Direct current magnetic bias treatment method and system for stray current

Abstract

The invention discloses a direct-current magnetic bias treatment method and system for stray current, and relates to the technical field of direct-current magnetic bias treatment, and the method comprises the steps: enabling a rail transit line to be equivalent to a resistance circuit according to the circulation characteristics of the stray current, and building a transformer substation direct-current model; collecting direct-current magnetic bias current of each transformer in a transformer substation for supplying power to the rail transit line in real time; when any direct-current magnetic bias current is larger than a preset threshold value, the transformer substation direct-current model is solved, and the difference value between the actual resistance value of the steel rail fastener and a preset resistance value is obtained; and generating a direct current magnetic bias treatment scheme according to the characteristics of the steel rail fastener and the difference value. By adopting the embodiment of the invention, the direct current magnetic bias phenomenon caused by the stray current can be comprehensively and effectively treated, and the safety and the stability of power grid operation are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current (DC) magnetic bias control, and in particular to a DC magnetic bias control method and system for stray current. Background Art

[0002] The reasons for the DC bias in transformers include the single-pole loop operation of UHV DC transmission, geomagnetic storms, subway stray currents, etc. With the rapid development of urban subways and the increase in subway, high-speed rail and other rail lines, the impact of stray currents on power grid transformers is becoming more and more serious.

[0003] During the operation of rail transit, the traction substations on both sides provide power for it, and the steel rails serve as return rails to form the loop of the locomotive power supply system. However, since the steel rails cannot be completely insulated from the ground, part of the traction current will leak into the underground and become stray current, flowing in the soil and metal pipes, and entering the transformer windings, causing DC bias in the transformer, seriously affecting the normal operation of the power grid.

[0004] At present, most of the solutions for the treatment of DC bias in rail transit are proposed around the DC transmission system. There are many differences between stray current and the DC bias current generated by the DC transmission system. The magnitude of stray current varies dynamically with the operation of the train, and the existing treatment solutions and devices are not applicable. Summary of the invention

[0005] The present invention provides a method and system for controlling DC bias magnetic field of stray current. Compared with the traditional DC transmission system control scheme, the embodiment of the present invention can effectively control the DC bias magnetic field phenomenon caused by stray current, thereby improving the safety and stability of power grid operation.

[0006] The embodiment of the present invention provides a DC bias magnetic treatment method for stray current, comprising:

[0007] According to the flow characteristics of stray current, the rail transit line is equivalent to a resistance circuit, and a DC model of the substation is established;

[0008] Real-time collection of DC bias current of each transformer in the substation that supplies power to the rail transit line;

[0009] When any of the DC bias currents is greater than a preset threshold, solving the substation DC model to obtain a difference between an actual resistance value of the rail fastener and a preset resistance value;

[0010] A DC bias magnetic treatment solution is generated based on the characteristics of the rail fastener and the difference.

[0011] As an improvement of the above scheme, according to the flow characteristics of stray current, the rail transit line is equivalent to a resistance circuit, and a substation DC model is established, including:

[0012] Equivalently treat the rail transit line as a resistance circuit to obtain an equivalent circuit;

[0013] According to the traction strategy of the rail transit line, Kirchhoff's law is used to perform current analysis on the equivalent circuit to obtain the stray current change value under different operating conditions of the locomotive;

[0014] Using the stray current variation value as an excitation, obtaining substation data and transformer data during the operation of the locomotive;

[0015] A substation DC model is established according to the equivalent circuit, the substation data and the transformer data.

[0016] As an improvement of the above solution, the rail transit line is equivalent to a resistance circuit to obtain an equivalent circuit, including:

[0017] The rail fasteners of rail transit are divided into three nodes, wherein the first node is the rail, the second node is the iron pad, and the third node is the sleeper block;

[0018] The fastener used to connect the first node and the second node is equivalent to a first fastener transition resistor;

[0019] The fastener used to connect the second node and the third node is equivalent to a second fastener transition resistor;

[0020] Calculating a rail fastener transition resistance of rail transit according to the first fastener transition resistance and the second fastener transition resistance;

[0021] According to the transition resistance of the rail fastener, an equivalent circuit is obtained.

[0022] As an improvement of the above scheme, when any of the DC bias currents is greater than a preset threshold, solving the substation DC model to obtain the difference between the actual resistance value of the rail fastener and the preset resistance value includes:

[0023] When any of the DC bias currents is greater than a preset threshold, solving the substation DC model according to the DC bias current greater than the preset threshold to obtain an actual resistance value of the rail fastener;

[0024] Solving the substation DC model according to a preset DC bias current limit value to obtain a preset resistance value of the rail fastener;

[0025] The difference between the actual resistance value and the preset resistance value of the rail fastener is calculated based on the actual resistance value and the preset resistance value.

