Method for configuring a surge arrester limiting overvoltage in a power system

Abstract

The application discloses a method for limiting overvoltage of a power system by a deep lightning arrester, and the method comprises the following steps: installing a plurality of groups of lightning arresters on a laying line, wherein the lightning arresters are arranged at the first end and the last end of the laying line and at the middle section of the laying line. The method has the advantages of deep overvoltage reduction potential and significant reduction of the operation overvoltage level in a transformer substation, and has the advantages of simple method and low cost compared with other limiting measures.

Description

Technical Field

[0001] This invention relates to the field of power distribution equipment, and in particular to a method for configuring surge arresters that deeply limit overvoltage in power systems. Background Technology

[0002] Currently, my country's 1000kV AC ultra-high voltage system uses circuit breakers with closing resistors in conjunction with surge arresters at both ends of the line to limit switching overvoltages. This method can limit various types of switching overvoltages to 1.6-1.7 pu. However, this level is still too high for ultra-high voltage electrical equipment, which requires a high level of insulation, resulting in higher costs and manufacturing bottlenecks.

[0003] The mechanism for limiting overvoltage during operation in ultra-high voltage (UHV) systems is to dissipate the energy in the system during switch operation, preventing oscillations from forming high-amplitude overvoltages. Measures include two categories: first, using the closing resistor of the circuit breaker to directly dissipate its energy; and second, improving the performance of surge arresters to limit overvoltages to a lower level.

[0004] To better limit switching overvoltages, researchers have proposed many different limiting methods, including multi-stage closing resistors, controlled closing, and surge arresters along the line. These methods have been proven effective in limiting switching overvoltages in UHV systems, but they do not meet the requirements for deep limiting. Furthermore, these methods all have certain drawbacks. For example, closing resistors in circuit breakers are expensive and prone to damage, while circuit breakers with multi-stage closing resistors are structurally more complex and difficult to manufacture. Therefore, a more effective and simpler method is needed to deeply limit the switching overvoltages of UHV systems.

[0005] Improving the protective performance of surge arresters can effectively meet the above requirements. In current insulation coordination, installing surge arresters at both ends of the line is only an auxiliary means of suppressing switching overvoltages along the line, while the closing resistor in the circuit breaker plays a more important role. Historically, improving the performance of surge arresters and reducing their protection level can significantly reduce the overvoltage level of the system. Furthermore, research has shown that installing surge arresters along the line is a good method for reducing switching overvoltages. Summary of the Invention

[0006] Purpose of the invention: The goal is to obtain a feasible, effective, easy-to-implement, and low-cost overvoltage depth limitation strategy for ultra-high voltage systems.

[0007] The purpose of this invention is to solve the above-mentioned problems by designing a surge arrester configuration method for deeply limiting overvoltage in power systems. The specific design scheme is as follows: A method for configuring surge arresters to deeply limit overvoltage in a power system involves installing multiple sets of surge arresters on a laid line, including surge arresters located at the beginning and end of the laid line and surge arresters located in the middle section of the laid line.

[0008] The number of surge arresters located in the middle section of the laid line is multiple.

[0009] The surge arresters include high charge rate surge arresters, low residual voltage surge arresters, and controllable surge arresters.

[0010] The number of surge arresters in the middle section of the laid line can be three, with the three surge arresters evenly distributed across the laid line, located at 25%, 50%, and 75% of the line length, respectively. According to IEC standards, the rated voltage of surge arresters is determined based on the power frequency overvoltage level of the system. For ultra-high voltage (UHV) systems, if the specified power frequency overvoltage level on the line side is less than 1.4 pu, then the rated voltage of the line-side surge arrester is selected as 1.4 pu (890 kV). If the specified power frequency overvoltage level on the bus side is 1.3 pu, then the rated voltage of the bus-side surge arrester is selected as 1.3 pu (828 kV). After evaluation, my country's 1000 kV UHV system also selected a rated voltage of 828 kV for the line-side surge arrester. This type of surge arrester currently used in my country is referred to as an ordinary surge arrester (OA).

[0011] The characteristics of low residual voltage surge arresters are very similar in the low current region, but in the high current region, low residual voltage surge arresters have significantly better characteristics, namely, lower residual voltage.

