A method and system for fast fault location of 10kV power grid

Abstract

This invention provides a method for rapid fault location in a 10kV power grid. The method includes: acquiring the three-phase voltage of the 10kV busbar and the three-phase current of the 10kV switch of the main transformer at a specified time when a fault occurs in the 10kV power grid; determining the fault type of the 10kV power grid based on the three-phase voltage and current, and constructing a composite sequence network and its vector equations related to reactance; selecting the characteristic phases of the composite sequence network, and calculating the positive-sequence, negative-sequence, and zero-sequence voltages and currents in conjunction with the three-phase voltage and current; solving for the reactance value from the fault point to the 10kV busbar in the vector equations related to the composite sequence network and reactance; and further combining the cable's factory-set parameters to obtain the fault distance from the fault point to the 10kV busbar. The fault type is classified as single-phase grounding, two-phase ground fault, two-phase short circuit, or three-phase short circuit. Implementing this invention allows for automatic and rapid location of the fault point distance in various fault types, avoiding the drawbacks of manual distance measurement and the influence of transition resistance.

Description

Technical Field

[0001] This invention relates to the field of power grid fault detection technology, and in particular to a method and system for rapid fault location and ranging in a 10kV power grid. Background Technology

[0002] 110kV and above power grids are large grounding systems, and fault location can be achieved through corresponding relay protection devices. In this case, the fault location principle of the 110kV and above power grid relay protection devices is to measure the impedance from the protection installation point to the fault point and calculate the distance based on the line impedance parameters. However, this is easily affected by transition resistance, leading to inaccurate fault location, thus making fault location only an auxiliary reference.

[0003] Currently, the 10kV power grid is a low grounding current system. Once a transverse fault occurs (such as single-phase grounding, two-phase short circuit, or three-phase short circuit), the existing 10kV relay protection devices cannot quickly locate the fault. Therefore, determining the fault range (fault location) mainly relies on relay protection personnel collecting data and conducting comprehensive analysis to determine the preliminary location of the fault point. This is not only inefficient but also prone to errors. Furthermore, the 10kV power grid is significantly affected by load current during single-phase grounding faults, meaning that the fault location methods used in 110kV and higher voltage power grids cannot be directly applied to 10kV power grids.

[0004] Therefore, there is an urgent need for a new method for fault location in 10kV power grids that can automatically and quickly locate the distance to the fault point in various types of faults. This method can not only avoid the disadvantages of manual distance measurement, but also avoid the influence of transition resistance. Summary of the Invention

[0005] The technical problem to be solved by the embodiments of the present invention is to provide a method and system for rapid fault location in 10kV power grid, which can automatically and quickly locate the distance of the fault point in various types of faults, not only avoiding the disadvantages of manual distance measurement, but also avoiding the influence of transition resistance.

[0006] To address the aforementioned technical problems, this invention provides a method for rapid fault location in a 10kV power grid, comprising the following steps:

[0007] S1. When a fault occurs in the 10kV power grid, obtain the three-phase voltage of the 10kV bus and the three-phase current of the main transformer's 10kV switch at a specified time.

[0008] S2. Based on the obtained three-phase voltage and three-phase current, determine the fault type of the 10kV power grid, and construct the corresponding composite sequence network and its vector equation related to the reactance based on the determined fault type of the 10kV power grid; wherein, the fault type is one of single-phase ground fault, two-phase ground short-circuit fault, two-phase short-circuit fault and three-phase short-circuit fault.

[0009] S3. Select the characteristic phase of the constructed composite sequence network, and calculate the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current, and zero sequence current of the selected characteristic phase based on the obtained three-phase voltage and three-phase current. Solve for the reactance value from the fault point to the 10kV bus in the vector equation relating the constructed composite sequence network to the reactance. Further combine this with predetermined cable factory-fixed parameters to obtain the fault distance from the fault point to the 10kV bus. Wherein, when the fault type is a single-phase ground fault, the selected characteristic phase is the fault phase; when the fault type is a two-phase ground fault or a two-phase short-circuit fault, the selected characteristic phase is the normal phase; when the fault type is a three-phase short-circuit fault, the selected characteristic phase is any fault phase.

[0010] Specifically, step S2 includes:

[0011] Based on the obtained amplitude and phase angle of the three-phase voltage, the zero-sequence voltage is calculated by vector.

[0012] If the vector calculation result is determined to be greater than the preset threshold, it is determined that there is a zero-sequence component. When it is determined that the current difference between any two phases of the acquired three-phase current is within the predetermined range, the fault type of the 10kV power grid is determined to be a single-phase ground fault; or, when it is determined that the current difference between two phases and another phase of the acquired three-phase current is outside the predetermined range, the fault type of the 10kV power grid is determined to be a two-phase ground short-circuit fault.

[0013] If the vector calculation result is determined to be less than or equal to the preset threshold, it is determined that there is no zero-sequence component. If it is determined that the current value of any phase among the three-phase currents is greater than the preset first current threshold, the fault type of the 10kV power grid is determined to be a three-phase short-circuit fault. Or, if it is determined that the current difference between two phases and the other phase among the three-phase currents is greater than the preset second current threshold, the fault type of the 10kV power grid is determined to be a two-phase short-circuit fault.

[0014] Based on the determined fault types of the 10kV power grid, a corresponding composite sequence network is constructed, and further, a vector equation related to reactance is constructed. The composite sequence network includes a single-phase grounding composite sequence network, a two-phase grounding short-circuit composite sequence network, a two-phase short-circuit composite sequence network, and a three-phase short-circuit composite sequence network. The vector equation related to reactance for the single-phase grounding composite sequence network is U1 + U2 = I1 * (2Z).L +Z L0 )+(-U0)+3I1*R g The vector equation relating the two-phase ground fault composite sequence network and the reactance of both the two-phase ground fault composite sequence network and the reactance is U1-U2=(I1-I2)*(Z). L +R g The vector equation relating the three-phase short-circuit composite sequence network and reactance is U1 = I1 * Z. L U1, U2, and U0 represent the positive-sequence voltage, negative-sequence voltage, and zero-sequence voltage, respectively; I1 is the positive-sequence current; I2 is the negative-sequence current; R g Z is the sum of the transition resistance and the cable resistance; L Z represents the positive and negative sequence impedance of the cable. L0 This is the zero-sequence impedance of the cable.