[0026] As an improvement of the above scheme, when any of the DC bias currents is greater than a preset threshold, solving the substation DC model according to the DC bias current greater than the preset threshold to obtain the actual resistance value of the rail fastener includes:

[0027] When any of the DC bias currents is greater than a preset threshold, the operating condition of the locomotive is obtained according to the DC bias current;

[0028] Inputting the operating conditions into the substation DC model to solve for a DC excitation source value;

[0029] Obtaining a stray current value according to a preset ratio of the DC excitation source value to the DC bias current limit value;

[0030] According to the stray current value, the actual resistance value of the rail fastener is calculated in the substation DC model.

[0031] As an improvement of the above solution, the DC bias magnetic treatment solution is generated according to the characteristics of the rail fastener and the difference, including:

[0032] According to the characteristics of the rail fastener, a material replacement scheme is obtained;

[0033] According to the difference of the rail fasteners, a proportional adjustment scheme is obtained;

[0034] Generate a first DC bias magnetic treatment plan according to the material replacement plan and the ratio adjustment plan;

[0035] According to the substation DC model, determining whether the first DC bias magnetic treatment solution is feasible;

[0036] If so, the first DC bias magnetization management scheme is used as the DC bias magnetization management scheme; if not, a second DC bias magnetization management scheme is generated, and the second DC bias magnetization management scheme is used as the DC bias magnetization management scheme; wherein the second DC bias magnetization management scheme is the receiving end management scheme.

[0037] As an improvement of the above solution, judging whether the first DC bias magnetic treatment solution is feasible according to the substation DC model includes:

[0038] In the substation DC model, the first DC bias magnetic treatment scheme is adopted to obtain a simulated DC bias magnetic current value after treatment;

[0039] If the simulated DC bias current value is greater than the preset threshold, it is determined that the first DC bias control scheme is not feasible; otherwise, if the simulated DC bias current value is not greater than the preset threshold, it is determined that the first DC bias control scheme is feasible.

[0040] As an improvement of the above scheme, the second DC bias magnetic control scheme is to compensate for the neutral point current of the transformer, install a capacitor isolation device at the neutral point of the transformer, or connect a small resistor in series with the neutral point of the transformer.

[0041] The embodiment of the present invention further provides a DC bias magnetic treatment system for stray current, comprising:

[0042] The model building module is used to establish a DC model of a substation by treating the rail transit line as a resistance circuit according to the flow characteristics of stray current;

[0043] A data acquisition module is used to collect the DC bias current of each transformer in the substation that supplies power to the rail transit line in real time;

[0044] A model solving module, used for solving the substation DC model to obtain the resistance change value of the rail fastener when any of the DC bias currents is greater than a preset threshold value;

[0045] The scheme generating module is used to generate a DC bias magnetic treatment scheme according to the characteristics of the rail fastener and the resistance change value of the rail fastener.

[0046] As an improvement of the above solution, the solution generation module includes:

[0047] A first sub-scheme generating unit, configured to obtain a material replacement scheme according to the characteristics of the rail fastener;

[0048] A second sub-scheme generating unit, configured to obtain a proportional adjustment scheme according to the difference of the rail fasteners;

[0049] A first scheme generating unit, configured to generate a first DC bias magnetic treatment scheme according to the material replacement scheme and the material replacement scheme;

[0050] A feasibility judgment unit, used for judging whether the first DC bias magnetic treatment scheme is feasible according to the DC model of the substation;

[0051] A DC bias magnetization management scheme generating unit is used to use the first DC bias magnetization management scheme as the DC bias magnetization management scheme if yes; if not, generate a second DC bias magnetization management scheme and use the second DC bias magnetization management scheme as the DC bias magnetization management scheme; wherein the second DC bias magnetization management scheme is a receiving end management scheme.

[0052] Compared with the prior art, the present invention discloses a method and system for controlling DC bias magnetism for stray current. According to the flow characteristics of stray current, the rail transit line is equivalent to a resistance circuit to establish a DC model of the substation; the DC bias magnetism current of each transformer in the substation that supplies power to the rail transit line is collected in real time; when any of the DC bias magnetism currents is greater than a preset threshold, the substation DC model is solved to obtain the difference between the actual resistance value of the rail fastener and the preset resistance value; according to the characteristics of the rail fastener and the difference, a DC bias magnetism control plan is generated. The embodiment of the present invention can comprehensively and effectively control the DC bias magnetism phenomenon caused by stray current, and improve the safety and stability of power grid operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a schematic diagram of the steps of a DC bias magnetic treatment method for stray current provided by an embodiment of the present invention;

