exceeds the start-up voltage threshold, it indicates that a ground fault has occurred. Further information can be obtained about the upstream zero-sequence equivalent impedance, transition resistance, and downstream zero-sequence equivalent impedance of each feeder.

[0083] When a single-phase open-circuit fault plus a ground fault occurs in the arc suppression coil grounding system, the fault location device can use zero-sequence voltage over-limit start. When the effective value of the bus zero-sequence voltage exceeds the set start setting value, fault location begins. Therefore, the start criterion can be set as follows:

[0084] U M(0) >U set

[0085] The starting value can be set according to the maximum zero-sequence voltage that occurs when there is three-phase imbalance. The zero-sequence voltage setting value can be taken as 10% of the phase voltage. For a 10kV distribution network, U set =577V.

[0086] In the specific implementation, we can first follow Figure 2 The circuit structure diagram in the image is analyzed using the symmetrical component method to determine the boundary conditions at the break point:

[0087]

[0088] in, This represents the positive sequence current at the point of disconnection. This is the negative sequence current at the point of disconnection. This is the zero-sequence current at the point of disconnection. This is the positive sequence voltage at the point of disconnection. This is the negative sequence voltage at the point of disconnection. This is the zero-sequence voltage at the point of disconnection.

[0089] The boundary conditions at the grounding point are:

[0090]

[0091] in, This is the positive sequence grounding current at the grounding point. This refers to the negative sequence current at the grounding point. R is the zero-sequence current at the grounding point. f This is the grounding resistance.

[0092] Based on the boundary conditions, the composite sequence network diagram of a single-phase open-circuit fault plus power supply side grounding fault in the arc suppression coil grounding system is as follows: Figure 4 As shown in the figure. Z is the equivalent potential of the positive-sequence network. up(1) Z up(2) Z up(0) Z represents the positive, negative, and zero-sequence equivalent impedance upstream of the fault point. down(1) Z down(2) Z down(0) The positive, negative, and zero-sequence equivalent impedances downstream of the fault point. These are the positive, negative, and zero-sequence voltages upstream of the fault point, i.e., the voltage at the point of disconnection. These are the positive, negative, and zero-sequence voltages downstream of the fault, i.e., the voltage at the grounding point. These are the positive, negative, and zero-sequence currents downstream of the fault.

[0093] In this embodiment, the zero-sequence voltages upstream and downstream of the fault point can be obtained by solving the composite sequence network diagram. Since the line impedance is much smaller than the capacitive reactance to ground, the voltage on the line impedance can be ignored. Thus, the zero-sequence voltages at the M and Nn side buses are the zero-sequence voltages upstream and downstream of the fault point.

[0094] Step 203: Calculate the sum of the upstream zero-sequence equivalent impedance and the transition resistance;

[0095] Step 204: Calculate the sum, the first multiplication between the downstream zero-sequence equivalent impedance and the first constant to obtain the downstream zero-sequence voltage corresponding to each feeder.

[0096] In this embodiment, the zero-sequence voltage U downstream of the nth feeder of the N-side bus is Nn(0) It can be calculated in the following way:

[0097] U Nn(0) =3Z down(0) (Z up(0) +R f )

[0098] The first constant can be 3.

[0099] Step 205: Determine the upstream zero-sequence voltage based on the upstream zero-sequence equivalent impedance, the downstream zero-sequence equivalent impedances, and the transition resistance.

[0100] Optionally, step 205 may include the following sub-steps:

[0101] Calculate the second multiplication value between each downstream zero-sequence equivalent impedance and the second constant;

[0102] Calculate the third multiplication factor between the transition resistance and the first constant;

[0103] Calculate the first difference between each second and third multiplication value;

[0104] The upstream zero-sequence voltage is obtained by multiplying each first difference value by the upstream zero-sequence equivalent impedance.

[0105] In this embodiment, the zero-sequence impedance downstream of the fault point is mainly the capacitive reactance to ground since there is no load present, relative to the negative-sequence impedance Z. down(0) It is much larger, therefore, the upstream zero-sequence voltage U of the M-side bus is... M(0) The calculation can be performed in the following ways:

[0106] U M(0) =Z up(0) (2Z down(0) -3R f )

[0107] The first constant is 3, and the second constant is 2.

[0108] Furthermore, prior to performing step 205, this method may also include the following steps:

[0109] Obtain the downstream negative sequence impedance corresponding to each feeder;

[0110] The sum of each first difference and the downstream negative sequence impedance is calculated as the new first difference.

