Method for positioning the ground of the t-line of the at traction network of the fused feeder circuit

Abstract

The application belongs to the technical field of power supply line fault ranging, and discloses a kind of AT traction network T line grounding positioning calculation method fusing feeder loop, including expanding feeder loop into the 0th power supply subarea, and constructing AT traction network circuit model based on "N+1" power supply subareas;With Beidou timing time as the benchmark, the bus fault voltage after each grounding fault and T line fault current are synchronously collected;Combined with circuit topology, bus fault voltage, T line fault current, and using uplink and downlink T line current, a fault ranging calculation model is constructed without train;According to the T line fault current of each station, it is determined whether the fault power supply subarea has a train, and after eliminating the influence of train shunting, the fault distance is calculated by substituting into the fault ranging calculation model;Finally, accurate positioning is realized according to the mapping relationship between the network point and the positive line pole position label.The application includes feeder loop into the ranging system, significantly improves the positioning accuracy in the long feeder scene, and does not need to increase additional measuring equipment, and has strong engineering applicability.

Description

Technical Field

[0001] This invention belongs to the field of power line fault location technology, and relates to a method for calculating the grounding location of the T-line of an AT traction network that integrates feeder circuits. Background Technology

[0002] High-speed and heavy-haul railways mostly employ fully parallel autotransformer (AT) power supply. AT traction networks have complex structures, operate in variable environments, and are constantly subjected to vibrations and shocks from the pantograph, making them prone to various short-circuit faults. Since AT traction networks have no backup during operation, a serious short circuit or line break can cause widespread train delays or even traffic accidents. The ability to quickly restore power to the AT traction network largely depends on the time required to locate the fault; therefore, feeder protection devices must possess rapid and accurate fault location capabilities.

[0003] Currently, the mainstream method for fault location in AT traction networks is based on the current distribution relationship of each conductor in the main line. However, traditional fault location calculation models typically do not take into account the feeder circuit (i.e., the power supply line from the traction substation busbar to the main line contact network). In conventional railway applications, the feeder circuit length is relatively short, and the resulting location error is still within the allowable range of industry standards, thus it has not received sufficient attention. However, with the continuous development of high-altitude railways, traction substations often cannot supply power to the contact network at close range, resulting in a significant increase in feeder circuit length, and its impact on fault current distribution can no longer be ignored. According to incomplete statistics, the average location error of the traction network in mountainous railways is about twice that of conventional lines, and the error in some sections seriously exceeds the standard, with the T-line grounding fault, which has the highest failure rate, being particularly prominent.

[0004] Due to limitations in current understanding, no complete mathematical method has yet been established, either domestically or internationally, to accurately describe the operating characteristics of fully parallel AT power supply systems. This makes it difficult to construct a detailed circuit topology covering the feeder loops from a theoretical perspective. In recent years, the rapid development of real-time digital simulation technology has provided a new technical approach for studying the electrical and load characteristics of AT power supply systems. This helps to optimize fault location schemes for AT traction networks by combining current and voltage variation patterns.

[0005] In summary, existing fault location calculation methods for AT traction networks, due to neglecting the influence of feeder circuits, exhibit significantly increased location errors in high-altitude and long-feeder scenarios, making them unsuitable for engineering requirements. Therefore, there is an urgent need for an AT traction network T-line grounding location calculation method that incorporates feeder circuits to correct the distortion issues of existing current ratio-based fault location methods. Summary of the Invention

[0006] The purpose of this invention is to provide a method for calculating the grounding location of the T-line in an AT traction network that integrates the feeder circuit, in order to solve the problem of large positioning errors in long feeder scenarios caused by neglecting the feeder circuit in existing AT traction network fault location methods.

[0007] To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0008] A method for calculating the grounding location of the T-line in an AT traction network with integrated feeder circuits includes the following steps:

[0009] S1. Extend the feeder circuit of the traction substation into an independent 0th power supply zone, construct an AT traction network circuit model based on "N+1" power supply zones, and generate the corresponding circuit topology.

[0010] S2. Using BeiDou time as the time reference, the bus voltage and T-line current waveform data after the ground fault are simultaneously extracted from the feeder protection devices of each station, and used as the bus fault voltage and T-line fault current of each station when the T-line is ground faulted; where each station includes traction substation, each AT station and section station.