[0054] Figure 2 1 is a schematic diagram of factors affecting a DC bias current value provided by an embodiment of the present invention;

[0055] Figure 3 is a circuit diagram of an equivalent circuit provided by an embodiment of the present invention;

[0056] Figure 4 is a structural schematic diagram of a rail node provided by an embodiment of the present invention;

[0057] Figure 5 It is a structural schematic diagram of a DC bias magnetic treatment system for stray current provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] In the description of the specification and claims, it is to be understood that the terms first, second, etc. in the specification and claims are only used for the purpose of describing the same technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated, nor necessarily describing the order or time sequence. The terms are interchangeable where appropriate. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0060] The reasons for the DC bias in transformers include the single-pole loop operation of UHV DC transmission, geomagnetic storms, and subway stray currents. With the rapid development of urban subways and the increase in subway lines, the impact of subway stray currents on power grid transformers is becoming more and more serious. During the operation of the subway, the traction substations on both sides supply power to it. The rails serve as return rails to form the circuit of the locomotive power supply system. Since the rails cannot be completely insulated from the ground, part of the traction current will leak into the ground and become stray current, which flows in the soil and metal pipes and enters the transformer windings, causing the transformer to have a DC bias, which seriously affects the normal operation of the power grid.

[0061] At present, the research on subway stray current mainly focuses on the analysis of the impact path and range on transformers, and the DC bias magnetic treatment solutions are mostly proposed around the DC transmission system. There are many differences between stray current and the DC bias magnetic current generated by the DC transmission system. The size of the stray current varies with the dynamic operation of the random train. The stray current leakage point is difficult to evaluate, and the existing treatment solutions and devices are not applicable. At present, relevant research has not proposed an effective treatment plan for the DC bias magnetic treatment of transformers caused by stray current. Many cities have experienced DC bias magnetic treatment of transformers caused by subway stray current, and no targeted treatment has been received, which has seriously affected the normal operation of the power grid.

[0062] Based on the above considerations, an embodiment of the present invention provides a schematic flow chart of the steps of a DC bias magnetic treatment method for stray current. Figure 1 In this embodiment, the DC bias magnetic treatment method for stray current is specifically performed through steps S1 to S4:

[0063] S1. According to the flow characteristics of stray current, the rail transit line is equivalent to a resistance circuit and a DC model of the substation is established.

[0064] It should be noted that the substation DC model can simplify the entire rail transit line composed of the rail transit power supply system, rails and underground structures into an equivalent resistance circuit, which can be used to accurately analyze the flow path and distribution characteristics of stray currents. In addition, the specific parameters of the substation DC model are also related to the transformer, grounding grid, overhead line, relative position of the line and substation, and soil resistivity in rail transit. When constructing the substation DC model, it can be set according to the actual situation.

[0065] S2. Real-time collection of DC bias current of each transformer in the substation that supplies power to the rail transit line.

[0066] It should be noted that there are several transformers in the substation that supplies power to the rail transit line. When collecting DC bias current data, it is necessary to collect data from all transformers. More preferably, after collecting the DC bias current, the DC bias current is sorted according to its value or line distribution.

[0067] S3. When any of the DC bias currents is greater than a preset threshold, the substation DC model is solved to obtain a difference between an actual resistance value of the rail fastener and a preset resistance value.

[0068] It should be noted that, in the present invention, it is found that the factors affecting the DC bias current value of the transformer include traction current, locomotive position, and rail-to-ground transition resistance, among which the rail-to-ground transition resistance has a greater influence weight and is easy to control. Figure 2 As shown in Figure 2, when the rail-to-ground transition resistance increases, the corresponding DC bias current decreases, and vice versa. Figure 2 In the figure, the positive and negative values ​​of the DC bias current indicate the direction of the current.

[0069] It should also be noted that the transition resistance of the rail fastener is an important component of the rail-to-ground transition resistance, so the rail-to-ground transition resistance value can be increased by increasing the transition resistance of the rail fastener. The rail fastener is mainly composed of elastic bars, anchor bolts, flat washers, rail pads, insulating gauge blocks, sleeves, iron pads, iron pads, etc. The rail pads, insulating gauge blocks, sleeves and iron pads are the main insulating components, and the rest are conductive parts. According to the structure of each component of the rail fastener, the equivalent circuit of the rail fastener transition resistance can be obtained, thereby obtaining the equivalent transition resistance value of the rail fastener, and then calculating the rail-to-ground transition resistance value. In an embodiment of the present invention, the difference between the actual resistance value of the rail fastener and the preset resistance value is calculated to reflect the influence of the source-end rail transit line on the DC bias current.

