【作者】 杨大晟；

【导师】 张小青；

【作者基本信息】 北京交通大学 ， 高电压与绝缘技术， 2011， 博士

【摘要】 移动基站容易受雷击和雷电电涌过电压的侵害。据统计,大多数雷电电涌是从移动基站的电源线路侵入的,因而移动基站电源系统的雷电防护对于维护站内设施的安全可靠运行具有重要意义。就总体而言,基站电源系统的雷电电涌过电压防护需要采取屏蔽、接地、等电位连接和分流限压等多种措施,在这些措施中,电涌保护器(SPD-surge protective device)的保护功能是至关重要的。由于保护器在雷电电涌过电压下的动作限压过程涉及到颇为复杂的电磁暂态过程,进行理论分析较为困难,目前工程上在进行设计时主要是根据标准规范和经验做法来确定其大致的参数,而在定量化计算与仿真分析方面所取得的研究成果相对较少。为此,本文旨在对用于基站电源系统防护的电涌保护器的保护性能进行分析,以期为移动基站电源系统的雷电电涌过电压防护提供可信的设计依据,从而降低基站的雷害损失。本文以自行搭建的放电管(GDT-gas discharge tube)模型为基础,对雷电电涌过电压下电涌保护器的动作特性和保护水平进行了仿真分析计算,并对现有的单相电源保护器进行了电路结构改进,通过理论分析及仿真证明了改进电路具有更好的综合性能。对以上仿真分析的保护器均组装实物进行冲击试验并将仿真与试验结果对比,验证了仿真的有效性。对两级保护器的级间配合及保护器与被保护设备负载特性配合进行了仿真分析计算,对前后级保护器动作电压高低、连接电缆长度对整体保护效果的影响均进行了讨论。对保护器与不同类型负载、不同长度连接电缆的配合效果首先采用简化电路定性分析,再进行仿真定量计算。为了验证仿真分析的有效性,组装了具体实物并进行了雷电冲击试验,将仿真结果和试验结果进行了对比从而证明了仿真分析的有效性。通过理论分析、计算和试验测量,对8/20μs和10/350μs这两种波形对电涌保护器核心元件压敏电阻(MOV-metal oxide varistor)的冲击作用是否存在等效性给出了相应结论。推荐采用2ms方波作为保护器耐受操作电涌过电压能力的考核波形,进行了压敏电阻在8/20μs和2ms方波下的冲击比较试验,通过试验使理论分析结果得到了验证。采用马尔可夫过程来分析压敏电阻运行中不同状态的转移过程,建立其状态转移图,推导出了压敏电阻运行中的平均失效前时间(MTTF-Mean Time To Failure)的计算公式。以该计算公式为基础,通过建模仿真取得的参数对雷击基站电源线路情况下压敏电阻的可靠性进行了计算,从而得出了不同条件下压敏电阻在运行中的寿命。本文报道的研究结果能够为移动基站等电子信息系统电源线路的雷电防护设计提供参考依据,对其电涌过电压防护具有实用价值。更多还原

【Abstract】 The mobile base stations are subject to lightning strike and lightning overvoltage harm. According to the statistic date, most of lightning surges intrude the mobile base stations through the power supply lines. Therefore, lightning protection is essential for safe and reliable operation of electrical and electronic equipment inside the mobile base stations. As a whole, the measures taken for protecting the power supply system from lightning overvoltage include shielding, grounding, equipotential bonding, shunting current and voltage limitation. However, the protection function of surge protective devices (SPDs) is very important in these measures. A direct theoretical analysis for the lightning surge suppression process of SPDs is difficult to be performed, since this process is concerned with the sophisticated electromagnetic transient mechanism. The standard specifications and experiential methods have been employed to estimate the protective performance of SDS in the engineering design, while fewer achievements have been obtained in quantitative calculation and simulation analysis. With the present situation in view, this paper makes a detailed analysis to the protective performance of SPDs installed on power supply lines of the base stations in order to provide a credible design basis for the lightning overvoltage protection and reduce the equipment loss from lightning strikes.In this paper, the model of gas discharge tube was constructed. Based on the model, the operating condition of SPDs during the limitation of lightning overvoltages was inquired and the associated protective level was determined by means of computer simulation. An improvement was also made for the circuit structure of single-phase power supply SPDs. It was proved from the theoretical analysis and simulating computation that the improved circuit had a better protective performance. Furthermore, the real components were selected to assemble the SPDs and the impulse tests were carried out to measure their response characteristics. The simulated results were compared with the measured ones, which confirmed the validity of the model and the simulation procedure.Simulating computations were made respectively for the interstage coordination between the two stage SPDs and the characteristic coordination between SPDs and load impedances. The influence of two stage breakdown voltages and connecting cable length on the protective effect was investigated. For different types of load impedances, the quanlitative analysis was made for the transient voltage responses by the simplified circuit model and the quantitative simulated results was also given for the voltage protection level at the protected load terminals. The impulse experiment measurement was conducted for checking the validity of simulation method by comparison between simulated and measured results.From theoretical analysis, computation and experimental measurement, a remark was given for the key protective element, namely metal oxide varistor, on its equivalence of the through-current capability between 8/20μs and 10/350μs waveforms. The 2ms square wave was recommended as the test waveform for examining the withstand ability of SPDs under switching overvoltage. The contrast tests on metal oxide varistors under 8/20μs and 2ms square wave was carried out and the theoretical analysis result was verified by the measured ones.In order to analyze the transfer behavior of different operating states of metal oxide varistors, Markov process was employed and its state transfer diagram was drawn, from which the calculation formula of the mean time to failure of metal oxide varistors was derived. Based on this formula, the reliability of metal oxide varistors was calculated on condition that the power lines of base station was struck by lightning, and the operating lifetime of metal oxide varistors was predicted in different conditions.The research results reported in this paper can provide the reference basis for lightning protection design of power supply system of mobile base station and are of practical significance for its transient overvoltage protection。更多还原