[0011] S3. Combining the circuit topology with the fault voltage of each bus and the fault current of the T-line, and using the ratio of the up and down T-line currents, construct a T-line grounding fault location calculation model when there are no trains in the power supply zone where the fault is located.

[0012] S4. Determine the power supply zone where the fault is located based on the fault current of each T-line in the same time period, and determine whether there is a train in the power supply zone where the fault is located. When there is no train in the power supply zone where the fault is located, directly use the T-line grounding fault ranging calculation model in step S3 to calculate the fault distance. When there is a train in the power supply zone where the fault is located, after eliminating the influence of train diversion, use the T-line grounding fault ranging calculation model in step S3 to calculate the fault distance.

[0013] S5. Based on the fault distance calculated in step S4, and according to the mapping relationship between the feeder circuit entry point and the pole position number on the main line, the fault is accurately located based on the pole position information on the main line.

[0014] As a limitation, the specific process of step S1 includes:

[0015] Define a single power supply arm as a complete power supply section, and divide the entire power supply section into N power supply zones according to the location of each AT station;

[0016] Extend the feeder circuit of the traction substation to the 0th power supply section, form an AT traction network circuit model based on "N+1" power supply sections, and generate the corresponding circuit topology.

[0017] In the AT traction network circuit model, except for the 0th power supply zone, the beginning and end of the T-line and F-line of any power supply zone are connected in parallel through a cross-connecting line.

[0018] As a second limitation, in step S2, the bus voltage and T-line current recording data of the 5th cycle after the ground fault are simultaneously extracted from each feeder protection device.

[0019] As a third limitation, in step S3, the calculation model for T-track grounding fault location when there are no trains in the fault section includes:

[0020] ① The fault is located in the 0th power supply zone, and the voltage of the T-line bus of the traction substation is... Less than the voltage of the F-line bus of the traction substation At that time, the fault distance from the fault point to the feeder circuit entry point is... for:

[0021] ;

[0022] in, The feeder current of the T-line in the traction substation is A; The unit impedance of the T-line in the traction substation is expressed in Ω / km.

[0023] ② The fault point is located in the first power supply zone, and the feeder current of the T-line of the traction substation is... Greater than the feeder current of line F of the traction substation At that time, the fault distance from the fault point to the feeder circuit entry point is... for:

[0024] ;

[0025] in, The current of the upstream T-line of the traction substation is A; The current of the down-line T of the traction substation is A; The current of the upstream T line of 1#AT, in A; The current of the upstream T line of 2#AT, in A; The length of the feeder circuit in the traction substation is in km; The unit impedance of the feeder circuit in the traction substation is expressed in Ω / km. The distance from the feeder loop entry point to substation #1 is in km; The unit impedance of the positive line T at 1#AT, in Ω / km;

[0026] ③ The fault point is located in the second power supply zone, and the current of the upstream T line of 1#AT is... The current of the F line above 1#AT is greater than the current of the F line above 1#AT. At that time, the fault distance from the fault point to the feeder circuit entry point is... for:

[0027] ;

[0028] in, The current of the T-line downstream of 1#AT is in A;

[0029] ④ The fault point is located in the 3rd power supply zone, and the current of the upstream T line of 2#AT is... The current of the F line above 2#AT is greater than the current of the F line above 2#AT. At that time, the fault distance from the fault point to the feeder circuit entry point is... for:

[0030] ;

[0031] in, The current of the upstream T line of 3#AT, in A; The current of the T-line downstream of 2#AT is in A; The total length of the main line from station 1#AT to station 2#AT, in km;

[0032] ⑤ The fault point is located at the first Power supply zoning, And the current of the T-line above j-1#AT The current of the F line above j-1#AT is greater than the current of the F line above j-1#AT. At that time, the fault distance from the fault point to the feeder circuit entry point is... for:

[0033] ;

[0034] in, The current of the T-line flowing down through j-1#AT, in A; The current of the upstream T line of j-1#AT, in A; The current of the upstream T line of j-2#AT, in A; The current of the upstream T line of j#AT, in A; The total length of the main line from j-2#AT to j-1#AT, in km; The total length of the main line from j-3#AT to j-2#AT is in km.