[0111] In another example of the invention, to further improve the accuracy of the calculation, the negative sequence impedance Z can be further considered when calculating the upstream zero-sequence voltage on the bus M side. down(0) The effect of this means that the first difference can be updated at this point, i.e.:

[0112] First difference = 2Z down(0) -3R f +Z down(2)

[0113] Step 206: Calculate the absolute value of the ratio between each downstream zero-sequence voltage and the upstream zero-sequence voltage to obtain the zero-sequence voltage amplitude ratio;

[0114] In this embodiment, the downstream zero-sequence voltage, i.e., the upstream zero-sequence voltage U of the nth feeder of the N-side bus and the M-side bus, can be calculated separately. M(0) The absolute value of the ratio between them yields the zero-sequence voltage amplitude ratio K. n :

[0115]

[0116] It should be noted that if negative sequence impedance Z is considered... down(0) The effect of this means that the zero-sequence voltage amplitude is greater than K. n for:

[0117]

[0118] It should be noted that when R f When K is small n It mainly depends on the zero-sequence admittance upstream and downstream of the fault, as can be seen from the above equation, K n Approaching 1.5, as the transition resistance increases, K... n Changes such as Figure 5 As shown in the figure, it can be seen that K changes with the transition resistance. n The value remains around 1.5, with little change.

[0119] Step 207: If the zero-sequence voltage amplitude ratio is greater than the preset fault threshold, it is determined that a single-phase open circuit power supply side ground fault has occurred in the feeder to which the zero-sequence voltage amplitude belongs.

[0120] When the line is not faulty, the voltage across the line impedance can be ignored, and K... n ≈1. Therefore, the following line selection criterion can be constructed:

[0121] K i >K set i = 1, 2, ..., n

[0122] In the formula: K i Let K be the ratio of the zero-sequence voltage at the N-side bus of the i-th line to the zero-sequence voltage amplitude at the M-side bus. i Greater than the preset fault threshold K set This indicates that a single-phase open-circuit ground fault has occurred on the feeder to which the zero-sequence voltage amplitude belongs, and that the feeder is the faulty line. K set 1.4 is acceptable.

[0123] Optionally, the method further includes:

[0124] If the bus zero-sequence voltage does not exceed the starting voltage threshold, then proceed to the step of real-time monitoring of the bus zero-sequence voltage corresponding to the bus.

[0125] If the zero-sequence voltage amplitude ratio is less than or equal to the preset fault threshold, it is determined that the feeder to which the zero-sequence voltage amplitude belongs has not experienced a single-phase open-circuit grounding fault on the power supply side.

[0126] Please see Figure 6 , Figure 6 This is a flowchart illustrating a ground fault location method based on double-ended zero-sequence voltage according to an embodiment of the present invention. The specific steps are as follows:

[0127] (1) Determine whether the bus voltage meets the line selection start criterion. If it does, proceed to step 2; otherwise, continue to monitor the line status.

[0128] (2) Obtain the zero-sequence voltage of the bus on the M side and the bus voltage on the N side of each line, and calculate the amplitude ratio of the zero-sequence voltage of the line;

[0129] (3) Determine whether the ratio of the zero-sequence admittance amplitude of each line to that of the reference line is greater than K. set If it is greater than K se If t is true, then the line is a faulty line; otherwise, it is a non-faulty line.

[0130] Please see Figure 7 , Figure 7 This is a schematic diagram of a simulation model of a 10kV arc suppression coil grounding system with multiple circuits on the same busbar and grounding fault in an embodiment of the present invention.

[0131] In this embodiment, a simulation model of a 10kV arc suppression coil grounding system with multiple circuits sharing the same busbar and experiencing multiple grounding faults can be built on the PSCAD platform, such as... Figure 7 As shown. There are 4 outgoing lines at the busbar. The system uses 10% overcompensation, and the system impedance is (7.55 × 10⁻⁶). -4 +j0.3607)Ω. The positive sequence parameters of the line are: r1=0.17Ω / km, x1=0.35Ω / km, c1=0.12μF / km. The zero sequence parameters are: r0=0.32Ω / km, x0=1.12Ω / km, c0=6.4×10 -3 μF / km. Assume a single-phase open circuit and a ground fault on the power supply side occur on line L4.

[0132] To verify the impact of different fault locations, let l f The distance from the fault point to the busbar is the length of the transition resistance. Simulations were performed with a transition resistance of 100Ω, and the simulation results are shown in Table 1.