[0015] Specifically, step S3 includes:

[0016] When the fault type is a single-phase ground fault, the selected characteristic phase is determined as the fault phase, and the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current and zero sequence current of the selected characteristic phase are calculated by vector method based on the obtained three-phase voltage and three-phase current.

[0017] Based on the vector equation relating the single-phase grounding composite sequence network and reactance, a vector circle is constructed. The constructed vector circle is then solved according to the positive sequence voltage, negative sequence voltage, and zero sequence voltage of the selected characteristic phase to obtain the reactance voltage. Furthermore, by combining the grounding resistance preset in the 10kV power grid and the zero sequence voltage of the selected characteristic phase, the reactance value from the fault point to the 10kV busbar is calculated.

[0018] Obtain the zero-sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained zero-sequence impedance value. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

[0019] Step S3 further includes:

[0020] When the fault type is a two-phase-to-ground short-circuit fault or a two-phase short-circuit fault, the selected characteristic phase is determined to be a normal phase, and the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current and zero-sequence current of the selected characteristic phase are calculated by vector method based on the obtained three-phase voltage and three-phase current.

[0021] Based on the positive sequence voltage, negative sequence voltage, positive sequence current and negative sequence current of the selected characteristic phase, the vector equation of the two-phase grounding short-circuit composite sequence network or the two-phase short-circuit composite sequence network and reactance is solved to directly obtain the reactance value from the fault point to the 10kV bus.

[0022] Obtain the positive sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained positive sequence impedance value of the cable. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

[0023] Step S3 further includes:

[0024] When the fault type is a three-phase short-circuit fault, the selected characteristic phase is determined to be a normal phase, and the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current and zero sequence current of the selected characteristic phase are calculated by vector method based on the obtained three-phase voltage and three-phase current.

[0025] Based on the positive sequence voltage and positive sequence current of the selected characteristic phase, the vector equation relating the three-phase short-circuit composite sequence network and reactance is solved to directly obtain the reactance value from the fault point to the 10kV bus.

[0026] Obtain the positive sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained positive sequence impedance value of the cable. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

[0027] This invention also provides a system for rapid fault location and ranging in a 10kV power grid, comprising:

[0028] The fault data acquisition unit is used to acquire the three-phase voltage of the 10kV bus and the three-phase current of the main transformer's 10kV switch at a specified time when a fault occurs in the 10kV power grid.

[0029] The composite sequence network and vector equation construction unit is used to determine the fault type of the 10kV power grid based on the obtained three-phase voltage and three-phase current, and to construct the corresponding composite sequence network and its vector equations related to reactance based on the determined fault type of the 10kV power grid; wherein, the fault type is one of single-phase ground fault, two-phase ground short-circuit fault, two-phase short-circuit fault and three-phase short-circuit fault;

[0030] The vector fault distance calculation unit is used to select the characteristic phase of the constructed composite sequence network, and calculate the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current, and zero sequence current of the selected characteristic phase by combining the obtained three-phase voltage and three-phase current. In the vector equation relating the constructed composite sequence network to reactance, the reactance value from the fault point to the 10kV bus is solved. Further, combined with the predetermined fixed parameters of the cable at the factory, the fault distance from the fault point to the 10kV bus is obtained. Wherein, when the fault type is a single-phase ground fault, the selected characteristic phase is the fault phase; when the fault type is a two-phase ground fault or a two-phase short circuit fault, the selected characteristic phase is the normal phase; when the fault type is a three-phase short circuit fault, the selected characteristic phase is any fault phase.

[0031] The composite sequence network and vector equation construction unit includes:

[0032] The zero-sequence voltage vector calculation module is used to perform vector calculations on the zero-sequence voltage based on the amplitude and phase angle of the acquired three-phase voltages.

[0033] The first power grid fault type discrimination module is used to determine the presence of a zero-sequence component if the vector calculation result is greater than a preset threshold, and to determine the fault type of the 10kV power grid as a single-phase ground fault when the current difference between any two phases of the acquired three-phase current is within a predetermined range; or, to determine the fault type of the 10kV power grid as a two-phase ground fault when the current difference between two phases and another phase of the acquired three-phase current is outside the predetermined range.

[0034] The second power grid fault type discrimination module is used to determine that if the vector calculation result is less than or equal to the preset threshold, there is no zero sequence component, and if the current value of any phase among the three-phase currents is greater than the preset first current threshold, the fault type of the 10kV power grid is determined to be a three-phase short circuit fault; or, if the current difference between two phases and the other phase among the three-phase currents is greater than the preset second current threshold, the fault type of the 10kV power grid is determined to be a two-phase short circuit fault.

[0035] The composite sequence network and vector equation construction module is used to construct corresponding composite sequence networks based on the determined fault types of the 10kV power grid, and further construct vector equations related to reactance. The composite sequence networks include single-phase grounding composite sequence networks, two-phase grounding short-circuit composite sequence networks, two-phase short-circuit composite sequence networks, and three-phase short-circuit composite sequence networks. The vector equation related to reactance for the single-phase grounding composite sequence network is U1 + U2 = I1 * (2Z). L +Z L0 )+(-U0)+3I1*R gThe vector equation relating the two-phase ground fault composite sequence network and the reactance of both the two-phase ground fault composite sequence network and the reactance is U1-U2=(I1-I2)*(Z). L +R g The vector equation relating the three-phase short-circuit composite sequence network and reactance is U1 = I1 * Z. L U1, U2, and U0 represent the positive-sequence voltage, negative-sequence voltage, and zero-sequence voltage, respectively; I1 is the positive-sequence current; I2 is the negative-sequence current; R g Z is the sum of the transition resistance and the cable resistance; L Z represents the positive and negative sequence impedance of the cable. L0 This is the zero-sequence impedance of the cable.

[0036] The vector-based fault distance calculation unit includes:

[0037] The single-phase fault distance calculation module is used to determine the selected characteristic phase as the fault phase when the fault type is a single-phase ground fault, and to calculate the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current, and zero-sequence current of the selected characteristic phase using a vector method based on the obtained three-phase voltage and three-phase current; and,

[0038] Based on the vector equation relating the single-phase grounding composite sequence network and reactance, a vector circle is constructed. The constructed vector circle is then solved using the positive-sequence, negative-sequence, and zero-sequence voltages of the selected characteristic phases to obtain the reactance voltage. Furthermore, by combining the preset grounding resistance of the 10kV power grid and the zero-sequence voltage of the selected characteristic phases, the reactance value from the fault point to the 10kV busbar is calculated.