[0035] As a fourth limitation, the specific process for determining the power supply zone where the fault occurs in step S4 is as follows:

[0036] Compare the T-line fault currents collected by the traction substation, each AT station, and the section station during the same time period, select the two sets with the largest values, and determine the power supply section corresponding to the two sets of data as the power supply section where the fault occurs.

[0037] The specific process for determining whether there are trains in the power supply section where the fault is located is as follows:

[0038] Based on Kirchhoff's current law, the current balance relationship at the T-line branch point at the end of the power supply zone where the fault occurs is verified, and the balance error is set to a certain value. If the actual balance error ≥ If the fault occurs, it is determined that there is a train in the power supply section where the fault is located; otherwise, it is determined that there is no train in the power supply section where the fault is located.

[0039] The balance error The calculation method is as follows:

[0040] ;

[0041] in, This represents the total number of branches at the T-line branch point, excluding train diversion branches; The first branch point of the T-line connected to the flow Current values ​​of each branch; balance error The range is between 20 and 50A;

[0042] When there are trains in the power supply zone where the fault occurs, the method to eliminate the impact of train diversion is: utilizing the balance error. The current of the train shunt branch within the power supply section where the fault occurred is verified, specifically:

[0043] ;

[0044] in, The current in A is the upstream T-line current of the i#AT station at the end of the power supply zone where the fault occurs; The current of the T-line above i+1#AT is in A.

[0045] The present invention, by adopting the above-described technical solution, achieves the following technical advancements compared to existing technologies:

[0046] (1) This invention expands the feeder circuit of the traction substation into an independent 0th power supply zone, and constructs an AT traction network circuit model based on “N+1” power supply zones, thus realizing the inclusion of the feeder circuit into the fault location calculation system. Compared with the existing traditional location method that ignores the feeder circuit, this invention fully considers the influence of the feeder circuit length and impedance on the fault current distribution, and fundamentally solves the technical problem of significantly increased positioning error of traditional methods in high-altitude and long feeder scenarios.

[0047] (2) This invention uses Beidou time synchronization to collect bus voltage and T-line current waveform data after grounding faults in traction substations, AT stations and section substations, and uses the ratio of up and down T-line currents to construct a T-line grounding fault ranging calculation model when there are no trains in the power supply section where the fault is located. No additional measuring equipment or modification of existing facilities is required. High-precision positioning can be achieved using only existing feeder protection devices. The engineering implementation cost is low and the promotion difficulty is small.

[0048] (3) This invention uses Kirchhoff's current law to verify the current balance relationship at the T-line branch point at the end of the power supply zone where the fault is located, accurately determine whether there is a train running in the zone, and eliminate the influence of train diversion on the fault current, effectively solving the problem of distance measurement distortion caused by train diversion, and ensuring the full working condition adaptability of fault location.

[0049] (4) This invention directly converts the calculated fault distance into pole position information required for on-site line patrol by mapping the entry point to the pole position number on the main line, which makes it easier for maintenance personnel to reach the fault point quickly and significantly shortens the fault investigation time.

[0050] In summary, this invention is applicable to fully parallel AT traction power supply systems in high-altitude, long-feeder scenarios, and has good engineering applicability and promotional value. Attached Figure Description

[0051] Figure 1 The diagram shown is a flowchart of a method according to an embodiment of the present invention;

[0052] Figure 2 The diagram shown is a circuit topology diagram of an embodiment of the present invention;

[0053] Figure 3 The diagram shown is a schematic of the RTplus smart grid hardware-in-the-loop simulation platform in an embodiment of the present invention.

[0054] Figure 4 The figure shows a real-time digital simulation model of the AT traction network built according to an embodiment of the present invention.

[0055] Figure 5 The image shows the T-line current recording data according to an embodiment of the present invention. Detailed Implementation

[0056] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0057] Example: A method for calculating the grounding location of the T-line in an AT traction network with integrated feeder circuits.

[0058] like Figure 1As shown, this embodiment is a method for calculating the grounding location of the T-line in an AT traction network with integrated feeder circuits, including the following steps:

[0059] S1. Extend the feeder circuit of the traction substation into an independent power supply zone 0, construct an AT traction network circuit model based on “N+1” power supply zones, and generate the corresponding circuit topology.

