Reactive compensation circuit of urban railway power transmission line

Abstract

The utility model provides a city region railway power transmission line reactive compensation circuit, which is connected in parallel in a high-voltage circuit from a power high-voltage line to a load side, and comprises a shunt reactor and a boosting transformer, one end of the shunt reactor is grounded, the other end of the shunt reactor is grounded, and the other end of the shunt reactor is grounded. The other end of the shunt reactor is connected with the low-voltage side of the boosting transformer, and the high-voltage side of the boosting transformer is connected with an electric power high-voltage line. According to the utility model, the shunt reactor is connected to the high-voltage side of the electric power combined station through the boosting transformer to compensate capacitive reactive power caused by a power transmission cable, so that the comprehensive power factor of an electric power circuit can be remarkably improved, huge electric charge caused by the reactive power is avoided, the operation cost is reduced, and the compensating circuit is simple in structure and easy to install and debug.

Description

Technical Field

[0001] This utility model relates to the field of power compensation technology, specifically a reactive power compensation circuit for urban railway transmission lines. Background Technology

[0002] Excessively long transmission lines between the public power grid and the traction substations of rail transit can lead to high capacitance effects on the lines, resulting in a large amount of reactive power being fed back into the lines. This can cause the metering department to incur huge fines due to a low overall power factor, greatly increasing operating costs. Therefore, the problem of low overall power factor in traction substations urgently needs to be addressed.

[0003] Currently, many scholars in China have conducted research on reactive power compensation in railway power supply systems. For example, some have proposed installing MCRs (Mechanical Control Reactors) in traction substations to compensate for capacitive reactive power generated by line no-load operation. Others have proposed a compensation scheme involving installing adjustable reactors at the beginning of through lines and fixed reactors of equal capacity along the entire line. In short, while there is considerable research on reactive power compensation in China, there is relatively little research specifically focused on urban railways.

[0004] In response to the problem of excessively low power factor in the combined traction power stations of urban railways, there is an urgent need for a comprehensive reactive power compensation scheme that meets the operational requirements, thereby avoiding huge electricity bills caused by reactive power and reducing operating costs. Utility Model Content

[0005] The technical problem to be solved by this utility model is to provide a reactive power compensation circuit for urban railway transmission lines, so as to overcome the shortcomings of the prior art described in the background.

[0006] To solve the above-mentioned technical problems, the embodiments of this utility model provide the following technical solution: a reactive power compensation circuit for urban railway transmission lines, wherein the reactive power compensation circuit is connected in parallel in the high-voltage circuit from the high-voltage power line to the load side, the reactive power compensation circuit includes a parallel reactor and a step-up transformer, one end of the parallel reactor is grounded, the other end of the parallel reactor is connected to the low-voltage side of the step-up transformer, and the high-voltage side of the step-up transformer is connected to the high-voltage power line.

[0007] Preferably, the parallel reactor is connected to the low-voltage side of the step-up transformer via a phase selection switch.

[0008] Preferably, a grounding switch is connected in parallel between the phase selection switch and the parallel reactor.

[0009] Preferably, a surge arrester is also connected in parallel between the phase selection switch and the parallel reactor.

[0010] Preferably, the high-voltage side of the step-up transformer is connected to the high-voltage power line via a circuit breaker and a disconnecting switch.

[0011] Preferably, the parallel reactor is a three-phase oil-immersed iron-core reactor, and the step-up transformer is an oil-immersed transformer.

[0012] The beneficial effects of the above-mentioned technical solution of this utility model are as follows:

[0013] This utility model connects a parallel reactor to the high-voltage side of a power substation via a step-up transformer to compensate for the capacitive reactive power caused by the transmission cable. This can significantly improve the overall power factor of the power line, avoid huge electricity bills caused by reactive power, reduce operating costs, and the compensation circuit has a simple structure and is easy to install and debug. Attached Figure Description

[0014] Figure 1 This is an electrical structure diagram illustrating the application scenario of the reactive power compensation circuit control system for urban railway transmission lines according to this utility model.

[0015] Figure 2 This is a schematic diagram of the reactive power compensation circuit for urban railway transmission lines according to this utility model;

[0016] Figure 3 This is a circuit diagram of a specific scheme for reactive power compensation circuit of urban railway transmission lines according to this utility model. Detailed Implementation

[0017] To make the technical problems, technical solutions and advantages of this utility model clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0018] like Figure 3 As shown, this utility model proposes a reactive power compensation circuit for urban railway transmission lines. The reactive power compensation circuit is connected in parallel in the high-voltage circuit from the high-voltage power line to the load side. The reactive power compensation circuit includes a parallel reactor and a step-up transformer. One end of the parallel reactor is grounded, and the other end of the parallel reactor is connected to the low-voltage side of the step-up transformer. The high-voltage side of the step-up transformer is connected to the high-voltage power line.

[0019] The shunt reactor is connected to the low-voltage side of the step-up transformer via a phase-selection switch. A grounding switch and a surge arrester are connected in parallel between the phase-selection switch and the shunt reactor. The high-voltage side of the step-up transformer is connected to the high-voltage power line via a circuit breaker and a disconnecting switch. The shunt reactor is a three-phase oil-immersed iron-core reactor, and the step-up transformer is an oil-immersed transformer.