[0133] 2 5774.55 1.0002 1.0001 1.0002 1.4595 L4 4 5775.17 1.0001 1.0002 1.0002 1.4599 L4 6 5775.67 1.0002 1.0002 1.0001 1.4607 L4 8 5776.45 1.0001 1.0001 1.0001 1.4637 L4 10 5777.54 1.0002 1.0001 1.0002 1.4722 L4 12 5779.12 1.0001 1.0001 1.0002 1.4927 L4

[0134] Table 1 Simulation results at different fault locations

[0135] The simulation results show that the bus voltage on the M side meets the starting value, the voltage amplitude ratio between the end and the beginning of the non-faulty line is close to 1, and the value of the faulty line meets the fault selection criterion. Therefore, this method is not affected by the fault location and can select the faulty line at different fault locations.

[0136] To verify different transition resistances R f To assess the impact of the fault, assuming it occurs in the middle of the line, simulations were performed under different transition resistances. The simulation results are shown in Table 2.

[0137] 1 5776.47 1.0001 1.0001 1.0002 1.4619 L4 10 5776.35 1.0001 1.0002 1.0002 1.4619 L4 100 5776.06 1.0002 1.0001 1.0001 1.4620 L4 500 5774.04 1.0001 1.0001 1.0001 1.4621 L4 1000 5771.15 1.0001 1.0002 1.0002 1.4623 L4

[0138] Table 2 Simulation results for different transition resistances

[0139] The simulation results show that the bus voltage on the M side meets the starting value, the voltage amplitude ratio between the end and the beginning of the non-faulty line is close to 1, and the value of the faulty line meets the fault selection criterion. Therefore, this method almost eliminates the influence of the transition resistance and has a strong ability to withstand the transition resistance.

[0140] In this embodiment of the invention, by real-time monitoring of the zero-sequence voltage of the bus corresponding to the bus, when the zero-sequence voltage of the bus exceeds the starting voltage threshold, the upstream zero-sequence voltage corresponding to the bus and the downstream zero-sequence voltage corresponding to each feeder are obtained. The absolute value of the ratio between each downstream zero-sequence voltage and the upstream zero-sequence voltage is calculated to obtain the zero-sequence voltage amplitude ratio. If the zero-sequence voltage amplitude ratio is greater than a preset fault threshold, it is determined that a single-phase open-circuit grounding fault has occurred on the feeder to which the zero-sequence voltage amplitude belongs. This solves the technical problem that existing grounding fault selection methods cannot be applied to open-circuit grounding faults, making it difficult to comprehensively and accurately select the faulty line. Even under the influence of fault location and transition resistance, the faulty line can still be accurately selected. Currently, open-circuit faults are less considered in the case of open-circuit grounding, mainly focusing on open-circuit ungrounded faults. This method considers the case of open-circuit grounding on the power supply side, which is more in line with reality. Compared with the current problem of difficulty in selecting the line for open-circuit grounding on the power supply side, this method realizes the line selection for single-phase open-circuit grounding faults on the power supply side in arc suppression coil grounding systems, effectively solving the problem of difficulty in selecting the line for this type of fault. Compared to current methods that use negative sequence current characteristics to identify open circuits and grounding faults, this method uses zero sequence voltage information, which is unaffected by load. Addressing the issue of current methods failing to adequately consider the impact of transition resistance and exhibiting failure at high resistance, this method achieves accurate line selection even under the influence of transition resistance.

[0141] Please see Figure 8 , Figure 8 This is a structural block diagram of a ground fault location device based on dual-terminal zero-sequence voltage provided in Embodiment 3 of the present invention.

[0142] This invention provides a ground fault location device based on dual-terminal zero-sequence voltage, relating to an arc suppression coil grounding system. The arc suppression coil grounding system includes a busbar and multiple feeders connected to the busbar. The device includes:

[0143] Monitoring module 801 is used to monitor the zero-sequence voltage of the bus corresponding to the bus in real time;

[0144] The zero-sequence voltage acquisition module 802 is used to acquire the upstream zero-sequence voltage of the bus and the downstream zero-sequence voltage of each feeder when the bus zero-sequence voltage exceeds the starting voltage threshold.

[0145] The amplitude ratio calculation module 803 is used to calculate the absolute value of the ratio between each downstream zero-sequence voltage and the upstream zero-sequence voltage to obtain the zero-sequence voltage amplitude ratio.