[0060] The specific process of this step includes:

[0061] S11. Define a single power supply arm as a complete power supply section. The power supply arm has N AT stations. Divide the entire power supply section into N power supply zones according to the location of each AT station.

[0062] In this context, a feeder circuit refers to the power supply line from the traction substation busbar to the main line contact network. A single power supply arm refers to a contact network section in an electrified railway where a traction substation supplies power to one side (or one end), i.e., a "single-sided power supply" arm. This section only obtains power from the traction substation at one end. To distinguish AT substations at different locations within the same power supply arm, they are marked with sequential numbering such as 1#AT substation, 2#AT substation, etc., where "#" is a common numbering symbol in the railway traction substation numbering rules. The end node of the first power supply section is 1#AT substation, the first end node of the second power supply section is 1#AT substation, the end node is 2#AT substation, and so on. The section substation is located at the end of the Nth power supply section.

[0063] S12. Extend the feeder circuit of the traction substation to the 0th power supply section of the power supply zone, form an AT traction network circuit model based on "N+1" power supply sections, and generate the corresponding circuit topology to enable the circuit model to cover all line fault points.

[0064] S13. In the AT traction network circuit model, except for the 0th power supply zone, the beginning and end of the T line and F line of any power supply zone are connected in parallel through the cross-connection line, and the current of each node follows Kirchhoff's current law.

[0065] S2. Using BeiDou time as the time reference, simultaneously extract the bus voltage and T-line current recording data of the 5th cycle after the ground fault from the feeder protection devices of the traction substation, each AT station and the section station, as the bus fault voltage and T-line fault current of each station when the T-line is grounded.

[0066] S3. Ignoring the influence of climatic conditions such as temperature and humidity on the line parameters of the AT traction network circuit model, and combining the circuit topology with the fault voltage of each bus and the fault current of the T-line, and using the ratio of the up and down T-line currents, a T-line grounding fault location calculation model is constructed when there are no trains in the power supply zone where the fault is located.

[0067] In this step, the calculation model for T-track grounding fault location when there are no trains in the fault section includes:

[0068] ① The fault is located in the 0th power supply zone, and the voltage of the T-line bus of the traction substation is... Less than the voltage of the F-line bus of the traction substation At that time, the fault distance from the fault point to the feeder circuit entry point is... for:

[0069] ;

[0070] in, The feeder current of the T-line in the traction substation is A; The unit impedance of the T-line in the traction substation is expressed in Ω / km.

[0071] ② The fault point is located in the first power supply zone, and the feeder current of the T-line of the traction substation is... Greater than the feeder current of line F of the traction substation At that time, the fault distance from the fault point to the feeder circuit entry point is... for:

[0072] ;

[0073] in, The current of the upstream T-line of the traction substation is A; The current of the down-line T of the traction substation is A; The current of the upstream T line of 1#AT, in A; The current of the upstream T line of 2#AT, in A; The length of the feeder circuit in the traction substation is in km; The unit impedance of the feeder circuit in the traction substation is expressed in Ω / km. The distance from the feeder loop entry point to substation #1 is in km; The unit impedance of the positive line T at 1#AT, in Ω / km;

[0074] ③ The fault point is located in the second power supply zone, and the current of the upstream T line of 1#AT is... The current of the F line above 1#AT is greater than the current of the F line above 1#AT. At that time, the fault distance from the fault point to the feeder circuit entry point is... for:

[0075] ;

[0076] in, The current of the T-line downstream of 1#AT is in A;

[0077] ④ The fault point is located in the 3rd power supply zone, and the current of the upstream T line of 2#AT is... The current of the F line above 2#AT is greater than the current of the F line above 2#AT. At that time, the fault distance from the fault point to the feeder circuit entry point is... for:

[0078] ;

[0079] in, The current of the upstream T line of 3#AT, in A; The current of the T-line downstream of 2#AT is in A; The total length of the main line from station 1#AT to station 2#AT, in km;

[0080] ⑤ The fault point is located at the first Power supply zoning, And the current of the T-line above j-1#AT The current of the F line above j-1#AT is greater than the current of the F line above j-1#AT. At that time, the fault distance from the fault point to the feeder circuit entry point is... for:

[0081] ;

[0082] in, The current of the T-line flowing down through j-1#AT is in A; The current of the upstream T line of j-1#AT, in A; The current of the upstream T line of j-2#AT, in A; The current of the upstream T line of j#AT, in A; The total length of the main line from j-2#AT to j-1#AT, in km; The total length of the main line from j-3#AT to j-2#AT is in km.