[0039] Obtain the zero-sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained zero-sequence impedance value. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

[0040] The vector-based fault distance calculation unit further includes:

[0041] The two-phase fault distance calculation module is used to determine the selected characteristic phase as the normal phase when the fault type is a two-phase-to-ground short-circuit fault or a two-phase short-circuit fault, and to calculate the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current, and zero-sequence current of the selected characteristic phase respectively using the vector method based on the obtained three-phase voltage and three-phase current; and,

[0042] Based on the positive-sequence voltage, negative-sequence voltage, positive-sequence current, and negative-sequence current of the selected characteristic phase, the vector equation relating the two-phase ground fault composite sequence network or the two-phase ground fault composite sequence network to reactance is solved to directly obtain the reactance value from the fault point to the 10kV busbar; and,

[0043] Obtain the positive sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained positive sequence impedance value of the cable. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

[0044] The vector-based fault distance calculation unit further includes:

[0045] The three-phase fault distance calculation module is used to determine the selected characteristic phase as the normal phase when the fault type is a three-phase short-circuit fault, and to calculate the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current, and zero-sequence current of the selected characteristic phase using a vector method based on the obtained three-phase voltage and three-phase current; and,

[0046] Based on the positive sequence voltage and positive sequence current of the selected characteristic phase, the vector equation relating the three-phase short-circuit composite sequence network and reactance is solved to directly obtain the reactance value from the fault point to the 10kV bus; and,

[0047] Obtain the positive sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained positive sequence impedance value of the cable. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

[0048] Implementing the embodiments of the present invention has the following beneficial effects:

[0049] When a fault occurs in a 10kV power grid, this invention quickly determines the fault type based on the three-phase voltage of the 10kV bus and the three-phase current of the 10kV switch of the main transformer at a specified time. Furthermore, it derives the corresponding vector equations by constructing a composite sequence network for each fault type. Using the positive, negative, and zero-sequence voltages and currents of the characteristic phases of the composite sequence network, it solves the vector equations to obtain the reactance value from the fault point to the 10kV bus. Combined with the cable's factory-fixed parameters, it quickly locates the fault distance from the fault point to the 10kV bus. This allows for automatic and rapid location of the fault distance in various fault types, avoiding the drawbacks of manual distance measurement and the influence of transition resistance. 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, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0051] Figure 1A flowchart of a method for rapid fault location in a 10kV power grid provided in an embodiment of the present invention;

[0052] Figure 2 A single-phase grounding composite sequence network diagram is provided in a method for rapid fault location in a 10kV power grid according to an embodiment of the present invention.

[0053] Figure 3 This invention provides a method for rapid fault location in a 10kV power grid, including a composite sequence network diagram of a two-phase grounding short circuit.

[0054] Figure 4 A two-phase short-circuit composite sequence network diagram is provided in the method for rapid fault location in a 10kV power grid according to an embodiment of the present invention.

[0055] Figure 5 A three-phase short-circuit composite sequence network diagram is provided in the method for rapid fault location in a 10kV power grid according to an embodiment of the present invention.

[0056] Figure 6 The vector circle diagram constructed for the vector equation relating single-phase grounding composite sequence network and reactance in a method for rapid fault location in a 10kV power grid provided in an embodiment of the present invention;

[0057] Figure 7 This is a schematic diagram of a system for rapid fault location in a 10kV power grid, provided as an embodiment of the present invention. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0059] like Figure 1 As shown in the figure, a method for rapid fault location in a 10kV power grid is provided in an embodiment of the present invention. The method includes the following steps:

[0060] Step S1: When a fault occurs in the 10kV power grid, obtain the three-phase voltage of the 10kV bus and the three-phase current of the main transformer's 10kV switch at a specified time.

[0061] The specific process is as follows: when a fault occurs in the 10kV power grid, a fault waveform diagram is obtained through a fault recorder. The fault waveform diagram contains the three-phase voltage waveform of the 10kV bus and the three-phase current waveform of the main transformer to the 10kV switch.

[0062] At this point, given that the current suddenly increases and remains elevated for a period of time (e.g., 70ms) after the fault is cleared, and then drops to zero, data from the stable middle segment of the fault waveform is taken, including the three-phase voltage of the 10kV bus and the three-phase current of the main transformer's 10kV lowering switch. For example, if the fault period is preset to approximately 35ms, then the relevant data of the three-phase voltage of the 10kV bus and the three-phase current of the main transformer's 10kV lowering switch at this 35ms point are taken.

[0063] S2. Based on the obtained three-phase voltage and three-phase current, determine the fault type of the 10kV power grid, and construct the corresponding composite sequence network and its vector equation related to the reactance based on the determined fault type of the 10kV power grid; wherein, the fault type is one of single-phase ground fault, two-phase ground short-circuit fault, two-phase short-circuit fault and three-phase short-circuit fault.

[0064] The specific process is as follows: First, based on the obtained amplitude and phase angle of the three-phase voltages, the zero-sequence voltage is calculated using vector methods. It should be noted that the vector calculation of the positive-sequence voltage, negative-sequence voltage, and zero-sequence voltage of the three-phase voltages is a common method in this field, and will not be elaborated upon here.

[0065] Secondly, if the vector calculation result (i.e., zero-sequence voltage) is determined to be greater than a preset threshold (e.g., 0), then a zero-sequence component is identified. Furthermore, if the current difference between any two phases of the acquired three-phase current is within a predetermined range (e.g., [-0.8A, +0.8A]), the fault type of the 10kV power grid is determined to be a single-phase ground fault. Alternatively, if the current difference between two phases and another phase of the acquired three-phase current is outside the predetermined range, the fault type of the 10kV power grid is determined to be a two-phase ground fault. It should be noted that a zero-sequence component only exists when a ground fault occurs. Additionally, a two-phase ground fault not only has a zero-sequence component but also positive and negative sequence components. Moreover, the currents of the two faulty phases in a two-phase ground fault current reach thousands of amperes, while the normal phases only have tens or hundreds of amperes, resulting in a very large current difference between the faulty and normal phases, far exceeding the aforementioned predetermined range.

