500kV变压器中性点加装小电抗的研究

发布时间：2018-05-06 23:04

本文选题：短路电流 + 变压器　；参考：《华南理工大学》2014年硕士论文

【摘要】：近年来随着广东电网装机容量和各级电压网架建设的高速发展，500kV网架结构大大增强，珠江三角洲地区基本形成了双回路内外环网的结构。电网结构的加强满足了广东电网负荷增长和可靠供电的需求，但同时也带来了电网短路容量的问题。由于电网结构加强，500kV变压器采用自耦变压器等原因，部分500kV变电站出现单相短路电流高于三相短路电流的现象，成为限制电网运行和发展的主导因素之一，需控制单相短路电流水平的增长。目前，广东电网主要通过500kV变电站分区供电的方式减小单相短路电流，但分区供电会减低整体电网的运行稳定性和可靠性，提高了电网运行安全风险。本文首先介绍了广东电网的架构特点，指出广东电网负荷集中、网架结构日益庞大，500kV变电站的220kV单相短路电流普遍高于三相短路电流水平，且逐年增大，严重制约电网稳定运行与发展。提出变压器中性点经小电抗器接地的方式能有效降低短路电流，能保障500kV变电站采用联网供电的方式下提高电网运行可靠性，并能促使变压器中性点的工频过电压、操作过电压也大幅下降，从而降低其绝缘水平，降低设备成本。介绍了国内部分省级电网在500kV主变中性点加装小电抗的成功应用案例。本文对变压器加装中性点小电抗的必要性进行分析，计算了广东电网在全接线方式和分区供电方式下的短路电流值，并根据单相和三相短路电流的对比，对广东电网500kV变电站加装小电抗接地的适宜性进行评估和分类，并对各个类别的500kV变电站加装小电抗后的短路电流进行计算。根据对广东现有500kV站的短路电流、送电能力、潮流及N-1分析的结果，并结合远景电网发展分析，广东电网500kV变电站主变中性点需加装小电抗有横沥站、莞城站、鹏城站、宝安站、香山站共5个变电站，且分析出横沥站和香山站主变加装小电抗限制单相短路电流的效果最为明显。本文介绍了500kV站主变中性点加装小电抗的装设模式分为两种，一是站内全部主变均装设，二是部分主变装设。通过计算分析，同时在4台主变装设小电抗对单相短路电流的限制效果要优于仅在部分主变装设小电抗的限制作用。因此，从降低短路电流效果和经济效益方面综合考虑，，建议鹏城站四台主变中性点、宝安站四台主变、莞城站四台主变和香山站三台主变中性点都装设小电抗。接着，论文对横沥站、莞城站、鹏城站、宝安站、香山站5个变电站的采用的小电抗容量进行分析计算，计算不同大小的电抗值能降低的单相、两相和三相短路电流，经过经济和技术方面考虑，推荐横沥站主变装设的小电抗均取15Ω、莞城站小电抗均取15Ω、香山站小电抗均取10Ω、鹏城站小电抗均取10Ω、宝安站小电抗均取10Ω。论文还对500kV主变中性点加装小电抗的方案进行综合分析，预测5个变电站加装推荐值的小电抗后，广东电网的运行方式比安装前得到优化，短路电流明显减小。另外，根据对小电抗装设方案的综合分析及适应性分析结果，拟定了5个500kV变电站加装小电抗的较为理想的时间，其中香山站建议在2010年夏季前安装，横沥站、鹏城站和宝安站建议在2010年底前安装，莞城站建议在2011年夏季前安装。基于对5座500kV变电站不同运行方式的短路电流，分析和计算中性点入地电流和接触电位差和跨步电位差，并选择了变压器中性点与接地串联小电抗器之间不安装隔离开关，只装设接地开关的接线方式。根据设备的绝缘水平和当地的具体条件，选定了66kV电抗器、66kV接地开关、66kV氧化锌避雷器的型号和参数。最后，制定了5座500kV变电站中性点加装小电抗的一次、二次和土建实施方案，进一步论证了加装小电抗的可行性和适宜性。
[Abstract]:In recent years , with the high speed development of Guangdong power grid installed capacity and voltage network frame construction at all levels , 500kV grid structure has been greatly enhanced , the structure of double - loop inner and outer ring network is basically formed in the Pearl River Delta region .

In this paper , the structure characteristics of Guangdong power grid are introduced . It is pointed out that the load concentration of Guangdong power grid , the structure of grid frame is increasingly large , 220 kV single - phase short - circuit current of 500 kV substation is generally higher than that of three - phase short - circuit current , and it can effectively reduce the short - circuit current by year by year .

In this paper , the necessity of the small reactance of the neutral point of the transformer is analyzed , the short - circuit current value of the Guangdong power grid in the whole wiring mode and the divisional power supply mode is calculated . According to the comparison between the single - phase and three - phase short - circuit current , the short - circuit current in the 500 kV substation of Guangdong power grid is evaluated and classified . According to the development analysis of the far - view power grid , the main transformer neutral point of the 500 kV substation in Guangdong power grid needs to be equipped with a small reactance which has 5 substations , and the effect of the main transformer plus small reactance limiting single - phase short - circuit current in the Hengli station and the Xiangshan station is most obvious .

In this paper , the installation mode of small reactance for main transformer neutral point of 500kV substation is divided into two types , one is the installation of all main transformers in the station , two is partial main transformer installation , and the limitation effect of small reactance on single - phase short - circuit current is better than that of only partial main transformer installation . Therefore , it is suggested that four main transformer neutral points in Pengcheng station , four main transformers in Baoan Station , four main transformers in Dongguan City Station and three main transformer neutral points of Xiangshan Station are installed with small reactance .

Then , the paper analyzes the small reactance capacity adopted by Hengli Station , Dongguan City Station , Pengcheng Station , Bao ' an Station and Xiangshan Station , and calculates the single - phase , two - phase and three - phase short - circuit current which can be reduced by the reactance value of different sizes .

In addition , according to the comprehensive analysis of the small reactance installation scheme and the results of the adaptability analysis , five 500 kV substations are proposed to be installed before the end of 2010 , and the Dongguan City Station is recommended to be installed before the summer of 2011 .

Based on the short - circuit current of different operating modes of five 500kV substations , the neutral point - in - ground current and the contact potential difference and the step - step potential difference are analyzed and calculated , and the connection mode of the grounding switch is selected between the transformer neutral point and the grounded series small reactor . The model and parameters of the 66kV reactor , the 66kV grounding switch and the 66kV zinc oxide arrester are selected according to the insulation level of the equipment and the specific conditions on the ground .

In the end , a primary , secondary and civil engineering scheme of 5 500 kV substation neutral point plus small reactance is developed , which further demonstrates the feasibility and suitability of adding small reactance .

【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM41

【参考文献】