[0083] S4. Determine the power supply zone where the fault is located based on the fault current of each T-line in the same time period, and determine whether there is a train in the power supply zone where the fault is located. When there is no train in the power supply zone where the fault is located, directly use the T-line grounding fault ranging calculation model in step S3 to calculate the fault distance. When there is a train in the power supply zone where the fault is located, after eliminating the influence of train diversion, use the T-line grounding fault ranging calculation model in step S3 to calculate the fault distance.

[0084] In this step, the specific process for determining the power supply zone where the fault occurs is as follows:

[0085] Compare the T-line fault currents collected by the traction substation, each AT station, and the section station during the same time period, select the two sets with the largest values, and determine the power supply section corresponding to the two sets of data as the power supply section where the fault occurs.

[0086] If the fault current of the T-line in both the traction substation and the No. 1 AT substation is greater than the current in the section substation, then the fault is determined to be located in the first power supply section. This determination principle is based on the attenuation law of the fault current along the power supply arm: when a ground fault occurs on the T-line, the fault current is shunted from the fault point to both ends of the power supply arm, and the closer to the fault point, the greater the measured current.

[0087] The specific process for determining whether there are trains in the power supply section where the fault is located is as follows:

[0088] Based on Kirchhoff's current law, the current balance relationship at the T-line branch point at the end of the power supply zone where the fault occurs is verified, and the balance error is set to a certain value. If the actual balance error ≥ If the fault is detected, it is determined that there is a train in the power supply section where the fault is located; otherwise, it is determined that there is no train in the power supply section where the fault is located.

[0089] Balance error The calculation method is as follows:

[0090] ;

[0091] in, This represents the total number of branches at the T-line branch point, excluding train diversion branches; The first branch point of the T-line connected to the flow Current values ​​of each branch; balance error The range is between 20 and 50A.

[0092] When there are trains in the power supply zone where the fault occurs, the method to eliminate the impact of train diversion is: utilizing the balance error. The current of the train shunt branch within the power supply section where the fault occurred is verified, specifically:

[0093] ;

[0094] in, The current in A is the upstream T-line current of the i#AT station at the end of the power supply zone where the fault occurs; The current of the T-line above i+1#AT is in A.

[0095] S5. Based on the fault distance calculated in step S4, and according to the mapping relationship between the feeder circuit entry point and the pole position number on the main line, the fault is accurately located based on the pole position information on the main line.

[0096] To verify the effectiveness of this method, this embodiment provides a typical example where the traction substation busbar is connected to the power supply arm via a feeder circuit, and a power supply zone is divided using an AT (Automatic Transmission Unit). For example... Figure 2The diagram shows the circuit topology when only one AT (Automatic Transmission Unit) is used to divide the power supply into zones. The lengths of the first and second power supply zones are both 10km. The lengths of the uplink and downlink feeder loops of the traction substation are equal, both 0.2km. A T-line grounding fault point is set every 2km on the power supply arm. Before simulation, the following basic parameters were determined based on the actual application scenario: the rated power supply capacity of the traction substation is 31.5MVA, and the rated bus voltage of the traction substation, AT station, and zone substation are all 27.5kV. During simulation, the configured capacity is directly adopted as the rated power supply capacity; ignoring the influence of internal resistance, the calculated equivalent internal reactance of the traction transformer is approximately 0.087Ω.

[0097] like Figure 3 As shown, this embodiment utilizes the RTplus smart grid hardware-in-the-loop simulation platform for simulation. The AT traction network real-time digital simulation model built on the RTplus smart grid hardware-in-the-loop simulation platform is as follows: Figure 4 As shown. The model parameters are set based on the basic parameters mentioned above.

[0098] By setting different locations for T-line grounding faults, the bus voltage and T-line current waveform data of the 5th cycle after the grounding fault were obtained. These waveforms were used as the bus fault voltage and T-line fault current at each location during the T-line grounding fault, resulting in... Figure 5 The T-line current recording data is shown.