[0146] The fault determination module 804 is used to determine that a single-phase open circuit power supply side ground fault has occurred in the feeder to which the zero-sequence voltage amplitude belongs if the zero-sequence voltage amplitude ratio is greater than a preset fault threshold.

[0147] Optionally, the zero-sequence voltage acquisition module 802 includes:

[0148] The impedance detection submodule is used to obtain the upstream zero-sequence equivalent impedance, transition resistance, and downstream zero-sequence equivalent impedance of each feeder when the bus zero-sequence voltage exceeds the start-up voltage threshold.

[0149] The sum calculation submodule is used to calculate the sum between the upstream zero-sequence equivalent impedance and the transition resistance;

[0150] The downstream zero-sequence voltage determination submodule is used to calculate the sum, the first multiplication between the downstream zero-sequence equivalent impedance and the first constant, respectively, to obtain the downstream zero-sequence voltage corresponding to each feeder.

[0151] The upstream zero-sequence voltage determination submodule is used to determine the upstream zero-sequence voltage based on the upstream zero-sequence equivalent impedance, the downstream zero-sequence equivalent impedances, and the transition resistance.

[0152] Optionally, the upstream zero-sequence voltage determination submodule is specifically used for:

[0153] Calculate the second multiplication value between each downstream zero-sequence equivalent impedance and the second constant;

[0154] Calculate the third multiplication factor between the transition resistance and the first constant;

[0155] Calculate the first difference between each second and third multiplication value;

[0156] The upstream zero-sequence voltage is obtained by multiplying each first difference value by the upstream zero-sequence equivalent impedance.

[0157] Optionally, before the upstream zero-sequence voltage determination submodule is specifically used to perform the step of using the product between each first difference and the upstream zero-sequence equivalent impedance as the upstream zero-sequence voltage, it is also used to:

[0158] Obtain the downstream negative sequence impedance corresponding to each feeder;

[0159] The sum of each first difference and the downstream negative sequence impedance is calculated as the new first difference.

[0160] Optionally, the device further includes:

[0161] The loop module is used to jump to the step of real-time monitoring of the zero-sequence voltage of the busbar if the zero-sequence voltage of the busbar does not exceed the starting voltage threshold.

[0162] The fault negation module is used to determine that no single-phase open-circuit grounding fault has occurred on the feeder to which the zero-sequence voltage amplitude belongs if the zero-sequence voltage amplitude ratio is less than or equal to a preset fault threshold.

[0163] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the above-described device and module can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0164] In the embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, apparatuses, or modules, and may be electrical, mechanical, or other forms.

[0165] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0166] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ground fault location method based on two-terminal zero-sequence voltage, characterized in that, The method relates to an arc suppression coil grounding system, the arc suppression coil grounding system comprising a busbar and multiple feeders connected to the busbar, the method comprising: Real-time monitoring of the zero-sequence voltage of the bus corresponding to the bus; When the zero-sequence voltage of the bus exceeds the start-up voltage threshold, the upstream zero-sequence voltage corresponding to the bus and the downstream zero-sequence voltage corresponding to each feeder are obtained. Calculate the absolute value of the ratio between each of the downstream zero-sequence voltages and the upstream zero-sequence voltages to obtain the zero-sequence voltage amplitude ratio; If the zero-sequence voltage amplitude ratio is greater than the preset fault threshold, it is determined that a single-phase open-circuit ground fault has occurred on the power supply side of the feeder to which the zero-sequence voltage amplitude belongs. The step of obtaining the upstream zero-sequence voltage corresponding to the bus and the downstream zero-sequence voltage corresponding to each feeder when the bus zero-sequence voltage exceeds the start-up voltage threshold includes: When the zero-sequence voltage of the bus exceeds the start-up voltage threshold, the upstream zero-sequence equivalent impedance, transition resistance, and downstream zero-sequence equivalent impedance of each feeder are obtained. Calculate the sum of the upstream zero-sequence equivalent impedance and the transition resistance; Calculate the first multiplication value between the sum, the downstream zero-sequence equivalent impedance, the ground zero-sequence current, and the first constant to obtain the downstream zero-sequence voltage corresponding to each feeder; The upstream zero-sequence voltage is determined based on the upstream zero-sequence equivalent impedance, the ground zero-sequence current, each of the downstream zero-sequence equivalent impedances, and the transition resistance.

