A method and device for locating a single-phase broken conductor of a power distribution network caused by lightning stroke

Abstract

The embodiment of the application discloses a lightning-caused single-phase broken line positioning method of a power distribution network, comprising the following steps: determining the line voltage of each node based on the three-phase voltage signals collected by each node in a fault line; determining the steady-state amplitude per-unit value of the line voltage of each node respectively; judging whether the steady-state amplitude per-unit value of the line voltage of each node meets a preset condition to determine the type of each node; and determining the line segment between two different type nodes in each node as a fault section of the fault line based on the type of each node. The embodiment of the application also discloses a lightning-caused single-phase broken line positioning device of a power distribution network. The application is suitable for different transition resistances and can accurately locate the fault section.

Description

Technical Field

[0001] This invention relates to the field of power system technology, and more specifically, to a method and apparatus for locating single-phase line breakage in a distribution network caused by lightning strikes. Background Technology

[0002] 10kV insulated lines operate in complex environments with low insulation levels, making them highly susceptible to line breakage due to lightning strikes. Lightning-induced line breakage points often occur on the load side of the insulators, within 200mm of the insulator axis, leading to single-phase line breakage and grounding on the load side. Due to the insulation layer, the transition resistance tends to be high. After a fault occurs, the system current changes little, making timely and effective detection of the line breakage difficult. Therefore, a method is urgently needed to locate the faulty section of the line breakage, providing a basis for subsequent maintenance and maintaining the stability of the power grid. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a method and apparatus for locating single-phase line breakage in a power distribution network caused by lightning strikes, which locates the faulty section based on the different line voltage amplitudes at each node after the fault.

[0004] This invention provides a method for locating a single-phase open circuit in a power distribution network caused by a lightning strike, the method comprising:

[0005] S1, Based on the three-phase voltage signals collected from each node in the faulty line, determine the line voltage of each node;

[0006] S2, determine the per-unit value of the steady-state amplitude of the line voltage at each node;

[0007] S3, determine whether the steady-state amplitude per unit value of the line voltage of each node meets the preset conditions, so as to determine the type of each node;

[0008] If the steady-state amplitude per unit value of the line voltage of the current node is equal to the first threshold, then the current node is determined to be located on the side of the disconnected power supply, and the current node is determined to be a type 1 node.

[0009] If at least two of the steady-state amplitude per-unit values ​​of the line voltage wave at the current node are less than the second threshold, then the current node is determined to be located on the disconnected load side, and the current node is determined to be a type 2 node.

[0010] S4. Based on the type of each node, the line segment between two nodes of different types is determined as the faulty section of the faulty line.

[0011] As a further improvement of the present invention, in S1, the nodes in the faulty line include three-phase nodes on the power supply side at the point of disconnection and three-phase nodes on the load side at the point of disconnection.

[0012] For the three-phase nodes A, B, and C on the power supply side at the point of disconnection, the line voltages of the three-phase nodes A, B, and C are calculated using the following formulas (1) to (3):

[0013]

[0014]

[0015]

[0016] In the formula, These are the three-phase voltage phasor values, These are the power supply side line voltages U AB U BC and U CA The vector value;

[0017] For the three-phase nodes A′, B′, and C′ on the load side at the point of disconnection, the line voltages of the three-phase nodes A′, B′, and C′ are calculated using the following formulas (4) to (7):

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] In the formula, These are the vector values ​​of the neutral-to-ground voltage on the power supply side and the neutral-to-ground voltage on the load side, respectively. Z2 is the load impedance, and R... d R d1 These represent the power supply-side transition resistance and the load-side transition resistance, respectively. C2 is the fault line-to-ground capacitance, C is the total-to-ground capacitance, γ = C / C2, and x is the proportion of the load-side-to-ground capacitance to the fault line-to-ground capacitance. The load-side line voltage U A′B′ U B′C′ U C′A′ The vector value.

[0024] As a further improvement of the present invention, the first threshold is set to 1.

[0025] As a further improvement of the present invention, in step S3, each variable Z2 and R is predefined. d R d1The range of values ​​for γ, x, and C is determined by randomly selecting a set of values ​​from the range of values ​​for each variable using the Monte Carlo method, and then substituting the selected values ​​into the calculation formulas (4) to (8) for the load side line voltage to perform multiple calculations to obtain the value of the second threshold.