[0099] To illustrate the impact of feeder circuit and train diversion on fault location, Table 1 compares the calculation results of the T-line grounding fault location calculation model constructed in this embodiment with those of the traditional fault location model when there are no trains in the power supply section where the fault is located; Table 2 compares the calculation results of the T-line grounding fault location calculation model constructed in this embodiment with and without considering train diversion when there are trains in the power supply section where the fault is located.

[0100] Table 1. Comparison of calculation results between the T-line grounding fault location calculation model and the traditional fault location model.

[0101]

[0102] As shown in Table 1, the fault current and fault location during a ground fault in the T-line of the AT traction network have the following characteristics: (1) Within any power supply zone, the fault current of the T-line decreases as the fault distance increases; (2) Within the entire power supply section, the calculation error of the T-line ground fault location calculation model constructed in this embodiment is less than 1 / 10 of that of the traditional location model, and the maximum absolute error is less than 20m, which is about 1 / 25 of the standard 500m; (3) The fault location error near the traction substation and the AT station is relatively large because the increase in current will slightly increase the actual equivalent internal impedance of the transformer. Compared with the traditional fault location model, the T-line ground fault location calculation model constructed in this embodiment has good calculation accuracy, and its calculation accuracy increases significantly with the increase in the length of the power supply circuit.

[0103] Table 2 Comparison of calculation results for T-line ground fault location calculation model with and without considering vehicle diversion.

[0104]

[0105] As shown in Table 2, when the T-line of the AT traction network is grounded and there are trains in the fault section, the train diversion has a significant impact on the calculation accuracy of the T-line grounding fault location calculation model constructed in this embodiment. The maximum location error before current correction may reach 1.2km, which is equivalent to 2.2km in the traditional location model. The further the fault point is from the network connection point, the greater the location error before current correction. After correcting the current parameters, the calculation accuracy of the T-line grounding fault location calculation model constructed in this embodiment returns to normal, that is, the absolute error is basically controlled at around 20m.

[0106] In summary, this invention significantly improves fault location accuracy by treating feeder circuits as independent sections and constructing an AT traction network circuit model based on "N+1" power supply zones, with virtually no increase in computational load. While maintaining the original computational structure, this invention improves both the absolute and relative accuracy of fault location by an order of magnitude, fully demonstrating its excellent balance between improving location performance and maintaining computational efficiency. It possesses outstanding substantive features and significant advancements.

[0107] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating the grounding location of the T-line in an AT traction network with integrated feeder circuits, characterized in that, Includes the following steps: S1. Extend the feeder circuit of the traction substation into an independent 0th power supply zone, construct an AT traction network circuit model based on "N+1" power supply zones, and generate the corresponding circuit topology. S2. Using BeiDou time as the time reference, the bus voltage and T-line current waveform data after the ground fault are simultaneously extracted from the feeder protection devices of each station, and used as the bus fault voltage and T-line fault current of each station when the T-line is ground faulted; where each station includes traction substation, each AT station and section station. S3. Combining the circuit topology with the fault voltage of each bus and the fault current of the T-line, and using the ratio of the up and down T-line currents, construct a T-line grounding fault location calculation model when there are no trains in the power supply zone where the fault is located. S4. Determine the power supply zone where the fault is located based on the fault current of each T-line in the same time period, and determine whether there is a train in the power supply zone where the fault is located. When there is no train in the power supply zone where the fault is located, directly use the T-line grounding fault ranging calculation model in step S3 to calculate the fault distance. When there is a train in the power supply zone where the fault is located, after eliminating the influence of train diversion, use the T-line grounding fault ranging calculation model in step S3 to calculate the fault distance. S5. Based on the fault distance calculated in step S4, and according to the mapping relationship between the feeder circuit entry point and the pole position number on the main line, the fault is accurately located based on the pole position information on the main line.

2. The method for calculating the grounding location of the T-line of the AT traction network with integrated feeder circuit according to claim 1, characterized in that, The specific process of step S1 includes: Define a single power supply arm as a complete power supply section, and divide the entire power supply section into N power supply zones according to the location of each AT station; Extend the feeder circuit of the traction substation to the 0th power supply section of the power supply zone, form an AT traction network circuit model based on "N+1" power supply sections, and generate the corresponding circuit topology. In the AT traction network circuit model, except for the 0th power supply zone, the beginning and end of the T-line and F-line of any power supply zone are connected in parallel through a cross-connecting line.