[0020] The working principle of this utility model is as follows:

[0021] like Figure 2The diagram shown is a schematic of the present invention. When the transmission line between the public power grid and the traction substation of rail transit is too long, the capacitance effect of the line becomes too high, leading to a large amount of reactive power being fed back through the line. Therefore, by using parallel reactance, the equivalent capacitance generated is canceled out, thus achieving reactive power compensation.

[0022] like Figure 3 The diagram shows a specific circuit diagram for the high-voltage side reactive power compensation technology implementation plan. In this embodiment, a 10kV voltage level parallel reactor with a compensation capacity of 7Mvar is added to the high-voltage layer and connected to the 110kV side through a 110kV / 10kV step-up transformer. The parallel reactor is a three-phase oil-immersed iron-core reactor with a capacity of 7Mvar. The oil tank is lined with pebbles and has a storage capacity of approximately 2.5 tons. The tank itself is protected against temperature, oil, and gas; the measurement parameters can be customized. The 110kV / 10kV power transformer is an oil-immersed transformer with a rated capacity of 10MVA. The compensation branch is connected to a disconnecting switch, surge arrester, and phase selection switch for protection. The load side is connected to the MCR (existing system compensation equipment) through a 110kV / 20kV power transformer.

[0023] The following are examples of applications utilizing this utility model:

[0024] During the transmission of power from substation M (110kV output voltage) to the combined substation L, the capacitive reactive power generated should be directly compensated on the 110kV high-voltage side. However, market research revealed that 110kV high-capacity shunt reactors are not advantageous in terms of product technology maturity, current engineering usage, or cost-effectiveness. Meanwhile, shunt reactors below 35kV are already well-established in terms of manufacturing processes and engineering applications. Therefore, it was chosen to add medium-voltage shunt reactors for reactive power compensation. Through on-site testing, simulation analysis, and theoretical calculations, the required compensation capacity was determined to be 7000kvar. After compensation, the shunt reactors can essentially balance the capacitive reactive power generated by 10km of cable.

[0025] Figure 1 This is the electrical structure diagram for the application scenario. The L traction power station has an external power supply voltage level of 110kV, with a 27.5kV traction transformer and a 20kV power transformer connected at the incoming line. The traction transformer adopts a fixed standby mode, with one in operation and one on standby. The traction transformer is connected using a V / V connection method. The power transformer output supplies power to the electrical load. An adjustable magnetically controlled parallel reactor (MCR) is connected to the 20kV side of the power transformer. The L traction power station is connected to the 110kV voltage level power grid via cable.

[0026] Figure 2This utility model provides a circuit diagram for high-voltage side capacitive reactive power compensation. The cable adopts an equivalent circuit, and the 110kV cable is connected to a three-phase compensation reactor for reactive power compensation.

[0027] Figure 3 This is a schematic diagram of the implementation scheme of the high-voltage side reactive power compensation technology of this utility model. At the L traction power combined substation, the 7Mvar reactor compensation device is connected to the 110kV / 10kV step-up transformer, and then connected to the power grid through the cable branch box. This compensation branch is equipped with 110kV and 10kV disconnect switches, surge arresters, and phase selection switches.

[0028] Table 1 shows the changes in power factor at the electricity metering point after reactive power compensation based on measured load data.

[0029] Table 1

[0030] Active power (kW) Reactive power before compensation (kvar) Reactive power after compensation (kvar) Power factor after compensation 824 -6761 266 0.92 4467 -6561 458 0.99 936 -7247 -226 0.99 2765 -7204 -186 0.99 4537 -6564 452 0.99 2820 -7232 -214 0.99

[0031] It can be seen that the fixed reactive power compensation circuit composed of the oil-immersed step-up transformer and reactor of this utility model can compensate for the capacitive reactive power generated by the cable, achieving a comprehensive power factor of 0.9 or higher. Moreover, the compensation circuit structure is simple and easy to install and debug.

[0032] The above description is the preferred embodiment of this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this utility model, and these improvements and modifications should also be considered within the protection scope of this utility model.

Claims

1. A reactive power compensation circuit for a metro railway power line, characterized by, The reactive compensation circuit is connected in parallel in a high-voltage circuit from a power high-voltage line to a load side, and comprises a shunt reactor, a step-up transformer, one end of the shunt reactor being grounded, the other end of the shunt reactor being connected to a low-voltage side of the step-up transformer, and a high-voltage side of the step-up transformer being connected to the power high-voltage line; the shunt reactor and the low-voltage side of the step-up transformer are connected through a phase selection switch; a ground switch is connected in parallel between the phase selection switch and the shunt reactor; a lightning arrester is also connected in parallel between the phase selection switch and the shunt reactor; and the high-voltage side of the step-up transformer is connected to the power high-voltage line through a circuit breaker and an isolating switch.

2. The metropolitan railway power line reactive compensation circuit of claim 1, wherein, The shunt reactor is a three-phase oil-immersed core reactor, and the step-up transformer is an oil-immersed transformer.

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