Calculation and characteristic analysis on synergistic effect of CF3I gas mixtures

CF_3I is a potential SF_6 alternative gas.In order to study the insulation properties and synergistic effects of CF_3I/N_2 and CF_3I/CO_2 gas mixtures,two-term approximate Boltzmann equations were used to obtain the ionization coefficient α,attachment coefficient η and the critical equivalent electrical field strength(E/N)_(cr).The results show that the(E/N)_(cr)of CF_3I gas at 300 K is 1.2 times that of SF_6 gas,and CF_3I/N_2 and CF_3I/CO_2 gas mixtures both have synergistic effect occurred.The synergistic effect coefficient of CF_3I/CO_2 gas mixture was higher than that of CF_3I/N_2 gas mixture.But the(E/N)_(cr)of CF_3I/N_2 is higher than that of CF_3I/CO_2 under the same conditions.When the content of CF_3I exceeds 20%,the (E/N)_(cr) of CF_3I/N_2 and CF_3I/CO_2 gas mixture increase linearly with the increasing of CF_3I gas content.The breakdown voltage of CF_3I/N_2 gas mixture is also higher than that of CF_3I/CO_2 gas mixture in slightly non-uniform electrical field under power frequency voltage,but the synergistic effect coefficients of the two gas mixtures are basically the same.     

N2环境下绝缘子闪络特性的试验研究

目前广泛应用于气体绝缘领域的SF_6是一种强温室气体,N_2以其取材方便、价格便宜、环境友好、低电压等级下的优良绝缘性能等优点成为新型环保替代气体。文中对N_2环境下的绝缘子闪络特性进行了试验研究,测量了不同条件下的雷电冲击50%闪络电压,结果显示:随着气压的增加,绝缘子闪络电压近似线性增加;随着绝缘子表面粗糙度的上升,闪络电压先下降后上升;随着伞裙数目的增加,绝缘子正极性闪络电压变化不明显,负极性则先下降后上升。文中的实验数据和结论为N_2在气体绝缘中的应用提供了参考。     

Breakdown characteristics of CF_3I/N_2/CO_2 mixture in power frequency and lightning impulse voltages

Trifluoroiodomethane(CF_3I) and its mixtures are believed to be prospective alternatives to sulfur hexafluoride(SF6), which has been included as a greenhouse gas. In this paper, the breakdown properties of a CF_3I/N_2/CO_2 mixture with the volume fraction of CF_3I fixed at 10% are investigated under power frequency and lightning impulse voltages. The experimental result shows that N_2 possesses higher power frequency and negative lightning impulse breakdown voltages than CO_2, but the power frequency and more negative lightning impulse breakdown voltages of the CF_3I/N_2/CO_2 mixture do not increase with the content of N_2. For the purpose of explaining this abnormal phenomenon, the ionization energies and excitation energies of CF_3I,N_2and CO_2 are calculated. The computation results indicate that the ionization energy of CF_3I is lower than the first excitation energy of N_2, but higher than the lowest excitation energy of CO_2,which means that CF_3I molecules are easily ionized by metastable N_2 molecules. The first excitation energy of N_2 is too high, which hinders its application as the buffer gas of CF_3I.     

典型场景TD—LTE站址选择思路及分析

本文以密集城区中的一个典型场景为例,充分利用现网站址资源和保障覆盖等性能的前提下,给出了典型场景下的TD—LTE选址策略,并结合仿真规划软件进行分析以验证该策略的有效性,这为专业设计人员对实际TD—LTE场景化建设提供相应参考与指导。     

c-C_4F_8/N_2混合气体稍不均匀电场下绝缘性能及放电分解产物的试验研究

SF6存在液化温度高和温室效应两大问题,电力行业发展急需新型环保气体。本文对cC_4F_8/N_2混合气体的绝缘性能进行了试验研究,测量了在稍不均匀电场中,不同气压强度以及混合比例条件下的工频交流击穿电压,结果表明,在实验条件范围内,击穿电压随着气压和c-C_4F_8占比的上升而上升;将实验结果与SF6比较发现c-C_4F_8/N_2混合气体具备和SF6相当的绝缘性能。此外,本文还对混合气体击穿后的气体进行了检测,发现了分解产物C_2F_4。本文为今后c-C_4F_8/N_2混合气体在电力行业中的实际应用提供了参考。     

基于电子输运参数的CF_3I及CF_3I-N_2混合气体绝缘性能分析

三氟碘甲烷(CF3I)因其优异的电气和物化性能被认为是最有可能替代六氟化硫(SF_6)的气体之一。采用玻耳兹曼方程计算纯CF3I及CF3I-N2混合气体的电子输运参数,分析这些参数随约化电场强度E/N和CF3I混合比例的变化规律,从微观角度研究CF3I及CF3I-N2混合气体的绝缘性能。结果表明,纯CF3I气体在均匀场中的绝缘强度约为SF_6的1.19倍;且当CF3I所占比例达到70%时,CF3I-N2混合气体能够达到与纯SF_6相当的绝缘性能。此外,CF3I混合气体在电场敏感性方面优于SF_6,但协同效应不如SF_6-N2混合气体显著。     

基于Boltzmann方程的CF_3I混合气体协同效应分析

CF_3I是一种极具潜力的SF_6替代气体,为了研究CF_3I在不同缓冲气体中的绝缘特性和协同效应,通过求解两项近似Boltzmann方程,对不同混合比例CF_3I/N_2和CF_3I/CO_2混合气体的协同效应系数进行了计算分析,并与试验结果进行对比。计算结果表明,300 K时CF_3I的绝缘强度是SF_6气体的1.2倍,CF_3I/N_2和CF_3I/CO_2混合气体都出现了协同效应现象,CF_3I/CO_2混合气体的协同效应系数显著高于CF_3I/N_2混合气体,但CF_3I/N_2混合气体的绝缘强度高于相同条件下的CF_3I/CO_2混合气体。当CF_3I含量超过20%时,CF_3I/N_2及CF_3I/CO_2混合气体的绝缘强度随CF_3I含量变化基本呈线性变化。试验结果显示,CF_3I/N_2混合气体的击穿电压同样高于CF_3I/CO_2混合气体,但两种混合气体的协同效应系数基本相同。     

GSM无线网络分区优化及割接调整策略

本文介绍了GSM无线网络分区优化和割接调整原则、流程和方法,重点结合网络割接对MSC、BSC、LAC分区优化进行了讨论。     

用于气体绝缘输电线路的CF_3I及其混合气体的散热能力分析

由于SF_6气体温室效应严重,因此亟需找到一种能够替代SF_6气体的环保型绝缘气体。利用传统解析法,对不同气压下充有不同体积分数CF_3I气体的CF_3I-N_2及CF_3I-CO_2混合气体绝缘的气体绝缘输电线路(GIL)的导体温度和外壳温度进行了计算,并与同等条件下采用SF_6气体以及含20%体积分数SF_6气体的SF_6/N_2混合气体的情况进行了对比,分析了CF_3I及其混合气体的散热性能。结果表明:同等条件下,CF_3I-N_2混合气体的散热能力优于CF_3I-CO_2混合气体。而含30%~80%体积分数CF_3I气体的混合气体的散热能力也优于已经广泛应用的SF_6及20%SF_6与80%N_2的混合气体,最高可达到纯SF_6气体的1.05倍以及20%SF_6与80%N_2混合气体的1.1倍。综合考虑绝缘特性、散热特性和液化温度等多方面因素,CF_3I气体体积分数为20%~30%的CF_3I/N_2混合气体可以在一定条件下用作GIL中的绝缘介质。