【作者】 何慧雯；

【导师】 何俊佳；

【作者基本信息】 华中科技大学 ， 高电压与绝缘技术， 2007， 硕士

【摘要】 中心城区城市化程度的不断提高和用电负荷的快速增长给城网中、高压线路电缆化带来了广阔的应用前景,也必然导致了电缆出线变电站这种新的变电站出线方式。由于电网中电缆线路比例不断上升,而传统的系统保护和运行方式设计并没有充分考虑这一变化带来的影响,这就有可能对设备的安全运行带来严重的潜在危险和实际的危害。本文从实际的电缆出线变电站系统出发,提取其共同特征,同时充分考虑电缆出线变电站与架空出线变电站的不同,利用ATP电磁暂态程序,建立了一个能够描述该种出线方式变电站基本运行特性的、具有一定广泛代表性的模型系统。对其单相短路故障时的暂态过程进行仿真,并将仿真结果与常规架空出线方式变电站的仿真结果进行对比;并建立缩小模型系统,进行实际测试,验证了所建模型的正确性。由于电缆线路单位长度等效电容值较大,电缆线路电容能存储很大的电场能量,使线路很长时间残存很高的电压,可能对设备和人身安全造成很大威胁。因此有必要对电缆残余电荷对系统操作过电压的影响进行分析,并与架空线路操作过电压进行对比。分析了重合闸操作的可行性。根据发生短路故障时电缆线路与架空线路中的过电流值,分析其对电缆线路和电缆网络中变压器的影响。分析结果表明:对于出线长度均为1km左右的变电站,电缆出线变电站中设备所需绝缘水平与同等条件下架空线出线变电站的要求一样,不需特别设计;对于较长的电缆线路,应考虑容升效应的影响,适当提高绝缘水平。因此,在出线长度较短的电缆网络中出现故障大部分为暂时性故障的前提条件下,重合闸设备的装设能为中压配电网络有效缩小停电面积、保证选择精度,提高供电可靠性提供有力支持。同时,在电缆线路较短的情况下,故障线路和变压器要承受的暂态过电流将比架空线情况下大,如果要采用重合闸装置则应严格校核变压器的动稳定特性。更多还原

【Abstract】 The development of the center city district and the rapid growth of electricity load bring the medium and high voltage urban grids the opportunity to replace overhead lines with cables, so there must be a new substation style with cable outlets. Because the traditional protection and running modes worked with out regard to the larger and larger proportion of cable outlets, then there may be some potential harm to the equipments.The models of substations with cable outlets and overhead line outlets are built respectively to analyze the crest of over-voltage and over-current which take place when a single-phase ground fault has occurred and the three-phase reclosing operation took action. A scale down experiment was made to prove the correctness of the simulation models. Because the equivalent capacitance per kilometer of cable line is large, the trapped electric is dangerous to the equipments and the human. It’s necessary to analyze the relationship between the trapped electric and the over-voltage. And the feasibility of reclosing operation was studied. The relationship between crest of the over-currents in cable and overhead line outlets was analyzed too.Analysis on the models of substations with cable outlets and overhead line outlets shows that over voltages due to reclosing are affected by some factors, such as the magnitude of the trapped charge on the line, the reclosing moment and the number of the outlets. Generally over voltages taking place in cable grid are higher than the over voltages in overhead line grid, however if there are many other outlets in the grid, the over voltage will be depressed much and will be even lower if these outlets are carrying lodes. So the over voltages will not endanger the grid. On the other hand, the over-currents which cable could endure depend on the time for which fault lasts, and the over-currents that transformer in the grid could endure depends on the transformer’s mechanical characteristic. Over currents in cable grid are much higher than in overhead line grid, so the mechanical characteristic of transformer should be checked carefully.更多还原