[0026] As a further improvement of the present invention, the value of the second threshold is 0.7.

[0027] This invention also provides a device for locating single-phase line breakage in a power distribution network caused by lightning strikes, the device comprising:

[0028] The line voltage acquisition module is used to determine the line voltage of each node based on the three-phase voltage signals collected from each node in the faulty line.

[0029] The steady-state amplitude per-unit value acquisition module is used to determine the steady-state amplitude per-unit value of the line voltage at each node.

[0030] The node type determination module is used to determine whether the steady-state amplitude per unit value of the line voltage of each node meets the preset conditions, so as to determine the type of each node;

[0031] If the steady-state amplitude per unit value of the line voltage of the current node is equal to the first threshold, then the current node is determined to be located on the side of the disconnected power supply, and the current node is determined to be a type 1 node.

[0032] If at least two of the steady-state amplitude per-unit values ​​of the line voltage wave at the current node are less than the second threshold, then the current node is determined to be located on the disconnected load side, and the current node is determined to be a type 2 node.

[0033] The fault diagnosis module is used to determine the faulty section of the line between two different types of nodes.

[0034] As a further improvement of the present invention, in the line voltage acquisition module, the nodes in the faulty line include three-phase nodes on the power supply side at the break point and three-phase nodes on the load side at the break point.

[0035] For the three-phase nodes A, B, and C on the power supply side at the point of disconnection, the line voltages of the three-phase nodes A, B, and C are calculated using the following formulas (1) to (3):

[0036]

[0037]

[0038]

[0039] In the formula, These are the three-phase voltage phasor values, These are the power supply side line voltages U AB U BC and U CA The vector value;

[0040] For the three-phase nodes A′, B′, and C′ on the load side at the point of disconnection, the line voltages of the three-phase nodes A′, B′, and C′ are calculated using the following formulas (4) to (8):

[0041]

[0042]

[0043]

[0044]

[0045]

[0046] In the formula, These are the vector values ​​of the neutral-to-ground voltage on the power supply side and the neutral-to-ground voltage on the load side, respectively. Z2 is the load impedance, and R... d R d1 These represent the power supply-side transition resistance and the load-side transition resistance, respectively. C2 is the fault line-to-ground capacitance, C is the total-to-ground capacitance, γ = C / C2, and x is the proportion of the load-side-to-ground capacitance to the fault line-to-ground capacitance. The load-side line voltage U A′B′ U B′C′ U C′A′ The vector value.

[0047] As a further improvement of the present invention, in the node type determination module, the first threshold value is 1.

[0048] As a further improvement of the present invention, in the node type determination module, each variable Z2, R is predefined. d R d1 The range of values ​​for γ, x, and C is determined by randomly selecting a set of values ​​from the range of values ​​for each variable using the Monte Carlo method, and then substituting the selected values ​​into the calculation formulas (4) to (7) for the load side line voltage to obtain the value of the second threshold through multiple calculations.

[0049] As a further improvement of the present invention, the value of the second threshold is 0.7.

[0050] The beneficial effects of this invention are as follows:

[0051] Based on the different line voltage amplitudes at each node after a fault, the faulty section can be located, enabling timely and effective detection of the fault. This invention is applicable to faults with transition resistance varying within the range of 0Ω-1MΩ. This invention is applicable to all situations of single-phase faults, including single-phase faults, single-phase faults with one side grounded, and single-phase faults with both sides grounded, and is unaffected by other non-faulty lines, accurately locating the faulty section. Attached Figure Description

[0052] 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.

[0053] Figure 1 This is a flowchart illustrating a method for locating a single-phase disconnection in a power distribution network caused by a lightning strike, as described in an exemplary embodiment of the present invention.

[0054] Figure 2 This is an equivalent circuit diagram of a broken wire as described in an exemplary embodiment of the present invention;

[0055] Figure 3 This is a schematic diagram of a power distribution network model according to an exemplary embodiment of the present invention;

[0056] Figure 4 This is a probability diagram of the load-side line voltage being lower than a threshold, as described in an exemplary embodiment of the present invention. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0059] Furthermore, the terminology used in the description of this invention is for illustrative purposes only and is not intended to limit the scope of the invention. The terms "comprising" and / or "including" are used to specify the presence of said elements, steps, operations, and / or components, but do not exclude the presence or addition of one or more other elements, steps, operations, and / or components. The terms "first," "second," etc., may be used to describe various elements, do not represent an order, and do not limit these elements. Moreover, in the description of this invention, unless otherwise stated, "a plurality of" means two or more. These terms are used only to distinguish one element from another. These and / or other aspects become apparent in conjunction with the following drawings, and those skilled in the art will more readily understand the description of the embodiments of the invention. The drawings are used for illustrative purposes only to depict the embodiments of the invention. Those skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods shown in the invention can be employed without departing from the principles of the invention.