[0066] Alternatively, if the vector calculation result (i.e., zero-sequence voltage) is determined to be less than or equal to the aforementioned preset threshold (e.g., 0), then it is determined that there is no zero-sequence component. Furthermore, if it is determined that the current value of any phase among the acquired three-phase currents is greater than the preset first current threshold, then the fault type of the 10kV power grid is determined to be a three-phase short-circuit fault. Or, if it is determined that the current difference between two phases and the other phase among the acquired three-phase currents is greater than the preset second current threshold, then the fault type of the 10kV power grid is determined to be a two-phase short-circuit fault. It should be noted that both three-phase and two-phase short-circuit faults are symmetrical short circuits, and because there is no grounding, there is no zero-sequence component. In addition, the currents of the two or three faulty phases in both two-phase and three-phase short-circuit faults reach thousands of amperes or more, while the normal operating load current is only a few hundred amperes. Therefore, different limits can be set to determine the fault type.

[0067] Finally, based on the determined fault types of the 10kV power grid, a corresponding composite sequence network was constructed, and further, vector equations related to reactance were constructed, as follows:

[0068] (a) When the fault type is a single-phase ground fault, a single-phase ground composite sequence network is constructed, such as... Figure 2 As shown:

[0069] exist Figure 2 In this paper, a single-phase grounding composite sequence network is constructed using a phase A fault as an example; where R g Z is the sum of the transition resistance and the cable resistance; L Z represents the positive and negative sequence impedance of the cable. L0 U1 represents the zero-sequence impedance of the cable; U1, U2, and U0 represent the positive-sequence voltage, negative-sequence voltage, and zero-sequence voltage, respectively; I1, I2, and I0 represent the positive-sequence current, negative-sequence current, and zero-sequence current, respectively. It should be noted that the zero-sequence impedance of the grounding transformer is ignored here.

[0070] according to Figure 2 The composite sequence network can be established using the following equations:

[0071]

[0072] Based on the above equations, the vector equation relating the single-phase grounding composite sequence network and reactance can be solved as follows:

[0073] U1+U2=I1*(2Z L +Z L0 )+(-U0)+3I1*R g (1).

[0074] (b) When the fault type is a two-phase-to-ground short-circuit fault, a two-phase-to-ground short-circuit composite sequence network is constructed, such as... Figure 3 As shown:

[0075] exist Figure 3 In this paper, a two-phase-to-ground short-circuit composite sequence network is constructed using a phase-to-BC fault as an example, and based on... Figure 3 The composite sequence network is constructed, and the vector equation relating the two-phase ground fault composite sequence network to the reactance is as follows:

[0076] U1-U2=(I1-I2)*(Z L +R g (2).

[0077] (c) When the fault type is a two-phase short-circuit fault, a two-phase short-circuit composite sequence network is constructed, such as... Figure 4 As shown:

[0078] exist Figure 4 In this paper, a two-phase short-circuit composite sequence network is constructed using a phase-BC inter-fault as an example, and based on... Figure 4 The composite sequence network is constructed, and the vector equation relating the two-phase short-circuit composite sequence network and the reactance is equivalent to the above formula (2).

[0079] (d) When the fault type is a three-phase short-circuit fault, a three-phase short-circuit composite sequence network is constructed, such as... Figure 5 As shown:

[0080] exist Figure 5 In this process, a three-phase short-circuit composite sequence network is constructed, and based on... Figure 5 The composite sequence network of the three-phase short-circuit network is constructed, and the vector equation relating the composite sequence network to the reactance is as follows:

[0081] U1=I1*Z L (3).

[0082] S3. Select the characteristic phase of the constructed composite sequence network, and calculate the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current, and zero sequence current of the selected characteristic phase based on the obtained three-phase voltage and three-phase current. Solve for the reactance value from the fault point to the 10kV bus in the vector equation relating the constructed composite sequence network to the reactance. Further combine this with predetermined cable factory-fixed parameters to obtain the fault distance from the fault point to the 10kV bus. Wherein, when the fault type is a single-phase ground fault, the selected characteristic phase is the fault phase; when the fault type is a two-phase ground fault or a two-phase short-circuit fault, the selected characteristic phase is the normal phase; when the fault type is a three-phase short-circuit fault, the selected characteristic phase is any fault phase.

[0083] The specific process is as follows: Given that there are four types of power grid faults—single-phase ground fault, two-phase ground fault, two-phase short circuit fault, and three-phase short circuit fault—it is necessary to quickly locate different fault distances based on different fault types, as detailed below:

[0084] (a) The fault type is a single-phase ground fault: First, determine the selected characteristic phase as the fault phase, and calculate the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current and zero sequence current of the selected characteristic phase by means of the vector method based on the obtained three-phase voltage and three-phase current.

[0085] Secondly, based on the vector equation relating the single-phase grounding composite sequence network and reactance, i.e., formula (1), a vector circle is constructed. The constructed vector circle is solved according to the positive sequence voltage, negative sequence voltage and zero sequence voltage of the selected characteristic phase to obtain the reactance voltage. Furthermore, the reactance value from the fault point to the 10kV bus is calculated by combining the grounding resistance preset in the 10kV power grid and the zero sequence voltage of the selected characteristic phase.

[0086] Among them, the vector circle is as follows Figure 6 As shown, diameter OA represents U1+U2, OB represents U0, OC is the direction of OB and represents -U0, and D is the intersection of the extension of OC and the circle with OA as its diameter. From the vector diagram, we can obtain CD as the transition resistance and other resistance voltage drop compensation, and AD as the zero-sequence and twice-positive-sequence reactance voltage drops of the cable, which is the reactance voltage to be solved.

[0087] Finally, the zero-sequence impedance value of the cable in the fixed parameters of the cable at the factory is obtained, and the reactance value from the fault point to the 10kV bus is divided by the obtained zero-sequence impedance value of the cable. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

[0088] In one example, on the 10kV bus: the amplitude of phase A voltage is 97.825, and the phase angle is -69.82; the amplitude of phase B voltage is 99.875, and the phase angle is -131.39; the amplitude of phase C voltage is 2.44, and the phase angle is 91.99. At the 10kV substation of the main transformer: the amplitude of phase A current is 1.229, and the phase angle is -82.58; the amplitude of phase B current is 1.099, and the phase angle is 160.78; the amplitude of phase C current is 1.223, and the phase angle is 43.77.