[0070] S4. Generate a DC bias magnetic treatment plan based on the characteristics of the rail fastener and the difference.

[0071] Exemplarily, the equivalent resistance of the rail fastener can be adjusted in the substation DC model according to the characteristics of the rail fastener and the difference, which is reflected in changing the structure or material of the rail fastener in the actual rail transit line.

[0072] A DC bias control method for stray current provided in an embodiment of the present invention can effectively control the DC bias phenomenon caused by stray current from multiple angles at the source end and the receiving end through a substation DC model and analysis of rail fasteners, thereby improving the safety and stability of power grid operation.

[0073] As a preferred implementation, step S1, according to the flow characteristics of stray current, the rail transit line is equivalent to a resistance circuit, and a substation DC model is established, which is specifically performed through steps S11-S14:

[0074] S11. Equivalently treat the rail transit line as a resistance circuit to obtain an equivalent circuit.

[0075] More preferably, step S11 includes:

[0076] The rail fasteners of rail transit are divided into three nodes, wherein the first node is the rail, the second node is the iron pad, and the third node is the sleeper block;

[0077] The fastener used to connect the first node and the second node is equivalent to a first fastener transition resistor;

[0078] The fastener used to connect the second node and the third node is equivalent to a second fastener transition resistor;

[0079] Calculating a rail fastener transition resistance of rail transit according to the first fastener transition resistance and the second fastener transition resistance;

[0080] According to the transition resistance of the rail fastener, an equivalent circuit is obtained.

[0081] For example, see Figure 3 A gauge block and a rail pad are distributed between the first node and the second node, and a high pad and a casing are distributed between the second node and the third node.

[0082] Then, the rail fastener transition resistance is Among them, R1 is the equivalent resistance of the gauge block, R2 is the equivalent resistance of the rail pad, R3 is the equivalent resistance of the high pad, and R4 is the equivalent resistance of the casing. The values ​​of R1, R2, R3, and R4 can be calculated by the conductivity of each material. In the subway track, rail fasteners are generally set every 0.6 to 0.8 meters. By calculating the rail fastener transition resistance of each rail fastener, the rail-to-ground transition resistance in the substation DC model can be obtained.

[0083] S12. According to the traction strategy of the rail transit line, Kirchhoff's law is used to perform current analysis on the equivalent circuit to obtain the stray current change value under different operating conditions of the locomotive.

[0084] S13, using the stray current change value as an excitation to obtain substation data and transformer data during the operation of the locomotive.

[0085] It should be noted that the DC bias current value can be obtained based on the relationship between the substation data and transformer data and the stray current change value. When solving the substation DC model in the subsequent process, the substation data and transformer data during the locomotive operation, as well as the locomotive operating conditions and other data can be obtained by reverse reasoning based on the DC bias current value.

[0086] S14. Establishing a substation DC model according to the equivalent circuit, the substation data and the transformer data.

[0087] See also Figure 4 In the substation DC model, the traction substation is equivalent to a voltage source, R is equivalent to the resistance of the locomotive and the traction substation, and R G is the longitudinal resistance of the rail, R P is the longitudinal resistance of the drainage network, R D is the equivalent resistance of underground structures and metal pipelines, R gp is the transition resistance between the rail and the drainage network, R pd is the transition resistance between the drainage network and the earth, R gp and R pd It can be equivalent to the rail-to-ground transition resistance.

[0088] By using Kirchhoff's law to analyze the current of the equivalent circuit, the distribution formula of the stray current can be obtained:

[0089]

[0090] Among them, i(x) is the rail current, i P (x) is the current of the drainage network at point x, i s (x) is the earth current. In the embodiment of the present invention, in order to simulate the actual subway operation, the fast traction strategy is selected to obtain the change value of the locomotive traction current in one operation cycle, so as to obtain the change value of the stray current under different locomotive operating conditions.

[0091] Furthermore, taking the stray current change value as the excitation, the DC bias current value of the nearby transformer during the locomotive operation can be obtained. The DC bias current value is determined by the following formula:

[0092] I e =(G -1 gV-V)g;

[0093] Among them, V is the ground voltage of the substation, g is the conductance of the substation, and G is the conductance of the transformer.

[0094] As a preferred implementation, in step S3, when any of the DC bias currents is greater than a preset threshold, the substation DC model is solved to obtain the difference between the actual resistance value of the rail fastener and the preset resistance value, which is specifically performed through steps S31-S33:

[0095] S31. When any of the DC bias currents is greater than a preset threshold, the substation DC model is solved according to the DC bias current greater than the preset threshold to obtain an actual resistance value of the rail fastener.

