A traction power supply system fault calibration method applied to a double-side power supply mode of an electrified railway

Abstract

The application relates to a traction power supply system fault calibration method applied to a double-side power supply mode of an electrified railway, and relates to the technical field of the traction power supply system of the electrified railway. Main steps are as follows: according to the short-circuit fault point position, short-circuit current distribution of different traction substations is divided into multiple short-circuit current distribution modules; the multiple short-circuit current distribution modules are superposed to obtain a power supply system fault mathematical model; traction substation feeder lines, parallel substations and partition substation incoming line breakers are taken as monitoring key nodes, and current and impedance functions are drawn; it is judged whether a fault point is located on the side of traction substation 1 or the side of traction substation 2, on an uplink or downlink of a traction network, on the left side or the right side of a parallel substation; and a transverse connection current ratio curve method is adopted to calculate a fault position. The application utilizes the characteristics that power flow meets the mutual superposition of power flow distribution under the action of independent power supply when double-side power supply double power sources act, and can realize fault calibration of a traction network of a double-side power supply system with a more complex topological structure.

Description

Technical Field

[0001] This invention relates to the field of electrified railway traction power supply system technology, and in particular to a fault identification method for traction power supply systems applied to bilateral power supply modes in electrified railways. Background Technology

[0002] Currently, single-sided power supply is the most common traction power supply method for electrified railways in my country. However, given my country's diverse terrain, the development of electrified railways has led to the construction of some high-standard, challenging mountainous electrified railways. These high-standard, challenging mountainous electrified railways often have high design speeds, reaching 160km / h to 200km / h, steep gradients (limited to 30‰), and a high proportion of tunnels (over 70%). Furthermore, the areas traversed by these lines are sparsely populated, with generally weak power grids, making it difficult to provide effective power support for the traction power supply system. This presents a series of challenges to the traction power supply system. Compared to single-sided power supply, double-sided power supply, by connecting adjacent power supply units, effectively balances the load scale within the power supply section, significantly improving the power supply capacity of the traction power supply system. Therefore, some research institutions have conducted relevant research on double-sided power supply technologies and implemented trial operations in electrified railways.

[0003] However, the bilateral power supply system forms a multi-source power supply network with a more complex topology. The protection and control principles that are closely related to its topology and power flow distribution are also different from those of the single-sided power supply method. Among them, the implementation scheme of the traction network fault calibration function, which is an important component of protection and control, has changed significantly and needs to be analyzed and studied.

[0004] The fault location determination principle of traction networks under single-sided power supply typically utilizes the linear relationship between the traction network impedance within the power supply unit and the distance from the fault point to the traction substation, and the linear one-to-one correspondence between impedance and location. The fault location is determined by linearly extrapolating the traction network impedance value at the time of the fault. However, with the introduction of a second power source in a double-sided power supply system, the system power flow changes from "distribution from a single power source to the end load" to "simultaneous distribution from both power sources to the intermediate load." The relationship between the traction network impedance monitored by a single substation and the fault location is no longer linear. Therefore, it is necessary to move away from the traditional method of fault location determination based solely on the electrical information of the traction substation. A system-wide approach is needed, collecting real-time electrical information from each traction substation, section substation, and parallel substation within the power supply unit. Through high-speed parallel computing based on a network, the fault location determination function for traction networks under double-sided power supply systems can be achieved. Summary of the Invention

[0005] Based on the above problems, the purpose of this invention is to provide a fault calibration method for traction power supply systems under bilateral power supply mode. According to the characteristic that the power flow under the dual power supply mode satisfies the superposition of the power flow distribution under the independent power supply mode, short-circuit current models of individual power supply points at different fault locations are constructed respectively, providing a systematic fault calibration method for traction networks under bilateral power supply mode.

[0006] The technical solution adopted by this invention to achieve its objective is a fault identification method for traction power supply systems in electrified railways with bilateral power supply, comprising the following steps:

[0007] S1. Based on the relative position of the short-circuit fault point and the parallel station, the short-circuit current distribution and the equivalent impedance of the traction network of different traction substations are analyzed, and the short-circuit current distribution of different traction substations is divided into multiple short-circuit current distribution modules.