[0089] Taking the non-characteristic phase A as an example, the zero-sequence voltage vector is calculated as follows: (97.825∠-69.82+99.875∠-131.39+2.44∠91.99) / 3=55.82∠-101.14; the positive-sequence voltage vector is calculated as follows: (97.825∠-69.82+99.875∠-11.39+2.44∠-28.01) / 3=58.313∠-40.10; the negative-sequence voltage vector is calculated as follows: (97.825∠-69.82+99.875∠-251.39+2.44∠211.99) / 3=0.517∠97.22.

[0090] Zero-sequence current vector calculation: (1.229∠-82.58+1.099∠160.78+1.223∠43.77) / 3=0.0038∠-69.24; Positive-sequence current vector calculation: (1.229∠-82.58+1.099∠280.78+1.223∠-76.23) / 3=1.182∠-79.35; Negative-sequence current vector calculation: (1.229∠-82.58+1.099∠40.78+1.223∠163.77) / 3=0.08∠-139.057.

[0091] It should be noted that for phase B, its positive sequence voltage and current correspond to an adjustment of the phase angle by -120° based on the positive sequence voltage and current of phase A, and its negative sequence voltage and current correspond to an adjustment of the phase angle by +120° based on the negative sequence voltage and current of phase A. Similarly, for phase C, its positive sequence voltage and current correspond to an adjustment of the phase angle by +120° based on the positive sequence voltage and current of phase A, and its negative sequence voltage and current correspond to an adjustment of the phase angle by -120° based on the negative sequence voltage and current of phase A.

[0092] At this point, since the selected characteristic phase is phase C, it is necessary to adjust the positive sequence angle by +120°, the negative sequence angle by -120°, and keep the zero sequence angle unchanged. Therefore, the positive sequence voltage of phase C is 58.313∠79.9, the negative sequence voltage is 0.517∠-22.78, the zero sequence voltage is 55.82∠-101.14, the positive sequence current is 1.182∠40.65, the negative sequence current is 0.08∠-259.057, and the zero sequence current is 0.0038∠-69.24.

[0093] Based on the above calculation results, according to formula (1), U1+U2 can be calculated as 58.313∠79.9+0.517∠-22.78=58.20∠79.4; U0 is 55.82∠-101.146, then -U0 is 55.82∠78.86.

[0094] therefore, Figure 6 The OA is 58.20∠79.4, and its reverse polarity is 58.20∠-100.6; the OC (i.e., the resistive component) is 55.82∠78.86, and its reverse polarity is 55.82∠-101.14. Furthermore, through... Figure 6 From the vector circle, we can obtain the relationship between reactance and voltage as AD = OA * sin∠AOD. At this point, ∠AOD = 101.146 - 100.6 = 0.546, thus the reactance voltage AD = 58.2 * sin0.546 = 0.554V can be calculated.

[0095] Since the preset grounding resistance of the 10kV power grid is 16 ohms for a single-phase grounding, totaling 48 ohms, and the zero-sequence voltage is 55.82V, the reactance is 0.554 × 48 ÷ 55.82 = 0.476Ω.

[0096] Finally, the cable generally uses a three-core copper conductor (YJV, YJV22) power cable with a voltage rating of 12kV and a cross-sectional area of ​​300 to 400 mm². Its positive and negative impedances are 0.1080 to 0.1212 Ω / km, and its zero-sequence impedance is 2.281 to 2.297 Ω / km. In this case, the zero-sequence impedance value of the cable is taken as 2.297 Ω / km. Therefore, the fault distance from the fault point to the 10kV busbar is 0.476 ÷ 2.297 = 0.207 km.

[0097] (b) For fault types of two-phase-to-ground short-circuit faults or two-phase short-circuit faults: First, determine that the selected characteristic phase is the normal phase, and based on the obtained three-phase voltages and three-phase currents, calculate the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current, and zero-sequence current of the selected characteristic phase using the vector method. It can be understood that for AB-phase faults, phase C is the characteristic phase; for AC-phase faults, phase B is the characteristic phase; and for BC-phase faults, phase A is the characteristic phase.

[0098] Secondly, based on the positive-sequence voltage, negative-sequence voltage, positive-sequence current, and negative-sequence current of the selected characteristic phase, the vector equation relating the two-phase ground fault composite sequence network (or two-phase short-circuit composite sequence network) to the reactance (i.e., formula (2)) is solved to directly obtain the reactance value from the fault point to the 10kV bus. It should be noted that formula (2) simplifies to the reactance vector equation Z. L =U / I*sina; where U is the vector calculation result of U1-U2, I is the vector calculation result of I1-I2, and a is the angle between U and I.

[0099] Finally, the positive sequence impedance value of the cable from the factory-set parameters is obtained, and the reactance value from the fault point to the 10kV bus is divided by the obtained positive sequence impedance value. The quotient is taken as the fault distance from the fault point to the 10kV bus and output. The zero sequence impedance value of the cable is taken as 2.297Ω / km.

[0100] It should be noted that the calculation methods for the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current, and zero sequence current of the selected characteristic phase in a two-phase ground fault are the same as those for the selected characteristic phase in a single-phase ground fault, and will not be repeated here.

[0101] (c) The fault type is a three-phase short circuit fault: First, determine that the selected characteristic phase is a normal phase, and calculate the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current and zero sequence current of the selected characteristic phase respectively by means of the vector method based on the obtained three-phase voltage and three-phase current.

[0102] Secondly, based on the positive sequence voltage and positive sequence current of the selected characteristic phase, the vector equation relating the three-phase short-circuit composite sequence network and reactance (i.e., formula (3)) is solved to directly obtain the reactance value from the fault point to the 10kV bus. It should be noted that formula (3) simplifies to the reactance vector equation Z. L =U / I*sina; where U is U1, I is I1, and a is the angle between U1 and I1.

[0103] Finally, the positive sequence impedance value of the cable from the factory-set parameters is obtained, and the reactance value from the fault point to the 10kV bus is divided by the obtained positive sequence impedance value. The quotient is taken as the fault distance from the fault point to the 10kV bus and output. The zero sequence impedance value of the cable is taken as 2.297Ω / km.

[0104] like Figure 7 As shown in the figure, a system for rapid fault location and ranging in a 10kV power grid is provided in an embodiment of the present invention, comprising:

[0105] The fault data acquisition unit 110 is used to acquire the three-phase voltage of the 10kV bus and the three-phase current of the main transformer's 10kV switch at a specified time when a fault occurs in the 10kV power grid.