[0060] The present invention provides a method for locating single-phase open circuits in a power distribution network caused by lightning strikes, as described in this embodiment. Figure 1 As shown, the method includes:

[0061] S1, Based on the three-phase voltage signals collected from each node in the faulty line, determine the line voltage of each node;

[0062] S2, determine the per-unit value of the steady-state amplitude of the line voltage at each node;

[0063] S3, determine whether the steady-state amplitude per unit value of the line voltage of each node meets the preset conditions, so as to determine the type of each node;

[0064] If the steady-state amplitude per unit value of the line voltage of the current node is equal to the first threshold, then the current node is determined to be located on the side of the disconnected power supply, and the current node is determined to be a type 1 node, that is, the current node is a node on the side of the disconnected power supply.

[0065] If at least two of the steady-state amplitude per-unit values ​​of the line voltage wave of the current node are less than the second threshold, then the current node is determined to be located on the disconnected load side, and the current node is determined to be a type 2 node, that is, the current node is a node on the disconnected load side.

[0066] S4. Based on the type of each node, the line segment between two nodes of different types is determined as the faulty section of the faulty line.

[0067] The method described in this invention identifies and locates single-phase open-circuit faults in distribution networks caused by lightning strikes. It is applicable to all scenarios of single-phase open-circuit faults, including single-phase open-circuit faults, single-phase open-circuit faults with grounding on one side, and single-phase open-circuit faults with grounding on both sides. This method is particularly suitable for open-circuit faults with voltage variations within the range of 0Ω-1MΩ. Based on the differences in line voltage amplitudes at various nodes after the fault, the method locates the open-circuit fault section, enabling timely and effective detection of the fault.

[0068] Understandably, in S2, when calculating the steady-state amplitude per unit value of the line voltage at each node, different reference values ​​can be set for the three line voltages, or the same reference value can be set for the three line voltages.

[0069] In one embodiment, in S1, the nodes in the faulty line include three-phase nodes on the power supply side at the point of disconnection and three-phase nodes on the load side at the point of disconnection.

[0070] For the three-phase nodes A, B, and C on the power supply side at the point of disconnection, the line voltages of the three-phase nodes A, B, and C are calculated using the following formulas (1) to (3):

[0071]

[0072]

[0073]

[0074] In the formula, These are the three-phase voltage phasor values, i.e., the three-phase power supply E in the open-circuit equivalent circuit. A E B E C The voltage vector value, These are the power supply side line voltages U AB U BC and U CA The vector value;

[0075] For the three-phase nodes A′, B′, and C′ on the load side at the point of disconnection, the line voltages of the three-phase nodes A′, B′, and C′ are calculated using the following formulas (4) to (7):

[0076]

[0077]

[0078]

[0079]

[0080]

[0081] In the formula, These are the vector values ​​of the neutral-to-ground voltage on the power supply side and the neutral-to-ground voltage on the load side, respectively. Z2 is the load impedance, and R... d R d1 These are the power supply-side transition resistance and the load-side transition resistance, respectively. C2 is the fault line-to-ground capacitance, C is the total-to-ground capacitance, i.e., the total-to-ground capacitance of the equivalent circuit of the open circuit, γ = C / C2, and x is the proportion of the open circuit load-side to-ground capacitance to the fault line-to-ground capacitance. The load-side line voltage U A′B′ U B′C′ U C′A′ The vector value. Methods for locating fault sections based on changes in steady-state phase voltage of a line in related technologies are easily affected by the ground capacitance of non-faulty lines. The method described in this invention, compared to this method, calculates U... N U M When calculating the voltage offset between the two neutral points, the capacitance to ground of the non-faulty lines was taken into account, and subsequent calculations showed that the capacitance to ground of the non-faulty lines could be canceled out and would not affect U. N U M The calculation expression for the offset voltage between the two neutral points ensures that it is not affected by other non-faulty lines, thus enabling accurate location of the faulty section.