[0012] For controllable surge arresters, there are two key parameters: the controllability ratio and the triggering threshold. The controllability ratio α is the ratio U of the rated voltage of the controllable part of the controllable surge arrester to the total rated voltage. r1 / (U r1 +U r2 The overvoltage limiting level increases with increasing α. The trigger threshold US0 is the voltage required for the thyristor of the controllable surge arrester to operate. A smaller US0 results in easier operation of the controllable surge arrester and better overvoltage limiting. However, the actual operating voltage of the controllable surge arrester may exceed the trigger threshold US0 due to the thyristor's operating delay. On the other hand, if US0 is set too low, the controllable surge arrester will operate frequently, affecting the long-term operation of the controllable components.

[0013] The surge arrester configuration method for deeply limiting power system overvoltage obtained through the above technical solution of the present invention has the following advantages: It has the potential to significantly reduce overvoltage and can substantially lower the level of operating overvoltage within substations. Compared to other limiting measures, it also has the advantages of being simple and low-cost. Attached Figure Description

[0014] Figure 1 This is a model diagram of the Huainan-Anhui section of the ultra-high voltage Huainan-Southern Anhui-Northern Zhejiang-West Shanghai line in my country. Figure 2 This is a line-by-line distribution diagram of the overvoltage of the closed line when using different methods. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings.

[0016] Example 1

[0017] The model used is the Huainan-Anhui section of the Huainan-Southern Anhui-Northern Zhejiang-West Shanghai UHVDC transmission line in my country. Its system configuration diagram is shown below. Figure 1 As shown, this is a double-circuit line with a system rated voltage of 1000 kV and a base voltage of 898 kV used for overvoltage calculations. T1–T4 are UHV autotransformers with rated capacities of 1000 / 1000 / 334 MVA, rated voltages of 1050 / 525 / 110 kV, and breaking impedances of 18% / 58% / 42%. Based on this system, the electromagnetic transient calculation program PSCAD / EMTDC can be used to model it and simulate the effects of depth-limited operational overvoltages.

[0018] The effectiveness of installing different surge arresters at both ends of the line (referred to here as Method A) in limiting overvoltage on closed lines was compared with other methods. The comparison method is as follows: Method A—Install different surge arresters at both ends of the line; Method B—The closing resistor is coordinated with the surge arresters at both ends of the line; Method C1—In addition to the surge arresters at both ends of the line, one set of surge arresters is installed along the line; Method C3—Based on the surge arresters at both ends of the line, three sets of surge arresters are arranged along the line.

[0019] In method B, the closing resistor is 600Ω and the connection time is 8ms; in method C1, the surge arrester is installed at 50% of the line length, while in method C3, it is installed at 25%, 50%, and 75% of the line length. The overvoltage distribution along the closed line after using different methods is as follows: Figure 2 As shown in the figure. Except for method A, the surge arresters used in the other limiting methods shown in the figure are all ordinary surge arresters.

[0020] from Figure 2As can be seen, although installing surge arresters at both ends of the line to reduce residual voltage is not the most effective method, it is sufficient considering its simplicity and economy. Combining this method with other voltage limiting techniques can achieve even better results. Furthermore, the overvoltage limiting effect at both ends of the line is the best among the various methods using surge arresters. In contrast, with other methods, the maximum overvoltage may occur at both ends of the line, i.e., in the substation.

[0021] The above analysis shows that surge arresters with reduced residual voltage can serve as an effective means of limiting operational overvoltages in UHV systems, possessing the potential for significant overvoltage reduction and substantially lowering operational overvoltage levels within substations. Compared to other limiting measures, they also offer advantages such as simplicity and lower cost.

[0022] The above technical solutions only embody the preferred technical solutions of the present invention. Any modifications that may be made by those skilled in the art to certain parts thereof embody the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A method for configuring surge arresters to deeply limit overvoltage in a power system, characterized in that, Multiple sets of surge arresters are installed on the laid line, including surge arresters located at the beginning and end of the laid line and surge arresters located in the middle section of the laid line.

2. The method for configuring surge arresters to deeply limit overvoltage in power systems according to claim 1, characterized in that, The number of surge arresters located in the middle section of the laid line is multiple.

3. The method for configuring surge arresters for deep overvoltage limiting in power systems according to claim 1, characterized in that, The surge arresters include high charge rate surge arresters, low residual voltage surge arresters, and controllable surge arresters.

4. The method for configuring surge arresters for deep limiting power system overvoltages as described in claim 1, characterized in that... The number of surge arresters located in the middle section of the laid line is three, and the three surge arresters are equally divided into the laid line, located at 25%, 50%, and 75% of the line length, respectively.

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