2. The method according to claim 1, characterized in that, The step of determining the upstream zero-sequence voltage based on the upstream zero-sequence equivalent impedance, the ground zero-sequence current, each of the downstream zero-sequence equivalent impedances, and the transition resistance includes: Calculate the second multiplication value between each of the downstream zero-sequence equivalent impedances and the second constant; Calculate the third multiplication factor between the transition resistance and the first constant; Calculate the first difference between each of the second multipliers and the third multiplier; The upstream zero-sequence voltage is obtained by multiplying the first difference, the ground zero-sequence current, and the upstream zero-sequence equivalent impedance.

3. The method according to claim 2, characterized in that, Before performing the step of using the product of each of the first differences and the upstream zero-sequence equivalent impedance as the upstream zero-sequence voltage, the method further includes: Obtain the downstream negative sequence impedance corresponding to each of the feed lines; The sum of each of the first differences and the downstream negative sequence impedance is calculated as a new first difference.

4. The method according to claim 1, characterized in that, The method further includes: If the zero-sequence voltage of the bus does not exceed the starting voltage threshold, then proceed to the step of real-time monitoring of the zero-sequence voltage of the bus corresponding to the bus. If the zero-sequence voltage amplitude ratio is less than or equal to a preset fault threshold, it is determined that the feeder to which the zero-sequence voltage amplitude belongs has not experienced a single-phase open-circuit power supply side grounding fault.

5. A ground fault location device based on dual-terminal zero-sequence voltage, characterized in that, The invention relates to an arc suppression coil grounding system, the arc suppression coil grounding system comprising a busbar and multiple feeders connected to the busbar, the device comprising: The monitoring module is used to monitor the zero-sequence voltage of the bus corresponding to the bus in real time. The zero-sequence voltage acquisition module is used to acquire the upstream zero-sequence voltage corresponding to the bus and the downstream zero-sequence voltage corresponding to each feeder when the zero-sequence voltage of the bus exceeds the start-up voltage threshold. The amplitude ratio calculation module is used to calculate the absolute value of the ratio between each of the downstream zero-sequence voltages and the upstream zero-sequence voltages to obtain the zero-sequence voltage amplitude ratio. The fault determination module is used to determine that a single-phase open-circuit power supply side grounding fault has occurred in the feeder to which the zero-sequence voltage amplitude belongs if the zero-sequence voltage amplitude ratio is greater than a preset fault threshold. The zero-sequence voltage acquisition module includes: The impedance detection submodule is used to acquire the upstream zero-sequence equivalent impedance, transition resistance, and downstream zero-sequence equivalent impedance of each feeder when the zero-sequence voltage of the bus exceeds the start-up voltage threshold. The sum calculation submodule is used to calculate the sum between the upstream zero-sequence equivalent impedance and the transition resistance; The downstream zero-sequence voltage determination submodule is used to calculate the first multiplication value between the sum, the downstream zero-sequence equivalent impedance, the ground zero-sequence current and the first constant, respectively, to obtain the downstream zero-sequence voltage corresponding to each feeder. The upstream zero-sequence voltage determination submodule is used to determine the upstream zero-sequence voltage based on the upstream zero-sequence equivalent impedance, the ground zero-sequence current, each of the downstream zero-sequence equivalent impedances, and the transition resistance.

6. The apparatus according to claim 5, characterized in that, The upstream zero-sequence voltage determination submodule is specifically used for: Calculate the second multiplication value between each of the downstream zero-sequence equivalent impedances and the second constant; Calculate the third multiplication factor between the transition resistance and the first constant; Calculate the first difference between each of the second multipliers and the third multiplier; The upstream zero-sequence voltage is obtained by multiplying the first difference, the ground zero-sequence current, and the upstream zero-sequence equivalent impedance.

7. The apparatus according to claim 6, characterized in that, Before the upstream zero-sequence voltage determination submodule is specifically configured to perform the step of using the product of each of the first differences and the upstream zero-sequence equivalent impedance as the upstream zero-sequence voltage, it is further configured to: Obtain the downstream negative sequence impedance corresponding to each of the feed lines; The sum of each of the first differences and the downstream negative sequence impedance is calculated as a new first difference.

8. The apparatus according to claim 5, characterized in that, The device further includes: The loop module is used to jump to the step of real-time monitoring of the zero-sequence voltage of the bus if the zero-sequence voltage of the bus does not exceed the starting voltage threshold. The fault denial module is used to determine that no single-phase open-circuit power supply side grounding fault has occurred on the feeder to which the zero-sequence voltage amplitude belongs if the zero-sequence voltage amplitude ratio is less than or equal to a preset fault threshold.

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