[0082] In S3, the determination of whether the preset conditions are met is based on... Figure 2 The first threshold and the second threshold are obtained by theoretical calculation of the disconnected circuit shown.

[0083] The equivalent circuit of the broken wire Figure 2 It is based on the set of non-faulty lines and faulty lines, where l1 represents all non-faulty lines, C1 is the ground capacitance of all non-faulty lines, Z1 is the load impedance of line l1, l2 represents the faulty line, A, B and C are the three-phase nodes on the power supply side of the broken line location, and A′, B′ and C′ are the three-phase nodes on the load side of the broken line location.

[0084] In one embodiment, the first threshold is set to 1. According to calculation formulas (1) to (3), the line voltage on the power supply side remains unchanged when a line breakage fault occurs and when no line breakage fault occurs, so the first threshold can be set to 1.

[0085] In one implementation, variables Z2 and R are predefined. d R d1 The range of values ​​for γ, x, and C is determined by randomly selecting a set of values ​​from the range of values ​​for each variable using the Monte Carlo method, and then substituting the selected values ​​into the calculation formulas (4) to (8) for the load side line voltage to perform multiple calculations to obtain the value of the second threshold.

[0086] The modulus of Z2 is set to vary from 20 to 5000Ω; since the power supply side is not grounded, R is preferably set. d 10MΩ; R d1 The variation range of γ is set to 0–1 MΩ; the variation range of x is set to 1–16; the variation range of x is set to 0–1. Since the single-phase grounding capacitor current of a 10kV neutral ungrounded distribution network is generally below 10A, the variation range of C is set to 0.184–1.84 μF. Using the Monte Carlo method, a set of values ​​is randomly selected from the variation range of each variable and substituted into the formula to calculate the value of the load-side line voltage. After multiple calculations (approximately 10,000), the probability curve of the load-side line voltage being below the threshold is obtained as shown below. Figure 4 As shown, the value of the second threshold is 0.7.

[0087] To verify the accuracy of this threshold, a distribution network model is configured for verification. This distribution network model can be constructed, for example, using power system simulation software such as PSCAD / EMTDC. The number of nodes may vary for different distribution network models; this invention does not impose specific limitations on the distribution network model used for verification.

[0088] This embodiment uses a distribution network model with six nodes, multiple feeders, and multiple branches for verification, such as... Figure 3 As shown, this is a 6-node model, consisting of a three-phase power supply, transformers, overhead lines, transition resistors, and three-phase loads. Specific parameters are as follows: the three-phase power supply voltage is 110kV; the transformer ratio on the power supply side is 110 / 10kV; the transformer ratio on the load side is 10 / 0.4kV; one non-faulty line is 15km long, and the other is 10km long; the distance between nodes on the faulty line is 0.5km; the transition resistor varies between 0Ω and 1MΩ; the three-phase load on the non-faulty line is 5MW + 4MVAR; and the three-phase load on the faulty line is 0.72MW + 0.35MVAR. Based on the statistical patterns of lightning-induced line breaks, a single-phase line breakage fault type with grounding via a transition resistor is set in the distribution network model. The fault point is located between nodes 2 and 4, 0.5km from both nodes. The transition resistor values ​​are set to 0Ω and 1MΩ, representing metallic grounding and high-resistance grounding, respectively. The distribution network simulation model was run to obtain the three-phase voltage waveforms of six nodes: nodes 1, 2, 3, 4, 5, and 6. After processing, the per-unit values ​​of the steady-state line voltage amplitudes of the six nodes were obtained. When calculating the per-unit values ​​of the steady-state line voltage amplitudes, the reference value was the rated line voltage of 10kV. The results are shown in Tables 1 and 2.

[0089] Table 1. Per-unit values ​​of steady-state line voltage amplitude at each node when the transition resistance is 0Ω.

[0090]

[0091] Table 2 shows the per-unit values ​​of the steady-state amplitude of the line voltage at each node when the transition resistance is 1 MΩ.