[0096] Further, preferably, step S31 includes:

[0097] When any of the DC bias currents is greater than a preset threshold, the operating condition of the locomotive is obtained according to the DC bias current;

[0098] Inputting the operating conditions into the substation DC model to solve for a DC excitation source value;

[0099] Obtaining a stray current value according to a preset ratio of the DC excitation source value to the DC bias current limit value;

[0100] According to the stray current value, the actual resistance value of the rail fastener is calculated in the substation DC model.

[0101] For example, if the DC bias current of a transformer in a certain substation is measured to be greater than a preset threshold value and there is no DC transmission system nearby, the DC model of the substation is used to analyze the position of the locomotive under dynamic operation and the traction current conditions under which the output DC bias current value is the largest. The DC model of the substation is established by setting the distribution of electrical components and standard values ​​of parameters of the joint model according to the construction standards of the subway line near the substation and the relative position of the subway line and the substation.

[0102] By importing the maximum value of the actually measured excessive DC bias current into the model, the ground potential distribution of the substation can be obtained. According to the ground potential calculation principle, the DC excitation source value I can be obtained. t :

[0103]

[0104] According to the distribution characteristics of stray current, the stray current leakage value is the largest at the micro-element position between the locomotive and the traction substation, and the stray current leaked at this micro-element position is the DC excitation source value I t Take 10% of the stray current value as the stray current value and find the actual resistance value under this stray current value condition.

[0105] S32. Solve the substation DC model according to the preset DC bias current limit value to obtain a preset resistance value of the rail fastener.

[0106] According to the electric power industry standard, the DC bias current limit of a single-phase transformer is 0.3% of the transformer rated current, and the three-phase five-column and three-phase three-column are 0.5% of the transformer rated current. In some embodiments, the preset DC bias current limit is 10A. The value of the DC bias current limit is related to the changes in the single-phase transformer used and the electric power industry standard, and the specific value does not affect the beneficial effects achieved by the present invention.

[0107] S33. Calculate the difference between the actual resistance value and the preset resistance value of the rail fastener according to the actual resistance value and the preset resistance value.

[0108] As a preferred implementation, step S4, generating a DC bias magnetic treatment plan according to the characteristics of the rail fastener and the difference, is specifically performed through steps S41-S45:

[0109] S41. Obtain a material replacement plan based on the characteristics of the rail fastener.

[0110] In some embodiments, the DC bias current can be effectively controlled by replacing the material of the insulating device in the rail fastener with a material with higher insulation properties.

[0111] Exemplarily, the material of the rail bottom plate in the rail fastener is replaced with a material like polytetrafluoroethylene.

[0112] S42. Obtain a proportional adjustment scheme according to the difference of the rail fasteners.

[0113] In the embodiment of the present invention, the rail pad is used as a regulating variable in combination with the characteristics of each insulating device in the rail fastener, and the optimized ratio is obtained by adjusting the proportion of the insulating devices in the rail fastener, thereby generating a ratio adjustment plan.

[0114] S43. Generate a first DC bias magnetic treatment plan according to the material replacement plan and the ratio adjustment plan.

[0115] It should be noted that, in some embodiments, the first DC bias magnetic treatment scheme is only a row material replacement scheme or a ratio adjustment scheme; in other embodiments, the first DC bias magnetic treatment scheme is a combination of a row material replacement scheme and a ratio adjustment scheme.

[0116] It should also be noted that the first DC bias magnetization control solution is a source-end-based control solution, which can fundamentally control the DC bias magnetization phenomenon of the transformer. In areas with dense subway lines, the source-end control solution can more centrally and systematically reduce the impact of stray current on the DC bias magnetization of the transformer, and reduce the impact range of stray current on the grid transformer. The control method based on the receiving end requires the installation of a resistor or capacitor device at the neutral point of the transformer. The current market price of a single unit is about 500,000 yuan; the cost of source-end control is much lower. The cost of changing the transition resistance of the rail fastener is mainly material cost and construction cost, and can be flexibly adjusted according to actual conditions. Compared with the receiving-end control solution, the source-end-based control solution is more stable and has less negative impact on the transformer.

[0117] S44. Determine whether the first DC bias magnetic treatment solution is feasible based on the substation DC model.

[0118] Preferably, step S44 includes:

[0119] In the substation DC model, the first DC bias magnetic treatment scheme is adopted to obtain a simulated DC bias magnetic current value after treatment;

[0120] If the simulated DC bias current value is greater than the preset threshold, it is determined that the first DC bias control scheme is not feasible; otherwise, if the simulated DC bias current value is not greater than the preset threshold, it is determined that the first DC bias control scheme is feasible.