[0106] The composite sequence network and vector equation construction unit 120 is used to determine the fault type of the 10kV power grid based on the obtained three-phase voltage and three-phase current, and to construct the corresponding composite sequence network and its vector equations related to reactance based on the determined fault type of the 10kV power grid; wherein, the fault type is one of single-phase ground fault, two-phase ground short-circuit fault, two-phase short-circuit fault and three-phase short-circuit fault;

[0107] The vector fault distance calculation unit 130 is used to select the characteristic phase of the constructed composite sequence network, and calculate the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current, and zero sequence current of the selected characteristic phase by combining the obtained three-phase voltage and three-phase current. In the vector equation relating the constructed composite sequence network to the reactance, the reactance value from the fault point to the 10kV bus is solved. Furthermore, combined with the predetermined fixed parameters of the cable at the factory, the fault distance from the fault point to the 10kV bus is obtained. Wherein, when the fault type is a single-phase ground fault, the selected characteristic phase is the fault phase; when the fault type is a two-phase ground fault or a two-phase short circuit fault, the selected characteristic phase is the normal phase; when the fault type is a three-phase short circuit fault, the selected characteristic phase is any fault phase.

[0108] The composite sequence network and vector equation construction unit 120 includes:

[0109] The zero-sequence voltage vector calculation module is used to perform vector calculations on the zero-sequence voltage based on the amplitude and phase angle of the acquired three-phase voltages.

[0110] The first power grid fault type discrimination module is used to determine the presence of a zero-sequence component if the vector calculation result is greater than a preset threshold, and to determine the fault type of the 10kV power grid as a single-phase ground fault when the current difference between any two phases of the acquired three-phase current is within a predetermined range; or, to determine the fault type of the 10kV power grid as a two-phase ground fault when the current difference between two phases and another phase of the acquired three-phase current is outside the predetermined range.

[0111] The second power grid fault type discrimination module is used to determine that if the vector calculation result is less than or equal to the preset threshold, there is no zero sequence component, and if the current value of any phase among the three-phase currents is greater than the preset first current threshold, the fault type of the 10kV power grid is determined to be a three-phase short circuit fault; or, if the current difference between two phases and the other phase among the three-phase currents is greater than the preset second current threshold, the fault type of the 10kV power grid is determined to be a two-phase short circuit fault.

[0112] The composite sequence network and vector equation construction module is used to construct corresponding composite sequence networks based on the determined fault types of the 10kV power grid, and further construct vector equations related to reactance. The composite sequence networks include single-phase grounding composite sequence networks, two-phase grounding short-circuit composite sequence networks, two-phase short-circuit composite sequence networks, and three-phase short-circuit composite sequence networks. The vector equation related to reactance for the single-phase grounding composite sequence network is U1 + U2 = I1 * (2Z). L +Z L0 )+(-U0)+3I1*R g The vector equation relating the two-phase ground fault composite sequence network and the reactance of both the two-phase ground fault composite sequence network and the reactance is U1-U2=(I1-I2)*(Z). L +R g The vector equation relating the three-phase short-circuit composite sequence network and reactance is U1 = I1 * Z. L U1, U2, and U0 represent the positive-sequence voltage, negative-sequence voltage, and zero-sequence voltage, respectively; I1 is the positive-sequence current; I2 is the negative-sequence current; R g Z is the sum of the transition resistance and the cable resistance; L Z represents the positive and negative sequence impedance of the cable. L0 This is the zero-sequence impedance of the cable.

[0113] The vector fault distance calculation unit 130 includes:

[0114] The single-phase fault distance calculation module is used to determine the selected characteristic phase as the fault phase when the fault type is a single-phase ground fault, and to calculate the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current, and zero-sequence current of the selected characteristic phase using a vector method based on the obtained three-phase voltage and three-phase current; and,

[0115] Based on the vector equation relating the single-phase grounding composite sequence network and reactance, a vector circle is constructed. The constructed vector circle is then solved using the positive-sequence, negative-sequence, and zero-sequence voltages of the selected characteristic phases to obtain the reactance voltage. Furthermore, by combining the preset grounding resistance of the 10kV power grid and the zero-sequence voltage of the selected characteristic phases, the reactance value from the fault point to the 10kV busbar is calculated.

[0116] Obtain the zero-sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained zero-sequence impedance value. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

[0117] The vector fault distance calculation unit 130 further includes:

[0118] The two-phase fault distance calculation module is used to determine the selected characteristic phase as the normal phase when the fault type is a two-phase-to-ground short-circuit fault or a two-phase short-circuit fault, and to calculate the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current, and zero-sequence current of the selected characteristic phase respectively using the vector method based on the obtained three-phase voltage and three-phase current; and,

[0119] Based on the positive-sequence voltage, negative-sequence voltage, positive-sequence current, and negative-sequence current of the selected characteristic phase, the vector equation relating the two-phase ground fault composite sequence network or the two-phase ground fault composite sequence network to reactance is solved to directly obtain the reactance value from the fault point to the 10kV busbar; and,

[0120] Obtain the positive sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained positive sequence impedance value of the cable. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

[0121] The vector fault distance calculation unit 130 further includes:

[0122] The three-phase fault distance calculation module is used to determine the selected characteristic phase as the normal phase when the fault type is a three-phase short-circuit fault, and to calculate the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current, and zero-sequence current of the selected characteristic phase using a vector method based on the obtained three-phase voltage and three-phase current; and,

[0123] Based on the positive sequence voltage and positive sequence current of the selected characteristic phase, the vector equation relating the three-phase short-circuit composite sequence network and reactance is solved to directly obtain the reactance value from the fault point to the 10kV bus; and,

[0124] Obtain the positive sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained positive sequence impedance value of the cable. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

[0125] Implementing the embodiments of the present invention has the following beneficial effects:

[0126] When a fault occurs in a 10kV power grid, this invention quickly determines the fault type based on the three-phase voltage of the 10kV bus and the three-phase current of the 10kV switch of the main transformer at a specified time. Furthermore, it derives the corresponding vector equations by constructing a composite sequence network for each fault type. Using the positive, negative, and zero-sequence voltages and currents of the characteristic phases of the composite sequence network, it solves the vector equations to obtain the reactance value from the fault point to the 10kV bus. Combined with the cable's factory-fixed parameters, it quickly locates the fault distance from the fault point to the 10kV bus. This allows for automatic and rapid location of the fault distance in various fault types, avoiding the drawbacks of manual distance measurement and the influence of transition resistance.