[0008] S2. Superimpose the multiple short-circuit current distribution modules at the same fault location to obtain a fault mathematical model of the bilateral power supply traction power supply system under different fault conditions.

[0009] S3. Take the traction substation feeder circuit breaker, parallel substation circuit breaker, and section substation incoming circuit breaker as key nodes for electrical parameter monitoring, and plot the graphs of each current and impedance function.

[0010] S4. By measuring the current direction of the section substation through the incoming circuit breaker or bus circuit breaker, determine whether the fault point is located on the traction substation 1 side or traction substation 2 side. At the same time, by combining the current direction measured by the circuit breaker of the parallel substation near the fault location, determine whether the fault point is located on the traction network upstream or downstream. By measuring the current direction of the upstream and downstream circuit breakers at the section substation incoming circuit breaker, determine whether the fault point is located on the left or right side of the parallel substation.

[0011] S5. The fault location is calculated using the cross-current ratio curve method.

[0012] Furthermore, the multiple short-circuit current distribution modules mentioned in step S1 are specifically as follows:

[0013] Module 1: The fault occurs between traction substation 1 and the parallel substation, and the short-circuit current distribution generated by traction substation 1 is as follows;

[0014] Module 2: The fault occurs between traction substation 1 and the parallel substation, and the short-circuit current distribution generated by traction substation 2 is as follows;

[0015] Module 3: The fault occurs between the section substation and the parallel substation, and the distribution of the short-circuit current generated by traction substation 1;

[0016] Module 4: The fault occurs between the section substation and the parallel substation, and the short-circuit current distribution generated by traction substation 2.

[0017] Furthermore, the mathematical model of the fault of the bilateral power supply traction power supply system under different fault conditions obtained in step S2 is specifically as follows: the current flowing through the feeder circuit breaker of the traction substation, the circuit breaker of the parallel substation, and the incoming circuit breaker of the section substation is obtained by superposition calculation.

[0018] Furthermore, after step S5, the fault location is calculated using the impedance ranging method and compared with the fault location calculated using the cross-current ratio curve method in step S5 for verification.

[0019] Furthermore, the impedance ranging method for calculating the fault location specifically involves:

[0020] Introduce the fault point transition resistance variable Zg;

[0021] When the conclusion is that the fault point is located in the upstream or downstream direction between the traction substation and the parallel station, the Thevenin equivalent impedance of the upstream or downstream feeder of the traction substation is calculated by monitoring the upstream or downstream feeder current I1 and voltage U1 of the traction substation as Equation 1: U1 / I1=Zg+x*Zl, where x is the distance from the fault point to the traction substation and Zl is the unit impedance of the traction network.

[0022] At the same time, by monitoring the parallel current I b The sum of the currents of the upstream or downstream incoming circuit breakers in the zone I f , parallel voltage U b The Thevenin equivalent impedance of the parallel circuit is calculated as Equation 2: U b / (I b +I f )=Zg+(Lx)*Zl, where L is the distance between the traction substation and the parallel substation;

[0023] Solve equations 1 and 2 simultaneously, where U1, I1, and U b I b I f All values ​​are measured values. L and Zl are known quantities, while Zg and x are unknown variables. Solving for these two variables, Zg and x, yields the location of the fault point.

[0024] When the fault point is determined to be located in the upstream or downstream direction between the parallel substation and the section substation, the upstream or downstream incoming current I of the section substation is monitored. f and voltage U f The Thevenin equivalent impedance of the partitioned area is calculated as Equation 3: U f / I f =Zg+x1*Zl, where x1 is the distance between the fault point and the partition;

[0025] At the same time, by monitoring the parallel current I bThe sum of the currents of the up or down circuit breakers in the traction substation, I f , parallel voltage U b The Thevenin equivalent impedance of the parallel circuit is calculated as Equation 4: U b / (I b +I f )=Zg+(L1-x1)*Zl, where L1 is the distance between the partition and the parallel section;

[0026] Solve equations 3 and 4 simultaneously, where U f I f U b I b All values ​​are measured values. L1 and Zl are known quantities, while Zg and x1 are unknown variables. Solving for these variables yields two variables, Zg and x1, and the location of the fault point is obtained.