[0121] S45. If yes, then the first DC bias magnetization management scheme is used as the DC bias magnetization management scheme; if not, then a second DC bias magnetization management scheme is generated, and the second DC bias magnetization management scheme is used as the DC bias magnetization management scheme; wherein, the second DC bias magnetization management scheme is the receiving end management scheme.

[0122] Further, preferably, the second DC bias magnetic control scheme is to compensate for the neutral point current of the transformer, install a capacitor isolation device at the neutral point of the transformer, or connect a small resistor in series with the neutral point of the transformer.

[0123] It should be noted that if, after the above-mentioned source-based DC bias control scheme is implemented, the DC bias current value monitored in the subsequent actual operation of the locomotive is still greater than the preset value, measures are taken at the receiving end, i.e. the transformer end, to suppress the DC current flowing into the neutral point of the transformer, thereby achieving targeted control of the transformer DC bias caused by stray current, improving the comprehensiveness of the transformer DC bias control scheme, and improving the stability of the power grid operation.

[0124] When generating the second DC bias control plan, it is also necessary to consider that the current suppression device is proposed based on the DC bias of the transformer caused by the DC transmission system. The injection pole position of the DC transmission system is determined, and the injection point current is clear, while the magnitude and direction of the stray current are changing dynamically. Therefore, it is necessary to estimate the impact range of the stray current based on the density of the subway lines, and take suppression measures in the transformers near the densely populated areas of urban subway lines to suppress the DC current flowing into the transformer and realize the control of the DC bias of the transformer based on the receiving end.

[0125] In the above scheme, firstly, according to the distribution principle of subway system and stray current, combined with the relative position with the substation and its DC model, an evaluation model of DC bias current of transformer caused by subway stray current is established, and the characteristics and size of DC bias current of transformer caused by stray current under different influencing factors are analyzed. According to the analysis results, the variable with a large influence weight of DC bias current of transformer caused by subway stray current is obtained. In the embodiment of the present invention, the variable is a rail fastener, more specifically, an insulating device in the rail fastener. The influence relationship between the variable and the DC bias current is analyzed, and it is observed whether the measured DC bias current value exceeds the standard. If it exceeds the standard, the preset DC bias current value is imported into the model as a governance target, and a source-end governance scheme based on a variable with a large influence weight is proposed. After applying the governance scheme, the preset DC bias current value and the DC bias current value actually measured during subway operation are compared to evaluate the feasibility of the governance scheme. If the DC bias current value measured in the actual operation of the subway does not meet the governance requirements after adding the source-end governance scheme, a governance scheme based on the receiving end is adopted to achieve DC bias governance of transformer caused by subway stray current.

[0126] A DC bias control method for stray current provided in an embodiment of the present invention can effectively control the DC bias phenomenon caused by stray current from multiple angles at the source end and the receiving end through a substation DC model and analysis of rail fasteners, thereby improving the safety and stability of power grid operation.

[0127] See also Figure 2 The embodiment of the present invention provides a DC bias magnetic treatment system for stray current, comprising a model building module 11, a data acquisition module 12, a model solving module 13 and a solution generating module 14, wherein:

[0128] The model building module 11 is used to establish a DC model of a substation by treating the rail transit line as equivalent to a resistance circuit according to the flow characteristics of stray current;

[0129] The data acquisition module 12 is used to collect the DC bias current of each transformer in the substation that supplies power to the rail transit line in real time;

[0130] A model solving module 13, used to solve the substation DC model to obtain the resistance change value of the rail fastener when any of the DC bias currents is greater than a preset threshold;

[0131] The solution generation module 14 is used to generate a DC bias magnetic treatment solution according to the characteristics of the rail fastener and the resistance change value of the rail fastener.

[0132] As a preferred implementation, the model building module 11 includes:

[0133] The resistance circuit equivalent unit is used to convert the rail transit line into a resistance circuit to obtain an equivalent circuit;

[0134] A stray current variation value analysis unit, used to perform current analysis on the equivalent circuit using Kirchhoff's law according to the traction strategy of the rail transit line, and obtain stray current variation values ​​under different operating conditions of the locomotive;

[0135] an excitation unit, used to use the stray current variation value as an excitation to obtain substation data and transformer data during the operation of the locomotive;

[0136] The model building unit is used to build a substation DC model according to the equivalent circuit, the substation data and the transformer data.

[0137] Furthermore, the resistance circuit equivalent unit is specifically used for:

[0138] The rail fasteners of rail transit are divided into three nodes, wherein the first node is the rail, the second node is the iron pad, and the third node is the sleeper block;

[0139] The fastener used to connect the first node and the second node is equivalent to a first fastener transition resistor;

[0140] The fastener used to connect the second node and the third node is equivalent to a second fastener transition resistor;

[0141] Calculating a rail fastener transition resistance of rail transit according to the first fastener transition resistance and the second fastener transition resistance;

[0142] According to the transition resistance of the rail fastener, an equivalent circuit is obtained.