[0127] It is worth noting that the various system modules included in the above system embodiments are only divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be achieved; in addition, the specific names of each functional module are only for easy differentiation and are not used to limit the scope of protection of the present invention.

[0128] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as ROM / RAM, disk, optical disk, etc.

[0129] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for rapid fault location in a 10kV power grid, characterized in that, The method includes the following steps: S1. When a fault occurs in the 10kV power grid, obtain the three-phase voltage of the 10kV bus and the three-phase current of the main transformer's 10kV switch at a specified time. S2. Based on the obtained three-phase voltage and three-phase current, determine the fault type of the 10kV power grid, and construct the corresponding composite sequence network and its vector equation related to the reactance based on the determined fault type of the 10kV power grid; wherein, the fault type is one of single-phase ground fault, two-phase ground short-circuit fault, two-phase short-circuit fault and three-phase short-circuit fault. S3. Select the characteristic phase of the constructed composite sequence network, and calculate the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current, and zero sequence current of the selected characteristic phase based on the obtained three-phase voltage and three-phase current. Solve for the reactance value from the fault point to the 10kV bus in the vector equation relating the constructed composite sequence network to the reactance. Further combine this with predetermined cable factory-fixed parameters to obtain the fault distance from the fault point to the 10kV bus. Wherein, when the fault type is a single-phase ground fault, the selected characteristic phase is the fault phase; when the fault type is a two-phase ground fault or a two-phase short-circuit fault, the selected characteristic phase is the normal phase; when the fault type is a three-phase short-circuit fault, the selected characteristic phase is any fault phase.

2. The method for rapid fault location and ranging in a 10kV power grid as described in claim 1, characterized in that, Step S2 specifically includes: Based on the obtained amplitude and phase angle of the three-phase voltage, the zero-sequence voltage is calculated by vector. If the vector calculation result is determined to be greater than the preset threshold, it is determined that there is a zero-sequence component. When it is determined that the current difference between any two phases of the acquired three-phase current is within the predetermined range, the fault type of the 10kV power grid is determined to be a single-phase ground fault; or, when it is determined that the current difference between two phases and another phase of the acquired three-phase current is outside the predetermined range, the fault type of the 10kV power grid is determined to be a two-phase ground short-circuit fault. If the vector calculation result is determined to be less than or equal to the preset threshold, it is determined that there is no zero-sequence component. If it is determined that the current value of any phase among the three-phase currents is greater than the preset first current threshold, the fault type of the 10kV power grid is determined to be a three-phase short-circuit fault. Or, if it is determined that the current difference between two phases and the other phase among the three-phase currents is greater than the preset second current threshold, the fault type of the 10kV power grid is determined to be a two-phase short-circuit fault. Based on the determined fault types of the 10kV power grid, a corresponding composite sequence network is constructed, and further, a vector equation related to reactance is constructed. The composite sequence network includes a single-phase grounding composite sequence network, a two-phase grounding short-circuit composite sequence network, a two-phase short-circuit composite sequence network, and a three-phase short-circuit composite sequence network. The vector equation related to reactance for the single-phase grounding composite sequence network is U1 + U2 = I1 * (2Z). L +Z L0 )+(-U0)+3I1*R g The vector equation relating the two-phase ground fault composite sequence network and the reactance of both the two-phase ground fault composite sequence network and the reactance is U1-U2=(I1-I2)*(Z). L +R g The vector equation relating the three-phase short-circuit composite sequence network and reactance is U1 = I1 * Z. L U1, U2, and U0 represent the positive-sequence voltage, negative-sequence voltage, and zero-sequence voltage, respectively; I1 is the positive-sequence current; I2 is the negative-sequence current; R g Z is the sum of the transition resistance and the cable resistance; L Z represents the positive and negative sequence impedance of the cable. L0 This is the zero-sequence impedance of the cable.

3. The method for rapid fault location and ranging in a 10kV power grid as described in claim 2, characterized in that, Step S3 specifically includes: When the fault type is a single-phase ground fault, the selected characteristic phase is determined as the fault phase, and the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current and zero sequence current of the selected characteristic phase are calculated by vector method based on the obtained three-phase voltage and three-phase current. Based on the vector equation relating the single-phase grounding composite sequence network and reactance, a vector circle is constructed. The constructed vector circle is then solved according to the positive sequence voltage, negative sequence voltage, and zero sequence voltage of the selected characteristic phase to obtain the reactance voltage. Furthermore, by combining the grounding resistance preset in the 10kV power grid and the zero sequence voltage of the selected characteristic phase, the reactance value from the fault point to the 10kV busbar is calculated. Obtain the zero-sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained zero-sequence impedance value. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

4. The method for rapid fault location and ranging in a 10kV power grid as described in claim 2, characterized in that, Step S3 further includes: When the fault type is a two-phase-to-ground short-circuit fault or a two-phase short-circuit fault, the selected characteristic phase is determined to be a normal phase, and the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current and zero-sequence current of the selected characteristic phase are calculated by vector method based on the obtained three-phase voltage and three-phase current. Based on the positive sequence voltage, negative sequence voltage, positive sequence current and negative sequence current of the selected characteristic phase, the vector equation of the two-phase grounding short-circuit composite sequence network or the two-phase short-circuit composite sequence network and reactance is solved to directly obtain the reactance value from the fault point to the 10kV bus. Obtain the positive sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained positive sequence impedance value of the cable. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

5. The method for rapid fault location and ranging in a 10kV power grid as described in claim 2, characterized in that, Step S3 further includes: When the fault type is a three-phase short-circuit fault, the selected characteristic phase is determined to be a normal phase, and the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current and zero sequence current of the selected characteristic phase are calculated by vector method based on the obtained three-phase voltage and three-phase current. Based on the positive sequence voltage and positive sequence current of the selected characteristic phase, the vector equation relating the three-phase short-circuit composite sequence network and reactance is solved to directly obtain the reactance value from the fault point to the 10kV bus. Obtain the positive sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained positive sequence impedance value of the cable. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