[0027] The beneficial effects of this invention are as follows:

[0028] Based on the characteristic that the power flow under dual power supply in bilateral power supply satisfies the superposition of power flow distribution under independent power supply, this invention constructs short-circuit current models for individual power supply points at different fault locations. By analyzing the characteristics of electrical parameters measured at key nodes such as traction substation feeder circuit breakers, parallel substation circuit breakers, and section substation circuit breakers as a function of fault distance, this invention summarizes fault calibration methods for different sections, forming a systematic fault calibration method for traction networks under bilateral power supply, which can achieve fault calibration for traction networks with more complex topologies in bilateral power supply systems. Attached Figure Description

[0029] Figure 1 The fault occurred between traction substation 1 and the parallel substation, and the short-circuit current distribution generated by traction substation 1 was as follows:

[0030] Figure 2 The fault occurred between traction substation 1 and the parallel substation, and the short-circuit current distribution generated by traction substation 2 was as follows:

[0031] Figure 3 The fault occurred between the section substation and the parallel substation, and the short-circuit current distribution generated by traction substation 1;

[0032] Figure 4 The fault occurred between the section substation and the parallel substation, and the short-circuit current distribution generated by traction substation 2;

[0033] Figure 5 It is the curve showing the variation of the Thevenin equivalent impedance of the feeder of the traction substation on the fault side with the fault distance when the fault occurs.

[0034] Figure 6When a fault occurs, the curve of the cross-connection current ratio as a function of the fault distance is calculated as the ratio of the parallel current and the sum of the parallel current and the difference between the upward and downward currents of the traction substation divided by 2.

[0035] Figure 7 When a fault occurs, the ratio of the current in the partition station to the current in the parallel station plus the current in the partition station is used as the curve of the cross-connection current ratio as a function of the fault distance.

[0036] Figure 8 It is a curve showing the Thevenin equivalent impedance of the feeder in the substation as a function of the fault distance when a fault occurs. Detailed Implementation

[0037] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Figures 1-8 This paper illustrates a specific implementation of the fault identification method for traction power supply systems in electrified railways with bilateral power supply. Taking a double-track railway as an example, it assumes that the short-circuit capacity of the external power supply system of the traction substation is 2000MVA (known system impedance Zx), the capacity of the traction transformer is 31.5MVA (known traction transformer impedance Zb), and the traction transformer impedance percentage is 10.5%. The power supply arm length is 20km, and the unit self-impedance of the double-track traction network is 0.0738+0.3017jΩ / km (denoted as Zl).

[0039] The method of the present invention includes the following steps:

[0040] S1. Based on the relative location of the short-circuit fault point and the parallel substation, the short-circuit current distribution and the equivalent impedance of the traction network of different traction substations are analyzed. The short-circuit current distribution of different traction substations is divided into 4 short-circuit current distribution modules, which are described in detail below. Figures 1-4 :

[0041] Module 1 describes the short-circuit current distribution generated in traction substation 1 when a fault occurs between traction substation 1 and the parallel substation. Assuming the distance from the fault point to traction substation 1 in kilometers is x, then according to... Figure 1 We can derive the short-circuit currents I1_2 = I1*x / 20 and I1_1 = I1 - I1*x / 20. At this time, the traction network impedance of module 1 is Zw1 = x*(20-x)*Zl / 20 and I1 = 27.5*1000 / (Zx+Zb+Zw1).

[0042] Module 2 describes the short-circuit current distribution generated in traction substation 2 when a fault occurs between traction substation 1 and the parallel substation. Assuming the distance from the fault point to traction substation 1 in kilometers is x, then according to... Figure 2We can derive the short-circuit currents I2_1 = I2*1 / 2*(10-x) / 20, I2_b = I2*1 / 2*(10+x) / 20, and I2_2 = I2*1 / 2+I2_b. At this time, the traction network impedance of module 2 is Zw2 = (10-x)*(10+x)*Zl / 20 + 30*Zl / 2, and I2 = 27.5*1000 / (Zx+Zb+Zw2).