[0092]

[0093] Based on the results in Tables 1 and 2, under both types of transition resistance, for nodes 1, 2, and 3, the per-unit values ​​of the three line voltage steady-state amplitudes for each node are around 1. Therefore, nodes 1, 2, and 3 are determined to be type 1 nodes. For nodes 4, 5, and 6, two of the per-unit values ​​of the three line voltage steady-state amplitudes for each node are around 0.5, which is less than the threshold of 0.7. Therefore, nodes 4, 5, and 6 are determined to be type 2 nodes.

[0094] Since node 2 is a type 1 node and node 4 is a type 2 node, combined with the radial topology of the line (i.e., the geometry formed by the interconnection of various devices in the power distribution network model), according to step S4, the fault point is located between node 2 and node 4. This is consistent with the location of the simulated fault point, which confirms the effectiveness of the method described in this invention for fault location, and it is also effective for fault location when there is high resistance grounding.

[0095] The present invention provides a device for locating single-phase line breakage in a power distribution network caused by lightning strikes, the device comprising:

[0096] The line voltage acquisition module is used to determine the line voltage of each node based on the three-phase voltage signals collected from each node in the faulty line.

[0097] The steady-state amplitude per-unit value acquisition module is used to determine the steady-state amplitude per-unit value of the line voltage at each node.

[0098] The node type determination module is used to determine whether the steady-state amplitude per unit value of the line voltage of each node meets the preset conditions, so as to determine the type of each node;

[0099] If the steady-state amplitude per unit value of the line voltage of the current node is equal to the first threshold, then the current node is determined to be located on the side of the disconnected power supply, and the current node is determined to be a type 1 node.

[0100] If at least two of the steady-state amplitude per-unit values ​​of the line voltage wave at the current node are less than the second threshold, then the current node is determined to be located on the disconnected load side, and the current node is determined to be a type 2 node.

[0101] The fault diagnosis module is used to determine the faulty section of the line between two different types of nodes.

[0102] In one embodiment, the line voltage acquisition module calculates the power supply side line voltage using the following formulas (1) to (3):

[0103]

[0104]

[0105]

[0106] In the formula, These are the three-phase voltage phasor values, These are the power supply side line voltages U AB U BC and U CA The vector value;

[0107] The load-side line voltage is calculated using the following formulas (4) to (8):

[0108]

[0109]

[0110]

[0111]

[0112]

[0113] In the formula, These are the vector values ​​of the neutral-to-ground voltage on the power supply side and the neutral-to-ground voltage on the load side, respectively. Z2 is the load impedance, and R... d R d1 These represent the power supply-side transition resistance and the load-side transition resistance, respectively. C2 is the fault line-to-ground capacitance, C is the total-to-ground capacitance, γ = C / C2, and x is the proportion of the load-side-to-ground capacitance to the fault line-to-ground capacitance. The load-side line voltage U A′B′ U B′C′ U C′A′ The vector value.

[0114] In one embodiment, the first threshold value in the node type determination module is 1.

[0115] In one implementation, the node type determination module predefines variables Z2 and R. d R d1The range of values ​​for γ, x, and C is determined by randomly selecting a set of values ​​from the range of values ​​for each variable using the Monte Carlo method, and then substituting the selected values ​​into the calculation formulas (4) to (7) for the load side line voltage to obtain the value of the second threshold through multiple calculations.

[0116] In one implementation, the value of the second threshold is 0.7.