6. A system for rapid fault location and ranging in a 10kV power grid, characterized in that, include; The fault data acquisition unit is used to acquire the three-phase voltage of the 10kV bus and the three-phase current of the main transformer's 10kV switch at a specified time when a fault occurs in the 10kV power grid. The composite sequence network and vector equation construction unit is used to determine the fault type of the 10kV power grid based on the obtained three-phase voltage and three-phase current, and to construct the corresponding composite sequence network and its vector equations related to reactance based on the determined fault type of the 10kV power grid; wherein, the fault type is one of single-phase ground fault, two-phase ground short-circuit fault, two-phase short-circuit fault and three-phase short-circuit fault; The vector fault distance calculation unit is used to select the characteristic phase of the constructed composite sequence network, and calculate the positive sequence voltage, negative sequence voltage, zero sequence voltage, positive sequence current, negative sequence current, and zero sequence current of the selected characteristic phase by combining the obtained three-phase voltage and three-phase current. In the vector equation relating the constructed composite sequence network to reactance, the reactance value from the fault point to the 10kV bus is solved. Further, combined with the predetermined fixed parameters of the cable at the factory, the fault distance from the fault point to the 10kV bus is obtained. Wherein, when the fault type is a single-phase ground fault, the selected characteristic phase is the fault phase; when the fault type is a two-phase ground fault or a two-phase short circuit fault, the selected characteristic phase is the normal phase; when the fault type is a three-phase short circuit fault, the selected characteristic phase is any fault phase.

7. The system for rapid fault location and ranging in a 10kV power grid as described in claim 6, characterized in that, The composite sequence network and vector equation construction unit includes: The zero-sequence voltage vector calculation module is used to perform vector calculations on the zero-sequence voltage based on the amplitude and phase angle of the acquired three-phase voltages. The first power grid fault type discrimination module is used to determine the presence of a zero-sequence component if the vector calculation result is greater than a preset threshold, and to determine the fault type of the 10kV power grid as a single-phase ground fault when the current difference between any two phases of the acquired three-phase current is within a predetermined range; or, to determine the fault type of the 10kV power grid as a two-phase ground fault when the current difference between two phases and another phase of the acquired three-phase current is outside the predetermined range. The second power grid fault type discrimination module is used to determine that if the vector calculation result is less than or equal to the preset threshold, there is no zero sequence component, and if the current value of any phase among the three-phase currents is greater than the preset first current threshold, the fault type of the 10kV power grid is determined to be a three-phase short circuit fault; or, if the current difference between two phases and the other phase among the three-phase currents is greater than the preset second current threshold, the fault type of the 10kV power grid is determined to be a two-phase short circuit fault. The composite sequence network and vector equation construction module is used to construct corresponding composite sequence networks based on the determined fault types of the 10kV power grid, and further construct vector equations related to reactance. The composite sequence networks include single-phase grounding composite sequence networks, two-phase grounding short-circuit composite sequence networks, two-phase short-circuit composite sequence networks, and three-phase short-circuit composite sequence networks. The vector equation related to reactance for the single-phase grounding composite sequence network is U1 + U2 = I1 * (2Z). L +Z L0 )+(-U0)+3I1*R g The vector equation relating the two-phase ground fault composite sequence network and the reactance of both the two-phase ground fault composite sequence network and the reactance is U1-U2=(I1-I2)*(Z). L +R g The vector equation relating the three-phase short-circuit composite sequence network and reactance is U1 = I1 * Z. L U1, U2, and U0 represent the positive-sequence voltage, negative-sequence voltage, and zero-sequence voltage, respectively; I1 is the positive-sequence current; I2 is the negative-sequence current; R g Z is the sum of the transition resistance and the cable resistance; L Z represents the positive and negative sequence impedance of the cable. L0 This is the zero-sequence impedance of the cable.

8. The system for rapid fault location and ranging in a 10kV power grid as described in claim 7, characterized in that, The vector-based fault distance calculation unit includes: The single-phase fault distance calculation module is used to determine the selected characteristic phase as the fault phase when the fault type is a single-phase ground fault, and to calculate the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current, and zero-sequence current of the selected characteristic phase using a vector method based on the obtained three-phase voltage and three-phase current; and, Based on the vector equation relating the single-phase grounding composite sequence network and reactance, a vector circle is constructed. The constructed vector circle is then solved using the positive-sequence, negative-sequence, and zero-sequence voltages of the selected characteristic phases to obtain the reactance voltage. Furthermore, by combining the preset grounding resistance of the 10kV power grid and the zero-sequence voltage of the selected characteristic phases, the reactance value from the fault point to the 10kV busbar is calculated. Obtain the zero-sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained zero-sequence impedance value. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

9. The system for rapid fault location and ranging in a 10kV power grid as described in claim 7, characterized in that, The vector-based fault distance calculation unit also includes: The two-phase fault distance calculation module is used to determine the selected characteristic phase as the normal phase when the fault type is a two-phase-to-ground short-circuit fault or a two-phase short-circuit fault, and to calculate the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current, and zero-sequence current of the selected characteristic phase respectively using the vector method based on the obtained three-phase voltage and three-phase current; and, Based on the positive-sequence voltage, negative-sequence voltage, positive-sequence current, and negative-sequence current of the selected characteristic phase, the vector equation relating the two-phase ground fault composite sequence network or the two-phase ground fault composite sequence network to reactance is solved to directly obtain the reactance value from the fault point to the 10kV busbar; and, Obtain the positive sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained positive sequence impedance value of the cable. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

10. The system for rapid fault location and ranging in a 10kV power grid as described in claim 7, characterized in that, The vector-based fault distance calculation unit also includes: The three-phase fault distance calculation module is used to determine the selected characteristic phase as the normal phase when the fault type is a three-phase short-circuit fault, and to calculate the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current, and zero-sequence current of the selected characteristic phase using a vector method based on the obtained three-phase voltage and three-phase current; and, Based on the positive sequence voltage and positive sequence current of the selected characteristic phase, the vector equation relating the three-phase short-circuit composite sequence network and reactance is solved to directly obtain the reactance value from the fault point to the 10kV bus; and, Obtain the positive sequence impedance value of the cable from the factory-set parameters, and divide the obtained reactance value from the fault point to the 10kV bus by the obtained positive sequence impedance value of the cable. The quotient is taken as the fault distance from the fault point to the 10kV bus and output.

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