[0043] Module 3 describes the short-circuit current distribution generated by traction substation 1 when a fault occurs between the section substation and the parallel substation; assuming the distance between the fault point and the parallel substation is x kilometers, then according to... Figure 3 We can derive the short-circuit currents I1_2 = I1*1 / 2*x / 20, I1_b = I1*1 / 2*(20-x) / 20, and I1_1 = I1*1 / 2 + I1_b. At this time, the traction network impedance of module 3 is Zw3 = x*(20-x)*Zl / 20 + 10*Zl / 2, and I1 = 27.5*1000 / (Zx+Zb+Zw3).

[0044] Module 4 describes the short-circuit current distribution generated by traction substation 2 when a fault occurs between the section substation and the parallel substation. Assuming the distance from the fault point to the parallel substation is x kilometers, then according to... Figure 4 We can derive the short-circuit currents I2_2 = I2*x / 20 and I2_1 = I2 - I2*x / 20. At this time, the traction network impedance of module 4 is Zw4 = (10-x)*(10+x)*Zl / 20+20*Zl / 2, and I2 = 27.5*1000 / (Zx+Zb+Zw4).

[0045] S2. Superimpose the multiple short-circuit current distribution modules at the same fault location to obtain a fault mathematical model of the bilateral power supply traction power supply system under different fault conditions, that is, calculate the current flowing through the feeder circuit breaker of the traction substation, the circuit breaker of the parallel substation, and the incoming circuit breaker of the section substation, specifically:

[0046] When the fault point is located between traction substation 1 and the parallel substation, the current flowing through the down-feeder circuit breaker of traction substation 1 is: IQ1x=I1*x / 20+I2*1 / 2*(10-x) / 20; the current flowing through the up-feeder circuit breaker of traction substation 1 is: IQ1s=I1-I1*x / 20+I2*1 / 2*(10-x) / 20; the current flowing through the circuit breaker of the parallel substation is: Ib=I1*x / 20+I2*1 / 2*(10+x) / 20; the current flowing through the circuit breaker of the section substation is: If=I2*1 / 2; the current flowing through the up-and-down circuit breakers of traction substation 2 is: IQ2s=IQ2x=I2*1 / 2.

[0047] When the fault point is located between the parallel substation and the section substation, the current flowing through the upstream and downstream feeder circuit breakers of traction substation 1 is: IQ1s = IQ1x = I1 * 1 / 2; the current flowing through the parallel substation circuit breaker is: Ib = I1 * 1 / 2 * (10 + x) / 20 + I2 - I2 * x / 20; the current flowing through the section substation upstream circuit breaker is: Ifs = I1 * 1 / 2 * x / 20 + I2 * x / 20; the current flowing through the section substation downstream circuit breaker is: Ifx = I1 * 1 / 2 * x / 20 - I2 + I2 * x / 20; the current flowing through the upstream and downstream circuit breakers of traction substation 2 is: IQ2s = IQ2x = I2 * 1 / 2.

[0048] S3. Using the traction substation feeder circuit breakers, parallel substation circuit breakers, and section substation incoming line circuit breakers as key nodes for electrical parameter monitoring, graphs of various current and impedance functions are plotted to form... Figures 5-8 The graph of the function.

[0049] S4. By measuring the direction of the current flowing between the incoming line circuit breaker or busbar circuit breaker of the substation in step 3, it can be determined whether the fault point is located on the traction substation 1 side or the traction substation 2 side. Simultaneously, by combining the direction of the current flowing between the circuit breakers of the parallel substations near the fault location measured in step 3, it can be determined whether the fault point is located on the traction network's up or down direction. Finally, to determine the relative position of the fault point and the parallel substation, the Thevenin equivalent impedance of the corresponding fault feeder of the traction substation on the fault side can be monitored. The curve of the equivalent impedance changing with the fault distance is shown in the figure below. Figure 5 As shown. According to Figure 5 Preliminary conclusions can be drawn that when the fault point is located between the traction substation and the parallel substation, the equivalent impedance of the traction substation increases linearly with distance; when the fault point is located between the parallel substation and the sectioning substation, the change in the equivalent impedance of the traction substation with respect to the fault distance is not linear. Therefore, a linearly changing interval function can be fitted and solved. When the monitored Thevenin equivalent impedance is less than the theoretical impedance value at 10km, it can be determined that the fault point is located between the traction substation and the parallel substation; otherwise, it is located between the parallel substation and the sectioning substation.