[0143] As a preferred implementation, the model solving module 13 includes:

[0144] An actual resistance value calculation unit, used for solving the substation DC model according to the DC bias current greater than the preset threshold value to obtain the actual resistance value of the rail fastener when any of the DC bias currents is greater than a preset threshold value;

[0145] A preset resistance value calculation unit, used to solve the substation DC model according to a preset DC bias current limit value to obtain a preset resistance value of the rail fastener;

[0146] The difference calculation unit is used to calculate the difference between the actual resistance value and the preset resistance value of the rail fastener according to the actual resistance value and the preset resistance value.

[0147] Further, preferably, the actual resistance value calculation unit is specifically used to:

[0148] When any of the DC bias currents is greater than a preset threshold, the operating condition of the locomotive is obtained according to the DC bias current;

[0149] Inputting the operating conditions into the substation DC model to solve for a DC excitation source value;

[0150] Obtaining a stray current value according to a preset ratio of the DC excitation source value to the DC bias current limit value;

[0151] According to the stray current value, the actual resistance value of the rail fastener is calculated in the substation DC model.

[0152] As a preferred implementation, the solution generation module 14 includes:

[0153] A first sub-scheme generating unit, configured to obtain a material replacement scheme according to the characteristics of the rail fastener;

[0154] A second sub-scheme generating unit, configured to obtain a proportional adjustment scheme according to the difference of the rail fasteners;

[0155] A first scheme generating unit, configured to generate a first DC bias magnetic treatment scheme according to the material replacement scheme and the material replacement scheme;

[0156] A feasibility judgment unit, used for judging whether the first DC bias magnetic treatment scheme is feasible according to the DC model of the substation;

[0157] A DC bias magnetization management scheme generating unit is used to use the first DC bias magnetization management scheme as the DC bias magnetization management scheme if yes; if not, generate a second DC bias magnetization management scheme and use the second DC bias magnetization management scheme as the DC bias magnetization management scheme; wherein the second DC bias magnetization management scheme is a receiving end management scheme.

[0158] Further, preferably, the feasibility determination unit is specifically used to:

[0159] In the substation DC model, the first DC bias magnetic treatment scheme is adopted to obtain a simulated DC bias magnetic current value after treatment;

[0160] If the simulated DC bias current value is greater than the preset threshold, it is determined that the first DC bias control scheme is not feasible; otherwise, if the simulated DC bias current value is not greater than the preset threshold, it is determined that the first DC bias control scheme is feasible.

[0161] In some embodiments, preferably, the second DC bias magnetic control scheme is to compensate for the neutral point current of the transformer, install a capacitor isolation device at the neutral point of the transformer, or connect a small resistor in series with the neutral point of the transformer.

[0162] A DC bias magnetic treatment system for stray current provided by an embodiment of the present invention can effectively treat the DC bias magnetic phenomenon caused by stray current from multiple angles at the source end and the receiving end through a substation DC model and analysis of rail fasteners, thereby improving the safety and stability of power grid operation.

[0163] A person skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0164] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A DC bias magnetic treatment method for stray current, characterized in that: include: According to the flow characteristics of stray current, the rail transit line is equivalent to a resistance circuit, and a DC model of the substation is established; Real-time collection of DC bias current of each transformer in the substation that supplies power to the rail transit line; When any of the DC bias currents is greater than a preset threshold, solving the substation DC model to obtain a difference between an actual resistance value of the rail fastener and a preset resistance value; A DC bias magnetic treatment solution is generated based on the characteristics of the rail fastener and the difference.

2. A DC bias magnetic treatment method for stray current as claimed in claim 1, characterized in that: According to the flow characteristics of stray current, the rail transit line is equivalent to a resistance circuit, and a substation DC model is established, including: Equivalently treat the rail transit line as a resistance circuit to obtain an equivalent circuit; According to the traction strategy of the rail transit line, Kirchhoff's law is used to perform current analysis on the equivalent circuit to obtain the stray current change value under different operating conditions of the locomotive; Using the stray current variation value as an excitation, obtaining substation data and transformer data during the operation of the locomotive; A substation DC model is established according to the equivalent circuit, the substation data and the transformer data.

3. A DC bias magnetic treatment method for stray current as claimed in claim 2, characterized in that: The method of converting the rail transit line into a resistance circuit to obtain an equivalent circuit includes: The rail fasteners of rail transit are divided into three nodes, wherein the first node is the rail, the second node is the iron pad, and the third node is the sleeper block; The fastener used to connect the first node and the second node is equivalent to a first fastener transition resistor; The fastener used to connect the second node and the third node is equivalent to a second fastener transition resistor; Calculating a rail fastener transition resistance of rail transit according to the first fastener transition resistance and the second fastener transition resistance; According to the transition resistance of the rail fastener, an equivalent circuit is obtained.