3. The method for calculating the grounding location of the T-line of the AT traction network in the fused feeder circuit according to claim 1 or 2, characterized in that, In step S2, the bus voltage and T-line current recording data of the 5th cycle after the ground fault are simultaneously extracted from the feeder protection devices of each feeder.

4. The method for calculating the grounding location of the T-line of the AT traction network in the fused feeder circuit according to claim 1 or 2, characterized in that, In step S3, the calculation model for T-track grounding fault location when there are no trains in the fault section includes: ① The fault is located in the 0th power supply zone, and the voltage of the T-line bus of the traction substation is... Less than the voltage of the F-line bus of the traction substation At that time, the fault distance from the fault point to the feeder circuit entry point is... for: ； in, The feeder current of the T-line in the traction substation is A; The unit impedance of the T-line in the traction substation is expressed in Ω / km. ② The fault point is located in the first power supply zone, and the feeder current of the T-line of the traction substation is... Greater than the feeder current of line F of the traction substation At that time, the fault distance from the fault point to the feeder circuit entry point is... for: ； in, The current of the upstream T-line of the traction substation is A; The current of the down-line T of the traction substation is A; The current of the upstream T line of 1#AT, in A; The current of the upstream T line of 2#AT, in A; The length of the feeder circuit in the traction substation is in km; The unit impedance of the feeder circuit in the traction substation is expressed in Ω / km. The distance from the feeder circuit entry point to substation #1 is in km; The unit impedance of the positive line T at 1#AT, in Ω / km; ③ The fault point is located in the second power supply zone, and the current of the upstream T line of 1#AT is... The current of the F line above 1#AT is greater than the current of the F line above 1#AT. At that time, the fault distance from the fault point to the feeder circuit entry point is... for: ； in, The current of the T-line downstream of 1#AT is in A; ④ The fault point is located in the 3rd power supply zone, and the current of the upstream T line of 2#AT is... The current of the F line above 2#AT is greater than the current of the F line above 2#AT. At that time, the fault distance from the fault point to the feeder circuit entry point is... for: ； in, The current of the upstream T line of 3#AT, in A; The current of the T-line downstream of 2#AT is in A; The total length of the main line from station 1#AT to station 2#AT, in km; ⑤ The fault point is located at the first Power supply zoning, And the current of the T-line above j-1#AT The current of the F line above j-1#AT is greater than the current of the F line above j-1#AT. At that time, the fault distance from the fault point to the feeder circuit entry point is... for: ； in, The current of the T-line flowing down through j-1#AT is in A; The current of the upstream T line of j-1#AT, in A; The current of the upstream T line of j-2#AT, in A; The current of the upstream T line of j#AT, in A; The total length of the main line from j-2#AT to j-1#AT, in km; The total length of the main line from j-3#AT to j-2#AT is in km.

5. The method for calculating the grounding location of the T-line of the AT traction network in the fused feeder circuit according to claim 1 or 2, characterized in that, In step S4, the specific process for determining the power supply zone where the fault occurs is as follows: Compare the T-line fault currents collected by the traction substation, each AT station, and the section station during the same time period, select the two sets with the largest values, and determine the power supply section corresponding to the two sets of data as the power supply section where the fault occurs. The specific process for determining whether there are trains in the power supply section where the fault is located is as follows: Based on Kirchhoff's current law, the current balance relationship at the T-line branch point at the end of the power supply zone where the fault occurs is verified, and the balance error is set to a certain value. If the actual balance error ≥ If the fault occurs, it is determined that there is a train in the power supply section where the fault is located; otherwise, it is determined that there is no train in the power supply section where the fault is located. The balance error The calculation method is as follows: ； in, This represents the total number of branches at the T-line branch point, excluding train diversion branches; The first branch point of the T-line connected to the flow Current values ​​of each branch; balance error The range is between 20 and 50A; When there are trains in the power supply zone where the fault occurs, the method to eliminate the impact of train diversion is: utilizing the balance error. The current of the train shunt branch within the power supply section where the fault occurred is verified, specifically: ； in, The current in A is the upstream T-line current of the i#AT station at the end of the power supply zone where the fault occurs; The current of the T-line above i+1#AT is in A.

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