[0050] S5. For fault location, first use the cross-connection current ratio curve (see...) Figure 6 , Figure 7 ) to conduct analysis:

[0051] When the fault point is determined to be located between the traction substation and the parallel substation, the upstream and downstream feeder currents of the traction substation and the current of the parallel substation are monitored using... Figure 6 By analyzing the cross-current ratio curve, the fault location can be calculated based on its linear variation characteristics.

[0052] When the fault point is determined to be located between the parallel substation and the zone substation, the current in the zone substation and the parallel substation is monitored using... Figure 7By analyzing the cross-current ratio curve, the fault location can be calculated based on its linear variation characteristics.

[0053] Then, the fault location is calculated using the impedance ranging method, that is, based on the determined relative location of the fault point, the corresponding method is used. Figure 5 or Figure 8 The fault location is calculated based on the Thevenin equivalent impedance value of the traction substation or section substation. Specifically, the impedance ranging method for calculating the fault location is as follows:

[0054] Introduce the fault point transition resistance variable Zg;

[0055] When the conclusion is that the fault point is located in the upstream or downstream direction between the traction substation and the parallel station, the Thevenin equivalent impedance of the upstream or downstream feeder of the traction substation is calculated by monitoring the upstream or downstream feeder current I1 and voltage U1 of the traction substation as Equation 1: U1 / I1=Zg+x*Zl, where x is the distance from the fault point to the traction substation and Zl is the unit impedance of the traction network.

[0056] At the same time, by monitoring the parallel current I b The sum of the currents of the upstream or downstream incoming circuit breakers in the zone I f , parallel voltage U b The Thevenin equivalent impedance of the parallel circuit is calculated as Equation 2: U b / (I b +I f )=Zg+(Lx)*Zl, where L is the distance between the traction substation and the parallel substation;

[0057] Solve equations 1 and 2 simultaneously, where U1, I1, and U b I b I f All values ​​are measured values. L and Zl are known quantities, while Zg and x are unknown variables. Solving for these two variables, Zg and x, yields the location of the fault point.

[0058] When the fault point is determined to be located in the upstream or downstream direction between the parallel substation and the section substation, the upstream or downstream incoming current I of the section substation is monitored. f and voltage U f The Thevenin equivalent impedance of the partitioned area is calculated as Equation 3: U f / I f =Zg+x1*Zl, where x1 is the distance between the fault point and the partition;

[0059] At the same time, by monitoring the parallel current I b The sum of the currents of the up or down circuit breakers in the traction substation, I f , parallel voltage U b The Thevenin equivalent impedance of the parallel circuit is calculated as Equation 4: Ub / (I b +I f )=Zg+(L1-x1)*Zl, where L1 is the distance between the partition and the parallel section;

[0060] Solve equations 3 and 4 simultaneously, where U f I f U b I b All values ​​are measured values. L1 and Zl are known quantities, while Zg and x1 are unknown variables. Solving for these variables yields Zg and x1, thus determining the location of the fault point.

[0061] The above calculation results are then verified with the fault location results calculated using the cross-current ratio to ensure the accuracy of fault calibration.

[0062] At this point, the fault calibration of the traction power supply system is complete.

