【作者】 李杨；

【导师】 周浩；

【作者基本信息】 浙江大学 ， 高电压与绝缘技术， 2014， 硕士

【摘要】 从2009年第一条特高压单回交流输电线路成功投入运行至今以来,我国在特高压交流输电方面的运行经验越来越丰富。但是,特高压交流系统仍存在部分过电压的相关问题,尤其是针对远距离的特高压交流输电线路。本文主要对特高压交流系统单相接地故障过电压和特快速暂态过电压的相关问题开展研究。对于特高压交流长距离输电线路,单相接地故障过电压不容忽视。本文首先基于系统电源阻抗特性对该过电压的影响规律,提出了综合考虑该过电压的各影响因素后求取该过电压最大值的方法。在此基础之上,对特高压交流长距离输电线路的单相接地故障过电压的限制方法进行了探讨,结果表明采用MOA和高抗联合限制该过电压的措施是一种技术上可行、经济上占优的方法。其次,应用该限制过电压的方法,在保证整条线路沿线过电压不超过限制水平的前提下,对分3-5段的长距离输电线路合理的分段方式进行了研究。结果表明,对于分3-5段的线路,整条线路总长度分别不超过1300km、1400km和1600km时,过电压不会超过限制水平,且单段线路的最大长度分别可达500km、400km和400km。陡波前、高幅值的VFTO会对特高压GIS系统中GIS设备和变压器构成威胁。本文首先通过试验和仿真就架设于GIS出线套管与主变出线套管之间的架空线对入侵特高压变压器的VFTO波前陡度的限制效果进行了研究,探究了该段架空线长度与入侵主变的VFTO波前陡度之间的定量关系。结果表明,10-25m长的架空线能够很好的保护主变纵绝缘：当架空线长度在10m左右时,架空线能够非常明显的削弱到达主变端口的VFTO波前陡度；当架空线长度达到25m时,对于一般的特高压GIS变电站以及发电厂,到达变压器的VFTO波前陡度不会超出限制水平。此外,对比了特高压GIS变电站与特高压发电厂中VFTO特性的差异,可为工程实践提供借鉴。更多还原

【Abstract】 From the time when the first UHVAC single-circuit transmission line was put into operation,China has accumulated a lot of experience in UHVAC transmission system.But,there still exists some problems about overvoltages of UHVAC transmission system,especially for UHVAC long-distance transmission lines.This paper mainly discuss about single-phase grounding overvoltage and very fast transient overvoltage of UHVAC transmission system.With the increasingly rapid growth of power load, the present main network of our country has been unable to cope with the multiplied transmission capacity needs. The establishment of UHV power grid has been the inevitable developing direction of the electric power industry. UHV transmission’s large capacity, rechargeable power, and long distance can cause high power frequency over-voltage, which seriously affecting the reliability of transmission. Therefore, the study of UHV transmission line power frequency over-voltage has significance on the design and construction of UHV transmissions.As to UHVAC long-distance transmission lines,single-phase overvoltage cannot be ignored.Based on the rule of the effect of source’s impdedance on single-phase grounding overvoltage,a method to get the maximum value of the overvoltage is put forward.On this basis,the restriction methods of this overvoltage is studied.Results show that allocation of the compensation capacity of high voltage(HV) shunt reactors and MOA at the same time can limit overvoltage effectively. Besides, with this limitation method,this paper discusses the maximum length of UHVAC lines when the amplitude of this overvoltage does not exceed1.7p.u under different types of line-segment. Results show that as to the lines that are divided into three segments,the maximum length of these lines can reach1300km when the amplitude of this overvoltage does not exceed1.7p.u;the maximum length can reach1400km and1600km respectively when the lines are divided into four segments and five segments. In1000kV GIS substations or power plants, VFTO poses a big threat to the longitudinal insulation of power transformers because of its steep wavefront. Through experiment and simulation,we discussed the effect of the overhead line between the GIS bushing and the transformer on the wavefront steepness of VFTO at the transformer’s port.With the help of ATP-EMTP, we also analyzed the quantitative relation between the length of the overhead line and the steepness of the VFTO at the transformer’s port. The result shows that the overhead line with the length of10-25m could effectively protect the longitudinal insulation of transformers; when the length of the overhead line is about10m,the steepness of VFTO drops dramatically at the transformer’s port; for usual1000kV GIS substations and power plants,when the length is about25m, the steepness of VFTO at the transformer port wouldn’t exceed the restriction level and wouldn’t threat the longitudinal insulation of the transformer.In addition this paper makes a comparison of VFTO characteristics between1000kV GIS substations and plants which can give reference for designing substations and plants.更多还原