4. A DC bias magnetic treatment method for stray current as claimed in claim 1, characterized in that: When any of the DC bias currents is greater than a preset threshold, solving the substation DC model to obtain a difference between an actual resistance value of the rail fastener and a preset resistance value includes: When any of the DC bias currents is greater than a preset threshold, solving the substation DC model according to the DC bias current greater than the preset threshold to obtain an actual resistance value of the rail fastener; Solving the substation DC model according to a preset DC bias current limit value to obtain a preset resistance value of the rail fastener; The difference between the actual resistance value and the preset resistance value of the rail fastener is calculated based on the actual resistance value and the preset resistance value.

5. A DC bias magnetic treatment method for stray current as claimed in claim 4, characterized in that: When any of the DC bias currents is greater than a preset threshold, solving the substation DC model according to the DC bias current greater than the preset threshold to obtain an actual resistance value of the rail fastener includes: When any of the DC bias currents is greater than a preset threshold, the operating condition of the locomotive is obtained according to the DC bias current; Inputting the operating conditions into the substation DC model to solve for a DC excitation source value; Obtaining a stray current value according to a preset ratio of the DC excitation source value to the DC bias current limit value; According to the stray current value, the actual resistance value of the rail fastener is calculated in the substation DC model.

6. A DC bias magnetic treatment method for stray current according to claim 1, characterized in that: Generating a DC bias magnetic treatment scheme according to the characteristics of the rail fastener and the difference includes: According to the characteristics of the rail fastener, a material replacement scheme is obtained; According to the difference of the rail fasteners, a proportional adjustment scheme is obtained; Generate a first DC bias magnetic treatment plan according to the material replacement plan and the ratio adjustment plan; According to the substation DC model, determining whether the first DC bias magnetic treatment solution is feasible; If so, the first DC bias magnetization management scheme is used as the DC bias magnetization management scheme; if not, a second DC bias magnetization management scheme is generated, and the second DC bias magnetization management scheme is used as the DC bias magnetization management scheme; wherein the second DC bias magnetization management scheme is the receiving end management scheme.

7. A DC bias magnetic treatment method for stray current as claimed in claim 6, characterized in that: The determining, based on the substation DC model, whether the first DC bias magnetic treatment solution is feasible includes: In the substation DC model, the first DC bias magnetic treatment scheme is adopted to obtain a simulated DC bias magnetic current value after treatment; If the simulated DC bias current value is greater than the preset threshold, it is determined that the first DC bias control scheme is not feasible; otherwise, if the simulated DC bias current value is not greater than the preset threshold, it is determined that the first DC bias control scheme is feasible.

8. A DC bias magnetic treatment method for stray current as claimed in claim 6, characterized in that: The second DC bias magnetic treatment solution is to compensate for the neutral point current of the transformer, install a capacitor isolation device at the neutral point of the transformer, or connect a small resistor in series with the neutral point of the transformer.

9. A DC bias magnetic treatment system for stray current, characterized in that: include: The model building module is used to establish a DC model of a substation by treating the rail transit line as a resistance circuit according to the flow characteristics of stray current; A data acquisition module is used to collect the DC bias current of each transformer in the substation that supplies power to the rail transit line in real time; A model solving module, used for solving the substation DC model to obtain the resistance change value of the rail fastener when any of the DC bias currents is greater than a preset threshold value; The scheme generating module is used to generate a DC bias magnetic treatment scheme according to the characteristics of the rail fastener and the resistance change value of the rail fastener.

10. A DC bias magnetic treatment system for stray current as claimed in claim 9, characterized in that: The solution generation module comprises: A first sub-scheme generating unit, configured to obtain a material replacement scheme according to the characteristics of the rail fastener; A second sub-scheme generating unit, configured to obtain a proportional adjustment scheme according to the difference of the rail fasteners; A first scheme generating unit, configured to generate a first DC bias magnetic treatment scheme according to the material replacement scheme and the material replacement scheme; A feasibility judgment unit, used for judging whether the first DC bias magnetic treatment scheme is feasible according to the DC model of the substation; A DC bias magnetization management scheme generating unit is used to use the first DC bias magnetization management scheme as the DC bias magnetization management scheme if yes; if not, generate a second DC bias magnetization management scheme and use the second DC bias magnetization management scheme as the DC bias magnetization management scheme; wherein the second DC bias magnetization management scheme is a receiving end management scheme.

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