[0117] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0118] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0119] Those skilled in the art will understand that although the invention has been described with reference to exemplary embodiments, various changes may be made and its elements may be substituted with equivalents without departing from the scope of the invention. Furthermore, many modifications may be made to adapt particular situations or materials to the teachings of the invention without departing from the essential scope of the invention. Therefore, the invention is not limited to the specific embodiments disclosed, but rather the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A method for locating a single-phase open circuit in a power distribution network caused by a lightning strike, characterized in that, The method includes: S1, Based on the three-phase voltage signals collected from each node in the faulty line, determine the line voltage of each node; S2, determine the per-unit value of the steady-state amplitude of the line voltage at each node; S3, determine whether the steady-state amplitude per unit value of the line voltage of each node meets the preset conditions, so as to determine the type of each node; If the steady-state amplitude per unit value of the line voltage of the current node is equal to the first threshold, then the current node is determined to be located on the side of the disconnected power supply, and the current node is determined to be a type 1 node. If at least two of the steady-state amplitude per-unit values ​​of the line voltage wave at the current node are less than the second threshold, then the current node is determined to be located on the disconnected load side, and the current node is determined to be a type 2 node. S4, based on the type of each node, the line segment between two nodes of different types in each node is determined as the fault section of the faulty line; In S1, the nodes in the faulty line include the three-phase nodes on the power supply side at the point of disconnection and the three-phase nodes on the load side at the point of disconnection. For the three-phase nodes A, B, and C on the power supply side at the point of disconnection, the line voltages of the three-phase nodes A, B, and C are calculated using the following formulas (1) to (3): （1） （2） （3） In the formula, These are the three-phase voltage vector values, These are the power supply side line voltages U AB U BC and U CA The vector value; For the three-phase nodes A', B', and C' on the load side at the point of disconnection, the line voltages of the three-phase nodes A', B', and C' are calculated using the following formulas (4) to (8): （4） （5） （6） （7） （8） In the formula, These are the vector values ​​of the neutral-to-ground voltage on the power supply side and the neutral-to-ground voltage on the load side, respectively. For load impedance, These are the power supply side transition resistance and the load side transition resistance, respectively. This is the capacitance to ground of the faulty line. Total capacitance to ground , This represents the ratio of the capacitance to ground on the load side of the disconnected line to the total capacitance to ground on the faulty line. These are the line voltages on the load side. The vector value.

2. The method as described in claim 1, wherein, In S3, the value of the first threshold is 1.

3. The method as described in claim 1, wherein, In S3, each variable is predefined. , , , , The range of values ​​is determined by using the Monte Carlo method to randomly select a set of values ​​from the range of values ​​of each variable, and then substituting the selected values ​​into the calculation formulas (4) to (8) for the load side line voltage to perform multiple calculations to obtain the value of the second threshold.

4. The method of claim 3, wherein, The value of the second threshold is 0.

7.

5. A device for locating single-phase disconnection in a power distribution network caused by lightning strikes, characterized in that, The device includes: The line voltage acquisition module is used to determine the line voltage of each node based on the three-phase voltage signals collected from each node in the faulty line. The steady-state amplitude per-unit value acquisition module is used to determine the steady-state amplitude per-unit value of the line voltage at each node. The node type determination module is used to determine whether the steady-state amplitude per unit value of the line voltage of each node meets the preset conditions, so as to determine the type of each node; If the steady-state amplitude per unit value of the line voltage of the current node is equal to the first threshold, then the current node is determined to be located on the side of the disconnected power supply, and the current node is determined to be a type 1 node. If at least two of the steady-state amplitude per-unit values ​​of the line voltage wave at the current node are less than the second threshold, then the current node is determined to be located on the disconnected load side, and the current node is determined to be a type 2 node. The fault diagnosis module is used to determine the faulty section of the line between two different types of nodes. In the line voltage acquisition module, the nodes in the faulty line include the three-phase nodes on the power supply side at the point of disconnection and the three-phase nodes on the load side at the point of disconnection. For the three-phase nodes A, B, and C on the power supply side at the point of disconnection, the line voltages of the three-phase nodes A, B, and C are calculated using the following formulas (1) to (3): （1） （2） （3） In the formula, These are the three-phase voltage vector values, These are the power supply side line voltages U AB U BC and U CA The vector value; For the three-phase nodes A', B', and C' on the load side at the point of disconnection, the line voltages of the three-phase nodes A', B', and C' are calculated using the following formulas (4) to (8): （4） （5） （6） （7） （8） In the formula, These are the vector values ​​of the neutral-to-ground voltage on the power supply side and the neutral-to-ground voltage on the load side, respectively. For load impedance, These are the power supply side transition resistance and the load side transition resistance, respectively. This is the capacitance to ground of the faulty line. Total capacitance to ground , This represents the ratio of the capacitance to ground on the load side of the disconnected line to the total capacitance to ground on the faulty line. These are the line voltages on the load side. The vector value.

6. The apparatus of claim 5, wherein, In the node type determination module, the first threshold value is 1.

7. The apparatus of claim 5, wherein, In the node type determination module, various variables are predefined. , , , , The range of values ​​is determined by using the Monte Carlo method to randomly select a set of values ​​from the range of values ​​of each variable, and then substituting the selected values ​​into the calculation formulas (4) to (7) of the load side line voltage to perform multiple calculations to obtain the value of the second threshold.

8. The apparatus of claim 7, wherein, The value of the second threshold is 0.7.

Images