Claims

1. A fault identification method for traction power supply systems in electrified railways with bilateral power supply, characterized in that, Includes the following steps: S1. Based on the relative position of the short-circuit fault point and the parallel station, the short-circuit current distribution and the equivalent impedance of the traction network of different traction substations are analyzed, and the short-circuit current distribution of different traction substations is divided into multiple short-circuit current distribution modules. S2. Superimpose the multiple short-circuit current distribution modules at the same fault location to obtain a fault mathematical model of the bilateral power supply traction power supply system under different fault conditions. S3. Take the traction substation feeder circuit breaker, parallel substation circuit breaker, and section substation incoming circuit breaker as key nodes for electrical parameter monitoring, and plot the graphs of each current and impedance function. S4. By measuring the current direction of the section substation through the incoming circuit breaker or bus circuit breaker, determine whether the fault point is located on the traction substation 1 side or traction substation 2 side. At the same time, by combining the current direction measured by the circuit breaker of the parallel substation near the fault location, determine whether the fault point is located on the traction network upstream or downstream. By measuring the current direction of the upstream and downstream circuit breakers at the section substation incoming circuit breaker, determine whether the fault point is located on the left or right side of the parallel substation. S5. The fault location is calculated using the cross-current ratio curve method.

2. The fault identification method for a traction power supply system applied to a bilateral power supply mode in electrified railways according to claim 1, characterized in that, The multiple short-circuit current distribution modules mentioned in step S1 are specifically: Module 1: The fault occurs between traction substation 1 and the parallel substation, and the short-circuit current distribution generated by traction substation 1 is as follows; Module 2: The fault occurs between traction substation 1 and the parallel substation, and the short-circuit current distribution generated by traction substation 2 is as follows; Module 3: The fault occurs between the section substation and the parallel substation, and the distribution of the short-circuit current generated by traction substation 1; Module 4: The fault occurs between the section substation and the parallel substation, and the short-circuit current distribution generated by traction substation 2.

3. The fault identification method for traction power supply system in a bilateral power supply mode for electrified railways according to claim 1, characterized in that, The mathematical model of the fault of the bilateral power supply traction power supply system under different fault conditions obtained in step S2 is specifically: the current flowing through the feeder circuit breaker of the traction substation, the circuit breaker of the parallel substation, and the incoming circuit breaker of the section substation is obtained by superposition calculation.

4. The fault identification method for a traction power supply system applied to a bilateral power supply mode in electrified railways according to claim 1, characterized in that: After step S5, the fault location is calculated using the impedance ranging method and compared with the fault location calculated using the cross-current ratio curve method in step S5 for verification.

5. A fault identification method for a traction power supply system applied to a bilateral power supply mode in electrified railways according to claim 4, characterized in that, The impedance ranging method for calculating the fault location specifically involves: Introduce the fault point transition resistance variable Zg; When the conclusion is that the fault point is located in the upstream or downstream direction between the traction substation and the parallel station, the Thevenin equivalent impedance of the upstream or downstream feeder of the traction substation is calculated by monitoring the upstream or downstream feeder current I1 and voltage U1 of the traction substation as Equation 1: U1 / I1=Zg+x*Zl, where x is the distance from the fault point to the traction substation and Zl is the unit impedance of the traction network. At the same time, by monitoring the parallel current I b The sum of the currents of the upstream or downstream incoming circuit breakers in the zone I f , parallel voltage U b The Thevenin equivalent impedance of the parallel circuit is calculated as Equation 2: U b / (I b +I f )=Zg+(Lx)*Zl, where L is the distance between the traction substation and the parallel substation; By solving equations 1 and 2 simultaneously, we can obtain two variables, Zg and x, and thus determine the location of the fault point. When the fault point is determined to be located in the upstream or downstream direction between the parallel substation and the section substation, the upstream or downstream incoming current I of the section substation is monitored. f and voltage U f The Thevenin equivalent impedance of the partitioned area is calculated as Equation 3: U f / I f =Zg+x1*Zl, where x1 is the distance between the fault point and the partition; At the same time, by monitoring the parallel current I b The sum of the currents of the up or down circuit breakers in the traction substation, I f , parallel voltage U b The Thevenin equivalent impedance of the parallel circuit is calculated as Equation 4: U b / (I b +I f )=Zg+(L1-x1)*Zl, where L1 is the distance between the partition and the parallel section; Solving equations 3 and 4 simultaneously yields two variables, Zg and x1, which leads to the location of the fault.

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